An apparatus for setting the gap distance between a mask and a wafer, facing with each other to a predetermined distance, is arranged as follows. A wafer stage is movable along a reference plane defined as a plane parallel to the transferring direction of the wafer and supports the wafer. The wafer stage...http://www.google.com.au/patents/US5179863?utm_source=gb-gplus-sharePatent US5179863 - Method and apparatus for setting the gap distance between a mask and a wafer at a predetermined distance
