An In-Depth Investigation Into Short-Circuit Failure Mechanisms of State-of-the-Art 1200 V Double Trench SiC MOSFETs

In this article, the short-circuit capability of 1200 V state-of-the-art silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (mosfet) featuring reinforced double trench structure (named RDT-MOS) is investigated comprehensively, involving the maximum short-circuit time and energy under various dc bus voltages and gate driving voltages. Furthermore, the corresponding failure mechanisms of RDT-MOS are revealed through finite-element simulation and microcosmic failure analysis. Under zero turn-off gate bias, the temperature exceeds the critical limit of melting aluminum and thermal runaway under dc bus voltages of 400 V and 800 V, respectively. The failure mechanism evolves from the fracture of interlayer dielectric to thermal runaway when increasing bus voltage from 400 to 800 V. Under negative turn-off gate bias, meanwhile, the breakdown of gate trench oxide occurs near the N+ region in the 400 V case and near both the current spreading layer region and the N+ region in the 800 V case. The location of breakdown evolves from a single region to multi-regions from 400 to 800 V. In brief, the article timely provides significant physical insights to better understand short-circuit capability and failure mechanisms and promotes the safe use of SiC mosfets in practical power circuits.