Method for reducing pattern dimension in photoresist layer

Abstract

The invention discloses improvements in the so-called coated thermal flow process for reducing the pattern dimension of a patterned resist layer on a substrate to accomplish increased fineness of resist patterning, in which a coating layer of a water-soluble resin formed on the patterned resist layer is heat-treated to effect thermal shrinkage of the coating layer with simultaneous reduction of the pattern dimension followed by removal of the coating layer by washing with water. The improvement of the process is obtained by using an aqueous coating solution admixed with a water-soluble amine compound such as triethanolamine in addition to a water-soluble resin such as a polyacrylic acid-based polymer. Further improvements can be obtained by selecting the water-soluble resin from specific copolymers including copolymers of (meth)acrylic acid and a nitrogen-containing monomer such as N-vinylpyrrolidone, N-vinylimidazolidinone and N-acryl-oylmorpholine as well as copolymers of N-vinylpyrrolidone and N-vinylimidazolidinone in a specified copolymerization ratio.

1 . A method for reducing dimensions of a resist pattern on a substrate which comprises the steps of: 
 (a) coating a patterned resist layer on a substrate surface with an aqueous coating solution comprising a water-soluble resin and a water-soluble amine compound to form a coating layer;    (b) drying the coating layer of the aqueous coating solution;    (c) subjecting the dried coating layer to a heat treatment to effect thermal shrinkage of the coating layer and reduction of the distance between resist patterns; and    (d) removing the coating layer by washing with water.    
   
   
       2 . The method as claimed in  claim 1  in which the water-soluble resin is selected from the group consisting of alkyleneglycol-based polymers, cellulose-based polymers, vinyl polymers, acrylic polymers, urea-based polymers, epoxy-based polymers, melamine-based polymers and polyamide-based polymers.  
   
   
       3 . The method as claimed in  claim 1  in which the aqueous coating solution contains from 3 to 50% by weight of the water-soluble resin.  
   
   
       4 . The method as claimed in  claim 1  in which the water-soluble amine compound is selected from the amine compounds having a pKa value in the range from 7.5 to 13 at 25° C.  
   
   
       5 . The method as claimed in  claim 1  in which the amount of the water-soluble amine compound contained in the aqueous coating solution is in the range from 0.1 to 30% by weight based on the amount of the water-soluble resin.  
   
   
       6 . The method as claimed in  claim 1  in which the temperature of the heat treatment in step (c) is lower than the softening temperature of the patterned resist layer.  
   
   
       7 . The method as claimed in  claim 4  in which the water-soluble amine compound is monoethanolamine or triethanolamine.  
   
   
       8 . A method for reducing dimensions of a resist pattern on a substrate surface which comprises the steps of: 
 (a2) coating a patterned resist layer with an aqueous coating solution containing a water-soluble resin, which is a copolymer of (meth)acrylic acid and an ethylenically unsaturated monomeric compound selected from the group consisting of N-vinylpyrrolidone, N-vinylimidazolidinone, methyl acrylate, methyl methacrylate, N,N-dimethylacrylamide, N,N-dimethylaminopropyl methacrylamide, N,N-dimethylaminopropyl acrylamide, N-methhylacrylamide, diacetoneacrylamide, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate and N-acryloylmorpholine;    (b2) drying the coating layer to form a dried coating layer of the water-soluble resin;    (c2) subjecting the dried coating layer to a heat treatment to effect thermal shrinkage of the coating layer and reduction of dimensions of the resist pattern; and    (d2) dissolving away the coating layer by washing with water.    
   
   
       9 . The method as claimed in  claim 8  in which the water-soluble resin is a copolymer of (meth)acrylic acid and the ethylenically unsaturated monomeric compound in a copolymerization ratio in the range from 4:1 to 1:1 by moles.  
   
   
       10 . The method as claimed in  claim 8  in which the heat treatment in step (c2) is conducted at a temperature lower than the softening temperature of the patterned resist layer.  
   
   
       11 . A method for reducing dimensions of a resist pattern on a substrate surface which comprises the steps of: 
 (a2) coating the patterned resist layer with an aqueous coating solution containing a water-soluble resin which is a homopolymer of N-vinylpyrrolidone or a copolymer of N-vinylpyrrolidone and a comonomer which is N-vinylimidazolidinone, N-acryloylmorpholine or a combination thereof to form a coating layer of the aqueous coating solution;    (b2) drying the coating layer to form a dried coating layer of the water-soluble resin;    (c2) subjecting the dried coating layer to a heat treatment to effect thermal shrinkage of the coating layer and reduction of the resist pattern dimension; and    (d2) dissolving away the coating layer by washing with water.    
   
   
       12 . The method as claimed in  claim 11  in which the water-soluble resin is a copolymer of N-vinylpyrrolidone and N-vinylimidazolidinone.  
   
   
       13 . The method as claimed in  claim 12  in which the water-soluble resin is a copolymer of N-vinylpyrrolidone and N-vinylimidazolidinone in a copolymerization ratio in the range from 9:1 to 1:9 by moles.  
   
   
       14 . The method as claimed in  claim 11  in which the temperature of the heat treatment in step (c2) is lower than the softening temperature of the patterned resist layer.  
   
   
       15 . An aqueous coating solution used in the coated thermal flow process for reducing a resist pattern dimension of a patterned resist layer on a substrate which comprises a water-soluble resin and a water-soluble amine compound.  
   
   
       16 . The aqueous coating solution as claimed in  claim 15  in which the water-soluble resin is selected from alkyleneglycol-based polymers, cellulosic polymers, vinyl polymers, acrylic polymers, urea-based polymers, epoxy polymers, melamine-based polymers and polyamide polymers.  
   
   
       17 . The aqueous coating solution as claimed in  claim 15  in which the water-soluble amine compound has a pK value in the range from 7.5 to 13.  
   
   
       18 . The aqueous coating solution as claimed in  claim 15  in which the water-soluble amine compound is monoethanolamine or triethanolamine.  
   
   
       19 . The aqueous coating solution as claimed in  claim 15  in which the amount of the water-soluble amine compound is in the range from 0.1 to 30% by weight based on the amount of the water-soluble resin.  
   
   
       20 . An aqueous coating solution of a water-soluble resin used in the coated thermal flow process for reducing a resist pattern dimension of a patterned resist layer on a substrate in which the water-soluble resin is a copolymer of (meth)acrylic acid and an ethylenically unsaturated monomeric compound selected from the group consisting of N-vinylpyrrolidone, N-vinylimidazolidinone, methyl acrylate, methyl methacrylate, N,N-dimethylacrylamide, N,N-dimethylaminopropyl methacrylamide, N,N-dimethylaminopropyl acrylamide, N-methhylacrylamide, diacetoneacrylamide, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate and N-acryloylmorpholine.  
   
   
       21 . The aqueous coating solution as claimed in  claim 20  in which the water-soluble resin is a copolymer of acrylic acid and N-vinylpyrrolidone.  
   
   
       22 . An aqueous coating solution of a water-soluble resin used in the coated thermal flow process for reducing a resist pattern dimension of a patterned resist layer on a substrate in which the water-soluble resin is a copolymer of N-vinylpyrrolidone and N-vinylimidazolidinone.  
   
   
       23 . A method for selection of a water-soluble resin used in the coated thermal flow process for reducing the pattern dimension of a patterned resist layer formed on a substrate surface comprising the steps of forming a coating layer of a water-soluble resin on a patterned resist layer, subjecting the coating layer to a heat treatment to effect thermal shrinkage of the coating layer and reduction of the pattern dimensions and removing the coating layer by washing with water, which comprises the steps of: 
 (a3) forming a coating layer of the water-soluble resin on the surface of an unpatterned but photocured photoresist layer on a substrate surface;    (b3) subjecting the coating layer of the water-soluble resin at 140° C. for 60 seconds; and    (c3) dissolving away the coating layer of the water-soluble resin by washing with water at 23° C. to determine the dissolving time taken for complete removal of the coating layer.    
   
   
       24 . The method as claimed in  claim 23  in which the water-soluble resin is selected from the group consisting of acrylic polymers, vinyl polymers, cellulose-based polymers and alkyleneglycol-based polymers.  
   
   
       25 . The method as claimed in  claim 24  in which the water-soluble resin is an acrylic polymer or a vinyl polymer.  
   
   
       26 . The method as claimed in  claim 25  in which the water-soluble resin is an acrylic polymer.  
   
   
       27 . The method as claimed in  claim 23  in which the temperature of the heat treatment in step (b) is lower than the softening point of the photocured photoresist layer.