CHEMICALLY VAPOR-DEPOSITED COATINGS OF SILICON-CARBIDE ON PLANAR ALUMINA SUBSTRATES

Some preliminary studies on chemical vapour deposition of silicon carbide on oxide substrates such as alumina are reported. Mixtures of silicon tetrachloride, methane and hydrogen, trichloromethylsilane and hydrogen, or dichlorodimethylsilane and hydrogen are used as precursor systems and the conditions for the deposition of single-phase beta-SiC are examined. The experimental results obtained are in agreement with those predicted by equilibrium thermodynamic calculations for the Si-C-H-Cl system. Chemical reaction between the SiCl4-CH4-H2 and the TMS-H2 gases and the oxide substrate is observed leading to weight loss of the substrates. The solid-gas reactivity decreases in the order silicon tetrachloride > dichloromethylsilane > dichlorodimethylsilane. The last of these seems to be the most suitable halosilane precursor for chemical vapour deposition of silicon carbide on oxide substrates in general and on alumina and mullite substrates in particular.