Copolymer and associated layered article, and device-forming method

Abstract

A copolymer is prepared by the polymerization of monomers that include an ultraviolet absorbing monomer, and a base-solubility-enhancing monomer. The copolymer is useful for forming a topcoat layer for electron beam and extreme ultraviolet lithographies. Also described are a layered article including the topcoat layer, and an associated method of forming an electronic device.

1 . A method of forming an electronic device, comprising:
 (a) applying a photoresist layer onto a substrate;   (b) applying a topcoat layer comprising a copolymer, onto the photoresist layer;   (c) pattern-wise exposing the photoresist layer through the topcoat layer to activating radiation; and   (d) developing the exposed photoresist layer to provide a resist relief image,   wherein the copolymer comprises the polymerization product of monomers comprising:
 an out-of-band absorbing monomer; and 
 a base-solubility-enhancing monomer; and 
   wherein a film cast from the copolymer has an extinction coefficient, k, of 0.1 to 0.5 at a wavelength in the range of 150 to 400 nanometers.   
     
     
         2 . The method of  claim 1 , wherein the activating radiation comprises electron beam or extreme ultraviolet radiation. 
     
     
         3 . The method of  claim 1 , wherein the copolymer has a dispersity (W w /M n ) of 1.05 to 1.2. 
     
     
         4 . The method of  claim 1 , wherein the out-of-band absorbing monomer comprises an unsubstituted or substituted C 6 -C 18  aryl group that is free of fluorine, an unsubstituted or substituted C 2 -C 17  heteroaryl group, a C 5 -C 12  dienone group, or a combination thereof. 
     
     
         5 . The method of  claim 1 , wherein the out-of-band absorbing monomer has the structure 
       
         
           
           
               
               
           
         
         wherein 
         R 1  is hydrogen or methyl, 
         n is 0, 1, 2, 3, or 4, and 
         Ar 1  is an unsubstituted or substituted C 6 -C 18  aryl group that is free of fluorine. 
       
     
     
         6 . The method of  claim 1 , wherein the base-solubility-enhancing monomer is selected from the group consisting of (meth)acrylate esters of poly(ethylene oxide)s, (meth)acrylate esters of poly(propylene oxide)s, base-labile (meth)acrylate esters, (meth)acrylate esters substituted with a group having a ply of 2 to 12, and combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein the base-solubility-enhancing monomer comprises a (meth)acrylate ester of a poly(ethylene oxide) and a (meth)acrylate ester substituted with a 1,1,1,3,3,3-hexafluoro-2-hydroxy-2-propyl group. 
     
     
         8 . The method of  claim 1 , wherein the out-of-band absorbing monomer has the structure 
       
         
           
           
               
               
           
         
         wherein R 1  is hydrogen or methyl, n is 0, 1, 2, 3, or 4, and Ar 1  is an unsubstituted or substituted C 6 -C 18  aryl group that is free of fluorine; 
         wherein the base-solubility-enhancing monomer comprises a (meth)acrylate ester of a poly(ethylene oxide) and a (meth)acrylate ester substituted with a 1,1,1,3,3,3-hexafluoro-2-hydroxy-2-propyl group; 
         wherein the monomers comprise, based on the total moles of monomer,
 30 to 50 mole percent of the out-of-band absorbing monomer, 
 30 to 50 mole percent of the (meth)acrylate ester of a poly(ethylene oxide), and 
 10 to 30 mole percent of the (meth)acrylate ester substituted with a 
 1,1,1,3,3,3-hexafluoro-2-propyl group; and 
 
         wherein the copolymer has a dispersity (W w /M n ) of 1.05 to 1.2. 
       
     
     
         9 . The method of  claim 1 , wherein the topcoat layer is formed by spin-coating a polymer solution comprising 0.1 to 3 weight percent of the copolymer in a solvent selected from the group consisting of 2-methyl-2-butanol, 2-methyl-2-pentanol, combinations of 2-methyl-2-butanol and 2-methyl-2-pentanol, combinations of dipropylene glycol monomethyl ether and 2-methyl-2-butanol containing at least 90 weight percent 2-methyl-2-butanol, combinations of dipropylene glycol monomethyl ether and 2-methyl-2-pentanol containing at least 90 weight percent 2-methyl-2-pentanol, and combinations of dipropylene glycol monomethyl ether and 2-methyl-2-butanol and 2-methyl-2-pentanol containing at least 90 weight percent total of 2-methyl-2-butanol and 2-methyl-2-pentanol. 
     
     
         10 . A layered article comprising:
 a substrate;   a photoresist layer over the substrate; and   a topcoat layer comprising a copolymer, over and in contact with the photoresist layer,   wherein the copolymer comprises the polymerization product of monomers comprising:
 an out-of-band absorbing monomer; and 
 a base-solubility-enhancing monomer; and 
   wherein a film cast from the copolymer has an extinction coefficient, k, of 0.1 to 0.5 at a wavelength in the range of 150 to 400 nanometers.