Electrical instabilities in SiO2 films under high fields at elevated temperatures have been widely attributed to mobile ionic impurities, with sodium suspected as the most important ion. Phosphate glass treatments on SiO2 are known to have a stabilizing effect. This paper reports neutron activation experiments to determine sodium contamination on and in steam‐grown SiO2 films and also diffusion and drift experiments with tracer sodium. Phosphate glass‐treated SiO2 films were included in the samples. SiO2 films grown and handled under various conditions had sodium densities of 7×1011 normalto 3×1014 normalatoms/cm2 , which could be easily removed or exchanged by washing and light etching. Densities remaining inside the 6000Aå films after washing and light etching were ⋜4×1011–4×1012/cm2 .Tracer diffusions into SiO2 at 600°C produced profiles which were high near the surface and lower through the interior of the film, similar to those observed by neutron activation for unintentional sodium contamination. Phosphate glass layers on SiO2 absorbed and stopped the sodium under similar conditions. With an applied field at elevated temperature (+4v, 1 min, 400°C) tracer sodium drifted through an SiO2 film under gold dot electrodes, piled up at the normalSi‐SiO2 interface, and carried a substantial part of the charge transported. There was no detectable diffusion in uncharged areas. A layer of phosphate glass applied over an SiO2 film absorbed sodium and prevented it from drifting into the SiO2 film under the gold dots.

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If the native oxide layer is sufficiently thin, the oxidation process is controlled by reaction rate at the GaAs surface (12). Note that holes at the GaAs surface produce broken bonds of GaAs which can react with oxygen atoms, resulting in oxidation of GaAs. Therefore the thickness could be related to the hole concentration at the GaAs surface.The permittivity of the native oxide layer on GaAs, which is dependent on oxidation processes, was regarded as a parameter in the present analysis. The optical refractive indexes are 1.56 for the thermal oxide of GaAs at 5460A and 1.8 ~ 1.9 (1, 10) for the native oxide. The electrostatic permittivity for both the oxides should be correspondingly different in the similar range. In the present study, an electrostatic permittivity of 5.4 (9) for the thick anodic oxide film was employed for calculating the oxide thickness. The validity of this permittivity is supported by the fact that the optical refractive index for thin native oxide is almost identical to that for thick anodic oxide (i, I0). The relationship 6 cc n-V= is well satisfied, even if the actual permittivity is slightly different from 5.4.In conclusion, it has been clarified that the chemical activity of n-GaAs surface for oxidizing agent is remarkably enhanced with lowering of the bulk electron concentration.

A macroscopic time dependent electrical conduction model for thin phosphosilicate glass films Statistical approach to parameter study of stress in multilayer films of phosphosilicate glass and silicon nitride J. Vac. Sci. Technol. A 9, 2497 (1991); 10.1116/1.577263Comparative study of phosphosilicate glass on (100) silicon by furnace and rapid isothermal annealing

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