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Electrolytic oxidation of semiconductor surfaces
World Abstracts on Microelectronics and Reliability
Preparation of highly photoconductive amorphous silicon by rf sputtering. T. D. MOUSTAKAS, D. A. ANDERSON and WILLIAM PAUL. Solid St. Communs 23, 155 (1977). The photoconductivity of hydrogenated rf sputtered amorphous Si has been determined as a function of the partial pressure of hydrogen in the sputtering gas and of deposition temperatures up to 450°C. The data can be used to choose conditions for preparing material with large photoresponse and small defect state density. Etude des processns de depot du silicium en phase gazense. J. P. DUCHEMIN. Revue Technque Thomson-CSF 9, (1) (March 1977). (In French.) This study deals with the mechanism of silicon deposits from Sill4, sin2c12, SiHa and SIC14 sources in a hydrogen atmosphere. Most of the experimenting was done at atmospheric pressure in a vertical system (AMV 800). The depositing rates were observed on single-crystals (111) as a function of the deposit parameters (temperature, source, carrier-gas flow rate, type of injector). The findings were compared with a gas analysis based on various methods (gaseousphase chromatography, infrared absorption, mass spectrography). The migration properties in the boundary layer are studied by analyzing the molar fractions of the various migrating species as a function of distance above the depositing surface. The coefficients of diffusion in the gaseous phase of the SiH2C12, SiHCIa, SiCI,, source species were measured on contact with the depositing surface. Conduction studies in silicon nitride; dark currents and photocurrents. D. J. DIMARIA and P. C. ARNETT. IBM Jl Res. Dev. p. 227 (May 1977). Dark conduction and photoconduction phenomena in amorphous, stoichiometric Si3N, films incorporated into metal-silicon nitride-silicon (MNS) structures are studied in detail. Results demonstrating the importance of hole conduction in SiaN, thin films are presented. The importance of trapped space charge injected from the contacts is shown in an analysis of the effects of Si3N, thickness and the choice of gate metal on conduction. Contact effects that are apparent in the current characteristics of thin SiaN, layers become dominated by bulk conduction mechanisms as the silicon nitride film increases in thickness. Optical interference effects in photoconduction are used to determine the origin of photocarriers. On the nature of photoelectric fatigue in semiconductors. S. PETROSJAN, A. SH1Kand A. YA VUL'. Solid St. Communs 23, 385 (1977). A model is proposed which explains slow processes of photoelectric fatigue that occur in some semiconductors. The model presupposes the presence of inhomogeneties in the form of high-resistive inclusions containing electron traps in the semiconductor. The fatigue effect consists in the trapping of slow photoelectrons and as a result, in the decrease of life time due to the increase of hole concentration on recombination centres. The effect of low-temperature annealing upon the structure and electrical characteristics of rectifying nickel-silicon contacts. O. P. KANCUKOVSKIJ,S. B. KAZIMIRSKIJ,L. V. MOROZ and V. A. PRESNOV. Electron Technol., Warsaw 10, (2) 37 (1977). The paper presents the results of the investigations of the effect of low-temperature annealing in vacuum upon the electrical characteristics and interfacial parameters of Ni-nSi surface-barrier junctions: forward and reverse I - V characteristics, non-ideality coefficient, barrier height. The interface layer thickness and the surface state density at the Si-SiO2-Ni interface are estimated prior to and following the thermal treatment. It is demonstrated that an increase of the barrier height of a Si-Ni surface barrier structure in the course of annealing is associated with a change of the surface state density and the interface layer thickness at the Ni-nSi contact.
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Met~table impurity bands: conduction in Sil_xCo x and Sil_xNix ahoy films. M. M. COLLVER. Solid St. Communs 23, 333 (1977). Conductivity data for silicon-nickel and silicon-cobalt films prepared by electron beam evaporation shows a hopping conduction at metal concentrations in the range of 1 to 6 at.%. A semiconductor-to-metal transition was observed at metal concentrations of 15 at.% Co for Si-Co and 13 at.°~, Ni for Si-Ni films. Impurity bands in semiconductors in arbitraly magnetic fields. S. D. JoG and P. R. WALLACE.Solid St. Communs 24, 225 (1977). For a random distribution of impurities we study the shift of the centre of the impurity band and its width as a function of magnetic field. This is done by calculating the first and second moments of the density of states in a tight binding approximation. Indication of the presence of acceptor states around the Fermi level of amorphous silicon. AHMEDKHAIRYABOULSEOUND. Solid St. Communs 24, 303 (1977). A junction was grown by sputtering of silicon on a single crystal of high resistivity n-type silicon. The reverse bias V-I characteristics followed. Fowler-Nerdheim model with a sudden change in the slope at 0.4 volt indicating an increase in the barrier height. This is attributed to tunneling of extra electrons from the bottom of the conduction band of the substrate to the acceptor traps that face each other at this bias. The dopant density and temperature dependence of electron mobility and resistivity in n-type silicon. SHENG S. LI and W. ROBERT THURBER. Solid-St. Electron. 20, 609 (1977). Traditional analysis of electron mobility in n-type silicon neglects the effect of electron-electron scattering in the mobility calculations. As a result, theory fails to conform with experiment when dopant density exceeds 2 x 1016 cm-3. In this work, an improved theoretical model for computing mobility and resistivity as functions of dopant density and temperature has been developed for n-type silicon. The model has been applied to phosphorus-doped silicon for dopant densities from 1013 to 10tgcm -3, and temperatures between 100 and 500 K. The mobility was calculated analytically by appropriately combining lattice, ionized impurity and neutral impurity scattering contributions. The effect of electron-electron scattering was incorporated empirically for dopant densities greater than 2 x 1016cm -3. Additionally, the anisotropic scattering effect was included in the mobility formulations. Resistivity measurements on seven phosphorus-doped silicon wafers with dopant densities from 1.2 x 101. to 2.5 x 10facto -a were carried out for temperatures from 100 to 500 K. Electron mobility at 300 K was deduced from resistivity and junction C-V measurements for dopant densities from 1014 to 1018 cm 3 Agreement between theoretical calculations and experimental data for both electron mobility and resistivity of phosphorus-doped silicon was within _+7% in the range of dopant densities and temperatures studied. Electrolytic oxidation of semiconductor surfaces. H. U HARTNAGEL. Electrocomp. Sci. Technol. 3, 225 (1977). Recently a greater understanding of the physics and chemistry of anodic oxide growth on III-V compound semiconductors has become available. These details are reviewed and critically assessed. With the data available now new device applications can be considered. Electroforming, switching and memory effects in oxide thin films. D. P. OXLEY.Electrocomp. Sci. Technol. 3, 217 (1977). Experiments on electroforming of Metal-Oxide-Metal thin film sandwiches which have been electroformed to exhibit voltage-controlled negative resistance are summarized and an outline of recent evidence in favour of localized or filamentary conduction is given.
Preparation of highly photoconductive amorphous silicon by rf sputtering. T. D. MOUSTAKAS, D. A. ANDERSON and WILLIAM PAUL. Solid St. Communs 23, 155 (1977). The photoconductivity of hydrogenated rf sputtered amorphous Si has been determined as a function of the partial pressure of hydrogen in the sputtering gas and of deposition temperatures up to 450°C. The data can be used to choose conditions for preparing material with large photoresponse and small defect state density. Etude des processns de depot du silicium en phase gazense. J. P. DUCHEMIN. Revue Technque Thomson-CSF 9, (1) (March 1977). (In French.) This study deals with the mechanism of silicon deposits from Sill4, sin2c12, SiHa and SIC14 sources in a hydrogen atmosphere. Most of the experimenting was done at atmospheric pressure in a vertical system (AMV 800). The depositing rates were observed on single-crystals (111) as a function of the deposit parameters (temperature, source, carrier-gas flow rate, type of injector). The findings were compared with a gas analysis based on various methods (gaseousphase chromatography, infrared absorption, mass spectrography). The migration properties in the boundary layer are studied by analyzing the molar fractions of the various migrating species as a function of distance above the depositing surface. The coefficients of diffusion in the gaseous phase of the SiH2C12, SiHCIa, SiCI,, source species were measured on contact with the depositing surface. Conduction studies in silicon nitride; dark currents and photocurrents. D. J. DIMARIA and P. C. ARNETT. IBM Jl Res. Dev. p. 227 (May 1977). Dark conduction and photoconduction phenomena in amorphous, stoichiometric Si3N, films incorporated into metal-silicon nitride-silicon (MNS) structures are studied in detail. Results demonstrating the importance of hole conduction in SiaN, thin films are presented. The importance of trapped space charge injected from the contacts is shown in an analysis of the effects of Si3N, thickness and the choice of gate metal on conduction. Contact effects that are apparent in the current characteristics of thin SiaN, layers become dominated by bulk conduction mechanisms as the silicon nitride film increases in thickness. Optical interference effects in photoconduction are used to determine the origin of photocarriers. On the nature of photoelectric fatigue in semiconductors. S. PETROSJAN, A. SH1Kand A. YA VUL'. Solid St. Communs 23, 385 (1977). A model is proposed which explains slow processes of photoelectric fatigue that occur in some semiconductors. The model presupposes the presence of inhomogeneties in the form of high-resistive inclusions containing electron traps in the semiconductor. The fatigue effect consists in the trapping of slow photoelectrons and as a result, in the decrease of life time due to the increase of hole concentration on recombination centres. The effect of low-temperature annealing upon the structure and electrical characteristics of rectifying nickel-silicon contacts. O. P. KANCUKOVSKIJ,S. B. KAZIMIRSKIJ,L. V. MOROZ and V. A. PRESNOV. Electron Technol., Warsaw 10, (2) 37 (1977). The paper presents the results of the investigations of the effect of low-temperature annealing in vacuum upon the electrical characteristics and interfacial parameters of Ni-nSi surface-barrier junctions: forward and reverse I - V characteristics, non-ideality coefficient, barrier height. The interface layer thickness and the surface state density at the Si-SiO2-Ni interface are estimated prior to and following the thermal treatment. It is demonstrated that an increase of the barrier height of a Si-Ni surface barrier structure in the course of annealing is associated with a change of the surface state density and the interface layer thickness at the Ni-nSi contact.
361
Met~table impurity bands: conduction in Sil_xCo x and Sil_xNix ahoy films. M. M. COLLVER. Solid St. Communs 23, 333 (1977). Conductivity data for silicon-nickel and silicon-cobalt films prepared by electron beam evaporation shows a hopping conduction at metal concentrations in the range of 1 to 6 at.%. A semiconductor-to-metal transition was observed at metal concentrations of 15 at.% Co for Si-Co and 13 at.°~, Ni for Si-Ni films. Impurity bands in semiconductors in arbitraly magnetic fields. S. D. JoG and P. R. WALLACE.Solid St. Communs 24, 225 (1977). For a random distribution of impurities we study the shift of the centre of the impurity band and its width as a function of magnetic field. This is done by calculating the first and second moments of the density of states in a tight binding approximation. Indication of the presence of acceptor states around the Fermi level of amorphous silicon. AHMEDKHAIRYABOULSEOUND. Solid St. Communs 24, 303 (1977). A junction was grown by sputtering of silicon on a single crystal of high resistivity n-type silicon. The reverse bias V-I characteristics followed. Fowler-Nerdheim model with a sudden change in the slope at 0.4 volt indicating an increase in the barrier height. This is attributed to tunneling of extra electrons from the bottom of the conduction band of the substrate to the acceptor traps that face each other at this bias. The dopant density and temperature dependence of electron mobility and resistivity in n-type silicon. SHENG S. LI and W. ROBERT THURBER. Solid-St. Electron. 20, 609 (1977). Traditional analysis of electron mobility in n-type silicon neglects the effect of electron-electron scattering in the mobility calculations. As a result, theory fails to conform with experiment when dopant density exceeds 2 x 1016 cm-3. In this work, an improved theoretical model for computing mobility and resistivity as functions of dopant density and temperature has been developed for n-type silicon. The model has been applied to phosphorus-doped silicon for dopant densities from 1013 to 10tgcm -3, and temperatures between 100 and 500 K. The mobility was calculated analytically by appropriately combining lattice, ionized impurity and neutral impurity scattering contributions. The effect of electron-electron scattering was incorporated empirically for dopant densities greater than 2 x 1016cm -3. Additionally, the anisotropic scattering effect was included in the mobility formulations. Resistivity measurements on seven phosphorus-doped silicon wafers with dopant densities from 1.2 x 101. to 2.5 x 10facto -a were carried out for temperatures from 100 to 500 K. Electron mobility at 300 K was deduced from resistivity and junction C-V measurements for dopant densities from 1014 to 1018 cm 3 Agreement between theoretical calculations and experimental data for both electron mobility and resistivity of phosphorus-doped silicon was within _+7% in the range of dopant densities and temperatures studied. Electrolytic oxidation of semiconductor surfaces. H. U HARTNAGEL. Electrocomp. Sci. Technol. 3, 225 (1977). Recently a greater understanding of the physics and chemistry of anodic oxide growth on III-V compound semiconductors has become available. These details are reviewed and critically assessed. With the data available now new device applications can be considered. Electroforming, switching and memory effects in oxide thin films. D. P. OXLEY.Electrocomp. Sci. Technol. 3, 217 (1977). Experiments on electroforming of Metal-Oxide-Metal thin film sandwiches which have been electroformed to exhibit voltage-controlled negative resistance are summarized and an outline of recent evidence in favour of localized or filamentary conduction is given.