Selectively-etched nanochannel electrophoretic and electrochemical devices

DOEpatents

Surh, Michael P.; Wilson, William D.; Barbee, Jr., Troy W.; Lane, Stephen M.

2004-11-16

Nanochannel electrophoretic and electrochemical devices having selectively-etched nanolaminates located in the fluid transport channel. The normally flat surfaces of the nanolaminate having exposed conductive (metal) stripes are selectively-etched to form trenches and baffles. The modifications of the prior utilized flat exposed surfaces increase the amount of exposed metal to facilitate electrochemical redox reaction or control the exposure of the metal surfaces to analytes of large size. These etched areas variously increase the sensitivity of electrochemical detection devices to low concentrations of analyte, improve the plug flow characteristic of the channel, and allow additional discrimination of the colloidal particles during cyclic voltammetry.

Selectively-etched nanochannel electrophoretic and electrochemical devices

DOEpatents

Surh, Michael P [Livermore, CA; Wilson, William D [Pleasanton, CA; Barbee, Jr., Troy W.; Lane, Stephen M [Oakland, CA

2006-06-27

Nanochannel electrophoretic and electrochemical devices having selectively-etched nanolaminates located in the fluid transport channel. The normally flat surfaces of the nanolaminate having exposed conductive (metal) stripes are selectively-etched to form trenches and baffles. The modifications of the prior utilized flat exposed surfaces increase the amount of exposed metal to facilitate electrochemical redox reaction or control the exposure of the metal surfaces to analytes of large size. These etched areas variously increase the sensitivity of electrochemical detection devices to low concentrations of analyte, improve the plug flow characteristic of the channel, and allow additional discrimination of the colloidal particles during cyclic voltammetry.

Characterization of the high density plasma etching process of CCTO thin films for the fabrication of very high density capacitors

NASA Astrophysics Data System (ADS)

Altamore, C.; Tringali, C.; Sparta', N.; Di Marco, S.; Grasso, A.; Ravesi, S.

2010-02-01

In this work the feasibility of CCTO (Calcium Copper Titanate) patterning by etching process is demonstrated and fully characterized in a hard to etch materials etcher. CCTO sintered in powder shows a giant relative dielectric constant (105) measured at 1 MHz at room temperature. This feature is furthermore coupled with stability from 101 Hz to 106 Hz in a wide temperature range (100K - 600K). In principle, this property can allow to fabricate very high capacitance density condenser. Due to its perovskite multi-component structure, CCTO can be considered a hard to etch material. For high density capacitor fabrication, CCTO anisotropic etching is requested by using high density plasma. The behavior of etched CCTO was studied in a HRe- (High Density Reflected electron) plasma etcher using Cl2/Ar chemistry. The relationship between the etch rate and the Cl2/Ar ratio was also studied. The effects of RF MHz, KHz Power and pressure variation, the impact of HBr addiction to the Cl2/Ar chemistry on the CCTO etch rate and on its selectivity to Pt and photo resist was investigated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chen; Metzler, Dominik; Oehrlein, Gottlieb S., E-mail: oehrlein@umd.edu

Angstrom-level plasma etching precision is required for semiconductor manufacturing of sub-10 nm critical dimension features. Atomic layer etching (ALE), achieved by a series of self-limited cycles, can precisely control etching depths by limiting the amount of chemical reactant available at the surface. Recently, SiO{sub 2} ALE has been achieved by deposition of a thin (several Angstroms) reactive fluorocarbon (FC) layer on the material surface using controlled FC precursor flow and subsequent low energy Ar{sup +} ion bombardment in a cyclic fashion. Low energy ion bombardment is used to remove the FC layer along with a limited amount of SiO{sub 2} frommore » the surface. In the present article, the authors describe controlled etching of Si{sub 3}N{sub 4} and SiO{sub 2} layers of one to several Angstroms using this cyclic ALE approach. Si{sub 3}N{sub 4} etching and etching selectivity of SiO{sub 2} over Si{sub 3}N{sub 4} were studied and evaluated with regard to the dependence on maximum ion energy, etching step length (ESL), FC surface coverage, and precursor selection. Surface chemistries of Si{sub 3}N{sub 4} were investigated by x-ray photoelectron spectroscopy (XPS) after vacuum transfer at each stage of the ALE process. Since Si{sub 3}N{sub 4} has a lower physical sputtering energy threshold than SiO{sub 2}, Si{sub 3}N{sub 4} physical sputtering can take place after removal of chemical etchant at the end of each cycle for relatively high ion energies. Si{sub 3}N{sub 4} to SiO{sub 2} ALE etching selectivity was observed for these FC depleted conditions. By optimization of the ALE process parameters, e.g., low ion energies, short ESLs, and/or high FC film deposition per cycle, highly selective SiO{sub 2} to Si{sub 3}N{sub 4} etching can be achieved for FC accumulation conditions, where FC can be selectively accumulated on Si{sub 3}N{sub 4} surfaces. This highly selective etching is explained by a lower carbon consumption of Si{sub 3}N{sub 4} as compared to SiO{sub 2}. The comparison of C{sub 4}F{sub 8} and CHF{sub 3} only showed a difference in etching selectivity for FC depleted conditions. For FC accumulation conditions, precursor chemistry has a weak impact on etching selectivity. Surface chemistry analysis shows that surface fluorination and FC reduction take place during a single ALE cycle for FC depleted conditions. A fluorine rich carbon layer was observed on the Si{sub 3}N{sub 4} surface after ALE processes for which FC accumulation takes place. The angle resolved-XPS thickness calculations confirmed the results of the ellipsometry measurements in all cases.« less

Evaluation of the soft x-ray reflectivity of micropore optics using anisotropic wet etching of silicon wafers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitsuishi, Ikuyuki; Ezoe, Yuichiro; Koshiishi, Masaki

2010-02-20

The x-ray reflectivity of an ultralightweight and low-cost x-ray optic using anisotropic wet etching of Si (110) wafers is evaluated at two energies, C K{alpha}0.28 keV and Al K{alpha}1.49 keV. The obtained reflectivities at both energies are not represented by a simple planar mirror model considering surface roughness. Hence, an geometrical occultation effect due to step structures upon the etched mirror surface is taken into account. Then, the reflectivities are represented by the theoretical model. The estimated surface roughness at C K{alpha} ({approx}6 nm rms) is significantly larger than {approx}1 nm at Al K{alpha}. This can be explained by differentmore » coherent lengths at two energies.« less

Evaluation of the soft x-ray reflectivity of micropore optics using anisotropic wet etching of silicon wafers.

PubMed

Mitsuishi, Ikuyuki; Ezoe, Yuichiro; Koshiishi, Masaki; Mita, Makoto; Maeda, Yoshitomo; Yamasaki, Noriko Y; Mitsuda, Kazuhisa; Shirata, Takayuki; Hayashi, Takayuki; Takano, Takayuki; Maeda, Ryutaro

2010-02-20

The x-ray reflectivity of an ultralightweight and low-cost x-ray optic using anisotropic wet etching of Si (110) wafers is evaluated at two energies, C K(alpha)0.28 keV and Al K(alpha)1.49 keV. The obtained reflectivities at both energies are not represented by a simple planar mirror model considering surface roughness. Hence, an geometrical occultation effect due to step structures upon the etched mirror surface is taken into account. Then, the reflectivities are represented by the theoretical model. The estimated surface roughness at C K(alpha) (approximately 6 nm rms) is significantly larger than approximately 1 nm at Al K(alpha). This can be explained by different coherent lengths at two energies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin Yunpeng; Sawin, Herbert H.

The impact of etching kinetics and etching chemistries on surface roughening was investigated by etching thermal silicon dioxide and low-k dielectric coral materials in C{sub 4}F{sub 8}/Ar plasma beams in an inductive coupled plasma beam reactor. The etching kinetics, especially the angular etching yield curves, were measured by changing the plasma pressure and the feed gas composition which influence the effective neutral-to-ion flux ratio during etching. At low neutral-to-ion flux ratios, the angular etching yield curves are sputteringlike, with a peak around 60 deg. -70 deg. off-normal angles; the surface at grazing ion incidence angles becomes roughened due to ionmore » scattering related ion-channeling effects. At high neutral-to-ion flux ratios, ion enhanced etching dominates and surface roughening at grazing angles is mainly caused by the local fluorocarbon deposition induced micromasking mechanism. Interestingly, the etched surfaces at grazing angles remain smooth for both films at intermediate neutral-to-ion flux ratio regime. Furthermore, the oxygen addition broadens the region over which the etching without roughening can be performed.« less

Selective dry etching of III-V nitrides in Cl{sub 2}/Ar, CH{sub 4}/H{sub 2}/Ar, ICi/Ar, and IBr/Ar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vartuli, C.B.; Pearton, S.J.; MacKenzie, J.D.

1996-10-01

The selectivity for etching the binary (GaN, AlN, and InN) and ternary nitrides (InGaN and InAlN) relative to each other in Cl{sub 2}/Ar, CH{sub 4}/H{sub 2}/Ar, ICl/Ar, or IBr/Ar electron cyclotron resonance (ECR) plasmas, and Cl{sub 2}/Ar or CH{sub 4}/H{sub 2}/Ar reactive ion (RIE) plasmas was investigated. Cl-based etches appear to be the best choice for maximizing the selectivity of GaN over the other nitrides. GaN/AlN and GaN/InGaN etch rate ratios of {approximately} 10 were achieved at low RF power in Cl{sub 2}/Ar under ECR and RIE conditions, respectively. GaN/InN selectivity of 10 was found in ICl under ECR conditions.more » A relatively high selectivity (> 6) of InN/GaN was achieved in CH{sub 4}/H{sub 2}/Ar under ECR conditions at low RF powers (50 W). Since the high bond strengths of the nitrides require either high ion energies or densities to achieve practical etch rates it is difficult to achieve high selectivities.« less

Self-terminated etching of GaN with a high selectivity over AlGaN under inductively coupled Cl2/N2/O2 plasma with a low-energy ion bombardment

NASA Astrophysics Data System (ADS)

Zhong, Yaozong; Zhou, Yu; Gao, Hongwei; Dai, Shujun; He, Junlei; Feng, Meixin; Sun, Qian; Zhang, Jijun; Zhao, Yanfei; DingSun, An; Yang, Hui

2017-10-01

Etching of GaN/AlGaN heterostructure by O-containing inductively coupled Cl2/N2 plasma with a low-energy ion bombardment can be self-terminated at the surface of the AlGaN layer. The estimated etching rates of GaN and AlGaN were 42 and 0.6 nm/min, respectively, giving a selective etching ratio of 70:1. To study the mechanism of the etching self-termination, detailed characterization and analyses were carried out, including X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). It was found that in the presence of oxygen, the top surface of the AlGaN layer was converted into a thin film of (Al,Ga)Ox with a high bonding energy, which effectively prevented the underlying atoms from a further etching, resulting in a nearly self-terminated etching. This technique enables a uniform and reproducible fabrication process for enhancement-mode high electron mobility transistors with a p-GaN gate.

Quantum Effect Physics, Electronics and Applications: Proceedings of the International Workshop Held in Luxor, Egypt on January 6-10, 1992

DTIC Science & Technology

1992-12-15

Giza Engineering Systems, Fujitsu, Hitachi, Matsushita, Mitsubishi, NEC, BTT, Sanyo, Sony. and Toshiba. K lsmail T Ikoma H I Smith Organizing and...etch and the i"• development of low etch rate surfaces were used for the fabrication of pyramid - shaped ridges with the QWs forming buried layers...inside the pyramids . "a/s Depending on the etch-depth, the wire /\

Nanofabrication on monocrystalline silicon through friction-induced selective etching of Si3N4 mask

PubMed Central

2014-01-01

A new fabrication method is proposed to produce nanostructures on monocrystalline silicon based on the friction-induced selective etching of its Si3N4 mask. With low-pressure chemical vapor deposition (LPCVD) Si3N4 film as etching mask on Si(100) surface, the fabrication can be realized by nanoscratching on the Si3N4 mask and post-etching in hydrofluoric acid (HF) and potassium hydroxide (KOH) solution in sequence. Scanning Auger nanoprobe analysis indicated that the HF solution could selectively etch the scratched Si3N4 mask and then provide the gap for post-etching of silicon substrate in KOH solution. Experimental results suggested that the fabrication depth increased with the increase of the scratching load or KOH etching period. Because of the excellent masking ability of the Si3N4 film, the maximum fabrication depth of nanostructure on silicon can reach several microns. Compared to the traditional friction-induced selective etching technique, the present method can fabricate structures with lesser damage and deeper depths. Since the proposed method has been demonstrated to be a less destructive and flexible way to fabricate a large-area texture structure, it will provide new opportunities for Si-based nanofabrication. PMID:24940174

Low-k SiOCH Film Etching Process and Its Diagnostics Employing Ar/C5F10O/N2 Plasma

NASA Astrophysics Data System (ADS)

Nagai, Mikio; Hayashi, Takayuki; Hori, Masaru; Okamoto, Hidekazu

2006-09-01

We proposed an environmental harmonic etching gas of C5F10O (CF3CF2CF2OCFCF2), and demonstrated the etching of low-k SiOCH films employing a dual-frequency capacitively coupled etching system. Dissociative ionization cross sections for the electron impact ionizations of C5F10O and c-C4F8 gases have been measured by quadrupole mass spectroscopy (QMS). The dissociative ionization cross section of CF3+ from C5F10O gas was much higher than those of other ionic species, and 10 times higher than that of CF3+ from C4F8 gas. CF3+ is effective for increasing the etching rate of SiO2. As a result, the etching rate of SiOCH films using Ar/C5F10O/N2 plasma was about 1000 nm/min, which is much higher than that using Ar/C4F8/N2 plasma. The behaviours of fluorocarbon radicals in Ar/C5F10O/N2 plasma, which were measured by infrared diode laser absorption spectroscopy, were similar to those in Ar/C4F8/N2 plasma. The densities of CF and CF3 radicals were markedly decreased with increasing N2 flow rate. Etching rate was controlled by N2 flow rate. A vertical profile of SiOCH with a high etching rate and less microloading was realized using Ar/C5F10O/N2 plasma chemistry.

Deep reactive ion etching of 4H-SiC via cyclic SF6/O2 segments

NASA Astrophysics Data System (ADS)

Luna, Lunet E.; Tadjer, Marko J.; Anderson, Travis J.; Imhoff, Eugene A.; Hobart, Karl D.; Kub, Fritz J.

2017-10-01

Cycles of inductively coupled SF6/O2 plasma with low (9%) and high (90%) oxygen content etch segments are used to produce up to 46.6 µm-deep trenches with 5.5 µm-wide openings in single-crystalline 4H-SiC substrates. The low oxygen content segment serves to etch deep in SiC whereas the high oxygen content segment serves to etch SiC at a slower rate, targeting carbon-rich residues on the surface as the combination of carbon-rich and fluorinated residues impact sidewall profile. The cycles work in concert to etch past 30 µm at an etch rate of ~0.26 µm min-1 near room temperature, while maintaining close to vertical sidewalls, high aspect ratio, and high mask selectivity. In addition, power ramps during the low oxygen content segment is used to produce a 1:1 ratio of mask opening to trench bottom width. The effect of process parameters such as cycle time and backside substrate cooling on etch depth and micromasking of the electroplated nickel etch mask are investigated.

Low-damage direct patterning of silicon oxide mask by mechanical processing

PubMed Central

2014-01-01

To realize the nanofabrication of silicon surfaces using atomic force microscopy (AFM), we investigated the etching of mechanically processed oxide masks using potassium hydroxide (KOH) solution. The dependence of the KOH solution etching rate on the load and scanning density of the mechanical pre-processing was evaluated. Particular load ranges were found to increase the etching rate, and the silicon etching rate also increased with removal of the natural oxide layer by diamond tip sliding. In contrast, the local oxide pattern formed (due to mechanochemical reaction of the silicon) by tip sliding at higher load was found to have higher etching resistance than that of unprocessed areas. The profile changes caused by the etching of the mechanically pre-processed areas with the KOH solution were also investigated. First, protuberances were processed by diamond tip sliding at lower and higher stresses than that of the shearing strength. Mechanical processing at low load and scanning density to remove the natural oxide layer was then performed. The KOH solution selectively etched the low load and scanning density processed area first and then etched the unprocessed silicon area. In contrast, the protuberances pre-processed at higher load were hardly etched. The etching resistance of plastic deformed layers was decreased, and their etching rate was increased because of surface damage induced by the pre-processing. These results show that etching depth can be controlled by controlling the etching time through natural oxide layer removal and mechanochemical oxide layer formation. These oxide layer removal and formation processes can be exploited to realize low-damage mask patterns. PMID:24948891

Exploration of suitable dry etch technologies for directed self-assembly

NASA Astrophysics Data System (ADS)

Yamashita, Fumiko; Nishimura, Eiichi; Yatsuda, Koichi; Mochiki, Hiromasa; Bannister, Julie

2012-03-01

Directed self-assembly (DSA) has shown the potential to replace traditional resist patterns and provide a lower cost alternative for sub-20-nm patterns. One of the possible roadblocks for DSA implementation is the ability to etch the polymers to produce quality masks for subsequent etch processes. We have studied the effects of RF frequency and etch chemistry for dry developing DSA patterns. The results of the study showed a capacitively-coupled plasma (CCP) reactor with very high frequency (VHF) had superior pattern development after the block co-polymer (BCP) etch. The VHF CCP demonstrated minimal BCP height loss and line edge roughness (LER)/line width roughness (LWR). The advantage of CCP over ICP is the low dissociation so the etch rate of BCP is maintained low enough for process control. Additionally, the advantage of VHF is the low electron energy with a tight ion energy distribution that enables removal of the polymethyl methacrylate (PMMA) with good selectivity to polystyrene (PS) and minimal LER/LWR. Etch chemistries were evaluated on the VHF CCP to determine ability to treat the BCPs to increase etch resistance and feature resolution. The right combination of RF source frequencies and etch chemistry can help overcome the challenges of using DSA patterns to create good etch results.

Etching of semiconductors and metals by the photonic jet with shaped optical fiber tips

NASA Astrophysics Data System (ADS)

Pierron, Robin; Lecler, Sylvain; Zelgowski, Julien; Pfeiffer, Pierre; Mermet, Frédéric; Fontaine, Joël

2017-10-01

The etching of semiconductors and metals by a photonic jet (PJ) generated with a shaped optical fiber tip is studied. Etched marks with a diameter of 1 μm have been realized on silicon, stainless steel and titanium with a 35 kHz pulsed laser, emitting 100 ns pulses at 1064 nm. The selection criteria of the fiber and its tip are discussed. We show that a 100/140 silica fiber is a good compromise which takes into account the injection, the working distance and the energy coupled in the higher-order modes. The energy balance is performed on the basis of the known ablation threshold of the material. Finally, the dependence between the etching depth and the number of pulses is studied. Saturation is observed probably due to a redeposition of the etched material, showing that a higher pulse energy is required for deeper etchings.

High Aspect Ratio Sub-15 nm Silicon Trenches From Block Copolymer Templates

NASA Astrophysics Data System (ADS)

Gu, Xiaodan; Liu, Zuwei; Gunkel, Ilja; Olynick, Deirdre; Russell, Thomas; University of Massachusetts Amherst Collaboration; Oxford Instrument Collaboration; Lawrence Berkeley National Lab Collaboration

2013-03-01

High-aspect-ratio sub-15 nm silicon trenches are fabricated directly from plasma etching of a block copolymer (BCP) mask. Polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) 40k-b-18k was spin coated and solvent annealed to form cylindrical structures parallel to the silicon substrate. The BCP thin film was reconstructed by immersion in ethanol and then subjected to an oxygen and argon reactive ion etching to fabricate the polymer mask. A low temperature ion coupled plasma with sulfur hexafluoride and oxygen was used to pattern transfer block copolymer structure to silicon with high selectivity (8:1) and fidelity. The silicon pattern was characterized by scanning electron microscopy and grazing incidence x-ray scattering. We also demonstrated fabrication of silicon nano-holes using polystyrene-b-polyethylene oxide (PS-b-PEO) using same methodology described above for PS-b-P2VP. Finally, we show such silicon nano-strucutre serves as excellent nano-imprint master template to pattern various functional materials like poly 3-hexylthiophene (P3HT).

Dry etch challenges for CD shrinkage in memory process

NASA Astrophysics Data System (ADS)

Matsushita, Takaya; Matsumoto, Takanori; Mukai, Hidefumi; Kyoh, Suigen; Hashimoto, Kohji

2015-03-01

Line pattern collapse attracts attention as a new problem of the L&S formation in sub-20nm H.P feature. Line pattern collapse that occurs in a slight non-uniformity of adjacent CD (Critical dimension) space using double patterning process has been studied with focus on micro-loading effect in Si etching. Bias RF pulsing plasma etching process using low duty cycle helped increase of selectivity Si to SiO2. In addition to the effect of Bias RF pulsing process, the thin mask obtained from improvement of selectivity has greatly suppressed micro-loading in Si etching. However it was found that micro-loading effect worsen again in sub-20nm space width. It has been confirmed that by using cycle etch process to remove deposition with CFx based etching micro-loading effect could be suppressed. Finally, Si etching process condition using combination of results above could provide finer line and space without "line pattern collapse" in sub-20nm.

Integration of Electrodeposited Ni-Fe in MEMS with Low-Temperature Deposition and Etch Processes

PubMed Central

Schiavone, Giuseppe; Murray, Jeremy; Perry, Richard; Mount, Andrew R.; Desmulliez, Marc P. Y.; Walton, Anthony J.

2017-01-01

This article presents a set of low-temperature deposition and etching processes for the integration of electrochemically deposited Ni-Fe alloys in complex magnetic microelectromechanical systems, as Ni-Fe is known to suffer from detrimental stress development when subjected to excessive thermal loads. A selective etch process is reported which enables the copper seed layer used for electrodeposition to be removed while preserving the integrity of Ni-Fe. In addition, a low temperature deposition and surface micromachining process is presented in which silicon dioxide and silicon nitride are used, respectively, as sacrificial material and structural dielectric. The sacrificial layer can be patterned and removed by wet buffered oxide etch or vapour HF etching. The reported methods limit the thermal budget and minimise the stress development in Ni-Fe. This combination of techniques represents an advance towards the reliable integration of Ni-Fe components in complex surface micromachined magnetic MEMS. PMID:28772683

Ion-beam-assisted etching of diamond

NASA Technical Reports Server (NTRS)

Efremow, N. N.; Geis, M. W.; Flanders, D. C.; Lincoln, G. A.; Economou, N. P.

1985-01-01

The high thermal conductivity, low RF loss, and inertness of diamond make it useful in traveling wave tubes operating in excess of 500 GHz. Such use requires the controlled etching of type IIA diamond to produce grating like structures tens of micrometers deep. Previous work on reactive ion etching with O2 gave etching rates on the order of 20 nm/min and poor etch selectivity between the masking material (Ni or Cr) and the diamond. An alternative approach which uses a Xe(+) beam and a reactive gas flux of NO2 in an ion-beam-assisted etching system is reported. An etching rate of 200 nm/min was obtained with an etching rate ratio of 20 between the diamond and an aluminum mask.

Suboxide/subnitride formation on Ta masks during magnetic material etching by reactive plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hu; Muraki, Yu; Karahashi, Kazuhiro

2015-07-15

Etching characteristics of tantalum (Ta) masks used in magnetoresistive random-access memory etching processes by carbon monoxide and ammonium (CO/NH{sub 3}) or methanol (CH{sub 3}OH) plasmas have been examined by mass-selected ion beam experiments with in-situ surface analyses. It has been suggested in earlier studies that etching of magnetic materials, i.e., Fe, Ni, Co, and their alloys, by such plasmas is mostly due to physical sputtering and etch selectivity of the process arises from etch resistance (i.e., low-sputtering yield) of the hard mask materials such as Ta. In this study, it is shown that, during Ta etching by energetic CO{sup +}more » or N{sup +} ions, suboxides or subnitrides are formed on the Ta surface, which reduces the apparent sputtering yield of Ta. It is also shown that the sputtering yield of Ta by energetic CO{sup +} or N{sup +} ions has a strong dependence on the angle of ion incidence, which suggests a correlation between the sputtering yield and the oxidation states of Ta in the suboxide or subnitride; the higher the oxidation state of Ta, the lower is the sputtering yield. These data account for the observed etch selectivity by CO/NH{sub 3} and CH{sub 3}OH plasmas.« less

Anisotropic Etching Using Reactive Cluster Beams

NASA Astrophysics Data System (ADS)

Koike, Kunihiko; Yoshino, Yu; Senoo, Takehiko; Seki, Toshio; Ninomiya, Satoshi; Aoki, Takaaki; Matsuo, Jiro

2010-12-01

The characteristics of Si etching using nonionic cluster beams with highly reactive chlorine-trifluoride (ClF3) gas were examined. An etching rate of 40 µm/min or higher was obtained even at room temperature when a ClF3 molecular cluster was formed and irradiated on a single-crystal Si substrate in high vacuum. The etching selectivity of Si with respect to a photoresist and SiO2 was at least 1:1000. We also succeeded in highly anisotropic etching with an aspect ratio of 10 or higher. Moreover, this etching method has a great advantage of low damage, compared with the conventional plasma process.

Fabrication mechanism of friction-induced selective etching on Si(100) surface

PubMed Central

2012-01-01

As a maskless nanofabrication technique, friction-induced selective etching can easily produce nanopatterns on a Si(100) surface. Experimental results indicated that the height of the nanopatterns increased with the KOH etching time, while their width increased with the scratching load. It has also found that a contact pressure of 6.3 GPa is enough to fabricate a mask layer on the Si(100) surface. To understand the mechanism involved, the cross-sectional microstructure of a scratched area was examined, and the mask ability of the tip-disturbed silicon layer was studied. Transmission electron microscope observation and scanning Auger nanoprobe analysis suggested that the scratched area was covered by a thin superficial oxidation layer followed by a thick distorted (amorphous and deformed) layer in the subsurface. After the surface oxidation layer was removed by HF etching, the residual amorphous and deformed silicon layer on the scratched area can still serve as an etching mask in KOH solution. The results may help to develop a low-destructive, low-cost, and flexible nanofabrication technique suitable for machining of micro-mold and prototype fabrication in micro-systems. PMID:22356699

Fabrication mechanism of friction-induced selective etching on Si(100) surface.

PubMed

Guo, Jian; Song, Chenfei; Li, Xiaoying; Yu, Bingjun; Dong, Hanshan; Qian, Linmao; Zhou, Zhongrong

2012-02-23

As a maskless nanofabrication technique, friction-induced selective etching can easily produce nanopatterns on a Si(100) surface. Experimental results indicated that the height of the nanopatterns increased with the KOH etching time, while their width increased with the scratching load. It has also found that a contact pressure of 6.3 GPa is enough to fabricate a mask layer on the Si(100) surface. To understand the mechanism involved, the cross-sectional microstructure of a scratched area was examined, and the mask ability of the tip-disturbed silicon layer was studied. Transmission electron microscope observation and scanning Auger nanoprobe analysis suggested that the scratched area was covered by a thin superficial oxidation layer followed by a thick distorted (amorphous and deformed) layer in the subsurface. After the surface oxidation layer was removed by HF etching, the residual amorphous and deformed silicon layer on the scratched area can still serve as an etching mask in KOH solution. The results may help to develop a low-destructive, low-cost, and flexible nanofabrication technique suitable for machining of micro-mold and prototype fabrication in micro-systems.

The Formation and Characterization of GaN Hexagonal Pyramids

NASA Astrophysics Data System (ADS)

Zhang, Shi-Ying; Xiu, Xiang-Qian; Lin, Zeng-Qin; Hua, Xue-Mei; Xie, Zi-Li; Zhang, Rong; Zheng, You-Dou

2013-05-01

GaN with hexagonal pyramids is fabricated using the photo-assisted electroless chemical etching method. Defective areas of the GaN substrate are selectively etched in a mixed solution of KOH and K2S2O8 under ultraviolet illumination, producing submicron-sized pyramids. Hexagonal pyramids on the etched GaN with well-defined {101¯1¯} facets and very sharp tips are formed. High-resolution x-ray diffraction shows that etched GaN with pyramids has a higher crystal quality, and micro-Raman spectra reveal a tensile stress relaxation in GaN with pyramids compared with normal GaN. The cathodoluminescence intensity of GaN after etching is significantly increased by three times, which is attributed to the reduction in the internal reflection, high-quality GaN with pyramids and the Bragg effect.

Effects of Bias Pulsing on Etching of SiO2 Pattern in Capacitively-Coupled Plasmas for Nano-Scale Patterning of Multi-Level Hard Masks.

PubMed

Kim, Sechan; Choi, Gyuhyun; Chae, Heeyeop; Lee, Nae-Eung

2016-05-01

In order to study the effects of bias pulsing on the etching characteristics of a silicon dioxide (SiO2) layer using multi-level hard mask (MLHM) structures of ArF photoresist/bottom anti-reflected coating/SiO2/amorphous carbon layer (ACL)/SiO2, the effects of bias pulsing conditions on the etch characteristics of a SiO2 layer with an ACL mask pattern in C4F8/CH2F2/O2/Ar etch chemistries were investigated in a dual-frequency capacitively-coupled plasma (CCP) etcher. The effects of the pulse frequency, duty ratio, and pulse-bias power in the 2 MHz low-frequency (LF) power source were investigated in plasmas generated by a 27.12 MHz high-frequency (HF) power source. The etch rates of ACL and SiO2 decreased, but the etch selectivity of SiO2/ACL increased with decreasing duty ratio. When the ACL and SiO2 layers were etched with increasing pulse frequency, no significant change was observed in the etch rates and etch selectivity. With increasing LF pulse-bias power, the etch rate of ACL and SiO2 slightly increased, but the etch selectivity of SiO2/ACL decreased. Also, the precise control of the critical dimension (CD) values with decreasing duty ratio can be explained by the protection of sidewall etching of SiO2 by increased passivation. Pulse-biased etching was successfully applied to the patterning of the nano-scale line and space of SiO2 using an ACL pattern.

SEMICONDUCTOR TECHNOLOGY: TaN wet etch for application in dual-metal-gate integration technology

NASA Astrophysics Data System (ADS)

Yongliang, Li; Qiuxia, Xu

2009-12-01

Wet-etch etchants and the TaN film method for dual-metal-gate integration are investigated. Both HF/HN O3/H2O and NH4OH/H2O2 solutions can etch TaN effectively, but poor selectivity to the gate dielectric for the HF/HNO3/H2O solution due to HF being included in HF/HNO3/H2O, and the fact that TaN is difficult to etch in the NH4OH/H2O2 solution at the first stage due to the thin TaOxNy layer on the TaN surface, mean that they are difficult to individually apply to dual-metal-gate integration. A two-step wet etching strategy using the HF/HNO3/H2O solution first and the NH4OH/H2O2 solution later can fully remove thin TaN film with a photo-resist mask and has high selectivity to the HfSiON dielectric film underneath. High-k dielectric film surfaces are smooth after wet etching of the TaN metal gate and MOSCAPs show well-behaved C-V and Jg-Vg characteristics, which all prove that the wet etching of TaN has little impact on electrical performance and can be applied to dual-metal-gate integration technology for removing the first TaN metal gate in the PMOS region.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donnelly, Vincent M.; Kornblit, Avinoam

The field of plasma etching is reviewed. Plasma etching, a revolutionary extension of the technique of physical sputtering, was introduced to integrated circuit manufacturing as early as the mid 1960s and more widely in the early 1970s, in an effort to reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry. Quickly, the ability to anisotropically etch silicon, aluminum, and silicon dioxide in plasmas became the breakthrough that allowed the features in integrated circuits to continue to shrink over the next 40 years. Some of this early history is reviewed, and a discussionmore » of the evolution in plasma reactor design is included. Some basic principles related to plasma etching such as evaporation rates and Langmuir–Hinshelwood adsorption are introduced. Etching mechanisms of selected materials, silicon, silicon dioxide, and low dielectric-constant materials are discussed in detail. A detailed treatment is presented of applications in current silicon integrated circuit fabrication. Finally, some predictions are offered for future needs and advances in plasma etching for silicon and nonsilicon-based devices.« less

Ga Lithography in Sputtered Niobium for Superconductive Micro and Nanowires.

DOE PAGES

Henry, Michael David; Lewis, Rupert M.; Wolfley, Steven L.; ...

2014-08-18

This work demonstrates the use of FIB implanted Ga as a lithographic mask for plasma etching of Nb films. Using a highly collimated Ga beam of a FIB, Nb is implanted 12 nm deep with a 14 nm thick Ga layer providing etch selectivity better than 15:1 with fluorine based etch chemistry. Implanted square test patterns, both 10 um by and 10 um and 100 um by 100 um, demonstrate that doses above than 7.5 x 1015 cm-2 at 30 kV provide adequate mask protection for a 205 nm thick, sputtered Nb film. The resolution of this dry lithographic techniquemore » is demonstrated by fabrication of nanowires 75 nm wide by 10 um long connected to 50 um wide contact pads. The residual resistance ratio of patterned Nb films was 3. The superconducting transition temperature, Tc =7.7 K, was measured using MPMS. This nanoscale, dry lithographic technique was extended to sputtered TiN and Ta here and could be used on other fluorine etched superconductors such as NbN, NbSi, and NbTi.« less

Study of TLIPSS formation on different metals and alloys and their selective etching

NASA Astrophysics Data System (ADS)

Dostovalov, Alexandr V.; Korolkov, Victor P.; Terentiev, Vadim S.; Okotrub, Konstantin A.; Dultsev, Fedor N.; Nemykin, Anton; Babin, Sergey A.

2017-02-01

Experimental investigation of thermochemical laser-induced periodic surface structures (TLIPSS) formation on metal films (Ti, Cr, Ni, NiCr) at different processing conditions is presented. The hypothesis that the TLIPSS formation depends significantly on parabolic rate constant for oxide thin film growth is discussed. Evidently, low value of this parameter for Ni is the reason of TLIPSS absence on Ni and NiCr film with low Cr content. The effect of simultaneous ablative (with period ≍λ) and thermochemical (with period ≍λ) LIPSS formation was observed. The formation of structures after TLIPSS selective etching was demonstrated.

Physics and chemistry of complex oxide etching and redeposition control

NASA Astrophysics Data System (ADS)

Margot, Joëlle

2012-10-01

Since its introduction in the 1970s, plasma etching has become the universal method for fine-line pattern transfer onto thin films and is anticipated to remain so in foreseeable future. Despite many success stories, plasma etching processes fail to meet the needs for several of the newest materials involved in advanced devices for photonic, electronic and RF applications like ferroelectrics, electro-optic materials, high-k dielectrics, giant magnetoresistance materials and unconventional conductors. In this context, the work achieved over the last decade on the etching of multicomponent oxides thin films such as barium strontium titanate (BST), strontium titanate (STO) and niobate of calcium and barium (CBN) will be reviewed. These materials present a low reactivity with usual etching gases such as fluorinated and chlorinated gases, their etching is mainly governed by ion sputtering and reactive gases sometimes interact with surface materials to form compounds that inhibit etching. The etching of platinum will also be presented as an example of unconventional conductor materials for which severe redeposition limits the achievable etching quality. Finally, it will be shown how simulation can help to understand the etching mechanisms and to define avenues for higher quality patterning.

Thermodynamic approach to the paradox of diamond formation with simultaneous graphite etching in the low pressure synthesis of diamond

NASA Astrophysics Data System (ADS)

Hwang, Nong M.; Yoon, Duk Y.

1996-03-01

In spite of the critical handicap from the thermodynamic point of view, the atomic hydrogen hypothesis is strongly supported by experimental observations of diamond deposition with simultaneous graphite etching. Thermodynamic analysis of the CH system showed that at ˜ 1500 K, carbon solubility in the gas phase is minimal and thus, the equilibrium fraction of solid carbon is maximal. Depending on whether gas phase nucleation takes place or not, the driving force is for deposition or for etching of solid carbon below ˜ 1500 K for the input gas of the typical mixture of 1% CH 499% H 2. The previous observation of etching of the graphite substrate is not expected unless solid carbon precipitated in the gas phase. By rigorous thermodynamic analysis of the previous experimental observations of diamond deposition with simultaneous graphite etching, we suggested that the previous implicit assumption that diamond deposits by an atomic unit should be the weakest point leading to the thermodynamic paradox. The experimental observations could be successfully explained without violating thermodynamics by assuming that the diamond phase had nucleated in the gas phase as fine clusters.

An optimized one-step wet etching process of Pb(Zr0.52Ti0.48)O3 thin films for microelectromechanical system applications

NASA Astrophysics Data System (ADS)

Che, L.; Halvorsen, E.; Chen, X.

2011-10-01

The existence of insoluble residues as intermediate products produced during the wet etching process is the main quality-reducing and structure-patterning issue for lead zirconate titanate (PZT) thin films. A one-step wet etching process using the solutions of buffered HF (BHF) and HNO3 acid was developed for patterning PZT thin films for microelectomechanical system (MEMS) applications. PZT thin films with 1 µm thickness were prepared on the Pt/Ti/SiO2/Si substrate by the sol-gel process for compatibility with Si micromachining. Various compositions of the etchant were investigated and the patterns were examined to optimize the etching process. The optimal result is demonstrated by a high etch rate (3.3 µm min-1) and low undercutting (1.1: 1). The patterned PZT thin film exhibits a remnant polarization of 24 µC cm-2, a coercive field of 53 kV cm-1, a leakage current density of 4.7 × 10-8 A cm-2 at 320 kV cm-1 and a dielectric constant of 1100 at 1 KHz.

Morphology-Driven Control of Metabolite Selectivity Using Nanostructure-Initiator Mass Spectrometry

DOE PAGES

Gao, Jian; Louie, Katherine B.; Steinke, Philipp; ...

2017-05-26

Nanostructure-initiator mass spectrometry (NIMS) is a laser desorption/ionization analysis technique based on the vaporization of a nanostructure-trapped liquid "initiator" phase. Here we report an intriguing relationship between NIMS surface morphology and analyte selectivity. Scanning electron microscopy and spectroscopic ellipsometry were used to characterize the surface morphologies of a series of NIMS substrates generated by anodic electrochemical etching. Mass spectrometry imaging was applied to compare NIMS sensitivity of these various surfaces toward the analysis of diverse analytes. The porosity of NIMS surfaces was found to increase linearly with etching time where the pore size ranged from 4 to 12 nm withmore » corresponding porosities estimated to be 7-70%. Surface morphology was found to significantly and selectively alter NIMS sensitivity. The small molecule ( < 2k Da) sensitivity was found to increase with increased porosity, whereas low porosity had the highest sensitivity for the largest molecules examined. Estimation of molecular sizes showed that this transition occurs when the pore size is < 3× the maximum of molecular dimensions. While the origins of selectivity are unclear, increased signal from small molecules with increased surface area is consistent with a surface area restructuring-driven desorption/ionization process where signal intensity increases with porosity. In contrast, large molecules show highest signal for the low-porosity and small-pore-size surfaces. We attribute this to strong interactions between the initiator-coated pore structures and large molecules that hinder desorption/ionization by trapping large molecules. This finding may enable us to design NIMS surfaces with increased specificity to molecules of interest.« less

Cl 2-based dry etching of the AlGaInN system in inductively coupled plasmas

NASA Astrophysics Data System (ADS)

Cho, Hyun; Vartuli, C. B.; Abernathy, C. R.; Donovan, S. M.; Pearton, S. J.; Shul, R. J.; Han, J.

1998-12-01

Cl 2-Based inductively coupled plasmas with low additional d.c. self-biases (-100 V) produce convenient etch rates (500-1500 Å·min -1) for GaN, AlN, InN, InAlN and InGaN. A systematic study of the effects of additive gas (Ar, N 2, H 2), discharge composition and ICP source power and chuck power on etch rate and surface morphology has been performed. The general trends are to go through a maximum in etch rate with percent Cl 2 in the discharge for all three mixtures and to have an increase (decrease) in etch rate with source power (pressure). Since the etching is strongly ion-assisted, anisotropic pattern transfer is readily achieved. Maximum etch selectivities of approximately 6 for InN over the other nitrides were obtained.

Temperature-Dependent Nanofabrication on Silicon by Friction-Induced Selective Etching.

PubMed

Jin, Chenning; Yu, Bingjun; Xiao, Chen; Chen, Lei; Qian, Linmao

2016-12-01

Friction-induced selective etching provides a convenient and practical way for fabricating protrusive nanostructures. A further understanding of this method is very important for establishing a controllable nanofabrication process. In this study, the effect of etching temperature on the formation of protrusive hillocks and surface properties of the etched silicon surface was investigated. It is found that the height of the hillock produced by selective etching increases with the etching temperature before the collapse of the hillock. The temperature-dependent selective etching rate can be fitted well by the Arrhenius equation. The etching at higher temperature can cause rougher silicon surface with a little lower elastic modulus and hardness. The contact angle of the etched silicon surface decreases with the etching temperature. It is also noted that no obvious contamination can be detected on silicon surface after etching at different temperatures. As a result, the optimized condition for the selective etching was addressed. The present study provides a new insight into the control and application of friction-induced selective nanofabrication.

Molecular dynamics simulations of plasma-surface interactions

NASA Astrophysics Data System (ADS)

Vegh, Joseph James

Molecular dynamics (MD) simulations are carried out to examine the fundamental mechanisms of plasma-surface interactions for various systems of interest to the semiconductor industry. These include ion and radical bombardment simulations of silicon, model low-k dielectric materials, and hydrocarbon (HC) based model photoresist materials. Simulations of fluorocarbon (FC), fluorine, and argon ion etching of silicon are conducted to find conditions under which the steady state etch of Si in the presence of a FC surface layer occurs. By varying the FC/F/Ar + ratios over a range of conditions, a correlation between FC layer thickness and Si etch yield (EY) is obtained that agrees qualitatively with experimentally observed trends. Further examination of this system allows for a Si etch mechanism to be proposed. This mechanism is similar to that seen in previous Si etching simulations where FC films do not form. The FC layer is observed to fluctuate in thickness during steady state Si etch, as the result of competition between FC deposition and sputtering of relatively large (> 6 C atoms) FC clusters during Ar+ impacts. This cluster ejection process is seen in all of the systems studied, and the properties of these clusters (composition, size, kinetic energy, etc.) are examined and catalogued. Ar+ and H radical and ion bombardment of a methylated Si surface is simulated as a model of plasma etching of low-k dielectric materials. The mechanisms and product distributions observed for 300 K H radical bombardment agree well with experiment. The etch characteristics of Ar+ bombardment are examined as a function of ion energy, and the corresponding variations in surface structure at high ion fluence are characterized. Various HC polymer surfaces are studied under ion and radical bombardment to examine plasma species interactions with model photoresist materials. Simulations of 100 eV Ar+ bombardment of polystyrene (PS), poly(4-methylstyrene) (P4MS), and poly(alpha-methylstyrene) (PalphaMS) show that for all of these materials (which have similar chemical compositions: PS: (C8H 8)x, PalphaMS and P4MS: (C9H 10)x), a densely crosslinked, dehydrogenated damaged layer forms at high ion fluences that greatly reduces the sputter yield of the material. During the initial transient period of bombardment, PalphaMS shows sputter yields nearly twice as high as P4MS or PS; polymer structure can play a role during the early stages of etch. Both the initial and high fluence etch characteristics match those observed experimentally. Further, fluctuations from cell-to-cell are much higher for the PalphaMS simulations, which may correlate to the increased roughening observed experimentally for PalphaMS. Additional simulations are carried out to examine the effects of H and F radical addition during Ar+ bombardment of PS. Both radical species are shown to inhibit and/or reverse the formation of the dehydrogenated layer that forms during bombardment with Ar+ alone. Further studies examine the effect of inert ion mass through simulations of Ar +, Xe+, and He+ bombardment of PS, amorphous C, and nanoscale features on diamond surfaces. The differences in penetration depth, kinetic energy deposition, and scattering patterns are suggestive of the differing etch characteristics that are seen experimentally for these ions. A discussion of dangling bond formation during ion bombardment and longer time-scale dynamics is also offered. A brief review of currently available potential energy functions is presented. Selected results from MD simulations that utilize some of these potentials and are closely related to the work in this dissertation are also discussed. The difficulties of expanding potential energy functions vis-a-vis commonly used ab initio quantum chemical calculations are also addressed.

Atomic precision etch using a low-electron temperature plasma

NASA Astrophysics Data System (ADS)

Dorf, L.; Wang, J.-C.; Rauf, S.; Zhang, Y.; Agarwal, A.; Kenney, J.; Ramaswamy, K.; Collins, K.

2016-03-01

Sub-nm precision is increasingly being required of many critical plasma etching processes in the semiconductor industry. Accurate control over ion energy and ion/radical composition is needed during plasma processing to meet these stringent requirements. Described in this work is a new plasma etch system which has been designed with the requirements of atomic precision plasma processing in mind. In this system, an electron sheet beam parallel to the substrate surface produces a plasma with an order of magnitude lower electron temperature Te (~ 0.3 eV) and ion energy Ei (< 3 eV without applied bias) compared to conventional radio-frequency (RF) plasma technologies. Electron beam plasmas are characterized by higher ion-to-radical fraction compared to RF plasmas, so a separate radical source is used to provide accurate control over relative ion and radical concentrations. Another important element in this plasma system is low frequency RF bias capability which allows control of ion energy in the 2-50 eV range. Presented in this work are the results of etching of a variety of materials and structures performed in this system. In addition to high selectivity and low controllable etch rate, an important requirement of atomic precision etch processes is no (or minimal) damage to the remaining material surface. It has traditionally not been possible to avoid damage in RF plasma processing systems, even during atomic layer etch. The experiments for Si etch in Cl2 based plasmas in the aforementioned etch system show that damage can be minimized if the ion energy is kept below 10 eV. Layer-by-layer etch of Si is also demonstrated in this etch system using electrical and gas pulsing.

Innovations in bonding to zirconia-based materials: Part I.

PubMed

Aboushelib, Moustafa N; Matinlinna, Jukka P; Salameh, Ziad; Ounsi, Hani

2008-09-01

Establishing a reliable bond to zirconia-based materials has proven to be difficult which is the major limitation against fabricating adhesive zirconia restorations. This bond could be improved using novel selective infiltration etching conditioning in combination with engineered zirconia primers. Aim of the work was to evaluate resin-to-zirconia bond strength using selective infiltration etching and novel silane-based zirconia primers. Zirconia discs (Procera Zirconia) received selective infiltration etching surface treatment followed by coating with either of five especially engineered experimental zirconia primers. Pre-aged resin-composite discs (Tetric Ivo Ceram) were bonded to the treated surface using an MDP-containing resin-composite (Panavia F 2.0). The bilayered specimens were cut into microbars and the microtensile bond strength (MTBS) was evaluated. 'As-sintered' zirconia discs served as a control (alpha=0.05). The broken microbars were examined using a scanning electron microscope (SEM). The combination of selective infiltration etching with experimental zirconia primers significantly improved (F=3805, P<0.0001) the MTBS values (41+/-5.8 MPa) compared to the 'as-sintered' surface using the same primers which demonstrated spontaneous failure and very low bond strength values (2.6+/-3.1 MPa). SEM analysis revealed that selective infiltration etching surface treatment resulted in a nano-retentive surface where the zirconia primers were able to penetrate and interlock which explained the higher MTBS values observed for the treated specimens.

Electrical transport and low-frequency noise in chemical vapor deposited single-layer MoS2 devices.

PubMed

Sharma, Deepak; Amani, Matin; Motayed, Abhishek; Shah, Pankaj B; Birdwell, A Glen; Najmaei, Sina; Ajayan, Pulickel M; Lou, Jun; Dubey, Madan; Li, Qiliang; Davydov, Albert V

2014-04-18

We have studied temperature-dependent (77-300 K) electrical characteristics and low-frequency noise (LFN) in chemical vapor deposited (CVD) single-layer molybdenum disulfide (MoS2) based back-gated field-effect transistors (FETs). Electrical characterization and LFN measurements were conducted on MoS2 FETs with Al2O3 top-surface passivation. We also studied the effect of top-surface passivation etching on the electrical characteristics of the device. Significant decrease in channel current and transconductance was observed in these devices after the Al2O3 passivation etching. For passivated devices, the two-terminal resistance variation with temperature showed a good fit to the activation energy model, whereas for the etched devices the trend indicated a hopping transport mechanism. A significant increase in the normalized drain current noise power spectral density (PSD) was observed after the etching of the top passivation layer. The observed channel current noise was explained using a standard unified model incorporating carrier number fluctuation and correlated surface mobility fluctuation mechanisms. Detailed analysis of the gate-referred noise voltage PSD indicated the presence of different trapping states in passivated devices when compared to the etched devices. Etched devices showed weak temperature dependence of the channel current noise, whereas passivated devices exhibited near-linear temperature dependence.

Dry etching technologies for reflective multilayer

NASA Astrophysics Data System (ADS)

Iino, Yoshinori; Karyu, Makoto; Ita, Hirotsugu; Kase, Yoshihisa; Yoshimori, Tomoaki; Muto, Makoto; Nonaka, Mikio; Iwami, Munenori

2012-11-01

We have developed a highly integrated methodology for patterning Extreme Ultraviolet (EUV) mask, which has been highlighted for the lithography technique at the 14nm half-pitch generation and beyond. The EUV mask is characterized as a reflective-type mask which is completely different compared with conventional transparent-type of photo mask. And it requires not only patterning of absorber layer without damaging the underlying multi reflective layers (40 Si/Mo layers) but also etching multi reflective layers. In this case, the dry etch process has generally faced technical challenges such as the difficulties in CD control, etch damage to quartz substrate and low selectivity to the mask resist. Shibaura Mechatronics ARESTM mask etch system and its optimized etch process has already achieved the maximal etch performance at patterning two-layered absorber. And in this study, our process technologies of multi reflective layers will be evaluated by means of optimal combination of process gases and our optimized plasma produced by certain source power and bias power. When our ARES™ is used for multilayer etching, the user can choose to etch the absorber layer at the same time or etch only the multilayer.

Demonstration of hetero-gate-dielectric tunneling field-effect transistors (HG TFETs).

PubMed

Choi, Woo Young; Lee, Hyun Kook

2016-01-01

The steady scaling-down of semiconductor device for improving performance has been the most important issue among researchers. Recently, as low-power consumption becomes one of the most important requirements, there have been many researches about novel devices for low-power consumption. Though scaling supply voltage is the most effective way for low-power consumption, performance degradation is occurred for metal-oxide-semiconductor field-effect transistors (MOSFETs) when supply voltage is reduced because subthreshold swing (SS) of MOSFETs cannot be lower than 60 mV/dec. Thus, in this thesis, hetero-gate-dielectric tunneling field-effect transistors (HG TFETs) are investigated as one of the most promising alternatives to MOSFETs. By replacing source-side gate insulator with a high- k material, HG TFETs show higher on-current, suppressed ambipolar current and lower SS than conventional TFETs. Device design optimization through simulation was performed and fabrication based on simulation demonstrated that performance of HG TFETs were better than that of conventional TFETs. Especially, enlargement of gate insulator thickness while etching gate insulator at the source side was improved by introducing HF vapor etch process. In addition, the proposed HG TFETs showed higher performance than our previous results by changing structure of sidewall spacer by high- k etching process.

Dry etched SiO2 Mask for HgCdTe Etching Process

NASA Astrophysics Data System (ADS)

Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

2016-09-01

A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

Spectral artefacts post sputter-etching and how to cope with them - A case study of XPS on nitride-based coatings using monoatomic and cluster ion beams

NASA Astrophysics Data System (ADS)

Lewin, Erik; Counsell, Jonathan; Patscheider, Jörg

2018-06-01

The issue of artefacts due to sputter-etching has been investigated for a group of AlN-based thin film materials with varying thermodynamical stability. Stability of the materials was controlled by alloying AlN with the group 14 elements Si, Ge or Sn in two different concentrations. The coatings were sputter-etched with monoatomic Ar+ with energies between 0.2 and 4.0 keV to study the sensitivity of the materials for sputter damage. The use of Arn+ clusters to remove an oxidised surface layer was also evaluated for a selected sample. The spectra were compared to pristine spectra obtained after in-vacuo sample transfer from the synthesis chamber to the analysis instrument. It was found that the all samples were affected by high energy (4 keV) Ar+ ions to varying degrees. The determining factors for the amount of observed damage were found to be the materials' enthalpy of formation, where a threshold value seems to exist at approximately -1.25 eV/atom (∼-120 kJ/mol atoms). For each sample, the observed amount of damage was found to have a linear dependence to the energy deposited by the ion beam per volume removed material. Despite the occurrence of sputter-damage in all samples, etching settings that result in almost artefact-free spectral data were found; using either very low energy (i.e. 200 eV) monoatomic ions, or an appropriate combination of ion cluster size and energy. The present study underlines that analysis post sputter-etching must be carried out with an awareness of possible sputter-induced artefacts.

Method for fabricating high aspect ratio structures in perovskite material

DOEpatents

Karapetrov, Goran T.; Kwok, Wai-Kwong; Crabtree, George W.; Iavarone, Maria

2003-10-28

A method of fabricating high aspect ratio ceramic structures in which a selected portion of perovskite or perovskite-like crystalline material is exposed to a high energy ion beam for a time sufficient to cause the crystalline material contacted by the ion beam to have substantially parallel columnar defects. Then selected portions of the material having substantially parallel columnar defects are etched leaving material with and without substantially parallel columnar defects in a predetermined shape having high aspect ratios of not less than 2 to 1. Etching is accomplished by optical or PMMA lithography. There is also disclosed a structure of a ceramic which is superconducting at a temperature in the range of from about 10.degree. K. to about 90.degree. K. with substantially parallel columnar defects in which the smallest lateral dimension of the structure is less than about 5 microns, and the thickness of the structure is greater than 2 times the smallest lateral dimension of the structure.

High quality InP-on-Si for solar cell applications

NASA Technical Reports Server (NTRS)

Shellenbarger, Zane A.; Goodwin, Thomas A.; Collins, Sandra R.; Dinetta, Louis C.

1994-01-01

InP on Si solar cells combine the low-cost and high-strength of Si with the high efficiency and radiation tolerance of InP. The main obstacle in the growth of single crystal InP-on-Si is the high residual strain and high dislocation density of the heteroepitaxial InP films. The dislocations result from the large differences in lattice constant and thermal expansion mismatch of InP and Si. Adjusting the size and geometry of the growth area is one possible method of addressing this problem. In this work, we conducted a material quality study of liquid phase epitaxy overgrowth layers on selective area InP grown by a proprietary vapor phase epitaxy technique on Si. The relationship between growth area and dislocation density was quantified using etch pit density measurements. Material quality of the InP on Si improved both with reduced growth area and increased aspect ratio (length/width) of the selective area. Areas with etch pit density as low as 1.6 x 10(exp 4) sq cm were obtained. Assuming dislocation density is an order of magnitude greater than etch pit density, solar cells made with this material could achieve the maximum theoretical efficiency of 23% at AMO. Etch pit density dependence on the orientation of the selective areas on the substrate was also studied.

Inductively Coupled Plasma-Induced Electrical Damage on HgCdTe Etched Surface at Cryogenic Temperatures

NASA Astrophysics Data System (ADS)

Liu, L. F.; Chen, Y. Y.; Ye, Z. H.; Hu, X. N.; Ding, R. J.; He, L.

2018-03-01

Plasma etching is a powerful technique for transferring high-resolution lithographic patterns into HgCdTe material with low etch-induced damage, and it is important for fabricating small-pixel-size HgCdTe infrared focal plane array (IRFPA) detectors. P- to n-type conversion is known to occur during plasma etching of vacancy-doped HgCdTe; however, it is usually unwanted and its removal requires extra steps. Etching at cryogenic temperatures can reduce the etch-induced type conversion depth in HgCdTe via the electrical damage mechanism. Laser beam-induced current (LBIC) is a nondestructive photoelectric characterization technique which can provide information regarding the vertical and lateral electrical field distribution, such as defects and p-n junctions. In this work, inductively coupled plasma (ICP) etching of HgCdTe was implemented at cryogenic temperatures. For an Ar/CH4 (30:1 in SCCM) plasma with ICP input power of 1000 W and RF-coupled DC bias of ˜ 25 V, a HgCdTe sample was dry-etched at 123 K for 5 min using ICP. The sample was then processed to remove a thin layer of the plasma-etched region while maintaining a ladder-like damaged layer by continuously controlling the wet chemical etching time. Combining the ladder etching method and LBIC measurement, the ICP etching-induced electrical damage depth was measured and estimated to be about 20 nm. The results indicate that ICP etching at cryogenic temperatures can significantly suppress plasma etching-induced electrical damage, which is beneficial for defining HgCdTe mesa arrays.

Morphological evolution and characterization of GaN pyramid arrays fabricated by photo-assisted chemical etching

NASA Astrophysics Data System (ADS)

Zhang, Shiying; Xiu, Xiangqian; Xu, Qingjun; Li, Yuewen; Hua, Xuemei; Chen, Peng; Xie, Zili; Liu, Bin; Zhou, Yugang; Han, Ping; Zhang, Rong; Zheng, Youdou

2016-12-01

GaN pyramid arrays have been successfully synthesized by selective photo-assisted chemical etching in a K2S2O8/KOH solution. A detailed analysis of time evolution of surface morphology has been conducted, which describes an etching process of GaN pyramids. Room temperature cathodoluminescence images indicate that these pyramids are composed of crystalline GaN surrounding dislocations, which is caused by the greater recombination rate of electrons and holes at dislocation than that of crystalline GaN. The Raman results show a stress relaxation in GaN pyramids compared with unetched GaN. The optical property of both unetched GaN and GaN pyramids has been studied by photoluminescence. The formation mechanism and feature of GaN pyramids are also rationally explained.

Silicon etching using only Oxygen at high temperature: An alternative approach to Si micro-machining on 150 mm Si wafers

NASA Astrophysics Data System (ADS)

Chai, Jessica; Walker, Glenn; Wang, Li; Massoubre, David; Tan, Say Hwa; Chaik, Kien; Hold, Leonie; Iacopi, Alan

2015-12-01

Using a combination of low-pressure oxygen and high temperatures, isotropic and anisotropic silicon (Si) etch rates can be controlled up to ten micron per minute. By varying the process conditions, we show that the vertical-to-lateral etch rate ratio can be controlled from 1:1 isotropic etch to 1.8:1 anisotropic. This simple Si etching technique combines the main respective advantages of both wet and dry Si etching techniques such as fast Si etch rate, stiction-free, and high etch rate uniformity across a wafer. In addition, this alternative O2-based Si etching technique has additional advantages not commonly associated with dry etchants such as avoiding the use of halogens and has no toxic by-products, which improves safety and simplifies waste disposal. Furthermore, this process also exhibits very high selectivity (>1000:1) with conventional hard masks such as silicon carbide, silicon dioxide and silicon nitride, enabling deep Si etching. In these initial studies, etch rates as high as 9.2 μm/min could be achieved at 1150 °C. Empirical estimation for the calculation of the etch rate as a function of the feature size and oxygen flow rate are presented and used as proof of concepts.

Silicon cells made by self-aligned selective-emitter plasma-etchback process

DOEpatents

Ruby, Douglas S.; Schubert, William K.; Gee, James M.; Zaidi, Saleem H.

2000-01-01

Photovoltaic cells and methods for making them are disclosed wherein the metallized grids of the cells are used to mask portions of cell emitter regions to allow selective etching of phosphorus-doped emitter regions. The preferred etchant is SF.sub.6 or a combination of SF.sub.6 and O.sub.2. This self-aligned selective etching allows for enhanced blue response (versus cells with uniform heavy doping of the emitter) while preserving heavier doping in the region beneath the gridlines needed for low contact resistance. Embodiments are disclosed for making cells with or without textured surfaces. Optional steps include plasma hydrogenation and PECVD nitride deposition, each of which are suited to customized applications for requirements of given cells to be manufactured. The techniques disclosed could replace expensive and difficult alignment methodologies used to obtain selectively etched emitters, and they may be easily integrated with existing plasma processing methods and techniques of the invention may be accomplished in a single plasma-processing chamber.

Influence of different conditioning methods on the shear bond strength of novel light-curing nano-ionomer restorative to enamel and dentin.

PubMed

Korkmaz, Yonca; Ozel, Emre; Attar, Nuray; Ozge Bicer, Ceren

2010-11-01

The purpose of this study was to investigate shear bond strength (SBS) between a light-curing nano-ionomer restorative and enamel or dentin after acid etching, after erbium:yttrium-aluminum-garnet (Er:YAG) laser etching, or after combined treatment. Forty third molars were selected, the crowns were sectioned, and 80 tooth slabs were obtained. The specimens were assigned to two groups, which were divided into four subgroups(n = 10). Group 1 [enamel (e)], treated with 37% phosphoric acid (A) + Ketac nano-primer (K); group 2 [dentin (d)], (A) + (K); group 3(e), Er:YAG laser etching (L) + (A) + (K); group 4(d), (L) + (A) + (K); group 5(e), (L) + (K); group 6(d), (L) + (K); group 7(e), (K); group 8(d), (K). The SBS of the specimens was measured with a universal test machine (1 mm/min). Data were analyzed by independent samples t-test, one-way analysis of variance (ANOVA) and a post-hoc Duncan test (p < 0.05). No difference was determined between groups 3 and 5 (p > 0.05). Group 7 exhibited higher SBS values than those of groups 3 and 5 (p < 0.05). Group 1 showed higher SBSs than those of groups 3, 5 and 7 (p < 0.05). There was no significant difference between groups 4 and 6 (p > 0.05). No difference was observed between groups 2 and 4 (p > 0.05). However, group 2 presented higher SBSs than did group 6 (p < 0.05). Group 8 exhibited the highest SBS values when compared with groups 2, 4 and 6 (p < 0.05). Er:YAG laser adversely affected the adhesion of the light-curing nano-ionomer restorative to both enamel and dentin.

Two-year Randomized Clinical Trial of Self-etching Adhesives and Selective Enamel Etching.

PubMed

Pena, C E; Rodrigues, J A; Ely, C; Giannini, M; Reis, A F

2016-01-01

The aim of this randomized, controlled prospective clinical trial was to evaluate the clinical effectiveness of restoring noncarious cervical lesions with two self-etching adhesive systems applied with or without selective enamel etching. A one-step self-etching adhesive (Xeno V(+)) and a two-step self-etching system (Clearfil SE Bond) were used. The effectiveness of phosphoric acid selective etching of enamel margins was also evaluated. Fifty-six cavities were restored with each adhesive system and divided into two subgroups (n=28; etch and non-etch). All 112 cavities were restored with the nanohybrid composite Esthet.X HD. The clinical effectiveness of restorations was recorded in terms of retention, marginal integrity, marginal staining, caries recurrence, and postoperative sensitivity after 3, 6, 12, 18, and 24 months (modified United States Public Health Service). The Friedman test detected significant differences only after 18 months for marginal staining in the groups Clearfil SE non-etch (p=0.009) and Xeno V(+) etch (p=0.004). One restoration was lost during the trial (Xeno V(+) etch; p>0.05). Although an increase in marginal staining was recorded for groups Clearfil SE non-etch and Xeno V(+) etch, the clinical effectiveness of restorations was considered acceptable for the single-step and two-step self-etching systems with or without selective enamel etching in this 24-month clinical trial.

Cyclic etching of tin-doped indium oxide using hydrogen-induced modified layer

NASA Astrophysics Data System (ADS)

Hirata, Akiko; Fukasawa, Masanaga; Nagahata, Kazunori; Li, Hu; Karahashi, Kazuhiro; Hamaguchi, Satoshi; Tatsumi, Tetsuya

2018-06-01

The rate of etching of tin-doped indium oxide (ITO) and the effects of a hydrogen-induced modified layer on cyclic, multistep thin-layer etching were investigated. It was found that ITO cyclic etching is possible by precisely controlling the hydrogen-induced modified layer. Highly selective etching of ITO/SiO2 was also investigated, and it was suggested that cyclic etching by selective surface adsorption of Si can precisely control the etch rates of ITO and SiO2, resulting in an almost infinite selectivity for ITO over SiO2 and in improved profile controllability.

Comparative study between REAP 200 and FEP171 CAR with 50-kV raster e-beam system for sub-100-nm technology

NASA Astrophysics Data System (ADS)

Baik, Ki-Ho; Lem, Homer Y.; Dean, Robert L.; Osborne, Stephen; Mueller, Mark; Abboud, Frank E.

2003-08-01

In this paper, a process established with a positive-tone chemically amplified resist (CAR) from TOK REAP200 and Fujifilm Arch FEP171 and 50kV MEBES system is discussed. This TOK resist is developed for raster scan 50 kV e-beam systems. It has high contrast, good coating characteristics, good dry etch selectivity, and high environmental stability. In the mask industries, the most popular positive tone CAR is FEP171, which is a high activation energy type CAR. REAP (Raster E-beam Advanced Process) 200 is low activation energy type and new acetal protecting polymer. In this study, we compared to these different type resists in terms of contrast, PAB and PEB latitude, resist profile, footing, T-topping, PED stability, LER, Global CDU (Critical Dimension Uniformity) and resolution. The REAP200 Resist obtained 75nm isolated lines and spaces, 90nm dense patterns with vertical profile, and a good stability of delay time.

Selective etching of TiN over TaN and vice versa in chlorine-containing plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Hyungjoo; Zhu Weiye; Liu Lei

2013-05-15

Selectivity of etching between physical vapor-deposited TiN and TaN was studied in chlorine-containing plasmas, under isotropic etching conditions. Etching rates for blanket films were measured in-situ using optical emission of the N{sub 2} (C{sup 3}{Pi}{sub u}{yields}B{sup 3}{Pi}{sub g}) bandhead at 337 nm to determine the etching time, and transmission electron microscopy to determine the starting film thickness. The etching selectivity in Cl{sub 2}/He or HCl/He plasmas was poor (<2:1). There was a window of very high selectivity of etching TiN over TaN by adding small amounts (<1%) of O{sub 2} in the Cl{sub 2}/He plasma. Reverse selectivity (10:1 of TaNmore » etching over TiN) was observed when adding small amounts of O{sub 2} to the HCl/He plasma. Results are explained on the basis of the volatility of plausible reaction products.« less

Dopant Selective Reactive Ion Etching of Silicon Carbide

NASA Technical Reports Server (NTRS)

Okojie, Robert (Inventor)

2016-01-01

A method for selectively etching a substrate is provided. In one embodiment, an epilayer is grown on top of the substrate. A resistive element may be defined and etched into the epilayer. On the other side of the substrate, the substrate is selectively etched up to the resistive element, leaving a suspended resistive element.

Alternating SiCl4/O2 passivation steps with SF6 etch steps for silicon deep etching

NASA Astrophysics Data System (ADS)

Duluard, C. Y.; Ranson, P.; Pichon, L. E.; Pereira, J.; Oubensaid, E. H.; Lefaucheux, P.; Puech, M.; Dussart, R.

2011-06-01

Deep etching of silicon has been investigated in an inductively coupled plasma etch reactor using short SiCl4/O2 plasma steps to passivate the sidewalls of the etched structures. A study was first carried out to define the appropriate parameters to create, at a substrate temperature of -20 °C, a passivation layer by SiCl4/O2 plasma that resists lateral chemical etching in SF6 plasma. The most efficient passivation layer was obtained for a SiCl4/O2 gas flow ratio of 2:1, a pressure of 1 Pa and a source power of 1000 W. Ex situ analyses on a film deposited with these parameters show that it is very rich in oxygen. Silicon etching processes that alternate SF6 plasma etch steps with SiCl4/O2 plasma passivation steps were then developed. Preliminary tests in pulsed-mode conditions have enabled etch rates greater than 2 µm min-1 with selectivities higher than 220. These results show that it is possible to develop a silicon deep etching process at substrate temperatures around -20 °C that uses low SiCl4 and O2 gas flows instead of conventional fluorocarbon gases for sidewall protection.

Selective dry etching of silicon containing anti-reflective coating

NASA Astrophysics Data System (ADS)

Sridhar, Shyam; Nolan, Andrew; Wang, Li; Karakas, Erdinc; Voronin, Sergey; Biolsi, Peter; Ranjan, Alok

2018-03-01

Multi-layer patterning schemes involve the use of Silicon containing Anti-Reflective Coating (SiARC) films for their anti-reflective properties. Patterning transfer completion requires complete and selective removal of SiARC which is very difficult due to its high silicon content (>40%). Typically, SiARC removal is accomplished through a non-selective etch during the pattern transfer process using fluorine containing plasmas, or an ex-situ wet etch process using hydrofluoric acid is employed to remove the residual SiARC, post pattern transfer. Using a non-selective etch may result in profile distortion or wiggling, due to distortion of the underlying organic layer. The drawbacks of using wet etch process for SiARC removal are increased overall processing time and the need for additional equipment. Many applications may involve patterning of active structures in a poly-Si layer with an underlying oxide stopping layer. In such applications, SiARC removal selective to oxide using a wet process may prove futile. Removing SiARC selectively to SiO2 using a dry etch process is also challenging, due to similarity in the nature of chemical bonds (Si - O) in the two materials. In this work, we present highly selective etching of SiARC, in a plasma driven by a surface wave radial line slot antenna. The first step in the process involves an in-situ modification of the SiARC layer in O2 plasma followed by selective etching in a NF3/H2 plasma. Surface treatment in O2 plasma resulted in enhanced etching of the SiARC layer. For the right processing conditions, in-situ NF3/H2 dry etch process demonstrated selectivity values greater than 15:1 with respect to SiO2. The etching chemistry, however, was sensitive to NF3:H2 gas ratio. For dilute NF3 in H2, no SiARC etching was observed. Presumably, this is due to the deposition of ammonium fluorosilicate layer that occurs for dilute NF3/H2 plasmas. Additionally, challenges involved in selective SiARC removal (selective to SiO2, organic and Si layers) post pattern transfer, in a multi-layer structure will be discussed.

Performance of InGaAs short wave infrared avalanche photodetector for low flux imaging

NASA Astrophysics Data System (ADS)

Singh, Anand; Pal, Ravinder

2017-11-01

Opto-electronic performance of the InGaAs/i-InGaAs/InP short wavelength infrared focal plane array suitable for high resolution imaging under low flux conditions and ranging is presented. More than 85% quantum efficiency is achieved in the optimized detector structure. Isotropic nature of the wet etching process poses a challenge in maintaining the required control in the small pitch high density detector array. Etching process is developed to achieve low dark current density of 1 nA/cm2 in the detector array with 25 µm pitch at 298 K. Noise equivalent photon performance less than one is achievable showing single photon detection capability. The reported photodiode with low photon flux is suitable for active cum passive imaging, optical information processing and quantum computing applications.

ScAlN etch mask for highly selective silicon etching

DOE PAGES

Henry, Michael David; Young, Travis R.; Griffin, Ben

2017-09-08

Here, this work reports the utilization of a recently developed film, ScAlN, as a silicon etch mask offering significant improvements in high etch selectivity to silicon. Utilization of ScAlN as a fluorine chemistry based deep reactive ion etch mask demonstrated etch selectivity at 23 550:1, four times better than AlN, 11 times better than Al 2O 3, and 148 times better than silicon dioxide with significantly less resputtering at high bias voltage than either Al 2O 3 or AlN. Ellipsometry film thickness measurements show less than 0.3 nm/min mask erosion rates for ScAlN. Micromasking of resputtered Al for Al 2Omore » 3, AlN, and ScAlN etch masks is also reported here, utilizing cross-sectional scanning electron microscope and confocal microscope roughness measurements. With lower etch bias, the reduced etch rate can be optimized to achieve a trench bottom surface roughness that is comparable to SiO 2 etch masks. Etch mask selectivity enabled by ScAlN is likely to make significant improvements in microelectromechanical systems, wafer level packaging, and plasma dicing of silicon.« less

Effects of a non-rinse conditioner on the enamel of primary teeth.

PubMed

Fava, Marcelo; Myaki, Silvio Issáo; Arana-Chavez, Victor Elias; Fava-de-Moraes, Flavio

2003-01-01

The aim of this in vitro study was to evaluate by scanning electron microscopy the morphological aspects of the enamel of primary teeth after etching with 36% phosphoric acid or a non-rinse conditioner. Ten naturally exfoliated anterior primary teeth were selected. The samples were subjected to prophylaxis with pumice paste and water using a low-speed hand piece. Etching was done on the buccal surface. Specimens were divided into 2 groups: G1 (n=10): etching with 36% phosphoric acid gel - Conditioner 36 (Dentsply) for 20 s, followed by water rinse for 15 s; G2 (n=10): etching with NRC - Non Rinse Conditioner (Dentsply) for 20 s, followed by air drying for 15 s. The samples were dehydrated, mounted on metal stubs, coated with gold and observed with Jeol JSM-6100 scanning electron microscope. Electron-micrographic analysis showed that both etching agents were effective for etching the enamel of primary teeth causing the formation of microporosities on the enamel surface, although the etching pattern was more effective with the use of 36% phosphoric acid gel.

Determination of Etch Rate Behavior of 4H-SiC Using Chlorine Trifluoride Gas

NASA Astrophysics Data System (ADS)

Miura, Yutaka; Habuka, Hitoshi; Katsumi, Yusuke; Oda, Satoko; Fukai, Yasushi; Fukae, Katsuya; Kato, Tomohisa; Okumura, Hajime; Arai, Kazuo

2007-12-01

The etch rate of single-crystalline 4H-SiC is studied using chlorine trifluoride gas at 673-973 K and atmospheric pressure in a cold wall horizontal reactor. The 4H-SiC etch rate can be higher than 10 μm/min at substrate temperatures higher than 723 K. The etch rate increases with the chlorine trifluoride gas flow rate. The etch rate is calculated by taking into account the transport phenomena in the reactor including the chemical reaction at the substrate surface. The flat etch rate at the higher substrate temperatures is caused mainly by the relationship between the transport rate and the surface chemical reaction rate of chlorine trifluoride gas.

Nanosecond laser-induced back side wet etching of fused silica with a copper-based absorber liquid

NASA Astrophysics Data System (ADS)

Lorenz, Pierre; Zehnder, Sarah; Ehrhardt, Martin; Frost, Frank; Zimmer, Klaus; Schwaller, Patrick

2014-03-01

Cost-efficient machining of dielectric surfaces with high-precision and low-roughness for industrial applications is still challenging if using laser-patterning processes. Laser induced back side wet etching (LIBWE) using UV laser pulses with liquid heavy metals or aromatic hydrocarbons as absorber allows the fabrication of well-defined, nm precise, free-form surfaces with low surface roughness, e.g., needed for optical applications. The copper-sulphatebased absorber CuSO4/K-Na-Tartrate/NaOH/formaldehyde in water is used for laser-induced deposition of copper. If this absorber can also be used as precursor for laser-induced ablation, promising industrial applications combining surface structuring and deposition within the same setup could be possible. The etching results applying a KrF excimer (248 nm, 25 ns) and a Nd:YAG (1064 nm, 20 ns) laser are compared. The topography of the etched surfaces were analyzed by scanning electron microscopy (SEM), white light interferometry (WLI) as well as laser scanning microscopy (LSM). The chemical composition of the irradiated surface was studied by energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT-IR). For the discussion of the etching mechanism the laser-induced heating was simulated with finite element method (FEM). The results indicate that the UV and IR radiation allows micro structuring of fused silica with the copper-based absorber where the etching process can be explained by the laser-induced formation of a copper-based absorber layer.

Hafnium Oxide Film Etching Using Hydrogen Chloride Gas

NASA Astrophysics Data System (ADS)

Habuka, Hitoshi; Yamaji, Masahiko; Kobori, Yoshitsugu; Horii, Sadayoshi; Kunii, Yasuo

2009-12-01

Hydrogen chloride gas removes the hafnium oxide film formed by atomic layer deposition at the etch rate of about 1 nm/min. A 100 nm-thick hafnium oxide film was perfectly etched off at 1173 K for 60 min by 100% hydrogen chloride gas at 100 sccm. A weight decrease in the hafnium oxide film was observed at temperatures higher than ca. 600 K, which corresponds to the sublimation point of hafnium tetrachloride. The etching by-product is considered to be hafnium tetrachloride. The etching technique developed in this study is expected to be applicable to various processes, such as the cleaning of a hafnium oxide film deposition reactor.

Ultradeep electron cyclotron resonance plasma etching of GaN

DOE PAGES

Harrison, Sara E.; Voss, Lars F.; Torres, Andrea M.; ...

2017-07-25

Here, ultradeep (≥5 μm) electron cyclotron resonance plasma etching of GaN micropillars was investigated. Parametric studies on the influence of the applied radio-frequency power, chlorine content in a Cl 2/Ar etch plasma, and operating pressure on the etch depth, GaN-to-SiO 2 selectivity, and surface morphology were performed. Etch depths of >10 μm were achieved over a wide range of parameters. Etch rates and sidewall roughness were found to be most sensitive to variations in RF power and % Cl 2 in the etch plasma. Selectivities of >20:1 GaN:SiO 2 were achieved under several chemically driven etch conditions where a maximummore » selectivity of ~39:1 was obtained using a 100% Cl 2 plasma. The etch profile and (0001) surface morphology were significantly influenced by operating pressure and the chlorine content in the plasma. Optimized etch conditions yielded >10 μm tall micropillars with nanometer-scale sidewall roughness, high GaN:SiO 2 selectivity, and nearly vertical etch profiles. These results provide a promising route for the fabrication of ultradeep GaN microstructures for use in electronic and optoelectronic device applications. In addition, dry etch induced preferential crystallographic etching in GaN microstructures is also demonstrated, which may be of great interest for applications requiring access to non- or semipolar GaN surfaces.« less

A Dry-Etch Process for Low Temperature Superconducting Transition Edge Sensors for Far Infrared Bolometer Arrays

NASA Technical Reports Server (NTRS)

Allen, Christine A.; Chervenak, James A.; Hsieh, Wen-Ting; McClanahan, Richard A.; Miller, Timothy M.; Mitchell, Robert; Moseley, S. Harvey; Staguhn, Johannes; Stevenson, Thomas R.

2003-01-01

The next generation of ultra-low power bolometer arrays, with applications in far infrared imaging, spectroscopy and polarimetry, utilizes a superconducting bilayer as the sensing element to enable SQUID multiplexed readout. Superconducting transition edge sensors (TES s) are being produced with dual metal systems of superconductinghormal bilayers. The transition temperature (Tc) is tuned by altering the relative thickness of the superconductor with respect to the normal layer. We are currently investigating MoAu and MoCu bilayers. We have developed a dry-etching process for MoAu TES s with integrated molybdenum leads, and are working on adapting the process to MoCu. Dry etching has the advantage over wet etching in the MoAu system in that one can achieve a high degree of selectivity, greater than 10, using argon ME, or argon ion milling, for patterning gold on molybdenum. Molybdenum leads are subsequently patterned using fluorine plasma.. The dry-etch technique results in a smooth, featureless TES with sharp sidewalls, no undercutting of the Mo beneath the normal metal, and Mo leads with high critical current. The effects of individual processing parameters on the characteristics of the transition will be reported.

New frontiers of atomic layer etching

NASA Astrophysics Data System (ADS)

Sherpa, Sonam D.; Ranjan, Alok

2018-03-01

Interest in atomic layer etching (ALE) has surged recently because it offers several advantages over continuous or quasicontinuous plasma etching. These benefits include (1) independent control of ion energy, ion flux, and radical flux, (2) flux-independent etch rate that mitigates the iso-dense loading effects, and (3) ability to control the etch rate with atomic or nanoscale precision. In addition to these benefits, we demonstrate an area-selective etching for maskless lithography as a new frontier of ALE. In this paper, area-selective etching refers to the confinement of etching into the specific areas of the substrate. The concept of area-selective etching originated during our studies on quasi-ALE of silicon nitride which consists of sequential exposure of silicon nitride to hydrogen and fluorinated plasma. The findings of our studies reported in this paper suggest that it may be possible to confine the etching into specific areas of silicon nitride without using any mask by replacing conventional hydrogen plasma with a localized source of hydrogen ions.

The first neural probe integrated with light source (blue laser diode) for optical stimulation and electrical recording.

PubMed

Park, HyungDal; Shin, Hyun-Joon; Cho, Il-Joo; Yoon, Eui-sung; Suh, Jun-Kyo Francis; Im, Maesoon; Yoon, Euisik; Kim, Yong-Jun; Kim, Jinseok

2011-01-01

In this paper, we report a neural probe which can selectively stimulate target neurons optically through Si wet etched mirror surface and record extracellular neural signals in iridium oxide tetrodes. Consequently, the proposed approach provides to improve directional problem and achieve at least 150/m gap distance between stimulation and recording sites by wet etched mirror surface in V-groove. Also, we developed light source, blue laser diode (OSRAM Blue Laser Diode_PL 450), integration through simple jig for one-touch butt-coupling. Furthermore, optical power and impedance of iridium oxide tetrodes were measured as 200 μW on 5 mW from LD and 206.5 k Ω at 1 kHz and we demonstrated insertion test of probe in 0.5% agarose-gel successfully. We have successfully transmitted a light of 450 nm to optical fiber through the integrated LD using by butt-coupling method.

Single-expose patterning development for EUV lithography

NASA Astrophysics Data System (ADS)

De Silva, Anuja; Petrillo, Karen; Meli, Luciana; Shearer, Jeffrey C.; Beique, Genevieve; Sun, Lei; Seshadri, Indira; Oh, Taehwan; Han, Seulgi; Saulnier, Nicole; Lee, Joe; Arnold, John C.; Hamieh, Bassem; Felix, Nelson M.; Furukawa, Tsuyoshi; Singh, Lovejeet; Ayothi, Ramakrishnan

2017-03-01

Initial readiness of EUV (extreme ultraviolet) patterning was demonstrated in 2016 with IBM Alliance's 7nm device technology. The focus has now shifted to driving the 'effective' k1 factor and enabling the second generation of EUV patterning. With the substantial cost of EUV exposure there is significant interest in extending the capability to do single exposure patterning with EUV. To enable this, emphasis must be placed on the aspect ratios, adhesion, defectivity reduction, etch selectivity, and imaging control of the whole patterning process. Innovations in resist materials and processes must be included to realize the full entitlement of EUV lithography at 0.33NA. In addition, enhancements in the patterning process to enable good defectivity, lithographic process window, and post etch pattern fidelity are also required. Through this work, the fundamental material challenges in driving down the effective k1 factor will be highlighted.

Neutral beam and ICP etching of HKMG MOS capacitors: Observations and a plasma-induced damage model

NASA Astrophysics Data System (ADS)

Kuo, Tai-Chen; Shih, Tzu-Lang; Su, Yin-Hsien; Lee, Wen-Hsi; Current, Michael Ira; Samukawa, Seiji

2018-04-01

In this study, TiN/HfO2/Si metal-oxide-semiconductor (MOS) capacitors were etched by a neutral beam etching technique under two contrasting conditions. The configurations of neutral beam etching technique were specially designed to demonstrate a "damage-free" condition or to approximate "reactive-ion-etching-like" conditions to verify the effect of plasma-induced damage on electrical characteristics of MOS capacitors. The results show that by neutral beam etching (NBE), the interface state density (Dit) and the oxide trapped charge (Qot) were lower than routine plasma etching. Furthermore, the decrease in capacitor size does not lead to an increase in leakage current density, indicating less plasma induced side-wall damage. We present a plasma-induced gate stack damage model which we demonstrate by using these two different etching configurations. These results show that NBE is effective in preventing plasma-induced damage at the high-k/Si interface and on the high-k oxide sidewall and thus improve the electrical performance of the gate structure.

The Selective Epitaxy of Silicon at Low Temperatures.

NASA Astrophysics Data System (ADS)

Lou, Jen-Chung

1991-01-01

This dissertation has developed a process for the selective epitaxial growth (SEG) of silicon at low temperatures using a dichlorosilane-hydrogen mixture in a hot-wall low pressure chemical vapor deposition (LPCVD) reactor. Some basic issues concerning the quality of epilayers --substrate preparation, ex-situ and in-situ cleaning, and deposition cycle, have been studied. We find it necessary to use a plasma etch to open epitaxial windows for the SEG of Si. A cycled plasma etch, a thin sacrificial oxide growth, and an oxide etching step can completely remove plasma-etch-induced surface damage and contaminants, which result in high quality epilayers. A practical wafer cleaning step is developed for low temperature Si epitaxial growth. An ex-situ HF vapor treatment can completely remove chemical oxide from the silicon surface and retard the reoxidation of the silicon surface. An in-situ low-concentration DCS cycle can aid in decomposition of surface oxide during a 900 ^circC H_2 prebake step. An HF vapor treatment combined with a low-concentration of DCS cycle consistently achieves defect-free epilayers at 850^circC and lower temperatures. We also show that a BF_sp{2}{+ } or F^+ ion implantation is a potential ex-situ wafer cleaning process for SEG of Si at low temperatures. The mechanism for the formation of surface features on Si epilayers is also discussed. Based on O ^+ ion implantation, we showed that the oxygen incorporation in silicon epilayers suppresses the Si growth rate. Therefore, we attribute the formation of surface features to the local reduction of the Si growth rate due to the dissolution of oxide islands at the epi/substrate interface. Finally, with this developed process for the SEG of silicon, defect-free overgrown epilayers are also obtained. This achievement demonstrates the feasibility for the future silicon-on-oxide (SOI) manufacturing technology.

REAP (raster e-beam advanced process) using 50-kV raster e-beam system for sub-100-nm node mask technology

NASA Astrophysics Data System (ADS)

Baik, Ki-Ho; Dean, Robert L.; Mueller, Mark; Lu, Maiying; Lem, Homer Y.; Osborne, Stephen; Abboud, Frank E.

2002-07-01

A chemically amplified resist (CAR) process has been recognized as an approach to meet the demanding critical dimension (CD) specifications of 100nm node technology and beyond. Recently, significant effort has been devoted to optimizing CAR materials, which offer the characteristics required for next generation photomask fabrication. In this paper, a process established with a positive-tone CAR from TOK and 50kV MEBES eXara system is discussed. This resist is developed for raster scan 50 kV e-beam systems. It has high contrast, good coating characteristics, good dry etch selectivity, and high environmental stability. The coating process is conducted in an environment with amine concentration less than 2 ppb. A nitrogen environment is provided during plate transfer steps. Resolution using a 60nm writing grid is 90nm line and space patterns. CD linearity is maintained down to 240nm for isolated lines or spaces by applying embedded proximity effect correction (emPEC). Optimizations of post-apply bake (PAB) and post-expose bake (PEB) time, temperature, and uniformity are completed to improve adhesion, coating uniformity, and resolution. A puddle develop process is optimized to improve line edge roughness, edge slope, and resolution. Dry etch process is optimized on a TetraT system to transfer the resist image into the chrome layer with minimum etch bias.

Surface Modification of Plastic Substrates Using Atomic Hydrogen

NASA Astrophysics Data System (ADS)

Heya, Akira; Matsuo, Naoto

The surface properties of a plastic substrate were changed by a novel surface treatment called atomic hydrogen annealing (AHA). In this method, a plastic substrate was exposed to atomic hydrogen generated by cracking of hydrogen molecules on heated tungsten wire. Surface roughness was increased and halogen elements (F and Cl) were selectively etched by AHA. In addition, plastic surface was reduced by AHA. The surface can be modified by the recombination reaction of atomic hydrogen, the reduction reaction and selective etching of halogen atom. It is concluded that this method is a promising technique for improvement of adhesion between inorganic films and plastic substrates at low temperatures.

Electrical resistance oscillations during plastic deformation in A Ti-Al-Nb-Zr alloy at 4·2 K

NASA Astrophysics Data System (ADS)

Nikiforenko, V. N.; Lavrentev, F. F.

1986-10-01

The serrated plastic flow in titanium alloy containing 5% Al, 2·5% Zr and 2% Nb has been investigated by measuring its electrical resistance and applying selective chemical etching. The electrical resistance was found to oscillate under active deformation at 4·2 K. Analysis of the possible causes seems to indicate a dominant role of break by dislocation pile-ups through obstacles, viz second phase precipitates and grain boundaries.

Spin-on metal oxide materials with high etch selectivity and wet strippability

NASA Astrophysics Data System (ADS)

Yao, Huirong; Mullen, Salem; Wolfer, Elizabeth; McKenzie, Douglas; Rahman, Dalil; Cho, JoonYeon; Padmanaban, Munirathna; Petermann, Claire; Hong, SungEun; Her, YoungJun

2016-03-01

Metal oxide or metal nitride films are used as hard mask materials in semiconductor industry for patterning purposes due to their excellent etch resistances against the plasma etches. Chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques are usually used to deposit the metal containing materials on substrates or underlying films, which uses specialized equipment and can lead to high cost-of-ownership and low throughput. We have reported novel spin-on coatings that provide simple and cost effective method to generate metal oxide films possessing good etch selectivity and can be removed by chemical agents. In this paper, new spin-on Al oxide and Zr oxide hard mask formulations are reported. The new metal oxide formulations provide higher metal content compared to previously reported material of specific metal oxides under similar processing conditions. These metal oxide films demonstrate ultra-high etch selectivity and good pattern transfer capability. The cured films can be removed by various chemical agents such as developer, solvents or wet etchants/strippers commonly used in the fab environment. With high metal MHM material as an underlayer, the pattern transfer process is simplified by reducing the number of layers in the stack and the size of the nano structure is minimized by replacement of a thicker film ACL. Therefore, these novel AZ® spinon metal oxide hard mask materials can potentially be used to replace any CVD or ALD metal, metal oxide, metal nitride or spin-on silicon-containing hard mask films in 193 nm or EUV process.

O2 Plasma Etching and Antistatic Gun Surface Modifications for CNT Yarn Microelectrode Improve Sensitivity and Antifouling Properties.

PubMed

Yang, Cheng; Wang, Ying; Jacobs, Christopher B; Ivanov, Ilia N; Venton, B Jill

2017-05-16

Carbon nanotube (CNT) based microelectrodes exhibit rapid and selective detection of neurotransmitters. While different fabrication strategies and geometries of CNT microelectrodes have been characterized, relatively little research has investigated ways to selectively enhance their electrochemical properties. In this work, we introduce two simple, reproducible, low-cost, and efficient surface modification methods for carbon nanotube yarn microelectrodes (CNTYMEs): O 2 plasma etching and antistatic gun treatment. O 2 plasma etching was performed by a microwave plasma system with oxygen gas flow and the optimized time for treatment was 1 min. The antistatic gun treatment flows ions by the electrode surface; two triggers of the antistatic gun was the optimized number on the CNTYME surface. Current for dopamine at CNTYMEs increased 3-fold after O 2 plasma etching and 4-fold after antistatic gun treatment. When the two treatments were combined, the current increased 12-fold, showing the two effects are due to independent mechanisms that tune the surface properties. O 2 plasma etching increased the sensitivity due to increased surface oxygen content but did not affect surface roughness while the antistatic gun treatment increased surface roughness but not oxygen content. The effect of tissue fouling on CNT yarns was studied for the first time, and the relatively hydrophilic surface after O 2 plasma etching provided better resistance to fouling than unmodified or antistatic gun treated CNTYMEs. Overall, O 2 plasma etching and antistatic gun treatment improve the sensitivity of CNTYMEs by different mechanisms, providing the possibility to tune the CNTYME surface and enhance sensitivity.

Emission and reflection spectra from AlxGa1-xN/GaN single heterostructures

NASA Astrophysics Data System (ADS)

Reynolds, D. C.; Hoelscher, J.; Litton, C. W.; Collins, T. C.; Fitch, R.; Via, G. D.; Gillespie, J.; Crespo, A.; Jenkins, T. J.; Saxler, A.

2003-10-01

Emission and reflection spectra from AlGaN/GaN single heterostructures grown on SiC substrates were investigated. Two-dimensional electron gas (2DEG) transitions were observed in both emission and reflection. The transitions are sharp, associated with the excited state of the 2DEG, reflect the conservation of the K-selection rule, and are excitonlike. The transitions are also associated with both the A- and B-valence bands. To verify the origin of the reflection and emission spectra, the top AlGaN layer was removed by reactive ion etching. After etching, only the excitonic reflection and emission spectra associated with GaN were observed.

Anisotropic selective etching between SiGe and Si

NASA Astrophysics Data System (ADS)

Ishii, Yohei; Scott-McCabe, Ritchie; Yu, Alex; Okuma, Kazumasa; Maeda, Kenji; Sebastian, Joseph; Manos, Jim

2018-06-01

In Si/SiGe dual-channel FinFETs, it is necessary to simultaneously control the etched amounts of SiGe and Si. However, the SiGe etch rate is higher than the Si etch rate in not only halogen plasmas but also physical sputtering. In this study, we found that hydrogen plasma selectively etches Si over SiGe. The result shows that the selectivity of Si over SiGe can be up to 38 with increasing Ge concentration in SiGe. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) results indicate that hydrogen selectively bonds with Si rather than with Ge in SiGe. During the etching, hydrogen-induced Si surface segregation is also observed. It is also observed that the difference in etched amount between SiGe and Si can be controlled from positive to negative values even in Si/SiGe dual-channel fin patterning while maintaining the vertical profiles. Furthermore, no plasma-induced lattice damage was observed by transmission electron microscopy for both Si and SiGe fin sidewalls.

Cross-plane electrical and thermal transport in oxide metal/semiconductor superlattices

NASA Astrophysics Data System (ADS)

Jha, Pankaj

Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multiferroics, and thermoelectrics. Cross-plane electron filtering transport in metal/semiconductor superlattices provides a potential approach to increase the thermoelectric figure of merit (ZT). La0.67Sr0.33MnO3 (LSMO) and LaMnO3 (LMO) thin-film depositions were optimized using pulsed laser deposition (PLD) to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate (STO) substrates. X-ray diffraction and high-resolution reciprocal space mapping (RSM) indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively-coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal an effective barrier height of 220 meV. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 microV/K at 300K that increases to 16640 microV/K at 360K. The large Seebeck coefficient may arise due to hot electron and spin filtering as LSMO/LMO superlattice constituent materials exhibit spintronic properties where charges and spin current are intertwined and can generate a spin-Seebeck effect. The room temperature thermal conductivity achieved in low resistivity superlattices was 0.92 W/mK, which indicates that cross-plane phonon scattering at interfaces reduces the lattice contribution to the thermal conductivity. The giant contribution of spin-Seebeck, the large temperature dependence of the cross-plane power factor, and the low thermal conductivity in low resistance LSMO/LMO superlattices may offer opportunities to realize spin-magnetic thermoelectric devices, and suggests a direction for further investigations of the potential of LSMO/LMO oxide superlattices for thermoelectric devices.

Effects of oxygen plasma etching on Sb{sub 2}Te{sub 3} explored by torque detected quantum oscillations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Yuan, E-mail: yuan.yan@pi1.physik.uni-stuttgart.de, E-mail: martin.dressel@pi1.physik.uni-stuttgart.de; Heintze, Eric; Pracht, Uwe S.

2016-04-25

De Haas–van Alphen measurements evidence that oxygen plasma etching strongly affects the properties of the three-dimensional topological insulator Sb{sub 2}Te{sub 3}. The quantum oscillations in magnetization down to low temperature (T ≥ 2 K) and high magnetic field (B ≤ 7 T) have been systematically investigated using a high-sensitive cantilever torque magnetometer. The effective mass and the oscillation frequency obtained from de Haas–van Alphen measurements first increase and then decrease as the oxygen plasma etching time increases from 0 to 12 min, corresponding to an up- and down-shift of the Dirac point. We establish the cantilever torque magnetometer as a powerful contactless tool to investigate themore » oxygen sensitivity of the surface state in topological insulators.« less

Silicon Carbide Etching Using Chlorine Trifluoride Gas

NASA Astrophysics Data System (ADS)

Habuka, Hitoshi; Oda, Satoko; Fukai, Yasushi; Fukae, Katsuya; Takeuchi, Takashi; Aihara, Masahiko

2005-03-01

The etch rate, chemical reactions and etched surface of β-silicon carbide are studied in detail using chlorine trifluoride gas. The etch rate is greater than 10 μm min-1 at 723 K with a flow rate of 0.1 \\ell min-1 at atmospheric pressure in a horizontal reactor. The maximum etch rate at a substrate temperature of 773 K is 40 μm min-1 with a flow rate of 0.25 \\ell min-1. The step-like pattern that initially exists on the β-silicon carbide surface tends to be smoothed; the root-mean-square surface roughness decreases from its initial value of 5 μm to 1 μm within 15 min; this minimum value is maintained for more than 15 min. Therefore, chlorine trifluoride gas is considered to have a large etch rate for β-silicon carbide associated with making a rough surface smooth.

In Situ Fabrication and Reactivation of Highly Selective and Stable Ag Catalysts for Electrochemical CO2 Conversion.

PubMed

Ma, Ming; Liu, Kai; Shen, Jie; Kas, Recep; Smith, Wilson A

2018-06-08

In this work, the highly selective and stable electrocatalytic reduction of CO 2 to CO on nanostructured Ag electrocatalysts is presented. The Ag electrocatalysts are synthesized by the electroreduction of Ag 2 CO 3 formed by in situ anodic-etching of Ag foil in a KHCO 3 electrolyte. After 3 min of this etching treatment, the Ag 2 CO 3 -derived nanostructured Ag electrocatalysts are capable of producing CO with up to 92% Faradaic efficiency at an overpotential as low as 290 mV, which surpasses all of the reported Ag catalysts at identical conditions to date. In addition, the anodic-etched Ag retained ∼90% catalytic selectivity in the electroreduction of CO 2 to CO for more than 100 h. The Ag 2 CO 3 -derived Ag is able to facilitate the activation of CO 2 via reduction of the activation energy barrier of the initial electron transfer and provide an increased number of active sites, resulting in the dramatically improved catalytic activity for the reduction of CO 2 to CO.

Height-selective etching for regrowth of self-aligned contacts using MBE

NASA Astrophysics Data System (ADS)

Burek, G. J.; Wistey, M. A.; Singisetti, U.; Nelson, A.; Thibeault, B. J.; Bank, S. R.; Rodwell, M. J. W.; Gossard, A. C.

2009-03-01

Advanced III-V transistors require unprecedented low-resistance contacts in order to simultaneously scale bandwidth, fmax and ft with the physical active region [M.J.W. Rodwell, M. Le, B. Brar, in: Proceedings of the IEEE, 96, 2008, p. 748]. Low-resistance contacts have been previously demonstrated using molecular beam epitaxy (MBE), which provides active doping above 4×10 19 cm -3 and permits in-situ metal deposition for the lowest resistances [U. Singisetti, M.A. Wistey, J.D. Zimmerman, B.J. Thibeault, M.J.W. Rodwell, A.C. Gossard, S.R. Bank, Appl. Phys. Lett., submitted]. But MBE is a blanket deposition technique, and applying MBE regrowth to deep-submicron lateral device dimensions is difficult even with advanced lithography techniques. We present a simple method for selectively etching undesired regrowth from the gate or mesa of a III-V MOSFET or laser, resulting in self-aligned source/drain contacts regardless of the device dimensions. This turns MBE into an effectively selective area growth technique.

Low resistivity of graphene nanoribbons with zigzag-dominated edge fabricated by hydrogen plasma etching combined with Zn/HCl pretreatment

NASA Astrophysics Data System (ADS)

Liu, Fengkui; Li, Qi; Wang, Rubing; Xu, Jianbao; Hu, Junxiong; Li, Weiwei; Guo, Yufen; Qian, Yuting; Deng, Wei; Ullah, Zaka; Zeng, Zhongming; Sun, Mengtao; Liu, Liwei

2017-11-01

Graphene nanoribbons (GNRs) have attracted intensive research interest owing to their potential applications in high performance graphene-based electronics. However, the deterioration of electrical performance caused by edge disorder is still an important obstacle to the applications. Here, we report the fabrication of low resistivity GNRs with a zigzag-dominated edge through hydrogen plasma etching combined with the Zn/HCl pretreatment method. This method is based on the anisotropic etching properties of hydrogen plasma in the vicinity of defects created by sputtering zinc (Zn) onto planar graphene. The polarized Raman spectra measurement of GNRs exhibits highly polarization dependence, which reveals the appearance of the zigzag-dominated edge. The as-prepared GNRs exhibit high carrier mobility (˜1332.4 cm2 v-1 s-1) and low resistivity (˜0.7 kΩ) at room temperature. Particularly, the GNRs can carry large current density (5.02 × 108 A cm-2) at high voltage (20.0 V) in the air atmosphere. Our study develops a controllable method to fabricate zigzag edge dominated GNRs for promising applications in transistors, sensors, nanoelectronics, and interconnects.

Optimized plasma etch window of block copolymers and neutral brush layers for enhanced direct self-assembly pattern transfer into a hardmask layer

NASA Astrophysics Data System (ADS)

Brakensiek, Nickolas; Xu, Kui; Sweat, Daniel; Hockey, Mary Ann

2018-03-01

Directed self-assembly (DSA) of block copolymers (BCPs) is one of the most promising patterning technologies for future lithography nodes. However, one of the biggest challenges to DSA is the pattern transfer by plasma etching from BCP to hardmask (HM) because the etch selectivity between BCP and neutral brush layer underneath is usually not high enough to enable robust pattern transfer. This paper will explore the plasma etch conditions of both BCPs and neutral brush layers that may improve selectivity and allow a more robust pattern transfer of DSA patterns into the hardmask layer. The plasma etching parameters that are under investigation include the selection of oxidative or reductive etch chemistries, as well as plasma gas pressure, power, and gas mixture fractions. Investigation into the relationship between BCP/neutral brush layer materials with varying chemical compositions and the plasma etching conditions will be highlighted. The culmination of this work will demonstrate important etch parameters that allow BCPs and neutral brush layers to be etched into the underlying hardmask layer with a large process window.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henry, Michael David; Young, Travis R.; Griffin, Ben

Here, this work reports the utilization of a recently developed film, ScAlN, as a silicon etch mask offering significant improvements in high etch selectivity to silicon. Utilization of ScAlN as a fluorine chemistry based deep reactive ion etch mask demonstrated etch selectivity at 23 550:1, four times better than AlN, 11 times better than Al 2O 3, and 148 times better than silicon dioxide with significantly less resputtering at high bias voltage than either Al 2O 3 or AlN. Ellipsometry film thickness measurements show less than 0.3 nm/min mask erosion rates for ScAlN. Micromasking of resputtered Al for Al 2Omore » 3, AlN, and ScAlN etch masks is also reported here, utilizing cross-sectional scanning electron microscope and confocal microscope roughness measurements. With lower etch bias, the reduced etch rate can be optimized to achieve a trench bottom surface roughness that is comparable to SiO 2 etch masks. Etch mask selectivity enabled by ScAlN is likely to make significant improvements in microelectromechanical systems, wafer level packaging, and plasma dicing of silicon.« less

Optical ridge waveguides preserving the thermo-optic features in LiNbO3 crystals fabricated by combination of proton implantation and selective wet etching.

PubMed

Tan, Yang; Chen, Feng

2010-05-24

We report on a new, simple method to fabricate optical ridge waveguides in a z-cut LiNbO3 wafer by using proton implantation and selective wet etching. The measured modal field is well confined in the ridge waveguide region, which is also confirmed by the numerical simulation. With thermal annealing treatment at 400 degrees C, the propagation loss of the ridge waveguides is determined to be as low as approximately 0.9 dB/cm. In addition, the measured thermo-optic coefficients of the waveguides are in good agreement with those of the bulk, suggesting potential applications in integrated photonics.

Deterministic Placement of Quantum-Size Controlled Quantum Dots for Seamless Top-Down Integration

DOE PAGES

Fischer, Arthur J.; Anderson, P. Duke; Koleske, Daniel D.; ...

2017-08-18

We demonstrate a new route toward the integration and deterministic placement of quantum dots (QDs) within prepatterned nanostructures. Using standard electron-beam lithography (EBL) and inductively coupled plasma reactive-ion etching (ICP-RIE), we fabricate arrays of nanowires on a III-nitride platform. Next, we integrate QDs of controlled size within the prepatterned nanowires using a bandgap-selective, wet-etching technique: quantum-size-controlled photoelectrochemical (QSC-PEC) etching. Low-temperature microphotoluminescence (μ-PL) measurements of individual nanowires reveal sharp spectral signatures, indicative of QD formation. Further, internal quantum efficiency (IQE) measurements reveal a near order of magnitude improvement in emitter efficiency following QSC-PEC etching. Finally, second-order cross-correlation (g(2)(0)) measurements of individualmore » QDs directly confirm nonclassical, antibunching behavior. Lastly, our results illustrate an exciting approach toward the top-down integration of nonclassical light sources within nanophotonic platforms.« less

Deterministic Placement of Quantum-Size Controlled Quantum Dots for Seamless Top-Down Integration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, Arthur J.; Anderson, P. Duke; Koleske, Daniel D.

We demonstrate a new route toward the integration and deterministic placement of quantum dots (QDs) within prepatterned nanostructures. Using standard electron-beam lithography (EBL) and inductively coupled plasma reactive-ion etching (ICP-RIE), we fabricate arrays of nanowires on a III-nitride platform. Next, we integrate QDs of controlled size within the prepatterned nanowires using a bandgap-selective, wet-etching technique: quantum-size-controlled photoelectrochemical (QSC-PEC) etching. Low-temperature microphotoluminescence (μ-PL) measurements of individual nanowires reveal sharp spectral signatures, indicative of QD formation. Further, internal quantum efficiency (IQE) measurements reveal a near order of magnitude improvement in emitter efficiency following QSC-PEC etching. Finally, second-order cross-correlation (g(2)(0)) measurements of individualmore » QDs directly confirm nonclassical, antibunching behavior. Lastly, our results illustrate an exciting approach toward the top-down integration of nonclassical light sources within nanophotonic platforms.« less

Lateral electrochemical etching of III-nitride materials for microfabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Jung

Conductivity-selective lateral etching of III-nitride materials is described. Methods and structures for making vertical cavity surface emitting lasers with distributed Bragg reflectors via electrochemical etching are described. Layer-selective, lateral electrochemical etching of multi-layer stacks is employed to form semiconductor/air DBR structures adjacent active multiple quantum well regions of the lasers. The electrochemical etching techniques are suitable for high-volume production of lasers and other III-nitride devices, such as lasers, HEMT transistors, power transistors, MEMs structures, and LEDs.

Large-aperture focusing of x rays with micropore optics using dry etching of silicon wafers.

PubMed

Ezoe, Yuichiro; Moriyama, Teppei; Ogawa, Tomohiro; Kakiuchi, Takuya; Mitsuishi, Ikuyuki; Mitsuda, Kazuhisa; Aoki, Tatsuhiko; Morishita, Kohei; Nakajima, Kazuo

2012-03-01

Large-aperture focusing of Al K(α) 1.49 keV x-ray photons using micropore optics made from a dry-etched 4 in. (100 mm) silicon wafer is demonstrated. Sidewalls of the micropores are smoothed with high-temperature annealing to work as x-ray mirrors. The wafer is bent to a spherical shape to collect parallel x rays into a focus. Our result supports that this new type of optics allows for the manufacturing of ultralight-weight and high-performance x-ray imaging optics with large apertures at low cost. © 2012 Optical Society of America

Comparative study of resist stabilization techniques for metal etch processing

NASA Astrophysics Data System (ADS)

Becker, Gerry; Ross, Matthew F.; Wong, Selmer S.; Minter, Jason P.; Marlowe, Trey; Livesay, William R.

1999-06-01

This study investigates resist stabilization techniques as they are applied to a metal etch application. The techniques that are compared are conventional deep-UV/thermal stabilization, or UV bake, and electron beam stabilization. The electron beam tool use din this study, an ElectronCure system from AlliedSignal Inc., ELectron Vision Group, utilizes a flood electron source and a non-thermal process. These stabilization techniques are compared with respect to a metal etch process. In this study, two types of resist are considered for stabilization and etch: a g/i-line resist, Shipley SPR-3012, and an advanced i-line, Shipley SPR 955- Cm. For each of these resist the effects of stabilization on resist features are evaluated by post-stabilization SEM analysis. Etch selectivity in all cases is evaluated by using a timed metal etch, and measuring resists remaining relative to total metal thickness etched. Etch selectivity is presented as a function of stabilization condition. Analyses of the effects of the type of stabilization on this method of selectivity measurement are also presented. SEM analysis was also performed on the features after a compete etch process, and is detailed as a function of stabilization condition. Post-etch cleaning is also an important factor impacted by pre-etch resist stabilization. Results of post- etch cleaning are presented for both stabilization methods. SEM inspection is also detailed for the metal features after resist removal processing.

Anisotropic diamond etching through thermochemical reaction between Ni and diamond in high-temperature water vapour.

PubMed

Nagai, Masatsugu; Nakanishi, Kazuhiro; Takahashi, Hiraku; Kato, Hiromitsu; Makino, Toshiharu; Yamasaki, Satoshi; Matsumoto, Tsubasa; Inokuma, Takao; Tokuda, Norio

2018-04-27

Diamond possesses excellent physical and electronic properties, and thus various applications that use diamond are under development. Additionally, the control of diamond geometry by etching technique is essential for such applications. However, conventional wet processes used for etching other materials are ineffective for diamond. Moreover, plasma processes currently employed for diamond etching are not selective, and plasma-induced damage to diamond deteriorates the device-performances. Here, we report a non-plasma etching process for single crystal diamond using thermochemical reaction between Ni and diamond in high-temperature water vapour. Diamond under Ni films was selectively etched, with no etching at other locations. A diamond-etching rate of approximately 8.7 μm/min (1000 °C) was successfully achieved. To the best of our knowledge, this rate is considerably greater than those reported so far for other diamond-etching processes, including plasma processes. The anisotropy observed for this diamond etching was considerably similar to that observed for Si etching using KOH.

Design and Application of a High Sensitivity Piezoresistive Pressure Sensor for Low Pressure Conditions

PubMed Central

Yu, Huiyang; Huang, Jianqiu

2015-01-01

In this paper, a pressure sensor for low pressure detection (0.5 kPa–40 kPa) is proposed. In one structure (No. 1), the silicon membrane is partly etched to form a crossed beam on its top for stress concentration. An aluminum layer is also deposited as part of the beam. Four piezoresistors are fabricated. Two are located at the two ends of the beam. The other two are located at the membrane periphery. Four piezoresistors connect into a Wheatstone bridge. To demonstrate the stress concentrate effect of this structure, two other structures were designed and fabricated. One is a flat membrane structure (No. 2), the other is a structure with the aluminum beam, but without etched silicon (No. 3). The measurement results of these three structures show that the No.1 structure has the highest sensitivity, which is about 3.8 times that of the No. 2 structure and 2.7 times that of the No. 3 structure. They also show that the residual stress in the beam has some backside effect on the sensor performance. PMID:26371001

Effect of source frequency and pulsing on the SiO2 etching characteristics of dual-frequency capacitive coupled plasma

NASA Astrophysics Data System (ADS)

Kim, Hoe Jun; Jeon, Min Hwan; Mishra, Anurag Kumar; Kim, In Jun; Sin, Tae Ho; Yeom, Geun Young

2015-01-01

A SiO2 layer masked with an amorphous carbon layer (ACL) has been etched in an Ar/C4F8 gas mixture with dual frequency capacitively coupled plasmas under variable frequency (13.56-60 MHz)/pulsed rf source power and 2 MHz continuous wave (CW) rf bias power, the effects of the frequency and pulsing of the source rf power on the SiO2 etch characteristics were investigated. By pulsing the rf power, an increased SiO2 etch selectivity was observed with decreasing SiO2 etch rate. However, when the rf power frequency was increased, not only a higher SiO2 etch rate but also higher SiO2 etch selectivity was observed for both CW and pulse modes. A higher CF2/F ratio and lower electron temperature were observed for both a higher source frequency mode and a pulsed plasma mode. Therefore, when the C 1s binding states of the etched SiO2 surfaces were investigated using X-ray photoelectron spectroscopy (XPS), the increase of C-Fx bonding on the SiO2 surface was observed for a higher source frequency operation similar to a pulsed plasma condition indicating the increase of SiO2 etch selectivity over the ACL. The increase of the SiO2 etch rate with increasing etch selectivity for the higher source frequency operation appears to be related to the increase of the total plasma density with increasing CF2/F ratio in the plasma. The SiO2 etch profile was also improved not only by using the pulsed plasma but also by increasing the source frequency.

Eliminating dependence of hole depth on aspect ratio by forming ammonium bromide during plasma etching of deep holes in silicon nitride and silicon dioxide

NASA Astrophysics Data System (ADS)

Iwase, Taku; Yokogawa, Kenetsu; Mori, Masahito

2018-06-01

The reaction mechanism during etching to fabricate deep holes in SiN/SiO2 stacks by using a HBr/N2/fluorocarbon-based gas plasma was investigated. To etch SiN and SiO2 films simultaneously, HBr/fluorocarbon gas mixture ratio was controlled to achieve etching selectivity closest to one. Deep holes were formed in the SiN/SiO2 stacks by one-step etching at several temperatures. The surface composition of the cross section of the holes was analyzed by time-of-flight secondary-ion mass spectrometry. It was found that bromine ions (considered to be derived from NH4Br) were detected throughout the holes in the case of low-temperature etching. It was also found that the dependence of hole depth on aspect ratio decreases as temperature decreases, and it becomes significantly weaker at a substrate temperature of 20 °C. It is therefore concluded that the formation of NH4Br supplies the SiN/SiO2 etchant to the bottom of the holes. Such a finding will make it possible to alleviate the decrease in etching rate due to a high aspect ratio.

A novel methodology for litho-to-etch pattern fidelity correction for SADP process

NASA Astrophysics Data System (ADS)

Chen, Shr-Jia; Chang, Yu-Cheng; Lin, Arthur; Chang, Yi-Shiang; Lin, Chia-Chi; Lai, Jun-Cheng

2017-03-01

For 2x nm node semiconductor devices and beyond, more aggressive resolution enhancement techniques (RETs) such as source-mask co-optimization (SMO), litho-etch-litho-etch (LELE) and self-aligned double patterning (SADP) are utilized for the low k1 factor lithography processes. In the SADP process, the pattern fidelity is extremely critical since a slight photoresist (PR) top-loss or profile roughness may impact the later core trim process, due to its sensitivity to environment. During the subsequent sidewall formation and core removal processes, the core trim profile weakness may worsen and induces serious defects that affect the final electrical performance. To predict PR top-loss, a rigorous lithography simulation can provide a reference to modify mask layouts; but it takes a much longer run time and is not capable of full-field mask data preparation. In this paper, we first brought out an algorithm which utilizes multi-intensity levels from conventional aerial image simulation to assess the physical profile through lithography to core trim etching steps. Subsequently, a novel correction method was utilized to improve the post-etch pattern fidelity without the litho. process window suffering. The results not only matched PR top-loss in rigorous lithography simulation, but also agreed with post-etch wafer data. Furthermore, this methodology can also be incorporated with OPC and post-OPC verification to improve core trim profile and final pattern fidelity at an early stage.

Characterizing fluorocarbon assisted atomic layer etching of Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

NASA Astrophysics Data System (ADS)

Metzler, Dominik; Li, Chen; Engelmann, Sebastian; Bruce, Robert L.; Joseph, Eric A.; Oehrlein, Gottlieb S.

2017-02-01

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C4F8 and CHF3) and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J. Vac. Sci. Technol., A 32, 020603 (2014) and D. Metzler et al., J. Vac. Sci. Technol., A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO2 and Si but is limited with regard to control over material etching selectivity. Ion energy over the 20-30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF3 has a lower FC deposition yield for both SiO2 and Si and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F8. The thickness of deposited FC layers using CHF3 is found to be greater for Si than for SiO2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.

Nitrogen reactive ion etch processes for the selective removal of poly-(4-vinylpyridine) in block copolymer films.

PubMed

Flynn, Shauna P; Bogan, Justin; Lundy, Ross; Khalafalla, Khalafalla E; Shaw, Matthew; Rodriguez, Brian J; Swift, Paul; Daniels, Stephen; O'Connor, Robert; Hughes, Greg; Kelleher, Susan M

2018-08-31

Self-assembling block copolymer (BCP) patterns are one of the main contenders for the fabrication of nanopattern templates in next generation lithography technology. Transforming these templates to hard mark materials is key for pattern transfer and in some cases, involves selectively removing one block from the nanopattern. For poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP), a high χ BCP system which could be potentially incorporated into semiconductor nanofabrication, this selective removal is predominantly done by a wet etch/activation process. Conversely, this process has numerous disadvantages including lack of control and high generation of waste leading to high cost. For these reasons, our motivation was to move away from the wet etch process and optimise a dry etch which would overcome the limitations associated with the activation process. The work presented herein shows the development of a selective plasma etch process for the removal of P4VP cores from PS-b-P4VP nanopatterned film. Results have shown that a nitrogen reactive ion etch plasma has a selectivity for P4VP of 2.2:1 and suggest that the position of the nitrogen in the aromatic ring of P4VP plays a key role in this selectivity. In situ plasma etching and x-ray photoelectron spectrometry measurements were made without breaking vacuum, confirming that the nitrogen plasma has selectivity for removal of P4VP over PS.

A Study on Ohmic Contact to Dry-Etched p-GaN

NASA Astrophysics Data System (ADS)

Hu, Cheng-Yu; Ao, Jin-Ping; Okada, Masaya; Ohno, Yasuo

Low-power dry-etching process has been adopted to study the influence of dry-etching on Ohmic contact to p-GaN. When the surface layer of as-grown p-GaN was removed by low-power SiCl4/Cl2-etching, no Ohmic contact can be formed on the low-power dry-etched p-GaN. The same dry-etching process was also applied on n-GaN to understand the influence of the low-power dry-etching process. By capacitance-voltage (C-V) measurement, the Schottky barrier heights (SBHs) of p-GaN and n-GaN were measured. By comparing the change of measured SBHs on p-GaN and n-GaN, it was suggested that etching damage is not the only reason responsible for the degraded Ohmic contacts to dry-etched p-GaN and for Ohmic contact formatin, the original surface layer of as-grown p-GaN have some special properties, which were removed by dry-etching process. To partially recover the original surface of as-grown p-GaN, high temperature annealing (1000°C 30s) was tried on the SiCl4/Cl2-etched p-GaN and Ohmic contact was obtained.

Principles and applications of laser-induced liquid-phase jet-chemical etching

NASA Astrophysics Data System (ADS)

Stephen, Andreas; Metev, Simeon; Vollertsen, Frank

2003-11-01

In this treatment method laser radiation, which is guided from a coaxially expanding liquid jet-stream, locally initiates a thermochemical etching reaction on a metal surface, which leads to selective material removal at high resolution and quality of the treated surface as well as low thermal influence on the workpiece. Electrochemical investigations were performed under focused laser irradiation using a cw-Nd:YAG laser with a maximum power of 15 W and a simultaneous impact of the liquid jet-stream consisting of phosphoric acid with a maximum flow rate of 20 m/s. The time resolved measurements of the electrical potential difference against an electrochemical reference electrode were correlated with the specific processing parameters and corresponding etch rates to identify processing conditions for temporally stable and enhanced chemical etching reactions. Applications of laser-induced liquid-phase jet-chemical etching in the field of sensor technology, micromechanics and micrmoulding technology are presented. This includes the microstructuring of thin film systems, cutting of foils of shape memory alloys or the generation of structures with defined shape in bulk material.

Atomic-layer soft plasma etching of MoS2

PubMed Central

Xiao, Shaoqing; Xiao, Peng; Zhang, Xuecheng; Yan, Dawei; Gu, Xiaofeng; Qin, Fang; Ni, Zhenhua; Han, Zhao Jun; Ostrikov, Kostya (Ken)

2016-01-01

Transition from multi-layer to monolayer and sub-monolayer thickness leads to the many exotic properties and distinctive applications of two-dimensional (2D) MoS2. This transition requires atomic-layer-precision thinning of bulk MoS2 without damaging the remaining layers, which presently remains elusive. Here we report a soft, selective and high-throughput atomic-layer-precision etching of MoS2 in SF6 + N2 plasmas with low-energy (<0.4 eV) electrons and minimized ion-bombardment-related damage. Equal numbers of MoS2 layers are removed uniformly across domains with vastly different initial thickness, without affecting the underlying SiO2 substrate and the remaining MoS2 layers. The etching rates can be tuned to achieve complete MoS2 removal and any desired number of MoS2 layers including monolayer. Layer-dependent vibrational and photoluminescence spectra of the etched MoS2 are also demonstrated. This soft plasma etching technique is versatile, scalable, compatible with the semiconductor manufacturing processes, and may be applicable for a broader range of 2D materials and intended device applications. PMID:26813335

A low insertion loss GaAs pHEMT switch utilizing dual n +-doping AlAs etching stop layers design

NASA Astrophysics Data System (ADS)

Chien, Feng-Tso; Lin, Da-Wei; Yang, Chih-Wei; Fu, Jeffrey S.; Chiu, Hsien-Chin

2010-03-01

A low insertion loss single-pole-single-throw (SPST) pseudomorphic high electron mobility transistor (pHEMT) switch utilizing the n +-type doping in AlAs etching stop layer was fabricated and investigated. This novel design reduces device sheet resistance resulting in an improvement of dc and rf power performance. In addition, the gate recess selectivity for GaAs/AlAs interface was not sacrificed after highly n +-type doping in AlAs etching stop layer. The pHEMT with n +-AlAs etching stop layer, also named Modified pHEMT (M-pHEMT), demonstrated a lower sheet resistance ( Rsh) of 65.9 Ω/γ, a higher maximum drain-to-source current ( Idmax) of 317.8 mA/mm and a higher peak transconductance ( gm) of 259.3 mS/mm which are superior to standard pHEMT performance with values of 71.9 Ω/γ, 290.3 mA/mm and 252.1 mS/mm, respectively. Due to a significant sheet resistance improvement from this novel epitaxial design, an SPST pHEMT switch was realized to manifest its industrial application potential. The results achieved an on-state insertion loss of 1.42 dB, an off-state isolation of 13.02 dB at 0.9 GHz, which were superior to traditional pHEMT switch under same condition of operation with values of 1.68 dB and 11.42 dB, respectively. It is proved that dual n +-doping AlAs etching stop layers scheme is beneficial for low loss microwave switches applications.

Double exposure using 193nm negative tone photoresist

NASA Astrophysics Data System (ADS)

Kim, Ryoung-han; Wallow, Tom; Kye, Jongwook; Levinson, Harry J.; White, Dave

2007-03-01

Double exposure is one of the promising methods for extending lithographic patterning into the low k I regime. In this paper, we demonstrate double patterning of k 1-effective=0.25 with improved process window using a negative resist. Negative resist (TOK N- series) in combination with a bright field mask is proven to provide a large process window in generating 1:3 = trench:line resist features. By incorporating two etch transfer steps into the hard mask material, frequency doubled patterns could be obtained.

Study of Thermal Electrical Modified Etching for Glass and Its Application in Structure Etching

PubMed Central

Zhan, Zhan; Li, Wei; Yu, Lingke; Wang, Lingyun; Sun, Daoheng

2017-01-01

In this work, an accelerating etching method for glass named thermal electrical modified etching (TEM etching) is investigated. Based on the identification of the effect in anodic bonding, a novel method for glass structure micromachining is proposed using TEM etching. To validate the method, TEM-etched glasses are prepared and their morphology is tested, revealing the feasibility of the new method for micro/nano structure micromachining. Furthermore, two kinds of edge effect in the TEM and etching processes are analyzed. Additionally, a parameter study of TEM etching involving transferred charge, applied pressure, and etching roughness is conducted to evaluate this method. The study shows that TEM etching is a promising manufacture method for glass with low process temperature, three-dimensional self-control ability, and low equipment requirement. PMID:28772521

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzler, Dominik; Li, Chen; Engelmann, Sebastian

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching (ALE) processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO 2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C 4F 8 and CHF 3), and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J Vac Sci Technol A 32,more » 020603 (2014), and D. Metzler et al., J Vac Sci Technol A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO 2 and Si, but is limited with regard to control over material etching selectivity. Ion energy over the 20 to 30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF 3 has a lower FC deposition yield for both SiO 2 and Si, and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F 8. The thickness of deposited FC layers using CHF 3 is found to be greater for Si than for SiO 2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.« less

Microlens frames for laser diode arrays

DOEpatents

Skidmore, J.A.; Freitas, B.L.

1999-07-13

Monolithic microlens frames enable the fabrication of monolithic laser diode arrays and are manufactured inexpensively with high registration, and with inherent focal length compensation for any lens diameter variation. A monolithic substrate is used to fabricate a low-cost microlens array. The substrate is wet-etched or sawed with a series of v-grooves. The v-grooves can be created by wet-etching, by exploiting the large etch-rate selectivity of different crystal planes. The v-grooves provide a support frame for either cylindrical or custom-shaped microlenses. Because the microlens frames are formed by photolithographic semiconductor batch-processing techniques, they can be formed inexpensively over large areas with precise lateral and vertical registration. The v-groove has an important advantage for preserving the correct focus for lenses of varying diameter. 12 figs.

Microlens frames for laser diode arrays

DOEpatents

Skidmore, Jay A.; Freitas, Barry L.

1999-01-01

Monolithic microlens frames enable the fabrication of monolithic laser diode arrays and are manufactured inexpensively with high registration, and with inherent focal length compensation for any lens diameter variation. A monolithic substrate is used to fabricate a low-cost microlens array. The substrate is wet-etched or sawed with a series of v-grooves. The v-grooves can be created by wet-etching, by exploiting the large etch-rate selectivity of different crystal planes. The v-grooves provide a support frame for either cylindrical or custom-shaped microlenses. Because the microlens frames are formed by photolithographic semiconductor batch-processing techniques, they can be formed inexpensively over large areas with precise lateral and vertical registration. The v-groove has an important advantage for preserving the correct focus for lenses of varying diameter.

Seebeck Coefficient of Thermocouples from Nickel-Coated Carbon Fibers: Theory and Experiment.

PubMed

Hardianto, Hardianto; De Mey, Gilbert; Ciesielska-Wrόbel, Izabela; Hertleer, Carla; Van Langenhove, Lieva

2018-05-30

Thermocouples made of etched and non-etched nickel-coated carbon yarn (NiCCY) were investigated. Theoretic Seebeck coefficients were compared to experimental results from measurements of generated electric voltage by these thermocouples. The etching process for making thermocouples was performed by immersion of NiCCY in the solution containing a mixture of hydrochloric acid (HCl) (37% of concentration), and hydrogen peroxide (H₂O₂) in three different concentrations-3%, 6%, and 10%. Thirty minutes of etching to remove Ni from NiCCY was followed by washing and drying. Next, the ability to generate electrical voltage by the thermocouples (being a junction of the etched and the non-etched NiCCY) was measured in different ranges of temperatures, both a cold junction (291.15⁻293.15 K) and a hot junction (293.15⁻325.15 K). A formula predicting the Seebeck coefficient of this thermocouple was elaborated, taking into consideration resistance values of the tested samples. It was proven that there is a good agreement between the theoretical and experimental data, especially for the yarns etched with 6% and 10% peroxide (both were mixed with HCl). The electrical resistance of non-fully etched nickel remaining on the carbon fiber surface ( R 1 ) can have a significant effect on the thermocouples' characteristics.

Cryogenic Etching of High Aspect Ratio 400 nm Pitch Silicon Gratings.

PubMed

Miao, Houxun; Chen, Lei; Mirzaeimoghri, Mona; Kasica, Richard; Wen, Han

2016-10-01

The cryogenic process and Bosch process are two widely used processes for reactive ion etching of high aspect ratio silicon structures. This paper focuses on the cryogenic deep etching of 400 nm pitch silicon gratings with various etching mask materials including polymer, Cr, SiO 2 and Cr-on-polymer. The undercut is found to be the key factor limiting the achievable aspect ratio for the direct hard masks of Cr and SiO 2 , while the etch selectivity responds to the limitation of the polymer mask. The Cr-on-polymer mask provides the same high selectivity as Cr and reduces the excessive undercut introduced by direct hard masks. By optimizing the etching parameters, we etched a 400 nm pitch grating to ≈ 10.6 μ m depth, corresponding to an aspect ratio of ≈ 53.

Fabrication and characterization of a nanometer-sized optical fiber electrode based on selective chemical etching for scanning electrochemical/optical microscopy.

PubMed

Maruyama, Kenichi; Ohkawa, Hiroyuki; Ogawa, Sho; Ueda, Akio; Niwa, Osamu; Suzuki, Koji

2006-03-15

We have already reported a method for fabricating ultramicroelectrodes (Suzuki, K. JP Patent, 2004-45394, 2004). This method is based on the selective chemical etching of optical fibers. In this work, we undertake a detailed investigation involving a combination of etched optical fibers with various types of tapered tip (protruding-shape, double- (or pencil-) shape and triple-tapered electrode) and insulation with electrophoretic paint. Our goal is to establish a method for fabricating nanometer-sized optical fiber electrodes with high reproducibility. As a result, we realized pencil-shaped and triple-tapered electrodes that had radii in the nanometer range with high reproducibility. These nanometer-sized electrodes showed well-defined sigmoidal curves and stable diffusion-limited responses with cyclic voltammetry. The pencil-shaped optical fiber, which has a conical tip with a cone angle of 20 degrees , was effective for controlling the electrode radius. The pencil-shaped electrodes had higher reproducibility and smaller electrode radii (r(app) < 1.0 nm) than those of other etched optical fiber electrodes. By using a pencil-shaped electrode with a 105-nm radius as a probe, we obtained simultaneous electrochemical and optical images of an implantable interdigitated array electrode. We achieved nanometer-scale resolution with a combination of scanning electrochemical microscopy SECM and optical microscopy. The resolution of the electrochemical and optical images indicated sizes of 300 and 930 nm, respectively. The neurites of living PC12 cells were also successfully imaged on a 1.6-microm scale by using the negative feedback mode of an SECM.

Composition/bandgap selective dry photochemical etching of semiconductor materials

DOEpatents

Ashby, Carol I. H.; Dishman, James L.

1987-01-01

A method of selectively photochemically dry etching a first semiconductor material of a given composition and direct bandgap Eg.sub.1 in the presence of a second semiconductor material of a different composition and direct bandgap Eg.sub.2, wherein Eg.sub.2 >Eg.sub.1, said second semiconductor material substantially not being etched during said method, comprises subjecting both materials to the same photon flux and to the same gaseous etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said photons being of an energy greater than Eg.sub.1 but less than Eg.sub.2, whereby said first semiconductor material is photochemically etched and said second material is substantially not etched.

Method of sputter etching a surface

DOEpatents

Henager, Jr., Charles H.

1984-01-01

The surface of a target is textured by co-sputter etching the target surface with a seed material adjacent thereto, while the target surface is maintained at a pre-selected temperature. By pre-selecting the temperature of the surface while sputter etching, it is possible to predetermine the reflectance properties of the etched surface. The surface may be textured to absorb sunlight efficiently and have minimal emittance in the infrared region so as to be well-suited for use as a solar absorber for photothermal energy conversion.

Method of sputter etching a surface

DOEpatents

Henager, C.H. Jr.

1984-02-14

The surface of a target is textured by co-sputter etching the target surface with a seed material adjacent thereto, while the target surface is maintained at a pre-selected temperature. By pre-selecting the temperature of the surface while sputter etching, it is possible to predetermine the reflectance properties of the etched surface. The surface may be textured to absorb sunlight efficiently and have minimal emittance in the infrared region so as to be well-suited for use as a solar absorber for photothermal energy conversion. 4 figs.

Characterizing Fluorocarbon Assisted Atomic Layer Etching of Si Using Cyclic Ar/C 4F 8 and Ar/CHF 3 Plasma

DOE PAGES

Metzler, Dominik; Li, Chen; Engelmann, Sebastian; ...

2016-09-08

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching (ALE) processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO 2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C 4F 8 and CHF 3), and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J Vac Sci Technol A 32,more » 020603 (2014), and D. Metzler et al., J Vac Sci Technol A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO 2 and Si, but is limited with regard to control over material etching selectivity. Ion energy over the 20 to 30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF 3 has a lower FC deposition yield for both SiO 2 and Si, and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F 8. The thickness of deposited FC layers using CHF 3 is found to be greater for Si than for SiO 2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.« less

Modeling of block copolymer dry etching for directed self-assembly lithography

NASA Astrophysics Data System (ADS)

Belete, Zelalem; Baer, Eberhard; Erdmann, Andreas

2018-03-01

Directed self-assembly (DSA) of block copolymers (BCP) is a promising alternative technology to overcome the limits of patterning for the semiconductor industry. DSA exploits the self-assembling property of BCPs for nano-scale manufacturing and to repair defects in patterns created during photolithography. After self-assembly of BCPs, to transfer the created pattern to the underlying substrate, selective etching of PMMA (poly (methyl methacrylate)) to PS (polystyrene) is required. However, the etch process to transfer the self-assemble "fingerprint" DSA patterns to the underlying layer is still a challenge. Using combined experimental and modelling studies increases understanding of plasma interaction with BCP materials during the etch process and supports the development of selective process that form well-defined patterns. In this paper, a simple model based on a generic surface model has been developed and an investigation to understand the etch behavior of PS-b-PMMA for Ar, and Ar/O2 plasma chemistries has been conducted. The implemented model is calibrated for etch rates and etch profiles with literature data to extract parameters and conduct simulations. In order to understand the effect of the plasma on the block copolymers, first the etch model was calibrated for polystyrene (PS) and poly (methyl methacrylate) (PMMA) homopolymers. After calibration of the model with the homopolymers etch rate, a full Monte-Carlo simulation was conducted and simulation results are compared with the critical-dimension (CD) and selectivity of etch profile measurement. In addition, etch simulations for lamellae pattern have been demonstrated, using the implemented model.

Defect-selective dry etching for quick and easy probing of hexagonal boron nitride domains.

PubMed

Wu, Qinke; Lee, Joohyun; Park, Sangwoo; Woo, Hwi Je; Lee, Sungjoo; Song, Young Jae

2018-03-23

In this study, we demonstrate a new method to selectively etch the point defects or the boundaries of as-grown hexagonal boron nitride (hBN) films and flakes in situ on copper substrates using hydrogen and argon gases. The initial quality of the chemical vapor deposition-grown hBN films and flakes was confirmed by UV-vis absorption spectroscopy, atomic force microscopy, and transmission electron microscopy. Different gas flow ratios of Ar/H 2 were then employed to etch the same quality of samples and it was found that etching with hydrogen starts from the point defects and grows epitaxially, which helps in confirming crystalline orientations. However, etching with argon is sensitive to line defects (boundaries) and helps in visualizing the domain size. Finally, based on this defect-selective dry etching technique, it could be visualized that the domains of a polycrystalline hBN monolayer merged together with many parts, even with those that grew from a single nucleation seed.

Defect-selective dry etching for quick and easy probing of hexagonal boron nitride domains

NASA Astrophysics Data System (ADS)

Wu, Qinke; Lee, Joohyun; Park, Sangwoo; Woo, Hwi Je; Lee, Sungjoo; Song, Young Jae

2018-03-01

In this study, we demonstrate a new method to selectively etch the point defects or the boundaries of as-grown hexagonal boron nitride (hBN) films and flakes in situ on copper substrates using hydrogen and argon gases. The initial quality of the chemical vapor deposition-grown hBN films and flakes was confirmed by UV-vis absorption spectroscopy, atomic force microscopy, and transmission electron microscopy. Different gas flow ratios of Ar/H2 were then employed to etch the same quality of samples and it was found that etching with hydrogen starts from the point defects and grows epitaxially, which helps in confirming crystalline orientations. However, etching with argon is sensitive to line defects (boundaries) and helps in visualizing the domain size. Finally, based on this defect-selective dry etching technique, it could be visualized that the domains of a polycrystalline hBN monolayer merged together with many parts, even with those that grew from a single nucleation seed.

Maskless micro/nanofabrication on GaAs surface by friction-induced selective etching

PubMed Central

2014-01-01

In the present study, a friction-induced selective etching method was developed to produce nanostructures on GaAs surface. Without any resist mask, the nanofabrication can be achieved by scratching and post-etching in sulfuric acid solution. The effects of the applied normal load and etching period on the formation of the nanostructure were studied. Results showed that the height of the nanostructure increased with the normal load or the etching period. XPS and Raman detection demonstrated that residual compressive stress and lattice densification were probably the main reason for selective etching, which eventually led to the protrusive nanostructures from the scratched area on the GaAs surface. Through a homemade multi-probe instrument, the capability of this fabrication method was demonstrated by producing various nanostructures on the GaAs surface, such as linear array, intersecting parallel, surface mesas, and special letters. In summary, the proposed method provided a straightforward and more maneuverable micro/nanofabrication method on the GaAs surface. PMID:24495647

Method and system for optical figuring by imagewise heating of a solvent

DOEpatents

Rushford, Michael C.

2005-08-30

A method and system of imagewise etching the surface of a substrate, such as thin glass, in a parallel process. The substrate surface is placed in contact with an etchant solution which increases in etch rate with temperature. A local thermal gradient is then generated in each of a plurality of selected local regions of a boundary layer of the etchant solution to imagewise etch the substrate surface in a parallel process. In one embodiment, the local thermal gradient is a local heating gradient produced at selected addresses chosen from an indexed array of addresses. The activation of each of the selected addresses is independently controlled by a computer processor so as to imagewise etch the substrate surface at region-specific etch rates. Moreover, etching progress is preferably concurrently monitored in real time over the entire surface area by an interferometer so as to deterministically control the computer processor to image-wise figure the substrate surface where needed.

Twin-Slot Antenna-Coupled Superconducting Ti Transition-Edge Sensor at 350 GHz

NASA Astrophysics Data System (ADS)

Zhang, W.; Miao, W.; Wang, Z.; Guo, X. H.; Liu, D.; Zhong, J. Q.; Yao, Q. J.; Shi, S. C.

2018-05-01

We have developed four-leg-supported superconducting Ti transition-edge sensors (TES) formed by KOH wet etching. Energy relaxation mechanism is changed from electron-phonon coupling to diffusive phonon after wet etching. The current-voltage curves of the same TES device were measured before and after wet etching. After wet etching, its thermal conductance (G) is reduced to 500 pW/K from 8950 pW/K. The measured effective response time (τ eff) is 143 μs, about 30 times larger. In addition, we have studied the optical noise equivalent power (NEP) with a cryogenic blackbody in combination with metal-mesh filters to define the radiation bandwidth. The obtained optical NEP is 5 × 10-16 W/√Hz, which is suitable for ground-based astronomical applications.

Plasma etching of superconducting Niobium tips for scanning tunneling microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roychowdhury, A.; Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742; Dana, R.

We have developed a reproducible technique for the fabrication of sharp superconducting Nb tips for scanning tunneling microscopy (STM) and scanning tunneling spectroscopy. Sections of Nb wire with 250 μm diameter are dry etched in an SF₆ plasma in a Reactive Ion Etcher. The gas pressure, etching time, and applied power are chosen to control the ratio of isotropic to anisotropic etch rates and produce the desired tip shape. The resulting tips are atomically sharp, with radii of less than 100 nm, mechanically stable, and superconducting. They generate good STM images and spectroscopy on single crystal samples of Au(111), Au(100),more » and Nb(100), as well as a doped topological insulator Bi₂Se₃ at temperatures ranging from 30 mK to 9 K.« less

III-Nitride Blue Laser Diode with Photoelectrochemically Etched Current Aperture

NASA Astrophysics Data System (ADS)

Megalini, Ludovico

Group III-nitride is a remarkable material system to make highly efficient and high-power optoelectronics and electronic devices because of the unique electrical, physical, chemical and structural properties it offers. In particular, InGaN-based blue Laser Diodes (LDs) have been successfully employed in a variety of applications ranging from biomedical and military devices to scientific instrumentation and consumer electronics. Recently their use in highly efficient Solid State Lighting (SSL) has been proposed because of their superior beam quality and higher efficiency at high input power density. Tremendous advances in research of GaN semi-polar and non-polar crystallographic planes have led both LEDs and LDs grown on these non-basal planes to rival with, and with the promise to outperform, their equivalent c-plane counterparts. However, still many issues need to be addressed, both related to material growth and device fabrication, including a lack of conventional wet etching techniques. GaN and its alloys with InN and AlN have proven resistant essentially to all known standard wet etching techniques, and the predominant etching methods rely on chlorine-based dry etching (RIE). These introduce sub-surface damage which can degrade the electrical properties of the epitaxial structure and reduce the reliability and lifetime of the final device. Such reasons and the limited effectiveness of passivation techniques have so far suggested to etch the LD ridges before the active region, although it is well-known that this can badly affect the device performance, especially in narrow stripe width LDs, because the gain guiding obtained in the planar configuration is weak and the low index step and high lateral current leakage result in devices with threshold current density higher than devices whose ridge is etched beyond the active region. Moreover, undercut etching of III-nitride layers has proven even more challenging, with limitations in control of the lateral etch distance. In this dissertation it is presented the first nitride blue edge emitting LD with a photoelectrochemical etched current aperture (CA-LD) into the device active region. Photoelectrochemical etching (PECE) has emerged as a powerful wet etching technique for III-nitride compounds. Beyond the advantages of wet etching technique, PECE offers bandgap selectivity, which is particularly desirable because it allows more freedom in designing new and advanced devices with higher performances. In the first part of this thesis a review of PECE is presented, and it is shown how it can be used to achieve a selective and controllable deep undercut of the active region of LEDs and LDs, in particular the selective PECE of MQW active region of (10-10) m-plane and (20-2-1) plane structures is reported. In the second part of this thesis, the fabrication flow process of the CA-LD is described. The performance of these devices is compared with that of shallow etched ridge LDs with a nominally identical epitaxial structure and active region width and it is experimentally shown that the CA-LD design has superior performance. CW operation of a (20-2-1) CA-LD with a 1.5 microm wide active region is demonstrated. Finally, in the third and last part of this thesis, the CA-LD performance is discussed in more details, in particular, an analysis of optical scattering losses caused by the rough edges of the remnant PEC etched active region is presented.

Optimization and characterization of bulk hexagonal boron nitride single crystals grown by the nickel-chromium flux method

NASA Astrophysics Data System (ADS)

Hoffman, Tim

Hexagonal boron nitride (hBN) is a wide bandgap III-V semiconductor that has seen new interest due to the development of other III-V LED devices and the advent of graphene and other 2-D materials. For device applications, high quality, low defect density materials are needed. Several applications for hBN crystals are being investigated, including as a neutron detector and interference-less infrared-absorbing material. Isotopically enriched crystals were utilized for enhanced propagation of phonon modes. These applications exploit the unique physical, electronic and nanophotonics applications for bulk hBN crystals. In this study, bulk hBN crystals were grown by the flux method using a molten Ni-Cr solvent at high temperatures (1500°C) and atmospheric pressures. The effects of growth parameters, source materials, and gas environment on the crystals size, morphology and purity were established and controlled, and the reliability of the process was greatly improved. Single-crystal domains exceeding 1mm in width and 200microm in thickness were produced and transferred to handle substrates for analysis. Grain size dependence with respect to dwell temperature, cooling rate and cooling temperature were analyzed and modeled using response surface morphology. Most significantly, crystal grain width was predicted to increase linearly with dwell temperature, with single-crystal domains exceeding 2mm in at 1700°C. Isotopically enriched 10B and 11B hBN crystal were produced using a Ni-Cr-B flux method, and their properties investigated. 10B concentration was evaluated using SIMS and correlated to the shift in the Raman peak of the E2g mode. Crystals with enrichment of 99% 10B and >99% 11B were achieved, with corresponding Raman shift peaks at 1392.0 cm-1 and 1356.6 cm-1, respectively. Peak FWHM also decreased as isotopic enrichment approached 100%, with widths as low as 3.5 cm-1 achieved, compared to 8.0 cm-1 for natural abundance samples. Defect selective etching was performed using a molten NaOH-KOH etchant at 425°C-525°C, to quantify the quality of the crystals. Three etch pit shapes were identified and etch pit width was investigated as a function of temperature. Etch pit density and etch pit activation energy was estimated at 5x107 cm-2 and 60 kJ/mol, respectively. Screw and mixed-type dislocations were identified using diffraction-contrast TEM imaging.

Composition/bandgap selective dry photochemical etching of semiconductor materials

DOEpatents

Ashby, C.I.H.; Dishman, J.L.

1985-10-11

Disclosed is a method of selectively photochemically dry etching a first semiconductor material of a given composition and direct bandgap Eg/sub 1/ in the presence of a second semiconductor material of a different composition and direct bandgap Eg/sub 2/, wherein Eg/sub 2/ > Eg/sub 1/, said second semiconductor material substantially not being etched during said method. The method comprises subjecting both materials to the same photon flux and to the same gaseous etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said photons being of an energy greater than Eg/sub 1/ but less than Eg/sub 2/, whereby said first semiconductor material is photochemically etched and said second material is substantially not etched.

Effect of Selectively Etched Ferroelectric Thin-Film Layer on the Performance of a Tunable Bandpass Filter

NASA Technical Reports Server (NTRS)

Subramanyam, Guru; Vignesparamoorthy, Sivaruban; Mueller, Carl; VanKeuls, Fred; Warner, Joseph; Miranda, Felix A.

2001-01-01

The main purpose of this work is to study the effect of a selectively etched ferroelectric thin film layer on the performance of an electrically tunable filter. An X-band tunable filter was designed, fabricated and tested on a selectively etched Barium Strontium Titanate (BSTO) ferroelectric thin film layer. Tunable filters with varying lengths of BSTO thin-film in the input and output coupling gaps were modeled, as well as experimentally tested. Experimental results showed that filters with coupling gaps partially filled with BSTO maintained frequency tunability and improved the insertion loss by approx. 2dB. To the best of our knowledge, these results represent the first experimental demonstration of the advantages of selective etching in the performance of thin film ferroelectric-based tunable microwave components.

Direct comparison of the performance of commonly used e-beam resists during nano-scale plasma etching of Si, SiO2, and Cr

NASA Astrophysics Data System (ADS)

Goodyear, Andy; Boettcher, Monika; Stolberg, Ines; Cooke, Mike

2015-03-01

Electron beam writing remains one of the reference pattern generation techniques, and plasma etching continues to underpin pattern transfer. We report a systematic study of the plasma etch resistance of several e-beam resists, both negative and positive as well as classical and Chemically Amplified Resists: HSQ[1,2] (Dow Corning), PMMA[3] (Allresist GmbH), AR-P6200 (Allresist GmbH), ZEP520 (Zeon Corporation), CAN028 (TOK), CAP164 (TOK), and an additional pCAR (non-disclosed provider). Their behaviour under plasma exposure to various nano-scale plasma etch chemistries was examined (SF6/C4F8 ICP silicon etch, CHF3/Ar RIE SiO2 etch, Cl2/O2 RIE and ICP chrome etch, and HBr ICP silicon etch). Samples of each resist type were etched simultaneously to provide a direct comparison of their etch resistance. Resist thicknesses (and hence resist erosion rates) were measured by spectroscopic ellipsometer in order to provide the highest accuracy for the resist comparison. Etch selectivities (substrate:mask etch rate ratio) are given, with recommendations for the optimum resist choice for each type of etch chemistry. Silicon etch profiles are also presented, along with the exposure and etch conditions to obtain the most vertical nano-scale pattern transfer. We identify one resist that gave an unusually high selectivity for chlorinated and brominated etches which could enable pattern transfer below 10nm without an additional hard mask. In this case the resist itself acts as a hard mask. We also highlight the differing effects of fluorine and bromine-based Silicon etch chemistries on resist profile evolution and hence etch fidelity.

Infrared Photodiodes Made by Low Energy Ion Etching of Molecular Beam Epitaxy Grown Mercury-Cadmium Alloy

NASA Astrophysics Data System (ADS)

Yoo, Sung-Shik

Ion etching was used to form junctions on the p-type (111)B Hg_{1-x}Cd_ {x}Te grown by Molecular Beam Epitaxy(MBE). When Hg_{1-x}Cd_{x}Te layers are etched by Ar ions at energies ranging between 300 and 450eV, the top Hg_{1 -x}Cd_{x}Te layer is converted to n-type. The converted region is electrically characterized as a defective n^+-region near the surface, and a low doped n^--region exist below the damaged region. The total thickness of the converted n-type layer was found to be considerable. These results suggest that the creation of the n-type layer is due to the filling of mercury vacancies by mercury atoms displaced by the Ar ion irradiation on the surface. For the performance of the resulting photodiodes on MBE grown (111)B Hg_{1-x}Cd _{x}Te using this technique, the dynamic resistances at 80K are one order of magnitude less than those of junctions made on Liquid Phase Epitaxially and Bulk grown Hg_{1 -x}Cd_{x}Te. The ion etching technique was compared with ion implantation technique by fabricating diodes on the same MBE grown (111)B Hg _{1-x}Cd_{x}Te layers. The result of the comparison illustrates that ion etching technique is as good as ion implantation technique for the fabrication of Hg_{1-x}Cd _{x}Te photodiodes. Also it is believed that the performance of the diodes is limited by a relatively large density of twin defects usually found in MBE grown (111)B Hg_{1-x}Cd _{x}Te.

193-nm multilayer imaging systems

NASA Astrophysics Data System (ADS)

Meador, James D.; Holmes, Doug; DiMenna, William; Nagatkina, Mariya I.; Rich, Michael D.; Flaim, Tony D.; Bennett, Randy; Kobayashi, Ichiro

2003-06-01

This paper highlights the performance of new materials that have been developed for use in 193-nm trilayer microlithography. The products are embedded etch masking layers (EMLs) and bottom antireflective coatings (BARCs). Both coatings are spin applied from organic solvent(s) and then thermoset during a hot plate bake. The EMLs (middle layers) are imaging compatible with JSR, Sumitomo, and TOK 193-nm photoresists. Best-case trilayer film stacks have given 100-nm dense and semi-dense L/S. Plasma etching, selectivities and solution compatibility performance of the EMLs meet or exceed proposed product targets. In addition, the EMLs exhibit both solution and plasma etching properties that should lead to successful rework processes for photoresists. The multiplayer BARCs offer good thick film coating quality and contribute to excellent images when used in trilayer applications. Combining the EMLs, which are nearly optically transparent (k=0.04) at 193-nm, with the new trilayer BARCs results in outstanding Prolith simulated reflectance control. In one modeling example, reflectance is a flat line at 0.5% on five different substrates for BARC thicknesses between 300 and 700-nm.

Very low temperature (450 °C) selective epitaxial growth of heavily in situ boron-doped SiGe layers

NASA Astrophysics Data System (ADS)

Aubin, J.; Hartmann, J. M.; Veillerot, M.; Essa, Z.; Sermage, B.

2015-11-01

We have investigated the feasibility of selectively growing SiGe:B layers at 450 °C, 20 Torr in a 300 mm industrial reduced pressure chemical vapor deposition tool. A reduced H2 carrier gas mass-flow has been used in order to have acceptable growth rates at such a temperature, which is very low indeed. We have first of all studied on blanket Si wafers the in situ boron doping of SiGe with Si2H6, GeH4 and B2H6. A growth rate increase by a factor close to 7 together with a Ge concentration decrease from 53% down to 32% occurred as the diborane mass-flow increased. Very high B+ ion concentrations were obtained in layers that were single crystalline and smooth. Their concentration increased almost linearly with the B2H6 mass-flow, from 1.8 up to 8.3 × 1020 cm-3. The associated resistivity dropped from 0.43 down to 0.26 mΩ cm. We have then tested whether or not selectivity versus SiO2 could be achieved by adding various amounts of HCl to Si2H6 + GeH4 +B2H6. Single crystalline growth rates of intrinsic SiGe(:B) on Si were very similar to poly-crystalline growth rates on SiO2-covered substrates irrespective of the HCl flow. Straightforward selectivity was thus not feasible with a co-flow approach. As a consequence, a 450 °C deposition/etch (DE) process was evaluated. Growth occurred at 20 Torr with the above-mentioned chemistry, while the selective etch of poly-SiGe:B versus c-SiGe:B was conducted at 740 Torr with a medium HCl mass-flow (F(HCl)/F(H2) = 0.2) and a high H2 flow. A 2.2 etch selectivity was achieved while retaining single crystalline if slightly rough SiGe:B layers.

Selective Etching of Silicon in Preference to Germanium and Si0.5Ge0.5.

PubMed

Ahles, Christopher F; Choi, Jong Youn; Wolf, Steven; Kummel, Andrew C

2017-06-21

The selective etching characteristics of silicon, germanium, and Si 0.5 Ge 0.5 subjected to a downstream H 2 /CF 4 /Ar plasma have been studied using a pair of in situ quartz crystal microbalances (QCMs) and X-ray photoelectron spectroscopy (XPS). At 50 °C and 760 mTorr, Si can be etched in preference to Ge and Si 0.5 Ge 0.5 , with an essentially infinite Si/Ge etch-rate ratio (ERR), whereas for Si/Si 0.5 Ge 0.5 , the ERR is infinite at 22 °C and 760 mTorr. XPS data showed that the selectivity is due to the differential suppression of etching by a ∼2 ML thick C x H y F z layer formed by the H 2 /CF 4 /Ar plasma on Si, Ge, and Si 0.5 Ge 0.5 . The data are consistent with the less exothermic reaction of fluorine radicals with Ge or Si 0.5 Ge 0.5 being strongly suppressed by the C x H y F z layer, whereas, on Si, the C x H y F z layer is not sufficient to completely suppress etching. Replacing H 2 with D 2 in the feed gas resulted in an inverse kinetic isotope effect (IKIE) where the Si and Si 0.5 Ge 0.5 etch rates were increased by ∼30 times with retention of significant etch selectivity. The use of D 2 /CF 4 /Ar instead of H 2 /CF 4 /Ar resulted in less total carbon deposition on Si and Si 0.5 Ge 0.5 and gave less Ge enrichment of Si 0.5 Ge 0.5 . These results are consistent with the selectivity being due to the differential suppression of etching by an angstrom-scale carbon layer.

TOPICAL REVIEW: Black silicon method X: a review on high speed and selective plasma etching of silicon with profile control: an in-depth comparison between Bosch and cryostat DRIE processes as a roadmap to next generation equipment

NASA Astrophysics Data System (ADS)

Jansen, H V; de Boer, M J; Unnikrishnan, S; Louwerse, M C; Elwenspoek, M C

2009-03-01

An intensive study has been performed to understand and tune deep reactive ion etch (DRIE) processes for optimum results with respect to the silicon etch rate, etch profile and mask etch selectivity (in order of priority) using state-of-the-art dual power source DRIE equipment. The research compares pulsed-mode DRIE processes (e.g. Bosch technique) and mixed-mode DRIE processes (e.g. cryostat technique). In both techniques, an inhibitor is added to fluorine-based plasma to achieve directional etching, which is formed out of an oxide-forming (O2) or a fluorocarbon (FC) gas (C4F8 or CHF3). The inhibitor can be introduced together with the etch gas, which is named a mixed-mode DRIE process, or the inhibitor can be added in a time-multiplexed manner, which will be termed a pulsed-mode DRIE process. Next, the most convenient mode of operation found in this study is highlighted including some remarks to ensure proper etching (i.e. step synchronization in pulsed-mode operation and heat control of the wafer). First of all, for the fabrication of directional profiles, pulsed-mode DRIE is far easier to handle, is more robust with respect to the pattern layout and has the potential of achieving much higher mask etch selectivity, whereas in a mixed-mode the etch rate is higher and sidewall scalloping is prohibited. It is found that both pulsed-mode CHF3 and C4F8 are perfectly suited to perform high speed directional etching, although they have the drawback of leaving the FC residue at the sidewalls of etched structures. They show an identical result when the flow of CHF3 is roughly 30 times the flow of C4F8, and the amount of gas needed for a comparable result decreases rapidly while lowering the temperature from room down to cryogenic (and increasing the etch rate). Moreover, lowering the temperature lowers the mask erosion rate substantially (and so the mask selectivity improves). The pulsed-mode O2 is FC-free but shows only tolerable anisotropic results at -120 °C. The downside of needing liquid nitrogen to perform cryogenic etching can be improved by using a new approach in which both the pulsed and mixed modes are combined into the so-called puffed mode. Alternatively, the use of tetra-ethyl-ortho-silicate (TEOS) as a silicon oxide precursor is proposed to enable sufficient inhibiting strength and improved profile control up to room temperature. Pulsed-mode processing, the second important aspect, is commonly performed in a cycle using two separate steps: etch and deposition. Sometimes, a three-step cycle is adopted using a separate step to clean the bottom of etching features. This study highlights an issue, known by the authors but not discussed before in the literature: the need for proper synchronization between gas and bias pulses to explore the benefit of three steps. The transport of gas from the mass flow controller towards the wafer takes time, whereas the application of bias to the wafer is relatively instantaneous. This delay causes a problem with respect to synchronization when decreasing the step time towards a value close to the gas residence time. It is proposed to upgrade the software with a delay time module for the bias pulses to be in pace with the gas pulses. If properly designed, the delay module makes it possible to switch on the bias exactly during the arrival of the gas for the bottom removal step and so it will minimize the ionic impact because now etch and deposition steps can be performed virtually without bias. This will increase the mask etch selectivity and lower the heat impact significantly. Moreover, the extra bottom removal step can be performed at (also synchronized!) low pressure and therefore opens a window for improved aspect ratios. The temperature control of the wafer, a third aspect of this study, at a higher etch rate and longer etch time, needs critical attention, because it drastically limits the DRIE performance. It is stressed that the exothermic reaction (high silicon loading) and ionic impact (due to metallic masks and/or exposed silicon) are the main sources of heat that might raise the wafer temperature uncontrollably, and they show the weakness of the helium backside technique using mechanical clamping. Electrostatic clamping, an alternative technique, should minimize this problem because it is less susceptible to heat transfer when its thermal resistance and the gap of the helium backside cavity are minimized; however, it is not a subject of the current study. Because oxygen-growth-based etch processes (due to their ultra thin inhibiting layer) rely more heavily on a constant wafer temperature than fluorocarbon-based processes, oxygen etches are more affected by temperature fluctuations and drifts during the etching. The fourth outcome of this review is a phenomenological model, which explains and predicts many features with respect to loading, flow and pressure behaviour in DRIE equipment including a diffusion zone. The model is a reshape of the flow model constructed by Mogab, who studied the loading effect in plasma etching. Despite the downside of needing a cryostat, it is shown that—when selecting proper conditions—a cryogenic two-step pulsed mode can be used as a successful technique to achieve high speed and selective plasma etching with an etch rate around 25 µm min-1 (<1% silicon load) with nearly vertical walls and resist etch selectivity beyond 1000. With the model in hand, it can be predicted that the etch rate can be doubled (50 µm min-1 at an efficiency of 33% for the fluorine generation from the SF6 feed gas) by minimizing the time the free radicals need to pass the diffusion zone. It is anticipated that this residence time can be reduced sufficiently by a proper inductive coupled plasma (ICP) source design (e.g. plasma shower head and concentrator). In order to preserve the correct profile at such high etch rates, the pressure during the bottom removal step should be minimized and, therefore, the synchronized three-step pulsed mode is believed to be essential to reach such high etch rates with sufficient profile control. In order to improve the etch rate even further, the ICP power should be enhanced; the upgrading of the turbopump seems not yet to be relevant because the throttle valve in the current study had to be used to restrict the turbo efficiency. In order to have a versatile list of state-of-the-art references, it has been decided to arrange it in subjects. The categories concerning plasma physics and applications are, for example, books, reviews, general topics, fluorine-based plasmas, plasma mixtures with oxygen at room temperature, wafer heat transfer and high aspect ratio trench (HART) etching. For readers 'new' to this field, it is advisable to study at least one (but rather more than one) of the reviews concerning plasma as found in the first 30 references. In many cases, a paper can be classified into more than one category. In such cases, the paper is directed to the subject most suited for the discussion of the current review. For example, many papers on heat transfer also treat cryogenic conditions and all the references dealing with highly anisotropic behaviour have been directed to the category HARTs. Additional pointers could get around this problem but have the disadvantage of creating a kind of written spaghetti. I hope that the adapted organization structure will help to have a quick look at and understanding of current developments in high aspect ratio plasma etching. Enjoy reading... Henri Jansen 18 June 2008

A benchmark of co-flow and cyclic deposition/etch approaches for the selective epitaxial growth of tensile-strained Si:P

NASA Astrophysics Data System (ADS)

Hartmann, J. M.; Veillerot, M.; Prévitali, B.

2017-10-01

We have compared co-flow and cyclic deposition/etch processes for the selective epitaxial growth of Si:P layers. High growth rates, relatively low resistivities and significant amounts of tensile strain (up to 10 nm min-1, 0.55 mOhm cm and a strain equivalent to 1.06% of substitutional C in Si:C layers) were obtained at 700 °C, 760 Torr with a co-flow approach and a SiH2Cl2 + PH3 + HCl chemistry. This approach was successfully used to thicken the sources and drains regions of n-type fin-shaped Field Effect Transistors. Meanwhile, the (Si2H6 + PH3/HCl + GeH4) CDE process evaluated yielded at 600 °C, 80 Torr even lower resistivities (0.4 mOhm cm, typically), at the cost however of the tensile strain which was lost due to (i) the incorporation of Ge atoms (1.5%, typically) into the lattice during the selective etch steps and (ii) a reduction by a factor of two of the P atomic concentration in CDE layers compared to that in layers grown in a single step (5 × 1020 cm-3 compared to 1021 cm-3).

Catalytically-etched hexagonal boron nitride flakes and their surface activity

NASA Astrophysics Data System (ADS)

Kim, Do-Hyun; Lee, Minwoo; Ye, Bora; Jang, Ho-Kyun; Kim, Gyu Tae; Lee, Dong-Jin; Kim, Eok-Soo; Kim, Hong Dae

2017-04-01

Hexagonal boron nitride (h-BN) is a ceramic compound which is thermally stable up to 1000 °C in air. Due to this, it is a very challenging task to etch h-BN under air atmosphere at low temperature. In this study, we report that h-BN flakes can be easily etched by oxidation at 350 °C under air atmosphere in the presence of transition metal (TM) oxide. After selecting Co, Cu, and Zn elements as TM precursors, we simply oxidized h-BN sheets impregnated with the TM precursors at 350 °C in air. As a result, microscopic analysis revealed that an etched structure was created on the surface of h-BN flakes regardless of catalyst type. And, X-ray diffraction patterns indicated that the air oxidation led to the formation of Co3O4, CuO, and ZnO from each precursor. Thermogravimetric analysis showed a gradual weight loss in the temperature range where the weight of h-BN flakes increased by air oxidation. As a result of etching, pore volume and pore area of h-BN flakes were increased after catalytic oxidation in all cases. In addition, the surface of h-BN flakes became highly active when the h-BN samples were etched by Co3O4 and CuO catalysts. Based on these results, we report that h-BN flakes can be easily oxidized in the presence of a catalyst, resulting in an etched structure in the layered structure.

Ion beam enhanced etching of LiNbO 3

NASA Astrophysics Data System (ADS)

Schrempel, F.; Gischkat, Th.; Hartung, H.; Kley, E.-B.; Wesch, W.

2006-09-01

Single crystals of z- and x-cut LiNbO 3 were irradiated at room temperature and 15 K using He +- and Ar +-ions with energies of 40 and 350 keV and ion fluences between 5 × 10 12 and 5 × 10 16 cm -2. The damage formation investigated with Rutherford backscattering spectrometry (RBS) channeling analysis depends on the irradiation temperature as well as the ion species. For instance, He +-irradiation of z-cut material at 300 K provokes complete amorphization at 2.0 dpa (displacements per target atom). In contrast, 0.4 dpa is sufficient to amorphize the LiNbO 3 in the case of Ar +-irradiation. Irradiation at 15 K reduces the number of displacements per atom necessary for amorphization. To study the etching behavior, 400 nm thick amorphous layers were generated via multiple irradiation with He +- and Ar +-ions of different energies and fluences. Etching was performed in a 3.6% hydrofluoric (HF) solution at 40 °C. Although the etching rate of the perfect crystal is negligible, that of the amorphized regions amounts to 80 nm min -1. The influence of the ion species, the fluence, the irradiation temperature and subsequent thermal treatment on damage and etching of LiNbO 3 are discussed.

Optical fiber sensor for low dose gamma irradiation monitoring

NASA Astrophysics Data System (ADS)

de Andrés, Ana I.; Esteban, Ã.`scar; Embid, Miguel

2016-05-01

An optical fiber gamma ray detector is presented in this work. It is based on a Terbium doped Gadolinium Oxysulfide (Gd2O2S:Tb) scintillating powder which cover a chemically etched polymer fiber tip. This etching improves the fluorescence gathering by the optical fiber. The final diameter has been selected to fulfill the trade-off between light gathering and mechanical strength. Powder has been encapsulated inside a microtube where the fiber tip is immersed. The sensor has been irradiated with different air Kerma doses up to 2 Gy/h with a 137Cs source, and the spectral distribution of the fluorescence intensity has been recorded in a commercial grade CCD spectrometer. The obtained signal-to-noise ratio is good enough even for low doses, which has allowed to reduce the integration time in the spectrometer. The presented results show the feasibility for using low cost equipment to detect/measure ionizing radiation as gamma rays are.

Formation of nanogaps in InAs nanowires by selectively etching embedded InP segments.

PubMed

Schukfeh, M I; Storm, K; Hansen, A; Thelander, C; Hinze, P; Beyer, A; Weimann, T; Samuelson, L; Tornow, M

2014-11-21

We present a method to fabricate nanometer scale gaps within InAs nanowires by selectively etching InAs/InP heterostructure nanowires. We used vapor-liquid-solid grown InAs nanowires with embedded InP segments of 10-60 nm length and developed an etching recipe to selectively remove the InP segment. A photo-assisted wet etching process in a mixture of acetic acid and hydrobromic acid gave high selectivity, with accurate removal of InP segments down to 20 nm, leaving the InAs wire largely unattacked, as verified using scanning electron and transmission electron microscopy. The obtained nanogaps in InAs wires have potential as semiconducting electrodes to investigate electronic transport in nanoscale objects. We demonstrate this functionality by dielectrophoretically trapping 30 nm diameter gold nanoparticles into the gap.

Cross-plane thermoelectric transport in p-type La0.67Sr0.33MnO3/LaMnO3 oxide metal/semiconductor superlattices

NASA Astrophysics Data System (ADS)

Jha, Pankaj; Sands, Timothy D.; Jackson, Philip; Bomberger, Cory; Favaloro, Tela; Hodson, Stephen; Zide, Joshua; Xu, Xianfan; Shakouri, Ali

2013-05-01

The cross-plane thermoelectric transport properties of La0.67Sr0.33MnO3 (LSMO)/LaMnO3 (LMO) oxide metal/semiconductor superlattices were investigated. The LSMO and LMO thin-film depositions were performed using pulsed laser deposition to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate substrates. X-ray diffraction and high-resolution reciprocal space mapping indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively, this coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal a lowering of the effective barrier height to 223 meV as well as an increase in cross-plane conductivity by an order of magnitude compared to high resistivity superlattices. These results suggest that controlling the oxygen deficiency in the constituent materials enables modification of the effective barrier height and increases the cross-plane conductivity in oxide superlattices. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 μV/K at 300 K that increases to 16 640 μV/K at 360 K. The giant increase in the Seebeck coefficient with temperature may include a collective contribution from the interplay of charge, spin current, and phonon drag. The low resistance oxide superlattices exhibited a room temperature cross-plane thermal conductivity of 0.92 W/m K, this indicating that the suppression of thermal conductivities due to the interfaces is preserved in both low and high resistivity superlattices. The high Seebeck coefficient, the order of magnitude improvement in cross-plane conductivity, and the low thermal conductivity in LSMO/LMO superlattices resulted in a two order of magnitude increase in cross-plane power factor and thermoelectric figure of merit (ZT), compared to the properties of superlattices with higher resistivity that were reported previously. The temperature dependence of the cross-plane power factor in low resistance superlattices suggests a direction for further investigations of the potential LSMO/LMO oxide superlattices for thermoelectric devices.

Effect of nonsinusoidal bias waveforms on ion energy distributions and fluorocarbon plasma etch selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarwal, Ankur; Kushner, Mark J.; Iowa State University, Department of Electrical and Computer Engineering, 104 Marston Hall, Ames, Iowa 50011-2151

2005-09-15

The distributions of ion energies incident on the wafer significantly influence feature profiles and selectivity during plasma etching. Control of ion energies is typically obtained by varying the amplitude or frequency of a radio frequency sinusoidal bias voltage applied to the substrate. The resulting ion energy distribution (IED), though, is generally broad. Controlling the width and shape of the IED can potentially improve etch selectivity by distinguishing between threshold energies of surface processes. In this article, control of the IED was computationally investigated by applying a tailored, nonsinusoidal bias waveform to the substrate of an inductively coupled plasma. The waveformmore » we investigated, a quasi-dc negative bias having a short positive pulse each cycle, produced a narrow IED whose width was controllable based on the length of the positive spike and frequency. We found that the selectivity between etching Si and SiO{sub 2} in fluorocarbon plasmas could be controlled by adjusting the width and energy of the IED. Control of the energy of a narrow IED enables etching recipes that transition between speed and selectivity without change of gas mixture.« less

Design and fabrication of low power GaAs/AlAs resonant tunneling diodes

NASA Astrophysics Data System (ADS)

Md Zawawi, Mohamad Adzhar; Missous, Mohamed

2017-12-01

A very low peak voltage GaAs/AlAs resonant tunneling diode (RTD) grown by molecular beam epitaxy (MBE) has been studied in detail. Excellent growth control with atomic-layer precision resulted in a peak voltage of merely 0.28 V (0.53 V) in forward (reverse) direction. The peak current density in forward bias is around 15.4 kA/cm2 with variation of within 7%. As for reverse bias, the peak current density is around 22.8 kA/cm2 with 4% variation which implies excellent scalability. In this work, we have successfully demonstrated the fabrication of a GaAs/AlAs RTD by using a conventional optical lithography and chemical wet-etching with very low peak voltage suitable for application in low dc input power RTD-based sub-millimetre wave oscillators.

Laser generation in microdisc resonators with InAs/GaAs quantum dots transferred on a silicon substrate

NASA Astrophysics Data System (ADS)

Nadtochiy, A. M.; Kryzhanovskaya, N. V.; Maximov, M. V.; Zhukov, A. E.; Moiseev, E. I.; Kulagina, M. M.; Vashanova, K. A.; Zadiranov, Yu. M.; Mukhin, I. S.; Arakcheeva, E. M.; Livshits, D.; Lipovskii, A. A.

2013-09-01

Microdisc resonators based on InAs/GaAs quantum dots separated from a GaAs substrate by selective etching and fixed to a silicon substrate by epoxy glue are studied using luminescence spectroscopy. A disc resonator 6 μm in diameter exhibits quasi-single-mode laser generation at a temperature of 78 K with a threshold power of 320 μW and λ/Δλ ˜ 27000.

Investigation of Cutting Quality of Remote DOE Laser Cutting in 0.5 mm Stainless Steel

NASA Astrophysics Data System (ADS)

Villumsen, Sigurd Lazic; Kristiansen, Morten

It has previously been shown that the stability of the remote fusion cutting (RFC) process can be increased by modifying the intensity profile of the laser by means of a diffractive optical element (DOE). This paper investigates the quality of remote DOE cutting (RDC) conducted with a 3 kW single mode fiber laser in 0.5 mm stainless steel. An automatic measurement system is used to investigate how the travel speed, focus offset and angle of incidence effect the kerf width and kerf variance. The study shows that the RDC process has a very low kerf width variance, and that the kerf width decreases with cutting speed. Furthermore, selected etched samples show a significant increase in the perpendicularity of the cuts when compared to RFC. Also, on average, the depth of the layer of molten material for RFC is 83% deeper than for RDC.

Method for the preparation of inorganic single crystal and polycrystalline electronic materials

NASA Technical Reports Server (NTRS)

Groves, W. O. (Inventor)

1969-01-01

Large area, semiconductor crystals selected from group 3-5 compounds and alloys are provided for semiconductor device fabrication by the use of a selective etching operation which completely removes the substrate on which the desired crystal was deposited. The substrate, selected from the same group as the single crystal, has a higher solution rate than the epitaxial single crystal which is essentially unaffected by the etching solution. The preparation of gallium phosphide single crystals using a gallium arsenide substrate and a concentrated nitric acid etching solution is described.

A high-performance nanoporous Si/Al2O3 foam lithium-ion battery anode fabricated by selective chemical etching of the Al-Si alloy and subsequent thermal oxidation.

PubMed

Hwang, Gaeun; Park, Hyungmin; Bok, Taesoo; Choi, Sinho; Lee, Sungjun; Hwang, Inchan; Choi, Nam-Soon; Seo, Kwanyong; Park, Soojin

2015-03-14

Nanostructured micrometer-sized Al-Si particles are synthesized via a facile selective etching process of Al-Si alloy powder. Subsequent thin Al2O3 layers are introduced on the Si foam surface via a selective thermal wet oxidation process of etched Al-Si particles. The resulting Si/Al2O3 foam anodes exhibit outstanding cycling stability (a capacity retention of 78% after 300 cycles at the C/5 rate) and excellent rate capability.

Material growth and characterization for solid state devices

NASA Technical Reports Server (NTRS)

Collis, Ward J.; Abul-Fadl, Ali; Iyer, Shanthi

1988-01-01

During the period of this research grant, the process of liquid phase electroepitaxy (LPEE) was used to grow ternary and quaternary alloy III-V semiconductor thin films. Selective area growth of InGaAs was performed on InP substrates using a patterned sputtered quartz or spin-on glass layer. The etch back and growth characteristics with respect to substrate orientation were investigated. The etch back behavior is somewhat different from wet chemical etching with respect to the sidewall profiles which are observed. LPEE was also employed to grow epitaxial layers of InGaAsP alloys on InP substrates. The behavior of Mn as an acceptor dopant was investigated with low temperature Hall coefficient and photoluminescence measurements. A metal-organic vapor phase epitaxy system was partially complete within the grant period. This atmospheric pressure system will be used to deposit III-V compound and alloy semiconductor layers in future research efforts.

Anisotropic etching of silicon in solutions containing tensioactive compounds

NASA Astrophysics Data System (ADS)

Zubel, Irena

2016-12-01

The results of investigations concerning anisotropic etching in 3M KOH and 25% TMAH solutions modified by tensioactive compounds such as alcohols, diols and a typical surfactant Triton X100 have been compared. Etching anisotropy was assessed on the basis of etch rates ratio V(110)/V(100). It was stated that the relation between surface tension of the solutions and etch rates of particular planes depend not only on the kind of surfactant but also on the kind of etching solution (KOH, TMAH). It points out an important role of TMA+ ions in the etching process, probably in the process of forming an adsorption layer, consisting of the molecules of tensioactive compounds on Si surface, which decides about etch rate. We have observed that this phenomenon occurs only at high concentration of TMA+ ions (25% TMAH). Reduction of TMAH concentration changes the properties of surfactant containing TMAH solutions. From all investigated solutions, the solutions that assured developing of (110) plane inclined at the angle of 45° to (100) substrate were selected. Such planes can be used as micromirrors in MOEMS structures. The solutions provide the etch rate ratio V(110)/V(100)<0.7, thus they were selected from hydroxide solutions containing surfactants. A simple way for etch rate anisotropy V(110)/V(100) assessment based on microscopic images etched structures has been proposed.

Isotropic plasma etching of Ge Si and SiN x films

DOE PAGES

Henry, Michael David; Douglas, Erica Ann

2016-08-31

This study reports on selective isotropic dry etching of chemically vapor deposited (CVD) Ge thin film, release layers using a Shibaura chemical downstream etcher (CDE) with NF 3 and Ar based plasma chemistry. Relative etch rates between Ge, Si and SiN x are described with etch rate reductions achieved by adjusting plasma chemistry with O 2. Formation of oxides reducing etch rates were measured for both Ge and Si, but nitrides or oxy-nitrides created using direct injection of NO into the process chamber were measured to increase Si and SiN x etch rates while retarding Ge etching.

Low-loss, submicron chalcogenide integrated photonics with chlorine plasma etching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiles, Jeff; Malinowski, Marcin; Rao, Ashutosh

A chlorine plasma etching-based method for the fabrication of high-performance chalcogenide-based integrated photonics on silicon substrates is presented. By optimizing the etching conditions, chlorine plasma is employed to produce extremely low-roughness etched sidewalls on waveguides with minimal penalty to propagation loss. Using this fabrication method, microring resonators with record-high intrinsic Q-factors as high as 450 000 and a corresponding propagation loss as low as 0.42 dB/cm are demonstrated in submicron chalcogenide waveguides. Furthermore, the developed chlorine plasma etching process is utilized to demonstrate fiber-to-waveguide grating couplers in chalcogenide photonics with high power coupling efficiency of 37% for transverse-electric polarized modes.

Semiconductor etching by hyperthermal neutral beams

NASA Technical Reports Server (NTRS)

Minton, Timothy K. (Inventor); Giapis, Konstantinos P. (Inventor)

1999-01-01

An at-least dual chamber apparatus and method in which high flux beams of fast moving neutral reactive species are created, collimated and used to etch semiconductor or metal materials from the surface of a workpiece. Beams including halogen atoms are preferably used to achieve anisotropic etching with good selectivity at satisfactory etch rates. Surface damage and undercutting are minimized.

In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays.

PubMed

Kim, Yong Hee; Kim, Gook Hwa; Kim, Ah Young; Han, Young Hwan; Chung, Myung-Ae; Jung, Sang-Don

2015-12-01

Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm(-2), which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays

NASA Astrophysics Data System (ADS)

Kim, Yong Hee; Kim, Gook Hwa; Kim, Ah Young; Han, Young Hwan; Chung, Myung-Ae; Jung, Sang-Don

2015-12-01

Objective. Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. Approach. Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. Main results. The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm-2, which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. Significance. Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

Design, modeling, and fabrication of crab-shape capacitive microphone using silicon-on-isolator wafer

NASA Astrophysics Data System (ADS)

Ganji, Bahram Azizollah; Sedaghat, Sedighe Babaei; Roncaglia, Alberto; Belsito, Luca; Ansari, Reza

2018-01-01

This paper presents design, modeling, and fabrication of a crab-shape microphone using silicon-on-isolator (SOI) wafer. SOI wafer is used to prevent the additional deposition of sacrificial and diaphragm layers. The holes have been made on diaphragm to prevent back plate etching. Dry etching is used for removing the sacrificial layer, because wet etching causes adhesion between the diaphragm and the back plate. Crab legs around the perforated diaphragm allow for improving the microphone performance and reducing the mechanical stiffness and air damping of the microphone. In this structure, the supply voltage is decreased due to the uniform deflection of the diaphragm due to the designed low-K (spring constant) structure. An analytical model of the structure for description of microphone behavior is presented. The proposed method for estimating the basic parameters of the microphone is based on the calculation of the spring constant using the energy method. The microphone is fabricated using only one mask to pattern the crab-shape diaphragm, resulting in a low-cost and easy fabrication process. The diaphragm size is 0.3 mm×0.3 mm, which is smaller than the conventional microelectromechanical systems capacitive microphone. The results show that the analytical equations have a good agreement with measurement results. The device has the pull-in voltage of 14.3 V, a resonant frequency of 90 kHz, an open-circuit sensitivity of 1.33 mV/Pa under bias voltage of 5 V. Comparing with previous works, this microphone has several advantages: SOI wafer decreases the fabrication process steps, the microphone is smaller than the previous works, and crab-shape diaphragm improves the microphone performances.

The effect of SEM imaging on the Ar/Ar system in feldspars

NASA Astrophysics Data System (ADS)

Flude, S.; Sherlock, S.; Lee, M.; Kelley, S. P.

2010-12-01

Complex microtextures form in K-feldspar crystals as they cool and are affected by deuteric alteration. This complex structure is the cause of variable closure temperatures for Ar-Ar, a phenomenon which has been utilized in multi domain diffusion (MDD) modelling to recover thermal histories [1]. However, there has been substantial controversy regarding the precise interaction between feldspar microtextures and Ar-diffusion [2,3]. A number of studies have addressed this issue using coupled SEM imaging and Ar/Ar UV laser ablation microprobe (UV-LAMP) analysis on the same sample, to enable direct comparison of microtextures with Ar/Ar age data [4]. Here we have tested the idea that SEM work may affect Ar/Ar ages, leading to inaccurate results in subsequent Ar/Ar analyses. Three splits of alkali feldspar from the Dartmoor Granite in SW England were selected for Ar/Ar UV-LAMP analysis. Split 1 (“control”) was prepared as a polished thick section for Ar/Ar analysis. Split 2 (“SEM”) was prepared as a polished thick section, was chemically-mechanically polished with colloidal silica and underwent SEM imaging (uncoated) and focussed ion beam (FIB) milling (gold coated); electron beam damage in the SEM was maximised by leaving the sample at high magnification for eight minutes. Split 3 (“Etch”) is a cleavage fragment that was etched with HF vapour and underwent low to moderate magnification SEM imaging. The control split gave a range of laser-spot ages consistent with the expected cooling age of the granite and high yields of radiogenic 40Ar* (>90%). The area of the “SEM” split that experienced significant electron beam damage gave younger than expected ages and 40Ar* yields as low as 57%. These are interpreted as a combination of implantation of atmospheric Ar and local redistribution of K within the sample. The area of “SEM” that underwent FIB milling gave ages and 40Ar* yields comparable to the control split, suggesting that the Au-coat minimises FIB damage and that colloidal-polishing and low-magnification SEM imaging do not affect the Ar/Ar system. The “Etch” split gave younger than expected ages and 40Ar* yields as low as 58%, suggesting that HF etching also disrupts the Ar/Ar system. These results suggest that SEM techniques involving intense electron bombardment of an uncoated sample, such as charge contrast imaging and electron backscatter diffraction (EBSD), may disrupt the Ar/Ar system in the sample, leading to spurious results. Etching samples with HF, as is often done for routine Ar/Ar preparation of volcanic phenocrysts, introduces atmospheric Ar and may result in differential loss or gain of K and Ar isotopes, leading to spurious results. References [1] Lovera and Richter, 1989, J. Geophys. Res. 94, 17917-17935. [2] Parsons. et al., 1999, Cont. Min. Pet. 136, 92-110. [3] Mark et al., 2008, Geochim. Cosmochim. Acta, 72 2695-2710. [4] Reddy et al., 2001, Cont. Min. Pet., 141 186-200.

A thickness-mode piezoelectric micromachined ultrasound transducer annular array using a PMN–PZT single crystal

NASA Astrophysics Data System (ADS)

Kang, Woojin; Jung, Joontaek; Lee, Wonjun; Ryu, Jungho; Choi, Hongsoo

2018-07-01

Micro-electromechanical system (MEMS) technologies were used to develop a thickness-mode piezoelectric micromachined ultrasonic transducer (Tm-pMUT) annular array utilizing a lead magnesium niobate–lead zirconate titanate (PMN–PZT) single crystal prepared by the solid-state single-crystal-growth method. Dicing is a conventional processing method for PMN–PZT single crystals, but MEMS technology can be adopted for the development of Tm-pMUT annular arrays and has various advantages, including fabrication reliability, repeatability, and a curved element shape. An inductively coupled plasma–reactive ion etching process was used to etch a brittle PMN–PZT single crystal selectively. Using this process, eight ring-shaped elements were realized in an area of 1  ×  1 cm2. The resonance frequency and effective electromechanical coupling coefficient of the Tm-pMUT annular array were 2.66 (±0.04) MHz, 3.18 (±0.03) MHz, and 30.05%, respectively, in the air. The maximum positive acoustic pressure in water, measured at a distance of 7.27 mm, was 40 kPa from the Tm-pMUT annular array driven by a 10 Vpp sine wave at 2.66 MHz without beamforming. The proposed Tm-pMUT annular array using a PMN–PZT single crystal has the potential for various applications, such as a fingerprint sensor, and for ultrasonic cell stimulation and low-intensity tissue stimulation.

Use of KRS-XE positive chemically amplified resist for optical mask manufacturing

NASA Astrophysics Data System (ADS)

Ashe, Brian; Deverich, Christina; Rabidoux, Paul A.; Peck, Barbara; Petrillo, Karen E.; Angelopoulos, Marie; Huang, Wu-Song; Moreau, Wayne M.; Medeiros, David R.

2002-03-01

The traditional mask making process uses chain scission-type resists such as PBS, poly(butene-1-sulfone), and ZEP, poly(methyl a-chloroacrylate-co-a-methylstyrene) for making masks with dimensions greater than 180nm. PBS resist requires a wet etch process to produce patterns in chrome. ZEP was employed for dry etch processing to meet the requirements of shrinking dimensions, optical proximity corrections and phase shift masks. However, ZEP offers low contrast, marginal etch resistance, organic solvent development, and concerns regarding resist heating with its high dose requirements1. Chemically Amplified Resist (CAR) systems are a very good choice for dimensions less than 180nm because of their high sensitivity and contrast, high resolution, dry etch resistance, aqueous development, and process latitude2. KRS-XE was developed as a high contrast CA resist based on ketal protecting groups that eliminate the need for post exposure bake (PEB). This resist can be used for a variety of electron beam exposures, and improves the capability to fabricate masks for devices smaller than 180nm. Many factors influence the performance of resists in mask making such as post apply bake, exposure dose, resist develop, and post exposure bake. These items will be discussed as well as the use of reactive ion etching (RIE) selectivity and pattern transfer.

Electronic-carrier-controlled photochemical etching process in semiconductor device fabrication

DOEpatents

Ashby, C.I.H.; Myers, D.R.; Vook, F.L.

1988-06-16

An electronic-carrier-controlled photochemical etching process for carrying out patterning and selective removing of material in semiconductor device fabrication includes the steps of selective ion implanting, photochemical dry etching, and thermal annealing, in that order. In the selective ion implanting step, regions of the semiconductor material in a desired pattern are damaged and the remainder of the regions of the material not implanted are left undamaged. The rate of recombination of electrons and holes is increased in the damaged regions of the pattern compared to undamaged regions. In the photochemical dry etching step which follows ion implanting step, the material in the undamaged regions of the semiconductor are removed substantially faster than in the damaged regions representing the pattern, leaving the ion-implanted, damaged regions as raised surface structures on the semiconductor material. After completion of photochemical dry etching step, the thermal annealing step is used to restore the electrical conductivity of the damaged regions of the semiconductor material.

Electronic-carrier-controlled photochemical etching process in semiconductor device fabrication

DOEpatents

Ashby, Carol I. H.; Myers, David R.; Vook, Frederick L.

1989-01-01

An electronic-carrier-controlled photochemical etching process for carrying out patterning and selective removing of material in semiconductor device fabrication includes the steps of selective ion implanting, photochemical dry etching, and thermal annealing, in that order. In the selective ion implanting step, regions of the semiconductor material in a desired pattern are damaged and the remainder of the regions of the material not implanted are left undamaged. The rate of recombination of electrons and holes is increased in the damaged regions of the pattern compared to undamaged regions. In the photochemical dry etching step which follows ion implanting step, the material in the undamaged regions of the semiconductor are removed substantially faster than in the damaged regions representing the pattern, leaving the ion-implanted, damaged regions as raised surface structures on the semiconductor material. After completion of photochemical dry etching step, the thermal annealing step is used to restore the electrical conductivity of the damaged regions of the semiconductor material.

Fabrication and Characteristics of High Capacitance Al Thin Films Capacitor Using a Polymer Inhibitor Bath in Electroless Plating Process.

PubMed

Cho, Young-Lae; Lee, Jung-Woo; Lee, Chang-Hyoung; Choi, Hyung-Seon; Kim, Sung-Su; Song, Young Il; Park, Chan; Suh, Su-Jeong

2015-10-01

An aluminum (Al) thin film capacitor was fabricated for a high capacitance capacitor using electrochemical etching, barrier-type anodizing, and electroless Ni-P plating. In this study, we focused on the bottom-up filling of Ni-P electrodes on Al2O3/Al with etched tunnels. The Al tunnel pits were irregularly distributed on the Al foil, diameters were in the range of about 0.5~1 μm, the depth of the tunnel pits was approximately 35~40 μm, and the complex structure was made full filled hard metal. To control the plating rate, the experiment was performed by adding polyethyleneimine (PEI, C2H5N), a high molecular substance. PEI forms a cross-link at the etching tunnel inlet, playing the role of delaying the inlet plating. When the PEI solution bath was used after activation, the Ni-P layer was deposited selectively on the bottoms of the tunnels. The characteristics were analyzed by adding the PEI addition quantity rate of 100~600 mg/L into the DI water. The capacitance of the Ni-P/Al2O3 (650~700 nm)/Al film was measured at 1 kHz using an impedance/gain phase analyzer. For the plane film without etch tunnels the capacitance was 12.5 nF/cm2 and for the etch film with Ni-P bottom-up filling the capacitance was 92 nF/cm2. These results illustrate a remarkable maximization of capacitance for thin film metal capacitors.

Penetration Effects of the Compound Vortex in Gas Metal-Arc Welding

DTIC Science & Technology

1988-05-01

steel plate using constant current GMAW equipment and argon + 2;. oxygen shielding gas. After welding, the plates were cut, ground, polished and etched...49 14. Typical time plot of current used in pulsed GMAW ..... 51 15. The experimental apparatus ........................... 54 16. Plot...this phenomenon could be employed in some manner to yield high penetration welds with low average current. 2. Pulsed GMAW . KolodziejczaK [26] studied

Optimization of reactive-ion etching (RIE) parameters for fabrication of tantalum pentoxide (Ta2O5) waveguide using Taguchi method

NASA Astrophysics Data System (ADS)

Muttalib, M. Firdaus A.; Chen, Ruiqi Y.; Pearce, S. J.; Charlton, Martin D. B.

2017-11-01

In this paper, we demonstrate the optimization of reactive-ion etching (RIE) parameters for the fabrication of tantalum pentoxide (Ta2O5) waveguide with chromium (Cr) hard mask in a commercial OIPT Plasmalab 80 RIE etcher. A design of experiment (DOE) using Taguchi method was implemented to find optimum RF power, mixture of CHF3 and Ar gas ratio, and chamber pressure for a high etch rate, good selectivity, and smooth waveguide sidewall. It was found that the optimized etch condition obtained in this work were RF power = 200 W, gas ratio = 80 %, and chamber pressure = 30 mTorr with an etch rate of 21.6 nm/min, Ta2O5/Cr selectivity ratio of 28, and smooth waveguide sidewall.

Isolating GaSb membranes grown metamorphically on GaAs substrates using highly selective substrate removal etch processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavrova, Olga; Balakrishnan, Ganesh

2017-02-24

The etch rates of NH 4OH:H 2O 2 and C 6H 8O 7:H 2O 2 for GaAs and GaSb have been investigated to develop a selective etch for GaAs substrates and to isolate GaSb epilayers grown on GaAs. The NH 4OH:H 2O 2 solution has a greater etch rate differential for the GaSb/GaAs material system than C 6H 8O 7:H 2O 2 solution. The selectivity of NH 4OH:H 2O 2 for GaAs/GaSb under optimized etch conditions has been observed to be as high as 11471 ± 1691 whereas that of C 6H 8O 7:H 2O 2 has been measured upmore » to 143 ± 2. The etch contrast has been verified by isolating 2 μm thick GaSb epi-layers that were grown on GaAs substrates. GaSb membranes were tested and characterized with high-resolution X-Ray diffraction (HR-XRD) and atomic force microscopy (AFM).« less

Dopant type and/or concentration selective dry photochemical etching of semiconductor materials

DOEpatents

Ashby, Carol I. H.; Dishman, James L.

1987-01-01

A method of selectively photochemically dry etching a first semiconductor material of a given composition in the presence of a second semiconductor material which is of a composition different from said first material, said second material substantially not being etched during said method, comprises subjecting both materials to the same photon flux of an energy greater than their respective direct bandgaps and to the same gaseous chemical etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said conditions also being such that the resultant electronic structure of the first semiconductor material under said photon flux is sufficient for the first material to undergo substantial photochemical etching under said conditions and being such that the resultant electronic structure of the second semiconductor material under said photon flux is not sufficient for the second material to undergo substantial photochemical etching under said conditions. In a preferred mode, the materials are subjected to a bias voltage which suppresses etching in n- or p- type material but not in p- or n-type material, respectively; or suppresses etching in the more heavily doped of two n-type or two p-type materials.

Dopant type and/or concentration selective dry photochemical etching of semiconductor materials

DOEpatents

Ashby, C.R.H.; Dishman, J.L.

1985-10-11

Disclosed is a method of selectively photochemically dry etching a first semiconductor material of a given composition in the presence of a second semiconductor material which is of a composition different from said first material, said second material substantially not being etched during said method. The method comprises subjecting both materials to the same photon flux of an energy greater than their respective direct bandgaps and to the same gaseous chemical etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said conditions also being such that the resultant electronic structure of the first semiconductor material under said photon flux is sufficient for the first material to undergo substantial photochemical etching under said conditions and being such that the resultant electronic structure of the second semiconductor material under said photon flux is not sufficient for the second material to undergo substantial photochemical etching under said conditions. In a preferred mode, the materials are subjected to a bias voltage which suppresses etching in n- or p-type material but not in p- or n-type material, respectively; or suppresses etching in the more heavily doped of two n-type or two p-type materials.

Study of radioactive impurities in neutron transmutation doped germanium

NASA Astrophysics Data System (ADS)

Mathimalar, S.; Dokania, N.; Singh, V.; Nanal, V.; Pillay, R. G.; Shrivastava, A.; Jagadeesan, K. C.; Thakare, S. V.

2015-02-01

A program to develop low temperature (mK) sensors with neutron transmutation doped Ge for rare event studies with a cryogenic bolometer has been initiated. For this purpose, semiconductor grade Ge wafers are irradiated with thermal neutron flux from Dhruva reactor at Bhabha Atomic Research Centre (BARC), Mumbai. Spectroscopic studies of irradiated samples have revealed that the environment of the capsule used for irradiating the sample leads to significant levels of 65Zn, 110mAg and 182Ta impurities, which can be reduced by chemical etching of approximately 50 μm thick surface layer. From measurements of the etched samples in the low background counting setup, activity due to trace impurities of 123Sb in bulk Ge is estimated to be 1 Bq / g after irradiation. These estimates indicate that in order to use the NTD Ge sensors for rare event studies, a cooldown period of 2 years would be necessary to reduce the radioactive background to ≤ 1 mBq / g.

Mesoporous carbon-supported Pd nanoparticles with high specific surface area for cyclohexene hydrogenation: Outstanding catalytic activity of NaOH-treated catalysts

NASA Astrophysics Data System (ADS)

Puskás, R.; Varga, T.; Grósz, A.; Sápi, A.; Oszkó, A.; Kukovecz, Á.; Kónya, Z.

2016-06-01

Extremely high specific surface area mesoporous carbon-supported Pd nanoparticle catalysts were prepared with both impregnation and polyol-based sol methods. The silica template used for the synthesis of mesoporous carbon was removed by both NaOH and HF etching. Pd/mesoporous carbon catalysts synthesized with the impregnation method has as high specific surface area as 2250 m2/g. In case of NaOH-etched impregnated samples, the turnover frequency of cyclohexene hydrogenation to cyclohexane at 313 K was obtained 14 molecules • site- 1 • s- 1. The specific surface area of HF-etched samples was higher compared to NaOH-etched samples. However, catalytic activity was 3-6 times higher on NaOH-etched samples compared to HF-etched samples, which can be attributed to the presence of sodium and surface hydroxylgroups of the catalysts etched with NaOH solution.

Effect of a New Surface Treatment Solution on the Bond Strength of Composite to Enamel

DTIC Science & Technology

2016-06-01

enamel ( Erickson et al., 2005). More significantly, clinical studies have shown significantly less marginal defects and staining with selective...using phosphoric acid. Erickson et al., (2009) also found improved bond strengths with a selective-etch step and attributed this to the degree of...cut enamel and dentin. Oper Dent 2005;30(1):39-49. Erickson RL, Barkmeier WW, Kimmes NS. Bond strength of self-etch adhesives to pre-etched

Investigation of Nitride Morphology After Self-Aligned Contact Etch

NASA Technical Reports Server (NTRS)

Hwang, Helen H.; Keil, J.; Helmer, B. A.; Chien, T.; Gopaladasu, P.; Kim, J.; Shon, J.; Biegel, Bryan (Technical Monitor)

2001-01-01

Self-Aligned Contact (SAC) etch has emerged as a key enabling technology for the fabrication of very large-scale memory devices. However, this is also a very challenging technology to implement from an etch viewpoint. The issues that arise range from poor oxide etch selectivity to nitride to problems with post etch nitride surface morphology. Unfortunately, the mechanisms that drive nitride loss and surface behavior remain poorly understood. Using a simple langmuir site balance model, SAC nitride etch simulations have been performed and compared to actual etched results. This approach permits the study of various etch mechanisms that may play a role in determining nitride loss and surface morphology. Particle trajectories and fluxes are computed using Monte-Carlo techniques and initial data obtained from double Langmuir probe measurements. Etched surface advancement is implemented using a shock tracking algorithm. Sticking coefficients and etch yields are adjusted to obtain the best agreement between actual etched results and simulated profiles.

A study of GaN-based LED structure etching using inductively coupled plasma

NASA Astrophysics Data System (ADS)

Wang, Pei; Cao, Bin; Gan, Zhiyin; Liu, Sheng

2011-02-01

GaN as a wide band gap semiconductor has been employed to fabricate optoelectronic devices such as light-emitting diodes (LEDs) and laser diodes (LDs). Recently several different dry etching techniques for GaN-based materials have been developed. ICP etching is attractive because of its superior plasma uniformity and strong controllability. Most previous reports emphasized on the ICP etching characteristics of single GaN film. In this study dry etching of GaN-based LED structure was performed by inductively coupled plasmas (ICP) etching with Cl2 as the base gas and BCl3 as the additive gas. The effects of the key process parameters such as etching gases flow rate, ICP power, RF power and chamber pressure on the etching properties of GaN-based LED structure including etching rate, selectivity, etched surface morphology and sidewall was investigated. Etch depths were measured using a depth profilometer and used to calculate the etch rates. The etch profiles were observed with a scanning electron microscope (SEM).

Synchrotron radiation x-ray topography and defect selective etching analysis of threading dislocations in GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sintonen, Sakari, E-mail: sakari.sintonen@aalto.fi; Suihkonen, Sami; Jussila, Henri

2014-08-28

The crystal quality of bulk GaN crystals is continuously improving due to advances in GaN growth techniques. Defect characterization of the GaN substrates by conventional methods is impeded by the very low dislocation density and a large scale defect analysis method is needed. White beam synchrotron radiation x-ray topography (SR-XRT) is a rapid and non-destructive technique for dislocation analysis on a large scale. In this study, the defect structure of an ammonothermal c-plane GaN substrate was recorded using SR-XRT and the image contrast caused by the dislocation induced microstrain was simulated. The simulations and experimental observations agree excellently and themore » SR-XRT image contrasts of mixed and screw dislocations were determined. Apart from a few exceptions, defect selective etching measurements were shown to correspond one to one with the SR-XRT results.« less

Fabrication and Characterization of CMOS-MEMS Thermoelectric Micro Generators

PubMed Central

Kao, Pin-Hsu; Shih, Po-Jen; Dai, Ching-Liang; Liu, Mao-Chen

2010-01-01

This work presents a thermoelectric micro generator fabricated by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and the post-CMOS process. The micro generator is composed of 24 thermocouples in series. Each thermocouple is constructed by p-type and n-type polysilicon strips. The output power of the generator depends on the temperature difference between the hot and cold parts in the thermocouples. In order to prevent heat-receiving in the cold part in the thermocouples, the cold part is covered with a silicon dioxide layer with low thermal conductivity to insulate the heat source. The hot part of the thermocouples is suspended and connected to an aluminum plate, to increases the heat-receiving area in the hot part. The generator requires a post-CMOS process to release the suspended structures. The post-CMOS process uses an anisotropic dry etching to remove the oxide sacrificial layer and an isotropic dry etching to etch the silicon substrate. Experimental results show that the micro generator has an output voltage of 67 μV at the temperature difference of 1 K. PMID:22205869

Performance of Universal Adhesive in Primary Molars After Selective Removal of Carious Tissue: An 18-Month Randomized Clinical Trial.

PubMed

Lenzi, Tathiane Larissa; Pires, Carine Weber; Soares, Fabio Zovico Maxnuck; Raggio, Daniela Prócida; Ardenghi, Thiago Machado; de Oliveira Rocha, Rachel

2017-09-15

To evaluate the 18-month clinical performance of a universal adhesive, applied under different adhesion strategies, after selective carious tissue removal in primary molars. Forty-four subjects (five to 10 years old) contributed with 90 primary molars presenting moderately deep dentin carious lesions on occlusal or occluso-proximal surfaces, which were randomly assigned following either self-etch or etch-and-rinse protocol of Scotchbond Universal Adhesive (3M ESPE). Resin composite was incrementally inserted for all restorations. Restorations were evaluated at one, six, 12, and 18 months using the modified United States Public Health Service criteria. Survival estimates for restorations' longevity were evaluated using the Kaplan-Meier method. Multivariate Cox regression analysis with shared frailty to assess the factors associated with failures (P<0.05). Estimated survival rates of the restorations were 100 percent, 100 percent, 90.6 percent, and 81.4 percent at one, six, 12, and 18 months, respectively. The adhesion strategy did not influence the restorations' longevity (P=0.06; 72.2 percent and 89.7 percent with etch-and-rinse and self-etch mode, respectively). Self-etch and etch-and-rinse strategies did not influence the clinical behavior of universal adhesive used in primary molars after selective carious tissue removal; although there was a tendency for better outcome of the self-etch strategy.

Fluorocarbon assisted atomic layer etching of SiO 2 and Si using cyclic Ar/C 4F 8 and Ar/CHF 3 plasma

DOE PAGES

Metzler, Dominik; Li, Chen; Engelmann, Sebastian; ...

2015-11-11

The need for atomic layer etching (ALE) is steadily increasing as smaller critical dimensions and pitches are required in device patterning. A flux-control based cyclic Ar/C 4F 8 ALE based on steady-state Ar plasma in conjunction with periodic, precise C 4F 8 injection and synchronized plasma-based low energy Ar + ion bombardment has been established for SiO 2. 1 In this work, the cyclic process is further characterized and extended to ALE of silicon under similar process conditions. The use of CHF 3 as a precursor is examined and compared to C 4F 8. CHF 3 is shown to enablemore » selective SiO 2/Si etching using a fluorocarbon (FC) film build up. Other critical process parameters investigated are the FC film thickness deposited per cycle, the ion energy, and the etch step length. Etching behavior and mechanisms are studied using in situ real time ellipsometry and X-ray photoelectron spectroscopy. Silicon ALE shows less self-limitation than silicon oxide due to higher physical sputtering rates for the maximum ion energies used in this work, ranged from 20 to 30 eV. The surface chemistry is found to contain fluorinated silicon oxide during the etching of silicon. As a result, plasma parameters during ALE are studied using a Langmuir probe and establish the impact of precursor addition on plasma properties.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yu; School of Mechanical and Electrical Engineering, Wuhan Institute of Technology, Wuhan 430073; Guo, Zhiguang, E-mail: zguo@licp.cas.cn

Graphical abstract: A double-metal-assisted chemical etching method is employed to fabricate superhydrophobic surfaces, showing a good superhydrophobicity with the contact angle of about 170°, and the sliding angle of about 0°. Meanwhile, the potential formation mechanism about it is also presented. Highlights: ► A double-metal-assisted chemical etching method is employed to fabricate superhydrophobic surfaces. ► The obtained surfaces show good superhydrophobicity with a high contact angle and low sliding angle. ► The color of the etched substrate dark brown or black and it is so-called black silicon. -- Abstract: Silicon substrates treated by metal-assisted chemical etching have been studied formore » many years since they could be employed in a variety of electronic and optical devices such as integrated circuits, photovoltaics, sensors and detectors. However, to the best of our knowledge, the chemical etching treatment on the same silicon substrate with the assistance of two or more kinds of metals has not been reported. In this paper, we mainly focus on the etching time and finally obtain a series of superhydrophobic silicon surfaces with novel etching structures through two successive etching processes of Cu-assisted and Ag-assisted chemical etching. It is shown that large-scale homogeneous but locally irregular wire-like structures are obtained, and the superhydrophobic surfaces with low hysteresis are prepared after the modifications with low surface energy materials. It is worth noting that the final silicon substrates not only possess high static contact angle and low hysteresis angle, but also show a black color, indicating that the superhydrophobic silicon substrate has an extremely low reflectance in a certain range of wavelengths. In our future work, we will go a step further to discuss the effect of temperature, the size of Cu nanoparticles and solution concentration on the final topography and superhydrophobicity.« less

Etching Selectivity of Cr, Fe and Ni Masks on Si & SiO2 Wafers

NASA Astrophysics Data System (ADS)

Garcia, Jorge; Lowndes, Douglas H.

2000-10-01

During this Summer 2000 I joined the Semiconductors and Thin Films group led by Dr. Douglas H. Lowndes at Oak Ridge National Laboratory’s Solid State Division. Our objective was to evaluate the selectivity that Trifluoromethane (CHF3), and Sulfur Hexafluoride (SF6) plasmas have for Si, SiO2 wafers and the Ni, Cr, and Fe masks; being this etching selectivity the ratio of the etching rates of the plasmas for each of the materials. We made use of Silicon and Silicon Dioxide-coated wafers that have Fe, Cr or Ni masks. In the semiconductor field, metal layers are often used as masks to protect layers underneath during processing steps; when these wafers are taken to the dry etching process, both the wafer and the mask layers’ thickness are reduced.

Highly selective dry etching of GaP in the presence of AlxGa1–xP with a SiCl4/SF6 plasma

NASA Astrophysics Data System (ADS)

Hönl, Simon; Hahn, Herwig; Baumgartner, Yannick; Czornomaz, Lukas; Seidler, Paul

2018-05-01

We present an inductively coupled-plasma reactive-ion etching process that simultaneously provides both a high etch rate and unprecedented selectivity for gallium phosphide (GaP) in the presence of aluminum gallium phosphide (AlxGa1–xP). Utilizing mixtures of silicon tetrachloride (SiCl4) and sulfur hexafluoride (SF6), selectivities exceeding 2700:1 are achieved at GaP etch rates above 3000 nm min‑1. A design of experiments has been employed to investigate the influence of the inductively coupled-plasma power, the chamber pressure, the DC bias and the ratio of SiCl4 to SF6. The process enables the use of thin AlxGa1–xP stop layers even at aluminum contents of a few percent.

Selective Plasma Etching of Polymeric Substrates for Advanced Applications

PubMed Central

Puliyalil, Harinarayanan; Cvelbar, Uroš

2016-01-01

In today’s nanoworld, there is a strong need to manipulate and process materials on an atom-by-atom scale with new tools such as reactive plasma, which in some states enables high selectivity of interaction between plasma species and materials. These interactions first involve preferential interactions with precise bonds in materials and later cause etching. This typically occurs based on material stability, which leads to preferential etching of one material over other. This process is especially interesting for polymeric substrates with increasing complexity and a “zoo” of bonds, which are used in numerous applications. In this comprehensive summary, we encompass the complete selective etching of polymers and polymer matrix micro-/nanocomposites with plasma and unravel the mechanisms behind the scenes, which ultimately leads to the enhancement of surface properties and device performance. PMID:28335238

Method of fabricating vertically aligned group III-V nanowires

DOEpatents

Wang, George T; Li, Qiming

2014-11-25

A top-down method of fabricating vertically aligned Group III-V micro- and nanowires uses a two-step etch process that adds a selective anisotropic wet etch after an initial plasma etch to remove the dry etch damage while enabling micro/nanowires with straight and smooth faceted sidewalls and controllable diameters independent of pitch. The method enables the fabrication of nanowire lasers, LEDs, and solar cells.

SiO2 Hole Etching Using Perfluorocarbon Alternative Gas with Small Global Greenhouse Effect

NASA Astrophysics Data System (ADS)

Ooka, Masahiro; Yokoyama, Shin

2004-06-01

The etching of contact holes of 0.1 μm size in SiO2 is achieved using, for the first time, cyclic (c-)C5F8 with a small greenhouse effect in the pulse-modulated inductively coupled plasma. The shape of the cross section of the contact hole is as good as that etched using conventional c-C4F8. It is confirmed that Kr mixing instead of Ar in the plasma does not change the etching characteristics, although lowering of the electron temperature is expected which reduces the plasma-induced damage. Pulse modulation of the plasma is found to improve the etching selectivity of SiO2 with respect to Si. Langmuir probe measurement of the plasma suggests that the improvement of the etching selectivity is due to the deposition of fluorocarbon film triggered by lowering of the electron temperature when the off time of the radio frequency (rf) power is extended.

Surface morphology and dislocation characteristics near the surface of 4H-SiC wafer using multi-directional scanning transmission electron microscopy.

PubMed

Sato, Takahiro; Orai, Yoshihisa; Suzuki, Yuya; Ito, Hiroyuki; Isshiki, Toshiyuki; Fukui, Munetoshi; Nakamura, Kuniyasu; Schamp, C T

2017-10-01

To improve the reliability of silicon carbide (SiC) electronic power devices, the characteristics of various kinds of crystal defects should be precisely understood. Of particular importance is understanding the correlation between the surface morphology and the near surface dislocations. In order to analyze the dislocations near the surface of 4H-SiC wafers, a dislocation analysis protocol has been developed. This protocol consists of the following process: (1) inspection of surface defects using low energy scanning electron microscopy (LESEM), (2) identification of small and shallow etch pits using KOH low temperature etching, (3) classification of etch pits using LESEM, (4) specimen preparation of several hundred nanometer thick sample using the in-situ focused ion beam micro-sampling® technique, (5) crystallographic analysis using the selected diffraction mode of the scanning transmission electron microscope (STEM), and (6) determination of the Burgers vector using multi-directional STEM (MD-STEM). The results show a correlation between the triangular terrace shaped surface defects and an hexagonal etch pit arising from threading dislocations, linear shaped surface defects and elliptical shaped etch pits arising from basal plane dislocations. Through the observation of the sample from two orthogonal directions via the MD-STEM technique, a basal plane dislocation is found to dissociate into an extended dislocation bound by two partial dislocations. A protocol developed and presented in this paper enables one to correlate near surface defects of a 4H-SiC wafer with the root cause dislocations giving rise to those surface defects. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Controllable poly-crystalline bilayered and multilayered graphene film growth by reciprocal chemical vapor deposition

NASA Astrophysics Data System (ADS)

Wu, Qinke; Jung, Seong Jun; Jang, Sung Kyu; Lee, Joohyun; Jeon, Insu; Suh, Hwansoo; Kim, Yong Ho; Lee, Young Hee; Lee, Sungjoo; Song, Young Jae

2015-06-01

We report the selective growth of large-area bilayered graphene film and multilayered graphene film on copper. This growth was achieved by introducing a reciprocal chemical vapor deposition (CVD) process that took advantage of an intermediate h-BN layer as a sacrificial template for graphene growth. A thin h-BN film, initially grown on the copper substrate using CVD methods, was locally etched away during the subsequent graphene growth under residual H2 and CH4 gas flows. Etching of the h-BN layer formed a channel that permitted the growth of additional graphene adlayers below the existing graphene layer. Bilayered graphene typically covers an entire Cu foil with domain sizes of 10-50 μm, whereas multilayered graphene can be epitaxially grown to form islands a few hundreds of microns in size. This new mechanism, in which graphene growth proceeded simultaneously with h-BN etching, suggests a potential approach to control graphene layers for engineering the band structures of large-area graphene for electronic device applications.We report the selective growth of large-area bilayered graphene film and multilayered graphene film on copper. This growth was achieved by introducing a reciprocal chemical vapor deposition (CVD) process that took advantage of an intermediate h-BN layer as a sacrificial template for graphene growth. A thin h-BN film, initially grown on the copper substrate using CVD methods, was locally etched away during the subsequent graphene growth under residual H2 and CH4 gas flows. Etching of the h-BN layer formed a channel that permitted the growth of additional graphene adlayers below the existing graphene layer. Bilayered graphene typically covers an entire Cu foil with domain sizes of 10-50 μm, whereas multilayered graphene can be epitaxially grown to form islands a few hundreds of microns in size. This new mechanism, in which graphene growth proceeded simultaneously with h-BN etching, suggests a potential approach to control graphene layers for engineering the band structures of large-area graphene for electronic device applications. Electronic supplementary information (ESI) available: The growth conditions, statistical studies of OM images and high-resolution STM/TEM measurements for multi-/bi-layered graphene are discussed in detail. See DOI: 10.1039/c5nr02716k

Changes in boron fiber strength due to surface removal by chemical etching

NASA Technical Reports Server (NTRS)

Smith, R. J.

1976-01-01

The effects of chemical etching on the tensile strength of commercial boron/tungsten fibers were investigated. Fibers with as-received diameters of 203, 143, and 100 micrometers were etched to diameters as small as 43 micrometers. The etching generally resulted in increasing fiber tensile strength with decreasing fiber diameter. And for the 203 micrometer fibers there was an accompanying significant decrease in the coefficient of variation of the tensile strength for diameters down to 89 micrometers. Heat treating these fibers above 1,173 K in a vacuum caused a marked decrease in the average tensile strength of at least 80 percent. But after the fibers were etched, their strengths exceeded the as-received strengths. The tensile strength behavior is explained in terms of etching effects on surface flaws and the residual stress pattern of the as-received fibers.

Etching and oxidation of InAs in planar inductively coupled plasma

NASA Astrophysics Data System (ADS)

Dultsev, F. N.; Kesler, V. G.

2009-10-01

The surface of InAs (1 1 1)A was investigated under plasmachemical etching in the gas mixture CH 4/H 2/Ar. Etching was performed using the RF (13.56 MHz) and ICP plasma with the power 30-150 and 50-300 W, respectively; gas pressure in the reactor was 3-10 mTorr. It was demonstrated that the composition of the subsurface layer less than 5 nm thick changes during plasmachemical etching. A method of deep etching of InAs involving ICP plasma and hydrocarbon based chemistry providing the conservation of the surface relief is proposed. Optimal conditions and the composition of the gas phase for plasmachemical etching ensuring acceptable etch rates were selected.

CR-39 track etching and blow-up method

DOEpatents

Hankins, Dale E.

1987-01-01

This invention is a method of etching tracks in CR-39 foil to obtain uniformly sized tracks. The invention comprises a step of electrochemically etching the foil at a low frequency and a "blow-up" step of electrochemically etching the foil at a high frequency.

Liquid droplet sensing using twisted optical fiber couplers fabricated by hydrofluoric acid flow etching

NASA Astrophysics Data System (ADS)

Son, Gyeongho; Jung, Youngho; Yu, Kyoungsik

2017-04-01

We report a directional-coupler-based refractive index sensor and its cost-effective fabrication method using hydrofluoric acid droplet wet-etching and surface-tension-driven liquid flows. The proposed fiber sensor consists of a pair of twisted tapered optical fibers with low excess losses. The fiber cores in the etched microfiber region are exposed to the surrounding medium for efficient interaction with the guided light. We observe that the etching-based low-loss fiber-optic sensors can measure the water droplet volume by detecting the refractive index changes of the surrounding medium around the etched fiber core region.

Shear Alignment of Diblock Copolymers for Patterning Nanowire Meshes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gustafson, Kyle T.

2016-09-08

Metallic nanowire meshes are useful as cheap, flexible alternatives to indium tin oxide – an expensive, brittle material used in transparent conductive electrodes. We have fabricated nanowire meshes over areas up to 2.5 cm 2 by: 1) mechanically aligning parallel rows of diblock copolymer (diBCP) microdomains; 2) selectively infiltrating those domains with metallic ions; 3) etching away the diBCP template; 4) sintering to reduce ions to metal nanowires; and, 5) repeating steps 1 – 4 on the same sample at a 90° offset. We aligned parallel rows of polystyrene-b-poly(2-vinylpyridine) [PS(48.5 kDa)-b-P2VP(14.5 kDa)] microdomains by heating above its glass transition temperaturemore » (T g ≈ 100°C), applying mechanical shear pressure (33 kPa) and normal force (13.7 N), and cooling below T g. DiBCP samples were submerged in aqueous solutions of metallic ions (15 – 40 mM ions; 0.1 – 0.5 M HCl) for 30 – 90 minutes, which coordinate to nitrogen in P2VP. Subsequent ozone-etching and sintering steps yielded parallel nanowires. We aimed to optimize alignment parameters (e.g. shear and normal pressures, alignment duration, and PDMS thickness) to improve the quality, reproducibility, and scalability of meshes. We also investigated metals other than Pt and Au that may be patterned using this technique (Cu, Ag).« less

Selective etching of silicon carbide films

DOEpatents

Gao, Di; Howe, Roger T.; Maboudian, Roya

2006-12-19

A method of etching silicon carbide using a nonmetallic mask layer. The method includes providing a silicon carbide substrate; forming a non-metallic mask layer by applying a layer of material on the substrate; patterning the mask layer to expose underlying areas of the substrate; and etching the underlying areas of the substrate with a plasma at a first rate, while etching the mask layer at a rate lower than the first rate.

Low-Cost Rapid Prototyping of Whole-Glass Microfluidic Devices

ERIC Educational Resources Information Center

Yuen, Po Ki; Goral, Vasiliy N.

2012-01-01

A low-cost, straightforward, rapid prototyping of whole-glass microfluidic devices is presented using glass-etching cream that can be easily purchased in local stores. A self-adhered vinyl stencil cut out by a desktop digital craft cutter was used as an etching mask for patterning microstructures in glass using the glass-etching cream. A specific…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzler, Dominik; Li, Chen; Engelmann, Sebastian

The need for atomic layer etching (ALE) is steadily increasing as smaller critical dimensions and pitches are required in device patterning. A flux-control based cyclic Ar/C 4F 8 ALE based on steady-state Ar plasma in conjunction with periodic, precise C 4F 8 injection and synchronized plasma-based low energy Ar + ion bombardment has been established for SiO 2. 1 In this work, the cyclic process is further characterized and extended to ALE of silicon under similar process conditions. The use of CHF 3 as a precursor is examined and compared to C 4F 8. CHF 3 is shown to enablemore » selective SiO 2/Si etching using a fluorocarbon (FC) film build up. Other critical process parameters investigated are the FC film thickness deposited per cycle, the ion energy, and the etch step length. Etching behavior and mechanisms are studied using in situ real time ellipsometry and X-ray photoelectron spectroscopy. Silicon ALE shows less self-limitation than silicon oxide due to higher physical sputtering rates for the maximum ion energies used in this work, ranged from 20 to 30 eV. The surface chemistry is found to contain fluorinated silicon oxide during the etching of silicon. As a result, plasma parameters during ALE are studied using a Langmuir probe and establish the impact of precursor addition on plasma properties.« less

Fabrication of 3D surface structures using grayscale lithography

NASA Astrophysics Data System (ADS)

Stilson, Christopher; Pal, Rajan; Coutu, Ronald A.

2014-03-01

The ability to design and develop 3D microstructures is important for microelectromechanical systems (MEMS) fabrication. Previous techniques used to create 3D devices included tedious steps in direct writing and aligning patterns onto a substrate followed by multiple photolithography steps using expensive, customized equipment. Additionally, these techniques restricted batch processing and placed limits on achievable shapes. Gray-scale lithography enables the fabrication of a variety of shapes using a single photolithography step followed by reactive ion etching (RIE). Micromachining 3D silicon structures for MEMS can be accomplished using gray-scale lithography along with dry anisotropic etching. In this study, we investigated: using MATLAB for mask designs; feasibility of using 1 μm Heidelberg mask maker to direct write patterns onto photoresist; using RIE processing to etch patterns into a silicon substrate; and the ability to tailor etch selectivity for precise fabrication. To determine etch rates and to obtain desired etch selectivity, parameters such as gas mixture, gas flow, and electrode power were studied. This process successfully demonstrates the ability to use gray-scale lithography and RIE for use in the study of micro-contacts. These results were used to produce a known engineered non-planer surface for testing micro-contacts. Surface structures are between 5 μm and 20 μm wide with varying depths and slopes based on mask design and etch rate selectivity. The engineered surfaces will provide more insight into contact geometries and failure modes of fixed-fixed micro-contacts.

Inorganic Bi/In thermal resist as a high-etch-ratio patterning layer for CF4/CHF3/O2 plasma etch

NASA Astrophysics Data System (ADS)

Tu, Yuqiang; Chapman, Glenn H.; Peng, Jun

2004-05-01

Bimetallic thin films containing indium and with low eutectic points, such as Bi/In, have been found to form highly sensitive thermal resists. They can be exposed by lasers with a wide range of wavelengths and be developed by diluted RCA2 solutions. The exposed bimetallic resist Bi/In can work as an etch masking layer for alkaline-based (KOH, TMAH and EDP) "wet" Si anisotropic etching. Current research shows that it can also act as a patterning and masking layer for Si and SiO2 plasma "dry" etch using CF4/CHF3. The profile of etched structures can be tuned by adding CHF3 and other gases such as Ar, and by changing the CF4/CHF3 ratio. Depending on the fluorocarbon plasma etching recipe the etch rate of laser exposed Bi/In can be as low as 0.1nm/min, 500 times lower than organic photoresists. O2 plasma ashing has little etching effect on exposed Bi/In, indicating that laser exposure is an oxidation process. Experiment result shows that single metal Indium film and bilayer Sn/In exhibit thermal resist characteristics but at higher exposure levels. They can be developed in diluted RCA2 solution and used as etch mask layers for Si anisotropic etch and plasma etch.

GaN membrane MSM ultraviolet photodetectors

NASA Astrophysics Data System (ADS)

Muller, A.; Konstantinidis, G.; Kostopoulos, A.; Dragoman, M.; Neculoiu, D.; Androulidaki, M.; Kayambaki, M.; Vasilache, D.; Buiculescu, C.; Petrini, I.

2006-12-01

GaN exhibits unique physical properties, which make this material very attractive for wide range of applications and among them ultraviolet detection. For the first time a MSM type UV photodetector structure was manufactured on a 2.2 μm. thick GaN membrane obtained using micromachining techniques. The low unintentionally doped GaN layer structure was grown by MOCVD on high resistivity (ρ>10kΩcm) <111> oriented silicon wafers, 500μm thick. The epitaxially grown layers include a thin AlN layer in order to reduce the stress in the GaN layer and avoid cracking. Conventional contact lithography, e-gun Ni/Au (10nm /200nm) evaporation and lift-off techniques were used to define the interdigitated Schottky metalization on the top of the wafer. Ten digits with a width of 1μm and a length of 100μm were defined for each electrode. The distance between the digits was also 1μm. After the backside lapping of the wafer to a thickness of approximately 150μm, a 400nm thick Al layer was patterned and deposited on the backside, to be used as mask for the selective reactive ion etching of silicon. The backside mask, for the membrane formation, was patterned using double side alignment techniques and silicon was etched down to the 2.2μm thin GaN layer using SF 6 plasma. A very low dark current (30ρA at 3V) was obtained. Optical responsivity measurements were performed at 1.5V. A maximum responsivity of 18mA/W was obtained at a wavelength of 370nm. This value is very good and can be further improved using transparent contacts for the interdigitated structure.

Wafer-Level Membrane-Transfer Process for Fabricating MEMS

NASA Technical Reports Server (NTRS)

Yang, Eui-Hyeok; Wiberg, Dean

2003-01-01

A process for transferring an entire wafer-level micromachined silicon structure for mating with and bonding to another such structure has been devised. This process is intended especially for use in wafer-level integration of microelectromechanical systems (MEMS) that have been fabricated on dissimilar substrates. Unlike in some older membrane-transfer processes, there is no use of wax or epoxy during transfer. In this process, the substrate of a wafer-level structure to be transferred serves as a carrier, and is etched away once the transfer has been completed. Another important feature of this process is that two electrodes constitutes an electrostatic actuator array. An SOI wafer and a silicon wafer (see Figure 1) are used as the carrier and electrode wafers, respectively. After oxidation, both wafers are patterned and etched to define a corrugation profile and electrode array, respectively. The polysilicon layer is deposited on the SOI wafer. The carrier wafer is bonded to the electrode wafer by using evaporated indium bumps. The piston pressure of 4 kPa is applied at 156 C in a vacuum chamber to provide hermetic sealing. The substrate of the SOI wafer is etched in a 25 weight percent TMAH bath at 80 C. The exposed buried oxide is then removed by using 49 percent HF droplets after an oxygen plasma ashing. The SOI top silicon layer is etched away by using an SF6 plasma to define the corrugation profile, followed by the HF droplet etching of the remaining oxide. The SF6 plasma with a shadow mask selectively etches the polysilicon membrane, if the transferred membrane structure needs to be patterned. Electrostatic actuators with various electrode gaps have been fabricated by this transfer technique. The gap between the transferred membrane and electrode substrate is very uniform ( 0.1 m across a wafer diameter of 100 mm, provided by optimizing the bonding control). Figure 2 depicts the finished product.

Optical-fiber strain sensors with asymmetric etched structures.

PubMed

Vaziri, M; Chen, C L

1993-11-01

Optical-fiber strain gauges with asymmetric etched structures have been analyzed, fabricated, and tested. These sensors are very sensitive with a gauge factor as high as 170 and a flat frequency response to at least 2.7 kHz. The gauge factor depends on the asymmetry of the etched structures and the number of etched sections. To understand the physical principles involved, researchers have used structural analysis programs based on a finite-element method to analyze fibers with asymmetric etched structures under tensile stress. The results show that lateral bends are induced on the etched fibers when they are stretched axially. To relate the lateral bending to the optical attenuation, we have also employed a ray-tracing technique to investigate the dependence of the attenuation on the structural deformation. Based on the structural analysis and the ray-tracing study parameters affecting the sensitivity have been studied. These results agree with the results of experimental investigations.

Fabrication of vertical nanowire resonators for aerosol exposure assessment

NASA Astrophysics Data System (ADS)

Merzsch, Stephan; Wasisto, Hutomo Suryo; Stranz, Andrej; Hinze, Peter; Weimann, Thomas; Peiner, Erwin; Waag, Andreas

2013-05-01

Vertical silicon nanowire (SiNW) resonators are designed and fabricated in order to assess exposure to aerosol nanoparticles (NPs). To realize SiNW arrays, nanolithography and inductively coupled plasma (ICP) deep reactive ion etching (DRIE) at cryogenic temperature are utilized in a top-down fabrication of SiNW arrays which have high aspect ratios (i.e., up to 34). For nanolithography process, a resist film thickness of 350 nm is applied in a vacuum contact mode to serve as a mask. A pattern including various diameters and distances for creating pillars is used (i.e., 400 nm up to 5 μm). In dry etching process, the etch rate is set high of 1.5 μm/min to avoid underetching. The etch profiles of Si wires can be controlled aiming to have either perpendicularly, negatively or positively profiled sidewalls by adjusting the etching parameters (e.g., temperature and oxygen content). Moreover, to further miniaturize the wire, multiple sacrificial thermal oxidations and subsequent oxide stripping are used yielding SiNW arrays of 650 nm in diameter and 40 μm in length. In the resonant frequency test, a piezoelectric shear actuator is integrated with the SiNWs inside a scanning electron microscope (SEM) chamber. The observation of the SiNW deflections are performed and viewed from the topside of the SiNWs to reduce the measurement redundancy. Having a high deflection of ~10 μm during its resonant frequency of 452 kHz and a low mass of 31 pg, the proposed SiNW is potential for assisting the development of a portable aerosol resonant sensor.

Thermal resistance of etched-pillar vertical-cavity surface-emitting laser diodes

NASA Astrophysics Data System (ADS)

Wipiejewski, Torsten; Peters, Matthew G.; Young, D. Bruce; Thibeault, Brian; Fish, Gregory A.; Coldren, Larry A.

1996-03-01

We discuss our measurements on thermal impedance and thermal crosstalk of etched-pillar vertical-cavity lasers and laser arrays. The average thermal conductivity of AlAs-GaAs Bragg reflectors is estimated to be 0.28 W/(cmK) and 0.35W/(cmK) for the transverse and lateral direction, respectively. Lasers with a Au-plated heat spreading layer exhibit a 50% lower thermal impedance compared to standard etched-pillar devices resulting in a significant increase of maximum output power. For an unmounted laser of 64 micrometer diameter we obtain an improvement in output power from 20 mW to 42 mW. The experimental results are compared with a simple analytical model showing the importance of heat sinking for maximizing the output power of vertical-cavity lasers.

Fluorescence turn-on sensing of trace cadmium ions based on EDTA-etched CdTe@CdS quantum dot.

PubMed

Wang, Si-Nan; Zhu, Jian; Li, Xin; Li, Jian-Jun; Zhao, Jun-Wu

2018-05-01

Cadmium-caused environmental pollution and diseases have always been worldwide problems. Thus it is extremely urgent to establish a cheap, rapid, simple and selective detection method for trace cadmium in drinking water. In this study, a fluorescence "turn-on" method based on ethylene diamine tetraacetic acid (EDTA)-etched CdTe@CdS quantum dots (QDs) was designed to detect Cd 2+ . High resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) were utilized for chemical and structural characterization of the as-prepared QDs. Based on chemical etching of EDTA on the surface of CdTe@CdS QDs, specific Cd 2+ recognition sites were produced, and then results in fluorescence quenching. The introduction of Cd 2+ could identify these sites and restore the fluorescence of the EDTA-QDs system. Under the optimum conditions, the nanoprobe shows a linear response range from 0.05 to 9 μM with a very low detection limit of 0.032 μM. In addition, the reported fluorescence probe in this work displays a good selectivity for trace Cd 2+ over other metal ions and an admirable practicability in real water samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Photolithography and Selective Etching of an Array of Quartz Tuning Fork Resonators with Improved Impact Resistance Characteristics

NASA Astrophysics Data System (ADS)

Lee, Sungkyu

2001-08-01

Quartz tuning fork blanks with improved impact-resistant characteristics for use in Qualcomm mobile station modem (MSM)-3000 central processing unit (CPU) chips for code division multiple access (CDMA), personal communication system (PCS), and global system for mobile communication (GSM) systems were designed using finite element method (FEM) analysis and suitable processing conditions were determined for the reproducible precision etching of a Z-cut quartz wafer into an array of tuning forks. Negative photoresist photolithography for the additive process was used in preference to positive photoresist photolithography for the subtractive process to etch the array of quartz tuning forks. The tuning fork pattern was transferred via a conventional photolithographical chromium/quartz glass template using a standard single-sided aligner and subsequent negative photoresist development. A tightly adhering and pinhole-free 600/2000 Å chromium/gold mask was coated over the developed photoresist pattern which was subsequently stripped in acetone. This procedure was repeated on the back surface of the wafer. With the protective metallization area of the tuning fork geometry thus formed, etching through the quartz wafer was performed at 80°C in a ± 1.5°C controlled bath containing a concentrated solution of ammonium bifluoride to remove the unwanted areas of the quartz wafer. The quality of the quartz wafer surface finish after quartz etching depended primarily on the surface finish of the quartz wafer prior to etching and the quality of quartz crystals used. Selective etching of a 100 μm quartz wafer could be achieved within 90 min at 80°C. A selective etching procedure with reproducible precision has thus been established and enables the photolithographic mass production of miniature tuning fork resonators.

XPS study of the surface chemistry of UO2 (111) single crystal film

NASA Astrophysics Data System (ADS)

Maslakov, Konstantin I.; Teterin, Yury A.; Popel, Aleksej J.; Teterin, Anton Yu.; Ivanov, Kirill E.; Kalmykov, Stepan N.; Petrov, Vladimir G.; Springell, Ross; Scott, Thomas B.; Farnan, Ian

2018-03-01

A (111) air-exposed surface of UO2 thin film (150 nm) on (111) YSZ (yttria-stabilized zirconia) before and after the Ar+ etching and subsequent in situ annealing in the spectrometer analytic chamber was studied by XPS technique. The U 5f, U 4f and O 1s electron peak intensities were employed for determining the oxygen coefficient kO = 2 + x of a UO2+x oxide on the surface. It was found that initial surface (several nm) had kO = 2.20. A 20 s Ar+ etching led to formation of oxide UO2.12, whose composition does not depend significantly on the etching time (up to 180 s). Ar+ etching and subsequent annealing at temperatures 100-380 °C in vacuum was established to result in formation of stable well-organized structure UO2.12 reflected in the U 4f XPS spectra as high intensity (∼28% of the basic peak) shake-up satellites 6.9 eV away from the basic peaks, and virtually did not change the oxygen coefficient of the sample surface. This agrees with the suggestion that a stable (self-assembling) phase with the oxygen coefficient kO ≈ 2.12 forms on the UO2 surface.

Microfabricated multijunction thermal converters

NASA Astrophysics Data System (ADS)

Wunsch, Thomas Franzen

2001-12-01

In order to develop improved standards for the measurement of ac voltages and currents, a new thin-film fabrication technique for the multijunction thermal converter has been developed. The ability of a thermal converter to relate an rms ac voltage or current to a dc value is characterized by a quantity called `ac-dc difference' that is ideally zero. The best devices produced using the new techniques have ac-dc differences below 1 × 10-6 in the range of frequencies from 20 Hz to 10 kHz and below 7.5 × 10-6 in the range of frequencies from 20 kHz to 300 kHz. This is a reduction of two orders of magnitude in the lower frequency range and one order of magnitude in the higher frequency range over devices produced at the National Institute of Standards and Technology in 1996. The performance achieved is competitive with the best techniques in the world for ac measurements and additional evaluation is therefore warranted to determine the suitability of the devices for use as national standards that form the legal basis for traceable rms voltage measurements of time varying waveforms in the United States. The construction of the new devices is based on thin-film fabrication of a heated wire supported by a thermally isolated thin-film membrane. The membrane is produced utilizing a reactive ion plasma etch. A photoresist lift- off technique is used to pattern the metal thin-film layers that form the heater and the multijunction thermocouple circuit. The etching and lift-off allow the device to be produced without wet chemical etches that are time consuming and impede the investigation of structures with differing materials. These techniques result in an approach to fabrication that is simple, inexpensive, and free from the manual construction techniques used in the fabrication of conventional single and multijunction thermoelements. Thermal, thermoelectric, and electrical models have been developed to facilitate designs that reduce the low- frequency error. At high frequencies, from 300 kHz to 1 MHz, the performance of the device is degraded by a capacitive coupling effect that produces an ac-dc difference of approximately -90 × 10-6 at 1 MHz. A model is developed that explains this behavior. The model shows that an improvement in performance in the high-frequency range is possible through the use of very high or very low resistivity silicon substrates.

Verification of E-Beam direct write integration into 28nm BEOL SRAM technology

NASA Astrophysics Data System (ADS)

Hohle, Christoph; Choi, Kang-Hoon; Gutsch, Manuela; Hanisch, Norbert; Seidel, Robert; Steidel, Katja; Thrun, Xaver; Werner, Thomas

2015-03-01

Electron beam direct write lithography (EBDW) potentially offers advantages for low-volume semiconductor manufacturing, rapid prototyping or design verification due to its high flexibility without the need of costly masks. However, the integration of this advanced patterning technology into complex CMOS manufacturing processes remains challenging. The low throughput of today's single e-Beam tools limits high volume manufacturing applications and maturity of parallel (multi) beam systems is still insufficient [1,2]. Additional concerns like transistor or material damage of underlying layers during exposure at high electron density or acceleration voltage have to be addressed for advanced technology nodes. In the past we successfully proved that potential degradation effects of high-k materials or ULK shrink can be neglected and were excluded by demonstrating integrated electrical results of 28nm node transistor and BEOL performance following 50kV electron beam dry exposure [3]. Here we will give an update on the integration of EBDW in the 300mm CMOS manufacturing processes of advanced integrated circuits at the 28nm SRAM node of GLOBALFOUNDRIES Dresden. The work is an update to what has been previously published [4]. E-beam patterning results of BEOL full chip metal and via layers with a dual damascene integration scheme using a 50kV VISTEC SB3050DW variable shaped electron beam direct writer at Fraunhofer IPMSCNT are demonstrated. For the patterning of the Metal layer a Mix & Match concept based on the sequence litho - etch -litho -etch (LELE) was developed and evaluated wherein several exposure fields were blanked out during the optical exposure. Etch results are shown and compared to the POR. Results are also shown on overlay performance and optimized e-Beam exposure time using most advanced data prep solutions and resist processes. The patterning results have been verified using fully integrated electrical measurement of metal lines and vias on wafer level. In summary we demonstrate the integration capability of EBDW into a productive CMOS process flow at the example of the 28nm SRAM technology node.

Bond strength of universal adhesives: A systematic review and meta-analysis.

PubMed

Rosa, Wellington Luiz de Oliveira da; Piva, Evandro; Silva, Adriana Fernandes da

2015-07-01

A systematic review was conducted to determine whether the etch-and-rinse or self-etching mode is the best protocol for dentin and enamel adhesion by universal adhesives. This report followed the PRISMA Statement. A total of 10 articles were included in the meta-analysis. Two reviewers performed a literature search up to October 2014 in eight databases: PubMed, Web of Science, Scopus, BBO, SciELO, LILACS, IBECS and The Cochrane Library. In vitro studies evaluating the bond strength of universal adhesives to dentin and/or enamel by the etch-and-rinse and self-etch strategies were eligible to be selected. Statistical analyses were conducted using RevMan 5.1 (The Cochrane Collaboration, Copenhagen, Denmark). A global comparison was performed with random-effects models at a significance level of p<0.05. The analysis of dentin micro-tensile bond strength showed no statistically significant difference between the etch-and-rinse and self-etch strategies for mild universal adhesives (p≥0.05). However, for the ultra-mild All-Bond Universal adhesive, the etch-and-rinse strategy was significantly different than the self-etch mode in terms of dentin micro-tensile bond strength, as well as in the global analysis of enamel micro-tensile and micro-shear bond strength (p≤0.05). The enamel bond strength of universal adhesives is improved with prior phosphoric acid etching. However, this effect was not evident for dentin with the use of mild universal adhesives with the etch-and-rinse strategy. Selective enamel etching prior to the application of a mild universal adhesive is an advisable strategy for optimizing bonding. Copyright © 2015 Elsevier Ltd. All rights reserved.

Preparation of fluorescent mesoporous hollow silica-fullerene nanoparticles via selective etching for combined chemotherapy and photodynamic therapy

NASA Astrophysics Data System (ADS)

Yang, Yannan; Yu, Meihua; Song, Hao; Wang, Yue; Yu, Chengzhong

2015-07-01

Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy.Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02769a

Ion-beam nanopatterning: experimental results with chemically-assisted beam

NASA Astrophysics Data System (ADS)

Pochon, Sebastien C. R.

2018-03-01

The need for forming gratings (for example used in VR headsets) in materials such as SiO2 has seen a recent surge in the use of Ion beam etching techniques. However, when using an argon-only beam, the selectivity is limited as it is a physical process. Typically, gases such as CHF3, SF6, O2 and Cl2 can be added to argon in order to increase selectivity; depending on where the gas is injected, the process is known as Reactive Ion Beam Etching (RIBE) or Chemically Assisted Ion Beam Etching (CAIBE). The substrate holder can rotate in order to provide an axisymmetric etch rate profile. It can also be tilted over a range of angles to the beam direction. This enables control over the sidewall profile as well as radial uniformity optimisation. Ion beam directionality in conjunction with variable incident beam angle via platen angle setting enables profile control and feature shaping during nanopatterning. These hardware features unique to the Ion Beam etching methods can be used to create angled etch features. The CAIBE technique is also well suited to laser diode facet etch (for optoelectronic devices); these typically use III-V materials like InP. Here, we report on materials such as SiO2 etched without rotation and at a fixed platen angle allowing the formation of gratings and InP etched at a fixed angle with rotation allowing the formation of nanopillars and laser facets.

Advanced Simulation Technology to Design Etching Process on CMOS Devices

NASA Astrophysics Data System (ADS)

Kuboi, Nobuyuki

2015-09-01

Prediction and control of plasma-induced damage is needed to mass-produce high performance CMOS devices. In particular, side-wall (SW) etching with low damage is a key process for the next generation of MOSFETs and FinFETs. To predict and control the damage, we have developed a SiN etching simulation technique for CHxFy/Ar/O2 plasma processes using a three-dimensional (3D) voxel model. This model includes new concepts for the gas transportation in the pattern, detailed surface reactions on the SiN reactive layer divided into several thin slabs and C-F polymer layer dependent on the H/N ratio, and use of ``smart voxels''. We successfully predicted the etching properties such as the etch rate, polymer layer thickness, and selectivity for Si, SiO2, and SiN films along with process variations and demonstrated the 3D damage distribution time-dependently during SW etching on MOSFETs and FinFETs. We confirmed that a large amount of Si damage was caused in the source/drain region with the passage of time in spite of the existing SiO2 layer of 15 nm in the over etch step and the Si fin having been directly damaged by a large amount of high energy H during the removal step of the parasitic fin spacer leading to Si fin damage to a depth of 14 to 18 nm. By analyzing the results of these simulations and our previous simulations, we found that it is important to carefully control the dose of high energy H, incident energy of H, polymer layer thickness, and over-etch time considering the effects of the pattern structure, chamber-wall condition, and wafer open area ratio. In collaboration with Masanaga Fukasawa and Tetsuya Tatsumi, Sony Corporation. We thank Mr. T. Shigetoshi and Mr. T. Kinoshita of Sony Corporation for their assistance with the experiments.

Self-assembled titanium calcium oxide nanopatterns as versatile reactive nanomasks for dry etching lithographic transfer with high selectivity.

PubMed

Faustini, Marco; Drisko, Glenna L; Letailleur, Alban A; Montiel, Rafael Salas; Boissière, Cédric; Cattoni, Andrea; Haghiri-Gosnet, Anne Marie; Lerondel, Gilles; Grosso, David

2013-02-07

We report the simple preparation of ultra-thin self-assembled nanoperforated titanium calcium oxide films and their use as reactive nanomasks for selective dry etching of silicon. This novel reactive nanomask is composed of TiO(2) in which up to 50% of Ti was replaced by Ca (Ca(x)Ti(1-x)O(2-x)). The system was prepared by evaporation induced self-assembly of dip-coated solution of CaCl(2), TiCl(4) and poly(butadiene-block-ethylene oxide) followed by 5 min of thermal treatment at 500 °C in air. The mask exhibits enhanced selectivity by forming a CaF(2) protective layer in the presence of a chemically reactive fluorinated plasma. In particular it is demonstrated that ordered nano-arrays of dense Si pillars, or deep cylindrical wells, with high aspect ratio i.e. lateral dimensions as small as 20 nm and height up to 200 nm, can be formed. Both wells and pillars were formed by tuning the morphology and the homogeneity of the deposited mask. The mask preparation is extremely fast and simple, low-cost and easily scalable. Its combination with reactive ion etching constitutes one of the first examples of what can be achieved when sol-gel chemistry is coupled with top-down technologies. The resulting Si nanopatterns and nanostructures are of high interest for applications in many fields of nanotechnology including electronics and optics. This work extends and diversifies the toolbox of nanofabrication methods.

Suppression of low-frequency charge noise in gates-defined GaAs quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

You, Jie; Li, Hai-Ou, E-mail: haiouli@ustc.edu.cn, E-mail: gpguo@ustc.edu.cn; Wang, Ke

To reduce the charge noise of a modulation-doped GaAs/AlGaAs quantum dot, we have fabricated shallow-etched GaAs/AlGaAs quantum dots using the wet-etching method to study the effects of two-dimensional electron gas (2DEG) underneath the metallic gates. The low-frequency 1/f noise in the Coulomb blockade region of the shallow-etched quantum dot is compared with a non-etched quantum dot on the same wafer. The average values of the gate noise are approximately 0.5 μeV in the shallow-etched quantum dot and 3 μeV in the regular quantum dot. Our results show the quantum dot low-frequency charge noise can be suppressed by the removal ofmore » the 2DEG underneath the metallic gates, which provides an architecture for noise reduction.« less

Selective Processing Techniques for Electronics and Opto-Electronic Applications: Quantum-Well Devices and Integrated Optic Circuits

DTIC Science & Technology

1993-02-10

new technology is to have sufficient control of processing to *- describable by an appropriate elecromagnetic model . build useful devices. For example...3. W aveguide Modulators .................................. 7 B. Integrated Optical Device and Circuit Modeling ... ................... .. 10 C...following categories: A. Integrated Optical Devices and Technology B. Integrated Optical Device and Circuit Modeling C. Cryogenic Etching for Low

Spinodal Decomposition in Functionally Graded Super Duplex Stainless Steel and Weld Metal

NASA Astrophysics Data System (ADS)

Hosseini, Vahid A.; Thuvander, Mattias; Wessman, Sten; Karlsson, Leif

2018-07-01

Low-temperature phase separations (T < 500 °C), resulting in changes in mechanical and corrosion properties, of super duplex stainless steel (SDSS) base and weld metals were investigated for short heat treatment times (0.5 to 600 minutes). A novel heat treatment technique, where a stationary arc produces a steady state temperature gradient for selected times, was employed to fabricate functionally graded materials. Three different initial material conditions including 2507 SDSS, remelted 2507 SDSS, and 2509 SDSS weld metal were investigated. Selective etching of ferrite significantly decreased in regions heat treated at 435 °C to 480 °C already after 3 minutes due to rapid phase separations. Atom probe tomography results revealed spinodal decomposition of ferrite and precipitation of Cu particles. Microhardness mapping showed that as-welded microstructure and/or higher Ni content accelerated decomposition. The arc heat treatment technique combined with microhardness mapping and electrolytical etching was found to be a successful approach to evaluate kinetics of low-temperature phase separations in SDSS, particularly at its earlier stages. A time-temperature transformation diagram was proposed showing the kinetics of 475 °C-embrittlement in 2507 SDSS.

Spinodal Decomposition in Functionally Graded Super Duplex Stainless Steel and Weld Metal

NASA Astrophysics Data System (ADS)

Hosseini, Vahid A.; Thuvander, Mattias; Wessman, Sten; Karlsson, Leif

2018-04-01

Low-temperature phase separations (T < 500 °C), resulting in changes in mechanical and corrosion properties, of super duplex stainless steel (SDSS) base and weld metals were investigated for short heat treatment times (0.5 to 600 minutes). A novel heat treatment technique, where a stationary arc produces a steady state temperature gradient for selected times, was employed to fabricate functionally graded materials. Three different initial material conditions including 2507 SDSS, remelted 2507 SDSS, and 2509 SDSS weld metal were investigated. Selective etching of ferrite significantly decreased in regions heat treated at 435 °C to 480 °C already after 3 minutes due to rapid phase separations. Atom probe tomography results revealed spinodal decomposition of ferrite and precipitation of Cu particles. Microhardness mapping showed that as-welded microstructure and/or higher Ni content accelerated decomposition. The arc heat treatment technique combined with microhardness mapping and electrolytical etching was found to be a successful approach to evaluate kinetics of low-temperature phase separations in SDSS, particularly at its earlier stages. A time-temperature transformation diagram was proposed showing the kinetics of 475 °C-embrittlement in 2507 SDSS.

Growth and Stability of Titanium Dioxide Nanoclusters on Graphene/Ru(0001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frederick, Ryan T.; Novotny, Zbynek; Netzer, Falko P.

Titanium dioxide/graphene composites have recently been demonstrated to improve the photocatalytic activity of TiO2 in visible light. To better understand the interactions of TiO2 with graphene we have investigated the growth of TiO2 nanoclusters on single-layer graphene/Ru(0001) using scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). Deposition of Ti in the O2 background at 300 K resulted in the formation of nanoclusters nucleating on intrinsic defects in the graphene (Gr) layer. The saturation nanocluster density decreased as the substrate temperature was increased from 300 to 650 K, while deposition at 700 K resulted in the significant etching of themore » Gr layer. We have also prepared nanoclusters with Ti2O3 stoichiometry using lower O2 pressures at 650 K. Thermal stability of the TiO2 nanoclusters prepared at 300 K was evaluated with AES and STM. No change in oxidation state for the TiO2 nanoclusters or etching of the Gr layer was observed up to ~900 K. Annealing studies characterized using STM revealed that cluster ripening proceeds via a Smoluchowski mechanism below 800 K and that Ostwald ripening dominates above 800 K. At even higher temperatures, the nanoclusters undergo reduction to TiOx (x ≈ 1 - 1.5) which is accompanied by oxidation and etching of the Gr. Our studies demonstrate that highly thermally stable TiOx nanoclusters of controlled composition and morphology can be prepared on Gr supports.« less

Etching of enamel for direct bonding with a thulium fiber laser

NASA Astrophysics Data System (ADS)

Kabaş Sarp, Ayşe S.; Gülsoy, Murat

2011-03-01

Background: Laser etching of enamel for direct bonding can decrease the risk of surface enamel loss and demineralization which are the adverse effects of acid etching technique. However, in excess of +5.5°C can cause irreversible pulpal responses. In this study, a 1940- nm Thulium Fiber Laser in CW mode was used for laser etching. Aim: Determination of the suitable Laser parameters of enamel surface etching for direct bonding of ceramic brackets and keeping that intrapulpal temperature changes below the threshold value. Material and Method: Polycrystalline ceramic orthodontic brackets were bonded on bovine teeth by using 2 different kinds of etching techniques: Acid and Laser Etching. In addition to these 3 etched groups, there was also a group which was bonded without etching. Brackets were debonded with a material testing machine. Breaking time and the load at the breaking point were measured. Intrapulpal temperature changes were recorded by a K-type Thermocouple. For all laser groups, intrapulpal temperature rise was below the threshold value of 5.5°C. Results and Conclusion: Acid-etched group ( 11.73 MPa) significantly required more debonding force than 3- second- irradiated ( 5.03 MPa) and non-etched groups ( 3.4 MPa) but the results of acid etched group and 4- second- irradiated group (7.5 MPa) showed no significant difference. Moreover, 4- second irradiated group was over the minimum acceptable value for clinical use. Also, 3- second lasing caused a significant reduction in time according to acid-etch group. As a result, 1940- nm laser irradiation is a promising method for laser etching.

Computer program TRACK_TEST for calculating parameters and plotting profiles for etch pits in nuclear track materials

NASA Astrophysics Data System (ADS)

Nikezic, D.; Yu, K. N.

2006-01-01

A computer program called TRACK_TEST for calculating parameters (lengths of the major and minor axes) and plotting profiles in nuclear track materials resulted from light-ion irradiation and subsequent chemical etching is described. The programming steps are outlined, including calculations of alpha-particle ranges, determination of the distance along the particle trajectory penetrated by the chemical etchant, calculations of track coordinates, determination of the lengths of the major and minor axes and determination of the contour of the track opening. Descriptions of the program are given, including the built-in V functions for the two commonly employed nuclear track materials commercially known as LR 115 (cellulose nitrate) and CR-39 (poly allyl diglycol carbonate) irradiated by alpha particles. Program summaryTitle of the program:TRACK_TEST Catalogue identifier:ADWT Program obtainable from:CPC Program Library, Queen's University of Belfast, N. Ireland Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWT Computer:Pentium PC Operating systems:Windows 95+ Programming language:Fortran 90 Memory required to execute with typical data:256 MB No. of lines in distributed program, including test data, etc.: 2739 No. of bytes in distributed program, including test data, etc.:204 526 Distribution format:tar.gz External subprograms used:The entire code must be linked with the MSFLIB library Nature of problem: Fast heavy charged particles (like alpha particles and other light ions etc.) create latent tracks in some dielectric materials. After chemical etching in aqueous NaOH or KOH solutions, these tracks become visible under an optical microscope. The growth of a track is based on the simultaneous actions of the etchant on undamaged regions (with the bulk etch rate V) and along the particle track (with the track etch rate V). Growth of the track is described satisfactorily by these two parameters ( V and V). Several models have been presented in the past describing the track development, one of which is the model of Nikezic and Yu (2003) [D. Nikezic, K.N. Yu, Three-dimensional analytical determination of the track parameters. Over-etched tracks, Radiat. Meas. 37 (2003) 39-45] used in the present program. The present computer program has been written to calculate coordinates of points on the track wall and to determine other relevant track parameters. Solution method:Coordinates of points on the track wall assuming normal incidence were calculated by using the method as described by Fromm et al. (1988) [M. Fromm, A. Chambaudet, F. Membrey, Data bank for alpha particle tracks in CR39 with energies ranging from 0.5 to 5 MeV recording for various incident angles, Nucl. Tracks Radiat. Meas. 15 (1988) 115-118]. The track is then rotated through the incident angle in order to obtain the coordinates of the oblique track [D. Nikezic, K.N. Yu, Three-dimensional analytical determination of the track parameters. Over-etched tracks, Radiat. Meas. 37 (2003) 39-45; D. Nikezic, Three dimensional analytical determination of the track parameters, Radiat. Meas. 32 (2000) 277-282]. In this way, the track profile in two dimensions (2D) was obtained. In the next step, points in the track wall profile are rotated around the particle trajectory. In this way, circles that outline the track in three dimensions (3D) are obtained. The intersection between the post-etching surface of the detector and the 3D track is the track opening (or the track contour). Coordinates of the track 2D and 3D profiles and the track opening are saved in separate output data files. Restrictions: The program cannot calculate track parameters for the incident angle of exactly 90°. The alpha-particle energy should be smaller than 10 MeV. Furthermore, the program cannot perform calculations for tracks in some extreme cases, such as for very low incident energies or very small incident angles. Additional comments: This is a freeware, but publications arising from using this program should cite the present paper and the paper describing the track growth model [D. Nikezic, K.N. Yu, Three-dimensional analytical determination of the track parameters. Over-etched tracks, Radiat. Meas. 37 (2003) 39-45]. Moreover, the references for the V functions used should also be cited. For the CR-39 detector: Function (1): S.A. Durrani, R.K. Bull, Solid State Nuclear Track Detection. Principles, Methods and Applications, Pergamon Press, 1987. Function (2): C. Brun, M. Fromm, M. Jouffroy, P. Meyer, J.E. Groetz, F. Abel, A. Chambaudet, B. Dorschel, D. Hermsdorf, R. Bretschneider, K. Kadner, H. Kuhne, Intercomparative study of the detection characteristics of the CR-39 SSNTD for light ions: Present status of the Besancon-Dresden approaches, Radiat. Meas. 31 (1999) 89-98. Function (3): K.N. Yu, F.M.F. Ng, D. Nikezic, Measuring depths of sub-micron tracks in a CR-39 detector from replicas using atomic force microscopy, Radiat. Meas. 40 (2005) 380-383. For the LR 115 detector: Function (1): S.A. Durrani, P.F. Green, The effect of etching conditions on the response of LR 115, Nucl. Tracks 8 (1984) 21-24. Function (2): C.W.Y. Yip, D. Nikezic, J.P.Y Ho, K.N. Yu, Chemical etching characteristics for cellulose nitrate, Mat. Chem. Phys. 95 (2005) 307-312. Running time: Order of several minutes, dependent on input parameters and the resolution requested by the user.

Damage-Free Smooth-Sidewall InGaAs Nanopillar Array by Metal-Assisted Chemical Etching.

PubMed

Kong, Lingyu; Song, Yi; Kim, Jeong Dong; Yu, Lan; Wasserman, Daniel; Chim, Wai Kin; Chiam, Sing Yang; Li, Xiuling

2017-10-24

Producing densely packed high aspect ratio In 0.53 Ga 0.47 As nanostructures without surface damage is critical for beyond Si-CMOS nanoelectronic and optoelectronic devices. However, conventional dry etching methods are known to produce irreversible damage to III-V compound semiconductors because of the inherent high-energy ion-driven process. In this work, we demonstrate the realization of ordered, uniform, array-based In 0.53 Ga 0.47 As pillars with diameters as small as 200 nm using the damage-free metal-assisted chemical etching (MacEtch) technology combined with the post-MacEtch digital etching smoothing. The etching mechanism of In x Ga 1-x As is explored through the characterization of pillar morphology and porosity as a function of etching condition and indium composition. The etching behavior of In 0.53 Ga 0.47 As, in contrast to higher bandgap semiconductors (e.g., Si or GaAs), can be interpreted by a Schottky barrier height model that dictates the etching mechanism constantly in the mass transport limited regime because of the low barrier height. A broader impact of this work relates to the complete elimination of surface roughness or porosity related defects, which can be prevalent byproducts of MacEtch, by post-MacEtch digital etching. Side-by-side comparison of the midgap interface state density and flat-band capacitance hysteresis of both the unprocessed planar and MacEtched pillar In 0.53 Ga 0.47 As metal-oxide-semiconductor capacitors further confirms that the surface of the resultant pillars is as smooth and defect-free as before etching. MacEtch combined with digital etching offers a simple, room-temperature, and low-cost method for the formation of high-quality In 0.53 Ga 0.47 As nanostructures that will potentially enable large-volume production of In 0.53 Ga 0.47 As-based devices including three-dimensional transistors and high-efficiency infrared photodetectors.

Selective etching of injection molded zirconia-toughened alumina: Towards osseointegrated and antibacterial ceramic implants.

PubMed

Flamant, Quentin; Caravaca, Carlos; Meille, Sylvain; Gremillard, Laurent; Chevalier, Jérôme; Biotteau-Deheuvels, Katia; Kuntz, Meinhard; Chandrawati, Rona; Herrmann, Inge K; Spicer, Christopher D; Stevens, Molly M; Anglada, Marc

2016-12-01

Due to their outstanding mechanical properties and excellent biocompatibility, zirconia-toughened alumina (ZTA) ceramics have become the gold standard in orthopedics for the fabrication of ceramic bearing components over the last decade. However, ZTA is bioinert, which hampers its implantation in direct contact with bone. Furthermore, periprosthetic joint infections are now the leading cause of failure for joint arthroplasty prostheses. To address both issues, an improved surface design is required: a controlled micro- and nano-roughness can promote osseointegration and limit bacterial adhesion whereas surface porosity allows loading and delivery of antibacterial compounds. In this work, we developed an integrated strategy aiming to provide both osseointegrative and antibacterial properties to ZTA surfaces. The micro-topography was controlled by injection molding. Meanwhile a novel process involving the selective dissolution of zirconia (selective etching) was used to produce nano-roughness and interconnected nanoporosity. Potential utilization of the porosity for loading and delivery of antibiotic molecules was demonstrated, and the impact of selective etching on mechanical properties and hydrothermal stability was shown to be limited. The combination of injection molding and selective etching thus appears promising for fabricating a new generation of ZTA components implantable in direct contact with bone. Zirconia-toughened alumina (ZTA) is the current gold standard for the fabrication of orthopedic ceramic components. In the present work, we propose an innovative strategy to provide both osseointegrative and antibacterial properties to ZTA surfaces: we demonstrate that injection molding allows a flexible design of surface micro-topography and can be combined with selective etching, a novel process that induces nano-roughness and surface interconnected porosity without the need for coating, avoiding reliability issues. These surface modifications have the potential to improve osseointegration. Furthermore, our results show that the porosity can be used for drug delivery and suggest that the etched surface could reduce bacterial adhesion. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The influence of Y-TZP surface treatment on topography and ceramic/resin cement interfacial fracture toughness.

PubMed

Paes, P N G; Bastian, F L; Jardim, P M

2017-09-01

Consider the efficacy of glass infiltration etching (SIE) treatment as a procedure to modify the zirconia surface resulting in higher interfacial fracture toughness. Y-TZP was subjected to 5 different surface treatments conditions consisting of no treatment (G1), SIE followed by hydrofluoric acid treatment (G2), heat treated at 750°C (G3), hydrofluoric acid treated (G4) and airborne-particle abrasion with alumina particles (G5). The effect of surface treatment on roughness was evaluated by Atomic Force Microscopy providing three different parameters: R a , R sk and surface area variation. The ceramic/resin cement interface was analyzed by Fracture Mechanics K I test with failure mode determined by fractographic analysis. Weibull's analysis was also performed to evaluate the structural integrity of the adhesion zone. G2 and G4 specimens showed very similar, and high R a values but different surface area variation (33% for G2 and 13% for G4) and they presented the highest fracture toughness (K IC ). Weibull's analysis showed G2 (SIE) tendency to exhibit higher K IC values than the other groups but with more data scatter and a higher early failure probability than G4 specimens. Selective glass infiltration etching surface treatment was effective in modifying the zirconia surface roughness, increasing the bonding area and hence the mechanical imbrications at the zirconia/resin cement interface resulting in higher fracture toughness (K IC ) values with higher K IC values obtained when failure probability above 20% was expected (Weibull's distribution) among all the experimental groups. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Selective Growth of Metallic and Semiconducting Single Walled Carbon Nanotubes on Textured Silicon.

PubMed

Jang, Mira; Lee, Jongtaek; Park, Teahee; Lee, Junyoung; Yang, Jonghee; Yi, Whikun

2016-03-01

We fabricated the etched Si substrate having the pyramidal pattern size from 0.5 to 4.2 μm by changing the texturing process parameters, i.e., KOH concentration, etching time, and temperature. Single walled carbon nanotubes (SWNTs) were then synthesized on the etched Si substrates with different pyramidal pattern by chemical vapor deposition. We investigated the optical and electronic properties of SWNT film grown on the etched Si substrates of different morphology by using scanning electron microscopy, Raman spectroscopy and conducting probe atomic force microscopy. We confirmed that the morphology of substrate strongly affected the selective growth of the SWNT film. Semiconducting SWNTs were formed on larger pyramidal sized Si wafer with higher ratio compared with SWNTs on smaller pyramidal sized Si.

Atmospheric-pressure plasma jet system for silicon etching without fluorocarbon gas feed

NASA Astrophysics Data System (ADS)

Ohtsu, Yasunori; Nagamatsu, Kenta

2018-01-01

We developed an atmospheric-pressure plasma jet (APPJ) system with a tungsten rod electrode coated with C2F4 particles of approximately 0.3 µm diameter for the surface treatment of a silicon wafer. The APPJ was generated by dielectric barrier discharge with a driving frequency of 22 kHz using a He gas flow. The characteristics of the APPJ were examined under various experimental conditions. The plasma jet length increased proportionally to the electric field. It was found that the treatment area of the silicon wafer was approximately 1 mm in diameter. By atomic force microscopy analysis, minute irregularities with a maximum length of about 600 nm and part of a ring-shaped trench were observed. A Si etching rate of approximately 400 nm/min was attained at a low power of 6 W and a He flow rate of 1 L/min without introducing molecular gas including F atoms.

Development of a polysilicon process based on chemical vapor deposition, phase 1 and phase 2

NASA Technical Reports Server (NTRS)

Plahutnik, F.; Arvidson, A.; Sawyer, D.; Sharp, K.

1982-01-01

High-purity polycrystalline silicon was produced in an experimental, intermediate and advanced CVD reactor. Data from the intermediate and advanced reactors confirmed earlier results obtained in the experimental reactor. Solar cells were fabricated by Westinghouse Electric and Applied Solar Research Corporation which met or exceeded baseline cell efficiencies. Feedstocks containing trichlorosilane or silicon tetrachloride are not viable as etch promoters to reduce silicon deposition on bell jars. Neither are they capable of meeting program goals for the 1000 MT/yr plant. Post-run CH1 etch was found to be a reasonably effective method of reducing silicon deposition on bell jars. Using dichlorosilane as feedstock met the low-cost solar array deposition goal (2.0 gh-1-cm-1), however, conversion efficiency was approximately 10% lower than the targeted value of 40 mole percent (32 to 36% achieved), and power consumption was approximately 20 kWh/kg over target at the reactor.

Size-focusing synthesis of gold nanoclusters with p-mercaptobenzoic acid.

PubMed

Tvedte, Laura M; Ackerson, Christopher J

2014-09-18

Etching or size-focusing methods are now widespread for preparation of atomically monodisperse thiolate-protected gold nanoparticles. Size-focusing methods are not widespread, however, in the production of water-soluble gold nanoparticles. Reported here is a new method for size-focusing of large gold nanoparticles utilizing p-mercaptobenzoic acid. We observe preferential formation of three large gold nanoparticles with approximate masses of 23, 51, and 88 kDa. On the basis of the stability of these masses against further etching or growth, they appear to be especially stable sizes. These sizes are not prominent after etching challenges with organosoluble ligands, and the 51 and 88 kDa sizes appear to be novel stable thiolate-protected gold cluster sizes. The overall trend in particle size distribution over time is also unusual, with larger sizes dominating at longer time points.

Low-loss slot waveguides with silicon (111) surfaces realized using anisotropic wet etching

NASA Astrophysics Data System (ADS)

Debnath, Kapil; Khokhar, Ali; Boden, Stuart; Arimoto, Hideo; Oo, Swe; Chong, Harold; Reed, Graham; Saito, Shinichi

2016-11-01

We demonstrate low-loss slot waveguides on silicon-on-insulator (SOI) platform. Waveguides oriented along the (11-2) direction on the Si (110) plane were first fabricated by a standard e-beam lithography and dry etching process. A TMAH based anisotropic wet etching technique was then used to remove any residual side wall roughness. Using this fabrication technique propagation loss as low as 3.7dB/cm was realized in silicon slot waveguide for wavelengths near 1550nm. We also realized low propagation loss of 1dB/cm for silicon strip waveguides.

Smart Pixels for Optical Processing and Communications: Design, Models, Fabrication and Test

DTIC Science & Technology

1998-06-01

11.3 Mobility-Lifetime Product 115 11.4 P-IforVCSEL 116 Chapter 12: Developing a Reliable Etch 12.1 Etch Rates and Selectivity for Citric Acid 126...eGa0.4As etch-stop layer beneath the GaAs buffer. The gate recess was performed with a timed citric acid / hydrogen peroxide wet etch. The conducting...alkalinity. The wet etchant tested in this effort was a citric acid / hydrogen peroxide mixture,8൓ due to its availability, ease of preparation

Selective etching of InGaAs/GaAs(100) multilayers of quantum-dot chains

NASA Astrophysics Data System (ADS)

Wang, Zh. M.; Zhang, L.; Holmes, K.; Salamo, G. J.

2005-04-01

We report selective chemical etching as a promising procedure to study the buried quantum dots in multiple InGaAs/GaAs layers. The dot layer-by-dot layer etching is demonstrated using a mixed solution of NH4OH:H2O2:H2O. Regular plan-view atomic force microscopy reveals that all of the exposed InGaAs layers have a chain-like lateral ordering despite the potential of significant In-Ga intermixing during capping. The vertical self-correlation of quantum dots in the chains is observed.

Fabrication of precision high quality facets on molecular beam epitaxy material

DOEpatents

Petersen, Holly E.; Goward, William D.; Dijaili, Sol P.

2001-01-01

Fabricating mirrored vertical surfaces on semiconductor layered material grown by molecular beam epitaxy (MBE). Low energy chemically assisted ion beam etching (CAIBE) is employed to prepare mirrored vertical surfaces on MBE-grown III-V materials under unusually low concentrations of oxygen in evacuated etching atmospheres of chlorine and xenon ion beams. UV-stabilized smooth-surfaced photoresist materials contribute to highly vertical, high quality mirrored surfaces during the etching.

Selective Etching via Soft Lithography of Conductive Multilayered Gold Films with Analysis of Electrolyte Solutions

ERIC Educational Resources Information Center

Gerber, Ralph W.; Oliver-Hoyo, Maria T.

2008-01-01

This experiment is designed to expose undergraduate students to the process of selective etching by using soft lithography and the resulting electrical properties of multilayered films fabricated via self-assembly of gold nanoparticles. Students fabricate a conductive film of gold on glass, apply a patterned resist using a polydimethylsiloxane…

Enlargement of halloysite clay nanotube lumen by selective etching of aluminum oxide.

PubMed

Abdullayev, Elshad; Joshi, Anupam; Wei, Wenbo; Zhao, Yafei; Lvov, Yuri

2012-08-28

Halloysite clay tubes have 50 nm diameter and chemically different inner and outer walls (inner surface of aluminum oxide and outer surface of silica). Due to this different chemistry, the selective etching of alumina from inside the tube was realized, while preserving their external diameter (lumen diameter changed from 15 to 25 nm). This increases 2-3 times the tube lumen capacity for loading and further sustained release of active chemical agents such as metals, corrosion inhibitors, and drugs. In particular, halloysite loading efficiency for the benzotriazole increased 4 times by selective etching of 60% alumina within the tubes' lumens. Specific surface area of the tubes increased over 6 times, from 40 to 250 m(2)/g, upon acid treatment.

Photoelectrochemical fabrication of spectroscopic diffraction gratings, phase 2

NASA Technical Reports Server (NTRS)

Rauh, R. David; Carrabba, Michael M.; Li, Jianguo; Cartland, Robert F.; Hachey, John P.; Mathew, Sam

1990-01-01

This program was directed toward the production of Echelle diffraction gratings by a light-driven, electrochemical etching technique (photoelectrochemical etching). Etching is carried out in single crystal materials, and the differential rate of etching of the different crystallographic planes used to define the groove profiles. Etching of V-groove profiles was first discovered by us during the first phase of this project, which was initially conceived as a general exploration of photoelectrochemical etching techniques for grating fabrication. This highly controllable V-groove etching process was considered to be of high significance for producing low pitch Echelles, and provided the basis for a more extensive Phase 2 investigation.

Spray-coated single walled carbon nanotubes as source and drain electrodes in SnO thin-film transistors

NASA Astrophysics Data System (ADS)

Ryu, Jae Hyeon; Baek, Geun-Woo; Kim, Seung Yeob; Kwon, Hyuck-In; Jin, Sung Hun

2018-07-01

In this letter, spray-coated single walled carbon nanotubes (SWNTs) as one of alternative electrodes in SnO thin-film transistors are demonstrated for emerging electronic applications. Herein, the device architecture of SnO TFTs with a polymer etch stop layer (SU-8) enables the selective etching of SWNTs in a desired region without the detrimental effects of SnO channel layers. Moreover, SnO TFTs with SWNT electrodes as substitutes successfully demonstrate decent width normalized electrical contact properties (∼1.49 kΩ cm), field effect mobility (∼0.69 cm2 V‑1 s‑1), sub-threshold slope (∼0.4 V dec‑1), and current on–off ratio (I on/I off ∼ 3.5 × 103). Systematic temperature dependency measurements elucidate that SnO channel transports with an activation energy within several tens of meV, together with decent contact resistance as compared to that of conventional Ni electrodes.

Highly selective SiO2 etching over Si3N4 using a cyclic process with BCl3 and fluorocarbon gas chemistries

NASA Astrophysics Data System (ADS)

Matsui, Miyako; Kuwahara, Kenichi

2018-06-01

A cyclic process for highly selective SiO2 etching with atomic-scale precision over Si3N4 was developed by using BCl3 and fluorocarbon gas chemistries. This process consists of two alternately performed steps: a deposition step using BCl3 mixed-gas plasma and an etching step using CF4/Ar mixed-gas plasma. The mechanism of the cyclic process was investigated by analyzing the surface chemistry at each step. BCl x layers formed on both SiO2 and Si3N4 surfaces in the deposition step. Early in the etching step, the deposited BCl x layers reacted with CF x radicals by forming CCl x and BF x . Then, fluorocarbon films were deposited on both surfaces in the etching step. We found that the BCl x layers formed in the deposition step enhanced the formation of the fluorocarbon films in the CF4 plasma etching step. In addition, because F radicals that radiated from the CF4 plasma reacted with B atoms while passing through the BCl x layers, the BCl x layers protected the Si3N4 surface from F-radical etching. The deposited layers, which contained the BCl x , CCl x , and CF x components, became thinner on SiO2 than on Si3N4, which promoted the ion-assisted etching of SiO2. This is because the BCl x component had a high reactivity with SiO2, and the CF x component was consumed by the etching reaction with SiO2.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzler, Dominik; Oehrlein, Gottlieb S., E-mail: oehrlein@umd.edu; Li, Chen

The need for atomic layer etching (ALE) is steadily increasing as smaller critical dimensions and pitches are required in device patterning. A flux-control based cyclic Ar/C{sub 4}F{sub 8} ALE based on steady-state Ar plasma in conjunction with periodic, precise C{sub 4}F{sub 8} injection and synchronized plasma-based low energy Ar{sup +} ion bombardment has been established for SiO{sub 2} [Metzler et al., J. Vac. Sci. Technol. A 32, 020603 (2014)]. In this work, the cyclic process is further characterized and extended to ALE of silicon under similar process conditions. The use of CHF{sub 3} as a precursor is examined and comparedmore » to C{sub 4}F{sub 8}. CHF{sub 3} is shown to enable selective SiO{sub 2}/Si etching using a fluorocarbon (FC) film build up. Other critical process parameters investigated are the FC film thickness deposited per cycle, the ion energy, and the etch step length. Etching behavior and mechanisms are studied using in situ real time ellipsometry and x-ray photoelectron spectroscopy. Silicon ALE shows less self-limitation than silicon oxide due to higher physical sputtering rates for the maximum ion energies used in this work, ranged from 20 to 30 eV. The surface chemistry is found to contain fluorinated silicon oxide during the etching of silicon. Plasma parameters during ALE are studied using a Langmuir probe and establish the impact of precursor addition on plasma properties.« less

Inductively coupled BCl 3/Cl 2 /Ar plasma etching of Al-rich AlGaN

DOE PAGES

Douglas, Erica A.; Sanchez, Carlos A.; Kaplar, Robert J.; ...

2016-12-01

Varying atomic ratios in compound semiconductors is well known to have large effects on the etching properties of the material. The use of thin device barrier layers, down to 25 nm, adds to the fabrication complexity by requiring precise control over etch rates and surface morphology. The effects of bias power and gas ratio of BCl 3 to Cl 2 for inductively coupled plasma etching of high Al content AlGaN were contrasted with AlN in this study for etch rate, selectivity, and surface morphology. Etch rates were greatly affected by both bias power and gas chemistry. Here we detail themore » effects of small variations in Al composition for AlGaN and show substantial changes in etch rate with regards to bias power as compared to AlN.« less

Characterization and modeling of low energy ion-induced damage in III-V semiconductors

NASA Astrophysics Data System (ADS)

Chen, Ching-Hui

1997-11-01

Low energy ion-induced damage (sub-keV) created during dry etching processes can extend quite deeply into materials. A systematic study on the deep penetration of dry etch-induced damage is necessary to improve device performance and helpful in further understanding the nature of defect propagation in semiconductors. In this study, a phenomenological model of dry etching damage that includes both effects of ion channeling and defect diffusion has been developed. It underscores that in addition to ion channeling, enhanced defect diffusion also plays an important role in establishing the damage profile. Further, the enhanced diffusion of dry etch- induced damage was experimentally observed for the first time by investigating the influences of concurrent above- bandgap laser illumination and low energy Ar+ ion bombardment on the damage profiles of GaAs/AlGaAs and InP-GaAs/InP heterostructures. The results indicate that non-radiative recombination of electron and hole pairs at defect sites is responsible for the observed radiation enhanced diffusion. DLTS measurements are also employed to characterize the nature of the enhanced diffusion in n-GaAs and reveal that a major component of the ion- induced defects is associated with primary point defects. Using the better understanding of the damage propagation in dry etched materials, a thin layer of low temperature grown GaAs (~200A) was utilized to stop defect propagation during dry etching process. This approach has been successfully applied to reduce ion damage that would occur during the formation of a dry-etch gate recess of a high electron mobility transistor. Finally, some future experiments are proposed and conceptually described, which would further clarify some of the many outstanding issues in the understanding and mitigation of etch- induced damage.

Pattern sampling for etch model calibration

NASA Astrophysics Data System (ADS)

Weisbuch, François; Lutich, Andrey; Schatz, Jirka

2017-06-01

Successful patterning requires good control of the photolithography and etch processes. While compact litho models, mainly based on rigorous physics, can predict very well the contours printed in photoresist, pure empirical etch models are less accurate and more unstable. Compact etch models are based on geometrical kernels to compute the litho-etch biases that measure the distance between litho and etch contours. The definition of the kernels as well as the choice of calibration patterns is critical to get a robust etch model. This work proposes to define a set of independent and anisotropic etch kernels -"internal, external, curvature, Gaussian, z_profile" - designed to capture the finest details of the resist contours and represent precisely any etch bias. By evaluating the etch kernels on various structures it is possible to map their etch signatures in a multi-dimensional space and analyze them to find an optimal sampling of structures to train an etch model. The method was specifically applied to a contact layer containing many different geometries and was used to successfully select appropriate calibration structures. The proposed kernels evaluated on these structures were combined to train an etch model significantly better than the standard one. We also illustrate the usage of the specific kernel "z_profile" which adds a third dimension to the description of the resist profile.

Inductively coupled plasma etching of GaAs low loss waveguides for a traveling waveguide polarization converter, using chlorine chemistry

NASA Astrophysics Data System (ADS)

Lu, J.; Meng, X.; Springthorpe, A. J.; Shepherd, F. R.; Poirier, M.

2004-05-01

A traveling waveguide polarization converter [M. Poirier et al.] has been developed, which involves long, low loss, weakly confined waveguides etched in GaAs (epitaxially grown by molecular beam epitaxy), with electroplated ``T electrodes'' distributed along the etched floor adjacent to the ridge walls, and airbridge interconnect metallization. This article describes the development of the waveguide fabrication, based on inductively coupled plasma (ICP) etching of GaAs using Cl2 chemistry; the special processes required to fabricate the electrodes and metallization [X. Meng et al.], and the device characteristics [M. Poirier et al.], are described elsewhere. The required waveguide has dimensions nominally 4 μm wide and 2.1 μm deep, with dimensional tolerances ~0.1 μm across the wafer and wafer to wafer. A vertical etch profile with very smooth sidewalls and floors is required to enable the plated metal electrodes to be fabricated within 0.1 μm of the ridge. The ridges were fabricated using Cl2 ICP etching and a photoresist mask patterned with an I-line stepper; He backside cooling, combined with an electrostatic chuck, was employed to ensure good heat transfer to prevent resist reticulation. The experimental results showed that the ridge profile is very sensitive to ICP power and platen rf power. High ICP power and low platen power tend to result in more isotropic etching, whereas increasing platen power increases the photoresist etch rate, which causes rougher ridge sidewalls. No strong dependence of GaAs etch rate and ridge profile were observed with small changes in process temperature (chuck temperature). However, when the chuck temperature was decreased from 25 to 0 °C, etch uniformity across a 3 in. wafer improved from 6% to 3%. Photoresist and polymer residues present after the ICP etch were removed using a combination of wet and dry processes. .

Low energy electron irradiation induced carbon etching: Triggering carbon film reacting with oxygen from SiO{sub 2} substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Cheng; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060; Wang, Chao, E-mail: cwang367@szu.edu.cn, E-mail: dfdiao@szu.edu.cn

2016-08-01

We report low-energy (50–200 eV) electron irradiation induced etching of thin carbon films on a SiO{sub 2} substrate. The etching mechanism was interpreted that electron irradiation stimulated the dissociation of the carbon film and SiO{sub 2}, and then triggered the carbon film reacting with oxygen from the SiO{sub 2} substrate. A requirement for triggering the etching of the carbon film is that the incident electron penetrates through the whole carbon film, which is related to both irradiation energy and film thickness. This study provides a convenient electron-assisted etching with the precursor substrate, which sheds light on an efficient pathway to themore » fabrication of nanodevices and nanosurfaces.« less

Bond efficacy and interface morphology of self-etching adhesives to ground enamel.

PubMed

Abdalla, Ali I; El Zohairy, Ahmed A; Abdel Mohsen, Mohamed M; Feilzer, Albert J

2010-02-01

This study compared the microshear bond strengths to ground enamel of three one-step self-etching adhesive systems, a self-etching primer system and an etch-and-rinse adhesive system. Three self-etching adhesives, Futurabond DC (Voco), Clearfil S Tri Bond (Kuraray) and Hybrid bond (Sun-Medical), a self-etching primer, Clearfil SE Bond (Kuraray), and an etch-and-rinse system, Admira Bond (Voco), were selected. Thirty human molars were used. The root of each tooth was removed and the crown was sectioned into halves. The convex enamel surfaces were reduced by polishing on silicone paper to prepare a flat surface. The bonding systems were applied on this surface. Prior to adhesive curing, a hollow cylinder (2.0 mm height/0.75 mm internal diameter) was placed on the treated surfaces. A resin composite was then inserted into the tube and cured. After water storage for 24 h, the tube was removed and shear bond strength was determined in a universal testing machine at a crosshead speed of 0.5 mm/min. The results were analyzed with ANOVA and the Tukey.-Kramer test at a 59 degrees confidence level. The enamel of five additional teeth was ground, and the etching component of each adhesive was applied and removed with absolute ethanol instead of being light cured. These teeth and selected fractured surfaces were examined by SEM. Adhesion to ground enamel of the Futurabond DC (25 +/- 3.5 MPa) and Clearfil SE Bond (23 +/- 2.9 MPa) self-etching systems was not significantly different from the etch-and-rinse system Admira Bond (27 +/- 2.3 MPa). The two self-etching adhesives Clearfil S Tri bond and Hybrid Bond demonstrated significantly lower bond strengths (14 +/- 1.4 MPa; 11 +/- 1.9 MPa) with no significant differences between them (p < 0.05). Bond strengths to ground enamel of self-etching adhesive systems are dependent on the type of adhesive system. Some of the new adhesive systems showed bond strength values comparable to that of etch-and-rinse systems. There was no correlation between bond strength and morphological changes in enamel.

A Low NO(x) Lean-Direct Injection, Multipoint Integrated Module Combuster Concept for Advanced Aircraft Gas Turbines

NASA Technical Reports Server (NTRS)

Tacina, Robert; Wey, Changlie; Laing, Peter; Mansour, Adel

2002-01-01

A low NO(x) emissions combustor has been demonstrated in flame-tube tests. A multipoint, lean-direct injection concept was used. Configurations were tested that had 25- and 36- fuel injectors in the size of a conventional single fuel injector. An integrated-module approach was used for the construction where chemically etched laminates, diffusion bonded together, combine the fuel injectors, air swirlers and fuel manifold into a single element. Test conditions were inlet temperatures up to 810 K, inlet pressures up to 2760 kPa, and flame temperatures up to 2100 K. A correlation was developed relating the NO(x) emissions with the inlet temperature, inlet pressure, fuel-air ratio and pressure drop. Assuming that 10 percent of the combustion air would be used for liner cooling and using a hypothetical engine cycle, the NO(x) emissions using the correlation from flame-tube tests were estimated to be less than 20 percent of the 1996 ICAO standard.

Fabrication of sub-diffraction-limit molecular structures by scanning near-field photolithography

NASA Astrophysics Data System (ADS)

Ducker, Robert E.; Montague, Matthew T.; Sun, Shuqing; Leggett, Graham J.

2007-09-01

Using a scanning near-field optical microscope coupled to a UV laser, an approach we term scanning near-field photolithography (SNP), structures as small as 9 nm (ca. λ/30) may be fabricated in self-assembled monolayers of alkanethiols on gold surfaces. Selective exposure of the adsorbate molecules in the near field leads to photoconversion of the alkylthiolate to a weakly bound alkylsulfonate which may be displaced readily be a contrasting thiol, leading to a chemical pattern, or used as a resist for the selective etching of the underlying metal. A novel ultra-mild etch for gold is reported, and used to etch structures as small as 9 nm. Photopatterning of oligo(ethylene glycol) (OEG) terminated selfassembled monolayers facilitates the fabrication of biomolecular nanostructures. Selective removal of the protein-resistant OEG terminated adsorbates created regions that may be functionalized with a second thiol and derivatized with a biomolecule. Finally, the application of SNP to nanopatterning on oxide surfaces is demonstrated. Selective exposure of monolayers of phosphonic acids adsorbed onto aluminum oxide leads to cleavage of the P-C bond and desorption of the adsorbate molecule. Subsequent etching, using aqueous based, yields structures as small as 100 nm.

Characteristics of pulsed dual frequency inductively coupled plasma

NASA Astrophysics Data System (ADS)

Seo, Jin Seok; Kim, Kyoung Nam; Kim, Ki Seok; Kim, Tae Hyung; Yeom, Geun Young

2015-01-01

To control the plasma characteristics more efficiently, a dual antenna inductively coupled plasma (DF-ICP) source composed of a 12-turn inner antenna operated at 2 MHz and a 3-turn outer antenna at 13.56 MHz was pulsed. The effects of pulsing to each antenna on the change of plasma characteristics and SiO2 etch characteristics using Ar/C4F8 gas mixtures were investigated. When the duty percentage was decreased from continuous wave (CW) mode to 30% for the inner or outer ICP antenna, decrease of the average electron temperature was observed for the pulsing of each antenna. Increase of the CF2/F ratio was also observed with decreasing duty percentage of each antenna, indicating decreased dissociation of the C4F8 gas due to the decreased average electron temperature. When SiO2 etching was investigated as a function of pulse duty percentage, increase of the etch selectivity of SiO2 over amorphous carbon layer (ACL) was observed while decreasing the SiO2 etch rate. The increase of etch selectivity was related to the change of gas dissociation characteristics, as observed by the decrease of average electron temperature and consequent increase of the CF2/F ratio. The decrease of the SiO2 etch rate could be compensated for by using the rf power compensated mode, that is, by maintaining the same time-average rf power during pulsing, instead of using the conventional pulsing mode. Through use of the power compensated mode, increased etch selectivity of SiO2/ACL similar to the conventional pulsing mode could be observed without significant decrease of the SiO2 etch rate. Finally, by using the rf power compensated mode while pulsing rf powers to both antennas, the plasma uniformity over the 300 mm diameter substrate could be improved from 7% for the CW conditions to about around 3.3% with the duty percentage of 30%.

Template-free fabrication of silicon micropillar/nanowire composite structure by one-step etching

PubMed Central

2012-01-01

A template-free fabrication method for silicon nanostructures, such as silicon micropillar (MP)/nanowire (NW) composite structure is presented. Utilizing an improved metal-assisted electroless etching (MAEE) of silicon in KMnO4/AgNO3/HF solution and silicon composite nanostructure of the long MPs erected in the short NWs arrays were generated on the silicon substrate. The morphology evolution of the MP/NW composite nanostructure and the role of self-growing K2SiF6 particles as the templates during the MAEE process were investigated in detail. Meanwhile, a fabrication mechanism based on the etching of silver nanoparticles (catalyzed) and the masking of K2SiF6 particles is proposed, which gives guidance for fabricating different silicon nanostructures, such as NW and MP arrays. This one-step method provides a simple and cost-effective way to fabricate silicon nanostructures. PMID:23043719

High-Si content BARC for dual-BARC systems such as trilayer patterning

NASA Astrophysics Data System (ADS)

Kennedy, Joseph; Xie, Song-Yuan; Wu, Ze-Yu; Katsanes, Ron; Flanigan, Kyle; Lee, Kevin; Slezak, Mark; Liu, Zhi; Lin, Shang-Ho

2009-03-01

This work discusses the requirements and performance of Honeywell's middle layer material, UVAS, for tri-layer patterning. UVAS is a high Si content polymer synthesized directly from Si containing starting monomer components. The monomers are selected to produce a film that meets the requirements as a middle layer for tri-layer patterning (TLP) and gives us a level of flexibility to adjust the properties of the film to meet the customer's specific photoresist and patterning requirements. Results of simulations of the substrate reflectance versus numerical aperture, UVAS thickness, and under layer film are presented. ArF photoresist line profiles and process latitude versus UVAS bake at temperatures as low as 150ºC are presented and discussed. Immersion lithographic patterning of ArF photoresist line space and contact hole features will be presented. A sequence of SEM images detailing the plasma etch transfer of line space photoresist features through the middle and under layer films comprising the TLP film stack will be presented. Excellent etch selectivity between the UVAS and the organic under layer film exists as no edge erosion or faceting is observed as a result of the etch process. A detailed study of the impact of a PGMEA solvent photoresist rework process on the lithographic process window of a TLP film stack was performed with the results indicating that no degradation to the UVAS film occurs.

Molecular dynamics simulations of Si etching in Cl- and Br-based plasmas: Cl{sup +} and Br{sup +} ion incidence in the presence of Cl and Br neutrals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakazaki, Nobuya, E-mail: nakazaki.nobuya.58x@st.kyoto-u.ac.jp; Takao, Yoshinori; Eriguchi, Koji

Classical molecular dynamics (MD) simulations have been performed for Cl{sup +} and Br{sup +} ions incident on Si(100) surfaces with Cl and Br neutrals, respectively, to gain a better understanding of the ion-enhanced surface reaction kinetics during Si etching in Cl- and Br-based plasmas. The ions were incident normally on surfaces with translational energies in the range E{sub i} = 20–500 eV, and low-energy neutrals of E{sub n} = 0.01 eV were also incident normally thereon with the neutral-to-ion flux ratio in the range Γ{sub n}{sup 0}/Γ{sub i}{sup 0} = 0–100, where an improved Stillinger--Weber potential form was employed for the interatomic potential concerned. The etch yieldsmore » and thresholds presently simulated were in agreement with the experimental results previously reported for Si etching in Cl{sub 2} and Br{sub 2} plasmas as well as in Cl{sup +}, Cl{sub 2}{sup +}, and Br{sup +} beams, and the product stoichiometry simulated was consistent with that observed during Ar{sup +} beam incidence on Si in Cl{sub 2}. Moreover, the surface coverage of halogen atoms, halogenated layer thickness, surface stoichiometry, and depth profile of surface products simulated for Γ{sub n}{sup 0}/Γ{sub i}{sup 0} = 100 were in excellent agreement with the observations depending on E{sub i} reported for Si etching in Cl{sub 2} plasmas. The MD also indicated that the yield, coverage, and surface layer thickness are smaller in Si/Br than in Si/Cl system, while the percentage of higher halogenated species in product and surface stoichiometries is larger in Si/Br. The MD further indicated that in both systems, the translational energy distributions of products and halogen adsorbates desorbed from surfaces are approximated by two Maxwellians of temperature T{sub 1} ≈ 2500 K and T{sub 2} ≈ 7000–40 000 K. These energy distributions are discussed in terms of the desorption or evaporation from hot spots formed through chemically enhanced physical sputtering and physically enhanced chemical sputtering, which have so far been speculated to both occur in the ion-enhanced surface reaction kinetics of plasma etching.« less

Tridimensional morphology and kinetics of etch pit on the {l_brace}0 0 0 1{r_brace} plane of sapphire crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Lunyong; Sun Jianfei, E-mail: jfsun_hit@263.net; Zuo Hongbo

2012-08-15

The tridimensional morphology and etching kinetics of the etch pit on the C-{l_brace}0 0 0 1{r_brace} plane of sapphire crystal ({alpha}-Al{sub 2}O{sub 3}) in molten KOH were studied experimentally. It was shown that the etch pit takes on tridimensional morphologies with triangular symmetry same as the symmetric property of the sapphire crystal. Pits like centric and eccentric triangular pyramid as well as hexagonal pyramid were observed, but the latter is less in density. In-depth analyses show the side walls of the etch pits belong to the {l_brace}1 1{sup Macron} 0 2{sup Macron }{r_brace} family, and the triangular pit contains edgesmore » full composed by Al{sup 3+} ions on the etching surface so it is more stable than the hexagonal pit since its edges on the etching surface contains Al{sup 2+} ions. The etch pits developed in a manner of kinematic wave by the step moving with constant speed, which is controlled by the chemical reaction with activation energy of 96.6 kJ/mol between Al{sub 2}O{sub 3} and KOH. - Graphical abstract: Schematic showing the atomic configuration of the predicted side walls of regular triangular pyramid shaped etch pit on the C-{l_brace}0 0 0 1{r_brace} plane of sapphire crystal. Highlights: Black-Right-Pointing-Pointer Observed the tridimensional morphology of etch pits. Black-Right-Pointing-Pointer Figured out the atomic configuration origin of the etch pits. Black-Right-Pointing-Pointer Quantitatively determined the etch rates of the etch pits.« less

Multimode fiber tip Fabry-Perot cavity for highly sensitive pressure measurement.

PubMed

Chen, W P; Wang, D N; Xu, Ben; Zhao, C L; Chen, H F

2017-03-23

We demonstrate an optical Fabry-Perot interferometer fiber tip sensor based on an etched end of multimode fiber filled with ultraviolet adhesive. The fiber device is miniature (with diameter of less than 60 μm), robust and low cost, in a convenient reflection mode of operation, and has a very high gas pressure sensitivity of -40.94 nm/MPa, a large temperature sensitivity of 213 pm/°C within the range from 55 to 85 °C, and a relatively low temperature cross-sensitivity of 5.2 kPa/°C. This device has a high potential in monitoring environment of high pressure.

Improving contact layer patterning using SEM contour based etch model

NASA Astrophysics Data System (ADS)

Weisbuch, François; Lutich, Andrey; Schatz, Jirka; Hertzsch, Tino; Moll, Hans-Peter

2016-10-01

The patterning of the contact layer is modulated by strong etch effects that are highly dependent on the geometry of the contacts. Such litho-etch biases need to be corrected to ensure a good pattern fidelity. But aggressive designs contain complex shapes that can hardly be compensated with etch bias table and are difficult to characterize with standard CD metrology. In this work we propose to implement a model based etch compensation method able to deal with any contact configuration. With the help of SEM contours, it was possible to get reliable 2D measurements particularly helpful to calibrate the etch model. The selections of calibration structures was optimized in combination with model form to achieve an overall errRMS of 3nm allowing the implementation of the model in production.

Process for etching mixed metal oxides

DOEpatents

Ashby, Carol I. H.; Ginley, David S.

1994-01-01

An etching process using dicarboxylic and tricarboxylic acids as chelating etchants for mixed metal oxide films such as high temperature superconductors and ferroelectric materials. Undesirable differential etching rates between different metal oxides are avoided by selection of the proper acid or combination of acids. Feature sizes below one micron, excellent quality vertical edges, and film thicknesses in the 100 Angstom range may be achieved by this method.

Wet etching mechanism and crystallization of indium-tin oxide layer for application in light-emitting diodes

NASA Astrophysics Data System (ADS)

Su, Shui-Hsiang; Kong, Hsieng-Jen; Tseng, Chun-Lung; Chen, Guan-Yu

2018-01-01

In the article, we describe the etching mechanism of indium-tin oxide (ITO) film, which was wet-etched using a solution of hydrochloric acid (HCl) and ferric chloride (FeCl3). The etching mechanism is analyzed at various etching durations of ITO films by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and selective area diffraction (SAD) analysis. In comparison with the crystalline phase of SnO2, the In2O3 phase can be more easily transformed to In3+ and can form an inverted conical structure during the etching process. By adjusting the etching duration, the residual ITO is completely removed to show a designed pattern. This is attributed to the negative Gibbs energy of In2O3 transformed to In3+. The result also corresponds to the finding of energy-dispersive X-ray spectroscopy (EDS) analysis that the Sn/In ratio increases with increasing etching duration.

Nanoparticle-based etching of silicon surfaces

DOEpatents

Branz, Howard [Boulder, CO; Duda, Anna [Denver, CO; Ginley, David S [Evergreen, CO; Yost, Vernon [Littleton, CO; Meier, Daniel [Atlanta, GA; Ward, James S [Golden, CO

2011-12-13

A method (300) of texturing silicon surfaces (116) such to reduce reflectivity of a silicon wafer (110) for use in solar cells. The method (300) includes filling (330, 340) a vessel (122) with a volume of an etching solution (124) so as to cover the silicon surface 116) of a wafer or substrate (112). The etching solution (124) is made up of a catalytic nanomaterial (140) and an oxidant-etchant solution (146). The catalytic nanomaterial (140) may include gold or silver nanoparticles or noble metal nanoparticles, each of which may be a colloidal solution. The oxidant-etchant solution (146) includes an etching agent (142), such as hydrofluoric acid, and an oxidizing agent (144), such as hydrogen peroxide. Etching (350) is performed for a period of time including agitating or stirring the etching solution (124). The etch time may be selected such that the etched silicon surface (116) has a reflectivity of less than about 15 percent such as 1 to 10 percent in a 350 to 1000 nanometer wavelength range.

Alternative process for thin layer etching: Application to nitride spacer etching stopping on silicon germanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Posseme, N., E-mail: nicolas.posseme@cea.fr; Pollet, O.; Barnola, S.

2014-08-04

Silicon nitride spacer etching realization is considered today as one of the most challenging of the etch process for the new devices realization. For this step, the atomic etch precision to stop on silicon or silicon germanium with a perfect anisotropy (no foot formation) is required. The situation is that none of the current plasma technologies can meet all these requirements. To overcome these issues and meet the highly complex requirements imposed by device fabrication processes, we recently proposed an alternative etching process to the current plasma etch chemistries. This process is based on thin film modification by light ionsmore » implantation followed by a selective removal of the modified layer with respect to the non-modified material. In this Letter, we demonstrate the benefit of this alternative etch method in term of film damage control (silicon germanium recess obtained is less than 6 A), anisotropy (no foot formation), and its compatibility with other integration steps like epitaxial. The etch mechanisms of this approach are also addressed.« less

MEMS-based silicon cantilevers with integrated electrothermal heaters for airborne ultrafine particle sensing

NASA Astrophysics Data System (ADS)

Wasisto, Hutomo Suryo; Merzsch, Stephan; Waag, Andreas; Peiner, Erwin

2013-05-01

The development of low-cost and low-power MEMS-based cantilever sensors for possible application in hand-held airborne ultrafine particle monitors is described in this work. The proposed resonant sensors are realized by silicon bulk micromachining technology with electrothermal excitation, piezoresistive frequency readout, and electrostatic particle collection elements integrated and constructed in the same sensor fabrication process step of boron diffusion. Built-in heating resistor and full Wheatstone bridge are set close to the cantilever clamp end for effective excitation and sensing, respectively, of beam deflection. Meanwhile, the particle collection electrode is located at the cantilever free end. A 300 μm-thick, phosphorus-doped silicon bulk wafer is used instead of silicon-on-insulator (SOI) as the starting material for the sensors to reduce the fabrication costs. To etch and release the cantilevers from the substrate, inductively coupled plasma (ICP) cryogenic dry etching is utilized. By controlling the etching parameters (e.g., temperature, oxygen content, and duration), cantilever structures with thicknesses down to 10 - 20 μm are yielded. In the sensor characterization, the heating resistor is heated and generating thermal waves which induce thermal expansion and further cause mechanical bending strain in the out-of-plane direction. A resonant frequency of 114.08 +/- 0.04 kHz and a quality factor of 1302 +/- 267 are measured in air for a fabricated rectangular cantilever (500x100x13.5 μm3). Owing to its low power consumption of a few milliwatts, this electrothermal cantilever is suitable for replacing the current external piezoelectric stack actuator in the next generation of the miniaturized cantilever-based nanoparticle detector (CANTOR).

BeZnCdSe quantum-well ridge-waveguide laser diodes under low threshold room-temperature continuous-wave operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Jijun; Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology; Akimoto, Ryoichi, E-mail: r-akimoto@aist.go.jp

2015-10-19

Low threshold current ridge-waveguide BeZnCdSe quantum-well laser diodes (LDs) have been developed by completely etching away the top p-type BeMgZnSe/ZnSe:N short-period superlattice cladding layer, which can suppress the leakage current that flows laterally outside of the electrode. The waveguide LDs are covered with a thick SiO{sub 2} layer and planarized with chemical-mechanical polishing and a reactive ion etching process. Room-temperature lasing under continuous-wave condition is achieved with the laser cavity formed by the cleaved waveguide facets coated with high-reflectivity dielectric films. For a 4 μm-wide green LD lasing around a wavelength of 535 nm, threshold current and voltage of 7.07 mA and 7.89 Vmore » are achieved for a cavity length of 300 μm, and the internal differential quantum efficiency, internal absorption loss, gain constant, and nominal transparency current density are estimated to be 27%, 4.09 cm{sup −1}, 29.92 (cm × μm)/kA and 6.35 kA/(cm{sup 2 }× μm), respectively. This compact device can realize a significantly improved performance with much lower threshold power consumption, which would benefit the potential application for ZnSe-based green LDs as light sources in full-color display and projector devices installed in consumer products such as pocket projectors.« less

Uniform lateral etching of tungsten in deep trenches utilizing reaction-limited NF3 plasma process

NASA Astrophysics Data System (ADS)

Kofuji, Naoyuki; Mori, Masahito; Nishida, Toshiaki

2017-06-01

The reaction-limited etching of tungsten (W) with NF3 plasma was performed in an attempt to achieve the uniform lateral etching of W in a deep trench, a capability required by manufacturing processes for three-dimensional NAND flash memory. Reaction-limited etching was found to be possible at high pressures without ion irradiation. An almost constant etching rate that showed no dependence on NF3 pressure was obtained. The effect of varying the wafer temperature was also examined. A higher wafer temperature reduced the threshold pressure for reaction-limited etching and also increased the etching rate in the reaction-limited region. Therefore, the control of the wafer temperature is crucial to controlling the etching amount by this method. We found that the uniform lateral etching of W was possible even in a deep trench where the F radical concentration was low.

Process for Smoothing an Si Substrate after Etching of SiO2

NASA Technical Reports Server (NTRS)

Turner, Tasha; Wu, Chi

2003-01-01

A reactive-ion etching (RIE) process for smoothing a silicon substrate has been devised. The process is especially useful for smoothing those silicon areas that have been exposed by etching a pattern of holes in a layer of silicon dioxide that covers the substrate. Applications in which one could utilize smooth silicon surfaces like those produced by this process include fabrication of optical waveguides, epitaxial deposition of silicon on selected areas of silicon substrates, and preparation of silicon substrates for deposition of adherent metal layers. During etching away of a layer of SiO2 that covers an Si substrate, a polymer becomes deposited on the substrate, and the substrate surface becomes rough (roughness height approximately equal to 50 nm) as a result of over-etching or of deposition of the polymer. While it is possible to smooth a silicon substrate by wet chemical etching, the undesired consequences of wet chemical etching can include compromising the integrity of the SiO2 sidewalls and undercutting of the adjacent areas of the silicon dioxide that are meant to be left intact. The present RIE process results in anisotropic etching that removes the polymer and reduces height of roughness of the silicon substrate to less than 10 nm while leaving the SiO2 sidewalls intact and vertical. Control over substrate versus sidewall etching (in particular, preferential etching of the substrate) is achieved through selection of process parameters, including gas flow, power, and pressure. Such control is not uniformly and repeatably achievable in wet chemical etching. The recipe for the present RIE process is the following: Etch 1 - A mixture of CF4 and O2 gases flowing at rates of 25 to 75 and 75 to 125 standard cubic centimeters per minute (stdcm3/min), respectively; power between 44 and 55 W; and pressure between 45 and 55 mtorr (between 6.0 and 7.3 Pa). The etch rate lies between approximately equal to 3 and approximately equal to 6 nm/minute. Etch 2 - O2 gas flowing at 75 to 125 stdcm3/min, power between 44 and 55 W, and pressure between 50 and 100 mtorr (between 6.7 and 13.3 Pa).

Composition and conductance distributions of single GeSi quantum rings studied by conductive atomic force microscopy combined with selective chemical etching.

PubMed

Lv, Y; Cui, J; Jiang, Z M; Yang, X J

2013-02-15

Atomic force microscopy imaging combined with selective chemical etching is employed to quantitatively investigate three-dimensional (3D) composition distributions of single GeSi quantum rings (QRs). In addition, the 3D quantitative composition distributions and the corresponding conductance distributions are simultaneously obtained on the same single GeSi QRs by conductive atomic force microscopy combined with selective chemical etching, allowing us to investigate the correlations between the conductance and composition distributions of single QRs. The results show that the QRs' central holes have higher Ge content, but exhibit lower conductance, indicating that the QRs' conductance distribution is not consistent with their composition distribution. By comparing the topography, composition and conductance profiles of the same single QRs before and after different etching processes, it is found that the conductance distributions of GeSi QRs do not vary with the change of composition distribution. Instead, the QRs' conductance distributions are found to be consistent with their topographic shapes, which can be supposed to be due to the shape determined electronic structures.

Highχ block copolymers for directed self-assembly patterning without the need for topcoat or solvent annealing

NASA Astrophysics Data System (ADS)

Xu, Kui; Hockey, Mary Ann; Calderas, Eric; Guerrero, Douglas; Sweat, Daniel; Fiehler, Jeffrey

2017-03-01

High-χ block copolymers for directed self-assembly (DSA) patterning that do not need topcoat or solvent annealing have been developed. A variety of functionalities have been successfully added into the block copolymers, such as balanced surface energy between the polymer blocks, outstandingly high χ, tunable glass transition temperature (Tg), and selective crosslinking. Perpendicular orientation control, as desired for patterning, of the block copolymers can be simply achieved by thermal annealing due to the equal surface energy of the polymer blocks at the annealing temperatures, which allows avoiding solvent annealing or top-coat. The χ value can be tuned up to achieve L0 as low as 8-10 nm for lamellar-structured block copolymers and hole/pillar size as small as 5-6 nm for cylinder-structured block copolymers. The Tg of the block copolymers can be tuned to improve the kinetics of thermal annealing by enhancing the polymer chain mobility. Block-selective crosslinking facilitates the pattern transfer by mitigating pattern collapse during wet etching and improving oxygen plasma etching selectivity between the polymer blocks. This paper provides an introductory review of our high-χ block copolymer materials with various functionalities for achieving improved DSA performance.

Bonding effectiveness of self-etch adhesives to dentin after 24 h water storage.

PubMed

Sarr, Mouhamed; Benoist, Fatou Leye; Bane, Khaly; Aidara, Adjaratou Wakha; Seck, Anta; Toure, Babacar

2018-01-01

This study evaluated the immediate bonding effectiveness of five self-etch adhesive systems bonded to dentin. The microtensile bond strength of five self-etch adhesives systems, including one two-step and four one-step self-etch adhesives to dentin, was measured. Human third molars had their superficial dentin surface exposed, after which a standardized smear layer was produced using a medium-grit diamond bur. The selected adhesives were applied according to their respective manufacturer's instructions for μTBS measurement after storage in water at 37°C for 24 h. The μTBS varied from 11.1 to 44.3 MPa; the highest bond strength was obtained with the two-step self-etch adhesive Clearfil SE Bond and the lowest with the one-step self-etch adhesive Adper Prompt L-Pop. Pretesting failures mainly occurring during sectioning with the slow-speed diamond saw were observed only with the one-step self-etch adhesive Adper Prompt L-Pop (4 out of 18). When bonded to dentin, the self-etch adhesives with simplified application procedures (one-step self-etch adhesives) still underperform as compared to the two-step self-etch adhesive Clearfil SE Bond.

Bonding effectiveness of self-etch adhesives to dentin after 24 h water storage

PubMed Central

Sarr, Mouhamed; Benoist, Fatou Leye; Bane, Khaly; Aidara, Adjaratou Wakha; Seck, Anta; Toure, Babacar

2018-01-01

Purpose: This study evaluated the immediate bonding effectiveness of five self-etch adhesive systems bonded to dentin. Materials and Methods: The microtensile bond strength of five self-etch adhesives systems, including one two-step and four one-step self-etch adhesives to dentin, was measured. Human third molars had their superficial dentin surface exposed, after which a standardized smear layer was produced using a medium-grit diamond bur. The selected adhesives were applied according to their respective manufacturer's instructions for μTBS measurement after storage in water at 37°C for 24 h. Results: The μTBS varied from 11.1 to 44.3 MPa; the highest bond strength was obtained with the two-step self-etch adhesive Clearfil SE Bond and the lowest with the one-step self-etch adhesive Adper Prompt L-Pop. Pretesting failures mainly occurring during sectioning with the slow-speed diamond saw were observed only with the one-step self-etch adhesive Adper Prompt L-Pop (4 out of 18). Conclusions: When bonded to dentin, the self-etch adhesives with simplified application procedures (one-step self-etch adhesives) still underperform as compared to the two-step self-etch adhesive Clearfil SE Bond. PMID:29674814

Advanced plasma etch technologies for nanopatterning

NASA Astrophysics Data System (ADS)

Wise, Rich

2013-10-01

Advances in patterning techniques have enabled the extension of immersion lithography from 65/45 nm through 14/10 nm device technologies. A key to this increase in patterning capability has been innovation in the subsequent dry plasma etch processing steps. Multiple exposure techniques, such as litho-etch-litho-etch, sidewall image transfer, line/cut mask, and self-aligned structures, have been implemented to solution required device scaling. Advances in dry plasma etch process control across wafer uniformity and etch selectivity to both masking materials have enabled adoption of vertical devices and thin film scaling for increased device performance at a given pitch. Plasma etch processes, such as trilayer etches, aggressive critical dimension shrink techniques, and the extension of resist trim processes, have increased the attainable device dimensions at a given imaging capability. Precise control of the plasma etch parameters affecting across-design variation, defectivity, profile stability within wafer, within lot, and across tools has been successfully implemented to provide manufacturable patterning technology solutions. IBM has addressed these patterning challenges through an integrated total patterning solutions team to provide seamless and synergistic patterning processes to device and integration internal customers. We will discuss these challenges and the innovative plasma etch solutions pioneered by IBM and our alliance partners.

Advanced plasma etch technologies for nanopatterning

NASA Astrophysics Data System (ADS)

Wise, Rich

2012-03-01

Advances in patterning techniques have enabled the extension of immersion lithography from 65/45nm through 14/10nm device technologies. A key to this increase in patterning capability has been innovation in the subsequent dry plasma etch processing steps. Multiple exposure techniques such as litho-etch-litho-etch, sidewall image transfer, line/cut mask and self-aligned structures have been implemented to solution required device scaling. Advances in dry plasma etch process control, across wafer uniformity and etch selectivity to both masking materials and have enabled adoption of vertical devices and thin film scaling for increased device performance at a given pitch. Plasma etch processes such as trilayer etches, aggressive CD shrink techniques, and the extension of resist trim processes have increased the attainable device dimensions at a given imaging capability. Precise control of the plasma etch parameters affecting across design variation, defectivity, profile stability within wafer, within lot, and across tools have been successfully implemented to provide manufacturable patterning technology solutions. IBM has addressed these patterning challenges through an integrated Total Patterning Solutions team to provide seamless and synergistic patterning processes to device and integration internal customers. This paper will discuss these challenges and the innovative plasma etch solutions pioneered by IBM and our alliance partners.

The Development of III-V Semiconductor MOSFETs for Future CMOS Applications

NASA Astrophysics Data System (ADS)

Greene, Andrew M.

Alternative channel materials with superior transport properties over conventional strained silicon are required for supply voltage scaling in low power complementary metal-oxide-semiconductor (CMOS) integrated circuits. Group III-V compound semiconductor systems offer a potential solution due to their high carrier mobility, low carrier effective mass and large injection velocity. The enhancement in transistor drive current at a lower overdrive voltage allows for the scaling of supply voltage while maintaining high switching performance. This thesis focuses on overcoming several material and processing challenges associated with III-V semiconductor development including a low thermal processing budget, high interface trap state density (Dit), low resistance source/drain contacts and growth on lattice mismatched substrates. Non-planar In0.53Ga0.47As FinFETs were developed using both "gate-first" and "gate-last" fabrication methods for n-channel MOSFETs. Electron beam lithography and anisotropic plasma etching processes were optimized to create highly scaled fins with near vertical sidewalls. Plasma damage was removed using a wet etch process and improvements in gate efficiency were characterized on MOS capacitor structures. A two-step, selective removal of the pre-grown n+ contact layer was developed for "gate-last" recess etching. The final In0.53Ga 0.47As FinFET devices demonstrated an ION = 70 mA/mm, I ON/IOFF ratio = 15,700 and sub-threshold swing = 210 mV/dec. Bulk GaSb and strained In0.36Ga0.64Sb quantum well (QW) heterostructures were developed for p-channel MOSFETs. Dit was reduced to 2 - 3 x 1012 cm-2eV-1 using an InAs surface layer, (NH4)2S passivation and atomic layer deposition (ALD) of Al2O3. A self-aligned "gate-first" In0.36Ga0.64Sb MOSFET fabrication process was invented using a "T-shaped" electron beam resist patterning stack and intermetallic source/drain contacts. Ni contacts annealed at 300°C demonstrated an ION = 166 mA/mm, ION/IOFF ratio = 1,500 and sub-threshold swing = 340 mV/dec. Split C-V measurements were used to extract an effective channel mobility of muh* = 300 cm2/Vs at Ns = 2 x 1012 cm -2. "Gate-last" MOSFETs grown with an epitaxial p + contact layer were fabricated using selective gate-recess etching techniques. A parasitic "n-channel" limited ION/I OFF ratio and sub-threshold swing, most likely due to effects from the InAs surface layer.

Effect of Atomic Hydrogen on Preparation of Highly Moisture-Resistive SiNx Films at Low Substrate Temperatures

NASA Astrophysics Data System (ADS)

Heya, Akira; Niki, Toshikazu; Takano, Masahiro; Yonezawa, Yasuto; Minamikawa, Toshiharu; Muroi, Susumu; Minami, Shigehira; Izumi, Akira; Masuda, Atsushi; Umemoto, Hironobu; Matsumura, Hideki

2004-12-01

Highly moisture-resistive SiNx films on a Si substrate are obtained at substrate temperatures of 80°C by catalytic chemical vapor deposition (Cat-CVD) using a source gas with H2. Atomic hydrogen effected the selective etching of a weak-bond regions and an increase in atomic density induced by the energy of the surface reaction. It is concluded that Cat-CVD using H2 is a promising candidate for the fabrication of highly moisture-resistive SiNx films at low temperatures.

Process for etching mixed metal oxides

DOEpatents

Ashby, C.I.H.; Ginley, D.S.

1994-10-18

An etching process is described using dicarboxylic and tricarboxylic acids as chelating etchants for mixed metal oxide films such as high temperature superconductors and ferroelectric materials. Undesirable differential etching rates between different metal oxides are avoided by selection of the proper acid or combination of acids. Feature sizes below one micron, excellent quality vertical edges, and film thicknesses in the 100 Angstrom range may be achieved by this method. 1 fig.

Characterization of Plasma-Induced Damage of Selectively Recessed GaN/InAlN/AlN/GaN Heterostructures Using SiCl4 and SF6

NASA Astrophysics Data System (ADS)

Ostermaier, Clemens; Pozzovivo, Gianmauro; Basnar, Bernhard; Schrenk, Werner; Carlin, Jean-François; Gonschorek, Marcus; Grandjean, Nicolas; Vincze, Andrej; Tóth, Lajos; Pécz, Bela; Strasser, Gottfried; Pogany, Dionyz; Kuzmik, Jan

2010-11-01

We have investigated an inductively coupled plasma etching recipe using SiCl4 and SF6 with a resulting selectivity >10 for GaN in respect to InAlN. The formation of an etch-resistant layer of AlF3 on InAlN required about 1 min and was noticed by a 4-times-higher initial etch rate on bare InAlN barrier high electron mobility transistors (HEMTs). Comparing devices with and without plasma-treatment below the gate showed no degradation in drain current and gate leakage current for plasma exposure durations shorter than 30 s, indicating no plasma-induced damage of the InAlN barrier. Devices etched longer than the required time for the formation of the etch-resistant barrier exhibited a slight decrease in drain current and an increase in gate leakage current which saturated for longer etching-time durations. Finally, we could prove the quality of the recipe by recessing the highly doped 6 nm GaN cap layer of a GaN/InAlN/AlN/GaN heterostructure down to the 2 nm thin InAlN/AlN barrier layer.

Etching characteristics of Si{110} in 20 wt% KOH with addition of hydroxylamine for the fabrication of bulk micromachined MEMS

NASA Astrophysics Data System (ADS)

Rao, A. V. Narasimha; Swarnalatha, V.; Pal, P.

2017-12-01

Anisotropic wet etching is a most widely employed for the fabrication of MEMS/NEMS structures using silicon bulk micromachining. The use of Si{110} in MEMS is inevitable when a microstructure with vertical sidewall is to be fabricated using wet anisotropic etching. In most commonly employed etchants (i.e. TMAH and KOH), potassium hydroxide (KOH) exhibits higher etch rate and provides improved anisotropy between Si{111} and Si{110} planes. In the manufacturing company, high etch rate is demanded to increase the productivity that eventually reduces the cost of end product. In order to modify the etching characteristics of KOH for the micromachining of Si{110}, we have investigated the effect of hydroxylamine (NH2OH) in 20 wt% KOH solution. The concentration of NH2OH is varied from 0 to 20% and the etching is carried out at 75 °C. The etching characteristics which are studied in this work includes the etch rates of Si{110} and silicon dioxide, etched surface morphology, and undercutting at convex corners. The etch rate of Si{110} in 20 wt% KOH + 15% NH2OH solution is measured to be four times more than that of pure 20 wt% KOH. Moreover, the addition of NH2OH increases the undercutting at convex corners and enhances the etch selectivity between Si and SiO2.

Ridge-width dependence of the threshold of long wavelength (λ ≈ 14 µm) Quantum Cascade lasers with sloped and vertical sidewalls.

PubMed

Huang, Xue; Chiu, Yenting; Charles, William O; Gmachl, Claire

2012-01-30

We investigate the ridge-width dependence of the threshold of Quantum Cascade lasers fabricated by wet and dry etching, respectively. The sloped sidewalls resulting from wet etching affect the threshold in two ways as the ridge gets narrower. First, the transverse modes are deeper in the substrate, hence reducing the optical confinement factor. Second, more important, a non-negligible field exists in the lossy SiO2 insulation layer, as a result of transverse magnetic mode coupling to the surface plamon mode at the insulator/metal surface, which increases the waveguide loss. By contrast, dry etching is anisotropic and leads to waveguides with vertical sidewalls, which avoids the shift of the modes to the substrate layer and coupling to the surface plasmons, resulting in improved threshold compared with wet-etched lasers, e.g., for narrow ridge widths below 20 µm, the threshold of a 14 µm wide λ ≈ 14 µm laser by dry etching is ~60% lower than that of a wet-etched laser of the same width, at 80 K.

Modeling, Fabrication, and Analysis of Vertical Conduction Gallium Nitride Fin MOSFET

NASA Astrophysics Data System (ADS)

Tahhan, Maher Bishara

Gallium Nitride has seen much interest in the field of electronics due to its large bandgap and high mobility. In the field of power electronics, this combination leads to a low on-resistance for a given breakdown voltage. To take full advantage of this, vertical conduction transistors in GaN can give high breakdown voltages independent of chip area, leading to transistors with nominally low on resistance with high breakdown at a low cost. Acknowledging this, a vertical transistor design is presented with a small footprint area. This design utilizes a fin structure as a double gated insulated MESFET with electrons flowing from the top of the fin downward. The transistor's characteristics and design is initially explored via simulation and modelling. In this modelling, it is found that the narrow dimension of the fin must be sub-micron to allow for the device to be turned off with no leakage current and have a positive threshold voltage. Several process modules are developed and integrated to fabricate the device. A smooth vertical etch leaving low damage to the surfaces is demonstrated and characterized, preventing micromasking during the GaN dry etch. Methods of removing damage from the dry etch are tested, including regrowth and wet etching. Several hard masks were developed to be used in conjunction with this GaN etch for various requirements of the process, such as material constraints and self-aligning a metal contact. Multiple techniques are tested to deposit and pattern the gate oxide and metal to ensure good contact with the channel without causing unwanted shorts. To achieve small fin dimensions, a self-aligned transistor process flow is presented allowing for smaller critical dimensions at increased fabrication tolerances by avoiding the use of lithographic steps that require alignments to very high accuracy. In the case of the device design presented, the fins are lithographically defined at the limit of i-line stepper system. From this single lithography, the sources are formed, fins are etched, and the gate insulator and metal are deposited. The first functional fabricated devices are presented, but exhibit a few differences from the model. A threshold voltage of -6 V, was measured, with an ID of 5 kA/cm2 at 3 V, and Ron of 0.6 mO/cm 2. The current is limited by the Schottky nature of the top contacts and show a turn-on voltage as a result. These measurements are comparable to recently published GaN fin MOSFET data, whose devices were defined by e-beam lithography. This dissertation work sought to show that a vertical conduction fin MOSFET can be fabricated on GaN. Furthermore, it aimed to provide a self-aligned process that does not require e-beam lithography. With further development, such devices can be designed to hold large voltages while maintaining a small footprint.

Resistless lithography - selective etching of silicon with gallium doping regions

NASA Astrophysics Data System (ADS)

Abdullaev, D.; Milovanov, R.; Zubov, D.

2016-12-01

This paper presents the results for used of resistless lithography with a further reactive-ion etching (RIE) in various chemistry after local (Ga+) implantation of silicon with different doping dose and different size doped regions. We describe the different etching regimes for pattern transfer of FIB implanted Ga masks in silicon. The paper studied the influence of the implantation dose on the silicon surface, the masking effect and the mask resistance to erosion at dry etching. Based on these results we conclude about the possibility of using this method to create micro-and nanoscale silicon structures.

Fabrication of a terahertz quantum-cascade laser with a double metal waveguide based on multilayer GaAs/AlGaAs heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khabibullin, R. A., E-mail: khabibullin@isvch.ru; Shchavruk, N. V.; Pavlov, A. Yu.

2016-10-15

The Postgrowth processing of GaAs/AlGaAs multilayer heterostructures for terahertz quantumcascade lasers (QCLs) are studied. This procedure includes the thermocompression bonding of In–Au multilayer heterostructures with a doped n{sup +}-GaAs substrate, mechanical grinding, and selective wet etching of the substrate, and dry etching of QCL ridge mesastripes through a Ti/Au metallization mask 50 and 100 μm wide. Reactive-ion-etching modes with an inductively coupled plasma source in a BCl{sub 3}/Ar gas mixture are selected to obtain vertical walls of the QCL ridge mesastripes with minimum Ti/Au mask sputtering.

Semiconductor structure and recess formation etch technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Bin; Sun, Min; Palacios, Tomas Apostol

2017-02-14

A semiconductor structure has a first layer that includes a first semiconductor material and a second layer that includes a second semiconductor material. The first semiconductor material is selectively etchable over the second semiconductor material using a first etching process. The first layer is disposed over the second layer. A recess is disposed at least in the first layer. Also described is a method of forming a semiconductor structure that includes a recess. The method includes etching a region in a first layer using a first etching process. The first layer includes a first semiconductor material. The first etching processmore » stops at a second layer beneath the first layer. The second layer includes a second semiconductor material.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Kun; Wang, Dan; Yang, Ping

Graphical abstract: Anatase TiO{sub 2} nanocaps prepared by HF-assisted chemical etching method exhibit enhanced photocatalytic activity compared with commercial P25 because of HF served as an etching agent to remove doped impurities. - Highlights: • Anatase TiO{sub 2} nanocaps were synthesized by HF etching process. • The optimal conditions of experiment are 700 °C calcination and 0.2 mL HF solution. • The photocatalytic properties was studied upon UV and Visible irradiation. • The unique TiO{sub 2} nanocaps structure shows excellent photocatalytic activity. - Abstract: Anatase titanium dioxide (TiO{sub 2}) nanocaps were created via a four-step process including the preparation ofmore » SiO{sub 2} spheres, the deposition of a TiO{sub 2} layer to fabricate SiO{sub 2}@TiO{sub 2} composite spheres, the calcination for obtaining the crystal structure of anatase phase, and hydrofluoric acid (HF) etching to dissolve SiO{sub 2} cores. The SiO{sub 2}@TiO{sub 2} spheres calcined at 700 °C revealed fine photocatalytic activity. Interestingly, most of samples transformed into TiO{sub 2} nanocaps via HF etching, and TiO{sub 2} nanocaps prepared using optimal conditions exhibited quick degradation (k is 0.052 min{sup −1}) compared with commercial P25 (k is 0.030 min{sup −1}) and the TiO{sub 2} nanostructures etched by a NaOH solution. The excellent photocatalytic performance is attributed to its unique hollow hemispherical nanocaps structure, which is in favor of making full use of incident light. The photocatalysis phenomenon in visible light was also observed after depositing Au nanoparticles on anantase TiO{sub 2} nanocaps.« less

Study of Gallium Arsenide Etching in a DC Discharge in Low-Pressure HCl-Containing Mixtures

NASA Astrophysics Data System (ADS)

Dunaev, A. V.; Murin, D. B.

2018-04-01

Halogen-containing plasmas are often used to form topological structures on semiconductor surfaces; therefore, spectral monitoring of the etching process is an important diagnostic tool in modern electronics. In this work, the emission spectra of gas discharges in mixtures of hydrogen chloride with argon, chlorine, and hydrogen in the presence of a semiconducting gallium arsenide plate were studied. Spectral lines and bands of the GaAs etching products appropriate for monitoring the etching rate were determined. It is shown that the emission intensity of the etching products is proportional to the GaAs etching rate in plasmas of HCl mixtures with Ar and Cl2, which makes it possible to monitor the etching process in real time by means of spectral methods.

Observation and measurement of negative differential resistance on PtSi Schottky junctions on porous silicon.

PubMed

Banihashemian, Seyedeh Maryam; Hajghassem, Hassan; Erfanian, Alireza; Aliahmadi, Majidreza; Mohtashamifar, Mansor; Mosakazemi, Seyed Mohamadhosein

2010-01-01

Nanosize porous Si is made by two step controlled etching of Si. The first etching step is carried on the Si surface and the second is performed after deposition of 75 Å of platinum on the formed surface. A platinum silicide structure with a size of less than 25 nm is formed on the porous Si surface, as measured with an Atomic Forced Microscope (AFM). Differential resistance curve as a function of voltage in 77 K and 100 K shows a negative differential resistance and indicates the effect of quantum tunneling. In general form, the ratio of maximum to minimum tunneling current (PVR) and the number of peaks in I-V curves reduces by increasing the temperature. However, due to accumulation of carriers behind the potential barrier and superposition of several peaks, it is observed that the PVR increases at 100 K and the maximum PVR at 100 K is 189.6.

Fabrication of ultra-high aspect ratio (>160:1) silicon nanostructures by using Au metal assisted chemical etching

NASA Astrophysics Data System (ADS)

Li, Hailiang; Ye, Tianchun; Shi, Lina; Xie, Changqing

2017-12-01

We present a facile and effective approach for fabricating high aspect ratio, dense and vertical silicon nanopillar arrays, using a combination of metal etching following electron-beam lithography and Au metal assisted chemical etching (MacEtch). Ti/Au nanostructures used as catalysts in MacEtch are formed by single layer resist-based electron-beam exposure followed by ion beam etching. The effects of MacEtch process parameters, including half period, etching time, the concentrations of H2O2 and HF, etching temperature and drying method are systematically investigated. Especially, we demonstrate an enhancement of etching quality by employing cold MacEtch process, and an enhancement in preventing the collapse of high aspect ratio nanostructures by employing low surface tension rinse liquid and natural evaporation in the drying stage. Using an optimized MacEtch process, vertical silicon nanopillar arrays with a period of 250 nm and aspect ratio up to 160:1 are realized. Our results should be instructive for exploring the achievable aspect ratio limit in silicon nanostructures and may find potential applications in photovoltaic devices, thermoelectric devices and x-ray diffractive optics.

Prediction of plasma-induced damage distribution during silicon nitride etching using advanced three-dimensional voxel model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuboi, Nobuyuki, E-mail: Nobuyuki.Kuboi@jp.sony.com; Tatsumi, Tetsuya; Kinoshita, Takashi

2015-11-15

The authors modeled SiN film etching with hydrofluorocarbon (CH{sub x}F{sub y}/Ar/O{sub 2}) plasma considering physical (ion bombardment) and chemical reactions in detail, including the reactivity of radicals (C, F, O, N, and H), the area ratio of Si dangling bonds, the outflux of N and H, the dependence of the H/N ratio on the polymer layer, and generation of by-products (HCN, C{sub 2}N{sub 2}, NH, HF, OH, and CH, in addition to CO, CF{sub 2}, SiF{sub 2}, and SiF{sub 4}) as ion assistance process parameters for the first time. The model was consistent with the measured C-F polymer layer thickness,more » etch rate, and selectivity dependence on process variation for SiN, SiO{sub 2}, and Si film etching. To analyze the three-dimensional (3D) damage distribution affected by the etched profile, the authors developed an advanced 3D voxel model that can predict the time-evolution of the etched profile and damage distribution. The model includes some new concepts for gas transportation in the pattern using a fluid model and the property of voxels called “smart voxels,” which contain details of the history of the etching situation. Using this 3D model, the authors demonstrated metal–oxide–semiconductor field-effect transistor SiN side-wall etching that consisted of the main-etch step with CF{sub 4}/Ar/O{sub 2} plasma and an over-etch step with CH{sub 3}F/Ar/O{sub 2} plasma under the assumption of a realistic process and pattern size. A large amount of Si damage induced by irradiated hydrogen occurred in the source/drain region, a Si recess depth of 5 nm was generated, and the dislocated Si was distributed in a 10 nm deeper region than the Si recess, which was consistent with experimental data for a capacitively coupled plasma. An especially large amount of Si damage was also found at the bottom edge region of the metal–oxide–semiconductor field-effect transistors. Furthermore, our simulation results for bulk fin-type field-effect transistor side-wall etching showed that the Si fin (source/drain region) was directly damaged by high energy hydrogen and had local variations in the damage distribution, which may lead to a shift in the threshold voltage and the off-state leakage current. Therefore, side-wall etching and ion implantation processes must be carefully designed by considering the Si damage distribution to achieve low damage and high transistor performance for complementary metal–oxide–semiconductor devices.« less

Nanostructured surfaces using thermal nanoimprint lithography: Applications in thin membrane technology, piezoelectric energy harvesting and tactile pressure sensing

NASA Astrophysics Data System (ADS)

Nabar, Bhargav Pradip

Nanoimprint lithography (NIL) is emerging as a viable contender for fabrication of large-scale arrays of 5-500 nm features. The work presented in this dissertation aims to leverage the advantages of NIL for realization of novel Nano Electro Mechanical Systems (NEMS). The first application is a nanoporous membrane blood oxygenator system. A fabrication process for realization of thin nanoporous membranes using thermal nanoimprint lithography is presented. Suspended silicon nitride membranes were fabricated by Low-Pressure Chemical Vapor Deposition (LPCVD) in conjunction with a potassium hydroxide-based bulk micromachining process. Nanoscale features were imprinted into a commercially available thermoplastic polymer resist using a pre-fabricated silicon mold. The pattern was reversed and transferred to a thin aluminum oxide layer by means of a novel two stage lift-off technique. The patterned aluminum oxide was used as an etch mask in a CHF3/He based reactive ion etch process to transfer the pattern to silicon nitride. Highly directional etch profiles with near vertical sidewalls and excellent Si3N4/Al2O3 etch selectivity was observed. One-micrometer-thick porous membranes with varying dimensions of 250x250 microm2 to 450x450 microm 2 and pore diameter of 400 nm have been engineered and evaluated. Results indicate that the membranes have consistent nanopore dimensions and precisely defined porosity, which makes them ideal as gas exchange interfaces in blood oxygenation systems as well as other applications such as dialysis. Additionally, bulk -- micromachined microfluidic channels have been developed for uniform, laminar blood flow with minimal cell trauma. NIL has been used for ordered growth of crystalline nanostructures for sensing and energy harvesting. Highly ordered arrays of crystalline ZnO nanorods have been fabricated using a polymer template patterned by thermal nanoimprint lithography, in conjunction with a low temperature hydrothermal growth process. Zinc Oxide nanorods were characterized to determine their piezoelectric response to an applied force. An atomic force microscope operating in the force spectroscopy mode was used to apply forces in the nN range. In contrast to previously published reports using lateral tip motion (C-AFM), the action of the tip in our experiment was perpendicular to the plane of the nanorods, allowing a more defined tip -- nanorod interaction. Voltage pulses of a positive polarity with amplitude ranging from hundreds of microV to few mV were observed. The tip -- nanorod interaction was modeled using commercial solid modeling software and was simulated using finite element analysis. Comparison of the results yielded useful observations for design of piezoelectric energy harvesters/sensors using ZnO nanorods. A nanoelectromechanical (NEMS) piezoelectric energy harvester using crystalline ZnO nanowires is developed. The device converts ambient vibrations into usable electrical energy for low power sensor applications. This is accomplished by mechanical excitation of an ordered ZnO nanorod array using a suspended bulk micromachined proof mass. The device is capable of generating up to 14.2 mV single polarity voltage under an input vibration of amplitude 1 g (9.8 m/s2) at a frequency of 1.10 kHz. Finally, large area arrays of ordered ZnO piezoelectric nanorods are developed on flexible substrates towards self-powered sensing skin for robots. The sensor array is designed to measure tactile pressure in the 10 kPa-- 200 kPa range with 1 mm spatial resolution. A voltage signal in the range of few mV is observed in response to applied pressure. This work represents the first demonstration of perfectly ordered, vertically aligned, crystalline ZnO nanorod arrays, fabricated in polyimides to ensure conformity to non-planar surfaces such as a robot's. The sensors are self-packaged using a flexible substrate and a superstrate. In addition to the novelty of the sensor structure itself, the work includes an innovative low-temperature hydrothermal ZnO growth process compatible with the temperature restrictions imposed by the polyimide substrate/superstrate.

Microtrenching-free two-step reactive ion etching of 4H-SiC using NF{sub 3}/HBr/O{sub 2} and Cl{sub 2}/O{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tseng, Yuan-Hung, E-mail: yhtseng.ee99g@nctu.edu.tw; Tsui, Bing-Yue

2014-05-15

In this paper, the authors performed a reactive ion etch of a 4H-SiC substrate with a gas mixture of NF{sub 3}, HBr, and O{sub 2}, resulting in a microtrenching-free etch. The etch rate was 107.8 nm/min, and the selectivity over the oxide hard mask was ∼3.85. Cross-sectional scanning electron microscopy showed no microtrenching compared with etches using plasmas of NF{sub 3}, NF{sub 3}/HBr, and NF{sub 3}/O{sub 2}. Analyzing a variety of HBr/O{sub 2} mixing ratios, the authors discuss the additive effect of each gas and their respective potential mechanisms for alleviating microtrenching. To increase the radius of gyration of the bottommore » corners, they introduced a second etch step with Cl{sub 2}/O{sub 2} plasma. Fabricating simple metal-oxide-semiconductor capacitors on the two-step etched surface, the authors found that the electrical characteristics of the etched sample were nearly the same as the nonetched sample.« less

Deep Reactive Ion Etching (DRIE) of High Aspect Ratio SiC Microstructures using a Time-Multiplexed Etch-Passivate Process

NASA Technical Reports Server (NTRS)

Evans, Laura J.; Beheim, Glenn M.

2006-01-01

High aspect ratio silicon carbide (SiC) microstructures are needed for microengines and other harsh environment micro-electro-mechanical systems (MEMS). Previously, deep reactive ion etching (DRIE) of low aspect ratio (AR less than or = 1) deep (greater than 100 micron) trenches in SiC has been reported. However, existing DRIE processes for SiC are not well-suited for definition of high aspect ratio features because such simple etch-only processes provide insufficient control over sidewall roughness and slope. Therefore, we have investigated the use of a time-multiplexed etch-passivate (TMEP) process, which alternates etching with polymer passivation of the etch sidewalls. An optimized TMEP process was used to etch high aspect ratio (AR greater than 5) deep (less than 100 micron) trenches in 6H-SiC. Power MEMS structures (micro turbine blades) in 6H-SiC were also fabricated.

Evaluation of Pentafluoroethane and 1,1-Difluoroethane for a Dielectric Etch Application in an Inductively Coupled Plasma Etch Tool

NASA Astrophysics Data System (ADS)

Karecki, Simon; Chatterjee, Ritwik; Pruette, Laura; Reif, Rafael; Sparks, Terry; Beu, Laurie; Vartanian, Victor

2000-07-01

In this work, a combination of two hydrofluorocarbon compounds, pentafluoroethane (FC-125, C2HF5) and 1,1-difluoroethane (FC-152a, CF2H-CH3), was evaluated as a potential replacement for perfluorocompounds in dielectric etch applications. A high aspect ratio oxide via etch was used as the test vehicle for this study, which was conducted in a commercial inductively coupled high density plasma etch tool. Both process and emissions data were collected and compared to those provided by a process utilizing a standard perfluorinated etch chemistry (C2F6). Global warming (CF4, C2F6, CHF3) and hygroscopic gas (HF, SiF4) emissions were characterized using Fourier transform infrared (FTIR) spectroscopy. FC-125/FC-152a was found to produce significant reductions in global warming emissions, on the order of 68 to 76% relative to the reference process. Although etch stopping, caused by a high degree of polymer deposition inside the etched features, was observed, process data otherwise appeared promising for an initial study, with good resist selectivity and etch rates being achieved.

High-aspect ratio micro- and nanostructures enabled by photo-electrochemical etching for sensing and energy harvesting applications

NASA Astrophysics Data System (ADS)

Alhalaili, Badriyah; Dryden, Daniel M.; Vidu, Ruxandra; Ghandiparsi, Soroush; Cansizoglu, Hilal; Gao, Yang; Saif Islam, M.

2018-03-01

Photo-electrochemical (PEC) etching can produce high-aspect ratio features, such as pillars and holes, with high anisotropy and selectivity, while avoiding the surface and sidewall damage caused by traditional deep reactive ion etching (DRIE) or inductively coupled plasma (ICP) RIE. Plasma-based techniques lead to the formation of dangling bonds, surface traps, carrier leakage paths, and recombination centers. In pursuit of effective PEC etching, we demonstrate an optical system using long wavelength (λ = 975 nm) infra-red (IR) illumination from a high-power laser (1-10 W) to control the PEC etching process in n-type silicon. The silicon wafer surface was patterned with notches through a lithography process and KOH etching. Then, PEC etching was introduced by illuminating the backside of the silicon wafer to enhance depth, resulting in high-aspect ratio structures. The effect of the PEC etching process was optimized by varying light intensities and electrolyte concentrations. This work was focused on determining and optimizing this PEC etching technique on silicon, with the goal of expanding the method to a variety of materials including GaN and SiC that are used in designing optoelectronic and electronic devices, sensors and energy harvesting devices.

Etching Characteristics of VO2 Thin Films Using Inductively Coupled Cl2/Ar Plasma

NASA Astrophysics Data System (ADS)

Ham, Yong-Hyun; Efremov, Alexander; Min, Nam-Ki; Lee, Hyun Woo; Yun, Sun Jin; Kwon, Kwang-Ho

2009-08-01

A study on both etching characteristics and mechanism of VO2 thin films in the Cl2/Ar inductively coupled plasma was carried. The variable parameters were gas pressure (4-10 mTorr) and input power (400-700 W) at fixed bias power of 150 W and initial mixture composition of 25% Cl2 + 75% Ar. It was found that an increase in both gas pressure and input power results in increasing VO2 etch rate while the etch selectivity over photoresist keeps a near to constant values. Plasma diagnostics by Langmuir probes and zero-dimensional plasma model provided the data on plasma parameters, steady-state densities and fluxes of active species on the etched surface. The model-based analysis of the etch mechanism showed that, for the given ranges of operating conditions, the VO2 etch kinetics corresponds to the transitional regime of ion-assisted chemical reaction and is influenced by both neutral and ion fluxes with a higher sensitivity to the neutral flux.

Automated Array Assembly, Phase 2. Low-cost Solar Array Project, Task 4

NASA Technical Reports Server (NTRS)

Lopez, M.

1978-01-01

Work was done to verify the technological readiness of a select process sequence with respect to satisfying the Low Cost Solar Array Project objectives of meeting the designated goals of $.50 per peak watt in 1986 (1975 dollars). The sequence examined consisted of: (1) 3 inches diameter as-sawn Czochralski grown 1:0:0 silicon, (2) texture etching, (3) ion implanting, (4) laser annealing, (5) screen printing of ohmic contacts and (6) sprayed anti-reflective coatings. High volume production projections were made on the selected process sequence. Automated processing and movement of hardware at high rates were conceptualized to satisfy the PROJECT's 500 MW/yr capability. A production plan was formulated with flow diagrams integrating the various processes in the cell fabrication sequence.

Anisotropic etching of amorphous perfluoropolymer films in oxygen-based inductively coupled plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, Takao; Akagi, Takanori; Center for NanoBio Integration, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656

2009-01-01

An amorphous perfluoropolymer, 'Cytop' (Asahi Glass Co., Ltd.), is a preferable material for the fabrication of micro total analysis system devices because of its superior optical transparency over a wide wavelength range and low refractive index of 1.34, which is almost the same as that of water, as well as excellent chemical stability. To establish the precise microfabrication technology for this unique resin, the dry etching of the amorphous perfluoropolymer in Ar/O{sub 2} low-pressure inductively coupled plasma has been studied. A relatively high etch rate of approximately 6.3 {mu}m/min at maximum and highly anisotropic etched features was attained. Plasma measurementsmore » by a single Langmuir probe technique and actinometry revealed that etching is dominated by ion-assisted surface desorption above a 10%O{sub 2} mixing ratio, whereas the supply of active oxygen species is the rate-limiting process below 10%. Moreover, angled x-ray photoelectron spectroscopy measurements of an etched trench pattern revealed that a high anisotropy is attributed to the formation of a carbon-rich sidewall protection layer.« less

320 x 256 Complementary Barrier Infrared Detector Focal Plane Array for Long-Wave Infrared Imaging

NASA Technical Reports Server (NTRS)

Nguyen, Jean; Rafol, Sir B.; Soibel, Alexander; Khoskhlagh, Arezou; Ting, David Z.-Y.; Liu, John K.; Mumolo, Jason M.; Gunapala, Sarath D.

2012-01-01

A 320 x 256 Complementary Barrier Infrared (CBIRD) focal plane array for long-wavelength infrared (LWIR) imaging is reported. The arrays were grown by molecular beam expitaxy (MBE) with a 300 period 1.9 um thick absorber. The mean dark current density of 2.2 x 10-4 A/cm2 was measured at an operating bias of 128 mV with a long wavelength cutoff of 8.8 ?m observed at 50% of the peak. The maximum quantum efficiency was 54% measured at 5.6 ?m. Operating at T = 80K, the array yielded an 81% fill factor with 97% operability. Good imagery with a mean noise equivalent different temperature (NE?T) of 18.6 mK and a mean detectivity of D* = 1.3 x 1011 cm-Hz1/2/W was achieved. The substrate was thinned using mechanical lapping and neither an AR coating nor a passivation layer was applied. This article provides the details of the fabrication process for achieving low-dark current LWIR CBIRD arrays. Discussion for an effective hard mask for excellent pattern transfer is given and appropriate mounting techniques for good thermal contact during the dry etching process is described. The challenges and differences between etching large 200 ?m test diodes and small 28 ?m FPA pixels are given.

Electrodeposited Ni nanowires-track etched P.E.T. composites as selective solar absorbers

NASA Astrophysics Data System (ADS)

Lukhwa, R.; Sone, B.; Kotsedi, L.; Madjoe, R.; Maaza, M.

2018-05-01

This contribution reports on the structural, optical and morphological properties of nanostructured flexible solar-thermal selective absorber composites for low temperature applications. The candidate material in the system is consisting of electrodeposited nickel nano-cylinders embedded in track-etched polyethylene terephthalate (PET) host membrane of pore sizes ranging between 0.3-0.8µm supported by conductive nickel thin film of about 0.5µm. PET were irradiated with 11MeV/u high charged xenon (Xe) ions at normal incidence. The tubular and metallic structure of the nickel nano-cylinders within the insulator polymeric host forms a typical ceramic-metal nano-composite "Cermet". The produced material was characterized by the following techniques: X-ray diffraction (XRD) for structural characterization to determine preferred crystallographic structure, and grain size of the materials; Scanning electron microscopy (SEM) to determine surface morphology, particle size, and visual imaging of distribution of structures on the surface of the substrate; Atomic force microscopy (AFM) to characterize surface roughness, surface morphology, and film thickness, and UV-Vis-NIR spectrophotometer to measure the reflectance, then to determine solar absorption

Improvement in etching rate for epilayer lift-off with surfactant

NASA Astrophysics Data System (ADS)

Wu, Fan-Lei; Horng, Ray-Hua; Lu, Jian-Heng; Chen, Chun-Li; Kao, Yu-Cheng

2013-03-01

In this study, the GaAs epilayer is quickly separated from GaAs substrate by epitaxial lift-off (ELO) process with mixture etchant solution. The HF solution mixes with surfactant as mixture etchant solution to etch AlAs sacrificial layer for the selective wet etching of AlAs sacrificial layer. Addiction surfactants etchant significantly enhance the etching rate in the hydrofluoric acid etching solution. It is because surfactant provides hydrophilicity to change the contact angle with enhances the fluid properties of the mixture etchant between GaAs epilayer and GaAs substrate. Arsine gas was released from the etchant solution because the critical reaction product in semiconductor etching is dissolved arsine gas. Arsine gas forms a bubble, which easily displaces the etchant solution, before the AlAs layer was undercut. The results showed that acetone and hydrofluoric acid ratio of about 1:1 for the fastest etching rate of 13.2 μm / min. The etching rate increases about 4 times compared with pure hydrofluoric acid, moreover can shorten the separation time about 70% of GaAs epilayer with GaAs substrate. The results indicate that etching ratio and stability are improved by mixture etchant solution. It is not only saving the epilayer and the etching solution exposure time, but also reducing the damage to the epilayer structure.

Self-etching aspects of a three-step etch-and-rinse adhesive.

PubMed

Bahillo, Jose; Roig, Miguel; Bortolotto, Tissiana; Krejci, Ivo

2013-11-01

The purpose of this study is to assess the marginal adaptation of cavities restored with a three-step etch-and-rinse adhesive, OptiBond FL (OFL) under different application protocols. Twenty-four class V cavities were prepared with half of the margins located in enamel and half in dentin. Cavities were restored with OFL and a microhybrid resin composite (Clearfil AP-X). Three groups (n = 8) that differed in the etching technique were tested with thermomechanical loading, and specimens were subjected to quantitative marginal analysis before and after loading. Micromorphology of etching patters on enamel and dentin were observed with SEM. Data was evaluated with Kruskal-Wallis and Bonferroni post hoc test. Significantly lower percent CM (46.9 ± 19.5) were found after loading on enamel in group 3 compared to group 1 (96.5 ± 5.1) and group 2 (93.1 ± 8.1). However, no significant differences (p = 0.30) were observed on dentin margins. Etching enamel with phosphoric acid but avoiding etching dentin before the application of OFL, optimal marginal adaptation could be obtained, evidencing a self-etching primer effect. A reliable adhesive interface was attained with the application of the three-step etch-and-rinse OFL adhesive with a selective enamel etching, representing an advantage on restoring deep cavities.

Optimization of KOH etching parameters for quantitative defect recognition in n- and p-type doped SiC

NASA Astrophysics Data System (ADS)

Sakwe, S. A.; Müller, R.; Wellmann, P. J.

2006-04-01

We have developed a KOH-based defect etching procedure for silicon carbide (SiC), which comprises in situ temperature measurement and control of melt composition. As benefit for the first time reproducible etching conditions were established (calibration plot, etching rate versus temperature and time); the etching procedure is time independent, i.e. no altering in KOH melt composition takes place, and absolute melt temperature values can be set. The paper describes this advanced KOH etching furnace, including the development of a new temperature sensor resistant to molten KOH. We present updated, absolute KOH etching parameters of n-type SiC and new absolute KOH etching parameters for low and highly p-type doped SiC, which are used for quantitative defect analysis. As best defect etching recipes we found T=530 °C/5 min (activation energy: 16.4 kcal/mol) and T=500 °C/5 min (activation energy: 13.5 kcal/mol) for n-type and p-type SiC, respectively.

Etch pit investigation of free electron concentration controlled 4H-SiC

NASA Astrophysics Data System (ADS)

Kim, Hong-Yeol; Shin, Yun Ji; Kim, Jung Gon; Harima, Hiroshi; Kim, Jihyun; Bahng, Wook

2013-04-01

Etch pits were investigated using the molten KOH selective etching method to examine dependence of etch pit shape and size on free electron concentration. The free electron concentrations of highly doped 4H-silicon carbide (SiC) were controlled by proton irradiation and thermal annealing, which was confirmed by a frequency shift in the LO-phonon-plasmon-coupled (LOPC) mode on micro-Raman spectroscopy. The proton irradiated sample with 5×1015 cm-2 fluence and an intrinsic semi-insulating sample showed clearly classified etch pits but different ratios of threading screw dislocation (TSD) and threading edge dislocation (TED) sizes. Easily classified TEDs and TSDs on proton irradiated 4H-SiC were restored as highly doped 4H-SiC after thermal annealing due to the recovered carrier concentrations. The etched surface of proton irradiated 4H-SiC and boron implanted SiC showed different surface conditions after activation.

AlGaN-Cladding-Free m-Plane InGaN/GaN Laser Diodes with p-Type AlGaN Etch Stop Layers

NASA Astrophysics Data System (ADS)

Farrell, Robert M.; Haeger, Daniel A.; Hsu, Po Shan; Hardy, Matthew T.; Kelchner, Kathryn M.; Fujito, Kenji; Feezell, Daniel F.; Mishra, Umesh K.; DenBaars, Steven P.; Speck, James S.; Nakamura, Shuji

2011-09-01

We present a new method of improving the accuracy and reproducibility of dry etching processes for ridge waveguide InGaN/GaN laser diodes (LDs). A GaN:Al0.09Ga0.91N etch rate selectivity of 11:1 was demonstrated for an m-plane LD with a 40 nm p-Al0.09Ga0.91N etch stop layer (ESL) surrounded by Al-free cladding layers, establishing the effectiveness of AlGaN-based ESLs for controlling etch depth in ridge waveguide InGaN/GaN LDs. These results demonstrate the potential for integrating AlGaN ESLs into commercial device designs where accurate control of the etch depth of the ridge waveguide is necessary for stable, kink-free operation at high output powers.

Defect sensitive etching of hexagonal boron nitride single crystals

NASA Astrophysics Data System (ADS)

Edgar, J. H.; Liu, S.; Hoffman, T.; Zhang, Yichao; Twigg, M. E.; Bassim, Nabil D.; Liang, Shenglong; Khan, Neelam

2017-12-01

Defect sensitive etching (DSE) was developed to estimate the density of non-basal plane dislocations in hexagonal boron nitride (hBN) single crystals. The crystals employed in this study were precipitated by slowly cooling (2-4 °C/h) a nickel-chromium flux saturated with hBN from 1500 °C under 1 bar of flowing nitrogen. On the (0001) planes, hexagonal-shaped etch pits were formed by etching the crystals in a eutectic mixture of NaOH and KOH between 450 °C and 525 °C for 1-2 min. There were three types of pits: pointed bottom, flat bottom, and mixed shape pits. Cross-sectional transmission electron microscopy revealed that the pointed bottom etch pits examined were associated with threading dislocations. All of these dislocations had an a-type burgers vector (i.e., they were edge dislocations, since the line direction is perpendicular to the [ 2 11 ¯ 0 ]-type direction). The pit widths were much wider than the pit depths as measured by atomic force microscopy, indicating the lateral etch rate was much faster than the vertical etch rate. From an Arrhenius plot of the log of the etch rate versus the inverse temperature, the activation energy was approximately 60 kJ/mol. This work demonstrates that DSE is an effective method for locating threading dislocations in hBN and estimating their densities.

ICP etching for InAs-based InAs/GaAsSb superlattice long wavelength infrared detectors

NASA Astrophysics Data System (ADS)

Huang, Min; Chen, Jianxin; Xu, Jiajia; Wang, Fangfang; Xu, Zhicheng; He, Li

2018-05-01

In this work, we study and report the dry etching processes for InAs-based InAs/GaAsSb strain-free superlattice long wavelength infrared (LWIR) detectors. The proper etching parameters were first obtained through the parametric studies of Inductively Coupled Plasma (ICP) etching of both InAs and GaSb bulk materials in Cl2/N2 plasmas. Then an InAs-based InAs/GaAsSb superlattice LWIR detector with PπN structure was fabricated by using the optimized etching parameters. At 80 K, the detector exhibits a 100% cut-off wavelength of 12 μm and a responsivity of 1.5 A/W. Moreover, the dark current density of the device under a bias of -200 mV reaches 5.5 × 10-4 A/cm2, and the R0A is 15 Ω cm2. Our results pave the way towards InAs-based superlattice LWIR detectors with better performances.

A Reactive-Ion Etch for Patterning Piezoelectric Thin Film

NASA Technical Reports Server (NTRS)

Yang, Eui-Hyeok; Wild, Larry

2003-01-01

Reactive-ion etching (RIE) under conditions described below has been found to be a suitable means for patterning piezoelectric thin films made from such materials as PbZr(1-x)Ti(x)O3 or Ba(x)Sr(1.x)TiO3. In the original application for which this particular RIE process was developed, PbZr(1-x)Ti(x)O3 films 0.5 microns thick are to be sandwiched between Pt electrode layers 0.1 microns thick and Ir electrode layers 0.1 microns thick to form piezoelectric capacitor structures. Such structures are typical of piezoelectric actuators in advanced microelectromechanical systems now under development or planned to be developed in the near future. RIE of PbZr(1-x)Ti(x)O3 is usually considered to involve two major subprocesses: an ion-assisted- etching reaction, and a sputtering subprocess that removes reactive byproducts. RIE is favored over other etching techniques because it offers a potential for a high degree of anisotropy, high-resolution pattern definition, and good process control. However, conventional RIE is not ideal for patterning PbZr(1-x)Ti(x)O3 films at a thickness as great as that in the original intended application. In order to realize the potential benefits mentioned above, it is necessary to optimize process conditions . in particular, the composition of the etching gas and the values of such other process parameters as radio-frequency power, gas pressure, gas-flow rate, and duration of the process. Guidelines for determining optimum conditions can be obtained from experimental determination of etch rates as functions of these parameters. Etch-gas mixtures of BCl3 and Cl2, some also including Ar, have been found to offer a high degree of selectivity as needed for patterning of PbZr(1-x)Ti(x)O3 films on top of Ir electrode layers in thin-film capacitor structures. The selectivity is characterized by a ratio of approx.10:1 (rate of etching PbZr(1-x)Ti(x)O3 divided by rate of etching Ir and IrO(x)). At the time of reporting the information for this article, several experiments on RIE in BCl3 and Cl2 (and sometimes Ar) had demonstrated the 10:1 selectivity ratio, and further experiments to enhance understanding and obtain further guidance for optimizing process conditions were planned.

Selective Dry Etch for Defining Ohmic Contacts for High Performance ZnO TFTs

DTIC Science & Technology

2014-03-27

scale, high-frequency ZnO thin - film transistors (TFTs) could be fabricated. Molybdenum, tantalum, titanium tungsten 10-90, and tungsten metallic contact... thin - film transistor layout utilized in the thesis research . . . . . 42 3.4 Process Flow Diagram for Optical and e-Beam Devices...TFT thin - film transistor TLM transmission line model UV ultra-violet xvii SELECTIVE DRY ETCH FOR DEFINING OHMIC CONTACTS FOR HIGH PERFORMANCE ZnO TFTs

High quality of InAsSb epilayer with cutoff wavelength longer than 10 μm grown on GaAs by the modified LPE technique

NASA Astrophysics Data System (ADS)

Hu, S. H.; Sun, C. H.; Sun, Y.; Ge, J.; Wang, R.; Wu, J.; Wang, Q. W.; Dai, N.

2009-04-01

The InAsSb epilayers with a cutoff wavelength of 11.5 μm were successfully grown on highly lattice-mismatched semi-insulating (1 0 0) GaAs substrate by the modified liquid phase epitaxy (LPE) technique. Fourier transform infrared (FTIR) transmission spectrum revealed a strong band gap narrowing for this alloy. The electrical properties were investigated by the Van der Pauw measurements at 300 and 77 K. InAsSb epilayers showed high Hall mobilities being 11,800 cm 2/V s at room temperature (RT). After an annealing treament for 10 h, the electron mobility at 77 K were improved from 1730 cm 2/V s (prior to annealing) to 13,470 cm 2/V s. Wet etching was used to display the surface etch pits prior to and after annealing treatment, showing that the mobility improvement was due to the reduction of the etch pits density.

Radial tunnel diodes based on InP/InGaAs core-shell nanowires

NASA Astrophysics Data System (ADS)

Tizno, Ofogh; Ganjipour, Bahram; Heurlin, Magnus; Thelander, Claes; Borgström, Magnus T.; Samuelson, Lars

2017-03-01

We report on the fabrication and characterization of radial tunnel diodes based on InP(n+)/InGaAs(p+) core-shell nanowires, where the effect of Zn-dopant precursor flow on the electrical properties of the devices is evaluated. Selective and local etching of the InGaAs shell is employed to access the nanowire core in the contact process. Devices with an n+-p doping profile show normal diode rectification, whereas n+-p+ junctions exhibit typical tunnel diode characteristics with peak-to-valley current ratios up to 14 at room temperature and 100 at 4.2 K. A maximum peak current density of 28 A/cm2 and a reverse current density of 7.3 kA/cm2 at VSD = -0.5 V are extracted at room temperature after normalization with the effective junction area.

Nanorods on surface of GaN-based thin-film LEDs deposited by post-annealing after photo-assisted chemical etching

NASA Astrophysics Data System (ADS)

Chen, Lung-Chien; Lin, Wun-Wei; Liu, Te-Yu

2017-01-01

This study investigates the optoelectronic characteristics of gallium nitride (GaN)-based thin-film light-emitting diodes (TF-LEDs) that are formed by a two-step transfer process that involves wet etching and post-annealing. In the two-step transfer process, GaN LEDs were stripped from sapphire substrates by the laser lift-off (LLO) method using a KrF laser and then transferred onto ceramic substrates. Ga-K nanorods were formed on the surface of the GaN-based TF-LEDs following photo-assisted chemical etching and photo-enhanced post-annealing at 100 °C for 1 min. As a result, the light output power of GaN-based TF-LEDs with wet etching and post-annealing was over 72% more than that of LEDs that did not undergo these treatments.

Note: Dissolved hydrogen detection in power transformer oil based on chemically etched fiber Bragg grating.

PubMed

Jiang, Jun; Ma, Guo-ming; Song, Hong-tu; Zhou, Hong-yang; Li, Cheng-rong; Luo, Ying-ting; Wang, Hong-bin

2015-10-01

A fiber Bragg grating (FBG) sensor based on chemically etched cladding to detect dissolved hydrogen is proposed and studied in this paper. Low hydrogen concentration tests have been carried out in mixed gases and transformer oil to investigate the repeatability and sensitivity. Moreover, to estimate the influence of etched cladding thickness, a physical model of FBG-based hydrogen sensor is analyzed. Experimental results prove that thin cladding chemically etched by HF acid solution improves the response to hydrogen detection in oil effectively. At last, the sensitivity of FBG sensor chemically etched 16 μm could be as high as 0.060 pm/(μl/l), increased by more than 30% in comparison to un-etched FBG.

Structures Self-Assembled Through Directional Solidification

NASA Technical Reports Server (NTRS)

Dynys, Frederick W.; Sayir, Ali

2005-01-01

Nanotechnology has created a demand for new fabrication methods with an emphasis on simple, low-cost techniques. Directional solidification of eutectics (DSE) is an unconventional approach in comparison to low-temperature biomimetic approaches. A technical challenge for DSE is producing microstructural architectures on the nanometer scale. In both processes, the driving force is the minimization of Gibb's free energy. Selfassembly by biomimetic approaches depends on weak interaction forces between organic molecules to define the architectural structure. The architectural structure for solidification depends on strong chemical bonding between atoms. Constituents partition into atomic-level arrangements at the liquid-solid interface to form polyphase structures, and this atomic-level arrangement at the liquid-solid interface is controlled by atomic diffusion and total undercooling due to composition (diffusion), kinetics, and curvature of the boundary phases. Judicious selection of the materials system and control of the total undercooling are the keys to producing structures on the nanometer scale. The silicon-titanium silicide (Si-TiSi2) eutectic forms a rod structure under isothermal cooling conditions. At the NASA Glenn Research Center, directional solidification was employed along with a thermal gradient to promote uniform rods oriented with the thermal gradient. The preceding photomicrograph shows the typical transverse microstructure of a solidified Si-TiSi2 eutectic composition. The dark and light gray regions are Si and TiSi2, respectively. Preferred rod orientation along the thermal gradient was poor. The ordered TiSi2 rods have a narrow distribution in diameter of 2 to 3 m, as shown. The rod diameter showed a weak dependence on process conditions. Anisotropic etch behavior between different phases provides the opportunity to fabricate structures with high aspect ratios. The photomicrographs show the resulting microstructure after a wet chemical etch and a dry plasma etch. The wet chemical etches the silicon away, exposing the TiSi2 rods, whereas plasma etching preferentially etches the Si-TiSi2 interface to form a crater. The porous architectures are applicable to fabricating microdevices or creating templates for part fabrication. The porous rod structure can serve as a platform for fabricating microplasma devices for propulsion or microheat exchangers and for fabricating microfilters for miniatured chemical reactors. Although more work is required, self-assembly from DSE can have a role in microdevice fabrication.

Metal-assisted chemical etch porous silicon formation method

DOEpatents

Li, Xiuling; Bohn, Paul W.; Sweedler, Jonathan V.

2004-09-14

A thin discontinuous layer of metal such as Au, Pt, or Au/Pd is deposited on a silicon surface. The surface is then etched in a solution including HF and an oxidant for a brief period, as little as a couple seconds to one hour. A preferred oxidant is H.sub.2 O.sub.2. Morphology and light emitting properties of porous silicon can be selectively controlled as a function of the type of metal deposited, Si doping type, silicon doping level, and/or etch time. Electrical assistance is unnecessary during the chemical etching of the invention, which may be conducted in the presence or absence of illumination.

Controlled core removal from a D-shaped optical fiber.

PubMed

Markos, Douglas J; Ipson, Benjamin L; Smith, Kevin H; Schultz, Stephen M; Selfridge, Richard H; Monte, Thomas D; Dyott, Richard B; Miller, Gregory

2003-12-20

The partial removal of a section of the core from a continuous D-shaped optical fiber is presented. In the core removal process, selective chemical etching is used with hydrofluoric (HF) acid. A 25% HF acid solution removes the cladding material above the core, and a 5% HF acid solution removes the core. A red laser with a wavelength of 670 nm is transmitted through the optical fiber during the etching. The power transmitted through the optical fiber is correlated to the etch depth by scanning electron microscope imaging. The developed process provides a repeatable method to produce an optical fiber with a specific etch depth.

Application of cyclic fluorocarbon/argon discharges to device patterning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzler, Dominik, E-mail: dmetzler@umd.edu; Uppireddi, Kishore; Bruce, Robert L.

2016-01-15

With increasing demands on device patterning to achieve smaller critical dimensions and pitches for the 5 nm node and beyond, the need for atomic layer etching (ALE) is steadily increasing. In this work, a cyclic fluorocarbon/Ar plasma is successfully used for ALE patterning in a manufacturing scale reactor. Self-limited etching of silicon oxide is observed. The impact of various process parameters on the etch performance is established. The substrate temperature has been shown to play an especially significant role, with lower temperatures leading to higher selectivity and lower etch rates, but worse pattern fidelity. The cyclic ALE approach established with thismore » work is shown to have great potential for small scale device patterning, showing self-limited etching, improved uniformity and resist mask performance.« less

The effect of SF6 addition in a Cl2/Ar inductively coupled plasma for deep titanium etching

NASA Astrophysics Data System (ADS)

Laudrel, E.; Tillocher, T.; Meric, Y.; Lefaucheux, P.; Boutaud, B.; Dussart, R.

2018-05-01

Titanium is a material of interest for the biomedical field and more particularly for body implantable devices. Titanium deep etching by plasma was carried out in an inductively coupled plasma with a chlorine-based chemistry for the fabrication of titanium-based microdevices. Bulk titanium etch rate was first studied in Cl2/Ar plasma mixture versus the source power and the self-bias voltage. The plasma was characterized by Langmuir probe and by optical emission spectroscopy. The addition of SF6 in the plasma mixture was investigated. Titanium etch rate was optimized and reached a value of 2.4 µm · min-1. The nickel hard mask selectivity was also enhanced. The etched titanium surface roughness was reduced significantly.

Application of cyclic fluorocarbon/argon discharges to device patterning

DOE PAGES

Metzler, Dominik; Uppiredi, Kishore; Bruce, Robert L.; ...

2015-11-13

With increasing demands on device patterning to achieve smaller critical dimensions and pitches for the 5nm node and beyond, the need for atomic layer etching (ALE) is steadily increasing. In this study, a cyclic fluorocarbon/Ar plasma is successfully used for ALE patterning in a manufacturing scale reactor. Self-limited etching of silicon oxide is observed. The impact of various process parameters on the etch performance is established. The substrate temperature has been shown to play an especially significant role, with lower temperatures leading to higher selectivity and lower etch rates, but worse pattern fidelity. The cyclic ALE approach established with thismore » work is shown to have great potential for small scale device patterning, showing self-limited etching, improved uniformity and resist mask performance.« less

Microchannel neural interface manufacture by stacking silicone and metal foil laminae

NASA Astrophysics Data System (ADS)

Lancashire, Henry T.; Vanhoestenberghe, Anne; Pendegrass, Catherine J.; Ajam, Yazan Al; Magee, Elliot; Donaldson, Nick; Blunn, Gordon W.

2016-06-01

Objective. Microchannel neural interfaces (MNIs) overcome problems with recording from peripheral nerves by amplifying signals independent of node of Ranvier position. Selective recording and stimulation using an MNI requires good insulation between microchannels and a high electrode density. We propose that stacking microchannel laminae will improve selectivity over single layer MNI designs due to the increase in electrode number and an improvement in microchannel sealing. Approach. This paper describes a manufacturing method for creating MNIs which overcomes limitations on electrode connectivity and microchannel sealing. Laser cut silicone—metal foil laminae were stacked using plasma bonding to create an array of microchannels containing tripolar electrodes. Electrodes were DC etched and electrode impedance and cyclic voltammetry were tested. Main results. MNIs with 100 μm and 200 μm diameter microchannels were manufactured. High electrode density MNIs are achievable with electrodes present in every microchannel. Electrode impedances of 27.2 ± 19.8 kΩ at 1 kHz were achieved. Following two months of implantation in Lewis rat sciatic nerve, micro-fascicles were observed regenerating through the MNI microchannels. Significance. Selective MNIs with the peripheral nervous system may allow upper limb amputees to control prostheses intuitively.

Process technologies of MPACVD planar waveguide devices and fiber attachment

NASA Astrophysics Data System (ADS)

Li, Cheng-Chung; Qian, Fan; Boudreau, Robert A.; Rowlette, John R., Sr.; Bowen, Terry P.

1999-03-01

Optical circuits based on low-loss glass waveguide on silicon are a practical and promising approach to integrate different functional components. Fiber attachment to planar waveguide provides a practical application for optical communications. Microwave Plasma Assisted Chemical Vapor Deposition (MPACVD) produces superior quality, low birefringence, low-loss, planar waveguides for integrated optical devices. Microwave plasma initiates the chemical vapor of SiCl4, GeCl4 and oxygen. A Ge-doped silica layer is thus deposited with a compatible high growth rate (i.e. 0.4 - 0.5 micrometer/min). Film properties are based on various parameters, such as chemical flow rates, chamber pressure and temperature, power level and injector design. The resultant refractive index can be varied between 1.46 (i.e. pure silica) and 1.60 (i.e. pure germania). Waveguides can be fabricated with any desired refractive index profile. Standard photolithography defines the waveguide pattern on a mask layer. The core layer is removed by plasma dry etch which has been investigated by both reactive ion etch (RIE) and inductively coupled plasma (ICP) etch. Etch rates of 3000 - 4000 angstrom/min have been achieved using ICP compared to typical etch rates of 200 - 300 angstrom/min using conventional RIE. Planar waveguides offer good mode matching to optical fiber. A polished fiber end can be glued to the end facet of waveguide with a very low optical coupling loss. In addition, anisotropic etching of silicon V- grooves provides a passive alignment capability. Epoxy and solder were used to fix the fiber within the guiding groove. Several designs of waveguide-fiber attachment will be discussed.

Effect of substrate dislocations on the Hg in-diffusion in CdZnTe substrates used for HgCdTe epilayer growth

NASA Astrophysics Data System (ADS)

Kumar, Shiv; Kapoor, A. K.; Nagpal, A.; Sharma, S.; Verma, D.; Kumar, A.; Raman, R.; Basu, P. K.

2006-12-01

Chemical-etched HgCdTe epilayers grown onto CdZnTe substrates have been studied using defect etching and EDS on cleaved (1 1 0) face. Formation of etch pits and mercury (Hg) in-diffusion into CZT substrate has been correlated with the substrate quality i.e. the presence of dislocations around second phase inclusions. That the Hg in-diffusion takes place through these dislocations is authenticated by the presence of Te-inclusions in substrates where large density of etch pits are revealed after chemical etching. X-ray rocking curve measurements were carried out to reveal crystalline quality of the substrates. FTIR spectroscopy indicates low transmission values and absence of interference fringes in MCT epilayers with large Hg diffusion. Hg diffusion into CZT substrate upto 25 μm in samples with low FWHM values and upto 250 μm in samples with multiple peaks and high FWHM values was observed.

Computer acquired performance data from an etched-rhenium, molybdenum planar diode

NASA Technical Reports Server (NTRS)

Manista, E. J.

1972-01-01

Performance data from an etched-rhenium, molybdenum thermionic converter are presented. The planar converter has a guard-ringed collector and a fixed spacing of 0.254 mm (10 mils). The data were acquired by using a computer and are available on microfiche as individual or composite parametric current, voltage curves. The parameters are the temperatures of the emitter T sub E, collector T sub C and cesium reservoir T sub R. The composite plots have constant T sub E, and varying T sub C or T sub R, or both. The envelope and composite plots having constant I sub E are presented. The diode was tested at increments between 1500 and 2000 K for the emitter, 750 and 1100 K for the collector, and 540 and 640 K for the reservoir. In all, 774 individual current, voltage curves were obtained.

Evaluation of erbium:YAG and holmium:YAG laser radiation and dental hard tissue

NASA Astrophysics Data System (ADS)

Attrill, David Cameron

Lasers have become increasingly established in medicine as effective alternatives or adjuncts to conventional techniques. In dentistry, several clinical laser systems have been developed and marketed, but their applications have been limited to soft tissue surgery. To date, no laser has been capable of effectively cutting or modifying the highly mineralised dental tissues of enamel and dentine. The aim of this study was to evaluate two new laser systems for use in dentistry through a series of in vitro experiments. Both generic erbium and holmium lasers have theoretically superior operating characteristics over currently established lasers for applications with dental hard tissues. The two lasers investigated in this study were pulsed Er:YAG (lambda=2.94) a.m. and Cr-Tm-Ho:YAG (lambda=2.1mu.m). Both operated with a macropulse duration of approximately 200lambdas, at pulse repetition rates of 2-8Hz and mean pulse energies up to 230mJ. Radiation was focused using CaF[2] lenses (f=50-120mm). The lasers could be operated with or without the addition of a surface water film at the interaction site. Tissue removal efficiency was expressed as a latent heat of ablation (LHA, kJ/cm[3]) using a modification of the technique described by Charlton et al. (1990). The mean LHA's for the Er:YAG laser were 6.24kJ/cm[3] and 22.99kJ/cm[3] with dentine and enamel respectively without water, and 10.07kJ/cm[3] and 18.73kJ/cm[3] for dentine and enamel with water. The Cr-Tm-Ho:YAG laser was unable to effectively remove enamel at the fluences and pulse energies available; the mean LHA's for the Cr-Tm- Ho:YAG laser with dentine were 82.79kJ/cm3 and 57.57kJ/cm3 with and without water respectively. The Cr-Tm-Ho;YAG was approximately 8-9 times less efficient for tissue removal than the Er:YAG system. Er:YAG tissue removal with water was characterised by clean "surgical" cuts, comparable in histological appearance to those obtained using conventional instrumentation. Some thermal disruption and evidence of molten enamel in particular were apparent when the Er:YAG laser was used without water. The Cr-Tm-Ho;YAG laser produced extensive charring and carbonisation of tissues. It was concluded that this laser was unsuitable for clinical applications directed at the removal or modification of enamel and dentine, particularly as the Er:YAG laser offers superior qualities. Further research with the Cr-Tm-Ho:YAG laser was discontinued. A comparison of the mean shear bond strengths of a composite (ZlOO, 3M Dental Products) bonded to enamel was made using either a conventional acid etch technique or one of a range of experimental Er:YAG laser etching configurations. The mean values for acid etching (16.6 MPa) were in all cases significantly greater (p<0.01, Bonferroni) than those obtained with laser etching. The optimal laser etching parameters were a fluence of 24J/cm[2] (1/e[2] calculation) with water resulting in a mean bond strength of 11.5 MPa. This figure represents approximately 70% of the mean obtained with acid etching, and was significantly greater (p<0.01, Bonferroni) than the mean recorded for non etched negative control surfaces (4.4 MPa). Histological evaluation of the etched surfaces demonstrated clear differences in the etching patterns observed between laser and acid etching. Some surface cracking was noted in most laser etched surfaces, but the extent of this was minimised when the laser was applied in conjunction with a surface water film. Pulpal temperature increments following Er:YAG laser irradiation were significantly lower in teeth prepared with water than without (paired t-test, p<0.01). The largest increment in samples prepared with water was 3.9°C, compared to 24.7°C without water. The principal determinant of the temperature increment in either group was the total delivered energy, up to 140J. Linear regression modelling predicts that continuous irradiation up to 160J with water would not result in iatrogenic pulpal damage. In conclusion, the Er:YAG laser was shown to be an effective tool for cutting and modifying dental hard tissues. It almost certainly offers the best combination of safety, efficiency and speed of any laser system designed for preparing cavities. The laser must be used in conjunction with a water coolant on the tissues to minimise the possibility of iatrogenic damage, improve the quality of the laser cuts and in some circumstances increase cutting efficiency. The Er:YAG laser has shown much promise in these in vitro experiments and its progression to clinical use is supported. The Cr-Tm-Ho:YAG laser is significantly less efficient and in vitro results are unfavourable in comparison with the Er:YAG laser. Its clinical use is not supported.

Method for forming suspended micromechanical structures

DOEpatents

Fleming, James G.

2000-01-01

A micromachining method is disclosed for forming a suspended micromechanical structure from {111} crystalline silicon. The micromachining method is based on the use of anisotropic dry etching to define lateral features of the structure which are etched down into a {111}-silicon substrate to a first etch depth, thereby forming sidewalls of the structure. The sidewalls are then coated with a protection layer, and the substrate is dry etched to a second etch depth to define a spacing of the structure from the substrate. A selective anisotropic wet etchant (e.g. KOH, EDP, TMAH, NaOH or CsOH) is used to laterally undercut the structure between the first and second etch depths, thereby forming a substantially planar lower surface of the structure along a {111} crystal plane that is parallel to an upper surface of the structure. The lateral extent of undercutting by the wet etchant is controlled and effectively terminated by either timing the etching, by the location of angled {111}-silicon planes or by the locations of preformed etch-stops. This present method allows the formation of suspended micromechanical structures having large vertical dimensions and large masses while allowing for detailed lateral features which can be provided by dry etch definition. Additionally, the method of the present invention is compatible with the formation of electronic circuitry on the substrate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swain, Basudev, E-mail: swain@iae.re.kr; Mishra, Chinmayee; Hong, Hyun Seon

Sustainable valorization processes for selective recovery of pure copper nanopowder from Indium-Tin-Oxide (ITO) etching wastewater by various wet chemical reduction processes, their chemistry has been investigated and compared. After the indium recovery by solvent extraction from ITO etching wastewater, the same is also an environmental challenge, needs to be treated before disposal. After the indium recovery, ITO etching wastewater contains 6.11 kg/m{sup 3} of copper and 1.35 kg/m{sup 3} of aluminum, pH of the solution is very low converging to 0 and contain a significant amount of chlorine in the media. In this study, pure copper nanopowder was recovered usingmore » various reducing reagents by wet chemical reduction and characterized. Different reducing agents like a metallic, an inorganic acid and an organic acid were used to understand reduction behavior of copper in the presence of aluminum in a strong chloride medium of the ITO etching wastewater. The effect of a polymer surfactant Polyvinylpyrrolidone (PVP), which was included to prevent aggregation, to provide dispersion stability and control the size of copper nanopowder was investigated and compared. The developed copper nanopowder recovery techniques are techno-economical feasible processes for commercial production of copper nanopowder in the range of 100–500 nm size from the reported facilities through a one-pot synthesis. By all the process reported pure copper nanopowder can be recovered with>99% efficiency. After the copper recovery, copper concentration in the wastewater reduced to acceptable limit recommended by WHO for wastewater disposal. The process is not only beneficial for recycling of copper, but also helps to address environment challenged posed by ITO etching wastewater. From a complex wastewater, synthesis of pure copper nanopowder using various wet chemical reduction route and their comparison is the novelty of this recovery process. - Highlights: • From the Indium-Tin-Oxide etching wastewater, copper nanopowder was synthesized. • Solution chemistry of ITO etching wastewater is addressed. • A techno-economical feasible, environment friendly and occupational safe process. • Brings back the material to production stream and address the circular economy. • A cradle to cradle technology management lowers the futuristic carbon economy.« less

Low damage dry etch for III-nitride light emitters

NASA Astrophysics Data System (ADS)

Nedy, Joseph G.; Young, Nathan G.; Kelchner, Kathryn M.; Hu, Yanling; Farrell, Robert M.; Nakamura, Shuji; DenBaars, Steven P.; Weisbuch, Claude; Speck, James S.

2015-08-01

We have developed a dry etch process for the fabrication of lithographically defined features close to light emitting layers in the III-nitride material system. The dry etch was tested for its effect on the internal quantum efficiency of c-plane InGaN quantum wells using the photoluminescence of a test structure with two active regions. No change was observed in the internal quantum efficiency of the test active region when the etched surface was greater than 71 nm away. To demonstrate the application of the developed dry etch process, surface-etched air gaps were fabricated 275 nm away from the active region of an m-plane InGaN/GaN laser diode and served as the waveguide upper cladding. Electrically injected lasing was observed without the need for regrowth or recovery anneals. This dry etch opens up a new design tool that can be utilized in the next generation of GaN light emitters.

Dynamic SEM wear studies of tungsten carbide cermets. [friction and wear experiments

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Buckley, D. H.

1975-01-01

Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

InAlAs photovoltaic cell design for high device efficiency

DOE PAGES

Smith, Brittany L.; Bittner, Zachary S.; Hellstroem, Staffan D.; ...

2017-04-17

This study presents a new design for a single-junction InAlAs solar cell, which reduces parasitic absorption losses from the low band-gap contact layer while maintaining a functional window layer by integrating a selective etch stop. The etch stop is then removed prior to depositing an anti-reflective coating. The final cell had a 17.9% efficiency under 1-sun AM1.5 with an anti-reflective coating. Minority carrier diffusion lengths were extracted from external quantum efficiency data using physics-based device simulation software yielding 170 nm in the n-type emitter and 4.6 um in the p-type base, which is more than four times the diffusion lengthmore » previously reported for a p-type InAlAs base. In conclusion, this report represents significant progress towards a high-performance InAlAs top cell for a triple-junction design lattice-matched to InP.« less

Dynamic SEM wear studies of tungsten carbide cermets

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Buckley, D. H.

1975-01-01

Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined. Etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the WC and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation. The wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

Novel Zirconia Surface Treatments for Enhanced Osseointegration: Laboratory Characterization

PubMed Central

Ewais, Ola H.; Al Abbassy, Fayza; Ghoneim, Mona M.; Aboushelib, Moustafa N.

2014-01-01

Purpose. The aim of this study was to evaluate three novel surface treatments intended to improve osseointegration of zirconia implants: selective infiltration etching treatment (SIE), fusion sputtering (FS), and low pressure particle abrasion (LPPA). The effects of surface treatments on roughness, topography, hardness, and porosity of implants were also assessed. Materials and Methods. 45 zirconia discs (19 mm in diameter × 3 mm in thickness) received 3 different surface treatments: selective infiltration etching, low pressure particle abrasion with 30 µm alumina, and fusion sputtering while nontreated surface served as control. Surface roughness was evaluated quantitatively using profilometery, porosity was evaluated using mercury prosimetry, and Vickers microhardness was used to assess surface hardness. Surface topography was analyzed using scanning and atomic force microscopy (α = 0.05). Results. There were significant differences between all groups regarding surface roughness (F = 1678, P < 0.001), porosity (F = 3278, P < 0.001), and hardness (F = 1106.158, P < 0.001). Scanning and atomic force microscopy revealed a nanoporous surface characteristic of SIE, and FS resulted in the creation of surface microbeads, while LPPA resulted in limited abrasion of the surface. Conclusion. Within the limitations of the study, changes in surface characteristics and topography of zirconia implants have been observed after different surface treatment approaches. Thus possibilities for enhanced osseointegration could be additionally offered. PMID:25349610

Does active application of universal adhesives to enamel in self-etch mode improve their performance?

PubMed

Loguercio, Alessandro D; Muñoz, Miguel Angel; Luque-Martinez, Issis; Hass, Viviane; Reis, Alessandra; Perdigão, Jorge

2015-09-01

To evaluate the effect of adhesion strategy on the enamel microshear bond strengths (μSBS), etching pattern, and in situ degree of conversion (DC) of seven universal adhesives. 84 extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 21 groups, according to the combination of the main factors adhesive (AdheSE Universal [ADU], All-Bond Universal [ABU], Clearfil Universal [CFU], Futurabond U [FBU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and adhesion strategy (etch-and-rinse, active self-etch, and passive self-etch). Specimens were stored in water (37°C/24h) and tested at 1.0mm/min (μSBS). Enamel-resin interfaces were evaluated for DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field-emission scanning electron microscope (direct and replica techniques). Data were analyzed with two-way ANOVA and Tukey's test (α=0.05). Active self-etch application increased μSBS and DC for five out of the seven universal adhesives when compared to passive application (p<0.001). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. A slight improvement in etching ability was observed in active self-etch application compared to that of passive self-etch application. Replicas of GBP and PBE applied in active self-etch mode displayed morphological features compatible with water droplets. The DC of GBP and PBE were not affected by the application/strategy mode. In light of the improved performance of universal adhesives when applied actively in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel. The active application of universal adhesives in self-etch mode may be a practical alternative to enamel etching in specific clinical situations. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ion-enhanced chemical etching of ZrO2 in a chlorine discharge

NASA Astrophysics Data System (ADS)

Sha, Lin; Cho, Byeong-Ok; Chang, Jane P.

2002-09-01

Chlorine plasma is found to chemically etch ZrO2 thin films in an electron cyclotron resonance reactor, and the etch rate scaled linearly with the square root of ion energy at high ion energies with a threshold energy between 12-20 eV. The etching rate decreased monotonically with increasing chamber pressures, which corresponds to reduced electron temperatures. Optical emission spectroscopy and quadrupole mass spectrometry were used to identify the reaction etching products. No Zr, O, or ZrCl were detected as etching products, but highly chlorinated zirconium compounds (ZrCl2, ZrCl3, and ZrCl4) and ClO were found to be the dominant etching products. ZrCl3 was the dominant etching products at low ion energies, while ZrCl4 became dominant at higher ion energies. This is consistent with greater momentum transfer and enhanced surface chlorination, as determined by x-ray photoelectron spectroscopy, at increased ion energies. Several ion-enhanced chemical reactions are proposed to contribute to the ZrO2 etching. copyright 2002 American Vacuum Society.

Atomic layer deposited lithium aluminum oxide: (In)dependency of film properties from pulsing sequence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miikkulainen, Ville, E-mail: ville.miikkulainen@helsinki.fi; Nilsen, Ola; Fjellvåg, Helmer

Atomic layer deposition (ALD) holds markedly high potential of becoming the enabling method for achieving the three-dimensional all-solid-state thin-film lithium ion battery (LiB). One of the most crucial components in such a battery is the electrolyte that needs to hold both low electronic conductivity and at least fair lithium ion conductivity being at the same time pinhole free. To obtain these desired properties in an electrolyte film, one necessarily has to have a good control over the elemental composition of the deposited material. The present study reports on the properties of ALD lithium aluminum oxide (Li{sub x}Al{sub y}O{sub z}) thinmore » films. In addition to LiB electrolyte applications, Li{sub x}Al{sub y}O{sub z} is also a candidate low dielectric constant (low-k) etch stop and diffusion barrier material in nanoelectronics applications. The Li{sub x}Al{sub y}O{sub z} films were deposited employing trimethylaluminum-O{sub 3} and lithium tert-butoxide-H{sub 2}O for Al{sub 2}O{sub 3} and Li{sub 2}O/LiOH, respectively. The composition was aimed to be controlled by varying the pulsing ratio of those two binary oxide ALD cycles. The films were characterized by several methods for composition, crystallinity and phase, electrical properties, hardness, porosity, and chemical environment. Regardless of the applied pulsing ratio of Al{sub 2}O{sub 3} and Li{sub 2}O/LiOH, all the studied ALD Li{sub x}Al{sub y}O{sub z} films of 200 and 400 nm in thickness were polycrystalline in the orthorhombic β-LiAlO{sub 2} phase and also very similar to each other with respect to composition and other studied properties. The results are discussed in the context of both fundamental ALD chemistry and applicability of the films as thin-film LiB electrolytes and low-k etch stop and diffusion barriers.« less

Conductive multi-walled boron nitride nanotubes by catalytic etching using cobalt oxide.

PubMed

Kim, Do-Hyun; Jang, Ho-Kyun; Kim, Min-Seok; Kim, Sung-Dae; Lee, Dong-Jin; Kim, Gyu Tae

2017-01-04

Boron nitride nanotubes (BNNTs) are ceramic compounds which are hardly oxidized below 1000 °C due to their superior thermal stability. Also, they are electrically almost insulators with a large band gap of 5 eV. Thus, it is a challenging task to etch BNNTs at low temperature and to convert their electrical properties to a conductive behavior. In this study, we demonstrate that BNNTs can be easily etched at low temperature by catalytic oxidation, resulting in an electrically conductive behavior. For this, multi-walled BNNTs (MWBNNTs) impregnated with Co precursor (Co(NO 3 ) 2 ·6H 2 O) were simply heated at 350 °C under air atmosphere. As a result, diverse shapes of etched structures such as pits and thinned walls were created on the surface of MWBNNTs without losing the tubular structure. The original crystallinity was still kept in the etched MWBNNTs in spite of oxidation. In the electrical measurement, MWBNNTs with a large band gap were converted to electrical conductors after etching by catalytic oxidation. Theoretical calculations indicated that a new energy state in the gap and a Fermi level shift contributed to MWBNNTs being conductive.

A novel 2D silicon nano-mold fabrication technique for linear nanochannels over a 4 inch diameter substrate

PubMed Central

Yin, Zhifu; Qi, Liping; Zou, Helin; Sun, Lei

2016-01-01

A novel low-cost 2D silicon nano-mold fabrication technique was developed based on Cu inclined-deposition and Ar+ (argon ion) etching. With this technique, sub-100 nm 2D (two dimensional) nano-channels can be etched economically over the whole area of a 4 inch n-type <100> silicon wafer. The fabricating process consists of only 4 steps, UV (Ultraviolet) lithography, inclined Cu deposition, Ar+ sputter etching, and photoresist & Cu removing. During this nano-mold fabrication process, we investigated the influence of the deposition angle on the width of the nano-channels and the effect of Ar+ etching time on their depth. Post-etching measurements showed the accuracy of the nanochannels over the whole area: the variation in width is 10%, in depth it is 11%. However, post-etching measurements also showed the accuracy of the nanochannels between chips: the variation in width is 2%, in depth it is 5%. With this newly developed technology, low-cost and large scale 2D nano-molds can be fabricated, which allows commercial manufacturing of nano-components over large areas. PMID:26752559

Comparative analysis of barium titanate thin films dry etching using inductively coupled plasmas by different fluorine-based mixture gas

PubMed Central

2014-01-01

In this work, the inductively coupled plasma etching technique was applied to etch the barium titanate thin film. A comparative study of etch characteristics of the barium titanate thin film has been investigated in fluorine-based (CF4/O2, C4F8/O2 and SF6/O2) plasmas. The etch rates were measured using focused ion beam in order to ensure the accuracy of measurement. The surface morphology of etched barium titanate thin film was characterized by atomic force microscope. The chemical state of the etched surfaces was investigated by X-ray photoelectron spectroscopy. According to the experimental result, we monitored that a higher barium titanate thin film etch rate was achieved with SF6/O2 due to minimum amount of necessary ion energy and its higher volatility of etching byproducts as compared with CF4/O2 and C4F8/O2. Low-volatile C-F compound etching byproducts from C4F8/O2 were observed on the etched surface and resulted in the reduction of etch rate. As a result, the barium titanate films can be effectively etched by the plasma with the composition of SF6/O2, which has an etch rate of over than 46.7 nm/min at RF power/inductively coupled plasma (ICP) power of 150/1,000 W under gas pressure of 7.5 mTorr with a better surface morphology. PMID:25278821

SHI induced nano track polymer filters and characterization

NASA Astrophysics Data System (ADS)

Vijay, Y. K.

2009-07-01

Swift heavy ion irradiation produces damage in polymers in the form of latent tracks. Latent tracks can be enlarged by etching it in a suitable etchant and thus nuclear track etch membrane can be formed for gas permeation / purification in particular for hydrogen where the molecular size is very small. By applying suitable and controlled etching conditions well defined tracks can be formed for specific applications of the membranes. After etching gas permeation method is used for characterizing the tracks. In the present work polycarbonate (PC) of various thickness were irradiated with energetic ion beam at Inter University Accelerator Centre (IUAC), New Delhi. Nuclear tracks were modified by etching the PC in 6N NaOH at 60 (±1) °C from both sides for different times to produce track etch membranes. At critical etch time the etched pits from both the sides meet a rapid increase in gas permeation was observed. Permeability of hydrogen and carbon dioxide has been measured in samples etched for different times. The latent tracks produced by SHI irradiation in the track etch membranes show enhancement of free volume of the polymer. Nano filters are separation devices for the mixture of gases, different ions in the solution and isotopes and isobars separations. The polymer thin films with controlled porosity finding it self as best choice. However, the permeability and selectivity of these polymer based membrane filters are very important at the nano scale separation. The Swift Heavy Ion (SHI) induced nuclear track etched polymeric films with controlled etching have been attempted and characterized as nano scale filters.

Use of sequential infiltration synthesis to improve the pattern transfer of PS-b-PLA DSA (Conference Presentation)

NASA Astrophysics Data System (ADS)

Evangelio Araujo, Laura; Fernández-Regúlez, Marta; Chevalier, Xavier; Nicolet, Célia; Cayrefourcq, Ian; Navarro, Christophe; Fleury, Guillaume; Pérez-Murano, Francesc

2017-03-01

Directed self-assembly of block copolymers is considered one of the candidates to fulfill the requirements of the next technological nodes [1,2]. Polymer domains are aligned by using a chemical and/or a topographical pre-pattern in which preferential surfaces to one of the two blocks or neutral wetting areas are created. In particular, polystyrene-block-polymetylmethacrylate (PS-b-PMMA) has been extensively studied during the last years showing strong capabilities to define periodic nanostructures. However, the relatively low Flory-Huggins parameter and, the resulting low segregation strength of PS-b-PMMA systems, limit their achievable resolution to around 11 nm [3]. The application of block copolymer on sub-10 nm technologies requires the development of the new block copolymer generation known as high- block copolymers. Additionally, an important requirement for their integration on the lithography roadmap is the capability of selectively remove one of the two blocks. The etch contrast between the two domains is typically low due to their organic chemistry. In this sense, selective sequential infiltration synthesis by ALD into one of the blocks can be used in order to incorporate an inorganic material. The formed organic/inorganic blend sustains better the plasma etching to remove the non-infiltrated organic block. In this contribution, we show the use of high- polystyrene-b-polylactide acid (PS-b-PLA) lamellar block copolymer for line/space applications. PS-b-PLA has a larger Flory-Huggins parameter (=0.218 at room temperature[4]) compared with PS-b-PMMA, allowing the size reduction of the self-assembled domains. The method to control the orientation of the polymer domains is similar to the one typically used for PS-b-PMMA. Chemical contrast and the subsequent alignment of the polymer domains are achieved by the definition of a chemical pre-pattern on a random copolymer PS-r-PMMA (48% of PS) (figure 1). The polymer brush is grafted on the substrate and then locally modified by the combination of e-beam lithography and soft oxygen plasma. Afterwards, the PS-b-PLA block copolymer is spin-coated and thermally annealed on the chemically pre-patterned substrate. A chemical contrast is observed between the modified and unmodified stripes. While, the lamellar domains are oriented perpendicular to the substrate on unmodified areas, PLA domains are strongly attracted to the O2 modified surfaces inducing a parallel orientation to the substrate. Additionally, the wetting behavior of the polymer domains is also studied through the difference of surface free energy between the substrate and each polymer block. The energy estimated by the Younǵs equation [Δγ =γSA -γSB= γAB·cos(ØAB)], where γSA and γSB are the interface tensions between homo-polymers A and B with the substrate, and ØAB is the contact angle between A and B homo-polymers which is obtained in de-wetting experiments. Finally, sequential infiltration synthesis is used to selectively infiltrate alumina (Al3O2) on PLA domains (figure 2). A selective infiltration is achieved because the precursor molecules react with the carbonyl (C=O) groups that are only present in the PLA block. After five cycles of SIS, the SIS modified PLA domains become more resistant to O2 plasma etching than PS enabling the PS etching without using other kind of hard-masks. The research leading to these results received funding from the European Union's Seventh Framework Program FP7/2007-2013, under the project CoLiSA and the European Nanoelectronics Initiative Advisory Council under the project PLACYD (ENIAC-2013-2). L. Evangelio acknowledges MECD for the PhD contract FPU13/03746 [1] R. Ruiz, H. Kang, F. A. Detcheverry, E. Dobisz, D. S. Kercher, T. R. Albrecht, J. J. de Pablo, P. F. Nealey, Science 321 (2008) 936-939. [2] M. Fernández-Regúlez, L, Evangelio, M. Lorenzoni, J. Fraxedas, F. Perez-Murano, ACS Appl. Mater. Interfaces 6 (2014) 21596-21602. [3] L. Wan, R. Ruiz, H. Gao, K. C. Patel, T. R. Albrecht, J. Yin, J. Kim, Y. Cao, G. Lin, ACS Nano 9 (2015) 7506-7514 [4] A. S. Zalusky, R. Olayo-Valles , J. H. Wolf , M. A. Hillmyer, J. Am. Chem. Soc. 124 (2002) 12761-12773

Integrated manufacturing flow for selective-etching SADP/SAQP

NASA Astrophysics Data System (ADS)

Ali, Rehab Kotb; Fatehy, Ahmed Hamed; Word, James

2018-03-01

Printing cut mask in SAMP (Self Aligned Multi Patterning) is very challenging at advanced nodes. One of the proposed solutions is to print the cut shapes selectively. Which means the design is decomposed into mandrel tracks, Mandrel cuts and non-Mandrel cuts. The mandrel and non-Mandrel cuts are mutually independent which results in relaxing spacing constrains and as a consequence more dense metal lines. In this paper, we proposed the manufacturing flow of selective etching process. The results are quantified in terms of measuring PVBand, EPE and the number of hard bridging and pinching across the layout.

Longevity of Self-etch Dentin Bonding Adhesives Compared to Etch-and-rinse Dentin Bonding Adhesives: A Systematic Review.

PubMed

Masarwa, Nader; Mohamed, Ahmed; Abou-Rabii, Iyad; Abu Zaghlan, Rawan; Steier, Liviu

2016-06-01

A systematic review and meta-analysis were performed to compare longevity of Self-Etch Dentin Bonding Adhesives to Etch-and-Rinse Dentin Bonding Adhesives. The following databases were searched for PubMed, MEDLINE, Web of Science, CINAHL, the Cochrane Library complemented by a manual search of the Journal of Adhesive Dentistry. The MESH keywords used were: "etch and rinse," "total etch," "self-etch," "dentin bonding agent," "bond durability," and "bond degradation." Included were in-vitro experimental studies performed on human dental tissues of sound tooth structure origin. The examined Self-Etch Bonds were of two subtypes; Two Steps and One Step Self-Etch Bonds, while Etch-and-Rinse Bonds were of two subtypes; Two Steps and Three Steps. The included studies measured micro tensile bond strength (μTBs) to evaluate bond strength and possible longevity of both types of dental adhesives at different times. The selected studies depended on water storage as the aging technique. Statistical analysis was performed for outcome measurements compared at 24 h, 3 months, 6 months and 12 months of water storage. After 24 hours (p-value = 0.051), 3 months (p-value = 0.756), 6 months (p-value=0.267), 12 months (p-value=0.785) of water storage self-etch adhesives showed lower μTBs when compared to the etch-and-rinse adhesives, but the comparisons were statistically insignificant. In this study, longevity of Dentin Bonds was related to the measured μTBs. Although Etch-and-Rinse bonds showed higher values at all times, the meta-analysis found no difference in longevity of the two types of bonds at the examined aging times. Copyright © 2016 Elsevier Inc. All rights reserved.

Improvement of a block co-polymer (PS-b-PDMS) template etch profile using amorphous carbon layer

NASA Astrophysics Data System (ADS)

Oh, JiSoo; Oh, Jong Sik; Sung, DaIn; Yim, SoonMin; Song, SeungWon; Yeom, GeunYoung

2017-03-01

Block copolymers (BCPs) are consisted of at least two types of monomers which have covalent bonding. One of the widely investigated BCPs is polystyrene-block-polydimethylsiloxane (PS-b-PDMS), which is used as an alternative patterning method for various deep nanoscale devices due to its high Flory-Huggins interaction parameter (χ), such as optical devices and transistors, replacing conventional photolithography. As an alternate or supplementary nextgeneration lithography technology to extreme ultraviolet lithography (EUVL), BCP lithography utilizing the DSA of BCP has been actively studied. However, the nanoscale BCP mask material is easily damaged by the plasma and has a very low etch selectivity over bottom semiconductor materials, because it is composed of polymeric materials even though it contains Si in PDMS. In this study, an amorphous carbon layer (ACL) was inserted as a hardmask material between BCP and materials to be patterned, and, by using O2 plasmas, the characteristics of dry etching of ACL for high aspect ratio (HAR) using a 10 nm PDMS pattern were investigated. The results showed that, by using a PS-b-PDMS pattern with an aspect ratio of 0.3 0.9:1, a HAR PDMS/ACL double layer mask with an aspect ratio of 10:1 could be fabricated. In addition, by the optimization of the plasma etch process, ACL masks with excellent sidewall roughness (SWR,1.35 nm) and sidewall angle (SWA, 87.9˚) could be fabricated.

Nanorods on surface of GaN-based thin-film LEDs deposited by post-annealing after photo-assisted chemical etching.

PubMed

Chen, Lung-Chien; Lin, Wun-Wei; Liu, Te-Yu

2017-12-01

This study investigates the optoelectronic characteristics of gallium nitride (GaN)-based thin-film light-emitting diodes (TF-LEDs) that are formed by a two-step transfer process that involves wet etching and post-annealing. In the two-step transfer process, GaN LEDs were stripped from sapphire substrates by the laser lift-off (LLO) method using a KrF laser and then transferred onto ceramic substrates. Ga-K nanorods were formed on the surface of the GaN-based TF-LEDs following photo-assisted chemical etching and photo-enhanced post-annealing at 100 °C for 1 min. As a result, the light output power of GaN-based TF-LEDs with wet etching and post-annealing was over 72% more than that of LEDs that did not undergo these treatments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Economou, Demetre J.

As microelectronic device features continue to shrink approaching atomic dimensions, control of the ion energy distribution on the substrate during plasma etching and deposition becomes increasingly critical. The ion energy should be high enough to drive ion-assisted etching, but not too high to cause substrate damage or loss of selectivity. In many cases, a nearly monoenergetic ion energy distribution (IED) is desired to achieve highly selective etching. In this work, the author briefly reviews: (1) the fundamentals of development of the ion energy distribution in the sheath and (2) methods to control the IED on plasma electrodes. Such methods includemore » the application of “tailored” voltage waveforms on an electrode in continuous wave plasmas, or the application of synchronous bias on a “boundary electrode” during a specified time window in the afterglow of pulsed plasmas.« less

Kinked silicon nanowires-enabled interweaving electrode configuration for lithium-ion batteries.

PubMed

Sandu, Georgiana; Coulombier, Michael; Kumar, Vishank; Kassa, Hailu G; Avram, Ionel; Ye, Ran; Stopin, Antoine; Bonifazi, Davide; Gohy, Jean-François; Leclère, Philippe; Gonze, Xavier; Pardoen, Thomas; Vlad, Alexandru; Melinte, Sorin

2018-06-28

A tri-dimensional interweaving kinked silicon nanowires (k-SiNWs) assembly, with a Ni current collector co-integrated, is evaluated as electrode configuration for lithium ion batteries. The large-scale fabrication of k-SiNWs is based on a procedure for continuous metal assisted chemical etching of Si, supported by a chemical peeling step that enables the reuse of the Si substrate. The kinks are triggered by a simple, repetitive etch-quench sequence in a HF and H 2 O 2 -based etchant. We find that the inter-locking frameworks of k-SiNWs and multi-walled carbon nanotubes exhibit beneficial mechanical properties with a foam-like behavior amplified by the kinks and a suitable porosity for a minimal electrode deformation upon Li insertion. In addition, ionic liquid electrolyte systems associated with the integrated Ni current collector repress the detrimental effects related to the Si-Li alloying reaction, enabling high cycling stability with 80% capacity retention (1695 mAh/g Si ) after 100 cycles. Areal capacities of 2.42 mAh/cm 2 (1276 mAh/g electrode ) can be achieved at the maximum evaluated thickness (corresponding to 1.3 mg Si /cm 2 ). This work emphasizes the versatility of the metal assisted chemical etching for the synthesis of advanced Si nanostructures for high performance lithium ion battery electrodes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vazehrad, S., E-mail: vazehrad@kth.se; Elfsberg, J., E-mail: jessica.elfsberg@scania.com; Diószegi, A., E-mail: attila.dioszegi@jth.hj.se

An investigation on silicon segregation of lamellar, compacted and nodular graphite iron was carried out by applying a selective, immersion color etching and a modified electron microprobe to study the microstructure. The color etched micrographs of the investigated cast irons by revealing the austenite phase have provided data about the chronology and mechanism of microstructure formation. Moreover, electron microprobe has provided two dimensional segregation maps of silicon. A good agreement was found between the segregation profile of silicon in the color etched microstructure and the silicon maps achieved by electron microprobe analysis. However, quantitative silicon investigation was found to bemore » more accurate than color etching results to study the size of the eutectic colonies. - Highlights: • Sensitivity of a color etchant to silicon segregation is quantitatively demonstrated. • Si segregation measurement by EMPA approved the results achieved by color etching. • Color etched micrographs provided data about solidification mechanism in cast irons. • Austenite grain boundaries were identified by measuring the local Si concentration.« less

Resistance of dichromated gelatin as photoresist

NASA Astrophysics Data System (ADS)

Lin, Pang; Yan, Yingbai; Jin, Guofan; Wu, Minxian

1999-09-01

Based on the photographic chemistry, chemically hardening method was selected to enhance the anti-etch capability of gelatin. With the consideration of hardener and permeating processing, formaldehyde is the most ideal option due to the smallest molecule size and covalent cross-link with gelatin. After hardened in formaldehyde, the resistance of the gelatin was obtained by etched in 1% HF solution. The result showed that anti-etch capability of the gelatin layer increased with tanning time, but the increasing rate reduced gradually and tended to saturation. Based on the experimental results, dissolving-flaking hypothesis for chemically hardening gelatin was presented. Sol-gel coatings were etched with 1% HF solution. Compared with the etching rate of gelatin layer, it showed that gelatin could be used as resist to fabricate optical elements in sol-gel coating. With the cleaving-etch method and hardening of dichromated gelatin (DCG), DCG was used as a photoresist for fabricating sol-gel optical elements. As an application, a sol-gel random phase plate was fabricated.

Molecular dynamics analysis of silicon chloride ion incidence during Si etching in Cl-based plasmas: Effects of ion incident energy, angle, and neutral radical-to-ion flux ratio

NASA Astrophysics Data System (ADS)

Nakazaki, Nobuya; Eriguchi, Koji; Ono, Kouichi

2014-10-01

Profile anomalies and surface roughness are critical issues to be resolved in plasma etching of nanometer-scale microelectronic devices, which in turn requires a better understanding of the effects of ion incident energy and angle on surface reaction kinetics. This paper presents a classical molecular dynamics (MD) simulation of Si(100) etching by energetic Clx+ (x = 1-2) and SiClx+ (x = 0-4) ion beams with different incident energies Ei = 20-500 eV and angles θi = 0-85°, with and without low-energy neutral Cl radicals (neutral-to-ion flux ratios Γn/Γi = 0 and 100). An improved Stillinger-Weber interatomic potential was used for the Si/Cl system. Numerical results indicated that in Cl+, Cl2+, SiCl3+, and SiCl4+ incidences for θi = 0° and Γn/Γi = 0, the etching occurs in the whole Ei range investigated; on the other hand, in SiCl+ and SiCl2+ incidences, the deposition occurs at low Ei < 300 and 150 eV, respectively, while the etching occurs at further increased Ei. For SiCl+ and SiCl2+, the transition energies from deposition and etching become lowered for Γn/Γi = 100. Numerical results further indicated that in the SiCl+ incidence for Γn/Γi = 0, the etching occurs in the whole θi range investigated for Ei >= 300 eV; on the other hand, for Ei = 100 and 150 eV, the deposition occurs at low θi < 60° and 40°, respectively, while the etching occurs at further increased θi; in addition, for Ei <= 50 eV, the deposition occurs in the whole θi range investigated.

Metal1 patterning study for random-logic applications with 193i, using calibrated OPC for litho and etch

NASA Astrophysics Data System (ADS)

Mailfert, Julien; Van de Kerkhove, Jeroen; De Bisschop, Peter; De Meyer, Kristin

2014-03-01

A Metal1-layer (M1) patterning study is conducted on 20nm node (N20) for random-logic applications. We quantified the printability performance on our test vehicle for N20, corresponding to Poly/M1 pitches of 90/64nm, and with a selected minimum M1 gap size of 70nm. The Metal1 layer is patterned with 193nm immersion lithography (193i) using Negative Tone Developer (NTD) resist, and a double-patterning Litho-Etch-Litho-Etch (LELE) process. Our study is based on Logic test blocks that we OPCed with a combination of calibrated models for litho and for etch. We report the Overlapping Process Window (OPW), based on a selection of test structures measured after-etch. We find that most of the OPW limiting structures are EOL (End-of-Line) configurations. Further analysis of these individual OPW limiters will reveal that they belong to different types, such as Resist 3D (R3D) and Mask 3D (M3D) sensitive structures, limiters related to OPC (Optical Proximity Corrections) options such as assist placement, or the choice of CD metrics and tolerances for calculation of the process windows itself. To guide this investigation, we will consider a `reference OPC' case to be compared with other solutions. In addition, rigorous simulations and OPC verifications will complete the after-etch measurements to help us to validate our experimental findings.

Influence of Different Etching Modes on Bond Strength to Enamel using Universal Adhesive Systems.

PubMed

Diniz, Ana Cs; Bandeca, Matheus C; Pinheiro, Larissa M; Dos Santosh Almeida, Lauber J; Torres, Carlos Rg; Borges, Alvaro H; Pinto, Shelon Cs; Tonetto, Mateus R; De Jesus Tavarez, Rudys R; Firoozmand, Leily M

2016-10-01

The adhesive systems and the techniques currently used are designed to provide a more effective adhesion with reduction of the protocol application. The objective of this study was to evaluate the bond strength of universal adhesive systems on enamel in different etching modes (self-etch and total etch). The mesial and distal halves of 52 bovine incisors, healthy, freshly extracted, were used and divided into seven experimental groups (n = 13). The enamel was treated in accordance with the following experimental conditions: FUE-Universal System - Futurabond U (VOCO) with etching; FUWE - Futurabond U (VOCO) without etching; SB-Total Etch System - Single Bond 2 (3M); SBUE-Universal System - Single Bond Universal (3M ESPE) with etching; SBUWE - Single Bond Universal (3M ESPE) without etching; CLE-Self-etch System - Clearfil SE Bond (Kuraray) was applied with etching; CLWE - Clearfil SE Bond (Kuraray) without etching. The specimens were made using the composite spectrum TPH (Dentsply) and stored in distilled water (37 ± 1°C) for 1 month. The microshear test was performed using the universal testing machine EMIC DL 2000 with the crosshead speed of 0.5 mm/minute. The bond strength values were analyzed using statistical tests (Kruskal-Wallis test and Mann-Whitney test) with Bonferroni correction. There was no statistically significant difference between groups (p < 0.05), where FUE (36.83 ± 4.9 MPa) showed the highest bond strength values and SBUWE (18.40 ± 2.2 MPa) showed the lowest bond strength values. The analysis of adhesive interface revealed that most failures occurred between the interface composite resin and adhesive. The universal adhesive system used in dental enamel varies according to the trademark, and the previous enamel etching for universal systems and the self-etch both induced greater bond strength values. Selective enamel etching prior to the application of a universal adhesive system is a relevant strategy for better performance bonding.

Bi/In thermal resist for both Si anisotropic wet etching and Si/SiO2 plasma etching

NASA Astrophysics Data System (ADS)

Chapman, Glenn H.; Tu, Yuqiang; Peng, Jun

2004-01-01

Bi/In thermal resist is a bilayer structure of Bi over In films which can be exposed by laser with a wide range of wavelengths and can be developed by diluted RCA2 solutions. Current research shows bimetallic resist can work as etch masking layer for both dry plasma etching and wet anisotropic etching. It can act as both patterning and masking layers for Si and SiO2 with plasma "dry" etch using CF4/CHF3. The etching condition is CF4 flow rate 50 sccm, pressure 150 mTorr, and RF power 100 - 600W. The profile of etched structures can be tuned by adding CHF3 and other gases such as Ar, and by changing the CF4/CHF3 ratio. Depending on the fluorocarbon plasma etching recipe the etch rate of laser exposed Bi/In can be as low as 0.1 nm/min, 500 times lower than organic photoresists. O2 plasma ashing has little etching effect on exposed Bi/In. Bi/In also creates etch masking layers for alkaline-based (KOH, TMAH and EDP) "wet" anisotropic bulk Si etch without the need of SiO2 masking steps. The laser exposed Bi/In etches two times more slowly than SiO2. Experiment result shows that single metal Indium film exhibits thermal resist characteristics but at twice the exposure levels. It can be developed in diluted RCA2 solution and used as an etch mask layer for Si anisotropic etch. X-ray diffraction analysis shows that laser exposure causes both Bi and In single film to oxidize. In film may become amorphous when exposed to high laser power.

Improving Resonance Characteristics of Gas Sensors by Chemical Etching of Quartz Plates

NASA Astrophysics Data System (ADS)

Raicheva, Z.; Georgieva, V.; Grechnikov, A.; Gadjanova, V.; Angelov, Ts; Vergov, L.; Lazarov, Y.

2012-12-01

The paper presents the results of the influence of the etching process of AT-cut quartz plates on the resonance parameters and the QCM sensors. Quartz wafers (100 μm thick, with a diameter of 8 mm), divided into five groups, have been etched in [NH4]2 F2: H2O = 1:1 solution at temperatures in the range from 70°C to 90°C. The influence of etching temperature on the surface morphology of quartz wafers has been estimated by Atomic Force Microscopy (AFM). A correlation between the etching temperature and the dynamic characteristics is obtained. The optimal etching conditions for removing the surface damages caused by the mechanical treatment of the quartz wafers and for obtaining a clean surface were determined. The typical parameters of fabricated resonators on the quartz plates etched in the temperature range from 70°C to 90°C are as follows: Frequency, Fs 16 MHz ± 100 kHz Motional resistance, Rs less 10 Ω Motional inductance, Lq higher than 3 mH Motional capacitance, Cq less 30 fF Static capacitance, Co around 5 pF Quality factor, Q from 46 000 to 70 000 Sorption properties of QCM - MoO3 are evaluated at NH3 concentrations in the interval from 100 ppm to 500 ppm.

Plasma/Neutral-Beam Etching Apparatus

NASA Technical Reports Server (NTRS)

Langer, William; Cohen, Samuel; Cuthbertson, John; Manos, Dennis; Motley, Robert

1989-01-01

Energies of neutral particles controllable. Apparatus developed to produce intense beams of reactant atoms for simulating low-Earth-orbit oxygen erosion, for studying beam-gas collisions, and for etching semiconductor substrates. Neutral beam formed by neutralization and reflection of accelerated plasma on metal plate. Plasma ejected from coaxial plasma gun toward neutralizing plate, where turned into beam of atoms or molecules and aimed at substrate to be etched.

Microdroplet-etched highly birefringent low-loss fiber tapers.

PubMed

Mikkelsen, Jared C; Poon, Joyce K S

2012-07-01

We use hydrofluoric acid microdroplets to directly etch highly birefringent biconical fiber tapers from standard single-mode fibers. The fiber tapers have micrometer-sized cross sections, which are controlled by the etching condition. The characteristic teardrop cross section leads to a high group birefringence of B(G)≈0.017 and insertion losses <0.7 dB over waist lengths of about 2.1 mm.

Clean solutions to the incoming wafer quality impact on lithography process yield limits in a dynamic copper/low-k research and development environment

NASA Astrophysics Data System (ADS)

Lysaght, Patrick S.; Ybarra, Israel; Sax, Harry; Gupta, Gaurav; West, Michael; Doros, Theodore G.; Beach, James V.; Mello, Jim

2000-06-01

The continued growth of the semiconductor manufacturing industry has been due, in large part, to improved lithographic resolution and overlay across increasingly larger chip areas. Optical lithography continues to be the mainstream technology for the industry with extensions of optical lithography being employed to support 180 nm product and process development. While the industry momentum is behind optical extensions to 130 nm, the key challenge will be maintaining an adequate and affordable process latitude (depth of focus/exposure window) necessary for 10% post-etch critical dimension (CD) control. If the full potential of optical lithography is to be exploited, the current lithographic systems can not be compromised by incoming wafer quality. Impurity specifications of novel Low-k dielectric materials, plating solutions, chemical-mechanical planarization (CMP) slurries, and chemical vapor deposition (CVD) precursors are not well understood and more stringent control measures will be required to meet defect density targets as identified in the National Technology Roadmap for Semiconductors (NTRS). This paper identifies several specific poor quality wafer issues that have been effectively addressed as a result of the introduction of a set of flexible and reliable wafer back surface clean processes developed on the SEZ Spin-Processor 203 configured for processing of 200 mm diameter wafers. Patterned wafers have been back surface etched by means of a novel spin process contamination elimination (SpCE) technique with the wafer suspended by a dynamic nitrogen (N2) flow, device side down, via the Bernoulli effect. Figure 1 illustrates the wafer-chuck orientation within the process chamber during back side etch processing. This paper addresses a number of direct and immediate benefits to the MicraScan IIITM deep-ultraviolet (DUV) step-and-scan system at SEMATECH. These enhancements have resulted from the resolution of three significant problems: (1) back surface particle/residual contamination, (2) wafer flatness, and (3) control of contaminant materials such as copper (Cu). Data associated with the SpCE process, optimized for flatness improvement, particle removal, and Cu contamination control is presented in this paper, as it relates to excessive consumption of the usable depth of focus (UDOF) and comprehensive yield enhancement in photolithography. Additionally, data illustrating a highly effective means of eliminating copper from the wafer backside, bevel/edge, and frontside edge exclusion zone (0.5 mm - 3 mm), is presented. The data, obtained within the framework of standard and experimental copper/low-k device production at SEMATECH, quantifies the benefits of implementing the SEZ SpCE clean operation. Furthermore, this data confirms the feasibility of utilizing existing (non-copper) process equipment in conjunction with the development of copper applications by verifying the reliability and cost effectiveness of SpCE functionality.

Field ionization characteristics of an ion source array for neutron generators

NASA Astrophysics Data System (ADS)

Bargsten Johnson, B.; Schwoebel, P. R.; Resnick, P. J.; Holland, C. E.; Hertz, K. L.; Chichester, D. L.

2013-11-01

A new deuterium ion source is being developed to improve the performance of existing compact neutron generators. The ion source is a microfabricated array of metal tips with an integrated gate (i.e., grid) and produces deuterium ions by field ionizing (or field desorbing) a supply of deuterium gas. Deuterium field ion currents from arrays at source temperatures of 77 K and 293 K are studied. Ion currents from single etched-wire tips operating under the same conditions are used to help understand array results. I-F characteristics of the arrays were found to follow trends similar to those of the better understood single etched-wire tip results; however, the fields achieved by the arrays are limited by electrical breakdown of the structure. Neutron production by field ionization at 293 K was demonstrated for the first time from microfabricated array structures with integrated gates.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lii-Rosales, Ann; Zhou, Yinghui; Wallingford, Mark

When using scanning tunneling microscopy, we characterize a surface carbide that forms such that Dy is deposited on the basal plane of graphite. In order to form carbide islands on terraces, Dy is first deposited at 650–800 K, which forms large metallic islands. Upon annealing at 1000 K, these clusters convert to carbide. Deposition directly at 1000 K is ineffective because nucleation on terraces is inhibited. Reaction is signaled by the fact that each carbide cluster is partially or totally surrounded by an etch pit. The etch pit is one carbon layer deep for most carbide clusters. Carbide clusters aremore » also identifiable by striations on their surfaces. Based on mass balance, and assuming that only the surface layer of carbon is involved in the reaction, the carbide has stoichiometry D y 2 C . This is Dy-rich compared with the most common bulk carbide Dy C 2 , which may reflect limited surface carbon transport to the carbide.« less

Sequential vortex hopping in an array of artificial pinning centers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keay, J. C.

2010-02-24

We use low-temperature magnetic force microscopy (MFM) to study the hopping motion of vortices in an array of artificial pinning centers (APCs). The array consists of nanoscale holes etched in a niobium thin film by Ar-ion sputtering through an anodic aluminum-oxide template. Variable-temperature magnetometry shows a transition temperature of 7.1 K and an enhancement of the magnetization up to the third matching field at 5 K. Using MFM with attractive and repulsive tip-vortex interaction, we measure the vortex-pinning strength and investigate the motion of individual vortices in the APC array. The depinning force for individual vortices at low field rangedmore » from 0.7 to 1.2 pN. The motion of individual vortices was found to be reproducible and consistent with movement between adjacent holes in the film. The movements are repeatable but the sequence of hops depends on the scan direction. This asymmetry in the motion indicates nonuniform local pinning, a consequence of array disorder and hole-size variation.« less

Design and grayscale fabrication of beamfanners in a silicon substrate

NASA Astrophysics Data System (ADS)

Ellis, Arthur Cecil

2001-11-01

This dissertation addresses important first steps in the development of a grayscale fabrication process for multiple phase diffractive optical elements (DOS's) in silicon. Specifically, this process was developed through the design, fabrication, and testing of 1-2 and 1-4 beamfanner arrays for 5-micron illumination. The 1-2 beamfanner arrays serve as a test-of- concept and basic developmental step toward the construction of the 1-4 beamfanners. The beamfanners are 50 microns wide, and have features with dimensions of between 2 and 10 microns. The Iterative Annular Spectrum Approach (IASA) method, developed by Steve Mellin of UAH, and the Boundary Element Method (BEM) are the design and testing tools used to create the beamfanner profiles and predict their performance. Fabrication of the beamfanners required the techniques of grayscale photolithography and reactive ion etching (RIE). A 2-3micron feature size 1-4 silicon beamfanner array was fabricated, but the small features and contact photolithographic techniques available prevented its construction to specifications. A second and more successful attempt was made in which both 1-4 and 1-2 beamfanner arrays were fabricated with a 5-micron minimum feature size. Photolithography for the UAH array was contracted to MEMS-Optical of Huntsville, Alabama. A repeatability study was performed, using statistical techniques, of 14 photoresist arrays and the subsequent RIE process used to etch the arrays in silicon. The variance in selectivity between the 14 processes was far greater than the variance between the individual etched features within each process. Specifically, the ratio of the variance of the selectivities averaged over each of the 14 etch processes to the variance of individual feature selectivities within the processes yielded a significance level below 0.1% by F-test, indicating that good etch-to-etch process repeatability was not attained. One of the 14 arrays had feature etch-depths close enough to design specifications for optical testing, but 5- micron IR illumination of the 1-4 and 1-2 beamfanners yielded no convincing results of beam splitting in the detector plane 340 microns from the surface of the beamfanner array.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chen; Gupta, Rahul; Pallem, Venkateswara

The authors report a systematic study aimed at evaluating the impact of molecular structure parameters of hydrofluorocarbon (HFC) precursors on plasma deposition of fluorocarbon (FC) films and etching performance of a representative ultra-low-k material, along with amorphous carbon. The precursor gases studied included fluorocarbon and hydrofluorocarbon gases whose molecular weights and chemical structures were systematically varied. Gases with three different degrees of unsaturation (DU) were examined. Trifluoromethane (CHF{sub 3}) is the only fully saturated gas that was tested. The gases with a DU value of one are 3,3,3-trifluoropropene (C{sub 3}H{sub 3}F{sub 3}), hexafluoropropene (C{sub 3}F{sub 6}), 1,1,3,3,3-pentafluoro-1-propene (C{sub 3}HF{sub 5}),more » (E)-1,2,3,3,3-pentafluoropropene (C{sub 3}HF{sub 5} isomer), heptafluoropropyl trifluorovinyl ether (C{sub 5}F{sub 10}O), octafluorocyclobutane (C{sub 4}F{sub 8}), and octafluoro-2-butene (C{sub 4}F{sub 8} isomer). The gases with a DU value of two includes hexafluoro-1,3-butadiene (C{sub 4}F{sub 6}), hexafluoro-2-butyne (C{sub 4}F{sub 6} isomer), octafluorocyclopentene (C{sub 5}F{sub 8}), and decafluorocyclohexene (C{sub 6}F{sub 10}). The work was performed in a dual frequency capacitively coupled plasma reactor. Real-time characterization of deposition and etching was performed using in situ ellipsometry, and optical emission spectroscopy was used for characterization of CF{sub 2} radicals in the gas phase. The chemical composition of the deposited FC films was examined by x-ray photoelectron spectroscopy. The authors found that the CF{sub 2} fraction, defined as the number of CF{sub 2} groups in a precursor molecule divided by the total number of carbon atoms in the molecule, determines the CF{sub 2} optical emission intensity of the plasma. CF{sub 2} optical emission, however, is not the dominant factor that determines HFC film deposition rates. Rather, HFC film deposition rates are determined by the number of weak bonds in the precursor molecule, which include a ring structure, C=C, C≡C, and C–H bonds. These bonds are broken preferentially in the plasma, and/or at the surface and fragments arriving at the substrate surface presumably provide dangling bonds that efficiently bond to the substrate or other fragments. Upon application of a radio-frequency bias to the substrate, substrate etching is induced. Highly polymerizing gases show decreased substrate etching rates as compared to HFC gases characterized by a lower HFC film deposition rate. This can be explained by a competition between deposition and etching reactions, and an increased energy and etchant dissipation in relatively thicker steady state FC films that form on the substrate surface. Deposited HFC films exhibit typically a high CF{sub 2} density at the film surface, which correlates with both the CF{sub 2} fractions in the precursor molecular structure and the deposition rate. The FC films deposited using hydrogen-containing precursors show higher degrees of crosslinking and lower F/C ratios than precursors without hydrogen, and exhibit a lower etch rate of substrate material. A small gap structure that blocks direct ion bombardment was used to simulate the sidewall plasma environment of a feature and was employed for in situ ellipsometry measurements. It is shown that highly polymerizing precursors with a DU of two enable protection of low-k sidewalls during plasma exposure from oxygen-related damage by protective film deposition. Dielectric film modifications are seen for precursors with a lower DU.« less

Simplified fast neutron dosimeter

DOEpatents

Sohrabi, Mehdi

1979-01-01

Direct fast-neutron-induced recoil and alpha particle tracks in polycarbonate films may be enlarged for direct visual observation and automated counting procedures employing electrochemical etching techniques. Electrochemical etching is, for example, carried out in a 28% KOH solution at room temperature by applying a 2000 V peak-to-peak voltage at 1 kHz frequency. Such recoil particle amplification can be used for the detection of wide neutron dose ranges from 1 mrad. to 1000 rads. or higher, if desired.

Reactive Intermediates or Inert Graphene? Temperature- and Pressure-Determined Evolution of Carbon in the CH 4–Ni(111) System

DOE PAGES

Yuan, Kaidi; Zhong, Jian-Qiang; Sun, Shuo; ...

2017-08-15

Atomic-level identification of carbon intermediates under reaction conditions is essential for carbon-related heterogeneous catalysis. Using the in operando technique of near-ambient-pressure X-ray photoelectron spectroscopy, we have identified in this paper various carbon intermediates during the thermal decomposition of CH 4 on Ni(111), including *CH, *C 1/Ni 3C, *C n (n ≥ 2), and clock-reconstructed Ni 2C at different temperature regions (300–900 K). These “reactive” carbon precursors can either react with probing molecules such as O 2 at room temperature or be etched away by CH 4. They can also develop into graphene flakes under controlled conditions: a temperature between 800more » and 900 K and a suitable CH 4 pressure (10 –3–10 –1 mbar, depending on temperature). The growth rate of graphene is significantly restrained at higher CH 4 pressures, due to the accelerated etching of its carbon precursors. The identification of in operando carbon intermediates and the control of their evolution have great potential in designing heterogeneous catalysts for the direct conversion of methane. Finally, the observed carbon aggregation/etching equilibrium reveals an underlying mechanism in coking prevention and in the fabrication of large-area single-crystal graphene, where the suppression of seeding density and etching up of small grains are required.« less

Reactive Intermediates or Inert Graphene? Temperature- and Pressure-Determined Evolution of Carbon in the CH 4–Ni(111) System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Kaidi; Zhong, Jian-Qiang; Sun, Shuo

Atomic-level identification of carbon intermediates under reaction conditions is essential for carbon-related heterogeneous catalysis. Using the in operando technique of near-ambient-pressure X-ray photoelectron spectroscopy, we have identified in this paper various carbon intermediates during the thermal decomposition of CH 4 on Ni(111), including *CH, *C 1/Ni 3C, *C n (n ≥ 2), and clock-reconstructed Ni 2C at different temperature regions (300–900 K). These “reactive” carbon precursors can either react with probing molecules such as O 2 at room temperature or be etched away by CH 4. They can also develop into graphene flakes under controlled conditions: a temperature between 800more » and 900 K and a suitable CH 4 pressure (10 –3–10 –1 mbar, depending on temperature). The growth rate of graphene is significantly restrained at higher CH 4 pressures, due to the accelerated etching of its carbon precursors. The identification of in operando carbon intermediates and the control of their evolution have great potential in designing heterogeneous catalysts for the direct conversion of methane. Finally, the observed carbon aggregation/etching equilibrium reveals an underlying mechanism in coking prevention and in the fabrication of large-area single-crystal graphene, where the suppression of seeding density and etching up of small grains are required.« less

Method of fabricating low-dislocation-density epitaxially-grown films with textured surfaces

DOEpatents

Li, Qiming; Wang, George T

2015-01-13

A method for forming a surface-textured single-crystal film layer by growing the film atop a layer of microparticles on a substrate and subsequently selectively etching away the microparticles to release the surface-textured single-crystal film layer from the substrate. This method is applicable to a very wide variety of substrates and films. In some embodiments, the film is an epitaxial film that has been grown in crystallographic alignment with respect to a crystalline substrate.

Titanium disilicide formation by sputtering of titanium on heated silicon substrate

NASA Astrophysics Data System (ADS)

Tanielian, M.; Blackstone, S.

1984-09-01

We have sputter deposited titanium on bare silicon substrates at elevated temperatures. We find that at a substrate temperature of about 515 °C titanium silicide is formed due to the reaction of the titanium with the Si. The resistivity of the silicide is about 15 μΩ cm and it is not etchable in a selective titanium etch. This process can have applications in low-temperature, metal-oxide-semiconductor self-aligned silicide formation for very large scale integrated

Localized etching of polymer films using an atmospheric pressure air microplasma jet

NASA Astrophysics Data System (ADS)

Guo, Honglei; Liu, Jingquan; Yang, Bin; Chen, Xiang; Yang, Chunsheng

2015-01-01

A direct-write process device based on the atmospheric pressure air microplasma jet (AμPJ) has been developed for the localized etching of polymer films. The plasma was generated by the air discharge ejected out through a tip-nozzle (inner diameter of 100 μm), forming the microplasma jet. The AμPJ was capable of reacting with the polymer surface since it contains a high concentration of oxygen reactive species and thus resulted in the selective removal of polymer films. The experimental results demonstrated that the AμPJ could fabricate different microstructures on a parylene-C film without using any masks or causing any heat damage. The etch rate of parylene-C reached 5.1 μm min-1 and microstructures of different depth and width could also be realized by controlling two process parameters, namely, the etching time and the distance between the nozzle and the substrate. In addition, combining XPS analysis and oxygen-induced chemical etching principles, the potential etching mechanism of parylene-C by the AμPJ was investigated. Aside from the etching of parylene-C, micro-holes on the photoresist and polyimide film were successfully created by the AμPJ. In summary, maskless pattern etching of polymer films could be achieved using this AμPJ.

Plasma-Etching of Spray-Coated Single-Walled Carbon Nanotube Films for Biointerfaces

NASA Astrophysics Data System (ADS)

Kim, Joon Hyub; Lee, Jun-Yong; Min, Nam Ki

2012-08-01

We present an effective method for the batch fabrication of miniaturized single-walled carbon nanotube (SWCNT) film electrodes using oxygen plasma etching. We adopted the approach of spray-coating for good adhesion of the SWCNT film onto a pre-patterned Pt support and used O2 plasma patterning of the coated films to realize efficient biointerfaces between SWCNT surfaces and biomolecules. By these approaches, the SWCNT film can be easily integrated into miniaturized electrode systems. To demonstrate the effectiveness of plasma-etched SWCNT film electrodes as biointerfaces, Legionella antibody was selected as analysis model owing to its considerable importance to electrochemical biosensors and was detected using plasma-etched SWCNT film electrodes and a 3,3',5,5'-tetramethyl-benzidine dihydrochloride/horseradish peroxidase (TMB/HRP) catalytic system. The response currents increased with increasing concentration of Legionella antibody. This result indicates that antibodies were effectively immobilized on plasma-etched and activated SWCNT surfaces.

Fabrication and analysis of single-crystal KTiOPO₄ films with thicknesses in the micrometer range.

PubMed

Ma, Changdong; Lu, Fei; Xu, Bo; Fan, Ranran

2016-02-01

Single-crystal potassium titanyl phosphate (KTiOPO4, KTP) films with thicknesses less than 5 μm are obtained by using helium (He) implantation combined with ion-beam-enhanced etching. A heavily damaged layer created by a 4×10(16)  cm(-2) fluence of 2 MeV He implantation is removed by means of wet chemical etching in hydrofluoric acid (HF). Thus, free-standing films of KTP with thicknesses in the range of 3-5 μm are obtained. The etching rate can be adjusted over a wide range by choosing temperature and HF concentration, as well as annealing conditions. Sharp etching edges and the smooth surface of the film indicate that a high selective-etching rate is achieved in the damaged layer, and the remaining part of the crystal is undamaged. X-ray and Raman-scattering results prove that KTP films have good single-crystal properties.

Ion-Exchange-Induced Selective Etching for the Synthesis of Amino-Functionalized Hollow Mesoporous Silica for Elevated-High-Temperature Fuel Cells.

PubMed

Zhang, Jin; Liu, Jian; Lu, Shanfu; Zhu, Haijin; Aili, David; De Marco, Roland; Xiang, Yan; Forsyth, Maria; Li, Qingfeng; Jiang, San Ping

2017-09-20

As differentiated from conventional synthetic processes, amino-functionalized hollow mesoporous silica (NH 2 -HMS) has been synthesized using a new and facile strategy of ion-exchange-induced selective etching of amino-functionalized mesoporous silica (NH 2 -meso-silica) by an alkaline solution. Nuclear magnetic resonance (NMR) spectroscopy and in situ time-resolved small-angle X-ray scattering (SAXS) reveal that ion-exchange-induced selective etching arises from the gradient distribution of OH - in the NH 2 -meso-silica nanospheres. Moreover, the ion-exchange-induced selective etching mechanism is verified through a successful synthesis of hollow mesoporous silica. After infiltration with phosphotungstic acid (PWA), PWA-NH 2 -HMS nanoparticles are dispersed in the poly(ether sulfone)-polyvinylpyrrolidone (PES-PVP) matrix, forming a hybrid PWA-NH 2 -HMS/PES-PVP nanocomposite membrane. The resultant nanocomposite membrane with an optimum loading of 10 wt % of PWA-NH 2 -HMS showed an enhanced proton conductivity of 0.175 S cm -1 and peak power density of 420 mW cm -2 at 180 °C under anhydrous conditions. Excellent durability of the hybrid composite membrane fuel cell has been demonstrated at 200 °C. The results of this study demonstrated the potential of the facile synthetic strategy in the fabrication of NH 2 -HMS with controlled mesoporous structure for application in nanocomposite membranes as a technology platform for elevated-temperature proton exchange membrane fuel cells.

METHOD OF APPLYING NICKEL COATINGS ON URANIUM

DOEpatents

Gray, A.G.

1959-07-14

A method is presented for protectively coating uranium which comprises etching the uranium in an aqueous etching solution containing chloride ions, electroplating a coating of nickel on the etched uranium and heating the nickel plated uranium by immersion thereof in a molten bath composed of a material selected from the group consisting of sodium chloride, potassium chloride, lithium chloride, and mixtures thereof, maintained at a temperature of between 700 and 800 deg C, for a time sufficient to alloy the nickel and uranium and form an integral protective coating of corrosion-resistant uranium-nickel alloy.

Molecular transport through nanoporous silicon nitride membranes produced from self-assembling block copolymers.

PubMed

Montagne, Franck; Blondiaux, Nicolas; Bojko, Alexandre; Pugin, Raphaël

2012-09-28

To achieve fast and selective molecular filtration, membrane materials must ideally exhibit a thin porous skin and a high density of pores with a narrow size distribution. Here, we report the fabrication of nanoporous silicon nitride membranes (NSiMs) at the full wafer scale using a versatile process combining block copolymer (BCP) self-assembly and conventional photolithography/etching techniques. In our method, self-assembled BCP micelles are used as templates for creating sub-100 nm nanopores in a thin low-stress silicon nitride layer, which is then released from the underlying silicon wafer by etching. The process yields 100 nm thick free-standing NSiMs of various lateral dimensions (up to a few mm(2)). We show that the membranes exhibit a high pore density, while still retaining excellent mechanical strength. Permeation experiments reveal that the molecular transport rate across NSiMs is up to 16-fold faster than that of commercial polymeric membranes. Moreover, using dextran molecules of various molecular weights, we also demonstrate that size-based separation can be achieved with a very good selectivity. These new silicon nanosieves offer a relevant technological alternative to commercially available ultra- and microfiltration membranes for conducting high resolution biomolecular separations at small scales.

Carbon Nanotube Spaceframes for Low-Density Aerospace Materials

DTIC Science & Technology

2012-01-26

different types of oxidative etching chemistries have been reported in the literature, with acidic conditions such as nitric acid etching and piranha...and reduce the production of adhered fulvic acid species.1 A range of RCA type different etching conditions were investigated involving different...carboxylic and hydroxyl type sites together by first using a dicarboxylic acid (preferably in a highly reactive form such as oxalic chloride or succinic

Laser-etch patterning of metal oxide coated carbon nanotube 3D architectures.

PubMed

Aksu, Cemile; Ingram, Wade; Bradford, Philip D; Jur, Jesse S

2018-08-17

This paper describes a way to fabricate novel hybrid low density nanostructures containing both carbon nanotubes (CNTs) and ceramic nanotubes. Using atomic layer deposition, a thin film of aluminum oxide was conformally deposited on aligned multiwall CNT foams in which the CNTs make porous, three-dimensional interconnected networks. A CO 2 laser was used to etch pure alumina nanotube structures by burning out the underlying CNT substrate in discrete locations via the printed laser pattern. Structural and morphological transitions during the calcination process of aluminum oxide coated CNTs were investigated through in situ transmission electron microscopy and high-resolution scanning electron microscopy. Laser parameters were optimized to etch the CNT away (i.e. etching speed, power and focal length) while minimizing damage to the alumina nanotubes due to overheating. This study opens a new route for fabricating very low density three dimensionally patterned materials with areas of dissimilar materials and properties. To demonstrate the attributes of these structures, the etched areas were used toward anisotropic microfluidic liquid flow. The demonstration used the full thickness of the material to make complex pathways for the liquid flow in the structure. Through tuning of processing conditions, the alumina nanotube (etched) regions became hydrophilic while the bulk material remained hydrophobic and electrically conductive.

Etching twin core fiber for the temperature-independent refractive index sensing

NASA Astrophysics Data System (ADS)

Zhang, Chuanbiao; Ning, Tigang; Li, Jing; Zheng, Jingjing; Gao, Xuekai; Lin, Heng; Pei, Li

2018-04-01

We proposed an ultra-compact chemically etched twin core fiber (TCF) based optic refractive index (RI) sensor, in which the etched fiber was fabricated by immersing in an aqueous solution of hydrofluoric acid (HF) to etch the cladding. Due to the multipath evolutions of light during the TCF, the mode induced interference pattern can be used for measurement. Numerical simulations were performed, demonstrating that only the cladding mode strongly interacts with the surrounding media, and the higher cladding modes will be more sensitive to external medium. In the experiment demonstration, the RI response characteristics of the sensor were investigated, which shows a relatively high RI sensitivity and a much low temperature cross-sensitivity with about 1.06 × 10-6 RIU °C-1. Due to low cost and easy fabrication, the sensor can be a suitable candidate in the biochemical field.

Fabrication and etching processes of silicon-based PZT thin films

NASA Astrophysics Data System (ADS)

Zhao, Hongjin; Liu, Yanxiang; Liu, Jianshe; Ren, Tian-Ling; Liu, Li-Tian; Li, Zhijian

2001-09-01

Lead-zirconate-titanate (PZT) thin films on silicon were prepared by a sol-gel method. Phase characterization and crystal orientation of the films were investigated by x-ray diffraction analysis (XRD). It was shown that the PZT thin films had a perfect perovskite structure after annealed at a low temperature of 600 degrees C. PZT thin films were chemically etched using HCl/HF solution through typical semiconductor lithographic process, and the etching condition was optimized. The scanning electron microscopy results indicated that the PZT thin film etching problem was well solved for the applications of PZT thin film devices.

Nanoscale silver-assisted wet etching of crystalline silicon for anti-reflection surface textures.

PubMed

Li, Rui; Wang, Shuling; Chuwongin, Santhad; Zhou, Weidong

2013-01-01

We report here an electro-less metal-assisted chemical etching (MacEtch) process as light management surface-texturing technique for single crystalline Si photovoltaics. Random Silver nanostructures were formed on top of the Si surface based on the thin film evaporation and annealing process. Significant reflection reduction was obtained from the fabricated Si sample, with approximately 2% reflection over a wide spectra range (300 to 1050 nm). The work demonstrates the potential of MacEtch process for anti-reflection surface texture fabrication of large area, high efficiency, and low cost thin film solar cell.

Metal-assisted chemical etching using sputtered gold: a simple route to black silicon

NASA Astrophysics Data System (ADS)

Kurek, Agnieszka; Barry, Seán T.

2011-08-01

We report an accessible and simple method of producing 'black silicon' with aspect ratios as high as 8 using common laboratory equipment. Gold was sputtered to a thickness of 8 nm using a low-vacuum sputter coater. The structures were etched into silicon substrates using an aqueous H2O2/HF solution, and the gold was then removed using aqua regia. Ultrasonication was necessary to produce columnar structures, and an etch time of 24 min gave a velvety, non-reflective surface. The surface features after 24 min etching were uniformly microstructured over an area of square centimetres.

What's new in dentine bonding? Self-etch adhesives.

PubMed

Burke, F J Trevor

2004-12-01

Bonding to dentine is an integral part of contemporary restorative dentistry, but early systems were not user-friendly. The introduction of new systems which have a reduced number of steps--the self-etch adhesives--could therefore be an advantage to clinicians, provided that they are as effective as previous adhesives. These new self-etch materials appear to form hybrid layers as did the previous generation of materials. However, there is a need for further clinical research on these new materials. Advantages of self-etch systems include, no need to etch and rinse, reduced post-operative sensitivity and low technique sensitivity. Disadvantages include, the inhibition of set of self- or dual-cure resin materials and the need to roughen untreated enamel surfaces prior to bonding.

Nanoporous polymeric nanofibers based on selectively etched PS-b-PDMS block copolymers.

PubMed

Demirel, Gokcen B; Buyukserin, Fatih; Morris, Michael A; Demirel, Gokhan

2012-01-01

One-dimensional nanoporous polymeric nanofibers have been fabricated within an anodic aluminum oxide (AAO) membrane by a facile approach based on selective etching of poly(dimethylsiloxane) (PDMS) domains in polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) block copolymers that had been formed within the AAO template. It was observed that prior to etching, the well-ordered PS-b-PDMS nanofibers are solid and do not have any porosity. The postetched PS nanofibers, on the other hand, had a highly porous structure having about 20-50 nm pore size. The nanoporous polymeric fibers were also employed as a drug carrier for the native, continuous, and pulsatile drug release using Rhodamine B (RB) as a model drug. These studies showed that enhanced drug release and tunable drug dosage can be achieved by using ultrasound irradiation. © 2011 American Chemical Society

Selective etchant for oxide sacrificial material in semiconductor device fabrication

DOEpatents

Clews, Peggy J.; Mani, Seethambal S.

2005-05-17

An etching composition and method is disclosed for removing an oxide sacrificial material during manufacture of semiconductor devices including micromechanical, microelectromechanical or microfluidic devices. The etching composition and method are based on the combination of hydrofluoric acid (HF) and sulfuric acid (H.sub.2 SO.sub.4). These acids can be used in the ratio of 1:3 to 3:1 HF:H.sub.2 SO.sub.4 to remove all or part of the oxide sacrificial material while providing a high etch selectivity for non-oxide materials including polysilicon, silicon nitride and metals comprising aluminum. Both the HF and H.sub.2 SO.sub.4 can be provided as "semiconductor grade" acids in concentrations of generally 40-50% by weight HF, and at least 90% by weight H.sub.2 SO.sub.4.

Impact of substrate etching on plasmonic elements and metamaterials: preventing red shift and improving refractive index sensitivity.

PubMed

Moritake, Yuto; Tanaka, Takuo

2018-02-05

We propose and demonstrate the elimination of substrate influence on plasmon resonance by using selective and isotropic etching of substrates. Preventing the red shift of the resonance due to substrates and improving refractive index sensitivity were experimentally demonstrated by using plasmonic nanostructures fabricated on silicon substrates. Applying substrate etching decreases the effective refractive index around the metal nanostructures, resulting in elimination of the red shift. Improvement of sensitivity to the refractive index environment was demonstrated by using plasmonic metamaterials with Fano resonance based on far field interference. Change in quality factors (Q-factors) of the Fano resonance by substrate etching was also investigated in detail. The presence of a closely positioned substrate distorts the electric field distribution and degrades the Q-factors. Substrate etching dramatically increased the refractive index sensitivity reaching to 1532 nm/RIU since the electric fields under the nanostructures became accessible through substrate etching. The FOM was improved compared to the case without the substrate etching. The method presented in this paper is applicable to a variety of plasmonic structures to eliminate the influence of substrates for realizing high performance plasmonic devices.

Vapor etching of nuclear tracks in dielectric materials

DOEpatents

Musket, Ronald G.; Porter, John D.; Yoshiyama, James M.; Contolini, Robert J.

2000-01-01

A process involving vapor etching of nuclear tracks in dielectric materials for creating high aspect ratio (i.e., length much greater than diameter), isolated cylindrical holes in dielectric materials that have been exposed to high-energy atomic particles. The process includes cleaning the surface of the tracked material and exposing the cleaned surface to a vapor of a suitable etchant. Independent control of the temperatures of the vapor and the tracked materials provide the means to vary separately the etch rates for the latent track region and the non-tracked material. As a rule, the tracked regions etch at a greater rate than the non-tracked regions. In addition, the vapor-etched holes can be enlarged and smoothed by subsequent dipping in a liquid etchant. The 20-1000 nm diameter holes resulting from the vapor etching process can be useful as molds for electroplating nanometer-sized filaments, etching gate cavities for deposition of nano-cones, developing high-aspect ratio holes in trackable resists, and as filters for a variety of molecular-sized particles in virtually any liquid or gas by selecting the dielectric material that is compatible with the liquid or gas of interest.

Microscale electrokinetic transport and stability

NASA Astrophysics Data System (ADS)

Chen, Chuan-Hua

Electrokinetics is a leading mechanism for transport and separation of biochemical samples in microdevices due to its favorable scaling at small scales. However, electrokinetic systems can become highly unstable, and this instability adversely affects key processes such as sample stacking and electrophoretic separation. This dissertation deals with two major topics: a novel planar micropump exploiting the favorable scaling of electroosmosis at the microscale, and a fundamental study of electrokinetic flow instabilities induced by electrical conductivity gradients. Electroosmotic micropumps use field-induced ion drag to drive liquids and achieve high pressures in a compact design with no moving parts. An analytical model applicable to planar, etched-structure micropumps was developed to guide the geometrical design and working fluid selection. Standard microlithography and wet etching techniques were used to fabricate a pump 1 mm long along the flow direction and 0.9 mum by 38 mm in cross section. The pump produced a maximum pressure of 0.33 atm and a maximum flow rate of 15 mul/min at 1 kV applied potential with deionized water as working fluid. The pump performance agreed well with the theoretical model. Electrokinetic flow instabilities occur under high electric field in the presence of electrical conductivity gradients. In a microfluidic T-junction 11 mum by 155 mum in cross section, aqueous electrolytes of 10:1 conductivity ratio were electrokinetically driven into a common mixing channel. Convectively unstable waves were observed at 0.5 kV/cm, and upstream propagating waves at 1.5 kV/cm. A physical model for this instability has been developed. A linear stability analysis of the governing equations in the thin-layer limit predicts both qualitative trends and quantitative features that agree well with experimental data. Briggs-Bers criteria were applied to select physically unstable modes and determine the nature of instability. Conductivity gradients and bulk charge accumulation are a crucial factor in the instability. The role of electroosmotic flow is mainly as a convecting medium. The instability is governed by two key controlling parameters: the ratio of dynamic to dissipative forces which determines the onset of instability, and the ratio of electroviscous to electroosmotic velocities which governs the convective versus absolute nature of instability.

Surface Treatment of Plastic Substrates using Atomic Hydrogen Generated on Heated Tungsten Wire at Low Temperatures

NASA Astrophysics Data System (ADS)

Heya, Akira; Matsuo, Naoto

2007-06-01

The surface properties of a plastic substrate were changed by a novel surface treatment called atomic hydrogen annealing (AHA). In this method, a plastic substrate was exposed to atomic hydrogen generated by cracking hydrogen molecules on heated tungsten wire. For the substrate, surface roughness was increased and halogen elements (F and Cl) were selectively etched by AHA. AHA was useful for pretreatment before film deposition on a plastic substrate because the changes in surface state relate to adhesion improvement. It is concluded that this method is a promising technique for preparing high-performance plastic substrates at low temperatures.

Sodium and potassium competition in potassium-selective and non-selective channels

NASA Astrophysics Data System (ADS)

Sauer, David B.; Zeng, Weizhong; Canty, John; Lam, Yeeling; Jiang, Youxing

2013-11-01

Potassium channels selectively conduct K+, primarily to the exclusion of Na+, despite the fact that both ions can bind within the selectivity filter. Here we perform crystallographic titration and single-channel electrophysiology to examine the competition of Na+ and K+ binding within the filter of two NaK channel mutants; one is the potassium-selective NaK2K mutant and the other is the non-selective NaK2CNG, a CNG channel pore mimic. With high-resolution structures of these engineered NaK channel constructs, we explicitly describe the changes in K+ occupancy within the filter upon Na+ competition by anomalous diffraction. Our results demonstrate that the non-selective NaK2CNG still retains a K+-selective site at equilibrium, whereas the NaK2K channel filter maintains two high-affinity K+ sites. A double-barrier mechanism is proposed to explain K+ channel selectivity at low K+ concentrations.

Novel Heterongineered Detectors for Multi-Color Infrared Sensing

DTIC Science & Technology

2012-01-30

barriers”. Appl. Phys. Lett. 98, 121106 (2011) 9. A. Khoshakhlagh, F. Jaeckel C. Hains J. B. Rodriguez , L. R. Dawson, K. Malloy, and S. Krishna...AlAs etch-stop layer. The detailed processing sequence is included in the Methods. b da c n + -GaAs 200 nm Mesa lndium bump 2.1 –2.1 FPA p d SP-FPA...FPA chip. The processing scheme of the plasmonic FPA chip consists of a dry etch to form the mesa , surface passivation, ohmic metal evaporation, under

Inductive plasmas for plasma processing

NASA Astrophysics Data System (ADS)

Keller, John H.

1996-05-01

With the need for high plasma density and low pressure in single wafer etching tools, a number of inductive etching systems have been and are being developed for commercial sale. This paper reviews some of the history of low-pressure inductive plasmas, gives features of inductive plasmas, limitations, corrections and presents uses for plasma processing. The theory for the skin depth, rf coil impedance and efficiency is also discussed.

High index glass thin film processing for photonics and photovoltaic (PV) applications

NASA Astrophysics Data System (ADS)

Ogbuu, Okechukwu Anthony

To favorably compete with fossil-fuel technology, the greatest challenge for thin film solar-cells is to improve efficiency and reduce material cost. Thickness scaling to thin film reduces material cost but affects the light absorption in the cells; therefore a concept that traps incident photons and increases its optical path length is needed to boost absorption in thin film solar cells. One approach is the integration of low symmetric gratings (LSG), using high index material, on either the front-side or backside of 30 um thin c-Si cells. In this study, Multicomponent TeO2--Bi2O 3--ZnO (TBZ) glass thin films were prepared using RF magnetron sputtering under different oxygen flow rates. The influences of oxygen flow rate on the structural and optical properties of the resulting thin films were investigated. The structural origin of the optical property variation was studied using X-ray diffraction, X-ray photoelectron spectroscopy, Raman Spectroscopy, and transmission electron microscopy. The results indicate that TBZ glass thin film is a suitable material for front side LSG material photovoltaic and photonics applications due to their amorphous nature, high refractive index (n > 2), broad band optical transparency window, low processing temperature. We developed a simple maskless method to pattern sputtered tellurite based glass thin films using unconventional agarose hydrogel mediated wet etching. Conventional wet etching process, while claiming low cost and high throughput, suffers from reproducibility and pattern fidelity issues due to the isotropic nature of wet chemical etching when applied to glasses and polymers. This method overcomes these challenges by using an agarose hydrogel stamp to mediate a conformal etching process. In our maskless method, agarose hydrogel stamps are patterned following a standard soft lithography and replica molding process from micropatterned masters and soaked in a chemical etchant. The micro-scale features on the stamp are subsequently transferred into glass and polymer thin films via conformal wet etching. High refractive index chalcogenide glass (n = 2.6) thin films with composition As20Se80 was selected for backside LSG material due to their attractive properties. We developed an optimized integration protocol for LSG integration and successfully integrated these LSG structures at the back side of both 30 microm c-Si solar cells and standalone 30 microm c-Si wafers. Optical and electrical characterization of LSG on thin c-Si cells shows that LSG structures create higher absorption enhancement and external quantum efficiency at long wavelengths.

Cross-plane electronic and thermal transport properties of p-type La0.67Sr0.33MnO3/LaMnO3 perovskite oxide metal/semiconductor superlattices

NASA Astrophysics Data System (ADS)

Jha, Pankaj; Sands, Timothy D.; Cassels, Laura; Jackson, Philip; Favaloro, Tela; Kirk, Benjamin; Zide, Joshua; Xu, Xianfan; Shakouri, Ali

2012-09-01

Lanthanum strontium manganate (La0.67Sr0.33MnO3, i.e., LSMO)/lanthanum manganate (LaMnO3, i.e., LMO) perovskite oxide metal/semiconductor superlattices were investigated as a potential p-type thermoelectric material. Growth was performed using pulsed laser deposition to achieve epitaxial LSMO (metal)/LMO (p-type semiconductor) superlattices on (100)-strontium titanate (STO) substrates. The magnitude of the in-plane Seebeck coefficient of LSMO thin films (<20 μV/K) is consistent with metallic behavior, while LMO thin films were p-type with a room temperature Seebeck coefficient of 140 μV/K. Thermal conductivity measurements via the photo-acoustic (PA) technique showed that LSMO/LMO superlattices exhibit a room temperature cross-plane thermal conductivity (0.89 W/m.K) that is significantly lower than the thermal conductivity of individual thin films of either LSMO (1.60 W/m.K) or LMO (1.29 W/m.K). The lower thermal conductivity of LSMO/LMO superlattices may help overcome one of the major limitations of oxides as thermoelectrics. In addition to a low cross-plane thermal conductivity, a high ZT requires a high power factor (S2σ). Cross-plane electrical transport measurements were carried out on cylindrical pillars etched in LSMO/LMO superlattices via inductively coupled plasma reactive ion etching. Cross-plane electrical resistivity data for LSMO/LMO superlattices showed a magnetic phase transition temperature (TP) or metal-semiconductor transition at ˜330 K, which is ˜80 K higher than the TP observed for in-plane resistivity of LSMO, LMO, or LSMO/LMO thin films. The room temperature cross-plane resistivity (ρc) was found to be greater than the in-plane resistivity by about three orders of magnitude. The magnitude and temperature dependence of the cross-plane conductivity of LSMO/LMO superlattices suggests the presence of a barrier with the effective barrier height of ˜300 meV. Although the magnitude of the cross-plane power factor is too low for thermoelectric applications by a factor of approximately 10-4—in part because the growth conditions chosen for this study yielded relatively high resistivity films—the temperature dependence of the resistivity and the potential for tuning the power factor by engineering strain, oxygen stoichiometry, and electronic band structure suggest that these epitaxial metal/semiconductor superlattices are deserving of further investigation.

Enhanced etching of tin-doped indium oxide due to surface modification by hydrogen ion injection

NASA Astrophysics Data System (ADS)

Li, Hu; Karahashi, Kazuhiro; Friederich, Pascal; Fink, Karin; Fukasawa, Masanaga; Hirata, Akiko; Nagahata, Kazunori; Tatsumi, Tetsuya; Wenzel, Wolfgang; Hamaguchi, Satoshi

2018-06-01

It is known that the etching yield (i.e., sputtering yield) of tin-doped indium oxide (ITO) by hydrocarbon ions (CH x +) is higher than its corresponding physical sputtering yield [H. Li et al., J. Vac. Sci. Technol. A 33, 060606 (2015)]. In this study, the effects of hydrogen in the incident hydrocarbon ion beam on the etching yield of ITO have been examined experimentally and theoretically with the use of a mass-selected ion beam system and by first-principles quantum mechanical (QM) simulation. As in the case of ZnO [H. Li et al., J. Vac. Sci. Technol. A 35, 05C303 (2017)], mass-selected ion beam experiments have shown that the physical sputtering yield of ITO by chemically inert Ne ions increases after a pretreatment of the ITO film by energetic hydrogen ion injection. First-principles QM simulation of the interaction of In2O3 with hydrogen atoms shows that hydrogen atoms embedded in In2O3 readily form hydroxyl (OH) groups and weaken or break In–O bonds around the hydrogen atoms, making the In2O3 film less resistant to physical sputtering. This is consistent with experimental observation of the enhanced etching yields of ITO by CH x + ions, considering the fact that hydrogen atoms of the incident CH x + ions are embedded into ITO during the etching process.

Suppression of Lateral Diffusion and Surface Leakage Currents in nBn Photodetectors Using an Inverted Design

NASA Astrophysics Data System (ADS)

Du, X.; Savich, G. R.; Marozas, B. T.; Wicks, G. W.

2018-02-01

Surface leakage and lateral diffusion currents in InAs-based nBn photodetectors have been investigated. Devices fabricated using a shallow etch processing scheme that etches through the top contact and stops at the barrier exhibited large lateral diffusion current but undetectably low surface leakage. Such large lateral diffusion current significantly increased the dark current, especially in small devices, and causes pixel-to-pixel crosstalk in detector arrays. To eliminate the lateral diffusion current, two different approaches were examined. The conventional solution utilized a deep etch process, which etches through the top contact, barrier, and absorber. This deep etch processing scheme eliminated lateral diffusion, but introduced high surface current along the device mesa sidewalls, increasing the dark current. High device failure rate was also observed in deep-etched nBn structures. An alternative approach to limit lateral diffusion used an inverted nBn structure that has its absorber grown above the barrier. Like the shallow etch process on conventional nBn structures, the inverted nBn devices were fabricated with a processing scheme that only etches the top layer (the absorber, in this case) but avoids etching through the barrier. The results show that inverted nBn devices have the advantage of eliminating the lateral diffusion current without introducing elevated surface current.

GaN nanowire arrays with nonpolar sidewalls for vertically integrated field-effect transistors

NASA Astrophysics Data System (ADS)

Yu, Feng; Yao, Shengbo; Römer, Friedhard; Witzigmann, Bernd; Schimpke, Tilman; Strassburg, Martin; Bakin, Andrey; Schumacher, Hans Werner; Peiner, Erwin; Suryo Wasisto, Hutomo; Waag, Andreas

2017-03-01

Vertically aligned gallium nitride (GaN) nanowire (NW) arrays have attracted a lot of attention because of their potential for novel devices in the fields of optoelectronics and nanoelectronics. In this work, GaN NW arrays have been designed and fabricated by combining suitable nanomachining processes including dry and wet etching. After inductively coupled plasma dry reactive ion etching, the GaN NWs are subsequently treated in wet chemical etching using AZ400K developer (i.e., with an activation energy of 0.69 ± 0.02 eV and a Cr mask) to form hexagonal and smooth a-plane sidewalls. Etching experiments using potassium hydroxide (KOH) water solution reveal that the sidewall orientation preference depends on etchant concentration. A model concerning surface bonding configuration on crystallography facets has been proposed to understand the anisotropic wet etching mechanism. Finally, NW array-based vertical field-effect transistors with wrap-gated structure have been fabricated. A device composed of 99 NWs exhibits enhancement mode operation with a threshold voltage of 1.5 V, a superior electrostatic control, and a high current output of >10 mA, which prevail potential applications in next-generation power switches and high-temperature digital circuits.

GaN nanowire arrays with nonpolar sidewalls for vertically integrated field-effect transistors.

PubMed

Yu, Feng; Yao, Shengbo; Römer, Friedhard; Witzigmann, Bernd; Schimpke, Tilman; Strassburg, Martin; Bakin, Andrey; Schumacher, Hans Werner; Peiner, Erwin; Wasisto, Hutomo Suryo; Waag, Andreas

2017-03-03

Vertically aligned gallium nitride (GaN) nanowire (NW) arrays have attracted a lot of attention because of their potential for novel devices in the fields of optoelectronics and nanoelectronics. In this work, GaN NW arrays have been designed and fabricated by combining suitable nanomachining processes including dry and wet etching. After inductively coupled plasma dry reactive ion etching, the GaN NWs are subsequently treated in wet chemical etching using AZ400K developer (i.e., with an activation energy of 0.69 ± 0.02 eV and a Cr mask) to form hexagonal and smooth a-plane sidewalls. Etching experiments using potassium hydroxide (KOH) water solution reveal that the sidewall orientation preference depends on etchant concentration. A model concerning surface bonding configuration on crystallography facets has been proposed to understand the anisotropic wet etching mechanism. Finally, NW array-based vertical field-effect transistors with wrap-gated structure have been fabricated. A device composed of 99 NWs exhibits enhancement mode operation with a threshold voltage of 1.5 V, a superior electrostatic control, and a high current output of >10 mA, which prevail potential applications in next-generation power switches and high-temperature digital circuits.

Metal-assisted electroless fabrication of nanoporous p-GaN for increasing the light extraction efficiency of light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Ruijun; Liu Duo; Zuo Zhiyuan

2012-03-15

We report metal-assisted electroless fabrication of nanoporous p-GaN to improve the light extraction efficiency of GaN-based light emitting diodes (LEDs). Although it has long been believed that p-GaN cannot be etched at room temperature, in this study we find that Ag nanocrystals (NCs) on the p-GaN surface enable effective etching of p-GaN in a mixture of HF and K{sub 2}S{sub 2}O{sub 8} under ultraviolet (UV) irradiation. It is further shown that the roughened GaN/air interface enables strong scattering of photons emitted from the multiple quantum wells (MQWs). The light output power measurements indicate that the nanoporous LEDs obtained after 10more » min etching show a 32.7% enhancement in light-output relative to the conventional LEDs at an injection current of 20 mA without significant increase of the operating voltage. In contrast, the samples etched for 20 min show performance degradation when compared with those etched for 10 min, this is attributed to the current crowding effect and increased surface recombination rate.« less

Extreme wettability of nanostructured glass fabricated by non-lithographic, anisotropic etching

PubMed Central

Yu, Eusun; Kim, Seul-Cham; Lee, Heon Ju; Oh, Kyu Hwan; Moon, Myoung-Woon

2015-01-01

Functional glass surfaces with the properties of superhydrophobicity/or superhydrohydrophilicity, anti-condensation or low reflectance require nano- or micro-scale roughness, which is difficult to fabricate directly on glass surfaces. Here, we report a novel non-lithographic method for the fabrication of nanostructures on glass; this method introduces a sacrificial SiO2 layer for anisotropic plasma etching. The first step was to form nanopillars on SiO2 layer-coated glass by using preferential CF4 plasma etching. With continuous plasma etching, the SiO2 pillars become etch-resistant masks on the glass; thus, the glass regions covered by the SiO2 pillars are etched slowly, and the regions with no SiO2 pillars are etched rapidly, resulting in nanopatterned glass. The glass surface that is etched with CF4 plasma becomes superhydrophilic because of its high surface energy, as well as its nano-scale roughness and high aspect ratio. Upon applying a subsequent hydrophobic coating to the nanostructured glass, a superhydrophobic surface was achieved. The light transmission of the glass was relatively unaffected by the nanostructures, whereas the reflectance was significantly reduced by the increase in nanopattern roughness on the glass. PMID:25791414

The effect of reactive ion etch (RIE) process conditions on ReRAM device performance

NASA Astrophysics Data System (ADS)

Beckmann, K.; Holt, J.; Olin-Ammentorp, W.; Alamgir, Z.; Van Nostrand, J.; Cady, N. C.

2017-09-01

The recent surge of research on resistive random access memory (ReRAM) devices has resulted in a wealth of different materials and fabrication approaches. In this work, we describe the performance implications of utilizing a reactive ion etch (RIE) based process to fabricate HfO2 based ReRAM devices, versus a more unconventional shadow mask fabrication approach. The work is the result of an effort to increase device yield and reduce individual device size. Our results show that choice of RIE etch gas (SF6 versus CF4) is critical for defining the post-etch device profile (cross-section), and for tuning the removal of metal layers used as bottom electrodes in the ReRAM device stack. We have shown that etch conditions leading to a tapered profile for the device stack cause poor electrical performance, likely due to metal re-deposition during etching, and damage to the switching layer. These devices exhibit nonlinear I-V during the low resistive state, but this could be improved to linear behavior once a near-vertical etch profile was achieved. Device stacks with vertical etch profiles also showed an increase in forming voltage, reduced switching variability and increased endurance.

Method of making an ion beam sputter-etched ventricular catheter for hydrocephalus shunt

NASA Technical Reports Server (NTRS)

Banks, B. A. (Inventor)

1984-01-01

The centricular catheter comprises a multiplicity of inlet microtubules. Each microtubule has both a large opening at its inlet end and a multiplicity of microscopic openings along its lateral surfaces. The microtubules are perforated by an ion beam sputter etch technique. The holes are etched in each microtubule by directing an ion beam through an electro formed mesh mask producing perforations having diameters ranging from about 14 microns to about 150 microns. This structure assures a reliable means for shunting cerebrospinal fluid from the cerebral ventricles to selected areas of the body.

Circulating tumor cell isolation: the assets of filtration methods with polycarbonate track-etched filters

PubMed Central

Dolfus, Claire; Piton, Nicolas; Toure, Emmanuel

2015-01-01

Circulating tumor cells (CTCs) arise from primary or secondary tumors and enter the bloodstream by active or passive intravasation. Given the low number of CTCs, enrichment is necessary for detection. Filtration methods are based on selection of CTCs by size using a filter with 6.5 to 8 µm pores. After coloration, collected CTCs are evaluated according to morphological criteria. Immunophenotyping and fluorescence in situ hybridization techniques may be used. Selected CTCs can also be cultivated in vitro to provide more material. Analysis of genomic mutations is difficult because it requires adapted techniques due to limited DNA materials. Filtration-selected CTCs have shown prognostic value in many studies but multicentric validating trials are mandatory to strengthen this assessment. Other clinical applications are promising such as follow-up, therapy response prediction and diagnosis. Microfluidic emerging systems could optimize filtration-selected CTCs by increasing selection accuracy. PMID:26543334

GaN MOSFET with Boron Trichloride-Based Dry Recess Process

NASA Astrophysics Data System (ADS)

Jiang, Y.; Wang, Q. P.; Tamai, K.; Miyashita, T.; Motoyama, S.; Wang, D. J.; Ao, J. P.; Ohno, Y.

2013-06-01

The dry recessed-gate GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) on AlGaN/GaN heterostructure using boron trichloride (BCl3) as etching gas were fabricated and characterized. Etching with different etching power was conducted. Devices with silicon tetrachloride (SiCl4) etching gas were also prepared for comparison. Field-effect mobility and interface state density were extracted from current-voltage (I-V) characteristics. GaN MOSFETs on AlGaN/GaN heterostructure with BCl3 based dry recess achieved a high maximum electron mobility of 141.5 cm2V-1s-1 and a low interface state density.

Surface passivation of mixed-halide perovskite CsPb(BrxI1-x)3 nanocrystals by selective etching for improved stability.

PubMed

Jing, Qiang; Zhang, Mian; Huang, Xiang; Ren, Xiaoming; Wang, Peng; Lu, Zhenda

2017-06-08

In recent years, there has been an unprecedented rise in the research of halide perovskites because of their important optoelectronic applications, including photovoltaic cells, light-emitting diodes, photodetectors and lasers. The most pressing question concerns the stability of these materials. Here faster degradation and PL quenching are observed at higher iodine content for mixed-halide perovskite CsPb(Br x I 1-x ) 3 nanocrystals, and a simple yet effective method is reported to significantly enhance their stability. After selective etching with acetone, surface iodine is partially etched away to form a bromine-rich surface passivation layer on mixed-halide perovskite nanocrystals. This passivation layer remarkably stabilizes the nanocrystals, making their PL intensity improved by almost three orders of magnitude. It is expected that a similar passivation layer can also be applied to various other kinds of perovskite materials with poor stability issues.

Temperature Rise during Primer, Adhesive, and Composite Resin Photopolymerization of a Low-Shrinkage Composite Resin under Caries-Like Dentin Lesions

PubMed Central

Mousavinasab, Sayed-Mostafa; Khoroushi, Maryam; Moharreri, Mohammadreza

2012-01-01

Objective. This study evaluated temperature rise of low-shrinkage (LS) self-etch primer (P), LS self-etch adhesive (A), and P90 silorane-based composite resin systems, photopolymerized under normal and artificially demineralized dentin. Methods. Forty 1.5 mm-thick dentin discs were prepared from sound human molars, half of which were demineralized. Temperature rise was measured during photopolymerization using a K-type thermocouple under the discs: 10 s and 40 s irradiation of the discs (controls/groups 1 and 2); 10 s irradiation of primer (P), 10 s irradiation of adhesive (A), 40 s irradiation of P90 without P and A, and 40 s irradiation of P90 with P and A (groups 3 to 6, resp.). The samples were photopolymerized using an LED unit under 550 mW/cm2 light intensity. Data was analyzed using repeated measures ANOVA and paired-sample t-test (α = 0.05). Results. There were no significant differences in temperature rise means between the two dentin samples for each irradiation duration (P > 0.0001), with significant differences between the two irradiation durations (P > 0.0001). Temperature rise measured with 40 s irradiation was significantly higher than that of 10 s duration for undemineralized and demineralized dentin P < 0.0001). Conclusions. Light polymerization of P90 low-shrinkage composite resin resulted in temperature rise approaching threshold value under artificially demineralized and undemineralized dentin. PMID:23320185

Overcoming etch challenges related to EUV based patterning (Conference Presentation)

NASA Astrophysics Data System (ADS)

Metz, Andrew W.; Cottle, Hongyun; Honda, Masanobu; Morikita, Shinya; Kumar, Kaushik A.; Biolsi, Peter

2017-04-01

Research and development activities related to Extreme Ultra Violet [EUV] defined patterning continue to grow for < 40 nm pitch applications. The confluence of high cost and extreme process control challenges of Self-Aligned Quad Patterning [SAQP] with continued momentum for EUV ecosystem readiness could provide cost advantages in addition to improved intra-level overlay performance relative to multiple patterning approaches. However, Line Edge Roughness [LER] and Line Width Roughness [LWR] performance of EUV defined resist images are still far from meeting technology needs or ITRS spec performance. Furthermore, extreme resist height scaling to mitigate flop over exacerbates the plasma etch trade-offs related to traditional approaches of PR smoothing, descum implementation and maintaining 2D aspect ratios of short lines or elliptical contacts concurrent with ultra-high photo resist [PR] selectivity. In this paper we will discuss sources of LER/LWR, impact of material choice, integration, and innovative plasma process techniques and describe how TELTM VigusTM CCP Etchers can enhance PR selectivity, reduce LER/LWR, and maintain 2D aspect ratio of incoming patterns. Beyond traditional process approaches this paper will show the utility of: [1] DC Superposition in enhancing EUV resist hardening and selectivity, increasing resistance to stress induced PR line wiggle caused by CFx passivation, and mitigating organic planarizer wiggle; [2] Quasi Atomic Layer Etch [Q-ALE] for ARC open eliminating the tradeoffs between selectivity, CD, and shrink ratio control; and [3] ALD+Etch FUSION technology for feature independent CD shrink and LER reduction. Applicability of these concepts back transferred to 193i based lithography is also confirmed.

Anodic etching of GaN based film with a strong phase-separated InGaN/GaN layer: Mechanism and properties

NASA Astrophysics Data System (ADS)

Gao, Qingxue; Liu, Rong; Xiao, Hongdi; Cao, Dezhong; Liu, Jianqiang; Ma, Jin

2016-11-01

A strong phase-separated InGaN/GaN layer, which consists of multiple quantum wells (MQW) and superlattices (SL) layers and can produce a blue wavelength spectrum, has been grown on n-GaN thin film, and then fabricated into nanoporous structures by electrochemical etching method in oxalic acid. Scanning electron microscopy (SEM) technique reveals that the etching voltage of 8 V leads to a vertically aligned nanoporous structure, whereas the films etched at 15 V show branching pores within the n-GaN layer. Due to the low doping concentration of barriers (GaN layers) in the InGaN/GaN layer, we observed a record-low rate of etching (<100 nm/min) and nanopores which are mainly originated from the V-pits in the phase-separated layer. In addition, there exists a horizontal nanoporous structure at the interface between the phase-separated layer and the n-GaN layer, presumably resulting from the high transition of electrons between the barrier and the well (InGaN layer) at the interface. As compared to the as-grown MQW structure, the etched MQW structure exhibits a photoluminescence (PL) enhancement with a partial relaxation of compressive stress due to the increased light-extracting surface area and light-guiding effect. Such a compressive stress relaxation can be further confirmed by Raman spectra.

Surface Nanostructures Formed by Phase Separation of Metal Salt-Polymer Nanocomposite Film for Anti-reflection and Super-hydrophobic Applications

NASA Astrophysics Data System (ADS)

Con, Celal; Cui, Bo

2017-12-01

This paper describes a simple and low-cost fabrication method for multi-functional nanostructures with outstanding anti-reflective and super-hydrophobic properties. Our method employed phase separation of a metal salt-polymer nanocomposite film that leads to nanoisland formation after etching away the polymer matrix, and the metal salt island can then be utilized as a hard mask for dry etching the substrate or sublayer. Compared to many other methods for patterning metallic hard mask structures, such as the popular lift-off method, our approach involves only spin coating and thermal annealing, thus is more cost-efficient. Metal salts including aluminum nitrate nonahydrate (ANN) and chromium nitrate nonahydrate (CNN) can both be used, and high aspect ratio (1:30) and high-resolution (sub-50 nm) pillars etched into silicon can be achieved readily. With further control of the etching profile by adjusting the dry etching parameters, cone-like silicon structure with reflectivity in the visible region down to a remarkably low value of 2% was achieved. Lastly, by coating a hydrophobic surfactant layer, the pillar array demonstrated a super-hydrophobic property with an exceptionally high water contact angle of up to 165.7°.

Surface Nanostructures Formed by Phase Separation of Metal Salt-Polymer Nanocomposite Film for Anti-reflection and Super-hydrophobic Applications.

PubMed

Con, Celal; Cui, Bo

2017-12-16

This paper describes a simple and low-cost fabrication method for multi-functional nanostructures with outstanding anti-reflective and super-hydrophobic properties. Our method employed phase separation of a metal salt-polymer nanocomposite film that leads to nanoisland formation after etching away the polymer matrix, and the metal salt island can then be utilized as a hard mask for dry etching the substrate or sublayer. Compared to many other methods for patterning metallic hard mask structures, such as the popular lift-off method, our approach involves only spin coating and thermal annealing, thus is more cost-efficient. Metal salts including aluminum nitrate nonahydrate (ANN) and chromium nitrate nonahydrate (CNN) can both be used, and high aspect ratio (1:30) and high-resolution (sub-50 nm) pillars etched into silicon can be achieved readily. With further control of the etching profile by adjusting the dry etching parameters, cone-like silicon structure with reflectivity in the visible region down to a remarkably low value of 2% was achieved. Lastly, by coating a hydrophobic surfactant layer, the pillar array demonstrated a super-hydrophobic property with an exceptionally high water contact angle of up to 165.7°.

A PDMS membrane microvalve with one-dimensional line valve seat for robust microfluidics

NASA Astrophysics Data System (ADS)

Park, Chin-Sung; Hwang, Kyu-Youn; Jung, Wonjong; Namkoong, Kak; Chung, Wonseok; Kim, Joon-Ho; Huh, Nam

2014-02-01

We have developed a monolithic polydimethylsiloxane (PDMS) membrane microvalve with an isotropically etched valve seat for robust microfluidics. In order to avoid bonding or sticking of the PDMS membrane to the valve seat during the bonding process, the valve seat was wet-etched to be a one-dimensional line instead of a plane. The simple wet-etching technique allowed for the fabrication of an anti-bonding architecture in a scalable manner, and it intrinsically prevented contact between the PDMS membrane and valve seat when no external force was applied (i.e., normally open). This approach enables the permanent device assembly so that the microfluidic chip can be operable in a wide range of fluid pressures (e.g., over 200 kPa) without any leakage and sticking problems.

X-ray diffraction gratings: Precise control of ultra-low blaze angle via anisotropic wet etching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voronov, Dmitriy L.; Naulleau, Patrick; Gullikson, Eric M.

2016-07-25

Diffraction gratings are used from micron to nanometer wavelengths as dispersing elements in optical instruments. At shorter wavelengths, crystals can be used as diffracting elements, but due to the 3D nature of the interaction with light are wavelength selective rather than wavelength dispersing. There is an urgent need to extend grating technology into the x-ray domain of wavelengths from 1 to 0.1 nm, but this requires the use of gratings that have a faceted surface in which the facet angles are very small, typically less than 1°. Small facet angles are also required in the extreme ultra-violet and soft x-ray energymore » ranges in free electron laser applications, in order to reduce power density below a critical damage threshold. In this work, we demonstrate a technique based on anisotropic etching of silicon designed to produce very small angle facets with a high degree of perfection.« less

Thin layer imaging process for microlithography using radiation at strongly attenuated wavelengths

DOEpatents

Wheeler, David R.

2004-01-06

A method for patterning of resist surfaces which is particularly advantageous for systems having low photon flux and highly energetic, strongly attenuated radiation. A thin imaging layer is created with uniform silicon distribution in a bilayer format. An image is formed by exposing selected regions of the silylated imaging layer to radiation. The radiation incident upon the silyliated resist material results in acid generation which either catalyzes cleavage of Si--O bonds to produce moieties that are volatile enough to be driven off in a post exposure bake step or produces a resist material where the exposed portions of the imaging layer are soluble in a basic solution, thereby desilylating the exposed areas of the imaging layer. The process is self limiting due to the limited quantity of silyl groups within each region of the pattern. Following the post exposure bake step, an etching step, generally an oxygen plasma etch, removes the resist material from the de-silylated areas of the imaging layer.

Homogeneity of Ge-rich nanostructures as characterized by chemical etching and transmission electron microscopy.

PubMed

Bollani, Monica; Chrastina, Daniel; Montuori, Valeria; Terziotti, Daniela; Bonera, Emiliano; Vanacore, Giovanni M; Tagliaferri, Alberto; Sordan, Roman; Spinella, Corrado; Nicotra, Giuseppe

2012-02-03

The extension of SiGe technology towards new electronic and optoelectronic applications on the Si platform requires that Ge-rich nanostructures be obtained in a well-controlled manner. Ge deposition on Si substrates usually creates SiGe nanostructures with relatively low and inhomogeneous Ge content. We have realized SiGe nanostructures with a very high (up to 90%) Ge content. Using substrate patterning, a regular array of nanostructures is obtained. We report that electron microscopy reveals an abrupt change in Ge content of about 20% between the filled pit and the island, which has not been observed in other Ge island systems. Dislocations are mainly found within the filled pit and only rarely in the island. Selective chemical etching and electron energy-loss spectroscopy reveal that the island itself is homogeneous. These Ge-rich islands are possible candidates for electronic applications requiring locally induced stress, and optoelectronic applications which exploit the Ge-like band structure of Ge-rich SiGe.

A new universal simplified adhesive: 36-Month randomized double-blind clinical trial.

PubMed

Loguercio, Alessandro D; de Paula, Eloisa Andrade; Hass, Viviane; Luque-Martinez, Issis; Reis, Alessandra; Perdigão, Jorge

2015-09-01

It is still debatable which technique should be used with universal adhesives, either etch-and-rinse (wet or dry) or self-etch strategy (with or without selective enamel etching). To evaluate the 36-month clinical performance of Scotchbond Universal Adhesive (SU, 3M ESPE) in non-carious cervical lesions (NCCLs) using two evaluation criteria. Thirty-nine patients participated in this study. Two-hundred restorations were assigned to four groups: ERm: etch-and-rinse+moist dentin; ERd: etch-and-rinse+dry dentin; Set: selective enamel etching; and SE: self-etch. The same composite resin was inserted for all restorations in up to 3 increments. The restorations were evaluated at baseline and at 6-, 18-, and 36-months using both the FDI and the USPHS criteria. Statistical analyses were performed with Friedman repeated measures ANOVA by rank and McNemar test for significance in each pair (α=0.05). Eight restorations (ERm: 1; ERd: 1; Set: 1 and SE: 5) were lost after 36 months, but only significant for SE when compared with baseline (p=0.02 for either criteria). Marginal staining occurred in 6.8% of the restorations (groups ERm, ERd, and Set) and 17.5% of the restorations (group SE), with significant difference for each group when compared with baseline using the FDI criteria (p<0.04), while statistical significance was reached only for SE when compared with baseline using the USPHS criteria (p<0.03). Twenty-eight and 49 restorations were scored as bravo for marginal adaptation using the USPHS and FDI criteria, respectively, with significant difference for each group when compared with baseline (p<0.05). While there was no statistical difference among bonding strategies when a universal adhesive was used, there were signs of degradation when the universal adhesive was applied in SE mode. The FDI criteria remain more sensitive than the USPHS criteria, especially for the criteria marginal staining and marginal adaptation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Method to fabricate functionalized conical nanopores

DOEpatents

Small, Leo J.; Spoerke, Erik David; Wheeler, David R.

2016-07-12

A pressure-based chemical etch method is used to shape polymer nanopores into cones. By varying the pressure, the pore tip diameter can be controlled, while the pore base diameter is largely unaffected. The method provides an easy, low-cost approach for conically etching high density nanopores.

Plasma-deposited amorphous silicon carbide films for micromachined fluidic channels

NASA Astrophysics Data System (ADS)

Wuu, Dong-Sing; Horng, Ray-Hua; Chan, Chia-Chi; Lee, Yih-Shing

1999-04-01

The stress properties of the a-SiC:H films on Si by plasma-enhanced chemical vapor deposition (PECVD) are investigated. It is found that the stability of the a-SiC:H films relates to Si-H bonds breaking and changes the stress toward tensile. No evident reduction in the content of Si-H bonds after thermal cycles was found in the carbon-rich samples. Moreover, a new method to fabricate microchannels by through-hole etching with subsequent planarization is proposed. The process is based on etching out the deep grooves through a perforated a-SiC:H membrane, where poly-Si is used as a sacrificial layer to define the channel structure, followed by PECVD sealing the SiC:H membrane. In order to improve the etching performance, the agitated KOH etch is performed at low temperatures (<50°C). The process technology is demonstrated on the fabrication of microfluidic channels with the low-stress (<0.1 GPa) a-SiC:H membranes.

Antireflective glass nanoholes on optical lenses.

PubMed

Lee, Youngseop; Bae, Sang-In; Eom, Jaehyeon; Suh, Ho-Cheol; Jeong, Ki-Hun

2018-05-28

Antireflective structures, inspired from moth eyes, are still reserved for practical use due to their large-area nanofabrication and mechanical stability. Here we report an antireflective optical lens with large-area glass nanoholes. The nanoholes increase light transmission due to the antireflective effect, depending on geometric parameters such as fill factor and height. The glass nanoholes of low effective refractive index are achieved by using solid-state dewetting of ultrathin silver film, reactive ion etching, and wet etching. An ultrathin silver film is transformed into nanoholes for an etch mask in reactive ion etching after thermal annealing at a low temperature. Unlike conventional nanopillars, nanoholes exhibit high light transmittance with enhancement of ~4% over the full visible range as well as high mechanical hardness. Also, an antireflective glass lens is achieved by directly employing nanoholes on the lens surface. Glass nanoholes of highly enhanced optical and mechanical performance can be directly utilized for commercial glass lenses in various imaging and lighting applications.

Formation of dysprosium carbide on the graphite (0001) surface

DOE PAGES

Lii-Rosales, Ann; Zhou, Yinghui; Wallingford, Mark; ...

2017-07-12

When using scanning tunneling microscopy, we characterize a surface carbide that forms such that Dy is deposited on the basal plane of graphite. In order to form carbide islands on terraces, Dy is first deposited at 650–800 K, which forms large metallic islands. Upon annealing at 1000 K, these clusters convert to carbide. Deposition directly at 1000 K is ineffective because nucleation on terraces is inhibited. Reaction is signaled by the fact that each carbide cluster is partially or totally surrounded by an etch pit. The etch pit is one carbon layer deep for most carbide clusters. Carbide clusters aremore » also identifiable by striations on their surfaces. Based on mass balance, and assuming that only the surface layer of carbon is involved in the reaction, the carbide has stoichiometry D y 2 C . This is Dy-rich compared with the most common bulk carbide Dy C 2 , which may reflect limited surface carbon transport to the carbide.« less

Deep Etching Process Developed for the Fabrication of Silicon Carbide Microsystems

NASA Technical Reports Server (NTRS)

Beheim, Glenn M.

2000-01-01

Silicon carbide (SiC), because of its superior electrical and mechanical properties at elevated temperatures, is a nearly ideal material for the microminiature sensors and actuators that are used in harsh environments where temperatures may reach 600 C or greater. Deep etching using plasma methods is one of the key processes used to fabricate silicon microsystems for more benign environments, but SiC has proven to be a more difficult material to etch, and etch depths in SiC have been limited to several micrometers. Recently, the Sensors and Electronics Technology Branch at the NASA Glenn Research Center at Lewis Field developed a plasma etching process that was shown to be capable of etching SiC to a depth of 60 mm. Deep etching of SiC is achieved by inductive coupling of radiofrequency electrical energy to a sulfur hexafluoride (SF6) plasma to direct a high flux of energetic ions and reactive fluorine atoms to the SiC surface. The plasma etch is performed at a low pressure, 5 mtorr, which together with a high gas throughput, provides for rapid removal of the gaseous etch products. The lateral topology of the SiC microstructure is defined by a thin film of etch-resistant material, such as indium-tin-oxide, which is patterned using conventional photolithographic processes. Ions from the plasma bombard the exposed SiC surfaces and supply the energy needed to initiate a reaction between SiC and atomic fluorine. In the absence of ion bombardment, no reaction occurs, so surfaces perpendicular to the wafer surface (the etch sidewalls) are etched slowly, yielding the desired vertical sidewalls.

Process For Patterning Dispenser-Cathode Surfaces

NASA Technical Reports Server (NTRS)

Garner, Charles E.; Deininger, William D.

1989-01-01

Several microfabrication techniques combined into process cutting slots 100 micrometer long and 1 to 5 micrometer wide into tungsten dispenser cathodes for traveling-wave tubes. Patterned photoresist serves as mask for etching underlying aluminum. Chemically-assisted ion-beam etching with chlorine removes exposed parts of aluminum layer. Etching with fluorine or chlorine trifluoride removes tungsten not masked by aluminum layer. Slots enable more-uniform low-work function coating dispensed to electron-emitting surface. Emission of electrons therefore becomes more uniform over cathode surface.

Self-templated fabrication of FeMnO3 nanoparticle-filled polypyrrole nanotubes for peroxidase mimicking with a synergistic effect and their sensitive colorimetric detection of glutathione.

PubMed

Chi, Maoqiang; Chen, Sihui; Zhong, Mengxiao; Wang, Ce; Lu, Xiaofeng

2018-06-05

A self-templated approach has been developed for the preparation of FeMnO3 nanoparticles filled in the hollow core of polypyrrole (PPy) nanotubes by an in situ polymerization process accompanied by the etching of FeMnO3 nanofibers. The prepared FeMnO3@PPy nanotubes exhibited a superior peroxidase-like activity. The catalytic reaction system has been used for the sensitive colorimetric detection of glutathione with a low detection limit and good selectivity.

Efficient Incorporation of Mg in Solution Grown GaN Crystals

NASA Astrophysics Data System (ADS)

Freitas, Jaime A., Jr.; Feigelson, Boris N.; Anderson, Travis J.

2013-11-01

Detailed spectrometry and optical spectroscopy studies carried out on GaN crystals grown in solution detect and identify Mg as the dominant shallow acceptor. Selective etching of crystals with higher Mg levels than that of the donor concentration background indicates that Mg acceptors incorporate preferentially in the N-polar face. Electrical transport measurements verified an efficient incorporation and activation of the Mg acceptors. These results suggest that this growth method has the potential to produce p-type doped epitaxial layers or p-type substrates characterized by high hole concentration and low defect density.

Recovery of GaN surface after reactive ion etching

NASA Astrophysics Data System (ADS)

Fan, Qian; Chevtchenko, S.; Ni, Xianfeng; Cho, Sang-Jun; Morko, Hadis

2006-02-01

Surface properties of GaN subjected to reactive ion etching and the impact on device performance have been investigated by surface potential, optical and electrical measurements. Different etching conditions were studied and essentially high power levels and low chamber pressures resulted in higher etch rates accompanying with the roughening of the surface morphology. Surface potential for the as-grown c-plane GaN was found to be in the range of 0.5~0.7 V using Scanning Kevin Probe Microscopy. However, after reactive ion etching at a power level of 300 W, it decreased to 0.1~0.2 V. A nearly linear reduction was observed on c-plane GaN with increasing power. The nonpolar a-plane GaN samples also showed large surface band bending before and after etching. Additionally, the intensity of the near band-edge photoluminescence decreased and the free carrier density increased after etching. These results suggest that the changes in the surface potential may originate from the formation of possible nitrogen vacancies and other surface oriented defects and adsorbates. To recover the etched surface, N II plasma, rapid thermal annealing, and etching in wet KOH were performed. For each of these methods, the surface potential was found to increase by 0.1~0.3 V, also the reverse leakage current in Schottky diodes fabricated on treated samples was reduced considerably compared with as-etched samples, which implies a partial-to-complete recovery from the plasma-induced damage.

Fabrication of micro-patterned aluminum surfaces for low ice adhesion strength

NASA Astrophysics Data System (ADS)

Jeon, Jaehyeon; Jang, Hanmin; Chang, Jinho; Lee, Kwan-Soo; Kim, Dong Rip

2018-05-01

We report a fabrication method to obtain a low-ice-adhesion aluminum surface by surface texturing using solution etching and subsequent thin-film coating. Specifically, the textured surface has microstructures of a low aspect ratio, that is, with a much smaller height than width. Such microstructures can effectively reduce ice-adhesion strengths by sliding the ice during detachment. Because our method is based on solution etching, it can be applied to curved surfaces with complex shapes for uniformly constructing the morphology of a low-ice-adhesion aluminum surface. Finally, the low-ice-adhesion aluminum surface reduces the ice-adhesion strengths by up to 95%.

SFG analysis of the molecular structures at the surfaces and buried interfaces of PECVD ultralow-dielectric constant pSiCOH: Reactive ion etching and dielectric recovery

NASA Astrophysics Data System (ADS)

Myers, John N.; Zhang, Xiaoxian; Huang, Huai; Shobha, Hosadurga; Grill, Alfred; Chen, Zhan

2017-05-01

Molecular structures at the surface and buried interface of an amorphous ultralow-k pSiCOH dielectric film were quantitatively characterized before and after reactive ion etching (RIE) and subsequent dielectric repair using sum frequency generation (SFG) vibrational spectroscopy and Auger electron spectroscopy. SFG results indicated that RIE treatment of the pSiCOH film resulted in a depletion of ˜66% of the surface methyl groups and changed the orientation of surface methyl groups from ˜47° to ˜40°. After a dielectric recovery process that followed the RIE treatment, the surface molecular structure was dominated by methyl groups with an orientation of ˜55° and the methyl surface coverage at the repaired surface was 271% relative to the pristine surface. Auger depth profiling indicated that the RIE treatment altered the top ˜25 nm of the film and that the dielectric recovery treatment repaired the top ˜9 nm of the film. Both SFG and Auger profiling results indicated that the buried SiCNH/pSiCOH interface was not affected by the RIE or the dielectric recovery process. Beyond characterizing low-k materials, the developed methodology is general and can be used to distinguish and characterize different molecular structures and elemental compositions at the surface, in the bulk, and at the buried interface of many different polymer or organic thin films.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, D.; Sankaranarayanan, S.; Khachariya, D.

We demonstrate a method for nanowire formation by natural selection during wet anisotropic chemical etching in boiling phosphoric acid. Nanowires of sub-10 nm lateral dimensions and lengths of 700 nm or more are naturally formed during the wet etching due to the convergence of the nearby crystallographic hexagonal etch pits. These nanowires are site controlled when formed in augmentation with dry etching. Temperature and power dependent photoluminescence characterizations confirm excitonic transitions up to room temperature. The exciton confinement is enhanced by using two-dimensional confinement whereby enforcing greater overlap of the electron-hole wave-functions. The surviving nanowires have less defects and a small temperaturemore » variation of the output electroluminescent light. We have observed superluminescent behaviour of the light emitting diodes formed on these nanowires. There is no observable efficiency roll off for current densities up to 400 A/cm{sup 2}.« less

Development and evaluation of magnesium oxide-based ceramics for chamber parts in mass-production plasma etching equipment

NASA Astrophysics Data System (ADS)

Kasashima, Yuji; Tsutsumi, Kota; Mitomi, Shinzo; Uesugi, Fumihiko

2017-06-01

In mass-production plasma etching equipment, the corrosion of ceramic chamber parts reduces the production yield of LSI and overall equipment effectiveness (OEE) owing to contamination, short useful life, and particle generation. Novel ceramics that can improve the production yield and OEE are highly required. We develop magnesium oxide (MgO)-based ceramics and evaluate them under mass-production plasma etching conditions. The results of this study indicate that the developed MgO-based ceramics with high mechanical properties and low electric resistivity have a higher resistance to corrosion in plasma etching using CF4 gas than Si and conventional ceramic materials such as aluminum oxide and yttrium oxide.

Fundamental Studies on Ambient Temperature Creep Deformation Behavior of Alpha and Alpha-Beta Titanium Alloys

DTIC Science & Technology

1994-02-15

Solutions [49] A-Etch 25 (mL) Hydrofluoric Acid (HF 50%) 25 Nitric Acid Cone (HN03) 50 Glycerine R-Etch 18.5 gm (17 mL) Benzalkonium Chloride 35 (mL... Reduction Project (0704-0188) Washington, DC 20503. 1. AGENCY USE ONLY (Leave Blank) 2. REPORT DATE 1994 3. REPORT TYPE AND DATES COVERED Final 4...K and a 60% reduction in area was given for all of the alloys. This work was found to be sufficient to recrystallize all of the alloys within 12

Inductively Coupled Plasma and Electron Cyclotron Resonance Plasma Etching of InGaAlP Compound Semiconductor System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abernathy, C.R.; Hobson, W.S.; Hong, J.

1998-11-04

Current and future generations of sophisticated compound semiconductor devices require the ability for submicron scale patterning. The situation is being complicated since some of the new devices are based on a wider diversity of materials to be etched. Conventional IUE (Reactive Ion Etching) has been prevalent across the industry so far, but has limitations for materials with high bond strengths or multiple elements. IrI this paper, we suggest high density plasmas such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma), for the etching of ternary compound semiconductors (InGaP, AIInP, AlGaP) which are employed for electronic devices like heterojunctionmore » bipolar transistors (HBTs) or high electron mobility transistors (HEMTs), and photonic devices such as light-emitting diodes (LEDs) and lasers. High density plasma sources, opeiating at lower pressure, are expected to meet target goals determined in terms of etch rate, surface morphology, surface stoichiometry, selectivity, etc. The etching mechanisms, which are described in this paper, can also be applied to other III-V (GaAs-based, InP-based) as well as III-Nitride since the InGaAIP system shares many of the same properties.« less

Etching of polymers, proteins and bacterial spores by atmospheric pressure DBD plasma in air

NASA Astrophysics Data System (ADS)

Kuzminova, A.; Kretková, T.; Kylián, O.; Hanuš, J.; Khalakhan, I.; Prukner, V.; Doležalová, E.; Šimek, M.; Biederman, H.

2017-04-01

Many studies proved that non-equilibrium discharges generated at atmospheric pressure are highly effective for the bio-decontamination of surfaces of various materials. One of the key processes that leads to a desired result is plasma etching and thus the evaluation of etching rates of organic materials is of high importance. However, the comparison of reported results is rather difficult if impossible as different authors use diverse sources of atmospheric plasma that are operated at significantly different operational parameters. Therefore, we report here on the systematic study of the etching of nine different common polymers that mimic the different structures of more complicated biological systems, bovine serum albumin (BSA) selected as the model protein and spores of Bacillus subtilis taken as a representative of highly resistant micro-organisms. The treatment of these materials was performed by means of atmospheric pressure dielectric barrier discharge (DBD) sustained in open air at constant conditions. All tested polymers, BSA and spores, were readily etched by DBD plasma. However, the measured etching rates were found to be dependent on the chemical structure of treated materials, namely on the presence of oxygen in the structure of polymers.

Plasma etching a ceramic composite. [evaluating microstructure

NASA Technical Reports Server (NTRS)

Hull, David R.; Leonhardt, Todd A.; Sanders, William A.

1992-01-01

Plasma etching is found to be a superior metallographic technique for evaluating the microstructure of a ceramic matrix composite. The ceramic composite studied is composed of silicon carbide whiskers (SiC(sub W)) in a matrix of silicon nitride (Si3N4), glass, and pores. All four constituents are important in evaluating the microstructure of the composite. Conventionally prepared samples, both as-polished or polished and etched with molten salt, do not allow all four constituents to be observed in one specimen. As-polished specimens allow examination of the glass phase and porosity, while molten salt etching reveals the Si3N4 grain size by removing the glass phase. However, the latter obscures the porosity. Neither technique allows the SiC(sub W) to be distinguished from the Si3N4. Plasma etching with CF4 + 4 percent O2 selectively attacks the Si3N4 grains, leaving SiC(sub W) and glass in relief, while not disturbing the pores. An artifact of the plasma etching reaction is the deposition of a thin layer of carbon on Si3N4, allowing Si3N4 grains to be distinguished from SiC(sub W) by back scattered electron imaging.

Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Provine, J., E-mail: jprovine@stanford.edu; Schindler, Peter; Kim, Yongmin

2016-06-15

The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiN{sub x}), particularly for use a low k dielectric spacer. One of the key material properties needed for SiN{sub x} films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiN{sub x} and evaluate the film’s WER in 100:1 dilutions of HF in H{sub 2}O. The remote plasma capability available in PEALD, enabled controlling the density of the SiN{submore » x} film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiN{sub x} of 6.1 Å/min, which is similar to WER of SiN{sub x} from LPCVD reactions at 850 °C.« less

Tuning of structural, light emission and wetting properties of nanostructured copper oxide-porous silicon matrix formed on electrochemically etched copper-coated silicon substrates

NASA Astrophysics Data System (ADS)

Naddaf, M.

2017-01-01

Matrices of copper oxide-porous silicon nanostructures have been formed by electrochemical etching of copper-coated silicon surfaces in HF-based solution at different etching times (5-15 min). Micro-Raman, X-ray diffraction and X-ray photoelectron spectroscopy results show that the nature of copper oxide in the matrix changes from single-phase copper (I) oxide (Cu2O) to single-phase copper (II) oxide (CuO) on increasing the etching time. This is accompanied with important variation in the content of carbon, carbon hydrides, carbonyl compounds and silicon oxide in the matrix. The matrix formed at the low etching time (5 min) exhibits a single broad "blue" room-temperature photoluminescence (PL) band. On increasing the etching time, the intensity of this band decreases and a much stronger "red" PL band emerges in the PL spectra. The relative intensity of this band with respect to the "blue" band significantly increases on increasing the etching time. The "blue" and "red" PL bands are attributed to Cu2O and porous silicon of the matrix, respectively. In addition, the water contact angle measurements reveal that the hydrophobicity of the matrix surface can be tuned from hydrophobic to superhydrophobic state by controlling the etching time.

Model polymer etching and surface modification by a time modulated RF plasma jet: role of atomic oxygen and water vapor

NASA Astrophysics Data System (ADS)

Luan, P.; Knoll, A. J.; Wang, H.; Kondeti, V. S. S. K.; Bruggeman, P. J.; Oehrlein, G. S.

2017-01-01

The surface interaction of a well-characterized time modulated radio frequency (RF) plasma jet with polystyrene, poly(methyl methacrylate) and poly(vinyl alcohol) as model polymers is investigated. The RF plasma jet shows fast polymer etching but mild chemical modification with a characteristic carbonate ester and NO formation on the etched surface. By varying the plasma treatment conditions including feed gas composition, environment gaseous composition, and treatment distance, we find that short lived species, especially atomic O for Ar/1% O2 and 1% air plasma and OH for Ar/1% H2O plasma, play an essential role for polymer etching. For O2 containing plasma, we find that atomic O initiates polymer etching and the etching depth mirrors the measured decay of O atoms in the gas phase as the nozzle-surface distance increases. The etching reaction probability of an O atom ranging from 10-4 to 10-3 is consistent with low pressure plasma research. We also find that adding O2 and H2O simultaneously into Ar feed gas quenches polymer etching compared to adding them separately which suggests the reduction of O and OH density in Ar/O2/H2O plasma.

Mushroom-free selective epitaxial growth of Si, SiGe and SiGe:B raised sources and drains

NASA Astrophysics Data System (ADS)

Hartmann, J. M.; Benevent, V.; Barnes, J. P.; Veillerot, M.; Lafond, D.; Damlencourt, J. F.; Morvan, S.; Prévitali, B.; Andrieu, F.; Loubet, N.; Dutartre, D.

2013-05-01

We have evaluated various Cyclic Selective Epitaxial Growth/Etch (CSEGE) processes in order to grow "mushroom-free" Si and SiGe:B Raised Sources and Drains (RSDs) on each side of ultra-short gate length Extra-Thin Silicon-On-Insulator (ET-SOI) transistors. The 750 °C, 20 Torr Si CSEGE process we have developed (5 chlorinated growth steps with four HCl etch steps in-between) yielded excellent crystalline quality, typically 18 nm thick Si RSDs. Growth was conformal along the Si3N4 sidewall spacers, without any poly-Si mushrooms on top of unprotected gates. We have then evaluated on blanket 300 mm Si(001) wafers the feasibility of a 650 °C, 20 Torr SiGe:B CSEGE process (5 chlorinated growth steps with four HCl etch steps in-between, as for Si). As expected, the deposited thickness decreased as the total HCl etch time increased. This came hands in hands with unforeseen (i) decrease of the mean Ge concentration (from 30% down to 26%) and (ii) increase of the substitutional B concentration (from 2 × 1020 cm-3 up to 3 × 1020 cm-3). They were due to fluctuations of the Ge concentration and of the atomic B concentration [B] in such layers (drop of the Ge% and increase of [B] at etch step locations). Such blanket layers were a bit rougher than layers grown using a single epitaxy step, but nevertheless of excellent crystalline quality. Transposition of our CSEGE process on patterned ET-SOI wafers did not yield the expected results. HCl etch steps indeed helped in partly or totally removing the poly-SiGe:B mushrooms on top of the gates. This was however at the expense of the crystalline quality and 2D nature of the ˜45 nm thick Si0.7Ge0.3:B recessed sources and drains selectively grown on each side of the imperfectly protected poly-Si gates. The only solution we have so far identified that yields a lesser amount of mushrooms while preserving the quality of the S/D is to increase the HCl flow during growth steps.

Endpoint in plasma etch process using new modified w-multivariate charts and windowed regression

NASA Astrophysics Data System (ADS)

Zakour, Sihem Ben; Taleb, Hassen

2017-09-01

Endpoint detection is very important undertaking on the side of getting a good understanding and figuring out if a plasma etching process is done in the right way, especially if the etched area is very small (0.1%). It truly is a crucial part of supplying repeatable effects in every single wafer. When the film being etched has been completely cleared, the endpoint is reached. To ensure the desired device performance on the produced integrated circuit, the high optical emission spectroscopy (OES) sensor is employed. The huge number of gathered wavelengths (profiles) is then analyzed and pre-processed using a new proposed simple algorithm named Spectra peak selection (SPS) to select the important wavelengths, then we employ wavelet analysis (WA) to enhance the performance of detection by suppressing noise and redundant information. The selected and treated OES wavelengths are then used in modified multivariate control charts (MEWMA and Hotelling) for three statistics (mean, SD and CV) and windowed polynomial regression for mean. The employ of three aforementioned statistics is motivated by controlling mean shift, variance shift and their ratio (CV) if both mean and SD are not stable. The control charts show their performance in detecting endpoint especially W-mean Hotelling chart and the worst result is given by CV statistic. As the best detection of endpoint is given by the W-Hotelling mean statistic, this statistic will be used to construct a windowed wavelet Hotelling polynomial regression. This latter can only identify the window containing endpoint phenomenon.

Cleaved-edge-overgrowth nanogap electrodes.

PubMed

Luber, Sebastian M; Bichler, Max; Abstreiter, Gerhard; Tornow, Marc

2011-02-11

We present a method to fabricate multiple metal nanogap electrodes of tailored width and distance in parallel, on the cleaved plane of a GaAs/AlGaAs heterostructure. The three-dimensional patterned structures are obtained by a combination of molecular-beam-epitaxial regrowth on a crystal facet, using the cleaved-edge-overgrowth (CEO) method, and subsequent wet selective etching and metallization steps. SEM and AFM studies reveal smooth and co-planar electrodes of width and distance of the order of 10 nm. Preliminary electrical characterization indicates electrical gap insulation in the 100 MΩ range with kΩ lead resistance. We propose our methodology to realize multiple electrode geometries that would allow investigation of the electrical conductivity of complex nanoscale objects such as branched organic molecules.

In situ CF3 Detection in Low Pressure Inductive Discharges by Fourier Transform Infrared Spectroscopy

NASA Technical Reports Server (NTRS)

Kim, J. S.; Cappelli, M. A.; Sharma, S. P.; Arnold, J. O. (Technical Monitor)

1998-01-01

The detection of CF(x) (x=1-3) radicals in low pressure discharges using source gases such as CF4 and CHF3 is of importance to the understanding of their chemical structure and relevance in plasma based etching processes. These radicals are known to contribute to the formation of fluorocarbon polymer films, which affect the selectivity and anisotropy of etching. In this study, we present preliminary results of the quantitative measurement of trifluoromethyl radicals, CF3, in low pressure discharges. The discharge studied here is an inductively (transformer) coupled plasma (ICP) source in the GEC reference cell, operating on pure CF4 at pressures ranging from 10 - 100 mTorr, This plasma source generates higher electron number densities at lower operating pressures than obtainable with the parallel-plate capacitively coupled version of the GEC reference cell. Also, this expanded operating regime is more relevant to new generations of industrial plasma reactors being used by the microelectronics industry. Fourier transform infrared (FTIR) spectroscopy is employed to observe the absorption band of CF3 radicals in the electronic ground state X2Al in the region of 1233-1270/cm. The spectrometer is equipped with a high sensitivity HgCdTe (MCT) detector and has a fixed resolution of 0.125/cm. The CF3 concentrations are measured for a range of operating pressures and discharge power levels.

Antibacterial Effect and Tensile Bond Strength of Self-etching Adhesive Resins with and without Methacryloyloxydodecylpyridinium Bromide: An in vitro Study.

PubMed

Krishnamurthy, Madhuram; Kumar, V Naveen; Leburu, Ashok; Dhanavel, Chakravarthy; Selvendran, Kasiswamy E; Praveen, Nehrudhas

2018-04-01

Aim: The aim of the present study was to compare the antibacterial activity of a self-etching primer containing antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB) (Clearfil protect bond) with a conventional self-etching primer without MDPB (Clearfil SE bond) against Streptococcus mutans and the effect of incorporation of MDPB on the tensile bond strength of the experimental self-etching primer (Clearfil protect bond). Materials and methods: The antibacterial activity of the self-etching primers was assessed using agar disk diffusion method and the diameters of the zones of inhibition were measured and ranked. For tensile bond strength testing, 20 noncarious human molars were selected and randomly divided into two groups comprising 10 teeth in each group. Group I specimens were treated with Clearfil SE bond (without MDPB). Group II specimens were treated with Clearfil protect bond (with MDPB). Composite material was placed incrementally and cured for 40 seconds in all the specimens. Tensile bond strength was estimated using the Instron Universal testing machine at a crosshead speed of 1 mm/min. Results: The addition of MDPB into a self-etching primer exerts potential antibacterial effect against S. mutans. The tensile bond strength of MDPB containing self-etching primer was slightly lower than that of the conventional self-etching Clearfil protect bond primer, but the difference was not statistically significant. Conclusion: Thus, a self-etching primer containing MDPB will be a boon to adhesive dentistry as it has bactericidal property with adequate tensile bond strength. Clinical significance: The concept of prevention of extension in adhesive dentistry would result in micro/nanoleakage due to the presence of residual bacteria in the cavity. Self-etching primers with MDPB would improve the longevity of such restorations by providing adequate antibacterial activity without compromising the bond strength. Keywords: Antibacterial property, Methacryloyloxydodecy-lpyridinium bromide, Self-etching primers, Tensile bond strength.

Low Energy X-Ray and γ-Ray Detectors Fabricated on n-Type 4H-SiC Epitaxial Layer

NASA Astrophysics Data System (ADS)

Mandal, Krishna C.; Muzykov, Peter G.; Chaudhuri, Sandeep K.; Terry, J. Russell

2013-08-01

Schottky barrier diode (SBD) radiation detectors have been fabricated on n-type 4H-SiC epitaxial layers and evaluated for low energy x- and γ-rays detection. The detectors were found to be highly sensitive to soft x-rays in the 50 eV to few keV range and showed 2.1 % energy resolution for 59.6 keV gamma rays. The response to soft x-rays for these detectors was significantly higher than that of commercial off-the-shelf (COTS) SiC UV photodiodes. The devices have been characterized by current-voltage (I-V) measurements in the 94-700 K range, thermally stimulated current (TSC) spectroscopy, x-ray diffraction (XRD) rocking curve measurements, and defect delineating chemical etching. I-V characteristics of the detectors at 500 K showed low leakage current ( nA at 200 V) revealing a possibility of high temperature operation. The XRD rocking curve measurements revealed high quality of the epitaxial layer exhibiting a full width at half maximum (FWHM) of the rocking curve 3.6 arc sec. TSC studies in a wide range of temperature (94-550 K) revealed presence of relatively shallow levels ( 0.25 eV) in the epi bulk with a density 7×1013 cm-3 related to Al and B impurities and deeper levels located near the metal-semiconductor interface.

Selective Plasma Deposition of Fluorocarbon Films on SAMs

NASA Technical Reports Server (NTRS)

Crain, Mark M., III; Walsh, Kevin M.; Cohn, Robert W.

2006-01-01

A dry plasma process has been demonstrated to be useful for the selective modification of self-assembled monolayers (SAMs) of alkanethiolates. These SAMs are used, during the fabrication of semiconductor electronic devices, as etch masks on gold layers that are destined to be patterned and incorporated into the devices. The selective modification involves the formation of fluorocarbon films that render the SAMs more effective in protecting the masked areas of the gold against etching by a potassium iodide (KI) solution. This modification can be utilized, not only in the fabrication of single electronic devices but also in the fabrication of integrated circuits, microelectromechanical systems, and circuit boards. In the steps that precede the dry plasma process, a silicon mold in the desired pattern is fabricated by standard photolithographic techniques. A stamp is then made by casting polydimethylsiloxane (commonly known as silicone rubber) in the mold. The stamp is coated with an alkanethiol solution, then the stamp is pressed on the gold layer of a device to be fabricated in order to deposit the alkanethiol to form an alkanethiolate SAM in the desired pattern (see figure). Next, the workpiece is exposed to a radio-frequency plasma generated from a mixture of CF4 and H2 gases. After this plasma treatment, the SAM is found to be modified, while the exposed areas of gold remain unchanged. This dry plasma process offers the potential for forming masks superior to those formed in a prior wet etching process. Among the advantages over the wet etching process are greater selectivity, fewer pin holes in the masks, and less nonuniformity of the masks. The fluorocarbon films formed in this way may also be useful as intermediate layers for subsequent fabrication steps and as dielectric layers to be incorporated into finished products.

Pulsed operation of (Al,Ga,In)N blue laser diodes

NASA Astrophysics Data System (ADS)

Abare, Amber C.; Mack, Michael P.; Hansen, Mark W.; Sink, R. K.; Kozodoy, Peter; Keller, Sarah L.; Hu, Evelyn L.; Speck, James S.; Bowers, John E.; Mishra, Umesh K.; Coldren, Larry A.; DenBaars, Steven P.

1998-04-01

Room temperature (RT) pulsed operation of blue (420 nm) nitride based multi-quantum well (MQW) laser diodes grown on a-plane and c-plane sapphire substrates has been demonstrated. A combination of atmospheric and low pressure metal organic chemical vapor deposition (MOCVD) using a modified two-flow horizontal reactor was employed. The emission is strongly TE polarized and has a sharp transition in the far field pattern above threshold. Threshold current densities as low as 12.6 kA/cm2 were observed for 10 X 1200 micrometer lasers with uncoated reactive ion etched (RIE) facets on c-plane sapphire. Cleaved facet lasers were also demonstrated with similar performance on a-plane sapphire. Differential efficiencies as high as 7% and output powers up to 77 mW were observed. Laser diodes tested under pulsed conditions operated up to 6 hours at room temperature. Performance was limited by resistive heating during the electrical pulses. Lasing was achieved up to 95 degrees Celsius and up to a 150 ns pulse length (RT). Threshold current increased with temperature with a characteristic temperature, T0, of 125 K.

Piezoelectric micromachined acoustic emission sensors for early stage damage detection in structures

NASA Astrophysics Data System (ADS)

Kabir, Minoo; Kazari, Hanie; Ozevin, Didem

2018-03-01

Acoustic emission (AE) is a passive nondestructive evaluation (NDE) method that relies on the energy release of active flaws. The passive nature of this NDE method requires highly sensitive transducers in addition to low power and lightweight characteristics. With the advancement of micro-electro-mechanical systems (MEMS), acoustic emission (AE) transducers can be developed in low power and miniaturized. In this paper, the AE transducers operating in plate flexural mode driven piezoelectrically known as Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) are presented. The AE PMUTs are manufactured using PiezoMUMPS process by MEMSCAP and tuned to 46 kHz and 200 kHz. The PiezoMUMPs is a 5-mask level SOI (silicon-on-insulator) patterning and etching process followed by deposition of 0.5 micron Aluminum Nitride (AlN) to form piezoelectric layer to form the transducers. The AE transducers are numerically modeled using COMSOL Multiphysics software in order to optimize the performance before manufacturing. The electrometrical characterization experiments are presented. The efficiency of the proposed AE PMUTs compared to the conventional AE transducers in terms of power consumption, weight and sensitivity is presented.

Non-chemically amplified 193-nm top surface imaging photoresist development: polymer substituent and polydispersity effects

NASA Astrophysics Data System (ADS)

Kim, Myoung-Soo; Kim, Hyoung-Gi; Kim, Hyeong-Soo; Baik, Ki-Ho; Johnson, Donald W.; Cernigliaro, George J.; Minsek, David W.

1999-06-01

Thin film imaging processes such as top surface imaging (TSI) are candidates for sub-150 nm lithography using 193 nm lithography. Single component, non-chemically amplified, positive tone TSI photoresists based on phenolic polymers demonstrate good post-etch contrast, resolution, and minimal line edge roughness, in addition to being the most straightforward thin film imaging approach. In this approach, ArF laser exposure results directly in radiation- induced crosslinking of the phenolic polymer, followed by formation of a thin etch mask at the surface of the un- exposed regions by vapor-phase silylation, followed by reactive ion etching of the non-silylated regions. However, single component resists based on poly(para-hydroxystryene) (PHS), such as MicroChem's Nano MX-P7, suffer from slow photospeed as well as low silylation contrast which can cause reproducibility and line-edge-roughness problems. We report that selected aromatic substitution of the poly(para- hydroxystryene) polymer can increase the photospeed by up to a factor of four relative to un-substituted PHS. In this paper we report the synthesis and lithographic evaluations of four experimental TSI photoresists. MX-EX-1, MX-EX-2, MX- EX-3 and MX-EX-4 are non-chemically amplified resists based on aromatic substitutions of chloro- and hydroxymethyl- groups and PHS. We report optimized lithographic processing conditions, line edge roughness, silylation contrast, and compare the results to the parent PHS photoresist.

Smooth and vertical facet formation for AlGaN-based deep-UV laser diodes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogart, Katherine Huderle Andersen; Shul, Randy John; Stevens, Jeffrey

2008-10-01

Using a two-step method of plasma and wet chemical etching, we demonstrate smooth, vertical facets for use in Al{sub x} Ga{sub 1-x} N-based deep-ultraviolet laser-diode heterostructures where x = 0 to 0.5. Optimization of plasma-etching conditions included increasing both temperature and radiofrequency (RF) power to achieve a facet angle of 5 deg from vertical. Subsequent etching in AZ400K developer was investigated to reduce the facet surface roughness and improve facet verticality. The resulting combined processes produced improved facet sidewalls with an average angle of 0.7 deg from vertical and less than 2-nm root-mean-square (RMS) roughness, yielding an estimated reflectivity greatermore » than 95% of that of a perfectly smooth and vertical facet.« less

The effect of additional enamel etching and a flowable composite to the interfacial integrity of Class II adhesive composite restorations.

PubMed

Belli, S; Inokoshi, S; Ozer, F; Pereira, P N; Ogata, M; Tagami, J

2001-01-01

This in vitro study evaluated the interfacial integrity of Class II resin composite restorations. The influence of a flowable composite and additional enamel etching was also evaluated. Deep, saucer-shaped Class II cavities were prepared in the mesial and distal proximal surfaces of 25 extracted human molars and assigned to five treatment groups. The gingival margins were extended to approximately 1 mm above the CEJ in 40 cavities and below the CEJ in 10 cavities. The prepared cavities were then restored with a self-etching primer system (Clearfil Liner Bond II) and a hybrid resin composite (Clearfil AP-X), with and without a flowable composite (Protect Liner F) and additional enamel etching with 37% phosphoric acid gel (K-etchant). After finishing, polishing and thermocycling (4 and 60 degrees C, x300), the samples were longitudinally sectioned through the restorations and resin-tooth interfaces were observed directly under a laser scanning microscope. Statistical analysis indicated that the use of a flowable composite produced significantly more (p = 0.04) gap-free resin-dentin interfaces than teeth restored without the flowable composite. However, both flowable composite and enamel etching could not prevent gap formation at enamel-resin interfaces and crack formation on enamel walls.

Selective Acid Etching Improves the Bond Strength of Universal Adhesive to Sound and Demineralized Enamel of Primary Teeth.

PubMed

Antoniazzi, Bruna Feltrin; Nicoloso, Gabriel Ferreira; Lenzi, Tathiane Larissa; Soares, Fabio Zovico Maxnuck; Rocha, Rachel de Oliveira

To evaluate the influence of enamel condition and etching strategy on bond strength of a universal adhesive in primary teeth. Thirty-six primary molars were randomly assigned to six groups (n = 6) according to the enamel condition (sound [S] and demineralized [DEM]/cariogenic challenge by pH cycling prior to restorative procedures) and adhesive system (Scotchbond Universal Adhesive [SBU]) used in either etch-and-rinse (ER) or selfetching (SE) mode, with Clearfil SE Bond as the self-etching control. The adhesives were applied to flat enamel surfaces and composite cylinders (0.72 mm2) were built up. After 24-h storage in water, specimens were subjected to the microshear test. Bond strength (MPa) data were analyzed using two-way ANOVA and Tukey's post-hoc tests (α = 0.05). Significant differences were found considering the factors adhesive system (p = 0.003) and enamel condition (p = 0.001). Demineralized enamel negatively affected the bond strength, with μSBS values approximately 50% lower than those obtained for sound enamel. SBU performed better in etch-and-rinse mode, and the bond strength found for SBU applied in self-etching mode was similar to that of CSE. Enamel etching with phosphoric acid improves the bond strength of a universal adhesive system to primary enamel. Demineralized primary enamel results in lower bond strength.

RIE-based Pattern Transfer Using Nanoparticle Arrays as Etch Masks

NASA Astrophysics Data System (ADS)

Hogg, Chip; Majetich, Sara A.; Bain, James A.

2009-03-01

Nanomasking is used to transfer the pattern of a self-assembled array of nanoparticles into an underlying thin film, for potential use as bit-patterned media. We have used this process to investigate the limits of pattern transfer, as a function of gap size in the pattern. Reactive Ion Etching (RIE) is our chosen process, since the gaseous reaction products and high chemical selectivity are ideal features for etching very small gaps. Interstitial surfactant is removed with an O2 plasma, allowing the etchants to penetrate between the particles. Their pattern is transferred into an intermediate SiO2 mask using a CH4-based RIE. This patterned SiO2 layer is finally used as a mask for the MeOH-based RIE which patterns the magnetic film. We present cross-sectional TEM characterization of the etch profiles, as well as magnetic characterization of the film before and after patterning.

Observation of Biological Tissues Using Common Path Optical Coherence Tomography with Gold Coated Conical Tip Lens Fiber

NASA Astrophysics Data System (ADS)

Taguchi, K.; Sugiyama, J.; Totsuka, M.; Imanaka, S.

2012-03-01

In this paper, we proposed a high lateral resolution common-path Fourier domain optical coherence tomography(OCT) system with the use of a chemically etched single mode fiber. In our experiments, single mode optical fiber for 1310nm was used for preparing the tapered tips. Our system used a conical microlens that was chemically etched by selective chemical etching technique using an etching solution of buffered hydrofluoric acid (BHF). From experimental results, we verified that our proposed optical coherence tomography system could operate as a common-path Fourier domain OCT system and conical tip lens fiber was very useful for a high lateral resolution common-path Fourier domain OCT system. Furthermore, we could observe a surface of paramecium bursaria and symbiotic chlorella in the paramecium bursaria using gold coated conical-tip fiber in the water.

Evolution and characteristics of GaN nanowires produced via maskless reactive ion etching.

PubMed

Haab, Anna; Mikulics, Martin; Sutter, Eli; Jin, Jiehong; Stoica, Toma; Kardynal, Beata; Rieger, Torsten; Grützmacher, Detlev; Hardtdegen, Hilde

2014-06-27

The formation of nanowires (NWs) by reactive ion etching (RIE) of maskless GaN layers was investigated. The morphological, structural and optical characteristics of the NWs were studied and compared to those of the layer they evolve from. It is shown that the NWs are the result of a defect selective etching process. The evolution of density and length with etching time is discussed. Densely packed NWs with a length of more than 1 μm and a diameter of ∼60 nm were obtained by RIE of a ∼2.5 μm thick GaN layer. The NWs are predominantly free of threading dislocations and show an improvement of optical properties compared to their layer counterpart. The production of NWs via a top down process on non-masked group III-nitride layers is assessed to be very promising for photovoltaic applications.

Demonstration of an N7 integrated fab process for metal oxide EUV photoresist

NASA Astrophysics Data System (ADS)

De Simone, Danilo; Mao, Ming; Kocsis, Michael; De Schepper, Peter; Lazzarino, Frederic; Vandenberghe, Geert; Stowers, Jason; Meyers, Stephen; Clark, Benjamin L.; Grenville, Andrew; Luong, Vinh; Yamashita, Fumiko; Parnell, Doni

2016-03-01

Inpria has developed a directly patternable metal oxide hard-mask as a robust, high-resolution photoresist for EUV lithography. In this paper we demonstrate the full integration of a baseline Inpria resist into an imec N7 BEOL block mask process module. We examine in detail both the lithography and etch patterning results. By leveraging the high differential etch resistance of metal oxide photoresists, we explore opportunities for process simplification and cost reduction. We review the imaging results from the imec N7 block mask patterns and its process windows as well as routes to maximize the process latitude, underlayer integration, etch transfer, cross sections, etch equipment integration from cross metal contamination standpoint and selective resist strip process. Finally, initial results from a higher sensitivity Inpria resist are also reported. A dose to size of 19 mJ/cm2 was achieved to print pillars as small as 21nm.

Track-Etched Magnetic Micropores for Immunomagnetic Isolation of Pathogens

PubMed Central

Muluneh, Melaku; Shang, Wu

2014-01-01

A microfluidic chip is developed to selectively isolate magnetically tagged cells from heterogeneous suspensions, the track-etched magnetic micropore (TEMPO) filter. The TEMPO consists of an ion track-etched polycarbonate membrane coated with soft magnetic film (Ni20Fe80). In the presence of an applied field, provided by a small external magnet, the filter becomes magnetized and strong magnetic traps are created along the edges of the micropores. In contrast to conventional microfluidics, fluid flows vertically through the porous membrane allowing large flow rates while keeping the capture rate high and the chip compact. By utilizing track-etching instead of conventional semiconductor fabrication, TEMPOs can be fabricated with microscale pores over large areas A > 1 cm2 at little cost (< 5 ¢ cm−2). To demonstrate the utility of this platform, a TEMPO with 5 μm pore size is used to selectively and rapidly isolate immunomagnetically targeted Escherichia coli from heterogeneous suspensions, demonstrating enrichment of ζ > 500 at a flow rate of Φ = 5 mL h−1. Furthermore, the large density of micropores (ρ = 106 cm−2) allows the TEMPO to sort E. coli from unprocessed environmental and clinical samples, as the blockage of a few pores does not significantly change the behavior of the device. PMID:24535921

Compact Submillimeter-Wave Receivers Made with Semiconductor Nano-Fabrication Technologies

NASA Technical Reports Server (NTRS)

Jung, C.; Thomas, B.; Lee, C.; Peralta, A.; Chattopadhyay, G.; Gill, J.; Cooper, K.; Mehdi, I.

2011-01-01

Advanced semiconductor nanofabrication techniques are utilized to design, fabricate and demonstrate a super-compact, low-mass (<10 grams) submillimeter-wave heterodyne front-end. RF elements such as waveguides and channels are fabricated in a silicon wafer substrate using deep-reactive ion etching (DRIE). Etched patterns with sidewalls angles controlled with 1 deg precision are reported, while maintaining a surface roughness of better than 20 nm rms for the etched structures. This approach is being developed to build compact 2-D imaging arrays in the THz frequency range.

Fabrication of Meso-Porous Sintered Metal Thin Films by Selective Etching of Silica Based Sacrificial Template

PubMed Central

Dumée, Ludovic F.; She, Fenghua; Duke, Mikel; Gray, Stephen; Hodgson, Peter; Kong, Lingxue

2014-01-01

Meso-porous metal materials have enhanced surface energies offering unique surface properties with potential applications in chemical catalysis, molecular sensing and selective separation. In this paper, commercial 20 nm diameter metal nano-particles, including silver and copper were blended with 7 nm silica nano-particles by shear mixing. The resulted powders were cold-sintered to form dense, hybrid thin films. The sacrificial silica template was then removed by selective etching in 12 wt% hydrofluoric acid solutions for 15 min to reveal a purely metallic meso-porous thin film material. The impact of the initial silica nano-particle diameter (7–20 nm) as well as the sintering pressure (5–20 ton·m−2) and etching conditions on the morphology and properties of the final nano-porous thin films were investigated by porometry, pyknometery, gas and liquid permeation and electron microscopy. Furthermore, the morphology of the pores and particle aggregation during shear mixing were assessed through cross-sectioning by focus ion beam milling. It is demonstrated that meso-pores ranging between 50 and 320 nm in average diameter and porosities up to 47% can be successfully formed for the range of materials tested. PMID:28344241

Simulations of Control Schemes for Inductively Coupled Plasma Sources

NASA Astrophysics Data System (ADS)

Ventzek, P. L. G.; Oda, A.; Shon, J. W.; Vitello, P.

1997-10-01

Process control issues are becoming increasingly important in plasma etching. Numerical experiments are an excellent test-bench for evaluating a proposed control system. Models are generally reliable enough to provide information about controller robustness, fitness of diagnostics. We will present results from a two dimensional plasma transport code with a multi-species plasma chemstry obtained from a global model. [1-2] We will show a correlation of external etch parameters (e.g. input power) with internal plasma parameters (e.g. species fluxes) which in turn are correlated with etch results (etch rate, uniformity, and selectivity) either by comparison to experiment or by using a phenomenological etch model. After process characterization, a control scheme can be evaluated since the relationship between the variable to be controlled (e.g. uniformity) is related to the measurable variable (e.g. a density) and external parameter (e.g. coil current). We will present an evaluation using the HBr-Cl2 system as an example. [1] E. Meeks and J. W. Shon, IEEE Trans. on Plasma Sci., 23, 539, 1995. [2] P. Vitello, et al., IEEE Trans. on Plasma Sci., 24, 123, 1996.

Effect of etching parameters on antireflection properties of Si subwavelength grating structures for solar cell applications

NASA Astrophysics Data System (ADS)

Leem, J. W.; Song, Y. M.; Lee, Y. T.; Yu, J. S.

2010-09-01

Silicon (Si) subwavelength grating (SWG) structures were fabricated on Si substrates by holographic lithography and subsequent inductively coupled plasma (ICP) etching process using SiCl4 with or without Ar addition for solar cell applications. To ensure a good nanosized pattern transfer into the underlying Si layer, the etch selectivity of Si over the photoresist mask is optimized by varying the etching parameters, thus improving antireflection characteristics. For antireflection analysis of Si SWG surfaces, the optical reflectivity is measured experimentally and it is also calculated theoretically by a rigorous coupled-wave analysis. The reflectance depends on the height, period, and shape of two-dimensional periodic Si subwavelength structures, correlated with ICP etching parameters. The optimized Si SWG structure exhibits a dramatic decrease in optical reflection of the Si surface over a wide angle of incident light ( θ i ), i.e. less than 5% at wavelengths of 300-1100 nm, leading to good wide-angle antireflection characteristics (i.e. solar-weighted reflection of 1.7-4.9% at θ i <50°) of Si solar cells.

Localized etching of an insulator film coated on a copper wire using an atmospheric-pressure microplasma jet.

PubMed

Yoshiki, Hiroyuki

2007-04-01

Atmospheric-pressure microplasma jets (APmicroPJs) of Ar and ArO(2) gases were generated from the tip of a stainless steel surgical needle having outer and inner diameters of 0.4 and 0.2 mm, respectively, with a rf excitation of 13.56 MHz. The steel needle functions both as a powered electrode and a gas nozzle. The operating power is 1.2-6 W and the corresponding peak-to-peak voltage Vp.p. is about 1.5 kV. The APmicroPJ was applied to the localized etching of a polyamide-imide insulator film (thickness of 10 microm) of a copper winding wire of 90 microm diameter. The insulator film around the copper wire was completely removed by the irradiated plasma from a certain direction without fusing the wire. The removal time under the Ar APmicroPJ irradiation was only 3 s at a rf power of 4 W. Fluorescence microscopy and scanning electron microscope images reveal that good selectivity of the insulator film to the copper wire was achieved. In the case of ArO(2) APmicroPJ irradiation with an O(2) concentration of 10% or more, the removed copper surface was converted to copper monoxide CuO.

Preparation of multifunctional Al-Mg alloy surface with hierarchical micro/nanostructures by selective chemical etching processes

NASA Astrophysics Data System (ADS)

Shi, Tian; Kong, Jianyi; Wang, Xingdong; Li, Xuewu

2016-12-01

A superamphiphobic aluminum magnesium alloy surface with enhanced anticorrosion behavior has been prepared in this work via a simple and low-cost method. By successively polishing, etching and boiling treatments, the multifunctional hierarchical binary structures composed of the labyrinth-like concave-convex microstructures and twisty nanoflakes have been prepared. Results indicate that a superhydrophobic contact angle of 160.5° and superoleophobic contact angle larger than 150° as well as low adhesive property to liquids are achieved after such structures being modified with fluoroalkyl-silane. Furthermore, the anticorrosion behaviors in seawater of as-prepared samples are characterized by electrochemical tests including the impedance spectroscopies, equivalent circuits fittings and polarization curves. It is found that the hierarchical micro/nanostructures accompanying with the modified coating are proved to possess the maximal coating coverage rate of 90.0% larger than microstructures of 85.9%, nanostructures of 83.8% and bare polished surface of 67.1% suggesting the optimal anticorrosion. Finally, a great potential application in concentrators for surface-enhanced Raman scattering (SERS) analysis of toxic and pollutive ions on the superamphiphobic surface is also confirmed. This work has wider significance in extending further applications of alloys in engineering and environmental detecting fields.

Study on the performance of 2.6 μm In0.83Ga0.17As detector with different etch gases

NASA Astrophysics Data System (ADS)

Li, Ping; Tang, Hengjing; Li, Tao; Li, Xue; Shao, Xiumei; Ma, Yingjie; Gong, Haimei

2017-09-01

In order to obtain a low-damage recipe in the ICP processing, ICP-induced damage using Cl2/CH4 etch gases in extended wavelength In0.83Ga0.17As detector materials was studied in this paper. The effect of ICP etching on In0.83Ga0.17As samples was characterized qualitatively by the photoluminescence (PL) technology. The etch damage of In0.83Ga0.17As samples was characterized quantitatively by the Transmission Line Model (TLM), current voltage (IV) measurement, signal and noise testing and the Fourier Transform Infrared Spectroscopy (FTIR) technologies. The results showed that the Cl2/CH4 etching processing could lead better detector performance than that Cl2/N2, such as a larger square resistance, a lower dark current, a lower noise voltage and a higher peak detectivity. The lower PL signal intensity and lower dark current could be attributed to the hydrogen decomposed by the CH4 etch gases in the plasma etching process. These hydrogen particles generated non-radiative recombination centers in inner materials to weaken the PL intensity and passivated dangling bond at the surface to reduce the dark current. The larger square resistance resulted from the lower etch damage. The lower dark current meant that the detectors have less dangling bonds and leakage channels.

Polarization-Engineered Ga-Face GaN-Based Heterostructures for Normally-Off Heterostructure Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Kim, Hyeongnam; Nath, Digbijoy; Rajan, Siddharth; Lu, Wu

2013-01-01

Polarization-engineered Ga-face GaN-based heterostructures with a GaN cap layer and an AlGaN/ p-GaN back barrier have been designed for normally-off field-effect transistors (FETs). The simulation results show that an unintentionally doped GaN cap and p-GaN layer in the buffer primarily deplete electrons in the channel and the Al0.2Ga0.8N back barrier helps to pinch off the channel. Experimentally, we have demonstrated a normally-off GaN-based field-effect transistor on the designed GaN cap/Al0.3Ga0.7N/GaN channel/Al0.2Ga0.8N/ p-GaN/GaN heterostructure. A positive threshold voltage of 0.2 V and maximum transconductance of 2.6 mS/mm were achieved for 80- μm-long gate devices. The device fabrication process does not require a dry etching process for gate recessing, while highly selective etching of the GaN cap against a very thin Al0.3GaN0.7N top barrier has to be performed to create a two-dimensional electron gas for both the ohmic and access regions. A self-aligned, selective etch of the GaN cap in the access region is introduced, using the gate metal as an etch mask. The absence of gate recess etching is promising for uniform and repeatable threshold voltage control in normally-off AlGaN/GaN heterostructure FETs for power switching applications.

Shear Bond Strengths of Different Adhesive Systems to Biodentine

PubMed Central

Odabaş, Mesut Enes; Bani, Mehmet; Tirali, Resmiye Ebru

2013-01-01

The aim of this study was to measure the shear bond strength of different adhesive systems to Biodentine with different time intervals. Eighty specimens of Biodentine were prepared and divided into 8 groups. After 12 minutes, 40 samples were randomly selected and divided into 4 groups of 10 each: group 1: (etch-and-rinse adhesive system) Prime & Bond NT; group 2: (2-step self-etch adhesive system) Clearfil SE Bond; group 3: (1-step self-etch adhesive systems) Clearfil S3 Bond; group 4: control (no adhesive). After the application of adhesive systems, composite resin was applied over Biodentine. This procedure was repeated 24 hours after mixing additional 40 samples, respectively. Shear bond strengths were measured using a universal testing machine, and the data were subjected to 1-way analysis of variance and Scheffé post hoc test. No significant differences were found between all of the adhesive groups at the same time intervals (12 minutes and 24 hours) (P > .05). Among the two time intervals, the lowest value was obtained for group 1 (etch-and-rinse adhesive) at a 12-minute period, and the highest was obtained for group 2 (two-step self-etch adhesive) at a 24-hour period. The placement of composite resin used with self-etch adhesive systems over Biodentine showed better shear bond strength. PMID:24222742

Shear bond strengths of different adhesive systems to biodentine.

PubMed

Odabaş, Mesut Enes; Bani, Mehmet; Tirali, Resmiye Ebru

2013-01-01

The aim of this study was to measure the shear bond strength of different adhesive systems to Biodentine with different time intervals. Eighty specimens of Biodentine were prepared and divided into 8 groups. After 12 minutes, 40 samples were randomly selected and divided into 4 groups of 10 each: group 1: (etch-and-rinse adhesive system) Prime & Bond NT; group 2: (2-step self-etch adhesive system) Clearfil SE Bond; group 3: (1-step self-etch adhesive systems) Clearfil S(3) Bond; group 4: control (no adhesive). After the application of adhesive systems, composite resin was applied over Biodentine. This procedure was repeated 24 hours after mixing additional 40 samples, respectively. Shear bond strengths were measured using a universal testing machine, and the data were subjected to 1-way analysis of variance and Scheffé post hoc test. No significant differences were found between all of the adhesive groups at the same time intervals (12 minutes and 24 hours) (P > .05). Among the two time intervals, the lowest value was obtained for group 1 (etch-and-rinse adhesive) at a 12-minute period, and the highest was obtained for group 2 (two-step self-etch adhesive) at a 24-hour period. The placement of composite resin used with self-etch adhesive systems over Biodentine showed better shear bond strength.

Analysis of GaN Damage Induced by Cl2/SiCl4/Ar Plasma

NASA Astrophysics Data System (ADS)

Minami, Masaki; Tomiya, Shigetaka; Ishikawa, Kenji; Matsumoto, Ryosuke; Chen, Shang; Fukasawa, Masanaga; Uesawa, Fumikatsu; Sekine, Makoto; Hori, Masaru; Tatsumi, Tetsuya

2011-08-01

GaN-based optical devices are fabricated using a GaN/InGaN/GaN sandwiched structure. The effect of radicals, ions, and UV light on the GaN optical properties during Cl2/SiCl4/Ar plasma etching was evaluated using photoluminescence (PL) analysis. The samples were exposed to plasma (radicals, ions, and UV light) using an inductively coupled plasma (ICP) etching system and a plasma ion beam apparatus that can separate the effects of UV and ions both with and without covering the SiO2 window on the surface. Etching damage in an InGaN single quantum well (SQW) was formed by exposing the sample to plasma. The damage, which decreases PL emission intensity, was generated not only by ion beam irradiation but also by UV light irradiation. PL intensity decreased when the thickness of the upper GaN layer was etched to less than 60 nm. In addition, simultaneous irradiation of UV light and ions slightly increased the degree of damage. There seems to be a synergistic effect between the UV light and the ions. For high-quality GaN-based optoelectronics and power devices, UV light must be controlled during etching processes in addition to the etching profile, selectivity, and ion bombardment damage.

Sculpting Silica Colloids by Etching Particles with Nonuniform Compositions

PubMed Central

2017-01-01

We present the synthesis of new shapes of colloidal silica particles by manipulating their chemical composition and subsequent etching. Segments of silica rods, prepared by the ammonia catalyzed hydrolysis and condensation of tetraethylorthosilicate (TEOS) from polyvinylpyrrolidone loaded water droplets, were grown under different conditions. Upon decreasing temperature, delaying ethanol addition, or increasing monomer concentration, the rate of dissolution of the silica segment subsequently formed decreased. A watery solution of NaOH (∼mM) selectively etched these segments. Further tuning the conditions resulted in rod–cone or cone–cone shapes. Deliberately modulating the composition along the particle’s length by delayed addition of (3-aminopropyl)-triethoxysilane (APTES) also allowed us to change the composition stepwise. The faster etching of this coupling agent in neutral conditions or HF afforded an even larger variety of particle morphologies while in addition changing the chemical functionality. A comparable step in composition was applied to silica spheres. Biamine functional groups used in a similar way as APTES caused a charge inversion during the growth, causing dumbbells and higher order aggregates to form. These particles etched more slowly at the neck, resulting in a biconcave silica ring sandwiched between two silica spheres, which could be separated by specifically etching the functionalized layer using HF. PMID:28413261

Bonding of universal adhesives to dentine--Old wine in new bottles?

PubMed

Chen, C; Niu, L-N; Xie, H; Zhang, Z-Y; Zhou, L-Q; Jiao, K; Chen, J-H; Pashley, D H; Tay, F R

2015-05-01

Multi-mode universal adhesives offer clinicians the choice of using the etch-and-rinse technique, selective enamel etch technique or self-etch technique to bond to tooth substrates. The present study examined the short-term in vitro performance of five universal adhesives bonded to human coronal dentine. Two hundred non-carious human third molars were assigned to five groups based on the type of the universal adhesives (Prime&Bond Elect, Scotchbond Universal, All-Bond Universal, Clearfil Universal Bond and Futurabond U). Two bonding modes (etch-and-rinse and self-etch) were employed for each adhesive group. Bonded specimens were stored in deionized water for 24h or underwent a 10,000-cycle thermocycling ageing process prior to testing (N=10). Microtensile bond testing (μTBS), transmission electron microscopy (TEM) of resin-dentine interfaces in non-thermocycled specimens and scanning electron microscopy (SEM) of tracer-infused water-rich zones within hybrid layers of thermocycled specimens were performed. Both adhesive type and testing condition (with/without thermocycling) have significant influences on μTBS. The use of each adhesive in either the etch-and-rinse or self-etch application mode did not result in significantly different μTBS to dentine. Hybrid layers created by these adhesives in the etch-and-rinse bonding mode and self-etch bonding mode were ∼5μm and ≤0.5μm thick respectively. Tracer-infused regions could be identified within the resin-dentine interface from all the specimens prepared. The increase in versatility of universal adhesives is not accompanied by technological advances for overcoming the challenges associated with previous generations of adhesives. Therapeutic adhesives with bio-protective and bio-promoting effects are still lacking in commercialized adhesives. Universal adhesives represent manufacturers' attempt to introduce versatility in product design via adaptation of a single-bottle self-etch adhesive for other application modes without compromising its bonding effectiveness. Published by Elsevier Ltd.

Sidewall patterning—a new wafer-scale method for accurate patterning of vertical silicon structures

NASA Astrophysics Data System (ADS)

Westerik, P. J.; Vijselaar, W. J. C.; Berenschot, J. W.; Tas, N. R.; Huskens, J.; Gardeniers, J. G. E.

2018-01-01

For the definition of wafer scale micro- and nanostructures, in-plane geometry is usually controlled by optical lithography. However, options for precisely patterning structures in the out-of-plane direction are much more limited. In this paper we present a versatile self-aligned technique that allows for reproducible sub-micrometer resolution local modification along vertical silicon sidewalls. Instead of optical lithography, this method makes smart use of inclined ion beam etching to selectively etch the top parts of structures, and controlled retraction of a conformal layer to define a hard mask in the vertical direction. The top, bottom or middle part of a structure could be selectively exposed, and it was shown that these exposed regions can, for example, be selectively covered with a catalyst, doped, or structured further.

Selective CO2 Sequestration with Monolithic Bimodal Micro/Macroporous Carbon Aerogels Derived from Stepwise Pyrolytic Decomposition of Polyamide-Polyimide-Polyurea Random Copolymers.

PubMed

Saeed, Adnan M; Rewatkar, Parwani M; Majedi Far, Hojat; Taghvaee, Tahereh; Donthula, Suraj; Mandal, Chandana; Sotiriou-Leventis, Chariklia; Leventis, Nicholas

2017-04-19

Polymeric aerogels (PA-xx) were synthesized via room-temperature reaction of an aromatic triisocyanate (tris(4-isocyanatophenyl) methane) with pyromellitic acid. Using solid-state CPMAS 13 C and 15 N NMR, it was found that the skeletal framework of PA-xx was a statistical copolymer of polyamide, polyurea, polyimide, and of the primary condensation product of the two reactants, a carbamic-anhydride adduct. Stepwise pyrolytic decomposition of those components yielded carbon aerogels with both open and closed microporosity. The open micropore surface area increased from <15 m 2 g -1 in PA-xx to 340 m 2 g -1 in the carbons. Next, reactive etching at 1,000 °C with CO 2 opened access to the closed pores and the micropore area increased by almost 4× to 1150 m 2 g -1 (out of 1750 m 2 g -1 of a total BET surface area). At 0 °C, etched carbon aerogels demonstrated a good balance of adsorption capacity for CO 2 (up to 4.9 mmol g -1 ), and selectivity toward other gases (via Henry's law). The selectivity for CO 2 versus H 2 (up to 928:1) is suitable for precombustion fuel purification. Relevant to postcombustion CO 2 capture and sequestration (CCS), the selectivity for CO 2 versus N 2 was in the 17:1 to 31:1 range. In addition to typical factors involved in gas sorption (kinetic diameters, quadrupole moments and polarizabilities of the adsorbates), it is also suggested that CO 2 is preferentially engaged by surface pyridinic and pyridonic N on carbon (identified with XPS) in an energy-neutral surface reaction. Relatively high uptake of CH 4 (2.16 mmol g -1 at 0 °C/1 bar) was attributed to its low polarizability, and that finding paves the way for further studies on adsorption of higher (i.e., more polarizable) hydrocarbons. Overall, high CO 2 selectivities, in combination with attractive CO 2 adsorption capacities, low monomer cost, and the innate physicochemical stability of carbon render the materials of this study reasonable candidates for further practical consideration.

Selective Nanoscale Mass Transport across Atomically Thin Single Crystalline Graphene Membranes.

PubMed

Kidambi, Piran R; Boutilier, Michael S H; Wang, Luda; Jang, Doojoon; Kim, Jeehwan; Karnik, Rohit

2017-05-01

Atomically thin single crystals, without grain boundaries and associated defect clusters, represent ideal systems to study and understand intrinsic defects in materials, but probing them collectively over large area remains nontrivial. In this study, the authors probe nanoscale mass transport across large-area (≈0.2 cm 2 ) single-crystalline graphene membranes. A novel, polymer-free picture frame assisted technique, coupled with a stress-inducing nickel layer is used to transfer single crystalline graphene grown on silicon carbide substrates to flexible polycarbonate track etched supports with well-defined cylindrical ≈200 nm pores. Diffusion-driven flow shows selective transport of ≈0.66 nm hydrated K + and Cl - ions over ≈1 nm sized small molecules, indicating the presence of selective sub-nanometer to nanometer sized defects. This work presents a framework to test the barrier properties and intrinsic quality of atomically thin materials at the sub-nanometer to nanometer scale over technologically relevant large areas, and suggests the potential use of intrinsic defects in atomically thin materials for molecular separations or desalting. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Au/Si eutectic bonding compatibility with KOH etching for 3D devices fabrication

NASA Astrophysics Data System (ADS)

Liang, Hengmao; Liu, Mifeng; Liu, Song; Xu, Dehui; Xiong, Bin

2018-01-01

KOH etching and Au/Si eutectic bonding are cost-efficient technologies for 3D device fabrication. Aimed at investigating the process compatibility of KOH etching and Au/Si bonding, KOH etching tests have been carried out for Au/bulk Si and Au/amorphous Si (a-Si) bonding wafers in this paper. For the Au/bulk Si bonding wafer, a serious underetch phenomenon occurring on the damage layer in KOH etching definitely results in packaging failure. In the microstructure analysis, it is found that the formation of the damage layer between the bonded layer and bulk Si is attributed to the destruction of crystal Si lattices in Au/bulk Si eutectic reaction. Considering the occurrence of underetch for Au/Si bonding must meet two requirements: the superfluous Si and the defective layer near the bonded layer, the Au/a-Si bonding by regulating the a-Si/Au thickness ratio is presented in this study. Only when the a-Si/Au thickness ratio is relatively low are there not underetch phenomena, of which the reason is the full reaction of the a-Si layer avoiding the formation of the damage layer for easy underetch. Obviously, the Au/a-Si bonding via choosing a moderate a-Si/Au thickness ratio (⩽1.5:1 is suggested) could be reliably compatible with KOH etching, which provides an available and low-cost approach for 3D device fabrication. More importantly, the theory of the damage layer proposed in this study can be naturally applied to relevant analyses on the eutectic reaction of other metals and single crystal materials.

Effect of etching time and resin bond on the flexural strength of IPS e.max Press glass ceramic.

PubMed

Xiaoping, Luo; Dongfeng, Ren; Silikas, Nick

2014-12-01

To evaluate the effect of hydrofluoric acid (HFA) etching time and resin cement bond on the flexural strength of IPS e.max(®) Press glass ceramic. Two hundred and ten bars, 25mm×3mm×2mm, were made from IPS e.max(®) Press ingots through lost-wax, hot-pressed ceramic fabrication technology and randomly divided into five groups with forty-two per group after polishing. The ceramic surfaces of different groups were etched by 9.5% hydrofluoric acid gel for 0, 20, 40, 60 and 120s respectively. Two specimens of each group were selected randomly to examine the surface roughness and 3-dimensional topography with atomic force microscope (AFM), and microstructure was analyzed by the field emission scanning electron microscope (FE-SEM). Then each group were subdivided into two subgroups (n=20). One subgroup of this material was selected to receive a thin (approximately 0.1mm) layer of resin luting agent (Variolink N) whereas the other subgroup remained unaltered. Half of subgroup's specimens were thermocycled 10,000 times before a 3-point bending test in order to determine the flexural strength. Interface between resin cement and ceramic was examined with field emission scanning electronic microscope. Roughness values increased with increasing etching time. The mean flexural strength values of group 0s, 20s, 40s, 60s and 120s were 384±33, 347±43, 330±53, 327±67 and 317±41MPa respectively. Increasing HF etching times reduced the mean flexural strength (p<0.05). However, the mean flexural strength of each group, except group 0s, increased significantly to 420±31, 435±50, 400±39 and 412±58MPa after the application of dual-curing resin cement. In the present investigation, no significant differences after thermocycling on the flexural strengths were evident. Overtime HF etching could have a wakening effect on IPS e.max(®) Press glass ceramic, but resin cement bonding to appropriately etched surface would strengthen the dental ceramic. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Miniature all-silica optical fiber pressure sensor with an ultrathin uniform diaphragm.

PubMed

Wang, Wenhui; Wu, Nan; Tian, Ye; Niezrecki, Christopher; Wang, Xingwei

2010-04-26

This paper presents an all-silica miniature optical fiber pressure/acoustic sensor based on the Fabry-Perot (FP) interferometric principle. The endface of the etched optical fiber tip and silica thin diaphragm on it form the FP structure. The uniform and thin silica diaphragm was fabricated by etching away the silicon substrate from a commercial silicon wafer that has a thermal oxide layer. The thin film was directly thermally bonded to the endface of the optical fiber thus creating the Fabry-Perot cavity. Thin films with a thickness from 1microm to 3microm have been bonded successfully. The sensor shows good linearity and hysteresis during measurement. A sensor with 0.75 microm-thick diaphragm thinned by post silica etching was demonstrated to have a sensitivity of 11 nm/kPa. The new sensor has great potential to be used as a non-intrusive pressure sensor in a variety of sensing applications.

Optically Defined Multifunctional Patterning of Photosensitive Thin-Film Silica Mesophases

NASA Astrophysics Data System (ADS)

Doshi, Dhaval A.; Huesing, Nicola K.; Lu, Mengcheng; Fan, Hongyou; Lu, Yunfeng; Simmons-Potter, Kelly; Potter, B. G.; Hurd, Alan J.; Brinker, C. Jeffrey

2000-10-01

Photosensitive films incorporating molecular photoacid generators compartmentalized within a silica-surfactant mesophase were prepared by an evaporation-induced self-assembly process. Ultraviolet exposure promoted localized acid-catalyzed siloxane condensation, which can be used for selective etching of unexposed regions; for ``gray-scale'' patterning of refractive index, pore size, surface area, and wetting behavior; and for optically defining a mesophase transformation (from hexagonal to tetragonal) within the film. The ability to optically define and continuously control both structure and function on the macro- and mesoscales is of interest for sensor arrays, nanoreactors, photonic and fluidic devices, and low-dielectric-constant films.

Submilliampere continuous-wave room-temperature lasing operation of a GaAs mushroom structure surface-emitting laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y.J.; Dziura, T.G.; Wang, S.C.

1990-05-07

We report a GaAs mushroom structure surface-emitting laser at 900 nm with submilliampere (0.2--0.5 mA) threshold under room-temperature cw operation for the first time. The very low threshold current was achieved on devices which consisted of a 2--4 {mu}m diameter active region formed by chemical selective etching, and sandwiched between two Al{sub 0.05}Ga{sub 0.95} As/ Al{sub 0.53}Ga{sub 0.47} As distributed Bragg reflectors of very high reflectivity (98--99%) grown by metalorganic chemical vapor deposition.

Submilliampere continuous-wave room-temperature lasing operation of a GaAs mushroom structure surface-emitting laser

NASA Astrophysics Data System (ADS)

Yang, Ying Jay; Dziura, Thaddeus G.; Wang, S. C.; Hsin, Wei; Wang, Shyh

1990-05-01

We report a GaAs mushroom structure surface-emitting laser at 900 nm with submilliampere (0.2-0.5 mA) threshold under room-temperature cw operation for the first time. The very low threshold current was achieved on devices which consisted of a 2-4 μm diameter active region formed by chemical selective etching, and sandwiched between two Al0.05Ga0.95 As/ Al0.53Ga0.47 As distributed Bragg reflectors of very high reflectivity (98-99%) grown by metalorganic chemical vapor deposition.

Comparative Evaluation of the Etching Pattern of Er,Cr:YSGG & Acid Etching on Extracted Human Teeth-An ESEM Analysis

PubMed Central

Mazumdar, Dibyendu; Ranjan, Shashi; Krishna, Naveen Kumar; Kole, Ravindra; Singh, Priyankar; Lakiang, Deirimika; Jayam, Chiranjeevi

2016-01-01

Introduction Etching of enamel and dentin surfaces increases the surface area of the substrate for better bonding of the tooth colored restorative materials. Acid etching is the most commonly used method. Recently, hard tissue lasers have been used for this purpose. Aim The aim of the present study was to evaluate and compare the etching pattern of Er,Cr:YSGG and conventional etching on extracted human enamel and dentin specimens. Materials and Methods Total 40 extracted non-diseased teeth were selected, 20 anterior and 20 posterior teeth each for enamel and dentin specimens respectively. The sectioned samples were polished by 400 grit Silicon Carbide (SiC) paper to a thickness of 1.0 ± 0.5 mm. The enamel and dentin specimens were grouped as: GrE1 & GrD1 as control specimens, GrE2 & GrD2 were acid etched and GrE3 & GrD3 were lased. Acid etching was done using Conditioner 36 (37 % phosphoric acid) according to manufacturer instructions. Laser etching was done using Er,Cr:YSGG (Erbium, Chromium : Ytrium Scandium Gallium Garnet) at power settings of 3W, air 70% and water 20%. After surface treatment with assigned agents the specimens were analyzed under ESEM (Environmental Scanning Electron Microscope) at X1000 and X5000 magnification. Results Chi Square and Student “t” statistical analysis was used to compare smear layer removal and etching patterns between GrE2-GrE3. GrD2 and GrD3 were compared for smear layer removal and diameter of dentinal tubule opening using the same statistical analysis. Chi-square test for removal of smear layer in any of the treated surfaces i.e., GrE2-E3 and GrD2-D3 did not differ significantly (p>0.05). While GrE2 showed predominantly type I etching pattern (Chi-square=2.78, 0.05

0.10) and GrE3 showed type III etching (Chi-square=4.50, p<0.05). The tubule diameters were measured using GSA (Gesellschaft fur Softwareentwicklung und Analytik, Germany) image analyzer and the ‘t’ value of student ‘t’ test was 18.10 which was a highly significant result (p<.001). GrD2 had a mean dentinal tubule diameter of 2.78μm and GrD3 of 1.09μm. Conclusion The present study revealed type I etching pattern after acid etching, while type III etching pattern in enamel after laser etching. The lased dentin showed preferential removal of intertubular dentin while acid etching had more effect on the peritubular dentin. No significant differences was observed in removal of smear layer between the acid etched and lased groups. Although diameter of the exposed dentinal tubules was lesser after lased treatment in comparison to acid etching, further long term in vivo studies are needed with different parameters to establish the usage of Er,Cr:YSGG as a sole etching agent. PMID:27437337

Disilane-based cyclic deposition/etch of Si, Si:P and Si1-yCy:P layers: I. The elementary process steps

NASA Astrophysics Data System (ADS)

Hartmann, J. M.; Benevent, V.; Barnes, J. P.; Veillerot, M.; Deguet, C.

2013-02-01

We have benchmarked the 550 °C, 20 Torr growth of Si:P and Si1-yCy:P using SiH4 and Si2H6. P segregation has prevented us from reaching P+ ion concentrations in Si higher than a few 1019 cm-3 using SiH4; the resulting surface ‘poisoning’ led to a severe growth rate reduction. Meanwhile, [P+] increased linearly with the phosphine flow when using Si2H6 as the Si precursor; values as high as 1.7 × 1020 cm-3 were obtained. The Si:P growth rate using Si2H6 was initially stable then increased as the PH3 flow increased. Mono-methylsilane flows 6.5-10 times higher were needed with Si2H6 than with SiH4 to reach the same substitutional C concentrations in intrinsic Si1-yCy layers ([C]subst. up to 1.9%). Growth rates were approximately six times higher with Si2H6 than with SiH4, however. 30 nm thick Si1-yCy layers became rough as [C]subst. exceeded 1.6% (formation of increasing numbers of islands). We have also studied the structural and electrical properties of ‘low’ and ‘high’ C content Si1-yCy:P layers (˜ 1.5 and 1.8%, respectively) grown with Si2H6. Adding significant amounts of PH3 led to a reduction of the tensile strain in the films. This was due to the incorporation of P atoms (at the expense of C atoms) in the substitutional sites of the Si matrix. Si1-yCy:P layers otherwise became rough as the PH3 flow increased. Resistivities lower than 1 mΩ cm were nevertheless associated with those Si1-yCy:P layers, with P atomic concentrations at most 3.9 × 1020 cm-3. Finally, we have quantified the beneficial impact of adding GeH4 to HCl for the low-temperature etching of Si. Etch rates 12-36 times higher with HCl + GeH4 than with pure HCl were achieved at 20 Torr. Workable etch rates close to 1 nm min-1 were obtained at 600 °C (versus 750 °C for pure HCl), enabling low-temperature cyclic deposition/etch strategies for the selective epitaxial growth of Si, Si:P and Si1-yCy:P layers on patterned wafers.

DENSITY-DEPENDENT EVOLUTION OF LIFE-HISTORY TRAITS IN DROSOPHILA MELANOGASTER.

PubMed

Bierbaum, Todd J; Mueller, Laurence D; Ayala, Francisco J

1989-03-01

Populations of Drosophila melanogaster were maintained for 36 generations in r- and K-selected environments in order to test the life-history predictions of theories on density-dependent selection. In the r-selection environment, populations were reduced to low densities by density-independent adult mortality, whereas populations in the K-selection environment were maintained at their carrying capacity. Some of the experimental results support the predictions or r- and K-selection theory; relative to the r-selected populations, the K-selected populations evolved an increased larval-to-adult viability, larger body size, and longer development time at high larval densities. Mueller and Ayala (1981) found that K-selected populations also have a higher rate of population growth at high densities. Other predictions of the thoery are contradicted by the lack of differences between the r and K populations in adult longevity and fecundity and a slower rate of development for r-selected individuals at low densities. The differences between selected populations in larval survivorship, larval-to-adult development time, and adult body size are strongly dependent on larval density, and there is a significant interaction between populations and larval density for each trait. This manifests an inadequacy of the theory on r- and K-selection, which does not take into account such interactions between genotypes and environments. We describe mechanisms that may explain the evolution of preadult life-history traits in our experiment and discuss the need for changes in theories of density-dependent selection. © 1989 The Society for the Study of Evolution.

Innovative ceramic slab lasers for high power laser applications

NASA Astrophysics Data System (ADS)

Lapucci, Antonio; Ciofini, Marco

2005-09-01

Diode Pumped Solid State Lasers (DPSSL) are gaining increasing interest for high power industrial application, given the continuous improvement in high power diode laser technology reliability and affordability. These sources open new windows in the parameter space for traditional applications such as cutting , welding, marking and engraving for high reflectance metallic materials. Other interesting applications for this kind of sources include high speed thermal printing, precision drilling, selective soldering and thin film etching. In this paper we examine the most important DPSS laser source types for industrial applications and we describe in details the performances of some slab laser configurations investigated at our facilities. The different architectures' advantages and draw-backs are briefly compared in terms of performances, system complexity and ease of scalability to the multi-kW level.

Fabrication and characterization of active nanostructures

NASA Astrophysics Data System (ADS)

Opondo, Noah F.

Three different nanostructure active devices have been designed, fabricated and characterized. Junctionless transistors based on highly-doped silicon nanowires fabricated using a bottom-up fabrication approach are first discussed. The fabrication avoids the ion implantation step since silicon nanowires are doped in-situ during growth. Germanium junctionless transistors fabricated with a top down approach starting from a germanium on insulator substrate and using a gate stack of high-k dielectrics and GeO2 are also presented. The levels and origin of low-frequency noise in junctionless transistor devices fabricated from silicon nanowires and also from GeOI devices are reported. Low-frequency noise is an indicator of the quality of the material, hence its characterization can reveal the quality and perhaps reliability of fabricated transistors. A novel method based on low-frequency noise measurement to envisage trap density in the semiconductor bandgap near the semiconductor/oxide interface of nanoscale silicon junctionless transistors (JLTs) is presented. Low-frequency noise characterization of JLTs biased in saturation is conducted at different gate biases. The noise spectrum indicates either a Lorentzian or 1/f. A simple analysis of the low-frequency noise data leads to the density of traps and their energy within the semiconductor bandgap. The level of noise in silicon JLT devices is lower than reported values on transistors fabricated using a top-down approach. This noise level can be significantly improved by improving the quality of dielectric and the channel interface. A micro-vacuum electron device based on silicon field emitters for cold cathode emission is also presented. The presented work utilizes vertical Si nanowires fabricated by means of self-assembly, standard lithography and etching techniques as field emitters in this dissertation. To obtain a high nanowire density, hence a high current density, a simple and inexpensive Langmuir Blodgett technique to deposit silica nanoparticles as a mask to etch Si is adopted. Fabrication and characterization of a metal-gated microtriode with a high current density and low operating voltage are presented.

An investigation into the suitability of some etching reagents to restoring obliterated stamped numbers on cast iron engine blocks of cars.

PubMed

Abdul Wahab, Mohd Farizon; Mohamad Ghani, Nurul Izwani; Kuppuswamy, R

2012-11-30

Most of the automotive companies use cast iron for their engine blocks. Restoration of obliterated number on these iron surfaces by chemical etching is known to be quite difficult. Heating of the obliterated surface using oxyacetylene flame is an alternative recovery treatment suggested in literature and used in practice. However chemical etching has been established to be the most sensitive technique for detection of metal deformation present under stamped serial numbers. Hence, the current work investigated the suitability of some common etchants on cast iron surfaces with a view to determining the most suitable one for revealing the obliterated marks. The reagents tested were mostly copper containing Fry's reagent and its modifications. Two cast iron engine blocks (3.29%C and 3.1%C) of two cars--a Proton Saga and a Toyota--were utilized for the experiments. The engine blocks were cut into several small plates and each plate was stamped with some numerical characters at 8 kN load using Instron Table Mounted Universal Testing Machine. The depth of stamping impression varied between 0.2 mm and 0.3 mm. The stamped number was completely ground off manually using a metal file. The grounded surface was then polished smooth using emery papers and etched with a few selected reagents mostly by swabbing. Experimental results showed that a modified Fry's composition consisting of 4 5g CuCl(2), 100 mL HCl, and 180 mL H(2)O restored the number with better contrast at a reasonably shorter time. The above reagent is a slightly modified form of one of the Fry's original compositions--45 g CuCl(2), 180 mL HCl, and 100 mL H(2)O. Quite importantly the proposed reagent restored the original stamped numbers of both Proton and Toyota cars and also a Mitsubishi car that had been obliterated. The most widely used Fry's composition (90 g CuCl(2), 120 mL HCl and 100 mL H(2)O), although recovered the obliterated number, did not cause the desired contrast. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Tip-Based Nanofabrication of Arbitrary Shapes of Graphene Nanoribbons for Device Applications

PubMed Central

Estrada, David; Bashir, Rashid; King, William P.

2015-01-01

Graphene nanoribbons (GNRs) have promising applications in future nanoelectronics, chemical sensing and electrical interconnects. Although there are quite a few GNR nanofabrication methods reported, a rapid and low-cost fabrication method that is capable of fabricating arbitrary shapes of GNRs with good-quality is still in demand for using GNRs for device applications. In this paper, we present a tip-based nanofabrication method capable of fabricating arbitrary shapes of GNRs. A heated atomic force microscope (AFM) tip deposits polymer nanowires atop a CVD-grown graphene surface. The polymer nanowires serve as an etch mask to define GNRs through one step of oxygen plasma etching similar to a photoresist in conventional photolithography. Various shapes of GNRs with either linear or curvilinear features are demonstrated. The width of the GNR is around 270 nm and is determined by the width of the depositing polymer nanowire, which we estimate can be scaled down 15 nms. We characterize our TBN-fabricated GNRs using Raman spectroscopy and I-V measurements. The measured sheet resistances of our GNRs fall within the range of 1.65 kΩ/□−1 – 2.64 kΩ/□−1, in agreement with previously reported values. Furthermore, we determined the high-field breakdown current density of GNRs to be approximately 2.94×108 A/cm2. This TBN process is seamlessly compatible with existing nanofabrication processes, and is particularly suitable for fabricating GNR based electronic devices including next generation DNA sequencing technologies and beyond silicon field effect transistors. PMID:26257891

Stability of field emission current from porous n-GaAs(110)

NASA Astrophysics Data System (ADS)

Tondare, V. N.; Naddaf, M.; Bhise, A. B.; Bhoraskar, S. V.; Joag, D. S.; Mandale, A. B.; Sainkar, S. R.

2002-02-01

Field electron emission from porous GaAs has been investigated. The emitter was prepared by anodic etching of n-GaAs (110) in 0.1 M HCl solution. The as-etched porous GaAs shows nonlinear Fowler-Nordheim (FN) characteristics, with a low onset voltage. The emitter, after operating for 6 h at the residual gas pressure of 1×10-8 mbar, shows a linear FN characteristics with a relatively high onset voltage and poor field emission current stability as compared to the as-etched emitter. The change in the behavior was attributed to the residual gas ion bombardment during field electron emission. X-ray photoelectron spectroscopic investigations were carried out on as-etched sample and the one which was studied for field emission. The studies indicate that the as-etched surface contains As2O3 and the surface after field electron emission for about 6 h becomes gallium rich. The presence of As2O3 seems to be a desirable feature for the stable field emission current.

Photoelectrochemical etching of epitaxial InGaN thin films: Self-limited kinetics and nanostructuring

DOE PAGES

Xiao, Xiaoyin; Fischer, Arthur J.; Coltrin, Michael E.; ...

2014-10-22

We report here the characteristics of photoelectrochemical (PEC) etching of epitaxial InGaN semiconductor thin films using narrowband lasers with linewidth less than ~1 nm. In the initial stages of PEC etching, when the thin film is flat, characteristic voltammogram shapes are observed. At low photo-excitation rates, voltammograms are S-shaped, indicating the onset of a voltage-independent rate-limiting process associated with electron-hole-pair creation and/or annihilation. At high photo-excitation rates, voltammograms are superlinear in shape, indicating, for the voltage ranges studied here, a voltage-dependent rate-limiting process associated with surface electrochemical oxidation. As PEC etching proceeds, the thin film becomes rough at the nanoscale,more » and ultimately evolves into an ensemble of nanoparticles. As a result, this change in InGaN film volume and morphology leads to a characteristic dependence of PEC etch rate on time: an incubation time, followed by a rise, then a peak, then a slow decay.« less

Wet etch methods for InAs nanowire patterning and self-aligned electrical contacts

NASA Astrophysics Data System (ADS)

Fülöp, G.; d'Hollosy, S.; Hofstetter, L.; Baumgartner, A.; Nygård, J.; Schönenberger, C.; Csonka, S.

2016-05-01

Advanced synthesis of semiconductor nanowires (NWs) enables their application in diverse fields, notably in chemical and electrical sensing, photovoltaics, or quantum electronic devices. In particular, indium arsenide (InAs) NWs are an ideal platform for quantum devices, e.g. they may host topological Majorana states. While the synthesis has been continously perfected, only a few techniques have been developed to tailor individual NWs after growth. Here we present three wet chemical etch methods for the post-growth morphological engineering of InAs NWs on the sub-100 nm scale. The first two methods allow the formation of self-aligned electrical contacts to etched NWs, while the third method results in conical shaped NW profiles ideal for creating smooth electrical potential gradients and shallow barriers. Low temperature experiments show that NWs with etched segments have stable transport characteristics and can serve as building blocks of quantum electronic devices. As an example we report the formation of a single electrically stable quantum dot between two etched NW segments.

Three-dimensional photonic crystals created by single-step multi-directional plasma etching.

PubMed

Suzuki, Katsuyoshi; Kitano, Keisuke; Ishizaki, Kenji; Noda, Susumu

2014-07-14

We fabricate 3D photonic nanostructures by simultaneous multi-directional plasma etching. This simple and flexible method is enabled by controlling the ion-sheath in reactive-ion-etching equipment. We realize 3D photonic crystals on single-crystalline silicon wafers and show high reflectance (>95%) and low transmittance (<-15dB) at optical communication wavelengths, suggesting the formation of a complete photonic bandgap. Moreover, our method simply demonstrates Si-based 3D photonic crystals that show the photonic bandgap effect in a shorter wavelength range around 0.6 μm, where further fine structures are required.

Ultra-Sensitive Magnetoresistive Displacement Sensing Device

NASA Technical Reports Server (NTRS)

Olivas, John D. (Inventor); Lairson, Bruce M. (Inventor); Ramesham, Rajeshuni (Inventor)

2003-01-01

An ultrasensitive displacement sensing device for use in accelerometers, pressure gauges, temperature transducers, and the like, comprises a sputter deposited, multilayer, magnetoresistive field sensor with a variable electrical resistance based on an imposed magnetic field. The device detects displacement by sensing changes in the local magnetic field about the magnetoresistive field sensor caused by the displacement of a hard magnetic film on a movable microstructure. The microstructure, which may be a cantilever, membrane, bridge, or other microelement, moves under the influence of an acceleration a known displacement predicted by the configuration and materials selected, and the resulting change in the electrical resistance of the MR sensor can be used to calculate the displacement. Using a micromachining approach, very thin silicon and silicon nitride membranes are fabricated in one preferred embodiment by means of anisotropic etching of silicon wafers. Other approaches include reactive ion etching of silicon on insulator (SOI), or Low Pressure Chemical Vapor Deposition of silicon nitride films over silicon substrates. The device is found to be improved with the use of giant magnetoresistive elements to detect changes in the local magnetic field.

Growth and dislocation studies of β-HMX.

PubMed

Gallagher, Hugh G; Sherwood, John N; Vrcelj, Ranko M

2014-01-01

The defect structure of organic materials is important as it plays a major role in their crystal growth properties. It also can play a subcritical role in "hot-spot" detonation processes of energetics and one such energetic is cyclotetramethylene-tetranitramine, in the commonly used beta form (β-HMX). The as-grown crystals grown by evaporation from acetone show prismatic, tabular and columnar habits, all with {011}, {110}, (010) and (101) faces. Etching on (010) surfaces revealed three different types of etch pits, two of which could be identified with either pure screw or pure edge dislocations, the third is shown to be an artifact of the twinning process that this material undergoes. Examination of the {011} and {110} surfaces show only one type of etch pit on each surface; however their natural asymmetry precludes the easy identification of their Burgers vector or dislocation type. Etching of cleaved {011} surfaces demonstrates that the etch pits can be associated with line dislocations. All dislocations appear randomly on the crystal surfaces and do not form alignments characteristic of mechanical deformation by dislocation slip. Crystals of β-HMX grown from acetone show good morphological agreement with that predicted by modelling, with three distinct crystal habits observed depending upon the supersaturation of the growth solution. Prismatic habit was favoured at low supersaturation, while tabular and columnar crystals were predominant at higher super saturations. The twin plane in β-HMX was identified as a (101) reflection plane. The low plasticity of β-HMX is shown by the lack of etch pit alignments corresponding to mechanically induced dislocation arrays. On untwinned {010} faces, two types of dislocations exist, pure edge dislocations with b = [010] and pure screw dislocations with b = [010]. On twinned (010) faces, a third dislocation type exists and it is proposed that these pits are associated with pure screw dislocations with b = [010]. Graphical abstractEtch pits on the twinned (010) face of β-HMX.

Development of optimized, graded-permeability axial groove heat pipes

NASA Technical Reports Server (NTRS)

Kapolnek, Michael R.; Holmes, H. Rolland

1988-01-01

Heat pipe performance can usually be improved by uniformly varying or grading wick permeability from end to end. A unique and cost effective method for grading the permeability of an axial groove heat pipe is described - selective chemical etching of the pipe casing. This method was developed and demonstrated on a proof-of-concept test article. The process improved the test article's performance by 50 percent. Further improvement is possible through the use of optimally etched grooves.

Increased Multilayer Fabrication and RF Characterization of a High-Density Stacked MIM Capacitor Based on Selective Etching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tseng, VFG; Xie, HK

2014-07-01

This paper presents the fabrication and characterization of a high-density multilayer stacked metal-insulator-metal (MIM) capacitor based on a novel process of depositing the MIM multilayer on pillars followed by polishing and selective etching steps to form a stacked capacitor with merely three photolithography steps. In this paper, the pillars were made of glass to prevent substrate loss, whereas an oxide-nitride-oxide dielectric was employed for lower leakage, better voltage/frequency linearity, and better stress compensation. MIM capacitors with six dielectric layers were successfully fabricated, yielding capacitance density of 3.8 fF/mu m(2), maximum capacitance of 2.47 nF, and linear and quadratic voltage coefficientsmore » of capacitance below 21.2 ppm/V and 2.31 ppm/V-2. The impedance was measured from 40 Hz to 3 GHz, and characterized by an analytically derived equivalent circuit model to verify the radio frequency applicability. The multilayer stacking-induced plate resistance mismatch and its effect on the equivalent series resistance (ESR) and effective capacitance was also investigated, which can be counteracted by a corrected metal thickness design. A low ESR of 800 m Omega was achieved, whereas the self-resonance frequency was >760 MHz, successfully demonstrating the feasibility of this method to scale up capacitance densities for high-quality-factor, high-frequency, and large-value MIM capacitors.« less

EUV patterning using CAR or MOX photoresist at low dose exposure for sub 36nm pitch

NASA Astrophysics Data System (ADS)

Thibaut, Sophie; Raley, Angélique; Lazarrino, Frederic; Mao, Ming; De Simone, Danilo; Piumi, Daniele; Barla, Kathy; Ko, Akiteru; Metz, Andrew; Kumar, Kaushik; Biolsi, Peter

2018-04-01

The semiconductor industry has been pushing the limits of scalability by combining 193nm immersion lithography with multi-patterning techniques for several years. Those integrations have been declined in a wide variety of options to lower their cost but retain their inherent variability and process complexity. EUV lithography offers a much desired path that allows for direct print of line and space at 36nm pitch and below and effectively addresses issues like cycle time, intra-level overlay and mask count costs associated with multi-patterning. However it also brings its own sets of challenges. One of the major barrier to high volume manufacturing implementation has been hitting the 250W power exposure required for adequate throughput [1]. Enabling patterning using a lower dose resist could help move us closer to the HVM throughput targets assuming required performance for roughness and pattern transfer can be met. As plasma etching is known to reduce line edge roughness on 193nm lithography printed features [2], we investigate in this paper the level of roughness that can be achieved on EUV photoresist exposed at a lower dose through etch process optimization into a typical back end of line film stack. We will study 16nm lines printed at 32 and 34nm pitch. MOX and CAR photoresist performance will be compared. We will review step by step etch chemistry development to reach adequate selectivity and roughness reduction to successfully pattern the target layer.

Ion beam figuring of CVD silicon carbide mirrors

NASA Astrophysics Data System (ADS)

Gailly, P.; Collette, J.-P.; Fleury Frenette, K.; Jamar, C.

2017-11-01

Optical and structural elements made of silicon carbide are increasingly found in space instruments. Chemical vapor deposited silicon carbide (CVD-SiC) is used as a reflective coating on SiC optics in reason of its good behavior under polishing. The advantage of applying ion beam figuring (IBF) to CVD-SiC over other surface figure-improving techniques is discussed herein. The results of an IBF sequence performed at the Centre Spatial de Liège on a 100 mm CVD-SiC mirror are reported. The process allowed to reduce the mirror surface errors from 243 nm to 13 nm rms . Beside the surface figure, roughness is another critical feature to consider in order to preserve the optical quality of CVD-SiC . Thus, experiments focusing on the evolution of roughness were performed in various ion beam etching conditions. The roughness of samples etched at different depths down to 3 ≠m was determined with an optical profilometer. These measurements emphasize the importance of selecting the right combination of gas and beam energy to keep roughness at a low level. Kaufman-type ion sources are generally used to perform IBF but the performance of an end-Hall ion source in figuring CVD-SiC mirrors was also evaluated in this study. In order to do so, ion beam etching profiles obtained with the end-Hall source on CVD-SiC were measured and used as a basis for IBF simulations.

A Compact Via-free Composite Right/Left Handed Low-pass Filter with Improved Selectivity

NASA Astrophysics Data System (ADS)

Kumar, Ashish; Choudhary, Dilip Kumar; Chaudhary, Raghvendra Kumar

2017-07-01

In this paper, a compact via-free low pass filter is designed based on composite right/left handed (CRLH) concept. The structure uses open ended concept. Rectangular slots are etched on signal transmission line (TL) to suppress the spurious band without altering the performance and size of filter. The filter is designed for low pass frequency band with cut-off frequency of 3.5 GHz. The proposed metamaterial structure has several prominent advantages in term of selectivity up to 34 dB/GHz and compactness with average insertion loss less than 0.4 dB. It has multiple applications in wireless communication (such as GSM900, global navigation satellite system (1.559-1.610 GHz), GSM1800, WLAN/WiFi (2.4-2.49 GHz) and WiMAX (2.5-2.69 GHz)). The design parameters have been measured and compared with the simulated results and found excellent agreement. The electrical size of proposed filter is 0.14λ0× 0.11λ0 (where λ0 is free space wavelength at zeroth order resonance (ZOR) frequency 2.7 GHz).

A practical double-sided frequency selective surface for millimeter-wave applications

NASA Astrophysics Data System (ADS)

Mohyuddin, Wahab; Woo, Dong Sik; Choi, Hyun Chul; Kim, Kang Wook

2018-02-01

Analysis, design, and implementation of a practical, high-rejection frequency selective surface (FSS) are presented in this paper. An equivalent circuit model is introduced for predicting the frequency response of the FSS. The FSS consists of periodic square loop structures fabricated on both sides of the thin dielectric substrate by using the low-cost chemical etching technique. The proposed FSS possesses band-stop characteristics and is implemented to suppress the 170 GHz signal with attenuation of more than 45 dB with insensitivity to an angle of incident plane wave over 20°. Good agreement is observed among calculated, simulated, and measured results. The proposed FSS filter can be used in various millimeter-wave applications such as the protection of imaging diagnostic systems from high spurious input power.

Controlled, prospective, randomized, clinical split-mouth evaluation of partial ceramic crowns luted with a new, universal adhesive system/resin cement: results after 18 months.

PubMed

Vogl, Vanessa; Hiller, Karl-Anton; Buchalla, Wolfgang; Federlin, Marianne; Schmalz, Gottfried

2016-12-01

A new universal adhesive with corresponding luting composite was recently marketed which can be used both, in a self-etch or in an etch-and-rinse mode. In this study, the clinical performance of partial ceramic crowns (PCCs) inserted with this adhesive and the corresponding luting material used in a self-etch or selective etch approach was compared with a self-adhesive universal luting material. Three PCCs were placed in a split-mouth design in 50 patients. Two PCCs were luted with a combination of a universal adhesive/resin cement (Scotchbond Universal/RelyX Ultimate, 3M ESPE) with (SB+E)/without (SB-E) selective enamel etching. Another PCC was luted with a self-adhesive resin cement (RelyX Unicem 2, 3M ESPE). Forty-eight patients were evaluated clinically according to FDI criteria at baseline and 6, 12 and 18 months. For statistical analyses, the chi-square test (α = 0.05) and Kaplan-Meier analysis were applied. Clinically, no statistically significant differences between groups were detected over time. Within groups, clinically significant increase for criterion "marginal staining" was detected for SB-E over 18 months. Kaplan-Meier analysis revealed significantly higher retention rates for SB+E (97.8 %) and SB-E (95.6 %) in comparison to RXU2 (75.6 %). The 18-month clinical performance of a new universal adhesive/composite combination showed no differences with respect to bonding strategy and may be recommended for luting PCCs. Longer-term evaluation is needed to confirm superiority of SB+E over SB-E. At 18 months, the new multi-mode adhesive, Scotchbond Universal, showed clinically reliable results when used for luting PCCs.

In vivo cation exchange in quantum dots for tumor-specific imaging.

PubMed

Liu, Xiangyou; Braun, Gary B; Qin, Mingde; Ruoslahti, Erkki; Sugahara, Kazuki N

2017-08-24

In vivo tumor imaging with nanoprobes suffers from poor tumor specificity. Here, we introduce a nanosystem, which allows selective background quenching to gain exceptionally tumor-specific signals. The system uses near-infrared quantum dots and a membrane-impermeable etchant, which serves as a cation donor. The etchant rapidly quenches the quantum dots through cation exchange (ionic etching), and facilitates renal clearance of metal ions released from the quantum dots. The quantum dots are intravenously delivered into orthotopic breast and pancreas tumors in mice by using the tumor-penetrating iRGD peptide. Subsequent etching quenches excess quantum dots, leaving a highly tumor-specific signal provided by the intact quantum dots remaining in the extravascular tumor cells and fibroblasts. No toxicity is noted. The system also facilitates the detection of peritoneal tumors with high specificity upon intraperitoneal tumor targeting and selective etching of excess untargeted quantum dots. In vivo cation exchange may be a promising strategy to enhance specificity of tumor imaging.The imaging of tumors in vivo using nanoprobes has been challenging due to the lack of sufficient tumor specificity. Here, the authors develop a tumor-specific quantum dot system that permits in vivo cation exchange to achieve selective background quenching and high tumor-specific imaging.

40 CFR 61.31 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... associated elements. (b) Extraction plant means a facility chemically processing beryllium ore to beryllium..., electrochemical machining, etching, or other similar operations. (e) Ceramic plant means a manufacturing plant... which contains more than 0.1 percent beryllium by weight. (k) Propellant plant means any facility...

40 CFR 61.31 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... associated elements. (b) Extraction plant means a facility chemically processing beryllium ore to beryllium..., electrochemical machining, etching, or other similar operations. (e) Ceramic plant means a manufacturing plant... which contains more than 0.1 percent beryllium by weight. (k) Propellant plant means any facility...

Surface morphology evolution during plasma etching of silicon: roughening, smoothing and ripple formation

NASA Astrophysics Data System (ADS)

Ono, Kouichi; Nakazaki, Nobuya; Tsuda, Hirotaka; Takao, Yoshinori; Eriguchi, Koji

2017-10-01

Atomic- or nanometer-scale roughness on feature surfaces has become an important issue to be resolved in the fabrication of nanoscale devices in industry. Moreover, in some cases, smoothing of initially rough surfaces is required for planarization of film surfaces, and controlled surface roughening is required for maskless fabrication of organized nanostructures on surfaces. An understanding, under what conditions plasma etching results in surface roughening and/or smoothing and what are the mechanisms concerned, is of great technological as well as fundamental interest. In this article, we review recent developments in the experimental and numerical study of the formation and evolution of surface roughness (or surface morphology evolution such as roughening, smoothing, and ripple formation) during plasma etching of Si, with emphasis being placed on a deeper understanding of the mechanisms or plasma-surface interactions that are responsible for. Starting with an overview of the experimental and theoretical/numerical aspects concerned, selected relevant mechanisms are illustrated and discussed primarily on the basis of systematic/mechanistic studies of Si etching in Cl-based plasmas, including noise (or stochastic roughening), geometrical shadowing, surface reemission of etchants, micromasking by etch inhibitors, and ion scattering/chanelling. A comparison of experiments (etching and plasma diagnostics) and numerical simulations (Monte Carlo and classical molecular dynamics) indicates a crucial role of the ion scattering or reflection from microscopically roughened feature surfaces on incidence in the evolution of surface roughness (and ripples) during plasma etching; in effect, the smoothing/non-roughening condition is characterized by reduced effects of the ion reflection, and the roughening-smoothing transition results from reduced ion reflections caused by a change in the predominant ion flux due to that in plasma conditions. Smoothing of initially rough surfaces as well as non-roughening of initially planar surfaces during etching (normal ion incidence) and formation of surface ripples by plasma etching (off-normal ion incidence) are also presented and discussed in this context.

Self-assembly and continuous growth of hexagonal graphene flakes on liquid Cu

NASA Astrophysics Data System (ADS)

Cho, Seong-Yong; Kim, Min-Sik; Kim, Minsu; Kim, Ki-Ju; Kim, Hyun-Mi; Lee, Do-Joong; Lee, Sang-Hoon; Kim, Ki-Bum

2015-07-01

Graphene growth on liquid Cu has received great interest, owing to the self-assembly behavior of hexagonal graphene flakes with aligned orientation and to the possibility of forming a single grain of graphene through a commensurate growth of these graphene flakes. Here, we propose and demonstrate a two-step growth process which allows the formation of self-assembled, completely continuous graphene on liquid Cu. After the formation of full coverage on the liquid Cu, grain boundaries were revealed via selective hydrogen etching and the original grain boundaries were clearly resolved. This result indicates that, while the flakes self-assembled with the same orientation, there still remain structural defects, gaps and voids that were not resolved by optical microscopy or scanning electron microscopy. To overcome this limitation, the two-step growth process was employed, consisting of a sequential process of a normal single-layer graphene growth and self-assembly process with a low carbon flux, followed by the final stage of graphene growth at a high degree of supersaturation with a high carbon flux. Continuity of the flakes was verified via hydrogen etching and a NaCl-assisted oxidation process, as well as by measuring the electrical properties of the graphene grown by the two-step process. Two-step growth can provide a continuous graphene layer, but commensurate stitching should be further studied.Graphene growth on liquid Cu has received great interest, owing to the self-assembly behavior of hexagonal graphene flakes with aligned orientation and to the possibility of forming a single grain of graphene through a commensurate growth of these graphene flakes. Here, we propose and demonstrate a two-step growth process which allows the formation of self-assembled, completely continuous graphene on liquid Cu. After the formation of full coverage on the liquid Cu, grain boundaries were revealed via selective hydrogen etching and the original grain boundaries were clearly resolved. This result indicates that, while the flakes self-assembled with the same orientation, there still remain structural defects, gaps and voids that were not resolved by optical microscopy or scanning electron microscopy. To overcome this limitation, the two-step growth process was employed, consisting of a sequential process of a normal single-layer graphene growth and self-assembly process with a low carbon flux, followed by the final stage of graphene growth at a high degree of supersaturation with a high carbon flux. Continuity of the flakes was verified via hydrogen etching and a NaCl-assisted oxidation process, as well as by measuring the electrical properties of the graphene grown by the two-step process. Two-step growth can provide a continuous graphene layer, but commensurate stitching should be further studied. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03352g

MITLL Silicon Integrated Photonics Process: Design Guide

DTIC Science & Technology

2015-07-31

Silicon Integrated Photonics Process Comprehensive Design Guide 16  Deep Etch for Fiber Coupling (DEEP_ETCH...facets for fiber coupling. Standard design layers for each process are defined in Section 3, but other options can be made available. Notes on...a silicon thinning process that can create very low loss waveguides (and which better suppresses back scatter and, therefore, resonance splitting in

Micrographic detection of plastic deformation in nickel base alloys

DOEpatents

Steeves, Arthur F.; Bibb, Albert E.

1984-01-01

A method for detecting low levels of plastic deformation in metal articles comprising electrolytically etching a flow free surface of the metal article with nital at a current density of less than about 0.1 amp/cm.sup.2 and microscopically examining the etched surface to determine the presence of alternating striations. The presence of striations indicates plastic deformation in the article.