Analysis of Long-Term Reliability of SiC in Traction Inverter Considering Vth Instability

Abstract:
Along with the booming of electrical vehicles, wide band gap (WBG) semiconductors, such as silicon carbide (SiC) is receiving more and more attention from both academic and industrial fields. There exist quite some design challenges, such as stray inductance optimization, thermal management enhancement due to smaller die size. Among them, long-term reliability of the gate threshold voltage (Vth), es-pecially under AC stress, is of paramount importance. Dynamic gate stress (DGS) test is proposed by AQG324 to give a guideline how to identify the Vth drift performance in test stage considering reliability design of traction inverters. Typically, 5% change of RDSON due to DGS test is followed currently as a preliminary acceptance criteria of Vth drift test. Nevertheless, the acceptance criteria should be deter-mined based on mission profile of traction inverter. Moreover, how to use the results from DGS in long-term reliability evaluation still require further investigation. In this paper, a design methodology considering long-term reliability is proposed by utilizing the mission profile of electrical vehicles, with which test results from DGS have been taken into account. This not only acts as a way to analyze Vth instability impact on SiC lifetime but also can act as a way to justify DGS test results about whether the selected device can satisfy the performance requirement regarding reliability aspects.