Investigation of Inrush Current Induced Trench Gate Degradation Inside SiC Mosfet by New Fowler-Nordheim Localization Methodology

In this letter, an inrush current degradation mechanism of trench gate inside silicon carbide (SiC) metal-oxide-semiconductor-field-effect transistor (Mosfet) is investigated in depth under different turn-off V-GS. The preconditioning is introduced to guarantee the accuracy of gate-related parameters, avoiding effect from recoverable components. Meanwhile, a new Fowler-Nordheim localization method is proposed to nondestructively evaluate degradation extent of gate oxide on channel and nonchannel region by achieving barrier height phi(B) of hole and electron, respectively. The degradation mechanism is the substantial hole injection into gate oxide on channel region due to the electric field direction and high hole density resulting from negative V-GS and inrush current, respectively. The degradation mechanism provides significant physical insights to better understand the impact of different turn-off V-GS and safely use SiC mosfet in practical circuits. The proposed methodology also provides novel general guidance for nondestructively, assessing the quality of gate oxide of channel and nonchannel region under various operation conditions.