US Patent 7375796 Lithographic apparatus and device manufacturing method

An immersion lithography apparatus is disclosed having a liquid supply system configured to at least partially fill a space between a final element of a projection system and a substrate table, with a first liquid, and a measurement system configured to measure a location of each of a plurality of points on the substrate, the measurement system being arranged such that measurements take place through a second liquid, the second liquid not being supplied by the liquid supply system.