Ab initio-based approach for the oxidation mechanisms at SiO2/4H-SiC interface: Interplay of dry and wet oxidants during interfacial reaction

Effects of the coexistence of dry and wet oxidants on the reaction process at SiO2/4H-SiC(0001) and (000 (1) over bar) interfaces during SiC oxidation are systematically investigated by performing ab initio calculations. We find characteristic features of the interfacial reaction mechanisms, which are dependent on the plane orientation and wet oxidation condition. The incorporation of wet oxidants leads to lower barrier heights for the reaction of O-2 molecules, resulting in the promotion of interfacial reaction at the SiO2/4H-SiC(0001) interface. In contrast, the coexisting O-2 molecule assists the reactions by H2O molecule and OH groups at the SiO2/4H-SiC(000 (1) over bar) interface. Furthermore, we estimate the linear rate constants in the Deal-Grove model using the calculated barrier heights and reveal that the preferable wet ambient condition at the SiO2/4H-SiC(0001) interface is different from that at the SiO2/4H-SiC(000 (1) over bar) interface. The difference in the rate constants is caused by the difference in the rate-limiting reaction pathway between SiO2/4H-SiC(0001) and (000 (1) over bar) interfaces. These calculated results offer better understanding of the atom-scale mechanisms for the significant enhancement of SiC oxidation by the interplay of dry and wet oxidants.