4. Conclusion

We review the oxidation mechanism of SiC and the formation of the interface layer between SiC and SiO2. Though most of articles have reported that the Deal-Grove model also describes the SiC oxidation process, we pointed out the discrepancy in the application of Deal-Grove model, in which the oxide growth rate in the thin oxide region cannot be reproduced with this model. Aimed at the elucidation of SiC oxidation process in this thin oxide region, we proposed a kinetic model that accounts for SiC oxidation, termed the 'Si and C emission model', and showed that the model well reproduces the oxide growth rate over the entire thickness range including the thin oxide region for both the C and Si faces. The results indicated that the oxidation and emission of C and the emission of Si all need to be taken into account to describe the oxide growth process in SiC. A comparison of the parameters obtained for the C and Si faces from the curve fits revealed that the differences in initial interfacial reaction rate and Si emission ratio are contributing to the large difference in oxide growth rate between these polar faces.

We tried to apply the Si and C emission model to the oxide growth rate data at various oxidation temperatures and found that the model reproduces the oxide growth rate curves for all of the temperatures measured for both of the Si- and C-faces. Comparing with the parameters deduced from the curve fits, we discussed the differences in oxidation process between Si- and C-face. We also showed the parameters obtained in this study, some of which such as a diffusivity and solubility limit of C in SiO2 were firstly reported.

We have studied the oxygen partial pressure dependence of the SiC oxidation process on the Si- and C-faces. The oxide thickness dependence of the growth rate at sub-atmospheric oxygen partial pressures down to 0.02 atm show that, just after oxidation starts, the oxide growth rate rapidly decreases and the deceleration-rate changes to a gentle mode at around 7 nm in oxide thickness, which are probably the oxide surface growth mode and oxide internal/interfacial growth mode, respectively. We tried to reproduce the pressure dependence of oxide growth rates, however, it cannot be achieved, which is perhaps due to the inaccurate description for the oxide growth on the oxide surface.

Finally, we discussed the structure and formation mechanism of the SiC-oxide interface layer in terms of the Si and C emission phenomenon. We also introduced a recently invented technology on defect using oxidation, i.e. point defect elimination by oxidation, and suggested that understanding of oxidation mechanism is also very important in the developments of SiC bıpolar devices.
