Method and device for aligning first and second objects relative to each

Abstract

First and second objects are moved relative and parallel to each other, in order to be aligned. More specifically, a first mark formed on the first object has first and second light-passing sections. A second mark formed on the second object has first and second light-reflecting sections. A light beam from a light source is directed to and reflected by the first and second light-reflecting sections of said second mark and transferred onto said first mark. An image of said first light-reflecting section is projected onto the first mark, so that the first light-passing section has a first overlapping region which overlaps a part of the inner of said first light-reflecting section. An image of said second light-reflecting section is projected onto the first mark, so that said second light-passing section has a second overlapping region which overlaps a part of the image of said second light-reflecting section. A first light beam passed through the first overlapping region and a second light beam passed through the second overlapping region are detected independently. The difference in amount between these two light beams is proportional to the positional shift between the objects. The objects are adjusted relative to each other to make the first and second light beams equal in amount, so that the objects can be aligned relative to each other. The first object is a reticle and the second object is a wafer or wafer table in the projecting and exposing apparatus.