| 摘要 |
PURPOSE:To position a mask, a wafer, etc. accurately by executing a rough positioning by a first control means by a one-dimensional image sensor and executing a precise positioning by a second control means detecting the magnitude of scattered light and diffracted light. CONSTITUTION:A polarizing half prism 26 separates zero order beams DM0 from a mask 20 and zero order beams DW0 from a wafer 21 into two by polarized light, and introduces them to the light-receiving surfaces of one-dimensional image sensors 27, 28. A positional displacement between the mask 20 and the wafer 21 to the position of an optical point of an objective 19 is detected by the one-dimensional image sensors 27, 28, and both are moved relatively. Diffracted light passing through a spatial filter 30 is projected to a polarizing half prism 32. The polarizing half prism 32 separates the diffracted light into diffracted light DM from the mask 20 and diffracted light DW from the wafer 21, and each introduces them to photoelectric detectors 33, 34. A precise focussing is executed by detecting the intensity of diffracted light DM, DW. |
