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 ($\bm {V-{GS}}$), under Fowler-Nordheim conduction only. However, as inferred, such conditions induce impact ionization-generated holes in the dielectric layer (SiO$\bm {-{2}}$), resulting in a state transition in the effective dipolar moment. This accelerates the SiO$\bm {-{2}}$ degradation leading to an overestimation of its intrinsic lifetime at typical $V-{GS}$ 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 $\bm {V-{GS}}$ 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.