| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the high precision alignment between a mask and a wafer by a method wherein a first detecting light from a substrate mark is detected without passing through a projection optical method, a mask mark is lit by a second detecting light through the projection optical system and a light from the mask mark is detected. SOLUTION: A lighting light is applied to a wafer 5 and a reflected light from the wafer 5 is transmitted through the half mirror of an alignment coaxial optical system 1 and focused on the image pickup surface of an image pickup device. The output of the image pickup device is supplied to a control system 13. Image information consisting of a wafer mark and a pair of index marks is obtained from the control system 13. By subjecting the image information to the image processing, the position of the wafer mark is detected. A beat interference light LM from a mask mark on a mask 4 is subjected to the photoelectric conversion by a photodetector 9 and a mask mark signal is generated and supplied to the control system 13. The difference between the phase of a reference signal and the phase of the mask mark signal is detected by the control system 13 and the position of the mask mark is detected in accordance with the detected phase difference. |
