Analysis Self-Healing of Gate Leakage Current due to Oxide Traps to Improve Reliability of Gate Electrode

To achieve robust SiC-MOSFET, reliability of the gate insulator was investigated in terms of gate electrode edge treatment. Analytical calculation showed that r should be larger than the thickness of gate insulator to relax the electric field concentration. We obtained the rounded gate edge by dry oxidation at 1000°C, while oxidation at 800°C had it sharpened. Former samples exhibited low leakage current with Time-Zero-Dielectric-Breakdown (TZDB) measurement. I_g consisted of Fowler-Nordheim (FN) tunneling current for V_g > 0, and it includes excess components for V_g < 0. We confirmed that they occurred at the gate edge and that they coursed positively charged trap centers in oxide near poly-Si/SiO₂ interface which caused local barrier lowering. Electron injection removed them by tunneling/recombination process, which followed tunneling-front model.