| 摘要 |
PROBLEM TO BE SOLVED: To enable highly precise alignment capable of position detection in the curse of exposure, without decreasing throughput, by attenuating one scattered light in such a manner that light intensities of images by the scattered light from an alignment mark and a mask mark mutually approach to each other, and forming the images on an imagery surface. SOLUTION: An optical filter 26 is arranged just in front of an imaging surface 21a vertical to an optical axis 25. An image by the scattered light from the wafer mark is formed in a region 21b in the imaging surface 21a, and an image by the scattered light from the mask mark is formed in a region 21c. The transmittance of the optical filter 26 for the region 21b is different from the transmittance for the region 21c. When intensities of the scattered lights from the water mark and the mask mark which have passed through a lens 22 are different from each other, the intensities of two scattered lights which form images on the imaging surface 21a can be made to approach to each other, by suitably selecting the transmittances of the two regions of the filter 26. Images may be formed by attenuating only the one scattered light with a filter. |
