Large range nano alignment for proximity lithography using complex grating

Abstract

We propose a novel alignment method with nanoscale precision and hundreds of microns detecting range for proximity lithography. With this method, both coarse and final alignments are realized by complex grating based on moiré fringe. For distinguishing the complex gratings in frequency spectrum, there is no interference between the coarse and the final alignment parts. Within only one pattern, modulation of the coarse mark and phase of the final mark can be calculated respectively. Combining the two results, we can do the alignment with nanoscale precision in large measurement range. Furthermore, the structure of our measurement system is simple. Simulation and experiments are carried out to validate the feasibility of the proposed method.