Flat-band voltage shift of 4H-SiC MOS capacitors induced by interface dipole layer formation at the oxide-semiconductor and oxide-oxide interfaces

Abstract

The positive flat-band voltage (VFB) shifts of 4H-SiC (0001) MOS capacitors with Al2O3/SiO2 dielectric layers were systematically investigated. After nitridation, there was a negative shift of VFB due to the dipole layer at the SiO2/4H-SiC interface induced by Si-N bonds. However, with Al2O3 layer deposition on thermally grown oxide, an additional dipole layer was formed at the Al2O3/SiO2 interface, which induced positive shift of VFB. Interface state density was estimated to show that the Al2O3 fabrication process had no impact on the quality of SiO2/4H-SiC interface.