The effects of sequential annealing in NO and wet-O2 on interfacial properties and reliability of 4H-SiC (0001) MOS devices

Abstract Post-oxidation annealing (POA) is widely employed in academic research as well as in mass production to improve the properties of SiC MOS devices. We investigated the effect of sequential annealing in NO and wet-O2 on interfacial properties and reliability of 4H-SiC MOS capacitors. Compared with the SiC MOS capacitors with normal NO annealing, the sample with NO and wet annealing shows almost identical interface state density, near-interface trap density and the F-N effective barrier height. Regarding the breakdown characteristics, the charge-to-breakdown (QBD) of sample NO/wet is increased by two times than sample NO at cumulative failure probability F = 63.2 %. Moreover, XPS analysis results confirm that sequential annealing can reduce the interface states and improve the oxide reliability by eliminating Si-related SiOxCy defects and carbon-related defects. The subsequent wet annealing can not only annihilate oxygen vacancies which are generated by additional oxidation after NO POA, but also suppress the deterioration of bulk SiO2 quality to further improve the gate oxide reliability of SiC MOS structures. These results will be useful for the improved control of the interface state passivation technologies and the further optimization of the properties of the SiO2/4H-SiC interface.