Cleanup method for optics in immersion lithography

Abstract

An immersion lithography apparatus has a reticle stage arranged to retain a reticle, a working stage arranged to retain a workpiece, and an optical system including an illumination source and an optical element opposite the workpiece for having an image pattern of the reticle projected by radiation from the illumination source. A gap is defined between the optical element and the workpiece, and a fluid-supplying device serves to supply an immersion liquid into this gap such that the supplied immersion liquid contacts both the optical element and the workpiece during an immersion lithography process. A cleaning device is incorporated for removing absorbed liquid from the optical element during a cleanup process. The cleaning device may make use of a cleaning liquid having affinity to the absorbed liquid, heat, a vacuum condition, ultrasonic vibrations or cavitating bubbles for the removal of the absorbed liquid. The cleaning liquid may be supplied through the same fluid-applying device provided with a switching device such as a valve.

1 . A lithographic apparatus, comprising: 
 a substrate table configured to hold a substrate;    a projection system configured to project a patterned beam of radiation onto the substrate, the projection system comprising a final optical element adjacent the substrate;    a liquid supply system configured to provide a liquid to a space between the projection system and the substrate table; and    a cleaning device configured to clean the final optical element, the substrate table, or both.    
   
   
       2 . The apparatus according to  claim 1 , wherein the cleaning device comprises a liquid confinement structure of the liquid supply system, the cleaning device configured to clean the final optical element in-line in the lithographic apparatus.  
   
   
       3 . The apparatus according to  claim 1 , wherein the cleaning device comprises an ultrasonic transmitter configured to turn liquid in the space into an ultrasonic cleaning liquid.  
   
   
       4 . The apparatus according to  claim 1 , wherein the cleaning device comprises an optical element configured to supply low wavelength ultraviolet radiation.  
   
   
       5 . The apparatus according to  claim 4 , wherein the liquid supply system comprises a surface that is transparent to the low wavelength ultraviolet radiation.  
   
   
       6 . The apparatus according to  claim 4 , wherein the low wavelength ultraviolet radiation has a wavelength of about 193 nm.  
   
   
       7 . The apparatus according to  claim 1 , wherein the cleaning device is configured to supply a cleaning fluid to the space.  
   
   
       8 . The apparatus according to  claim 7 , wherein the cleaning fluid comprises a solvent.  
   
   
       9 . The apparatus according to  claim 7 , wherein the cleaning fluid comprise a detergent.  
   
   
       10 . The apparatus according to  claim 7 , wherein the cleaning fluid comprises a dissolved gas.  
   
   
       11 . The apparatus according to  claim 10 , wherein the gas is selected from oxygen, ozone or nitrogen.  
   
   
       12 . The apparatus according to  claim 1 , wherein the cleaning device is in the substrate table.  
   
   
       13 . The apparatus according to  claim 12 , wherein the cleaning device comprises a spray unit.  
   
   
       14 . The apparatus according to  claim 13 , wherein the spray unit is configured to spray a cleaning fluid onto the optical element, the substrate table, or both.  
   
   
       15 . The apparatus according to  claim 14 , wherein the cleaning fluid comprises ozone.  
   
   
       16 . The apparatus according to  claim 14 , wherein the cleaning fluid comprises plasma.  
   
   
       17 . The apparatus according to  claim 14 , wherein the cleaning fluid comprises liquid carbon dioxide.  
   
   
       18 . The apparatus according to  claim 14 , wherein the cleaning fluid comprises a non-polar organic solvent.  
   
   
       19 . The apparatus according to  claim 14 , wherein the cleaning fluid comprises a polar organic solvent.  
   
   
       20 . The apparatus according to  claim 14 , wherein the cleaning device is configured to clean only the final optical element or to clean only the substrate table.  
   
   
       21 . A lithographic apparatus, comprising: 
 a substrate table configured to hold a substrate;    a projection system configured to project a patterned beam of radiation onto the substrate, the projection system comprising a final optical element adjacent the substrate;    a liquid supply system configured to provide a liquid to a space between the projection system and the substrate table; and    a coater configured to coat the final optical element, the substrate table, or both.    
   
   
       22 . The apparatus according to  claim 21 , wherein the coater comprises a spray unit in the substrate table.  
   
   
       23 . The apparatus according to  claim 21 , wherein the coater comprises a liquid confinement structure of the liquid supply system, the coating device configured to coat the final optical element in-line in the lithographic apparatus.  
   
   
       24 . The apparatus according to  claim 21 , wherein the coating device is configured to coat only the final optical element or to clean only the substrate table.  
   
   
       25 . The use of a fluid supply system in a lithographic apparatus for the in-line application of (i) a cleaning fluid, (ii) a coating fluid, (iii) a coating remover, or (iv) any combination of (i)-(iii), to a space between a projection system and a substrate table of the lithographic apparatus.  
   
   
       26 . A spray unit configured to spray a cleaning fluid onto a final optical element of a lithographic apparatus projection system.  
   
   
       27 . An ultrasonic emitter configured to turn a liquid confined in a space between a projection system and a substrate table of lithographic apparatus into an ultrasonic cleaning liquid.  
   
   
       28 . A method of cleaning a projection system optical element, a substrate table, or both, in a lithographic apparatus configured to have a liquid in a space between the optical element and the substrate table, the method comprising circulating a cleaning fluid through the space.  
   
   
       29 . A method of coating a projection system optical element, a substrate table, or both, in a lithographic apparatus configured to have a liquid in a space between the optical element and the substrate table, the method comprising circulating a coating fluid through the space.