Degradation of SiC MOSFETs with Gate Oxide Breakdown under Short Circuit and High Temperature Operation

Reliability of power semiconductor switches is important when considering their vital role in power converters for aerospace, railways, hybrid electric vehicles, and power system applications. Due to technology advancements in material sciences, power MOSFETs manufactured with wide band gap materials such as silicon carbide (SiC), gallium nitride (GaN) have been proposed as an alternative to existing silicon (Si) based MOSFETs and IGBTs. In consideration to thin oxide films and high electric field of SiC MOSFETs, gate oxide breakdown and time dependent dielectric breakdown (TDDB) calculations are necessary to completely understand the reliability of SiO2 on SiC. In this paper TDDB measurements using anode hole injection (1/E) model that are carried under high electric field of 4-7MV/cm and high temperature of 125 degrees C and 200 degrees C are presented. The experiments are also carried under high repetitive short circuit currents at elevated temperatures to accelerate the testing. It is observed that time to breakdown t(BD) reduces with increase in electric field. Since repeated short circuits results in heat inside the device under test due to dissipation, gate oxide degradation accelerates with more reduction in the time to breakdown.