Failure Analysis of Power MOSFETs based on Multi- finger Configuration under Unclamped Inductive Switching (UIS) Stress Condition

Failure analysis of power devices under avalanche breakdown condition during Unclamped Inductive Switching (UIS) stress is presented. This study provides a clear understanding of the dependency of various failure mechanisms on multi-cell or finger structures in n-type LDMOS power devices investigated by 2D and 3D technology-computer-aideddesign (TCAD) simulation. The maximum amount of UIS energy (EAS) sustained by the device before failure is evaluated and is found to have a linear relationship with number of device finger and device-width. At a fixed inductive load, the dominant failure mechanism observed in devices with fewer fingers is currentfailure. Time in avalanche, tAV gets prolonged in multi-finger device design. As a result, self-heating is more resulting in temperature-failure in device with higher finger numbers.