| 摘要 |
PURPOSE:To detect with stability a prescribed largest orientation flat of one of increasingly diversifying wafers by a method wherein light is projected on the vicinity of an end of a semiconductor wafer after it is turned for the formation of an optical image to be used for the detection of a prescribed position. CONSTITUTION:A light source 15 is built of LEDs lined along the radius of a wafer 1. A condenser 17 collects light transmitted by the light source 15 and electric signals are outputted by a line image sensor 19. The line image sensor 19 is driven by a counter 21 and the electric signals are amplified by a preamplifier 23 owing to the wafer 1 in revolution. The electric signals are applied to a zero clamp circuit 25, binarized in a comparator 27, and applied to a counter 29. The continuous dark status along the circumference of the wafer 1 is subjected to counting and the result is applied to a minimum value detecting circuit 31. In this way, the minimum value during the revolution of the wafer 1, that is, the position of the largest orientation flat is detected. A table controlling circuit 33, upon receiving the detected signals, drives a motor 5 for the positioning of the wafer 1. |
