| 摘要 |
PURPOSE:To eliminate the need for the retreat of a mirror for detecting an alignment mark on exposure, and to enable alignment operation at high speed by a method wherein an alignment-mark detection optical system is arranged outside an exposure optical path on exposure, an acousto-optic element is ultrasonic-driven, and signal beams from the alignment mark on a wafer are changed into a diffraction grating and directed toward the outside of the exposure optical path. CONSTITUTION:An alignment mark on a reticle 1 is formed outside the exposure optical path of a lighting unit 5, and reflected beams from the mark are image-formed on the image sensing surface of an image sensing element 22 through a mirror 7a and a beam splitter 21, and position-sensed as a positional reference. On the other hand, scattered beams from the edge of an alignment mark on a wafer 2 placed on a moving stage 4 are projected to an acousto-optic element 11 through a projection lens 3. The acousto-optic element 11 is driven only during positioning by an ultrasonic oscillation circuit 16 and a driver 15, and compressional waves are generated on the surface by ultrasonic vibrations, thus resulting in a change into a diffraction grating. Scattered beams are image-formed on the image sensing surface of an image sensing element 25 by an objective 8 through a mirror 7b. The positions of each mark are obtained, using thc synchronous signals of the image sensing elements 22, 25 as references in both the reticle and the wafer, and the quantity of the displacement of the positions is acquired and the reticle and the wafer are positioned. |
