| 摘要 |
<p>PURPOSE:To make it possible to align the position of a wafer quickly and highly accurately by obtaining the operation of the theta axis of a table based on the inclination of a straight line passing two points of an orientation flat part and a deviation angle from the reference angle of the xytheta table. CONSTITUTION:A contour point P1 of a wafer which is closest to the center of gravity PG of the image pattern of a wafer is obtained from image data. The direction of a segment PG-P1 is made to be an approximate rotary angle alpha of the wafer. Windows W1, W2 and W3 are set in the vicinities of the intersections between three imaginary straight lines having the inclinations of +pi/2, -pi and -pi/2 with respect to the approximate rotary angle alpha and the contour of the wafer. The straight lines pass the center of gravity PG. The average contour points of the wafer are obtained in windows W1, W2 and W3. The amounts of deviations of the wafer in the directions (x) and (y) are obtained from the points. Of + or -pi/4 and + or -3pi/4, the direction closest to the final positioning direction (a) of the wafer is used, and the angular difference between the direction and the approximate rotary angle of the wafer is made to be the rotating amount of the wafer. Thus an xytheta table is rotated. Average contour points P5 and P6 in the windows which are set at the orientation flat part are obtained. The inclination of a straight line perpendicular to the straight line P5-P6 is made to be the rotary angle of the wafer. The angular difference between the angle and the final positioning direction of the wafer (a) is made to be a correcting amount theta for wafer rotation, and the axis thetaof the xytheta table is rotated.</p> |
