| 摘要 |
PURPOSE:To attain the in-focus state quickly with a high precision by irradiating the first object at angles of incidence different from each other to detect the deviation of a projected image on the second object. CONSTITUTION:The laser light of a light source 5 passes a polygonal mirror 8 and is divided by a prism 12 and scans a reticle 1 through mirrors 13 and 17, and the reflected light is detected by a photodetector 21. Meanwhile, the transmitted light of the reticle 1 passes a projection lens 2 and scans a wafer 3, and the reflected light has the direction of polarization rotated at 90 deg. by a quarte-wave plate 18 and is detected through a mirror 15 by a photodetector 25. A mirror 6 is moved to made the light incident on the wafer and the reticle surface at two kinds of angle to measure the extent of deviation of relative position between the reticle 1 and the wafer 3. Thus, the in-focus state is attained quickly with a high precision. |
