Formation of stacking faults and enhanced diffusion in the oxidation of silicon

Abstract

The phenomena of the formation of stacking faults and the enhanced diffusion during the oxidation of silicon are shown to be closely related and to have a common cause. A model is presented which at once can consistently explain various aspects of both phenomena; in particular, it is capable of explaining the crystal-orientation dependence of these phenomena and the parabolic growth of stacking faults. The model envisages a small incompleteness (∼ 10−3) of oxidation, producing silicon interstitials. A concept is introduced that these excess interstitials, as they supersaturate the lattice, will undergo surface regrowth. The rate of interface regrowth is proportional to the density of surface kinks, which is in turn dependent on the surface orientation. The dependence is described. Quantitative analyses are given for the excess interstitials, the growth of stacking faults, and the enhancement of diffusion. The analyses also show that the stacking-fault embryos are formed within a very short time of the start of oxidation, usually less than 1 sec, consequently leading to uniform stacking-fault size. The occasionally observed variation in the size of bulk stacking faults is attributed to a continuous formation of stacking-fault nuclei (e.g., oxide clusters and precipitates). The absence of a surface regrowth would predict a 1/4 power law of stacking-fault growth, in contradiction of the experiments.