Thermodynamics investigation of the gas-phase reactions in the chemical vapor deposition of silicon borides with BCl3–SiCl4–H2 precursors

Abstract

The gas-phase reaction thermodynamics in the chemical vapor deposition (CVD) process of preparing silicon borides with the precursors of BCl3–SiCl4–H2 is investigated with a relatively complete set of 220 species, in which the thermochemistry data are 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 free energies of formation. Based on these data, the distribution of the equilibrium concentration of the 220 species is obtained with the principle of chemical equilibrium. BHCl2, SiHCl3, and BH2Cl are found to be the crucial intermediates. This work provides fundamental data for analyzing the thermochemistry of the CVD process of the BCl3–SiCl4–H2 system, which is instructive to optimize the input precursors and temperatures for controlling the composition of the condensed phase B, SiB6, and SiB14.