Practical approaches to improve thermal SOA for smart power IC

In this paper, approaches to improve thermal SOA (T-SOA) of LDMOS have been presented. We show three important points for T-SOA based on experimental data. Firstly, improvement of thermal stability, which is expressed by simple index “α”; a ratio of drain current at 200°C divided by that at 25°C. Secondly, suppression of parasitic NPN action that causes device destruction and the correlation between failure energy and off-state leak current is studied. Thirdly, reduction of the thermal impedance. We examined an effect of Cu plate on wafer surface and a thinning effect of wafer thickness, and found thinner wafers were quite effective for long pulse energy.