A consideration of the effect of the thermal boundary layer on CVD growth rates

Abstract

In deriving theoretical transport controlled growth rates for CVD processes the effect of the temperature gradient close to the reaction surface is usually neglected in order to obtain a simple analytical treatment, and values of gas properties corresponding to some average temperature are taken. A simple consideration of the differential equations for fluid flow and heat and mass transfer shows that one might expect the steep temperature profile commonly encountered at a susceptor surface to lead to a considerable distortion of the diffusion boundary layer and hence of the growth rate. Nevertheless, the agreement between theory based on constant gas property conditions and experiment for various reactor geometries is usually reasonable. In this paper we present an analysis to show why this is so.