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 gate electrode radius of curvature 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 800oC 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/SiO
₂
interface which caused local barrier lowering. Electron injection removed them by tunneling/recombination process, which followed tunneling-front model.