Charge Trapping in SiC MOSFETs under Constant Gate Current Stress: Analysis Based on Charge Pumping Measurements

This work improves the understanding of charge trapping in SiC MOSFETs during constant gate current stress, by presenting an analysis based on charge pumping measurements (constant-amplitude approach) and threshold voltage measurements. The tests were done by a custom-made, on-wafer, in situ monitoring setup. A non-monotonic trend for the gate voltage was observed during the stress, and each phase was linked to a charge trapping mechanism: a) electron trapping at near-interface oxide traps; b) hole trapping, due to impact ionization in the oxide; c) generation of electron traps at the interface. Charge pumping measurements provided a quantitative description of the variation of the interface traps in the long term. Such trapping phenomena are explained based on the literature on interface and oxide defects in SiC. Persistence of the created defects and trapped charge was studied as well.