| 摘要 |
PURPOSE: To enable a relative position of a reference mark to a measurement mark on a wafer to be accurately detected by a method wherein a measurement mark and a reference mark illuminated by the reflected light from a semiconductor wafer are imaged through imaging optical paths different from each other in focal distance respectively. CONSTITUTION: A reflected light C2 from a semiconductor wafer 2 illuminated by an illuminating light C1 is made to branch into reflected lights C2a and C2b by a half mirror 11 passing through an object lens 9, a beam splitter 8, and an imaging lens 10. At this point, an X stage 6a, a Y stage 6b, and a Z stage 6c are moved so as to make a measurement mark and a reference mark on the wafer 2 located in the fields of view of a first and a second image sensing device, 12 and 13, and the measurement mark optimally focused on the first image sensing device 12. By this setup, an optical image formed by the reflected light C2a which passes through the half mirror 11 is formed on the first image sensing device 12, and another optical image formed by the reflected light C2b , reflected from the half mirror 11 is formed on the second image sensing device 13. |
