No abstract

SiC is unique amongst the wide bandgap semiconductors in that the natural thermal oxide is stoichiometric SiO2, as is the case for silicon. The possibility of producing devices such as MOSFET in which thermal SiO2 is used as the gate insulator has motivated substantial work aimed at understanding the morphology and electrical properties of the SiO2/SiC interface and the processes responsible for thermal oxide growth. The oxide growth kinetics are quite different, parallel and anti-parallel to the crystal polar direction. We review the experimental study of the nature of the thermal oxide grown in ultra-dry oxygen and of the extended interfacial region at the SiO2/SiC interface on the nominally Si-terminated and C-terminated polar surfaces of hexagonal polytypes of SiC, highlighting how the use of stable isotopic tracing has helped to clarify processes for which kinetics measurements alone do not prove to be sufficiently incisive.

The diffusion of defects during the thermal growth of SiO2 film on Si(100) in dry O2 was investigated using sequential treatments in natural oxygen (16O2) and in heavy oxygen (18O2) in a Joule effect furnace. The O18 depth profiles were measured with a depth resolution better than 1 nm, using the nuclear reaction narrow resonance O18(p,α)15N (ER=151 keV, ΓR=100 eV). From these profiles, we confirmed that just below the surface an exchange between the oxygen atoms from the gas phase and those from the silica occurs, even for silica films thicker than 20 nm. This fact is not predicted by the Deal and Grove model. A diffusion of oxygen related defects takes place in the near surface region, with an apparent diffusion coefficient D*=4.33×10−19 cm2/s for an oxidation temperature of T=930 °C and for an oxygen pressure of P=100 mbar.