Thermal Oxidation of Heavily Phosphorus‐Doped Silicon

Abstract

The effects of high substrate phosphorus impurity levels on the kinetics of thermal oxidation of <111> oriented silicon have been studied for a dry oxygen ambient in the temperature range 800°–1100°C. The observed enhanced oxidation rates with phosphorus doping levels ≥1019/cm3 are found to be consistent with a simplified interpretation of the linear‐parabolic oxidation model together with phosphorus redistribution effects. The linear rate constant increases substantially at all temperatures, implying significant change in the interface reaction rate, though apparently with only slight effect on the associated activation energy. The parabolic rate constant increases somewhat at lower temperatures, indicating a finite change in oxidant diffusion through the oxide, possibly via an additional diffusion mechanism at high phosphorus concentrations, with reduced activation energy. Reasonable closed‐form approximations to these phosphorus concentration dependencies of the oxidation rate constants are described.