The oxidation of shaped silicon surfaces

Nonplanar silicon surfaces were prepared and oxidized at 900~176 and the oxide morphology was studied by transmission electron microscopy of thin sections. A 30 % decrease in oxide thickness at silicon step edges following 900 ~ and 950 ~ wet oxidation is attributed to the effect of locally compressive intrinsic stress within the oxide on the solubilit: ~ of oxygen. Oxidation inhibition becomes less at higher temperatures due to the relief of stress (during growth) by viscous flow of the oxide. Our present understanding of the mechanism for the oxidation of silicon is based on oxidation studies on flat silicon wafers or bars. These studies have shown that oxidation behavior can be represented by the ex-pression (1) x 2+Ax=B ( t+T) [1] where x is the oxide thickness, t is the oxidation time, and T is an initial oxidation period in which oxide growth occurs in a manner that is not well understood. For short oxidation times it has been found that oxida-tion follows a rate law B x---- (t §,) [2