| 摘要 |
PURPOSE:To detect position deviation of a reticle and a wafer with high precision, by projecting the image of a scanning slit on a slit on the reticle and a slit on a wafer, and comparing time-variant phases of two bright and dark images. CONSTITUTION:When a rotary slit 2 is rotated at a constant speed, the image of the rotary slit 2 projected on a wafer 9 and the image of a slit 10 on the wafer 9 are superposed with each other, projected on a transmission window 6 on a reticle 5, and detected by a photo detector 13. A slit 7 on the reticle 5 and the projected image of the rotary slit 2 are superposed with each other. When the rotary slit 2 is rotated at a constant speed, an image whose brightness periodically changes is generated. Said image is detected by a photo detector 14. By detecting and comparing the phase difference between the photo detectors 13 and 14, the relative position of the wafer and the reticle is obtained. Hence said position is not affected by the fluctuation of air due to the change of a refractive index which is different along an optical path. |
