An analytical model to account for the effects of gas phase reactions in CVD processes is presented. In this model a system with only two reactions, gas phase production of an intermediate and reaction of the intermediate on the surface of the substrate to form the film is considered. The reaction kinetics, convective and diffusive transport mechanisms are coupled to analyse the thickness distribution over the length of the reactor.
Theoretical deposition rate profiles in the direction of gas flow are shown with varying deposition temperatures and gas flow velocities for both surface and gas phase reaction controlled mechanisms. It has been shown that by analyzing the nature of the deposition rate profiles, the rate limiting step in a CVD process can be identified.