Method for enhancing lithographic imaging of isolated and semi-isolated features

Abstract

The present invention relates to photolithography methods for enhancing lithographic imaging of isolated and semi-isolated features. A first layer of a first photoresist is formed over a substrate. A second layer of a second photoresist is formed over the first layer. The second photoresist includes a polymer containing an absorbing moiety. The second layer is exposed through a first patterned mask and developed to form a first relief image. The first relief image and the first layer are exposed through a second patterned mask. One of the first and the second patterned masks includes a dense pattern, while the other includes an isolated or a semi-isolated pattern. The first relief image and base soluble regions of the first layer are removed to form a second relief image with an isolated or a semi-isolated pattern. The second layer can also be bleachable upon exposure and bake in the present invention.

What is claimed is: 
     
         1 . A photolithography method comprising:
 forming a first layer of a first photoresist over a substrate, said first photoresist is photosensitive to a radiation having an imaging wavelength;   forming a second layer of a second photoresist over said first layer, said second photoresist comprising a polymer containing an absorbing moiety rendering said polymer absorbing said radiation;   exposing said second layer to a first dose of said radiation through a first patterned mask, said first patterned mask comprising a dense pattern;   thermally treating said second layer at a first temperature to form bleached regions in said second layer, wherein said bleached regions of said second layer have substantially lower absorption than unbleached regions of said second layer at said imaging wavelength of said radiation;   exposing said second layer and said first layer to a second dose of said radiation through a second patterned mask, wherein said second patterned mask comprises an isolated or a semi-isolated pattern and a fraction of said radiation passes through at least one said bleached region of said second layer, resulting in exposing at least one region of said first layer directly beneath said at least one said bleached region; and   removing said second layer and base soluble regions of said first layer to form a second relief image in said first layer, said second relief image comprising said isolated or semi-isolated pattern.   
     
     
         2 . The method of  claim 1 , wherein said absorbing moiety is selected from the group consisting of unsubstituted aromatic moieties and substituted aromatic moieties. 
     
     
         3 . The method of  claim 1 , wherein said dense pattern and said isolated or semi-isolated pattern have a same pattern feature, but different pitches. 
     
     
         4 . A photolithography method comprising:
 forming a first layer of a first photoresist over a substrate, said first photoresist is photosensitive to a radiation having an imaging wavelength;   forming a second layer of a second photoresist over said first layer, said second photoresist comprising a polymer containing an absorbing moiety rendering said polymer absorbing said radiation;   exposing said second layer to a first dose of said radiation through a first patterned mask, said first patterned mask comprising an isolated or a semi-isolated pattern;   thermally treating said second layer at a first temperature to form at least one bleached region in said second layer, wherein said at least one bleached region of said second layer has substantially lower absorption than unbleached regions of said second layer at said imaging wavelength of said radiation;   exposing said second layer and said first layer to a second said radiation through a second patterned mask, wherein said second patterned mask comprises a dense pattern and a fraction of said radiation passes through at least one said bleached region of said second layer, resulting in exposing at least one region of said first layer directly beneath said at least one said bleached region; and   removing said second layer and base soluble regions of said first layer to form a second relief image in said first layer, said second relief image comprising said isolated or semi-isolated pattern.   
     
     
         5 . The method of  claim 4 , wherein said absorbing moiety is selected from the group consisting of unsubstituted aromatic moieties and substituted aromatic moieties. 
     
     
         6 . The method of  claim 4 , wherein said dense pattern and said isolated or semi-isolated pattern have a same pattern feature, but different pitches.