Development of a model for high precursor conversion efficiency pulsed-pressure chemical vapor deposition (PP-CVD) processing

The unsteady pulsed-pressure chemical vapour deposition (PP-CVD) technique offers an increase in process intensification over conventional CVD processes due to the high precursor utilisation efficiency. A numerical model of the movement of precursor particles in the process is developed to study the high efficiencies observed experimentally in this process. The modelling procedures were verified via a study of velocity persistence in an equilibrium gas and through direct simulation Monte Carlo (DSMC) modelling of unsteady self-diffusion processes. The results demonstrate that in the PP-CVD process the arrival time for precursor particles at the deposition surface is much less than the reactor pump-down time, resulting in high precursor conversion efficiencies. Higher conversion efficiency was found to correlate with smaller size carrier gas molecules and moderate reactor peak pressure.