Proposal of Screening Technique for Reverse Biased Safe Operating Area Failure by Unclamped Inductive Switching

In this study, we experimentally analyzed the failure mechanism of RBSOA (reverse biased safe operating area) in combination with simulation results and confirmed, for what is believed to be the first time, that IGBTs with abnormal RBSOA characteristics can be screened out by a UIS (unclamped inductive switching) test that only needs currents roughly on the order of tens of amperes, which a conventional wafer tester or chip tester can apply to individual dice in the wafer or chip state. From the simulation and experimental results, we found that the destructive traces are the same between RBSOA and UIS in defective IGBTs while they are completely different in normal ones. In addition, this is confirmed by results in which the percentages of both the RBSOA and UIS defectives are statistically the same, and IGBTs that pass UIS screening do not fail by RBSOA. These results imply the failure mechanisms are the same between RBSOA and UIS in defective IGBTs and indicate that IGBTs with abnormal RBSOA characteristics can be screened out by the UIS test