Failure mechanisms of SOI high-voltage LIGBTs and LDMOSes under unclamped inductive switching

This paper examines the behaviour of silicon-on-insulator (SOI) LIGBTs and LDMOSes under unclamped inductive switching (UIS). Surprisingly, it is found that LIGBTs can absorb much less UIS current than LDMOSes, specifically only between one-half and one-third. Two-dimensional device simulation showed that this was because hole injection from the LIGBT anode during turn-off changed the potential distribution within the device, leading to field concentration beneath the gate and hence premature failure of the gate. This has an important impact on the choice of a power device in a power integrated circuit, and its design.