Correlation Between Trench Angle and Wafer Warpage in Trench Field Plate Power MOSFETs and its Application to Quality Control

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. The main method for reducing the trench width is to design large trench angle. However large trench angle for better characteristics causes some challenges. And process window always becomes narrow to get excellent characteristic. For quality control of trench angle, we found that the wafer warpage was related to the trench angle at two process steps. We confirmed these mechanisms by simulation and experiment. Furthermore, we examined which process step was appropriate for monitoring the trench angle by wafer warpage. Finally, we acquired 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.