Thermal oxidation of polycrystalline silicon films

Abstract

In order to study the oxidation rate of polycrystalline silicon, thin polycrystalline films deposited at 650°C and thicker films deposited at 1020° and 1100°C were oxidized under conditions corresponding to both the reaction-rate-limited and diffusion-limited cases. The apparent oxidation rate of polycrystalline silicon was found to be somewhat less than that of single-crystal silicon but greater than that of single-crystal silicon. The differences observed are attributed to the varying oxidation rates of the differently oriented grains in the polycrystalline samples. Both optical and replica photomicrographs confirm this hypothesis. If the effect of grain orientation must be avoided in a certain application, oxidations should be carried out under diffusion-limited conditions (e.g. 1200°C), where the oxidation rates are approximately the same for single-crystal and polycrystalline silicon.