Fast wafer focus measurement system for photolithography using on-axis structure illumination method

Abstract

Wafer focus-measuring system (WFMS) with high efficiency and robustness is crucial to ensure the exposure quality when advanced optical projection photolithography method is applied. In this work, we proposed a structure-illumination based wafer focus measuring system (SI-WFMS) which requires only single-step sampling process to implement the measurement of vertical defocus distance of exposure area, with less than 0.06 μm error. Both the surface profile and tilt angle of the wafer are also available to be rapidly measured through SI-WFMS, thereby saving the time of the measuring process and improving the manufacturing efficiency.