The reactant depletion effect on chemically vapor deposited SiC films with pressure and gas ambient

Polycrystalline β-silicon carbide (SiC) films were chemically vapor-deposited onto graphite substrate using MTS(CH₃SiCl₃) as precursor and Ar or H₂ dilution gas, at temperatures ranging from 1273 to 1573 K and total pressures from 1.3 to 10.0 kPa. We investigated the effect of reactant depletion, which usually occurs in the horizontal hot wall reactor, on the characteristics of SiC films with total pressure and gas ambient. Crystalline phases and preferred orientations are determined by X-ray diffraction (XRD) and surface morphology is identified with scanning electron microscopy (SEM). The effect of reactant depletion was correlated with the decrease of the deposition rate in a gas flow direction. Its effect becomes larger with increasing deposition temperature and total pressure, but remarkably diminished when Ar was used as a dilution gas in place of H₂. With the increase of reactant depletion, preferred orientation of SiC films changes from [220] to [111] and surface morphologies of those also develop into the four-fold symmetry faceted structure in a gas flow direction. With the diminution of reactant depletion, SiC films have uniform preferred orientation of [111] and surface morphologies at all deposition positions.