Improving the Short-Circuit Capability of RC-IEGT by Backside Double P-Ring Structure

The reverse-conducting injection-enhanced gate transistor (RC-IEGT) is a device that has both p-type and n-type layers at the backside. It was found that the RC-IEGT has a weaker short-circuit capability compared to the conventional IEGT, which has a single p-type layer at the backside. We analyzed this issue using TCAD simulation and confirmed that the hole injection from the edge of the cell region is an important factor in suppressing the increase in the backside electric field. To improve the short-circuit capability without affecting the turn-off capability, we applied the backside double P-ring structure which injects the hole from the P-ring only at saturation current during short-circuit operation. As a result, the fabricated device showed an excellent short-circuit capability without any influence on other electrical characteristics, including the turn-off capability.