Effect of temperature on the chemical vapor deposition of silicon carbide coatings

The effect of temperature(850-1350°C) on deposition rates, reactant depletions, surface morphologies and microstructures was investigated in chemical vapor deposition(CVD) of silicon carbide coatings from methyltrichlorosilane and hydrogen system at constant pressure and flow rates. The in-situ kinetics by magnetic suspension balance shows that there are four rate-limiting mechanisms: the surface reactions in a region(<1000°C); the inhibition of HCl from deposition rate in b region(1000-1050°C); the combination of surface reactions and mass transfer in c region (1050-1300°C), and the reactant depletions in d region. The different rate-limiting mechanisms result in different coating morphologies. The combination of decreased concentrations of carbon-containing, silicon-containing species increased, HCl and decomposition of MTS causes the reactants depletion. The XRD results show that coatings consist of porlycrystal β-SiC. The C/SiC is gradually close to 1 with the increasing temperature.