The thermal oxidation characteristics of α-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 oxidized Si substrates, using two differently configured deposition systems; silane, methane, and argon gas mixtures; and, temperatures from 200° to 600°C. The films were oxidized in either dry oxygen or air (with approx. 1 volume percent water) for times between 1 and 270h and temperatures from 500° to 900°C. The resulting oxide surface layers were characterized by etch rate, profilometry, XPS, and RBS techniques and were determined to consist of virtually stoichiometric SiO2 at the outermost surface with perhaps small islands of unreacted carbide remaining near the inner interface. Oxidation rates were found to increase rapidly with increasing C and H concentrations and were always much larger than those of sintered, sputtered films of stoichiometric SiC. The oxidation results were found to fit 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 CH bonds which are more prevalent in the graphitic, C-rich films than in the tetrahedrally coordinated, Si-rich ones. © 1990, The Electrochemical Society, Inc. All rights reserved.