Thermodynamic analysis of gas phase chemistry in hot wire chemical vapor deposition of a-Si:H and μc-Si:H

Gas phase reactions amongst filament-generated radicals play a crucial role in growth and properties of films deposited by hot wire chemical vapor deposition (HWCVD) technology. Gas phase species of interest are SiH4, H2, Si, H, SiH3, SiH2 and SiH. Partial pressures of these species for different sets of deposition conditions have been determined from the standard Gibbs free energy data. Equilibrium concentrations of the film forming precursors have been determined. The effect of the various process parameters on the equilibrium concentration of the precursors has been studied. H, Si and SiH are found to be the dominant species in gas phase above a filament temperature of 2300 K. However SiH3 and SiH2 concentration peaks are between 1900 and 2300 K, of the filament temperature.