| 摘要 |
<p>PURPOSE:To establish highly accurate alignment by irradiating the thick surface of a wafer with light and rotating the wafer for alignment of the same. CONSTITUTION:A wafer 11 is attracted by and fixed to the center of a subchuck 15 by a transfer mechanism, and an optical sensor comprising a light emitting element 13 and a photodetector 14 is disposed in the vicinity of the thick surface of the wafer 11 with slits 13a, 14a formed through both elements for stabilization of the sensor. The thick surface of the wafer 11 is irradiated with light from the optical sensors 13, 14 and the wafer 11 is rotated to permit data to be taken out from the wafer 11. Hereby, the position of an orientation flat 12 is detected, and based upon the detected data the center of the orientation flat 12 is defined to be located at a position half the distance of the orientation flat 12. Thus, prealignment of the wafer 11 can be established highly accurately.</p> |
