Chemically amplified negative resist composition and patterning process

Abstract

A polymer comprising 0.5-10 mol % of recurring units having acid generating capability and 50-99.5 mol % of recurring units providing for dissolution in alkaline developer is used to formulate a chemically amplified negative resist composition. When used in a lithography process, the composition ensures an effective sensitivity, makes more uniform the distribution and diffusion of the acid generating component in a resist film, and suppresses deactivation of acid at the substrate interface. The pattern can be formed to a profile which is improved in LER and undercut.

The invention claimed is: 
     
       1. A pattern forming process comprising the steps of:
 applying a negative resist composition onto a processable substrate to form a resist film, 
 exposing the film patternwise to high-energy radiation, and 
 developing the exposed film with an alkaline developer to form a resist pattern; 
 wherein the negative resist composition is a chemically amplified negative resist composition comprising a polymer, adapted such that the polymer may turn insoluble in alkaline developer by reacting with a crosslinker and/or a recurring unit having a crosslinkable functional group in the polymer under the catalysis of an acid generated upon exposure to high-energy radiation, to form crosslinks between polymer molecules, 
 said polymer consisting of: 
 0.5 to 10 mol % of recurring units of the general formula (1), 
 50 to less than 99.5 mol % of a sum total of recurring units of at least one type selected from the general formulae (2), (3), and (4), 
 greater than 0 mol % and up to 39.5 mol % of recurring units of general formula (5), 
 greater than 0 mol % and up to 39.5 mol % of a sum total of recurring units of at least one type selected from the general formulae (6) and (7), and 
 0 to 20 mol % of recurring units of the general formula (M-1) or (M-2); 
 
       
         
           
           
               
               
           
         
       
       wherein A is a single bond or a C 1 -C 10  alkylene group which may be separated by ethereal oxygen,
 Rf is each independently hydrogen, fluorine, trifluoromethyl, or pentafluoroethyl, with the proviso that not all Rf's are hydrogen, 
 B is a C 1 -C 10  divalent hydrocarbon group in which some or all hydrogen atoms may be replaced by fluorine and in which a methylene moiety at a position other than α- and β-positions relative to the ester oxygen atom may be replaced by oxygen, 
 C is a single bond or a C 1 -C 10  alkylene group which may be separated by ethereal oxygen, 
 R 1  is hydrogen, fluorine, methyl, or trifluoromethyl, 
 R 2 , R 3 , and R 4  are each independently a straight, branched or cyclic C 1 -C 10  alkyl or alkoxy group, 
 R 5  is a substituted or unsubstituted, straight, branched or cyclic C 1 -C 30  alkyl group which may contain an ether bond, or a substituted or unsubstituted C 6 -C 14  aryl group, 
 R 6  is each independently a C 1 -C 8  alkyl group, 
 R 7  is each independently a C 1 -C 8  alkyl group, 
 k, m and n are each independently an integer of 0 to 3, a is an integer of 0 to 4, b is an integer of 1 to 5, c and d each are an integer of 1 to 4, e is an integer of 0 to (4-c), f is an integer of 0 to (4-d), p is independently 0 or 1, and t is an integer of 0, 
 
       
         
           
           
               
               
           
         
       
       wherein D is a single bond or a C 1 -C 10  alkylene group which may be separated by ethereal oxygen, R 1  is as defined above, R 8  is each independently halogen, an optionally halo-substituted C 1 -C 8  alkyl or alkoxy group, a C 6 -C 20  aromatic ring-containing hydrocarbon group, or an optionally halo-substituted C 1 -C 12  acyloxy group, g is an integer of 0 to 5, q is 0 or 1, and s is an integer of 0 to 2, 
       
         
           
           
               
               
           
         
       
       wherein R 9  is independently halogen, an optionally halo-substituted C 1 -C 12  acyloxy group, an optionally halo-substituted C 1 -C 8  alkyl group, or an optionally halo-substituted C 1 -C 8  alkoxy group, and h is an integer of 0 to 4, 
       
         
           
           
               
               
           
         
       
       wherein R 1  is hydrogen, fluorine, methyl, or trifluoromethyl, R 10  is hydrogen of or a straight, branched or cyclic C 1 -C 8  monovalent hydrocarbon group, R 11  is each independently a straight, branched or cyclic C 1 -C 8  monovalent hydrocarbon group which may contain oxygen, or halogen, i is an integer of 0 to 4, and u is an integer of 0 to 2,
 wherein the recurring units of formula (1) account for 0.5 to 10 mol % and the sum of recurring units of formulae (2), (3), and (4) accounts for 50 to 99.5 mol %, recurring units of formula (5) account for 39.5 mol %, recurring units of formulae (6) or (7) account for up to 39.5 mol %, and recurring units of formulae (M-1) or (M-2) account for up to 20 mol %, based on the entire recurring units of the polymer. 
 
     
     
       2. The process of  claim 1  wherein the high-energy radiation is EUV or EB. 
     
     
       3. The process of  claim 1  wherein the processable substrate comprises a chromium-containing material at the outermost surface. 
     
     
       4. The process of  claim 1  wherein the processable substrate is a photomask blank.