Showing papers on "Silicon published in 1985"

Handbook of Optical Constants of Solids

Abstract: VOLUME ONE: Determination of Optical Constants: E.D. Palik, Introductory Remarks. R.F. Potter, Basic Parameters for Measuring Optical Properties. D.Y. Smith, Dispersion Theory, Sum Rules, and Their Application to the Analysis of Optical Data. W.R. Hunter, Measurement of Optical Constants in the Vacuum Ultraviolet Spectral Region. D.E. Aspnes, The Accurate Determination of Optical Properties by Ellipsometry. J. Shamir, Interferometric Methods for the Determination of Thin-Film Parameters. P.A. Temple, Thin-Film Absorplance Measurements Using Laser Colorimetry. G.J. Simonis, Complex Index of Refraction Measurements of Near-Millimeter Wavelengths. B. Jensen, The Quantum Extension of the Drude--Zener Theory in Polar Semiconductors. D.W. Lynch, Interband Absorption--Mechanisms and Interpretation. S.S. Mitra, Optical Properties of Nonmetallic Solids for Photon Energies below the Fundamental Band Gap. Critiques--Metals: D.W. Lynch and W.R. Hunter, Comments of the Optical Constants of Metals and an Introduction to the Data for Several Metals. D.Y. Smith, E. Shiles, and M. Inokuti, The Optical Properties of Metallic Aluminum. Critiques--Semiconductors: E.D. Palik, Cadium Telluride (CdTe). E.D. Palik, Gallium Arsenide (GaAs). A. Borghesi and G. Guizzetti, Gallium Phosphide (GaP). R.F. Potter, Germanium (Ge). E.D. Palik and R.T. Holm, Indium Arsenide (InAs). R.T. Holm, Indium Antimonide (InSb). O.J. Glembocki and H. Piller, Indium Phosphide (InP). G. Bauer and H. Krenn, Lead Selenide (PbSe). G. Guizzetti and A. Borghesi, Lead Sulfide (PbS). G. Bauer and H. Krenn, Lead Telluride (PbTe). D.F. Edwards, Silicon (Si). H. Piller, Silicon (Amorphous) (-Si). W.J. Choyke and E.D. Palik, Silicon Carbide (SiC). E.D. Palik and A. Addamiano, Zinc Sulfide (ZnS). Critiques--Insulators: D.J. Treacy, Arsenic Selenide (As 2 gt Se 3 gt ). D.J. Treacy, Arsenic Sulfide (As 2 gt S 3 gt ). D.F. Edwards and H.R. Philipp, Cubic Carbon (Diamond). E.D. Palik and W.R. Hunter, Litium Fluoride (LiF). E.D. Palik, Lithium Niobote (LiNbO 3 gt ). E.D. Palik, Potassium Chloride (KCl). H.R. Philipp, Silicon Dioxide (SiO 2 gt ), Type ( (Crystalline). H.R. Philipp, Silicon Dioxide (SiO 2 gt ) (Glass). gt H.R. Philipp, Silicon Monoxide (SiO) (Noncrystalline). H.R. Philipp, Silicon Nitride (Si 3 gt N 4 gt ) (Noncrystalline). J.E. Eldridge and E.D. Palik, Sodium Chloride (NaCl). M.W. Ribarsky, Titanium Dioxide (TiO 2 gt ) (Rutile).

Light-induced metastable defects in hydrogenated amorphous silicon: A systematic study.

Abstract: We study the magnitude of metastable light-induced changes in undoped hydrogenated amorphous silicon (the Staebler-Wronski effect) with electron-spin-resonance and photoconductivity measurements. The influence of the following parameters is investigated in a systematic way: sample thickness, impurity content, illumination time, light intensity, photon energy, and illumination and annealing temperatures. The experimental results can be explained quantitatively by a model based on the nonradiative recombination of photoexcited carriers as the defect-creating step. In the framework of this model, the Staebler-Wronski effect is an intrinsic, self-limiting bulk process, characterized by a strongly sublinear dependence on the total light exposure of a sample. The experimental results suggest that the metastable changes are caused by recombination-induced breaking of weak Si--Si bonds, rather than by trapping of excess carriers in already existing defects. Hydrogen could be involved in the microscopic mechanism as a stabilizing element. The main metastable defect created by prolonged illumination is the silicon dangling bond. An analysis of the annealing behavior shows that a broad distribution of metastable dangling bonds exists, characterized by a variation of the energy barrier separating the metastable state from the stable ground state between 0.9 and 1.3 eV.

Optical properties of semiconducting iron disilicide thin films

Abstract: Iron disilicide thin films were prepared by furnace reaction of ion beam sputtered iron layers with single‐crystal silicon wafers and with low‐pressure chemical vapor deposition (LPCVD) polycrystalline silicon thin films. X‐ray diffraction indicates the films are single‐phase, orthorhombic, β‐FeSi2. Impurity levels are below the detection limit of Auger spectroscopy. Normal incidence spectral transmittance and reflectance data indicate a minimum, direct energy gap of 0.87 eV. The apparent thermal activation energy of the resistivity in the intrinsic regime is about half of this minimum optical gap. With such a direct band gap, the material may be suitable for the development of both light‐sensitive and light‐emitting thin‐film devices within the silicon microelectronics technology.

Impurities in silicon solar cells

Abstract: Metallic impurities, both singly and in combinations, affect the performance of silicon solar cells. Czochralski silicon web crystals were grown with controlled additions of secondary impurities. The primary electrical dopants were boron and phosphorus. The silicon test ingots were grown under controlled and carefully monitored conditions from high-purity charge and dopant material to minimize unintentional contamination. Following growth, each crystal was characterized by chemical, microstructural, electrical, and solar cell tests to provide a detailed and internally consistent description of the relationships between silicon impurity concentration and solar cell performance. Deep-level spectroscopy measurements were used to measure impurity concentrations at levels below the detectability of other techniques and to study thermally-induced changes in impurity activity. For the majority of contaminants, impurity-induced performance loss is due to a reduction of the base diffusion length. From these observations, a semi-empirical model which predicts cell performance as a function of metal impurity concentration was formulated. The model was then used successfully to predict the behavior of solar cells bearing as many as 11 different impurities.

Point defects, diffusion processes, and swirl defect formation in silicon

Abstract: The paper consists of three parts. In the first part we review the basic experimental and theoretical results which shaped our present knowledge on point defects and diffusion processes in silicon. These results concern on one side oxidation effects which established that silicon self-interstitials and vacancies coexist in silicon and on the other side diffusion of gold into dislocation-free silicon which allowed to determine the self-interstitial contribution to silicon self-diffusion and to estimate the corresponding vacancy contribution. In the second part we discuss topics for which an understanding is just emerging within the framework of coexisting self-interstitials and vacancies: reaching of local dynamical equilibrium between self-interstitials and vacancies; rough estimates of the thermal equilibrium concentrations of self-interstitials and vacancies and their respective diffusivities, and finally, various possibilities to generate an undersaturation of self-interstitials. In the third part we examine swirl defect formation in silicon in terms of vacancies and self-interstitials.

Diffusion of radiolytic molecular hydrogen as a mechanism for the post‐irradiation buildup of interface states in SiO2‐on‐Si structures

Abstract: A review is made of recent literature dealing with radiation‐induced point defects distributed volumetrically in thermally grown SiO2‐on‐Si or superficially at the silicon interface, with particular emphasis on the results of electron‐spin‐resonance experimentation. The observed defect types and their anneal kinetics are then compared with recent advances in the understanding of similar species and processes in irradiated bulk fused silica. It is concluded that radiolytic molecular hydrogen is formed in thermally grown SiO2 layers, just as it is in bulk fused silica, and that the diffusion of this hydrogen determines the temperature and time dependencies of the post‐irradiation interface state buildups.

Metastable phase formation in titanium‐silicon thin films

Abstract: The formation of TiSi2 thin films on silicon substrates has been investigated with several transmission electron microscope techniques. For films formed either by reacting titanium with a silicon substrate or by sintering a codeposited (Ti+Si) mixture, electron diffraction patterns show that a metastable phase—TiSi2 (C49 or ZrSi2 structure)—forms prior to the equilibrium phase—TiSi2 (C54 structure). High‐resolution images indicate that the metastable TiSi2‐silicon interface is atomically sharp, with no ‘‘glassy membrane’’ layer present. The annealing temperature required to transform the metastable TiSi2 to the low resistivity, equilibrium TiSi2 increases as the thin‐film impurity content increases. Previous studies of TiSi2 formation are discussed in light of these results.

1.54‐μm electroluminescence of erbium‐doped silicon grown by molecular beam epitaxy

Abstract: The feasibility of producing erbium‐doped silicon light‐emitting diodes by molecular beam epitaxy is demonstrated. The p‐n junctions are formed by growing an erbium‐doped p‐type epitaxial silicon layer on an n‐type silicon substrate. When the diodes are biased in the forward direction at 77 K they show an intense sharply structured electroluminescence spectrum at 1.54 μm. This luminescence is assigned to the internal 4f–4f transition 4I13/2→4I15/2 of Er3+ (4f11).

Erratum: Indirect band gap of coherently strained Ge x Si 1 − x bulk alloys on silicon substrates

Abstract: Estimates of the indirect band gap for coherently strained alloys of ${\mathrm{Ge}}_{\mathrm{x}}$${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$ on Si〈001〉 are given for x in the range 0\ensuremath{\le}x\ensuremath{\le}0.75. The present results were obtained by combining x-ray diffraction data with relevant deformation-potential constants and using the phenomenological strain Hamiltonian of Kleiner and Roth. Uniaxial splittings of the sixfold-degenerate valence-band edge were calculated using the 6\ifmmode\times\else\texttimes\fi{}6 Hamiltonian of Hasegawa. It is found that the coherency strain generated by lattice mismatch dramatically reduces the indirect gap of the alloy (which approaches the ${L}_{1}$-${\ensuremath{\Gamma}}_{25}^{\mathcal{'}}$ gap of unstrained Ge at x\ensuremath{\simeq}0.6).

A high-yield IC-compatible multichannel recording array

Abstract: This paper reports the development of a multielectrode recording array for use in studies of information processing in the central nervous system and in the closed-loop control of neural prostheses. The probe utilizes a silicon supporting carrier which is defined using a deep boron diffusion and an anisotropic etch stop. This substrate supports an array of polysilicon or tantalum thin-film conductors insulated above and below with silicon nitride and silicon dioxide. Typical probe dimensions include a length of 3 mm, shank width of 50 µm, and a thickness of 15 µm. These structures are capable of simultaneous high-amplitude multichannel recording of neural activity in the cortex. The probe fabrication process requires only four masks and is single-sided using wafers of normal thickness, resulting in yields which exceed 80 percent. The process is also compatible with the inclusion of on-chip MOS circuitry for signal amplification and multiplexing. A complete ten-channel signal processor which requires only three external probe leads is being developed.

1/f and random telegraph noise in silicon metal‐oxide‐semiconductor field‐effect transistors

Abstract: We demonstrate that deviations from 1/ f noise behavior found in submicron silicon metal‐oxide‐semiconductor field‐effect transistors operating at room temperature are the direct result of the decomposition of the 1/ f spectrum into its constituent Lorentzian components. In the time domain, these devices produce random telegraph signals due to localized and discrete modulations of the channel resistance caused by individual carrier trapping events.

A simple technique for the determination of mechanical strain in thin films with applications to polysilicon

Abstract: Free standing, doubly supported micromechanical beams which are fabricated from films with built‐in compressive strain fields buckle at critical geometries. Experimental determination of the onset of buckling for known geometries leads to a direct measurement of the strain level in the films. This idea is supported by appropriate theory for experimental structures which form clamped, doubly supported beams with constant cross section and varying lengths. Application to low pressure chemical vapor deposition polysilicon leads to the conclusion that strain fields of 0.2% reduce to 0.05% during annealing.

Microstructure and formation mechanism of porous silicon

Abstract: A systematic study is presented of the effects of silicon dopant type, resistivity, current density, and hydrofluoric acid concentration on the formation and properties of porous silicon. Cross‐section transmission electron microscopy revealed the presence of two distinct microstructures. The structure formed is determined by the doping level with the transition occurring near degeneracy. A model of the anodisation process is presented which is based on the semiconducting properties of the material and which explains the formation of the two different types of porous structure observed.

Limited reaction processing: Silicon epitaxy

Abstract: We introduce a new technique, limited reaction processing, in which radiant heating is used to provide rapid, precise changes in the temperature of a substrate to control surface reactions. This process was used to fabricate thin layers of high quality epitaxial silicon. Abrupt transitions in doping concentration at the epitaxial layer/substrate interface were achieved for undoped films deposited on heavily doped substrates.

Resonator sensors-a review

Abstract: Control systems are becoming increasingly dependent on digital processing and so require sensors able to provide direct digital inputs Resonator sensors, configured to have a mechanical resonance frequency or relative phase of oscillation dependent on the measured parameter, are a subject of considerable practical interest The author reviews the wide range of devices which have been proposed and developed, including sensors for liquid or gas density and viscosity, liquid level, mass and mechanical force, and fluid flow rates Techniques cover the frequency range from audio, for sensors based on vibrating vanes or tubes, to 100 MHz or more for surface acoustic wave devices Resonator sensors based on single crystal materials such as quartz and silicon are of particular interest because they combine high accuracy and repeatability and low cost of manufacture and potentially very low power consumption

Hydrogen localization near boron in silicon

Abstract: Several models of boron neutralized by atomic hydrogen in silicon were tested by secondary ion mass spectrometry and infrared spectrometry. The hydrogen concentration is comparable to that of boron. Boron neutralization appears as a drop in free‐carrier absorption and as an increase in resistivity. A new infrared vibrational mode attributed to 〈111〉 vibrations of H tied to Si appears at 1875 cm−1.

Interatomic potentials for silicon structural energies.

Abstract: We develop two- and three-body classical interatomic potentials that model structural energies for silicon. These potentials provide a global fit to a data base of first-principles calculations of the energy for bulk and surface silicon structures which spans a wide range of atomic coordinations and bonding geometries. This is accomplished by use of a new "separable" form for the three-body potential that reduces the three-body energy to a product of two-body sums and leads to computations of the energy and atomic forces in ${n}^{2}$ steps as opposed to ${n}^{3}$ for a general three-body potential.

Annealing characteristics of Si‐rich SiO2 films

Abstract: Silicon‐rich SiO2 films of various compositions were deposited by atmospheric or plasma‐enhanced chemical vapor deposition (CVD) techniques. These films were annealed at various temperatures between 700 and 1100 °C. The growth and crystallinity of the silicon clusters were monitored by transmission electron microscopy. The growth of the silicon clusters was found to be diffusion controlled with an activation energy measured to a first approximation at 1.9 eV/atom for both atmospheric and plasma‐enhanced CVD films. A minimum annealing temperature of between 800 and 950 °C and a minimum amount of excess Si above SiO2 are required to form crystalline silicon particles in the films. The minimum silicon crystal diameter was measured at 2.5 nm.

Molybdenum-silicon multilayer mirrors for the extreme ultraviolet.

Abstract: Multilayer structures of molybdenum and silicon have been synthesized by sputter deposition onto flat silicon single-crystal silicon substrates and spherically ground (0.5and 22.0-m radii) fused silica substrates; and the reflectivities for 170.4-A (72.8-eV), 160.1-A (77.4-eV), and 228-A (54.4-eV) light measured at near normal incidence. Observed peak values ranged from 26.2 to 78 percent, the highest reflectivities occurring closest to normal incidence. Energy resolutions were about 10 in all cases. Model calculations were performed using optical constants and experimentally determined multilayer structural parameters. In all cases the measured reflectivities were equal to or larger (by up to a factor of 2) than the calculated values, a result attributed to uncertainty in the optical constants used in the calculations. Experimental and calculated angular-peak positions and energy resolutions were in good agreement. The high reflectivities of these molybdenum-silicon structures will make possible application of traditional optics approaches in the EUV and support new developments including free-electron lasers.

Effect of silicon on the crystallization and adsorption properties of ferric oxides.

Abstract: Influence de silicate dissous sur les proprietes globales et superficielles d'oxyhydroxydes de fer vieillis

Thermal nitridation of Si and SiO 2 for VLSI

Abstract: This paper presents an extensive review of our work on thermal nitridation of Si and SiO 2 . High-quality ultrathin films of silicon nitride and nitrided-oxide (nitroxide) have been thermally grown in ammonia atmosphere in a cold-wall RF-heated reactor and in a lamp-heated system. The growth kinetics and their dependence on processing time and temperature have been studied from very short to long nitridation times. The kinetics of thermal nitridation of SiO 2 in ammonia ambient have also been studied. In nitroxide, nitrogen-rich layers are formed at the surface and interface at a very early stage of the nitridation. Then the nitridation reaction mainly goes on in the bulk region with the surface and near interface nitrogen content remaining fairly constant. Our results also indicate the formation of an oxygen-rich layer at the interface underneath the nitrogen-rich layer whose thickness increases slowly with nitridation time. The nitride and nitroxide films were analyzed using Auger electron spectroscopy, grazing angle Rutherford backscattering, and etch rate measurements. MIS devices were fabricated using these films as gate insulators and were electrically characterized using I - V, C - V , time-dependent breakdown, trapping, and dielectric breakdown techniques. Breakdown, conduction, and C-V measurements on metal-insulator semiconductor (MIS) structures fabricated with these films show that very thin thermal silicon nitride and nitroxide films can be used as gate dielectrics for future highly scaled-down VLSI devices. The electrical characterization results also indicate extremely low trapping in the nitride films. The reliability of ultrathin nitride was observed to be far superior to SiO 2 and nitroxide due to its much less trapping. Studies show that the interface transition from nitride to silicon is almost abrupt and the morphology and roughness of the interface are comparable to the SiO 2 -Si interfaces.

Prediction of silicon-29 nuclear magnetic resonance chemical shifts using a group electronegativity approach: applications to silicate and aluminosilicate structures

Abstract: Linear relations between group electronegativeity (EN) sums of ligands bonded to tetravalent silicon and silicon-29 nuclear magnetic resonance (NMR) chemical shift (Ssi) are shown to exist for both type P silicon (all ligands have lone-pair electrons available for (d-p) d o n d i n g , e.g., in (MeO),Si) and type S silicon (all ligands have only a-bonding electrons available, e.g., in (CH3),Si). For type P silicon having group electronegativity sums greater than 11, a range encompassing all minerals, we have used previously reported E N and aSi values (for aryl-, halo-, and alkoxysilanes) to describe the observed silicon-29 N M R chemical shift as S(Si,P) = -24.336CEN(P) + 279.27. We then apply this correlation to a wide range of silicates and aluminosilicates (containing insular (Q’) to framework (Q4) Si sites) to predict silicon-29 NMR chemical shifts by means of a group fragment electronegativity sum approach, in which all fragments (e.g., OAl, OLi, O c a ) attached to Si are assigned, on the basis of experiments on a series of model silicates and the above equation, a characteristic group (or fragment) electronegativity value. OSi group electronegativities are scaled linearly with bridging bond angle. As an example of the use of the method, the electronegativity sum value for the cyclosilicate (Qz) beryl (A12Be3(Si03)6) is derived as EN(0Be) + EN(OA1) + 2(EN(OSi) (168.2’)) = 15.67, which predicts a silicon-29 chemical shift of -102.1 ppm (from Me@), that compares favorably with the value from experiment, -102.6 ppm. On the basis of a total of 99 sites in 51 different compounds, the mean absolute deviation between theory and experiment is 1.96 ppm (correlation coefficient = 0.979). When all types of silicon are considered (Qo-Q4), this empirical approach is the most accurate method of predicting silicon-29 chemical shifts found to date. Since 1980, there has been very considerable interest in using solid-state silicon-29 nuclear magnetic resonance ( N M R ) spectroscopy, with “magic-angle’’ sample-spinning (MASS), to investigate the structures of a wide variety of silicate and aluminosilicate materials of interest in chemistry and ge~chemistry.’-~ In order to interpret the silicon-29 shifts observed in structural terms, various correlations based on bond length,6 bridging bond angle,’x8 bond ~ t r e n g t h , ~ * ’ ~ mean TOT distance,” and a-orbital hybridization12 have been presented, together with a recent calculation of the paramagnetic shift term (a,) based on band-gap and refractive index dispersion data.13 E.O. was a U.S.P.H.S Research Career Development Awardee, 1979-1984 (Grant CA-00595). T o date, when all silicate phases are examined, the best correlation between experiment and prediction is by use of the (1) E. Lippmaa, M. Magi, A. Samoson, G. Engelhardt. and A.-R. Grim(2) E. Lippmaa, M. Magi, A. Samoson, M. Tarmak, and G. Engelhardt, (3) C. A. Fyfe, J. M. Thomas, J. Klinowski, and G. C. Gobbi, Angew. (4) C . A. Fyfe, G. C. Gobbi, J. Klinowski, J. M. Thomas, and S. Ramdas, (5) E. Oldfield and R. J. Kirkpatrick, Science, 227, 1537 (1985). (6) J. B. Higgins and D. E. Woessner, EOS (Tram. Am. Geophys. Union), 63, 1139 (1982). A.-R. Grimmer, R. Peter, E. Fechner, and G. Molgedey, Chem. Phys. Lett., 77, 331 (1981). A.-R. Grimmer and R. Radeglia, Chem. Phys. Let t . , 106, 262 (1984). mer, J . Am. Chem. SOC., 102, 4889 (1980). J . Am. Chem. SOC., 103, 4992 (1981). Chem., Int. Ed. Engl., 22, 259 (1983). Nature (London), 296, 530 (1982). 0002-7863/85/ 1507-6769$01.50/0

Quantum yield of electron impact ionization in silicon

Abstract: p‐channel Si‐gate metal‐oxide‐semiconductor transistors of very thin oxides are used for the study of quantum yield of electron impact ionization in silicon. Electrons are injected into silicon from the polysilicon gate by tunneling to give an approximate δ‐function energy distribution. This energy distribution is preserved when electrons pass through the oxide by direct tunneling. Using the carrier‐separation properties of the induced junction, we are able to experimentally measure the number of generated electron‐hole pairs as a function of the incident electron energy, up to 5 eV. Our results are found to be in excellent agreement with recent theoretical calculations of quantum yield. Beyond 5 eV, the interpretations on the experimental data are difficult due to the broadening of the incident electron energy distribution. This broadening effect is caused by strong scattering in the oxide when electrons tunnel by the Fowler–Nordheim (F–N) process. It is observed that the average energy of those electron...