Improvement of SBD Electronic Characteristics Using Sacrificial Oxidation Removing the Degraded Layer from SiC Surface after High Temperature Annealing

Abstract

Ion implantation and a subsequent annealing at high temperature are required for fabricating a high voltage Schottky Barrier Diode (SBD) with a field limiting ring (FLR) or a junction termination extension (JTE), but high temperature annealing degrades surface condition of a SiC substrate and induces a degradation of electronic characteristics of a fabricated SBD. To avoid a degradation of SBD electronic characteristics after high temperature annealing, the method of removing a degraded layer from a SiC surface by sacrificial oxidation after high temperature annealing is studied. In this study, we studied the relationship between the improvement of SBD electronic characteristics and the thickness of sacrificial oxide grown after high temperature annealing. 9~12 SBD without edge termination were fabricated on a SiC substrate of 4mm×4mm. The ratio of good chips to all chips (9~12 SBD) increases with increasing total thickness of sacrificial oxide grown after high temperature annealing at 1800oC for 30 s, where an SBD with a leakage current less than 1μA/cm2 at reverse voltage of –100V was defined as a good chip. We applied this process growing sacrificial oxide of 150nm after high temperature annealing to fabricate the SBD with an FLR structure designed with 600V blocking voltage on a Si-face SiC substrate. The SBD with an FLR structure through this process of 150 nm sacrificial oxide is low leakage current of less than 1μA/cm2 at reverse voltage of –100V and achieves 600V blocking voltage, however, the SBD with an FLR structure without the process of sacrificial oxide after high temperature annealing is high leakage current at reverse voltage of –100V. It is shown that this process growing sacrificial oxide after high temperature annealing is useful to fabricate an SBD with an FLR structure.