Mechanistic Analysis of the Effect of Gap on Convex Curves of Wafer in Double-Sided Polishing

Double-Sided Polishing (DSP) is a critical process for achieving flatness in silicon wafers. This study explores the relationship between the variations in the gap between polishing plates and the surface convexity of wafers. The study indicates that differences in the gap between the upper and lower plates affect the stress distribution on the wafers, altering the removal rate at different positions during the DSP process. This results in the formation of convex curves on the wafer surface. Additionally, this research proposes a calculation method to determine the convex curves, by coupling the contact stress on wafer surface with its relative motion path to the pad, to calculate the removal amount at different positions. The reliability of the model was ultimately verified through experimental results. This method provides guidance for optimizing DSP processes to improve wafer flatness.