Effect of diluent gases on the growth behavior of CVD SiC films with temperature

Silicon carbide films have been grown onto graphite substrates by low pressure chemical vapor deposition using MTS (CH₃SiCl₃) as a source precursor and H₂ or N₂ as a diluent gas. The experiments were performed at fixed conditions of a flow rate of 100 sccm for each MTS and carrier gas, a flow rate of 300 sccm for diluent gas addition, and a total pressure of 5 torr. The effect of temperature from 900 °C to 1350 °C and the alteration of diluent gas species on the growth rate and structure of deposits have been studied. The experimental results showed that the deposition rate increased with increasing deposition temperature irrespective of diluent gases and reactant depletion effect increased especially at H₂ diluent gas ambient. At MTS-H₂ system, the deposition mechanism changed from chemical reaction to mass transfer controlled reaction with temperature. Otherwise, For MTS-H₂-N₂ system, surface chemical reaction controlled the growth process at whole deposition temperature ranges. For N₂ addition, surface morphology of leaf-like structure appeared, and for H₂, faceted structure at 1350 °C. The observed features were involved by crystalline phase of β-SiC and surface composition with different gas ambient.