Alignment method and apparatus for reduction projection type aligner

Abstract

An alignment method and apparatus for reduction projection type aligner in which the rough detection of reticle position in the reticle alignment process at the time of mounting a reticle and the fine detection of reticle position in the wafer alignment for the alignment between a wafer and the reticle are performed automatically by the same reticle alignment pattern and the same optical alignment detection system. A plurality of one- or two-dimensional Fresnel zone plates having different shapes of diffraction patterns formed outside of a reticle circuit pattern and arranged at a position outward of the entrance pupil of the reduction projection lens are used as a reticle alignment pattern to detect the absolute position of the reticle. The detection field of view of the optical alignment detection system is thus effectively widened to make pattern detection possible with high magnification for an improved detection accuracy. The same reticle alignment pattern and the same optical alignment detection system are used for rough detection of reticle position in reticle alignment and fine detection of reticle position in wafer alignment. In the optical alignment detection system, on the other hand, the image position of the diffraction pattern from the reticle alignment pattern and the image position of the wafer alignment pattern are located at the same distance from the reticle surface.