Improvement of Clamped Inductive Turn-Off Ruggedness of Trench IGBT at Overcurrent Condition with Optimized Split Gate Structure

In this paper, the clamped inductive turn-off ruggedness of a novel Trench Insulated Gate Bipolar Transistor (TIGBT) at overcurrent condition is studied by numerical simulation. This proposed structure is optimized by using split gate structure to improve the turn-off reliability. Simulation result shows that the maximum turn-off critical current of the proposed TIGBT increases for about 42.8% compared with the conventional TIGBT structure. The main reason is that the electric field of the proposed structure is redistributed by RESURF effect at the trench bottomed area, resulting to attenuate the current filament at local area. In addition, the hole which concentrated at the trench bottom area is less because the bottom part of split gate polysilicon is shorted with the emitter. Therefore, the local dynamic avalanche effect which triggered by the excessive carriers concentration and high peak electric filed accumulation is weakened. The turn-off ruggedness of the proposed structure is enhanced effectively and the electrical parameters are not compromised but even better compared with conventional structure.