First-principles study on C=C defects near SiC/SiO2 interface: Defect passivation by double-bond saturation

Thermally produced SiC/SiO2 stacking in SiC MOSFETs creates defect-related interfacial states in and around the band gap of SiC. These interfacial states can cause serious reliability problems such as threshold voltage shift, as well as efficiency problems such as channel mobility degradation. Carbon species having C=C double bonds have been suggested as one of the origins of these interfacial states. We have theoretically shown that this type of defect produces interfacial states in and around the band gap of SiC, and that they can be removed by saturating the C=C double bond by reactions with H2 and F2. The single-bond products of these reactions are found to be stable at regular device operation temperatures.