A reference plate used with an exposure apparatus that emits an exposure beam to irradiate a reference mark pattern with observation light, to detect the reflected light, and to obtain a position of the reference mark pattern. A respective reference plate is fixed on a mask stage and a wafer stage of...http://www.google.es/patents/US6608666?utm_source=gb-gplus-sharePatente US6608666 - Reference plate, exposure apparatus, device manufacturing system, device manufacturing method, semiconductor manufacturing factory, and exposure apparatus maintenance method
