Ultra-precision alignment technique based on modified Moire signals

摘要

A novel method for automatic ultra-precision alignment is presented. This method relies on the modified Moire technique, and alignment marks are used in the form of gratings. The modified Moire technique can effectively improve detecting sensitivity of signals and simplify the control system by using only one pair of laser-Moire sensors. We present the mathematical model and simulation results of diffracting two gratings. The effect of various parameters on Moire signals is studied theoretically andexperimentally, and the results are found to be consistent. A computer controlled alignment device using one pair of Moire sensors is designed. The device can achieve a fully automatic precision alignment by the modified Moire signal. The experimental result shows that the alignment device can obtain the resolution of 5 nm and the positioning accuracy of ±0.5 mum.