bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monomeric Chelated Amides of Aluminum and Gallium: Volatile, Miscible Liquid Precursors for CVD
Authors: Barry Seàn T. , Gordon Roy G. , Wagner Valerie A. 
Published: April 2011

AbstractNew precursors were developed for the chemical vapor deposition (CVD) of aluminum nitride (AIN) and gallium nitride (GaN) at low temperatures. Synthetic methods for the new materials will be reported, along with their analyses and spectral characterization. The precursors are volatile (180 mTorr at 45-55 °C), low-viscosity (10 centipoise) liquids, so they are more convenient as vapor sources than previously available solid sources. They are thermally stable to temperatures well above their vaporization temperatures, so their vaporization is highly reproducible and leaves no residue. Unlike previously available liquid precursors, they are not pyrophoric, so they are safer to handle. AMN films formed by reaction with ammonia at around 200 °C are amorphous, transparent insulators that are good barriers to diffusion of water, oxygen, and other materials.
Metal-Organic Chemical Vapor Deposition of Zn-In-Sn-O and Ga-In-Sn-O Transparent Conducting Oxide Thin Films
Authors: Wang A. , Edleman N.L. , Babcock J.R. , Marks T.J. , Lane M.A. , Brazis P.W. , Kannewurf C.R. 
Published: April 2011

AbstractThe metal-organic chemical vapor deposition (MOCVD) technique has been successfully applied for growth of Sn-doped transparent, conducting Zn-In-O and Ga-In-O films using Sn(acac)2, In(dpm)3, Ga(dpm)3, and Zn(dpm)2, as volatile precursors. The 25 °C electrical conductivity of the as-grown films is as high as 1030 S/cm (n-type, carrier density N = 4.5 × 1020 cm−3, mobility µ = 14.3 cm2/V•s) for the Zn-In-O series and 700 S/cm (n-type, N = 8.1 × 1019 cm−3, µ = 55.2 cm2/V•s) for the Ga-In-O series. After Sn-doping, the Zn-In-O series exhibits 25 'C electrical conductivities as high as 2290 S/cm with a higher carrier mobility, while the Ga-InO series exhibits higher electrical conductivity (3280 S/cm at 25 °C) and much higher carrier density, but with diminished mobility. All films show broader optical transparency windows than that of commercial ITO films. Reductive annealing, carried out at 400-425 °C in a flowing gas mixture of H2(4%) and N2, results in increased carrier density and mobility as high as 64.6 cm2/V•s for films without Sn doping, but lowered carrier density for the Sn-doped films. X-ray diffraction, transmission electron microscopy, micro diffraction, and high-resolution X-ray analysis show that all films with good conductivity have cubic, homogeneously doped In2O3-like crystal structures.
Photoinduced Changes in the Charge States of Native Donors and Acceptors in ZnGeP2
Authors: Stevens K. T. , Setzler S. D. , Schunemann P. G. , Pollak T. M. , Giles N. C. , Halliburton L. E. 
Published: April 2011

AbstractBulk ZnGeP2 (ZGP) crystals grown for high-power tunable mid-infrared laser systems contain large concentrations of three native defects. Using EPR, these three defects have been identified as the Zn vacancy (an acceptor), the phosphorus vacancy (a donor), and the germanium-on-zinc antisite (also a donor). We have studied the wavelength dependence of the photoinduced changes in the EPR signal intensity of the three defect centers using 633 nm and 1064 nm light. We observe a significant increase in the EPR signal under 633 nm light. The 633-nm light also produces an increase in the defect-related 1-R.m absorption band, and we have used a spectrophotometer to measure the spectral shape of the photoinduced change in absorption in this near-IR region. The 633-nm wavelength produces paramagnetic forms of both donor centers, while 1064 nm light only produces the EPR-active center. Time decays of the photoinduced EPR signals have been measured for each of the donors.
ZnGep2 : Optical Transparency and Melt Composition
Authors: Verozubova G.A. , Gribenyukov A.I. , Vere A.W. , Flynn C. , Ivanov Y.F. 
Published: April 2011

AbstractThe paper presents the results of TEM and optical transparency measurements on ZnGeP2 crystals grown by the vertical Bridgman technique from melts of differing compositions. The TEM study reveals the presence of nano-dimensional precipitates of second phases: zinc and ZnxPy precipitation occurs in material grown from Zn-rich melts and GeP from the deficient melts. The precipitation is associated with cooling through the retrograde solidus at a temperature below the melting point. Elastic stress fields are also observed. The relationships between the precipitates and elastic stresses and between precipitation and optical losses are investigated
Room Temperature CW Operation of GaInAsSb/AlGaAsSb Quantum Well Lasers Emitting in the 2.2 to 2.3µm Wavelength Range
Authors: Mermelstein C. , Simanowski S. , Mayer M. , Kiefer R. , Schmitz J. , Walther M. , Wagner J. 
Published: April 2011

AbstractWe report on room temperature cw operation of type-I semiconductor quantum well (QW) laser diodes based on the GaInAsSb/AIGaAsSb/GaSb material system emitting beyond 2.2 µm. Lasing is observed in cw mode up to at least 320 K. A high internal quantum efficiency of 65% and a low internal loss coefficient of 5 cm1have been achieved for a single QW (SQW)large optical cavity laser at 280 K. An extrapolated threshold current density for infinite cavity length of 144 A/cm2and 55 A/cm2has been deduced for the 3 QW and SQW lasers, respectively, which scales with the number of QWs. A maximum cw light output power of 230 mW at 280 K heatsink temperature was obtained for a 3 QW large optical cavity laser with HR/AR coated mirror facets, mounted substrate-side down.
Small-Angle Neutron Scattering from Device-Quality a-Si:H and a-Si:D Prepared by PECVD and HWCVD
Authors: Williamson D.L. , Marr D.W.M. , Nelson B.P. , Iwaniczko E. , Yang J. , Yan B. , Guha S. 
Published: April 2011

ABSTRACTThe heterogeneity of a-Si:H and a-Si:D films has been probed on the nano-scale by small-angle neutron scattering (SANS). Films were deposited by two techniques, plasma-enhanced chemical-vapor deposition (PECVD) and hot-wire chemical-vapor deposition (HWCVD) using conditions that yield high-quality films and devices. Four samples were examined in a light-soaked state (AM1.5, 300 h) and then re-examined after annealing (190°C, 1 h) in-situ to look for any change in SANS associated with the Staebler-Wronski effect. No changes were observed in the SANS intensity to a precision that could have readily detected the 25% change reported in 1985 (Chenevas-Paule et al). Significant differences are observed in hydrogenated and deuterated films, as well as in the PECVD versus the HWCVD materials.
A European Adventure In Amorphous Materials: From Past to Future
Authors: Solomon Ionel 
Published: April 2011

ABSTRACTThe early work on amorphous silicon in Europe was dominated by the activity of the Dundee group, who demonstrated the feasibility of substitutional doping, in contradiction with previous theories which denied the possibility of doping disordered semiconductors. Also, the role of hydrogen in this new “good” disordered semiconductor was not immediately accepted, and the controversy was finally settled by the crucial experiment of post-hydrogenation by D. Kaplan. It is little known that this process of post-hydrogenation, currently used for the improvement of devices, was covered by a patent, which turned out to be quite inapplicable!The high hopes raised by this “new” material, in particular for photovoltaic applications, rendered the field highly competitive, resulting in a surprising neglect of the basic principles of physics. A striking example is the sweeping under the rug of the effect of band bending at the surface of intrinsic a-Si:H. This effect makes the surface much more conducting than the bulk, rendering a large number of published transport measurements in planar geometry completely meaningless.Research in Europe has been less application-oriented than research in USA and Japan, but on a small scale it was not completely absent from industrial applications to photovoltaics; a start-up adventure “a la French” is described. The problem of disordered materials is one of the timely solid-state topics, to continue to be a major subject of materials research in the near future. In that respect, amorphous silicon is an exemplary system, and the “hydrogen glass” picture, pioneered by R. A. Street et al., is an open field of research for the improvement of disordered semiconductors.
Gas-Phase and Surface Reactions of Decomposed Species In Catalytic Cvd
Authors: Honda Namiko , Masuda Atsushi , Matsumura Hideki 
Published: April 2011

ABSTRACTGas-phase and surface reactions of transported species decomposed on the catalyzer were investigated in catalytic CVD (Cat-CVD), often called hot-wire CVD, using a specially designed reactor tube. The phenomena were comparatively studied using H2- or He-diluted SiH4. It turned out that the control of gas flow through the catalyzer between the gas showerhead and the substrate is a key factor to obtain high uniformity in not only the film thickness but also the crystallinity for Si films prepared by Cat-CVD using the gas pressure above about 10 Pa and the gas-flow velocity faster than several m/s.
Nucleation Mechanism of Microcrystalline Silicon Studied by Real Time Spectroscopic Ellipsometry and Infrared Spectroscopy
Authors: Fujiwara Hiroyuki , Toyoshima Yasutake , Kondo Michio , Matsuda Akihisa 
Published: April 2011

ABSTRACTWe have characterized a-Si:H initial layers for μc-Si:H nucleation by real time spectroscopic ellipsometry (SE) and infrared attenuated total reflection spectroscopy (ATR) to investigate the μc-Si:H formation mechanism. By performing Ar plasma treatment of a-Si:H layers, we confirmed a presence of a 2 monolayer thick sub-surface in a-Si:H layers. In the a-Si:H sub-surface that leads to the μc-Si:H nucleation, an important peak at ∼1937 cm−1 assigned to the SiHn complex was found in the ATR spectra. From H2 plasma treatment experiments, we proposed that this SiHn complex is formed by H insertion into strained Si-Si bonds. The SiHn complex formed in the a-Si:H sub-surface showed a clear relationship with the μc-Si:H nucleation. From these results, we conclude that the μc-Si:H nucleation occurs by the formation of the chemically active and flexible SiHn complexes in the 2 monolayer thick a-Si:H sub-surface.
Dependence of H Diffusion in Hydrogenated Silicon on Doping and the Fermi Level
Authors: Beyer Wolfhard , Zastrow Uwe 
Published: April 2011

ABSTRACTFor three types of hydrogenated silicon films, amorphous, microcrystalline and crystalline hydrogenated silicon, hydrogen diffusion was studied as a function of doping level employing depth profiling by secondary ion mass spectrometry. Hydrogen implantation was used to control the hydrogen concentration. All three materials show a similar doping dependence of H diffusion, namely a strong increase upon boron (p-type) doping and a much lesser increase for n- type (P, As) doping. In a band model of H diffusion, the effect is related to a decrease in energy of the hydrogen diffusion path. Possible explanations are a different charge state of diffusing hydrogen or an effect of the Fermi energy on the release energy of neutral hydrogen.
Fabrication of Mechanical Microstructures Using Amorphous Silicon Films on Glass Substrates
Authors: Yeh Chingwen , Boyce James B. , Ho Jackson , Lau Rachel 
Published: April 2011

ABSTRACTA new process of surface micromachining has been developed, where amorphous silicon (a-Si) and oxynitride films are used as structural and sacrificial layers on the glass substrate, respectively. Due to glass as the substrate material, the temperatures for all process steps need to be lower than 600°C. Some generic mechanical microstructures such as cantilever beams, bridges, and membranes have been fabricated. The stress changes of a-Si films with annealing temperatures are studied. It is found that the residual stress can be minimized using thermal annealing at 430°C for a few hours. In addition, some process issues such as a-Si film bubbling, the film adhesion of a-Si to the glass substrate, and stiction during structure release are discussed.
Hydrogenated Amorphous Silicon Grown by Hot-Wire CVD at Deposition Rates up to 1 µm/minute
Authors: Nelson Brent P. , Xu Yueqin , Mahan A. Harv , Williamson D.L. , Crandal R.S. 
Published: April 2011

ABSTRACTWe grow hydrogenated amorphous-silicon (a-Si:H) by the hot-wire chemical vapor deposition (HWCVD) technique. In our standard tube-reactor we use a single filament, centered 5 cm below the substrate and obtain deposition rates up to 20 Å/s. However, by adding a second filament, and decreasing the filament-to-substrate distance, we are able to grow a-Si:H at deposition rates exceeding 167 Å/s (1 µm/min). We find the deposition rate increases with increasing deposition pressure, silane flow rate, and filament current and decreasing filament-tosubstrate distance. There are significant interactions among these parameters that require optimization to grow films of optimal quality for a desired deposition rate. Using our best conditions, we are able to maintain an AM1.5 photoconductivity-to-dark-conductivity ratio of 105 at deposition rates up to 130 Å/s, beyond which the conductivity ratio decreases. Other electronic properties decrease more rapidly with increasing deposition rate, including the ambipolar diffusion length, Urbach energy, and the as-grown defect density. Measurements of void density by small-angle X-ray scattering (SAXS) reveal an increase by well over an order of magnitude when going from one to two filaments. However, both Raman and X-ray diffraction (XRD) measurements show no change in film structure with increasing deposition rates up to 144 Å/s, and atomic force microscopy (AFM) reveals little change in topology.
Defect and Tail States in Microcrystalline Silicon investigated by pulsed ESR
Authors: Kanschat P. , Mell H. , Lips K. , Fuhs W. 
Published: April 2011

ABSTRACTWe report on a detailed analysis of paramagnetic states in a doping series of microcrystalline silicon, μc-Si:H, by pulsed electron spin resonance. We identify two dangling bond like structures at g = 2.0052 (db1) and g = 2.0043 (db2). Whereas db1 is evenly distributed in the gap, the db2 state is found to be localized in the lower part of the gap. The CE resonance at g ≈ 1.998 is assigned to electrons in conduction band tail states. In p-doped samples, we observe a broad structure CH at g ≈ 2.08 which we identify with holes trapped in valence band tail states. It is shown that the CH state behaves very similar on illumination as the CE resonance. In n-type samples a pair of hyperfine split lines (A ≈ 11 mT) is found which apparently does not originate from 31P-donor states. On the basis of our results we propose a qualitative model for paramagnetic states in μc-Si:H.
Low Temperature Poly-Si Layers Deposited by Hot Wire CVD Yielding a Mobility of 4.0 cm2V−1s−1 in Top Gate Thin Film Transistors
Authors: Schropp R.E.I. , Rath J.K. , Stannowski B. , Werf C.H.M. Van Der , Chen Y. , Wagner S. 
Published: April 2011

ABSTRACTDirect deposition of polycrystalline silicon (poly-Si) thin films by the Hot Wire CVD method has been used for the first time for the fabrication of poly-Si top gate Thin Film Transistors (TFTs). The TFTs have a high electron mobility in saturation of up to 4 cm2V−1s−1 as well as a remarkably large ON/OFF ratio of up to 6 × 105.
Gas Phase and Surface Kinetic Processes in Hot-Wire Chemical Vapor Deposition
Authors: Holt J. K. , Swiatek M. , Goodwin D. G. , Atwater Harry A. 
Published: April 2011

ABSTRACTOne- and two-dimensional numerical simulations have been used to determine the parameters critical to high rate growth of high quality polycrystalline silicon via hot-wire chemical vapor deposition at silane partial pressures of 1-70 mTorr and a wire temperature of 2000°C. The Direct Simulation Monte Carlo method [1] was used, including gas-phase chemistry relevant for growth. Model predictions agree both qualitatively and quantitatively with experimental measurements.
Surface roughness evolution of a-Si:H growth and its relation to the growth mechanism
Authors: Smets A.H.M. , Schram D.C. , van de Sanden M.C.M. 
Published: April 2011

ABSTRACTThe post-initial growth dynamic scaling exponent β, which describes the surface roughness evolution in time, is determined for a-Si:H growth using in situ single wavelength (632.8 nm) rotating compensator ellipsometry. β is measured as function of the substrate temperature for three different growth rates 2, 5 and 22 Ås-1 under conditions where SiH3 dominantly contributes to growth. β (≤ 0.5) decreases with increasing substrate temperature and does not strongly depend on the growth rate within the range of growth rates. A roughness evolution model is proposed, based upon a random generation of active growth sites and a subsequent site dependent surface diffusion process. The measured β temperature dependence can be simulated with an activated site hopping activation energy of about 1.0 eV. This activation energy is much higher than what would be expected from a model based upon the diffusion of physisorbed silyl SiH3 radical and suggests therefore another mechanism which is responsible for the surface smoothening during a-Si:H growth.
Thickness-Dependent Micro-Raman Measurement of Poly-Si Films Prepared by Metal-Induced-Crystallization using a Ni Layer
Authors: Muramatsu Shin-ichi , Minagawa Yasushi , Oka Fumihito , Yazawa Yoshiaki 
Published: April 2011

ABSTRACTRelatively thick amorphous silicon films for solar-cell applications were prepared by metal-induced-crystallization (MIC). Then, the thickness-dependent characteristics of micro-Raman spectra from a cross section of the prepared polycrystalline silicon (poly-Si) films were analyzed. It was found that Ni-induced crystallized films have a uniform composition that is 80% polycrystalline and 20% nanocrystalline. Also, the x-ray diffraction data show that a sub-mono-layer of Ni is sufficient for MIC of 6-μm-thick amorphous silicon (a-Si) films.
Probing Pore Characteristics in Low-K Thin Films Using Positronium Annihilation Lifetime Spectroscopy
Authors: Gidley D. W. , Frieze W. E. , Dull T. L. , Sun J. N. , Yee A. F. 
Published: April 2011

AbstractDepth profiled positronium annihilation lifetime spectroscopy (PALS) has been used to probe the pore characteristics (size, distribution, and interconnectivity) in thin, porous films, including silica and organic-based films. The technique is sensitive to all pores (both interconnected and closed) in the size range from 0.3 nm to 300 nm, even in films buried under a diffusion barrier. PALS may be particularly useful in deducing the pore-size distribution in closed-pore systems where gas absorption methods are not available. In this technique a focussed beam of several keV positrons forms positronium (Ps, the electron-positron bound state) with a depth distribution that depends on the selected positron beam energy. Ps inherently localizes in the pores where its natural (vacuum) annihilation lifetime of 142 ns is reduced by collisions with the pore surfaces. The collisionally reduced Ps lifetime is correlated with pore size and is the key feature in transforming a Ps lifetime distribution into a pore size distribution. In thin silica films that have been made porous by a variety of methods the pores are found to be interconnected and an average pore size is determined. In a mesoporous methyl-silsesquioxane film with nominally closed pores a pore size distribution has been determined. The sensitivity of PALS to metal overlayer interdiffusion is demonstrated. PALS is a non-destructive, depth profiling technique with the only requirement that positrons can be implanted into the porous film where Ps can form.
Ultra Low k Mesoporous Silica Films: Synthesis, Film Properties and One-Level Copper Damascene Evaluation
Authors: Jin Changming , Liu J. , Li X. , Coyle C. , Birnbaum J. , Fryxell G. E. , Williford R. E. , Baskaran S. 
Published: April 2011

AbstractSpin-on mesoporous silica films were prepared on eight-inch wafers at SEMATECH by condensation of a silicate network around surfactant micellar structures. Copper single-damascene one-level test structures were built using mesoporous silica as the intermetal dielectric. No major structural failures were observed after chemical mechanical planarization on both blanket films and patterned wafers, indicating relatively good mechanical integrity for a highly porous structure. A simple silane spin-coating step used at SEMATECH on the films appears to be insufficient for complete dehydroxylation and silylation. The electrical test results on the metal comb structures showed good capacitance and leakage current distributions. However, capacitance and leakage current changes were observed after each post-CMP process step, and these changes could be correlated to moisture desorption/outgassing, which was also noted during k measurement. With controlled film synthesis and dehydroxylation conditions, mesoporous silica films with k ≤2.0 and elastic modulus of 4.0 GPa have been synthesized at PNNL. The results of the Cu one-level metal screening tests at SEMATECH combined with properties obtained at PNNL indicate that mesoporous molecularly-templated silicate films hold promise as ultra low k intermetal dielectrics.
Material Properties of a SiOC Low Dielectric Constant Film with Extendibility to k < 2.7
Authors: Lopata Eugene S. , Young Lydia , Felts John T. 
Published: April 2011

AbstractA plasma deposited SiOC very low k (VLK) interlayer dielectric (ILD) film has been developed which can be tuned to 2.5 = k = 3.0, demonstrates very good thermal stability, excellent adhesion properties, acceptable hardness, and an indication that it may be extendible to k < 2.5. This paper will disclose properties of this SiOC film which are important to a VLK ILD application.
Fabrication and Performance Limits of Sub-0.1 µm Cu Interconnects
Authors: Kuan T. S. , Inoki C. K. , Oehrlein G. S. , Rose K. , Zhao Y. –P. , Wang G. –C. , Rossnagel S. M. , Cabral C. 
Published: April 2011

AbstractAs the on-chip interconnect linewidth and film thickness shrink below 0.1 µm, the size effect on Cu resistivity becomes important, and the electrical performance deliverable by such narrow metal lines needs to be assessed critically. From the fabrication viewpoint, it is also crucial to determine how structural parameters affect resistivity in the sub-0.1 µm feature size regime. To evaluate the scaling of resistivity with thickness, we have fabricated a series of Ta/Cu/Ta/SiO2 thin film structures with Cu thickness ranging from 1 µm to 0.02 µm. These test structures revealed a far larger (∼2.3 ×) size effect than that expected from surface scattering. We have also fabricated test structures containing 50-nm-wide Cu lines wrapped in Ta-based liners and embedded in insulating SiO2 using e-beam lithography, high-density plasma etching, ionized PVD Cu deposition, and chemical-mechanical planarization processes. Direct current (16 nA) resistance measurements from these 50-nm-wide Cu lines have also shown a higher- than-expected distribution of resistivity. Cross-sectional TEM and surface AFM observations suggest that the observed extra resistivity increase can be attributed to small grain sizes in ultra- thin Cu films and to Cu/Ta interface roughness. Monte Carlo simulations are used to quantify the extra resistivity resulting from interface roughness.