New Patterned Wafer Shape Metrology Technique for In-Plane Distortion Predictions

Abstract

In semiconductor manufacturing, achieving precise overlay alignment between successive lithography layers is critical. Current methods face challenges due to non-lithographic process-induced wafer shape changes that cause in-plane distortions (IPD). This study presents Wave Front Phase Imaging (WFPI), a new technique that measures wafer shape by analyzing the intensity of reflected light without requiring interference. WFPI’s capability to produce high-resolution shape maps allows for accurate prediction of IPD. WFPI utilizes two intensity images at distinct optical distances to construct phase maps indicative of wafer topography. Our evaluation on test wafers reveals that WFPI can accurately predict IPD, matching lithography scanner outputs. The paper also shows that WFPI can acquire the wafer shape on a fully patterned 300mm silicon wafer on both frontside and backside. This technique shows the potential to significantly improve overlay accuracy, supporting advanced semiconductor manufacturing processes.