Lithographic apparatus and lithographic apparatus cleaning method

Abstract

An immersion lithographic projection apparatus having a megasonic transducer configured to clean a surface and a method of using megasonic waves to clean a surface of an immersion lithographic projection apparatus are disclosed.

1 .- 20 . (canceled) 
     
     
         21 . An immersion lithographic projection apparatus, comprising:
 a movable table;   a projection system to project a patterned beam of radiation onto the table, the projection system having an optical element nearest the table;   a liquid confinement system configured to at least partly confine liquid between the optical element and the table for exposure of a radiation-sensitive substrate;   a cleaning liquid supply system to provide a cleaning liquid to contact the liquid confinement system; and   a shield to prevent cleaning liquid from contacting a surface, nearest the table, of the optical element.   
     
     
         22 . The apparatus of  claim 21 , wherein the shield comprises a substantially liquid-free gap adjacent the optical element surface and wherein the cleaning liquid supply system is configured to form the gap by controlling provision of cleaning liquid to a level that is below the optical element surface but at or above a bottom surface of the liquid confinement system. 
     
     
         23 . The apparatus of  claim 21 , wherein the shield comprises a plate. 
     
     
         24 . The apparatus of  claim 21 , further comprising a transducer configured to emit sonic waves to the cleaning liquid to clean a surface. 
     
     
         25 . The apparatus of  claim 24 , wherein the transducer is physically separate from the liquid confinement system and movable with respect to the projection system, the liquid confinement system, or both the projection system and the liquid confinement system. 
     
     
         26 . The apparatus of  claim 21 , wherein the cleaning liquid supply system comprises a structure movable with respect to the liquid confinement system to provide the cleaning liquid to contact the liquid confinement system. 
     
     
         27 . The apparatus of  claim 21 , wherein the cleaning liquid supply system comprises a movable structure having a recess to accommodate cleaning liquid, the recess having an inner periphery wider than an outer periphery of the liquid confinement system. 
     
     
         28 . A method of cleaning a surface of a component of a lithographic projection apparatus, the method comprising:
 providing a cleaning liquid to contact a liquid confinement structure, the liquid confinement structure configured to at least partly confine liquid between a movable table and an optical element, nearest the table, of a projection system of the lithographic projection apparatus for exposure of a radiation-sensitive substrate, the projection system configured to project a modulated beam of radiation onto the table; and   preventing cleaning liquid from contacting a surface, nearest the table, of the optical element.   
     
     
         29 . The method of  claim 28 , wherein the preventing comprises controlling provision of the cleaning liquid to a level that is below the optical element surface but at or above a bottom surface of the liquid confinement structure. 
     
     
         30 . The method of  claim 28 , wherein the preventing comprises interposing a plate between the optical element surface and the cleaning liquid. 
     
     
         31 . The method of  claim 28 , further comprising emitting sonic waves to the cleaning liquid to clean a surface. 
     
     
         32 . The method of  claim 31 , further comprising moving a transducer emitting the sonic waves with respect to the projection system, the liquid confinement structure, or both the projection system and the liquid confinement structure, the transducer being physically separate from the liquid confinement structure. 
     
     
         33 . The method of  claim 28 , comprising providing the cleaning liquid to contact the liquid confinement structure using a structure movable with respect to the liquid confinement structure. 
     
     
         34 . The method of  claim 28 , comprising providing the cleaning liquid to contact the liquid confinement structure using a movable structure having a recess to accommodate cleaning liquid, the recess having an inner periphery wider than an outer periphery of the liquid confinement structure. 
     
     
         35 . An immersion lithographic projection apparatus, comprising:
 a movable table;   a projection system to project a patterned beam of radiation onto the table, the projection system having an optical element nearest the table;   a liquid confinement system configured to at least partly confine liquid between the optical element and the table for exposure of a radiation-sensitive substrate; and   a cleaning liquid supply system to provide a cleaning liquid to contact the liquid confinement system,   wherein the apparatus is configured to prevent cleaning liquid from contacting a surface, nearest the table, of the optical element.   
     
     
         36 . The apparatus of  claim 35 , further comprising a transducer configured to emit sonic waves to the cleaning liquid to clean a surface. 
     
     
         37 . The apparatus of  claim 36 , wherein the transducer is physically separate from the liquid confinement system and movable with respect to the projection system, the liquid confinement system, or both the projection system and the liquid confinement system. 
     
     
         38 . The apparatus of  claim 35 , wherein the cleaning liquid supply system is configured to control provision of cleaning liquid to a level that is below the optical element surface such that the cleaning liquid is prevented from contacting the optical element surface. 
     
     
         39 . The apparatus of  claim 35 , wherein a plate is provided to prevent the cleaning liquid from contacting the optical element surface. 
     
     
         40 . The apparatus of  claim 35 , wherein the cleaning liquid supply system comprises a structure movable with respect to the liquid confinement system to provide the cleaning liquid to contact the liquid confinement system.