Patent ID: 7894037

Claim:
A lithographic apparatus comprising: an illumination system configured to condition a beam of radiation; a pattern support configured to hold a patterning device, the patterning device configured to pattern the beam of radiation to form a patterned beam of radiation; a substrate holder configured to hold a substrate, the substrate holder including a support surface in contact with the substrate; a projection system configured to project the patterned beam of radiation onto the substrate; and a cleaning system including a cleaning unit, the cleaning unit constructed and arranged to generate radicals, ions or both on the support surface of the substrate holder to remove contamination therefrom, wherein the cleaning system is located in an area of the apparatus in which an atmosphere of hydrogen is maintained, and wherein the cleaning unit includes a housing including a plurality of openings and an outlet in communication with a vacuum unit, the plurality of openings enabling gas communication between the atmosphere of hydrogen and an interior of the housing, and a plasma generator arranged in the interior of the housing and configured to create a plasma of hydrogen to generate hydrogen radicals, the atmosphere of hydrogen configured to act as a supply of hydrogen for the plasma generator.