| 摘要 |
PURPOSE:To eliminate the effects of the uneven surface of an object for an automatic focusing device of an optical measurement device, by using an electrostatic microdisplacement sensor to drive a piezoelectric actuator which performs a fine adjustment of the space between a mobile stage and a support stage. CONSTITUTION:A mobile stage 5 of a project aligner containing an automatic focusing device is shifted two-dimensionally and horizontally by an XY stage 8 and displaced with revolutions by a rotary stage 7 and centering on a vertical shaft. Then the stage 5 is driven vertically by an up-down displacement mechanism 6 for coarse adjustment. A wafer chuck 4 and a wafer 11 are put on the upper side of the stage 5 via three piezoelectric actuators 1A-1C, and an optical axis passes through the center of the stage 5. Then microdisplacement sen- sors 2A-2C of electrostatic type are provided on the end face of a lens barrel 30 in response to said piezoelectric actuators respectively. Then a microspace (d) between the sensor surface and the surface of the wafer 11 is detected according to the change of the electrostatic capacity. Then the voltage signal is produced to drive the actuators at positions corresponding to those sensors respectively. Thus the coincidence is secured between the space between both stages 5 and 8 and the focal distance of a lens system 3. |
