LITHOGRAPHIC APPARATUS AND METHOD FOR FABRICATING DEVICE TO EMBODY PROJECTION SYSTEM CAPABLE OF MAINTAINING OPTICAL ELEMENTS IN THEIR PRECISE POSITIONS

摘要

PURPOSE: A lithographic apparatus is provided to embody a projection system capable of maintaining optical elements in their precise positions by maintaining the first and second optical elements in predetermined relative positions. CONSTITUTION: A radiation system supplies a projection beam(PB) of radioactive rays. A support structure supports a patterning unit functioning to pattern the projection beam according to a necessary pattern. A substrate is held by a substrate table(WT). A projection system(PL) projects the patterned beam to a target of the substrate. The radiation system and/or an illumination system includes at least the first and second optical elements and a positioning system for maintaining the first and second optical elements in predetermined positions. The positioning system includes at least one position sensor for directly measuring at least a relative position of the first optical element with respect to the second optical element, thereby maintaining the first and second optical elements in predetermined relative positions.