The steady-state model for coupled defect-impurity diffusion in silicon

Abstract

We extend and generalize our earlier model which was proposed to explain tails in the diffusion profiles of high-concentration boron and phosphorus in silicon. Our quasi-steady-state approach is generalized here to include both vacancies (V) and interstitials (I) at equivalent levels. I-V recombination is regarded as near local equilibrium, occurring through reactions of the defects with defect-impurity pairs. This approach leads to important details such as the well-known plateau, kink, and tail in high-surface-concentration P diffusions in Si, and to the less well-recognized tails in B as well, with no additional ad hoc assumptions. Our extended model, in its simplest form, allows a more complete and less restrictive treatment than the usual models of Au in-diffusion in Si. An important advantage is the direct inclusion of these defect-impurity interactions and the resulting gradients in the defect concentrations, which are ignored in even the latest versions of popular process simulation programs, such as suprem iv.