On the homogeneous chemistry of the thermal decomposition of methyltrichlorosilane : thermodynamic analysis and kinetic modeling

Equilibrium gas-phase calculations for the Si/C/Cl/H deposition system are performed over the range of conditions used to deposit silicon carbide (SiC) through the thermal decomposition of methyltrichlorosilane (MTS). The compounds that exist in significant quantities in the gas phase, and thus may influence significantly the chemistry of the process, as well as the main deposition precursors are identified. The effect of temperature, pressure, and initial composition of the reacting mixture on the equilibrium composition of the gas phase is determined, and process conditions that may lead to stoichiometric silicon carbide films are suggested. Based on the results of the equilibrium calculations, a kinetic model for the homogeneous chemistry of the decomposition of MTS is proposed. Several reaction sequences leading to the generation of carbon and silicon deposition precursors are considered and their effects on the chemistry of the system are examined. Finally, the mechanism is incorporated into the reaction and transport model of a plug flow hot-wall reactor and the overall model is used to obtain the spatial variation of the composition of the gas phase under conditions typically encountered in chemical vapor deposition reactors.