Moiré fringe-based offset control method for overlay grating alignment using substrate grating and experimental verification

This study presents a high-precision method for controlling the nanoscale offset of overlay gratings by utilizing Moiré fringes generated from a substrate grating. By optimizing the dual-beam interference optical path and monitoring the reference fringes through a CMOS camera, we achieved precise alignment of the overlay grating with a target offset of -150 nm. Experimental results demonstrated a mean offset of -146.3 nm, with errors primarily attributed to signal instability, mechanical positioning inaccuracies, and manual image calibration. This method provides a robust solution for multilayer grating alignment in optical devices and nanofabrication applications.