Physics-Based Strategies for Fast TDDB Testing and Lifetime Estimation in SiC Power MOSFETs

To expedite testing, time-dependent dielectric breakdown (TDDB) analyses are conducted on commercial 4H-SiC MOSFETs at high gate-to-source voltages (VGS), under Fowler-Nordheim conduction only. However, as inferred, such conditions induce impact ionization-generated holes in the dielectric layer (SiO2), resulting in a state transition in the effective dipolar moment. This accelerates the SiO2 degradation leading to an overestimation of its intrinsic lifetime at typical VGS values for gate driving in power converters. To address this, a physics-based approach is proposed to design TDDB tests under such conditions and to correct the intrinsic lifetime prediction at nominal VGS values, shortening the testing time by up to two orders of magnitude. Thus, the proposed method is a well-suited candidate to be considered in SiC power device qualification standards, still under development.