A Warpage Prediction Model for Trench Field-Plate Power MOSFET in 300mm-Diameter Process

A wafer warpage prediction model for trench field-plate MOSFETs on large diameter wafers is proposed. Trench field-plate MOSFETs have deeper trenches and thicker oxides compared to conventional power MOSFETs, and the stress imbalance between the front and back of the wafer must be controlled to suppress wafer warpage in the mass-production process. Therefore, predicting wafer warpage throughout the process is a key technology from the viewpoint of process integration, and its importance is increasing with the use of large-diameter wafers. In this study, as a main process module in trench field-plate power MOSFET process, the processes of trench formation, oxidation, polysilicon deposition, and annealing were examined. The wafer warpage and Raman shift were analyzed by comparing the experiment results with simulations in a 300 mm diameter process. Based on the measured wafer warpage, anisotropic deformation of the poly silicon after annealing was suggested, and a new model considering this anisotropic deformation was developed to predict the through-process for 300 mm wafers.