Thermal oxidation of carbon-terminated and silicon-terminated 6H SiC in ultrapure oxygen: Study using stable-isotope tracking

The oxidation mechanisms of 6H SiC in ultra-dry O-2 have been studied on th e (0001) face ("carbon-terminated") and the 000 (1) over bar) face ("silico n-terminated") by using isotropically labelled O-2 gases and nuclear reacti on analysis via the O-18(p,alpha)N-15 reaction. The pressure range 3-200 mb and durations of 30 minutes to 15 hours were investigated, and compared to the oxidation of Si(100) under identical conditions. As is the case for si licon, we show the formation of a layer of SiO2. Treatments in which oxidat ion is performed alternately under O-16(2), and O-18(2), coupled with measu rements of O-18 depth profiles, show the formation of new oxide near the Si O2/SiC interface. The isotopic composition of the oxide formed near the int erface is different from that of the gaas utilized, suggesting the presence of isotropic exchange phenomena or exotic growth processes such as the inj ection of silicon atoms from the SiC into the existing oxide.