| 摘要 |
PROBLEM TO BE SOLVED: To provide a positioning method which enables accurate positioning between a reticle and a wafer by using a video signal obtained in an image pick-up means and also to provide a projection aligner using the positioning method. SOLUTION: The projection aligner illuminates a grating mark provided on an object with light flux emitted from a light source and forms a mark interference image based on the grating mark on a surface of an image pick-up means with use of±n-th order light (n=1, 2, 3,...) of a reflection refractive light from the grating mark. And the aligner overlaps a reference interference image of a reference mark GS not interfered with the mark interference mark and different in periodicity therefrom on the surface of the image pick-up means, selects a spatial frequency component appearing inherently in an interference image based on the periodicity of the overlapped composite video signal, and detects a position of the grating mark to thereby position the object at a pedelermined position. |
