Influence of high-voltage gate-oxide pulses on the BTI behavior of SiC MOSFETs

We study the bias temperature instability (BTI) behavior of 4H-SiC trench MOSFETs after application of very high gate-voltage pulses at high temperatures. These pulses correspond to an electric field sufficiently high to trigger impact ionization and the associated effects in gate oxides. BTI effects measured in the form of threshold voltage or VTh drifts are more severe after these pulses as compared to BTI after voltage pulses that are sufficiently below the impact ionization regime. The effects shown in this paper impose an upper limit on electric fields applied to the gate during, e.g., device screening during front-end processing, but also in the application.