Investigations of short-circuit failure in double trench SiC MOSFETs through three-dimensional electro-thermal-mechanical stress analysis

Abstract

In this study, the short-circuit failure mechanisms of 1.2 kV double trench SiC MOSFETs were investigated by experiment and three-dimensional numerical TCAD simulation. Damage at the gate interlayer dielectric was confirmed as the cause of failure in the case of 400 V drain-source bias short-circuit transient. The three-dimensional TCAD simulation results showed that the high level of mechanical stress could cause the structural damage observed in the interlayer dielectric. Stress component analysis showed that tensile stress and shear stress were the principal stresses that caused the damage. The typical thermal runaway failure caused by activation of bipolar characteristics at extremely high temperature was confirmed, by experiment and simulation, in the case of the 800 V drain-source bias short-circuit transient. The three-dimensional simulation results indicated that activation of the bipolar junction transistor initially occurred near the gate cross-corner, and then spread throughout the entire cell.