| 摘要 |
<p>PURPOSE:To prevent deterioration in positioning accuracy due to deterioration of an optical sensor element by measuring the distance between the ends of shades arranged symmetrically each other, comparing the measured distance with a predetermined value and then determining variation of the end part detecting position of the shades. CONSTITUTION:After photointerrupters 6, 7 are adjusted such that the upper and lower limit positions Pu, Pd and an intemediate stage position (wafer delivery position) Pm are set as designed, a wafer chuck is driven up and down and the distances Wdm, Wdu between the positions Pd, Pm and between the positions Pd, Pu are stored as initial values Wdm1, Wdu1. Distances W'dm, W'du are determined before a wafer is fed on a pin and variation of detecting position due to deterioration of element in a photointerrupter 6 is determined according to a formula; Dd=Du=(Wdu1-W'du)/2, where Dd and Du represent variation of the positions P'd, P'u, respectively. After feeding the wafer on the pin, variation Dm of the position P'm due to deterioration of element in a photointerrupter 7 is determined according to a formula; Dm=(Wdm1-W'du) and then the shade 5 is positioned based on the variations Dm, Dd, Du.</p> |
