Polymer, resist composition, and pattern forming process

Abstract

A polymer comprising recurring units having an acid generator bound to the backbone, and recurring units having an optionally acid labile group-substituted carboxyl group and/or recurring units having an optionally acid labile group-substituted hydroxyl group is obtained by polymerizing corresponding monomers under such illumination that the quantity of light of wavelength up to 400 nm is up to 0.05 mW/cm 2 . The polymer avoids photo-decomposition of the acid generator during polymerization and concomitant deprotection reaction of the acid labile group when used in positive resist compositions. A pattern with high dissolution contrast and rectangularity is formed after development.

1 . A polymer comprising recurring units having an acid generator bound to the backbone, and recurring units of at least one type selected from recurring units having a carboxyl group optionally substituted with an acid labile group and recurring units having a hydroxyl group optionally substituted with an acid labile group, said polymer being obtained from polymerization of monomers corresponding to the recurring units under such illumination that the quantity of light of wavelength up to 400 nm is 0.05 mW/cm 2  or less. 
     
     
         2 . The polymer of  claim 1  wherein the quantity of light of wavelength up to 400 nm is 0.02 mW/cm 2  or less. 
     
     
         3 . The polymer of  claim 2  wherein the quantity of light of wavelength up to 400 nm is 0.01 mW/cm 2  or less. 
     
     
         4 . The polymer of  claim 1  wherein the illumination is provided by an LED or organic EL. 
     
     
         5 . The polymer of  claim 1  wherein the recurring units having an acid generator bound to the backbone are units of at least one type selected from recurring units having the formulae (1) to (3): 
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 5  and R 9  are each independently hydrogen or methyl,
 R 2  is a single bond, phenylene, —O—R— or —C(═O)—Y 0 —R—, Y 0  is oxygen or NH, R is a straight, branched or cyclic C 1 -C 6  alkylene, straight, branched or cyclic C 2 -C 6  alkenylene, or phenylene group, which may contain a carbonyl (—CO—), ester (—COO—), ether (—O—), sulfonic acid ester (—OS(O 2 )—), sulfonamide (—NH—S(O 2 )—) or hydroxyl moiety, 
 R 3 , R 4 , R 6 , R 7 , R 8 , R 11 , R 12  and R 13  are each independently a straight, branched or cyclic C 1 -C 12  alkyl group which may contain a carbonyl, ester or ether moiety, or a C 6 -C 12  aryl, C 7 -C 20  aralkyl, or thiophenyl group, 
 X 1  and X 2  are each independently a single bond, methylene, ethylene, phenylene, fluorinated phenylene, —O—R 14 —, or —C(═O)-Z 1 -R 14 —, Z 1  is oxygen or NH, R 14  is a straight, branched or cyclic C 1 -C 6  alkylene, alkenylene, or phenylene group, which may contain a carbonyl, ester, ether, sulfonic acid ester, sulfonamide or hydroxyl moiety, or which may be fluorinated, 
 R 10  is a C 1 -C 4  fluoroalkyl or C 6 -C 10  fluoroaryl group, and 
 M −  is a non-nucleophilic counter ion. 
 
     
     
         6 . The polymer of  claim 5  wherein at least one of R 3  and R 4 , at least one of R 6 , R 7  and R 8 , or at least one of R 11 , R 12  and R 13  is an optionally substituted phenyl group. 
     
     
         7 . The polymer of  claim 1  wherein the recurring units having a carboxyl group optionally substituted with an acid labile group and the recurring units having a hydroxyl group optionally substituted with an acid labile group have the following formulae (4) and (5), respectively, 
       
         
           
           
               
               
           
         
       
       wherein R 15  and R 17  are each independently hydrogen or methyl,
 R 16  and R 19  are each independently hydrogen or an acid labile group, 
 Y 1  is a single bond, phenylene, naphthylene or —C(═O)—O—R 20 —, R 20  is a straight, branched or cyclic C 1 -C 10  alkylene group which may contain an ether, ester, lactone ring or hydroxyl moiety, or phenylene or naphthylene group, 
 Y 2  is a single bond, a phenylene or naphthylene group which may have a nitro, cyano or halogen moiety, or —C(═O)—O—R 21 —, —C(═O)—NH—R 21 —, —O—R 21 —, or —S—R 21 —, R 21  is a straight, branched or cyclic C 1 -C 10  alkylene group which may contain an ether, ester, lactone ring or hydroxyl moiety, or a phenylene or naphthylene group which may contain a straight, branched or cyclic C 1 -C 6  alkyl, C 2 -C 6  alkenyl, C 6 -C 10  aryl, alkoxy, acyl, acyloxy, alkoxycarbonyl, nitro, cyano or halogen moiety, 
 R 18  is a single bond, or a straight, branched or cyclic, C 1 -C 16 , di- to pentavalent, aliphatic hydrocarbon group or phenylene group, which may contain an ether or ester moiety, and m is an integer of 1 to 4. 
 
     
     
         8 . A chemically amplified resist composition comprising the polymer of  claim 1 , and an organic solvent. 
     
     
         9 . The resist composition of  claim 8 , further comprising a basic compound and/or surfactant. 
     
     
         10 . A pattern forming process comprising the steps of applying the resist composition of  claim 8  onto a substrate, baking, exposing to high-energy radiation, and developing in a developer. 
     
     
         11 . The pattern forming process of  claim 10  wherein the high-energy radiation is i-line, KrF excimer laser, ArF excimer laser, EB, or soft x-ray of wavelength in the range of 3 to 15 nm.