Contact or proximity printing using a magnified mask image

Abstract

Improvements in the fabrication of integrated circuits are driven by the decrease of the size of the features printed on the wafers. Current lithography techniques limits have been extended through the use of phase-shifting masks, off-axis illumination, and proximity effect correction. More recently, liquid immersion lithography has been proposed as a way to extend even further the limits of optical lithography. This invention described a methodology based on contact or proximity printing using a projection lens to define the image of the mask onto the wafer. As the imaging is performed in a solid material, larger refractive indices can be obtained and the resolution of the imaging system can be increased.

1 . A lithography system comprising:
 a plurality of lens elements;   a lens enclosure establishing a controlled environment between the lens elements in the plurality of lens elements, the plurality of lens elements having a first lens element adapted to face a source of radiation, and having a final lens element comprising a material with an index of refraction greater than 1, and having a surface adapted to be placed in contact or in close proximity with the sample; and   a stage to support said sample in contact or in close proximity with the surface of the final lens element.   
     
     
         2 . The lithography system of  claim 1 , wherein the material of said final lens element comprises one of silicon dioxide, calcium fluoride, aluminum oxide, yttrium fluoride, lanthanum fluoride, and strontium fluoride. 
     
     
         3 . The lithography system of  claim 1 , wherein said plurality of lens elements projects radiation having a wavelength of about 193 nm to the sample. 
     
     
         4 . The lithography system of  claim 1 , wherein said plurality of lens elements projects radiation having a wavelength of about 157 nm to the sample. 
     
     
         5 . The lithography system of  claim 1 , including a mask between the source of radiation and said plurality of lens elements, and said plurality of lens elements demagnifies an object on the mask by a factor greater than 4 at an image plane on or near said sample. 
     
     
         6 . The lithography system of  claim 1 , including a mask between the source of radiation and said plurality of lens elements, and said plurality of lens elements projects an image of an object on the mask at an image plane on or near the surface of the final lens adapted to be placed in contact or in close proximity with the sample. 
     
     
         7 . The lithography system of  claim 1 , wherein said sample has a layer adapted to be developed in response to radiation projected by the plurality of lens elements, said layer having an index of refraction, and wherein said final lens element comprises a material having an index of refraction matching the index of refraction of said layer. 
     
     
         8 . The lithography system of  claim 1 , wherein the final lens element comprises a removable slab of said material. 
     
     
         9 . A lithography system comprising:
 a projection lens for imaging an object on a mask onto a sample, one side of the projection lens adapted to be placed in contact or in close proximity with the sample and an other side of the projection lens adapted to be placed in contact or in close proximity with the mask; and   a stage to support said sample in contact or in close proximity with the projection lens.   
     
     
         10 . The lithography system of  claim 9 , wherein a material of a lens element of said projection lens adapted to be placed in contact or in close proximity with the mask, comprises a material including one of silicon dioxide, calcium fluoride, aluminum oxide, yttrium fluoride, lanthanum fluoride, and strontium fluoride. 
     
     
         11 . The lithography system of  claim 9 , wherein said projection lens projects radiation having a wavelength of about 193 nm from the mask to the sample. 
     
     
         12 . The lithography system of  claim 9 , wherein said projection lens projects radiation having a wavelength of about 157 nm from the mask to the sample. 
     
     
         13 . The lithography system of  claim 9 , wherein said projection lens demagnifies an image on the mask by a factor greater than 4 at an image plane on or near said sample. 
     
     
         14 . The lithography system of  claim 9 , wherein said projection lens includes a lens having a surface adapted to be placed in contact or in close proximity with the sample, and projects an image of a mask at an image plane on or near said surface of said lens. 
     
     
         15 . The lithography system of  claim 9 , wherein the lens having a surface adapted to be placed in contact or in close proximity with the sample comprises a removable slab of said material. cm  16 - 27 . (canceled)