| 摘要 |
PURPOSE:To obtain the aligning device of simple constitution by a method wherein the theta-control of a table is performed in such a manner that the difference between the image of arbitrary area of the wafer placed on an attracting table and the image of the area aparted in the distance corresponding to a plurality of semiconductor chips becomes the minimum. CONSTITUTION:When a wafer is automatically brought in, an attracting table is moved to the extent of the prescribed distance to a fixed image pick-up device ITV, and the picture signal of the circuit pattern A at an arbitrary place is formed. Subsequently, the attracting table is shifted as far as the distance of a plurality of semiconductor chips, a circuit pattern B is obtained, the image of the circuit pattern A retained on an image memory PM is picked up in synchronization with the processing of the above-mentioned signal, and the picture signal is substracted by a subtraction circuit OP. The differential signal obtained as above is integrated by an integration circuit DET, and the integration output for a picture frame is A/D-converted and retained. Then, the attracting table is rotated in theta-direction in the prescribed quantity in accordance with a program. Then, the theta-position at which the integration output becomes the minimum is calculated by repeating the operation same as above, and the aligning process is finished by controlling the rotation of the table. |
