Numerical modeling of silicon oxide particle formation and transport in a one-dimensional low-pressure chemical vapor deposition reactor

A numerical model is presented for particle formation and transport during low-pressure chemical vapor deposition of silicon dioxide films from silane and oxygen. A detailed chemical kinetics approach was used to model silicon oxide clustering that leads to homogeneous nucleation. A moment-type aerosol dynamics model was developed, which includes particle growth by surface reactions and coagulation, and particle transport by convection, diffusion and thermophoresis, assuming a lognormal particle size distribution function. A chemical clustering mechanism was coupled to the aerosol dynamics model in an axisymmetric stagnation-flow reactor. Simulations were conducted to predict steady-state spatial distributions of major particle characteristics such as particle concentration, diameter and volume fraction. The effects of various system parameters were assessed for conditions around 1.5 Torr(200 Pa), 800°C, 200 sccm and an inlet oxygen-to-silane ratio of 20. Model predictions are shown to be in good agreement with experimental data and indicate that, unlike the case of particle formation in silane pyrolysis, the results are relatively insensitive to temperature. On the other hand, we observe a large sensitivity to pressure change, which is corroborated by experiment.