APPARATUS FOR IMAGING A MASK PATTERN ON A SUBSTRATE

摘要

PHN. 11.053 15 A pre-alignment system of an apparatus for imaging a mask pattern on a substrate is described. The pre-alignment system comprises two optical imaging systems for imaging two alignment marks provided on the substrate for the purpose of fine-alignment onto two radiation-sensitive detectors, the combined output signals of the subdetectors of each detector being a measure of the alignment of the associated alignment mark relative to a detector. me alignment marks are preferably phase gratings and the imaging systems are preferably interference-contrast microscopes.