Published online by Cambridge University Press: 21 February 2011
An interstitial model is developed to quantitatively account for the anomalous effects which accompany the diffusion of phosphorus in silicon from high surface concentrations. Phosphorus is assumed to diffuse as both a positively charged (intrinsic diffusion) and an uncharged interstitial (high concentration case). Silicon is assumed to diffuse as both an uncharged (instrinsic) and a negatively charged interstitial (high phosphorus concentrations). The effect of internal fields on charged species is included. An excellent fit is found with published experimental data if a surface enhancement factor, analogous to that for the case of oxidation enhancement, is used. Flat-top diffusion is modelled by assuming the formation of a dislocation array, which alters the point defect equilibria.