Theoretical study on the SiH4−nCln (n = 0–4) reaction mechanisms for polysilicon production process

Abstract

Because of the lacking of rate coefficients of reactions in polysilicon production process, the reaction mechanisms of SiH4−nCln (n=0–4) in gas phase were investigated using quantum chemical calculations and transition state theory, which contained 20 species and 117 elementary reactions. By considering of the calculation amount and accuracy, the thermodynamic properties, including enthalpy of formation, entropy and heat capacity of the species were calculated using G3B3 method. The geometry optimization and vibrational frequencies of reactants, transition states, and products were determined at the B3LYP/6-311G(d,p) and MP2/6-311G(d,p) level, while energies were calculated using G3B3, G3MP2 and QCISD(T)/CBS method. The rate coefficients for the reactions without transition states were obtained by the canonical variational transition state theory (CVT), while the rate coefficients for the other reactions with saddle-point transition states were obtained by the conventional transition state theory (TST). The rate coefficients agree with available data from the literatures well. This research provided high accuracy thermodynamic and kinetic data for H–Si–Cl reaction system, which could be used for reactor optimization in polysilicon production.