DEPLETION EFFECTS OF SILICON-CARBIDE DEPOSITION FROM METHYLTRICHLOROSILANE

The deposition rate of SiC on carbon-coated Nicalon fibers from methyltrichlorosilane in hydrogen was measured as a function of temperature, pressure, total flow rate, and simulated reactant depletion. The results, together with kinetic information on the stability of methyltrichlorosilane, led to two conclusions: (1) two different mechanisms of deposition can occur depending on whether the methyltrichlorosilane has an opportunity to dissociate into separate silicon- and carbon-containing precursors, and (2) the deposition rate is strongly reduced by the generation of byproduct HCl. The data were fitted to a simple etch model to obtain a kinetic expression that accounts for the significant effect of HCl.