Effects of interface engineering for $HfO2$ gate dielectric stack on $4H-SiC$

$HfO2$ films were grown on $SiO2∕4H-SiC$ and $SiON∕4H-SiC$ layers by deposition of metallic Hf in an electron beam evaporation system followed by thermal oxidation. X-ray photoelectron spectroscopy confirmed the formation of stoichiometric $HfO2$ films. There is no evidence of formation of hafnium silicide or carbon pileup at the surface as well as at the interfacial layer. Electrical measurements show the presence of fewer trapped charges in the $HfO2∕SiON$ gate dielectric stack compared to $HfO2∕SiO2$ stack with a comparable interface state density. The $HfO2∕SiON$ stack layer improves leakage current characteristics with a higher breakdown field and has smaller flatband voltage shift under electrical stress, indicating improved reliability.