Quality Control of Trench Field Plate Power MOSFETs by Correlation of Trench Angle and Wafer Warpage

Field-Plate (FP) MOSFET structure has been studied to get higher performance characteristics. To get low drift layer resistance, reduction of the trench width is one typical method with FP-MOSFET because it enables us to design the fine cell pitch of the FP-MOSFET. Trench width is relevant to trench angle. However large trench angle for better characteristics causes the variation of the dielectric breakdown voltage on the oxide film that separating the gate and source. Therefore, process window becomes always narrow to get excellent characteristic. For quality control of trench angle, we find that wafer the warpage is relevant to the trench angle. We confirmed the dependence by simulation and experiment. Furthermore, we acquire four correlation data related to the wafer warpage after field plate oxidation. Subsequently, we derived the regression equation for quality control and confirmed the validity of the equation.