| 摘要 |
PURPOSE:To separate and select detected diffracted interference light independently by providing at least diffraction grating in each couple of mutually opposite areas of two bodies so that light which is projected after traveling through the couple of areas becomes diffracted light having a two-dimensional distribution. CONSTITUTION:A mask 34 is arranged at a specific Z-directional interval with a wafer 33, areas 11, 12, and 13 are prescribed at specific positions of the mask 34, and areas 21, 22, and 23 are prescribed at specific positions of the wafer 33 opposite those areas. Stripped or checked diffraction gratings are arranged in those areas and when the gratings are irradiated with two beams f1 and f2, the diffraction gratings project three diffracted interference light beams IG, IW, and IW having the two-dimensional distribution. The two light beams IW and IM which have specific degrees and are used for positioning are separated and detected independently of other diffracted light beams and detected, and consequently, the mask 34 and wafer 33 can be positioned with high accuracy irrelevantly to their interval. |
