Large-range lithography nano-alignment without phase unwrapping by a dual-frequency moiré fringe heterodyne

Moiré fringe is an effective approach to realize nano-alignment. However, affected by short periodicity and phase unwrapping, moiré fringe technology has small alignment ranges and redundant algorithms, making it difficult to meet practical application requirements. To solve the problem, we propose a large-range lithography nano-alignment method without phase unwrapping by a dual-frequency moiré fringe heterodyne. This method obtains four sets of moiré fringes from the main and differential alignment marks and then calculates the misalignment information using the heterodyne method. In this approach, both large alignment range and high alignment accuracy are achieved while avoiding the phase unwrapping process. The experimental results verified the rationality and feasibility of the proposed method.