Characterization and Analysis of Degradation for 1.2-kV Rated SiC Trench MOSFETs Under Repetitive Switching Impulses

The degradation behaviors and mechanism of commercial 1.2-kV rated SiC trench MOSFETs under repetitive switching impulses (RSIs) are comprehensively investigated. Two degradation regions and corresponding degradation behaviors are characterized. Region I is the gate oxide on the channel region. The electrons are trapped in region I under positive gate bias stress, which leads to a slightly positive shift of threshold voltage ( ${V}_{\text {th}}$ ) and an increment in ON-state resistance ( ${R}_{\text {ds-ON}}$ ). Region II is the gate oxide at the trench bottom corner. Hot holes are injected into the gate oxide of region II, which leads to a slight decrease in $\text {R}_{\text {ds-ON}}$ . The effect is intensified with the increase of thermal stress. Fortunately, the degradation of Region I is not affected by drain-source voltage ( ${V}_{\text {ds}}$ ) stress, even if ${V}_{\text {ds}}$ is up to 80% of the breakdown voltage ( ${V}_{\text {BR}}$ ). A severe gate leakage current was observed when it experienced $9.0\times 10^{{6}}$ switching impulses under 80% $\times 0~{V}_{\text {BR}}$ . Simulated results confirm that the leakage current path is located at the trench bottom corner, induced by a strong electric field. This simultaneously explains the degradation observed in ${V}_{\text {th}}$ and ${R}_{\text {ds-ON}}$ .