Patent ID: 6924884

Claim:
A lithographic projection apparatus comprising: an illumination system constructed and arranged to irradiate at least a portion of a reflective mask a first movable support constructed and arranged to hold said reflective mask, and having a physical reference surface fixed thereon; a second support constructed and arranged to hold a substrate; a projection system constructed and arranged to image the irradiated portion of the reflective mask onto a target portion of the substrate; a positioning system constructed and arranged to move said first support between an exposure station, at which said projection system can image said mask portion onto said substrate, and a measurement station; a height mapping system located at said measurement station comprising at least one sensor constructed and arranged both to measure positions of a plurality of points on a surface of said mask in a first direction substantially perpendicular to said surface and to measure a position of said physical reference surface in said first direction, said lithographic apparatus constructed and arranged to create a height map, relative to said physical reference surface, from said positions of the plurality of points on the surface of the mask; a position measuring system located at said exposure station constructed and arranged to measure a position of said physical reference surface in said first direction, after movement of said first support to said exposure station; and a position controller constructed and arranged to control a position of said first support in at least said first direction, during exposure of said target portion, in accordance with said height map and said position measured by said position measuring system.