Nano-Focusing and Leveling System Based on Improved Phase Analysis

A nano-focusing and leveling system (FLS) based on improved phase analysis is proposed to measure the wafer height in lithography. Different from traditional methods, this paper applies a grating-based mark to conduct the measurement according to the principle of the Moiré effect. The phase analysis is also improved based on the fringe frequency feature, which is quantitatively analyzed for the first time. As a result, the wafer height can be measured with nanoscale precision. Compared with the existing FLS, the proposed method can get higher precision. Both the simulations and experiments are carried out to verify the feasibility and accuracy of the proposed method.