Diffusion of Impurities into Evaporating Silicon

Abstract

Steady‐state impurity distributions are produced when impurities are diffused into a piece of silicon, the surface of which is evaporating. The moving boundary condition results under steady state in an exponential impurity distribution. The silicon evaporation rate has been determined for temperatures between 1200 and 1325°C from weight loss measurements. No difference in the evaporation rate from various crystallographic planes could be observed from the diffusion technique but flat‐bottomed etch pits which formed on surfaces closely orientated to the (111) plane indicated that this plane is probably the most stable. Single diffusions as well as simultaneous double diffusions of phosphorus and gallium into silicon have been studied.