| 摘要 |
PURPOSE:To enable an optimum image surface to be detected simply and readily by receiving light which is reflected from a light-sensitive substrate, etc., and is returned through a projection optical system and a mask with a photometric element at a required conjugated position and then by detecting an average focusing surface position. CONSTITUTION:Rays from a pupil EP of a projecting optical system 10 of an illumination distribution unification means 2 and from a secondary light source on an irradiation surface at a conjugate position enable a substrate 11 to be irradiated through a reticle blind 5 in conjugate relation, a pattern surface of a mask 9, the mask 9, and a projection optical system 10. Then, a reflected light from a wafer 11 reverses the same light path and then enters the pupil EP and a photometric element 15 at a conjugate position. In this case, when the wafer 11 is located at a focusing position of the optical system 10 and the wafer 11 and the mask 9 are in a conjugate relationship, reflected light image is formed again at a pattern of the mask 9 and all reflection lights pass through the mask 9. Thus, by controlling a stage 12 through a focus controller 16 so that the amount of light entering an element 15 reaches the maximum, an average optimum image surface including curve and slant can be detected simply and readily in first attempt without pattern printing, development, and photometry. |
