Investigation on Robust Avalanche Capacity of Super-Junction IGBT Under UIS Stress

Avalanche capability of the super-junction insulated gate bipolar transistor (SJ-IGBT) under unclamped inductive switching (UIS) stress is experimentally investigated through a standard avalanche energy tester, accompanied with conventional N-drift IGBTs as contrasts. Measured average failure currents of the N-drift insulated gate bipolar transistors (IGBTs) and SJ-IGBT are 2.7 and 7.8 A, respectively, and the corresponding avalanche energy is 36.5 and 307 mJ, respectively, where the active area of measured SJ-IGBT is just 39% of the N-drift one. The stronger avalanche capability of SJ-IGBT can be attributed to its positive differential resistance (PDR) within the avalanche current tested range in the breakdown I – V curve, instead of the negative differential resistance (NDR) in conventional N-drift IGBTs, thus the positive electrothermal feedback in N-drift IGBTs can be suppressed in SJ-IGBTs. The multicell UIS simulation points out that, avalanche current and heat of SJBTs are evenly distributed in SJ pillar before the avalanche failure occurs, instead of concentrating on one side of the drift region as in conventional N-drift IGBTs, which is the main reason for the higher avalanche current and energy of SJ-IGBT. In addition, both PDR characteristics and UIS failure current of SJ-IGBT are sensitive to pillar doping concentration, which indicates that the higher doping concentration of SJ-IGBT is the intrinsic cause for its more robust avalanche capability.