Investigations on the Degradation of 1.2 kV 4H SiC MOSFETs Under Repetitive Short Circuit Tests
The long term operational reliability of silicon carbide (SiC) MOSFETs needs to be further verified before they could replace silicon counterparts in power applications. In this paper, the failure mechanism of commercial 1.2 kV SiC MOFSETs under repetitive short circuit (SC) tests has been investigated. Relatively low stress defined as low bias voltage and short SC duration is imposed on the devices, eliminating the effect of gate oxide degradation and metal deterioration. The generation of hot holes in the oxide is confirmed by the charge pumping experiments and measurements on the transfer characteristics of the stressed devices during the tests. Electrothermal simulation results demonstrate that the trapped holes are located above the channel region due to the high local impact ionization generation rate and electric field. Besides, the additional positive electric field to the channel makes Vth decrease and Idss increase, which are consistent with the experimental results. What is more, the trapped holes get indeed released, as the ambient temperature increases when the stress is removed.
IEEE Transactions on Electron Devices