THERMODYNAMIC STUDY OF THE CHEMICAL-VAPOR-DEPOSITION IN THE SI-B-C-H-CL SYSTEM

This paper presents the results of a thermodynamic study concerning the codeposition of phases of the silicon, boron and carbon system by a classical C.V.D. technique from an initial gaseous mixture composed of methyltrichlorosilane (MTS), boron trichloride (BCI3) and hydrogen. The thermodynamic approach developed here is specific in the sense that for the first time the non-stoichiometry of boron carbide is described from B4C up to B10C The Gibbs' energy of the solid solution phase is assumed to follow the sublattice model. A deposition diagram is determined as a function of the initial gas composition together with the equilibrium yields of the different gaseous and solid species. Finally, an interesting deposition domain could be chosen for future experiments of deposition on C/C, C/SiC and SiC/SiC composites.