Compact reticle/wafer alignment system

Abstract

A reticle/wafer alignment system provided with a laser beam source for emitting laser beams, a first optical system portion for a reticle/wafer alignment which consists of a first optical sub-system for receiving laser beams from the laser beam source and projecting the received laser beams onto alignment marks formed on a substrate and made up of diffraction gratings and a second optical sub-system for gathering laser beams diffracted by the alignment marks to form an image thereof, a photoelectric detection portion for performing a photoelectric conversion of the gathered laser beams, a position detecting portion for measuring the position of the substrate based on a signal outputted from the photoelectric detection portion, a second optical system portion for an image processing which consists of a third optical sub-system for illuminating the alignment marks and a fourth optical sub-system having a television camera for observing the image of the alignment marks, and an image processing portion for performing an image processing of video signals outputted from the television camera. The first and second optical system portions are made in such a manner to have a common part thereof. Thereby, an entire alignment system can be made to be compact. Consequently, a position measurement accuracy can be improved.