Impact of gate drive voltage on avalanche robustness of trench IGBTs

In this paper, the impact of the gate drive voltage on avalanche capability of Trench-IGBTs is deeply analyzed by means of infrared (IR) thermal measurements and TCAD simulations during Unclamped Inductive Switching (UIS) test. The reported results are carried out for a case study on a 1.2 kV - 200 A rated device. Experimental results show the effect of the gate drive voltage during avalanche operation. A possible non-uniform current conduction for unipolar gate-driver case is proven using transient thermal maps. As a consequence, the dependence of the actual breakdown voltage (VBR) of the device active area with a negative gate biasing is investigated for trench structures. A reduction of the VBR and a slighter interplay between the T-IGBT cells and the termination area is demonstrated for a negative gate bias during the blocking state using ad-hoc TCAD electro-thermal simulations. Finally, the boosted avalanche capability is proven for under-biased case and a theoretical explanation of the involved phenomena is provided.