Method of and apparatus for in-situ repair of reflective optic

Abstract

Method of and apparatus for repairing an optical element disposed in a vacuum chamber while the optical element is in the vacuum chamber. An exposed surface of the optical element is exposed to an ion flux generated by an ion source to remove at least some areas of the surface that have been damaged by exposure to the environment within the vacuum chamber. The method and apparatus are especially applicable to repair multilayer mirrors serving as collectors in systems for generating EUV light for use in semiconductor photolithography.

What is claimed is: 
     
         1 . A method of repairing an optical element disposed in a vacuum chamber comprising the steps of:
 cleaning an exposed surface of the optical element while the optical element is in the vacuum chamber to remove at least some of a contaminant on the exposed surface to produce a cleaned exposed surface; and   exposing the cleaned exposed surface while the optical element is in the vacuum chamber to an ion flux generated by an ion gun to remove at least some areas of the surface that have been damaged by exposure to the environment within the vacuum chamber.   
     
     
         2 . A method as claimed in  claim 1  wherein said cleaning step is performed by subjecting the exposed surface to hydrogen radicals. 
     
     
         3 . A method as claimed in  claim 1  wherein said cleaning step removes substantially all of the contaminant from the exposed surface. 
     
     
         4 . A method as claimed in  claim 1  wherein said exposing step removes substantially all areas of the surface that have been damaged by exposure to the environment within the vacuum chamber. 
     
     
         5 . A method as claimed in  claim 1  wherein said exposing step comprises the additional steps of:
 generating the ion flux using an ion gun; and 
 directing the ion gun to cause ions to strike at least some areas of the surface that have been damaged by exposure to the environment within the vacuum chamber. 
 
     
     
         6 . A method as claimed in  claim 1  wherein said exposing step comprises the additional steps of:
 generating the ion flux using an ion gun; and 
 directing the ion gun to cause ions to strike substantially all areas of the surface that have been damaged by exposure to the environment within the vacuum chamber. 
 
     
     
         7 . A method of repairing a multilayer mirror in a system for producing EUV light for semiconductor photolithography, the multilayer mirror being disposed in a vacuum chamber in which a source material is vaporized to produce the EUV light, comprising the steps of:
 cleaning an exposed surface of the multilayer mirror while the multilayer mirror is in the vacuum chamber to remove at least some source material on the exposed surface to produce a cleaned exposed surface; and   exposing the cleaned exposed surface while the multilayer mirror is in the vacuum chamber to an ion flux generated by an ion gun to remove at least some areas of the surface that have been damaged by exposure to the environment within the vacuum chamber.   
     
     
         8 . A method as claimed in  claim 7  wherein said cleaning step is performed by subjecting the exposed surface to hydrogen radicals. 
     
     
         9 . A method as claimed in  claim 7  wherein said cleaning step removes substantially all of the contaminant from the exposed surface. 
     
     
         10 . A method as claimed in  claim 7  wherein said exposing step removes substantially all areas of the surface that have been damaged by exposure to the environment within the vacuum chamber. 
     
     
         11 . A method as claimed in  claim 7  wherein said exposing step comprises the additional steps of:
 generating the ion flux using an ion gun; and 
 directing the ion gun to cause ions to strike at least some areas of the surface that have been damaged by exposure to the environment within the vacuum chamber. 
 
     
     
         12 . A method as claimed in  claim 7  wherein said exposing step comprises the additional steps of:
 generating the ion flux using an ion gun; and 
 directing the ion gun to cause ions to strike substantially all areas of the surface that have been damaged by exposure to the environment within the vacuum chamber. 
 
     
     
         13 . Apparatus comprising:
 a vacuum chamber;   an optical element disposed within the vacuum chamber;   an ion source disposed within the vacuum chamber; and   an actuator mechanically coupled to the ion source and arranged to aim the ion source toward at least a portion of an exposed surface of the optical element in response to a control signal.   
     
     
         14 . Apparatus as claimed in  claim 13  wherein the ion source generates a beam and wherein a cross-section size of the beam at the exposed surface is in the range of about 2 cm to about 50 cm. 
     
     
         15 . Apparatus as claimed in  claim 13  further comprising a scanning control system connected to supply the control signal to the actuator. 
     
     
         16 . Apparatus for producing EUV light for semiconductor photolithography, the apparatus comprising:
 a vacuum chamber in which a source material is vaporized to produce the EUV light;   a multilayer mirror disposed in the vacuum chamber;   an ion source disposed within the vacuum chamber; and   an actuator mechanically coupled to the ion source and arranged to aim the ion source toward at least a portion of an exposed surface of the multilayer minor in response to a control signal.   
     
     
         17 . Apparatus as claimed in  claim 16  wherein the ion source generates a beam and wherein a cross-section size of the beam at the exposed surface is in the range of about 2 cm to about 50 cm. 
     
     
         18 . Apparatus as claimed in  claim 16  further comprising a scanning control system connected to supply the control signal to the actuator.