Model for defect-impurity pair diffusion in silicon

Abstract

A new model for impurity diffusion in silicon by a point defect-impurity pair mechanism is described. A pair of coupled, nonlinear, partial differential equations for the silicon self-interstitial and the impurity is derived and solved numerically. The familiar kink and tail of phosphorus and, to a lesser extent, boron diffused profiles arise naturally from the solution. The coupling between defect and impurity becomes smaller at high temperatures and at low impurity concentrations, in agreement with experimental observations. The transient buildup of the defect concentration may have implications for models of rapid thermal processes.