Study of the SiO2/4H-SiC Interface Obtained by Oxidation of Nitrogen Doped Nanoscale Epitaxial Layer

A novel technique for improving SiO₂/4H-SiC interface properties by over-oxidation the nanoscale heavily nitrogen-doped 4H-SiC epitaxial layer is proposed in this paper. The potential of such method for device application was demonstrated by fabricating and testing Al/SiO₂/4H-SiC metal- oxide-semiconductor (MOS) capacitors. The results indicate that this process could strongly reduce the density of interface traps (D_it) without degrading the oxide insulating properties. The D_it extracted using C-V measurements show the lower D_it of about 6×10¹¹ cm^-2.eV^-1 at the energy of 0.3 eV below the conduction band, which is comparable with that of conventional NO-annealed process. Finally, secondary ion mass spectroscopy (SIMS) and x-ray photoelectron spectroscopy (XPS) results show that nitrogen atoms, initially introduced by the nanoscale heavily nitrogen-doped epi-layer, have been successfully incorporated at the interface of SiO₂/4H-SiC. These results show that the proposed technique is an alternative nitridation technique and can be used to improve the interface properties of the SiO₂/4H-SiC.