| 摘要 |
PURPOSE:To obtain the detection signal having the optimum SN ratio without dividing the detection luminous flux by dividing a light accepting plane of a photoelectric detector into a part for detecting pattern signals of a detected substance and a part for deteting a detected region surface in the photoelectric detector used for relative alignment of masks and wafers. CONSTITUTION:A laser light from a laser light source 1 enters in a rotating polyhedral mirror 3 through a condenser lens 2 and the reflected light from the mirror 3 is projected on a mask 12 prevent on a wafer 13 through an objective 11 comprising a relay lens 4, a beam splitter 5, a field lens 6, a beam splitter 7, a relay lens 8, a beam splitter 9 and an incident aperture 10. In this constitution the reflected light from the splitter 7 is detected by a photodetector 18 through an image forming lens 14 and a filter 15. At this time, the reflector 18 is provided with a pattern detection light accepting plane and a scattered light accepting plane which are arranged separately and the mask alignment is performed effectively by using the pattern detection light accepting plane. |
