A look underneath the SiO(2)/4H-SiC interface after N(2)O thermal treatments

The electrical compensation effect of the nitrogen incorporation at the SiO(2)/4H-SiC (p-type) interface after thermal treatments in ambient N(2)O is investigated employing both scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM). SSRM measurements on p-type 4H-SiC areas selectively exposed to N(2)O at 1150 °C showed an increased resistance compared to the unexposed ones; this indicates the incorporation of electrically active nitrogen-related donors, which compensate the p-type doping in the SiC surface region. Cross-sectional SCM measurements on SiO(2)/4H-SiC metal/oxide/semiconductor (MOS) devices highlighted different active carrier concentration profiles in the first 10 nm underneath the insulator–substrate interface depending on the SiO(2)/4H-SiC roughness. The electrically active incorporated nitrogen produces both a compensation of the acceptors in the substrate and a reduction of the interface state density (D(it)). This result can be correlated with the 4H-SiC surface configuration. In particular, lower D(it) values were obtained for a SiO(2)/SiC interface on faceted SiC than on planar SiC. These effects were explained in terms of the different surface configuration in faceted SiC that enables the simultaneous exposition at the interface of atomic planes with different orientations.