Kinetic laws of the chemical process in the CVD of SiC ceramics from CH₃SiCl₃-H₂ precursor

Abstract

On the basis of growth rate measurements as a function of temperature and initial gas phase composition, the kinetic process of the CVD of silicon carbide from MTS-H2 is investigated, particularly under conditions of rate-control by the chemical reactions. Within specific ranges of dilution ratio 3 ≤ α ≤ 5 KPa and total pressure 3 ≤ P ≤ 10 KPa, two kinetic regimes are brought out depending on the temperature. At about 825°C, the deposition of SiC could be rate-limited by the homogeneous decomposition of MTS with an activation energy higher than 300 kJ.mol-1 and an apparent reaction order of 2.5 with respect to MTS. At about 925°C, surface reactions could control the overall kinetic process with an activation energy of only 160 kJ.mol-1 and an inhibitor chemisorption of Cl species which involves a negative reaction order with respect to HCl.