Study of the Thermomechanical Strain Induced by Current Pulses in SiC-Based Power MOSFET

Power SiC MOSFETs are going to substitute Si devices by to their significantly better performances that make them much suitable in power switching applications such as electric/hybrid vehicles. The increasingly use of these devices in critical mission profiles requires an ever-higher reliability, whereas the increase of the dissipated power during high-speed working cycling due to short current pulses leads to unavoidable thermal and mechanical stress. Here, we propose a direct method to evaluate the mechanical stress due to current pulses. This method highlights that high Power SiC-based MOSFET undergoes to almost two different thermomechanical processes with completely different time scale. The results allow a link between the thermo-mechanical stress and the device failure conditions, with special focus on the current pulses effects on metal surface, as this is a main power devices weakness.