A Study of Predominated Pathway of Initial Processes in Chemical Vapor Deposition of Silicon-Carbide from Methyltrichlorosilane and Hydrogen System

The initial pathways in the CVD process of preparing silicon carbides with CH3SiCl3-H2 precursors was searched theoretically, which involves 21 well-defined transition states. The geometries of the species were optimized by employing the B3PW91/6-311G(d,p) method. The energy barriers and the reaction energies were evaluated with the accurate model chemistry method at G3(MP2) level after a non-dynamical electronic correlation detection. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K and 1200 K for all the possible elementary reactions, including both direct decomposition and the radical attacking dissociations for MTS were reported. The energies at any temperature could be derived classically by using the analytical heat capacities. It was found that the free radical reactions have clearly kinetic ascendency to be the most efficient decomposition pathway.