Showing papers on "Silicon published in 1974"

Thermal expansion of AlN, sapphire, and silicon

Abstract: Thermal expansion coefficients of high‐purity AlN, sapphire, and silicon were calculated from the data obtained with precision high‐temperature x‐ray lattice parameter measurements The mean thermal expansion coefficients obtained in the range 20–800°C are α⊥ = 53 × 10−6/°C and α∥ = 42 × 10−6/°C for AlN, α⊥ = 73 × 10−6/°C and α∥ = 81 × 10−6/°C for α‐Al2O3, and α = 36 × 10−6/°C for Si

The Current Understanding of Charges in the Thermally Oxidized Silicon Structure

Abstract: Generally accepted facts along with unanswered questions, concerning the four charges, , , , and , associated with the thermally oxidized silicon system are presented and briefly discussed. The discussions and information presented are based on comprehensive investigations carried out in the semiconductor industry over the past ten years. Although reasonably good empirical information concerning charge dependence on device processing is available, much remains to be learned regarding the physical origin of these charges. A simplified model is presented which indicates that most of the charges can be related to silicon bond defects in the thermally oxidized silicon structure.

Defect centers in a germanium-doped silica-core optical fiber

Abstract: The radiation‐induced defect centers in a low‐loss Corning germanium‐doped optical fiber have been studied. In addition to silicon E′ centers, four germanium‐related centers, corresponding to electrons trapped at the site of oxygen vacancies in s p3 orbitals of germanium ions with zero to three next‐nearest‐neighbor germaniums, were observed. A model which assumes Gaussian distributions in the excited‐state energy‐level splittings has been successfully used to computer simulate the ESR spectrum of the irradiated fiber.

Wetting of thin layers of SiO2 by water

Abstract: We have measured the contact angle θ of water on silicon and on very thin layers of silicon dioxide grown on silicon. The silicon is hydrophobic and θ is near 90°. Oxides thicker than 30 A are hydrophilic and θ is near 0°. For intermediate thicknesses, θ varies smoothly between these limits. Our results show that the interaction energy between water and the solid surface depends strongly on the oxide thickness. Consideration of different possible interactions leads us to conclude that this is due to corresponding changes in the structure or composition of the oxide surface.

The Kinetics of Silicon Deposition on Silicon by Pyrolysis of Silane A Mass Spectrometric Investigation by Molecular Beam Sampling

Abstract: The kinetics of silane pyrolysis on a silicon (111) surface has been investigated mass spectrometrically by molecular beam sampling over the silane pressure range Torr and specimen temperature range 20°–1200°C. Silane decomposition was found to occur by the mechanism where both the amount of adsorbed silane and decomposition rate depend linearly on silane pressure. The activation energy for decomposition was and the surface reaction efficiency (α) was found to obey the equation At silane pressures , small quantities of disilane formed by the bimolecular surface reaction were detected with an activation energy for production of .Measurements of silicon growth rate as a function of silane pressure supported the first‐order mechanism for decomposition. The condensation coefficient (σ) of silicon adatoms, determined from measurements of the silicon growth rate as a function of temperature and the surface reaction efficiency, was found to be less than 0.3 over the entire temperature range 700°–1200°C, indicating that the majority of silicon adatoms were desorbed. This behavior was accounted for on the basis of a step flow model for silicon growth and an activation energy for surface diffusion of derived. Addition of arsine to the silane was found to inhibit silane pyrolysis. The measurements suggest an activation energy of for desorption of arsenic adsorbed on the silicon (111) surface. Additions of more than 1% diborane to the silane, on the other hand, resulted in a significant increase in silane reaction efficiency.

Multiple‐pass thin‐film silicon solar cell

Abstract: A technique is described by which light entering a thin film is ``trapped'' in the sense of having to traverse the film a number of times. It is shown that the use of this technique in silicon provides a solar cell with good carrier collection efficiencies even with Si only ∼2 μm thick and with ∼10‐nsec lifetime.

Relationship between resistivity and phosphorus concentration in silicon

Abstract: Accurate electrical and analytical measurements allowed us to determine a relationship between resistivity and phosphorus concentration in doped silicon. This relationship is compared with that obtained by other authors in the case of n‐type silicon, and the differences due to the various doping agents are discussed. Differences between concentrations determined by analytical techniques and by Hall effect measurements are reported.

Diffusion of Ge in SiGe alloys

Abstract: Germanium diffusion was measured in SiGe alloys of 100/0, 77.6/22.4, 69.2/30.8, 44.6/55.4, and 22.3/77.7 silicon to germanium atomic-percent ratios by the use of the radioisotope $^{71}\mathrm{Ge}$ and a thin-sectioning technique. As expected from the calculated, small, strain-energy contributions from the $^{71}\mathrm{Ge}$ impurities, the diffusion is similar to silicon self-diffusion for the silicon end member. Since the results fit an Arrhenius plot for the compositions and temperature ranges studied, activation energies and pre-exponentials were determined. These diffusion parameters indicate that the $^{71}\mathrm{Ge}$ diffusion is compatible with the monovacancy mechanism up to 70-at.% silicon in the SiGe alloys. For more silicon-rich material, the diffusion is quite analogous to the extended-defect mechanism previously suggested for high-temperature silicon self-diffusion.

Saturation capacitance of thin oxide MOS structures and the effective surface density of states of silicon

Abstract: The capacitance vs voltage curve of thin oxide (30–40 A) MOS structures in strong accumulation was studied. The results were interpreted in terms of equivalent surface density of state masses, which was found to be 0·2 m 0 for the silicon valence band and 0·06 m 0 for the conduction band, for both 111 and 100 surfaces. The experimental density of state masses were shown to be much lower than the bulk values. Equivalent density of states masses were calculated from a surface quantization model and in this case agreement with the experiments was obtained for the valence band only.

Stoichiometry of thin silicon oxide layers on silicon

Abstract: The composition of anodically and thermally grown silicon oxide layers was determined by backscattering and channeling measurements with 2.0‐MeV 4He+ ions. The oxide thickness was determined by ellipsometry and, for anodic films, the silicon removal rate was also determined by layer removal measurements. The surface layer consists of stoichiometric silicon dioxide plus a silicon‐rich transition layer between the substrate and the silicon dioxide. The number of silicon atoms in this layer was found to be 6 × 1015 atoms/cm2 (about three atomic layers).

Excess vacancy generation mechanism at phosphorus diffusion into silicon

Abstract: Phosphorus is diffused into silicon at 900 °C from a phosphorus‐doped silicon‐dioxide layer. Since a profile of phosphorus concentration is expressed by a function of x/t, where x is the distance from a surface and t the diffusion time, diffusion coefficients are determined by the Boltzmann‐Matano method. They are larger than the intrinsic diffusion coefficient and are dependent not only on the concentration (the concentration effect) but also on some unknown condition at a surface (the surface effect). The surface effect extends more than 20 μ deep into a bulk of silicon, and is stronger than the concentration effect. All of phosphorus atoms are located at substitutional sites. Diffusion‐induced dislocations are not found. A new mechanism for the generation of excess vacancies is suggested. The new mechanism consists of the following: (i) Phosphorus diffuses by a vacancy mechanism. The diffusion of phosphorus occurs only through the diffusion of E centers. (ii) When phosphorus atoms enter from a surface ...

Two-band conduction of amorphous silicon nitride

Abstract: A method is proposed for determining the electron and hole components of stationary current flowing through an MIS structure and the hole and electron components of the stationary current in an MNOS structure have been determined. It is shown that the experimental results may be explained by a two-band Si3N4 conduction model. A two-band Si3N4 impurity conduction model with silicon microcrystals is examined, the latter serving as Poole-Frenkel centres in the nitride volume as well as trapping and recombination centres in the regions close to the electrodes. [Russian Text Ignored].

Lattice parameter study of silicon uniformly doped with boron and phosphorus

Abstract: Powder and single-crystal X-ray techniques have been employed to obtain precise lattice parameters of silicon uniformly doped with boron or phosphorus. Good agreement is found between the two methods. Previous accurate determination of the CuKα1, effective wavelength has yielded λ=1.540621±0.000006 A. Particular care has been devoted to the chemical and electrical characterization of the alloys, whose maximum dopant concentrations were 8×1019 atoms cm−3 for P and 4.4×1020 atoms cm−3 for B.

Nozzles formed in monocrystalline silicon

Abstract: Method for producing a predetermined pattern of small size fluid nozzles of identical or different geometries in crystallographically oriented monocrystalline silicon or similar material utilizing anisotropic etching through the silicon to an integral etch resistant barrier layer heavily doped with P type impurities.

High Temperature Reactions in the Silicon‐Hydrogen‐Chlorine System

Abstract: The partial pressures of the gaseous species in equilibrium with solid silicon in the Si‐H‐Cl system are presented as a function of temperature for different Cl/H ratios and total pressures. Computations were performed using our recently determined value of . Experimental data concerning the deposition and dissolution of silicon over a temperature range of 1200°–1700°K are compared to the equilibrium data and general conclusions drawn about the probable reaction mechanisms involved, especially for decomposition of the compounds and . Particular emphasis is put on attempting to integrate the diverse body of experimental data that exists for silicon deposition from and mixtures at high temperatures.

Preparation of organically modified silicon dioxides

Abstract: Process for the preparation of modified, porous silicon dioxides by the hydrolytic polycondensation of tetraalkoxysilanes or polyalkoxysiloxanes in the heterogenous phase in the presence of an organoalkoxysilane.

Epitaxial Growth of Nickel Silicide NiSi2 on Silicon

Abstract: The formation of structures of nickel silicides on Si have been studied by the use of glancing angle X-ray diffraction, MeV4He+ backscattering, reflection electron diffraction and replica electron microscopy. By reacting evaporated Ni films with Si wafers in the temperature range of 200 to 800°C, we have found three Ni silicides. The phase Ni2Si starts to form at 200°C at the Si-Ni interface. Around 350°C, the phase NiSi grows from the Si-Ni2Si interface. The NiSi is stable in the temperature range of 350 to 750°C and above that it transforms abruptly to NiSi2. The disilicide grows epitaxially on (111), (110) and (100) surfaces of Si.

Correlation of core electron binding energies with charge distributions for compounds of carbon, silicon, and germanium

Abstract: Core electron binding energies for analogous compounds of carbon, silicon, and germanium have been measured by X-ray photoelectron spectroscopy in the gas phase. The chemical shifts have been correlated by the electrostatic potential equation using charge distributions from extended Huckel theory, CNDO/2, and an electronegativity equalization method. The data can be rationalized without any consideration p..pi -->..d..pi.. or p(pi)..-->..d(pi) in the silicon and germanium compounds.

The role of the metal-semiconductor interface in silicon integrated circuit technology

Abstract: A typical medium-scale integrated (MSI) circuit requires hundreds of metal-semiconductor (M–S) junctions that are utilized for rectification, interconnection of device elements, and termination to external circuits. Comparison has been made between two metallization technologies, based upon the possible metallurgical reactions with Si: (1) nonreactive, such as evaporated aluminum, and (2) reactive, such as PtSi. Ohmic and rectifying contacts have been contrasted on the basis of the dominant current conduction mechanisms at the M–S interface. Current transport has been characterized in terms of the height and thickness of the potential energy barrier arising from thermal equilibrium among charge carriers between dissimilar conductors. Thermionic emission of electrons and holes provides the first illustration of conduction over a thick potential barrier (≫100 A), resulting in a rectifying contact (Schottky barrier diode). Thus, Schottky diode currents are exponentially dependent upon potential barrier height and inverse temperature. The contrasting illustration deals with a thin barrier (≪100 A) that conducts electrons and holes by quantum mechanical tunneling and forms ohmic contacts with resistance controlled only by contact size and underlying silicon resistivity. The final section covers two possible problems associated with silicon integrated circuit (SIC) fabrication. In the first example, a layer of oxide, too thin to be visible by optical interference (<500 A), can prevent proper contact formation. A method of observation, which makes use of hydrostatic surface tension, has been presented with experimental results on SiO2 films. Successive etching has revealed a detection limit of 11–13 A. The second deleterious phenomenon to be treated is the electrical degradation of Schottky barrier rectification associated with nonplanar penetration of metals into silicon. The destruction of the planar M–S interface could result from either undesired alloy eutectics or metallic precipitation.

Fabrication and some applications of large-area silicon field emission arrays

Abstract: A method of fabricating large-area arrays of sharply-pointed field emitters at densities up to 1·5 × 10 5 per cm 2 from single crystal silicon wafers is described. The point emitters are formed by etch-undercutting a precision oxide pattern which is delineated on the silicon surface by projection photolithography. Observations indicate that emitters with very small tip dimensions in the 200Arange are formed. In the presence of an external electric field, such as produced by a voltage applied to a closely-spaced, planar anode, multiple-emitter arrays are shown to field-emit electrons uniformly over areas up to 3 cm dia. Two important applications currently being explored, are discussed: (1) High resistivity, p -Si has been utilized to develop experimental field emission photocathodes with which field emission imaging has been demonstrated. These photoemitters exhibit very high photo-sensitivities at visible and near i.r. wavelengths. For example, at 0·86 μm, the measured quantum efficiency is 25 per cent which is about five-times higher than the red-sensitive S-20 photocathode and comparable to the highest reported sensitivities of the III–V photosurfaces; (2) N -type emitter arrays show considerable promise as high current, cold cathodes and total emission currents of 1/4 A from 1 cm 2 areas of 100 Ω-cm n -type emitters have been obtained. Measurements were made under pulse conditions because of anode dissipation considerations.

Method of forming doped dielectric layers utilizing reactive plasma deposition

Abstract: A doped oxide layer is formed on a semiconductor substrate utilizing reactive plasma deposition. Impurity doped thin film oxide deposits are formed by reacting suitable source gases in an RF plasma at low pressures and temperatures. Passing an dopant compound in vapor form with a suitable carrier gas, in combination with a flow of silicon hydride and an oxide vapor flow, provides a solid film of doped silicon dioxide on a surface when the gases are subjected to an RF discharge. The method features low temperature processing which is particularly advantageously utilized in providing a doped oxide layer as a diffusion source for a Group III-V substrate.

Silicon carbide diffusion furnace components

Abstract: Process tube, paddle, and boat for a semi-conductor diffusion furnace composed of a matrix of high purity sintered silicon carbide which is made impervious to gases by impregnation thereof with silicon metal which is 99.9% pure. The process tube, paddle and boat provide the ultra pure environment needed for semi-conductor production and are highly resistant to the degradative effect of a great number of high temperature heating cycles.

Vapor deposition method of forming low cost semiconductor solar cells including reconstitution of the reacted gases

Abstract: The disclosure relates to a method of upgrading metallurgical grade silicon to semiconductor grade for making low cost silicon devices and particularly solar cells. This is accomplished by passing conductive fibers such as graphite or the like which are compatible with the later processing steps through an area which is cooled below 700° C and which contains silicon difluoride and a proper N-type dopant. At these temperatures, the silicon difluoride gas will break down into pure silicon which will deposit onto the fiber with the formation of silicon tetrafluoride gas which is then recycled into a further chamber. In the further chamber, the gaseous silicon tetrafluoride is mixed with the impure metallurgical grade silicon at temperatures above 700° C to form the silicon difluoride gas which is then fed into the former chamber for deposition of pure silicon onto the continuously moving fibers of graphite or the like. A p-type layer can then be formed over the n-type layer in any standard manner, such as by then passing the coated fibers through a further reaction chamber wherein p-type dopant is diffused into the top surface of the n-type layer that has been formed. The dopants alternatively could be added in the gas stream of SiF 4 or the p-layer formed by ion implantation. In this way, relatively inexpensive p-n junction devices are formed without the requirement of purifying, cutting and polishing a silicon slice in the standard manner.

Deep depletion insulated gate field effect transistors

Abstract: A deep depletion insulated gate field effect transistor is made in a silicon layer on a sapphire substrate, so that its threshold voltage is relatively independent of the thickness of the silicon layer. The silicon layer has two parts, namely, a lower part adjacent to the sapphire substrate which is relatively lightly doped, and an upper part, preferably formed by ion implantation, having a doping concentration on the order of about 2 × 10 15 atoms/cm 3 .