Method for cleaning optical element of euv light source device and optical element cleaning device

Abstract

A method for cleaning an optical element of an extreme ultraviolet light source device for removing, from the optical element in a chamber, scattered matter generated together with extreme ultraviolet light by plasma formed through laser beam excitation of a target in the chamber, the method which comprises: making the scattered matter generated by the plasma no larger than nanosize by using solid tin as the target and using a CO 2 laser as an excitation source of the solid tin; and imparting, to the scattered matter no larger than the nanosize adhered to the optical element, an effect of overcoming the adherence of the scattered matter.

1 . A method for cleaning an optical element of an extreme ultraviolet light source device for removing, from the optical element in a chamber, scattered matter generated together with extreme ultraviolet light by plasma formed through laser beam excitation of a target in the chamber,
 the method comprising:   making the scattered matter generated by the plasma no larger than nanosize by using solid tin as the target and using a CO 2  laser as an excitation source of the solid tin; and   imparting, to the scattered matter no larger than the nanosize adhered to the optical element, an effect of overcoming the adherence of the scattered matter.   
     
     
         2 . An optical element cleaning device for an extreme ultraviolet light source device for removing, from the optical element in a chamber, scattered matter generated together with extreme ultraviolet light by plasma formed through laser beam excitation of a target in the chamber, wherein
 solid tin is used as the target,   a CO 2  laser is used as an excitation source of the solid tin, and   the optical element cleaning device comprises cleaning means for imparting, to nanosize scattered matter adhered to the optical element generated by plasma formed through excitation of the solid tin by the CO 2  laser, an effect of overcoming the adherence of the scattered matter.   
     
     
         3 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has wiping means for wiping off the nanosize scattered matter adhered to the optical element.   
     
     
         4 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has sputtering means for removing, by sputtering, the nanosize scattered matter adhered to the optical element.   
     
     
         5 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has laser light irradiation means for irradiating laser light onto the nanosize scattered matter adhered to the optical element, and detaching the scattered matter from the optical element by way of thermal shockwaves generated by irradiating laser light onto the scattered matter.   
     
     
         6 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has: water supply means for supplying water to the nanosize scattered matter adhered to the optical element; and laser light irradiation means for irradiating laser light onto the scattered matter containing water and vaporizing the scattered matter and the water.   
     
     
         7 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has gas jetting means for jetting an inert gas onto the nanosize scattered matter adhered to the optical element, and detaching the scattered matter from the optical element by way of a jetting pressure of the inert gas.   
     
     
         8 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has particle jetting means for jetting particles onto the nanosize scattered matter adhered to the optical element, and detaching the scattered matter from the optical element by way of a jetting pressure of the particles.   
     
     
         9 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has liquid filling means for filling the chamber with liquid, and removing the nanosize scattered matter adhered to the optical element by way of the liquid.   
     
     
         10 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has liquid jetting means for jetting liquid onto the nanosize scattered matter adhered to the optical element, and detaching the scattered matter from the optical element by way of a jetting pressure or detergency of the liquid.   
     
     
         11 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the cleaning means has vibration means for vibrating the optical element and detaching, from the optical element, the nanosize scattered matter adhered to the optical element.   
     
     
         12 . The optical element cleaning device for an extreme ultraviolet light source device as claimed in  claim 2 , wherein
 the optical element comprises a transmissive protective plate, provided between a plasma generation region and other optical element in such a way so as to cover the other optical element, for preventing scattered matter from adhering to the other optical element.   
     
     
         13 . The optical element cleaning device as claimed in  claim 2 , wherein
 the liquid cleaning solution comprises at least one of pure water, weak alkaline water or weak acidic water used in RCA cleaning solution, ionized water, and ozone water.   
     
     
         14 . The optical element cleaning device as claimed in  claim 2 , wherein
 The cleaning means further comprises at least one valve adapted to isolate the space.   
     
     
         15 . The optical element cleaning device as claimed in  claim 2 , wherein
 the cleaning means further comprises a heater adapted to promote evaporation of the cleaning solution.