Optical element with a self-assembled monolayer, lithographic projection apparatus including such an optical element, and device manufacturing method

Abstract

A lithographic apparatus contains an optical element, the surface of the optical element being modified to reduce the effects of reflectivity reduction by molecular contamination. The surface includes a self assembled monolayer.

1 . A lithographic projection apparatus, comprising: 
 a radiation system configured to provide a beam of EUV radiation;    a support configured to support a patterning device, the patterning device configured to pattern the beam of radiation according to a desired pattern;    a substrate table configured to hold a substrate; and    a projection system configured to project the patterned beam onto a target portion of the substrate, wherein the radiation system and/or the projection system contains an optical element comprising 
 a substrate;  
 a Mo/Si multilayer stack on the substrate; and  
 a hydrophobic self-assembled monolayer on the multilayer stack.  
   
     
     
         2 . An apparatus according to  claim 1 , wherein the optical element has a peak reflectivity for radiation having a wavelength of about 5 nm to about 50 nm.  
     
     
         3 . An apparatus according to  claim 2 , wherein the reflectivity of the optical element is greater than about 40%.  
     
     
         4 . An apparatus according to  claim 1 , wherein the optical element is a near-normal incidence mirror, a grazing incidence mirror, an integrator, or a sensor.  
     
     
         5 . An apparatus according to  claim 4 , wherein the near-normal incidence mirror is a Mo/Si multilayer mirror.  
     
     
         6 . An apparatus according to  claim 4 , wherein the integrator is a scattering plate.  
     
     
         7 . An apparatus according to  claim 4 , wherein the sensor is an image sensor or a spot sensor.  
     
     
         8 . An apparatus according to  claim 1 , wherein the self-assembled monolayer covers about 70% of a the multilayer stack.  
     
     
         9 . An optical element, comprising: 
 a substrate;    a Mo/Si multilayer stack on the substrate; and    a hydrophobic self-assembled monolayer on the multilayer stack.    
     
     
         10 . An optical element according to  claim 9 , wherein the optical element has a peak reflectivity for radiation with a wavelength of about 5 nm to about 50 nm.  
     
     
         11 . An optical element according to  claim 9 , wherein the reflectivity of the optical element is greater than about 40%.  
     
     
         12 . An optical element according to  claim 9 , wherein the optical element is a near-normal incidence mirror, a grazing incidence mirror, an integrator, or a sensor.  
     
     
         13 . An optical element according to  claim 12 , wherein the near-normal incidence mirror is a Mo/Si multilayer mirror.  
     
     
         14 . An optical element according to  claim 12 , wherein the integrator is a scattering plate.  
     
     
         15 . An optical element according to  claim 12 , wherein the sensor is an image sensor or a spot sensor.  
     
     
         16 . An optical element according to  claim 9 , wherein the self-assembled monolayer covers about 70% of the multilayer stack.  
     
     
         17 . A device manufacturing method, comprising: 
 providing a beam of radiation;    patterning the beam of radiation; and    projecting the patterned beam of radiation onto a target portion of a substrate, wherein at least one optical element on which the beam of radiation is incident has, on its surface, a hydrophobic self-assembled monolayer.    
     
     
         18 . A method according to  claim 17 , wherein the optical element has a peak reflectivity for radiation having a wavelength of about 5 nm to about 50 mm.  
     
     
         19 . A method according to  claim 17 , wherein the reflectivity of the optical element is greater than about 40%.  
     
     
         20 . A method according to  claim 17 , wherein the self-assembled monolayer covers about 70% of a surface of the optical element.