Oxidation of plasma-deposited α-SixC1-x : H films

The thermal oxidation characteristics of alpha-SixC1-x:H films were studied for compositions from x = 0.25 to 0.51 and varying hydrogen concentrations. The carbide films were plasma-deposited onto oxidised Si substrates, using two differently configured deposition systems; silane, methane, and argon gas mixtures; and, temperatures from 200 to 600 C. The films were oxidised in either dry oxygen or air (with approx. 1 volume percent water) for times between 1 and 270 h and temperatures from 500 to 900 C. The resulting oxide surface layers were characterised by etch rate, profilometry, XPS and RBS techniques and were found to consist of virtually stoichiometric SiO2 at the outermost surface with perhaps small islands of unreacted carbide remaining near the inner interface. Oxidation rates increased rapidly with increasing C and H concentrations and were always much larger than those of sintered, sputtered films of stoichiometric SiC. The oxidation results fitted reasonably well to a mixed linear-parabolic time dependence. This kinetic analysis suggested that the large observed increases in the linear and parabolic rate constants with decreasing x could be attributed to preferential attack on C-H bonds which are more prevalent in the graphitic, C-rich films than in the tetrahedrally coordinated, Si-rich ones. 21 refs.