A Mathematical Model for Chemical Vapor Deposition Processes Influenced by Surface Reaction Kinetics: Application to Low‐Pressure Deposition of Tungsten

This paper reports on a mode for the simultaneous reaction kinetics and transport processes in chemical vapor deposition (CVD) reactors extended to treat deposition of materials that have a broad range of surface characteristics, e.g. sites with multiple dangling bonds and adsorbates with multiple bonding configurations. The model uses the nature of the surface to determine the elementary processes that can take place during growth. Rate constants for these processes are calculated from first principles using statistical thermodynamics, transition state theory, and bond dissociation enthalpies. In this way, deposition rates are determined without either assuming the reaction mechanism or arbitrarily choosing any kinetic parameter values. The utility of the approach is illustrated by modeling low-pressure CVD of tungsten from tungsten hexafluoride and hydrogen. The treatment considers 14 species and eight reactions in the gas together with 21 species and 65 processes at the surface.