A General Correction to Surface Reaction Models Based on Reactive Sticking Coefficients

Abstract

AbstractFollowing the work of Coltrin et al. (Surface Chemkin III, Reaction Design, San Diego 1996), many CVD models express the rate of surface reactions as the molecular flux into the surface multiplied by a reactive sticking coefficient and a correction factor that was derived by Motz and Wise (J. Chem. Phys. 1960, 32, 1893). According to Motz and Wise, this factor is only valid for small reactive species concentrations, a condition that is not generally fulfilled in CVD processes. Nevertheless, it is widely used in CVD modeling.In the present study, the direct simulation Monte Carlo (DSMC) method was used to determine the deviation from this theory for more general CVD process conditions. The results show that the deviation increases with increasing reactive sticking coefficient and reactant mass fraction, and a significant deviation from the theory of up to 45 % was found. A fitted correlation is presented to predict this deviation using the sticking coefficient and the reactant mass fraction for cases with a reactant mass fraction near the surface up to (approximately) 99 %.