Active Channel Impact on SiC MOSFET Gate Oxide Reliability

It is well known that SiC MOSFETs have relatively susceptible gate oxide causing reliability concerns. Therefore, it is essential to identify gate oxide fault mechanisms under realistic conditions. The goal of this paper is to evaluate the load current impact on gate oxide degradation of SiC MOSFETs. For this purpose, conventional high electric field test (HEF) and active channel gate bias test (ACGB) are carried out under electro-thermal stress and the results are compared. During ACGB tests, both gate and drain biases applied to the device at high temperatures, and device channel is forced to conduct under various load currents. After tunning both tests, gate oxide degradation precursors such as threshold voltage and gate leakage are investigated, and the findings are compared to each other. In addition, load current impact on device consumable lifetime is evaluated, and possible failures and root causes are discussed. It is shown in the experimental results that the conductive channel with high drain-source current introduces severe device instability due to degradations and conventional HEF tests can be misleading and yield overestimated device lifetime.