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

Oxidat ion-enhanced diffusion (OED) of boron and phosphorus has been found to vary with oxidation rate. The measurement technique uses a grat ing pattern of paral le l nitr ide and oxide stripes on the silicon surIace, which allows three different dr ive- 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 relat ive change in the diffusivity of doPants could be accurately de-termined by means of spreading resistance measurements. The results show that impur i ty diffusion in oxidizing ambients is enhanced and the enhance-ment clearly depends on oxidation rates, the higher the rate, the larger the enhancement. Oxidat ion-enhanced diffusion is caused by the supersaturat ion f extrinsic point defects generated at the Si-SiO2 interface during oxidation. The present work indicates that the supersaturat ion is directly related to oxidation rate by a subl inear power- law dependence, s imi lar to that ob