Effect of Chemical Vapor Deposition Process Parameters on Graded SiC-SiO2 Coating

Abstract

The effect of the chemical vapor deposition (CVD) process parameters on the structure of graded SiC-SiO2coating was studied through thermodynamic computation. The addition of enough hydrogen into the carrier gas is necessary for the synthesis of the graded SiC-SiO2coating. Both high deposition temperature and low deposition temperature make the change of the composition of the coating abrupt with the change of the composition of CVD atmosphere, which is harmful to the process control of the coating. A low concentration of reactants is preferred according to the thermodynamic computation but the deposition rate is too low at a low concentration of reactants. When hydrogen is the carrier gas and the concentration of SiCl4is between 1 – 2 vol%, the graded SiC-SiO2coating with a suitably graded distribution of SiC and SiO2can be easily obtained through gradually changing the flow rate ratio of methane and water vapor at 1100 - 1200 °C.