| 摘要 |
PROBLEM TO BE SOLVED: To realize an automatic focusing device which is capable of very accurately detecting the surface position of a plate-like work by a method wherein a light projecting means which irradiates the platelike work placed on a stage movable in a direction vertical to the light axis of a projection optical system with light spots, a photodetecting means which detects a reflected light flux from the platelike work, and a computing device which computes signals outputted from the photodetecting means are properly set in configuration. SOLUTION: Light rays projected from a light source 4 are turned to a collimated light flux through a lighting lens 5 to irradiate an aperture mask 6 where pinholes are provided. The images of the pinholes provided to the mask 6 are formed on a wafer 2 by an image forming lens 7 and a deflecting mirror 8. Light fluxes reflected at measurement points on a wafer 2 are changed in the direction of travel by the deflecting mirror 9 and made to impinge on a position detecting detector 11 where photodetectors are two-dimensionally arranged through the intermediary of a detection lens 10. Signals outputted from the position detecting device 11 are formed into the surface position data of the measurement points by a surface position detecting means 14, the surface position data of the measurement points are inputted into a control means 13, the command signals outputted from the control means 13 are inputted into a stage drive means 12, and a wafer stage 3 is driven by the stage drive means 12 of servo mechanism. |
