| 摘要 |
PURPOSE:To improve a decrease in SN ratio due to scattered light greatly by preventing regular reflected and scattered light from receiving light by a detection part from the outer peripheral edge part of a mark for position detection consisting of a diffraction grating. CONSTITUTION:The projection part of an alignment mark 21 is cut slantingly and incident luminous flux B1 is made incident on the mark 21 at an angle PHIto the normal in a plane perpendicular to a position shift detecting direction. A detector D photodetects diffracted light B2 which is projected on the side of the incident luminous flux B1 to the normal in the incidence plane of the incident luminous flux B1, but the projection part of the mark 21 is cut slantingly, so light which is regularly reflected and scattered from the projection part never travels into the incidence plane except in the normal direction. Therefore, the detector D which is arranged at the position where the diffracted light B2 traveling in the incidence plane, i.e. signal light is never receive light of the regular reflected and scattered light, i.e. noisy light and the SN ratio is increased to enable high-accuracy position detection. |
