Thermodynamic study on the chemical vapor deposition of silicon nitride from the SiCl4–NH3–H2 system

The gas-phase reaction thermodynamics in the chemical vapor deposition (CVD) process of preparing silicon nitride with the precursors of SiCl4–NH3–H2 was investigated with a relatively complete set of 161 species, in which the thermochemistry data were calculated with accurate model chemistry at G3(MP2) and G3//B3LYP levels combined with standard statistical thermodynamics. The data include the heat capacities, entropies, enthalpies of formation, and Gibbs energies of formation. Two condensed phase, silicon nitride (Si3N4) and silicon (Si) were taken into consideration. Based on these data, the distribution of the equilibrium concentration of the 161 species was obtained with the principle of chemical equilibrium. It was concluded that Si3N4 could be produced at the initial temperature of 300 K up to the temperature 1560 K, and the ideal deposition ratio r = SiCl4/(SiCl4 + NH3) for Si3N4 was found to be 0.5.