The Oxidation Rate Dependence of Oxidation‐Enhanced Diffusion of Boron and Phosphorus in Silicon

Abstract

Oxidation‐enhanced diffusion (OED) of boron and phosphorus has been found to vary with oxidation rate. The measurement technique uses a grating pattern of parallel nitride and oxide stripes on the silicon surface, which allows three different drive‐in conditions to be achieved on the same wafer, namely, inert and oxidizing conditions with two different oxidation rates. Because of the close proximity of the profiles diffused under different conditions on the wafers, the relative change in the diffusivity of dopants could be accurately determined by means of spreading resistance measurements. The results show that impurity diffusion in oxidizing ambients is enhanced and the enhancement clearly depends on oxidation rates, the higher the rate, the larger the enhancement. Oxidation‐enhanced diffusion is caused by the supersaturation of extrinsic point defects generated at the interface during oxidation. The present work indicates that the supersaturation is directly related to oxidation rate by a sublinear power‐law dependence, similar to that observed for the growth of oxidation‐induced stacking faults. The oxidation rate dependence is used as a basis to formulate a general model which explains the variation of OED under different oxidation conditions, namely, temperature, time, ambient, and pressure.