The exposure surface of a wafer to be exposed is formed with a wafer mark having edges for scattering incident light. The edge of the wafer mark has a curved portion whose image vertically projected upon a plane in parallel to the exposure surface has a curved shape. The surface of an exposure mask is...http://www.google.de/patents/US6295120?utm_source=gb-gplus-sharePatent US6295120 - Position detection technique applied to proximity exposure
