Showing papers on "Silicon published in 1981"

Interface states and electron spin resonance centers in thermally oxidized (111) and (100) silicon wafers

Abstract: Interface states and electron spin resonance centers have been observed and compared in thermally oxidized (111) and (100) silicon wafers subjected to various processing treatments. The ESR Pb signal, previously assigned to interface ⋅Si≡Si3 defects on (111) wafers, was found to have two components on (100): an ⋅Si≡Si3 center oriented in accord with (100) face structure, and an unidentified center consistent with ⋅Si≡Si2O. The quantitative proportionality of Pb spin concentration to midgap interface trap density Dit is maintained on (100), and both are lower by a factor of about 3 compared to (111). This correlation persists over the range of oxidation temperatures 800–1200°C, for both n‐ and p‐doped silicon, cooled by fast pull in oxygen, and cooled or annealed in nitrogen or argon. The correlation is independent of doping level. In samples with different oxide thickness, neither Pb nor Dit varied significantly over the range 100–2000 A, but Pb was smaller at 50 A. In general, ESR is judged to offer prom...

Silicon and siliceous structures in biological systems

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Local structure of silicate glasses

Abstract: Extended X-ray absorption fine structure is used to study local order in silicate glasses around sodium and silicon atoms. It is demonstrated that modifying cations like sodium have well-defined short range order that is complementary rather than incidental to the glass forming silicate network.

Macroscopic theory of pulsed-laser annealing. I. Thermal transport and melting

Abstract: Pulses of radiation from ruby and Nd:YAG $Q$-switched lasers have been used recently to anneal the lattice damage caused by ion implantation of semiconductors. Other similar applications include the laser-induced diffusion of thin dopant films deposited on the surface of samples, recrystallization of doped amorphous films deposited on single-crystal substrates, and the removal of precipitates present after conventional high-temperature dopant diffusion. All of these processes can be understood in terms of models and calculations based on macroscopic diffusion equations for heat and mass transport, cast in a finite-difference form to allow for the temperature and spatial dependences of the thermal conductivity, absorption coefficient, reflectivity, and other quantities. Results of calculations on silicon with the models show that the near-surface region of a sample can melt and stay molten for times of the order of 100 nsec during which dopant diffusion in the liquid state and nonequilibrium segregation during ultrarapid recrystallization are sufficient to explain the major features of the experimental results. In this paper, a description of the model used in our heat-transport calculations is given. Results of the modeling are illustrated by a variety of calculations which should be of particular interest to experimentalists working with pulsed-laser annealing. These results include, e.g., the effects of pulse duration, shape, and energy density, the effects of assumptions made about the latent heat of amorphous silicon, the effects of substrate heating, the role played by the absorption coefficient in determining melt-front penetration, and the duration of surface melting.

A field-funneling effect on the collection of alpha-particle-generated carriers in silicon devices

Abstract: We studied the transient characteristics of charge collection from alpha-particle tracks in silicon devices. We have run computer calculations using the finite element method, in parallel with experimental work. When an alpha particle penetrates a pn-junction, the generated carriers drastically distort the junction field. After the alpha particle penetration, the field, which was originally limited to the depletion region, extends far down into the bulk silicon along the length of the alpha-particle track and funnels a large number of carriers into the struck junction. After a few nanoseconds, the field recovers to its position in the normal depletion layer, and, if the track is long enough, a residue of carriers is left to be transported by diffusion. The extent of this field funneling is a function of substrate concentration, bias voltage, and the alpha-particle energy.

Carrier mobilities in silicon semi-empirically related to temperature, doping and injection level

Abstract: From a review of different publications on the carrier mobilities in silicon, the authors propose an approximated calculation procedure which permits a quick and accurate evaluation of these mobilities over a large range of temperatures, doping concentrations and injection-levels. The proposed relations are well adapted to semiconductor device simulation becuase they allow short computation times.

Plasma etching of Si and SiO2 in SF6–O2 mixtures

Abstract: The products of reaction and etch rates of Si and SiO2 in SF6‐O2 plasmas have been studied as a function of feed composition in an alumina tube reactor at 27 mHz, 45 W, and 1 Torr. There is a broad chemical analogy with CF4‐02 plasmas. As in CF4‐02 mixtures, the rate of Si etching and 703.7‐nm emission from electronically excited F atoms each exhibit distinct maxima as a function of feed gas composition; these data support a model in which fluorine atoms, the etching species, compete with oxygen atoms for chemisorption on the Si surface. Without oxygen in the feed or Si in the reactor, no stable products could be detected. With an SF6‐O2 mixture in the absence of silicon, the final reaction products are F2, SOF4, and SO2F2. The product distribution was unaffected by small SiO2 substrates. When Si is etched, SiF4 is the only stable silicon‐containing etch product and SOF2 is formed in oxygen‐poor mixtures. Rapid etch rates (≳104 A/min for Si) can be obtained with a high selectivity in favor of silicon (Si:...

Application of amorphous silicon field effect transistors in addressable liquid crystal display panels

Abstract: It is shown that thin-film field effect transistors (FETs) made from amorphous (a-) silicon deposited by the glow-discharge technique have considerable potential as switching elements in addressable liquid crystal display panels. The fabrication of the elements and their characteristics with steady and pulsed applied potentials are discussed in some detail. Two important points are stressed: (i) a-Si device arrays can be produced by well-established photolithographic techniques, and (ii) satisfactory operation at applied voltages below 15VV is possible. Small experimental 7×5 transistor panels have been investigated and it is shown that with the present design up to 250-way multiplexing could be achieved. The reproducibility of FET characteristics is good and in tests so far no change has been observed after more than 109 switching operations.

Optical absorption in heavily doped silicon

Abstract: Optical-absorption measurements at 300 and 4 K on a series of heavily doped Si:As and Si:B samples are reported. The interband contribution is isolated and confronted with the predictions of an electron-gas calculation. Disorder effects are observed and impurity-derived states are found to play a significant role, invalidating the electron-gas model at concentrations lower than ${10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. The gap shrinkage follows a critical behavior, going to zero at the insulator-metal transition and varying approximately linearly with concentration at high doping. The discrepancy between device-based and optical determinations of the gap shrinkage is discussed.

Stoichiometric disturbances in ion implanted compound semiconductors

Abstract: Disturbances in the stoichiometry of compound semiconductors which result from ion implantation are calculated using a Boltzmann transport equation approach. Results for 50‐keV boron, 150‐keV silicon, and 400‐keV selenium implanted into silicon carbide, indium phosphide, and gallium arsenide are presented. Possible complications in the annealing of such implants are discussed.

Matching properties, and voltage and temperature dependence of MOS capacitors

Abstract: The matching properties of MOS capacitors are modeled and compared with measured data. A weighted-capacitor array design approach is described. Voltage and temperature dependence of MOS capacitors are analyzed, modeled, and compared with measured data. It is shown that to a first-order heavily doped polysilicon accumulates and depletes similar to crystalline silicon.

Quasiparticle lifetime in disordered two-dimensional metals

Abstract: A calculation of the electron quasiparticle lifetime in a disordered metal due to electron-electron scattering is given. The calculation takes account of the diffusive nature of electron motion which leads to enhancement of the diagonal exchange term of the electron self-energy. The lifetime, as a function of temperature, behaves as ${T}^{\ensuremath{-}\frac{d}{2}}$ where $d$ is the dimensionality, in contrast to the ${T}^{\ensuremath{-}2}$ behavior of ordinary Fermi-liquid theory. At $d=2$, a logarithmic singularity occurs which leads to ${(T\mathrm{ln}T)}^{\ensuremath{-}1}$ behavior of the lifetime and a failure of the quasiparticle picture near the Fermi surface. The calculated lifetime agrees in temperature, Fermi energy, and elastic mean-free-path dependence with recent experiments on silicon inversion layers.

A new dielectric isolation method using porous silicon

Abstract: A new dielectric isolation technology is proposed. In the new structure, single crystalline Si islands are separated from the silicon substrate by oxidized porous silicon. It is based on the following characteristics of the porous silicon oxide formation: (1) p -type Si is more easily changed to porous silicon than n -type Si; (2) porous silicon is formed along the anodic reaction current flow line; (3) the change in volume of porous silicon after oxidation is relatively small; (4) thick porous silicon films (10 μm) can be obtained easily. In this method, a p -type isolated layer is obtained by proton implantation used for an n -type layer formation. Lateral p - n junctions fabricated in such isolated silicon layers show lower leakage current than those reported in SOS technology.

Silicon substituted zeolite compositions and process for preparing same

Abstract: Aluminum from AlO 4 -tetrahedra of as-synthesized zeolites is extracted and substituted with silicon to form zeolite compositions having higher SiO 2 /Al 2 O 3 molar ratios and exhibiting distinctive chemical and physical properties. The preparative procedure involves contact of the starting zeolite with an aqueous solution of a fluorosilicate salt using controlled proportions and temperature and pH conditions which avoid aluminum extraction without silicon substitution.

The Properties of Iron in Silicon

Abstract: The properties of iron in n‐type and p‐type silicon were studied by means of DLTS, carrier lifetime measurements, and infrared absorption spectroscopy. Only one donor level was observed, situated at and correlated to iron on an interstitial site. In p‐Si:B iron‐boron pairs were formed at room temperature. Their activation energy was determined to be . The reaction proceeded in two phases. In the second phase a thermal equilibrium between iron and iron‐boron pairs was found which could be shifted by annealing and illuminating the specimen, respectively. In aluminum‐doped silicon crystals two levels were observed after iron diffusion correlated to iron‐aluminum pairs. Their activation energies were determined to be . It is assumed that iron‐boron pairs form also two levels, a donor and an acceptor. The acceptor must be situated in the upper half of the silicon bandgap. Reaction mechanisms are discussed.

Microwave-excited atmospheric pressure helium plasma emission detection characteristics in fused silica capillary gas chromatography

Abstract: Interfacing of fused silica gas chromatographic capillary columns to a microwave-excited atmospheric pressure helium plasma (MED) is investigated. The system for glass and fused silica capillary operation incorporates an interface where excess solvent can be vented by a chemically deactivated fluidic-logic gas switching system. A TM/sub 010/ resonant cavity allows axial viewing of plasma emission. A quartz refractor plate background corrector improves selectivity ratios for elements whose emission occurs in the high-carbon (cyanogen) background region. Background emission characteristics of the helium plasma under various conditions are established from 200 to 500 nm. Calibration curves, selectivity ratios, and detection limits are established for the elements vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, osmium, cobalt, nickel, mercury, boron, aluminum, carbon, silicon, germanium, tin, lead, phosphorus, arsenic, sulfur, selenium, fluorine, chlorine, bromine, iodine, hydrogen, and deuterium.

The magnetic properties of the oxygen-hole aluminum centres in crystalline SiO2. IV. [AlO4/Na]+

Abstract: The centre [AlO4/Na]+, formed in α-quartz by X irradiation at 77 K, contains an aluminum ion substituted for a silicon ion, with an electron hole on a nearest-neighbor oxygen ion, and an interstiti...

Raman efficiency measurements of graphite

Abstract: The Raman efficiency of graphite, germanium and silicon have been measured at room temperature with 5145 A laser excitation The efficiencies were determined from a comparison with the 1332 cm−1 zone center phonon of diamond For graphite, the 1585 cm−1 E2g intralayer mode was studied, while for Si and Ge the 525 cm−1 and 303 cm−1 F2g zone center modes were measured

Effects of inert gas dilution of silane on plasma‐deposited a‐Si:H films

Abstract: Electrical, optical, and structural characterization of hydrogenated amorphous silicon films plasma‐deposited from mixtures of SiH4 with different inert‐gas diluents reveals substantial differences in a number of properties. A general trend of increasing defect density with atomic weight of the inert gas is observed. Of specific interest to device applications is the observation that high deposition rates can be achieved concurrently with low defect densities when helium is used as a deluent.

Plasma Si nitride—A promising dielectric to achieve high-quality silicon MIS/IL solar cells

Abstract: Substantial advantages of plasma Si nitride, for the first time applied to silicon MIS inversion layer (MIS/IL) solar cells, are demonstrated: The highest positive interface charge densities ever used for this type of solar cell (up to 72×1012 cm−2), absolute stability of the charges up to the nitride despoition temperature (220 and 300 °C, respectively), excellent passivation of the entire cell, and good AR coating properties High uv sensitive MIS/IL solar cells were fabricated with these layers on p–Si (100) AM1 efficiencies of 15% (active area) at 25 °C were obtained

Silicon-terminated polyurethane polymer

Abstract: What are disclosed are the method of making a moisture-curable silicon terminated organic polymer which comprises reacting a polyurethane prepolymer having terminal active hydrogen atoms with an isocyanato organosilane having at least one hydrolyzable alkoxy group bonded to silicon, silicon terminated organic polymers so produced, and moisture-curable sealant compositions comprising such a silicon terminated polymer.