Power Cycling SiC MOSFETs: Study of Reliability in Multi-chip Power Modules

Large-format SiC power modules are becoming widely adopted in high-current applications due to their faster switching and reduced switching losses compared to Si devices. However, the thermo-mechanical properties of Silicon Carbide are different than those of Silicon. For example, SiC chips are generally less flexible than Silicon chips of similar dimensions. This produces elevated shear forces within the thermal stackup, due to differences in the coefficient of thermal expansion between layers. This has important consequences for the lifetime of these modules. This work details a methodology for evaluating the resilience of large-format SiC MOSFET and Si IGBT power modules, along with preliminary results for and 3.3kV modules from different commercial manufacturers. Device reliability is assessed through power cycling (PC) experiments where the number of cycles to failure can be used as an indicator of device reliability. The preliminary results presented here demonstrate minimal degradation after 40k cycles with a junction temperature swing of 100 deg C.