High-pressure oxidation for thin gate insulator process

High-pressure oxidation of silicon was performed at a pressure of 8.9 kg/cm
²
at a temperature range of 650 to 950°C. The oxidation temperature dependence of the film density, refractive index, chemical etching rate, and residual stress was measured. The film density of the oxide film was found to increase with decreasing oxidation temperature. The refractive index of the film also increased with decreasing oxidation temperature. The residual stress was found to be dependent on the oxidation temperature. The dielectric breakdown strength of the oxide film was measured by the voltage ramping method. The defect density of the oxide film calculated from the distribution of dielectric breakdown strength slightly decreased with decreasing oxidation temperature. The surface-state density of the oxide film was about 1.1 × 10
¹¹
cm
^-2
throughout the oxidation temperature range. The oxide grown on a doped polysilicon layer at a temperature of 750°C was five times as thick as the oxide simultaneously grown on the silicon substrate. The high-pressure and low-temperature oxidation was applied to the fabrication process of a device with a double polysilicon layer structure.