| 摘要 |
PROBLEM TO BE SOLVED: To realize a surface position detector which is capable of very accurately positioning the surface of a wafer at the image forming position of a projection optical system by a method wherein a fluctuation detecting system which detects fluctuation signals induced by fluctuating air around a wafer and a surface position detecting system which detects the position of a wafer surface are provided properly setting their optical paths. SOLUTION: Illuminating light rays 10 of wavelengthλemitted from a light source 1 forms the image of a slit provided to a pattern forming plate 2 on the exposure surface of a wafer 5 by projection. Illuminating light rays reflected from the wafer 5 form the image of a slit again on the pattern forming plate 2 passing through a light splitting member 20. A fluctuation detecting system forms a reference light path composed of a light source 15 or a light source 16 to a photodetector 8 or a photodetector 24 partially taking advantage of a light path composed of the light source 1 to a photodetector 8 of a surface position detecting system (1 to 8). When air is fluctuating, an operational circuit 25 computes the position of a pattern image on the photodetectors 23 and 24 respectively, the output of the photodetector 24 is subtracted from that of the photodetector 23, the remainder is multiplied by a certain coefficient, and the product is outputted to an operational circuit 26.
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