| 摘要 |
<p>PURPOSE:To improve the yield by preventing generation of minute damages on the circumferential end portion of a wafer by keeping the wafer from touching something but a holding means during the alignment operation. CONSTITUTION:A wafer 10 is attracted by an attracting plate 9 and an elevating device 3 raises a base plate 4 to keep it away from a conveyer 15. A pulse generating circuit 14-1 of a rotation controlling part 14 sends the pulses to a pulse motor 5 to rotate the wafer 10 together with the attracting plate 9 in clockwise direction. When a front end (a) of orientation flat (OF) of the wafer 10 comes on (O) just right above a light-conducting tube 11-1 of a photosensor 11, the reflected light from the wafer surface ceases and the output of the senser 11 also ceases. A pulse counter 14-3 counts number of the pulse while there is no output from the senser 11, namely the pulse for the angle theta1. OF is rotated from the position PO only by the number of pulses corresponding to the angle of theta2-1/2theta1 in clockwise direction by the pulse motor 5, thereby aligning OF in a predetermined direction Q.</p> |
