It was recalled that SiC offered the great advantage of having SiO2 as its native oxide. Unfortunately, normal thermal oxidation produced an unacceptably high density of interface states, with a complex energy distribution. Deep states were assumed to be caused by C excess at the interface, while the slow electron traps, with an especially high density near to the conduction band of 4H-SiC, were expected to originate from oxide defects near to the interface. Unlike the case of the Si/SiO2 interface, simple H passivation did not help to reduce the high trap density. A possible passivation method for both deep states and interface states was post-oxidation annealing or oxidation in the presence of NO or N2O molecules. Here, systematic and sophisticated theoretical calculations, based upon a model of the 4H-SiC/SiO2 interface, were performed in order to establish the main reaction routes and the most important defects that were created during dry oxidation, and which could give rise to the observed interface traps. The effect of N in suppressing them was also investigated.

The Mechanism of Defect Creation and Passivation at the SiC/SiO2 Interface. P.Deák, J.M.Knaup, T.Hornos, C.Thill, A.Gali, T.Frauenheim: Journal of Physics D, 2007, 40, 6242-53