Patent ID: 8685632
Filing Date: 2014-04-01
Classification: G03F,G21K

Abstract:
1. A lithographic apparatus comprising: a source configured to generate a radiation beam comprising desired radiation and undesired radiation using a plasma; an illumination system configured to condition the radiation beam and to receive hydrogen gas during operation of the lithographic apparatus; a support structure constructed to hold a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; and one or more filters provided at an end of the projection system which receives the radiation beam last, the one or more filters being arranged to filter out ultraviolet radiation and/or deep ultraviolet radiation that assist in the generation of hydrogen radicals, wherein the lithographic apparatus is configured such that the radiation beam on entering the illumination system includes at least 50% of the undesired radiation that is generated by the plasma and includes wavelengths of radiation that interact with the hydrogen gas to generate hydrogen radicals configured to remove contamination from reflective surfaces within the lithographic apparatus.