Impacts of material parameters on breakdown voltage and location for power MOSFETs

To improve the electrical performance of power devices, materials used in fabrication need to be analyzed and optimized. By numerical simulations, we reveal that the breakdown voltage (BV) and location of a lateral diffused MOS power device simultaneously depend also on trench oxide permittivity. For a given device geometry, while the trench oxide permittivity with a certain value leads to a maximal BV, a smaller (larger) value causes electrical breakdown in the Si drift channel around the bottom (top) of the trench. This trend remains the same when Si is replaced by SiC. Our study implies that any by-product reducing the trench permittivity during trench filling should be avoided.