Radiation-sensitive resin composition, polymer, and method for forming resist pattern

1. A radiation sensitive resin composition comprising,

a first polymer (A) which comprises:

a repeating unit (1) represented by the following general formula (1); and

a repeating unit (2) being other than the repeating unit (1), having an acid labile group, and being represented by the following general formula (2-1), a total amount of the repeating unit (1) and the repeating unit (2) is at least about 85 mol % based on a total amount of repeating units included in the first polymer;

a second polymer (B) which comprises an acid labile group and is dissociated by an action of acid so that alkali solubility is given by dissociation of said acid labile group; and

a radiation sensitive acid generator (C),

wherein, in the formula, R 1 represents a hydrogen atom, a methyl group, or a trifluoromethyl group, R 2 represents a single bond, a divalent linear, branched, or cyclic, and saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, X represents a methylene group substituted with a fluorine atom, or a linear or branched fluoroalkylene group having 2 to 20 carbon atoms, and R 3 represents a monovalent organic group,

wherein, in the formula, R 4 represents a hydrogen atom, a methyl group, a trifluoromethyl group, or a hydroxymethyl group, and R 5 each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms, a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, or a group derived therefrom, or any two of R 5 bind to each other and form, together with the carbon atom to which they are attached, a divalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, or a group derived therefrom, and the remaining one R 5 represents a linear or branched alkyl group having 1 to 4 carbon atoms, a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, or a group derived therefrom.

2. The radiation sensitive resin composition according to claim 1 , wherein the polymer (A) comprises, as said repeating unit (2), a repeating unit represented by the following general formula (2-1-1),

wherein, in the formula, R 6 represents a hydrogen atom, a methyl group, a trifluoromethyl group, or a hydroxymethyl group, R 7 represents a linear or branched alkyl group having 1 to 4 carbon atoms, and k represents an integer of 1 to 4.

3. The radiation sensitive resin composition according to claim 1 , wherein said polymer (A) further comprises a repeating unit (3) having an alkali soluble group and being other than said repeating unit (1), or a repeating unit (4) having an alkali reactive group and being other than said repeating unit (1).

4. The radiation sensitive resin composition according to claim 3 , wherein said repeating unit (3) comprises, as said alkali soluble group, a functional group having a hydrogen atom having a pKa of 4 to 11.

5. The radiation sensitive resin composition according to claim 3 , wherein said repeating unit (3) comprises, as said alkali soluble group, at least one of functional groups represented by the following formulae (3a) to (3c),

wherein, in the formulae, R 8 represents a hydrocarbon group having 1 to 10 carbon atoms substituted with a fluorine atom, and Z represents a fluoromethylene group or an alkylene group having 2 to 20 carbon atoms substituted with a fluorine atom.

6. The radiation sensitive resin composition according to claim 3 , wherein said repeating unit (4) comprises, as said alkali reactive group, a functional group having lactone skeleton or cyclic carbonate structure.

7. The radiation sensitive resin composition according to claim 3 , wherein said polymer (A) comprises, as said repeating unit (4), at least one of repeating units represented by the following general formulae (4a-1) to (4a-6) and a repeating unit represented by the following general formula (4b),

wherein, in the formulae, R 9 represents a hydrogen atom or a methyl group, R 1 ° represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent group, R 11 represents a hydrogen atom or a methoxy group, A represents a single bond, an ether group, an ester group, a carbonyl group, a divalent chained hydrocarbon group having 1 to 30 carbon atoms, a divalent alicyclic hydrocarbon group having 3 to 30 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms, or a divalent group obtained by combination thereof, B represents an oxygen atom or a methylene group, 1 represents an integer of 1 to 3, and m represents 0 or 1,

wherein, in the formula, R 12 represents a hydrogen atom, a methyl group, or a trifluoromethyl group, R 13 represents a hydrogen atom or a chain hydrocarbon group having 1 to 5 carbon atoms, and when a plurality of R 13 is present, each may be the same or different from each other, D represents a single bond, a divalent or trivalent chained hydrocarbon group having 1 to 30 carbon atoms, a divalent or trivalent alicyclic hydrocarbon group having 3 to 30 carbon atoms, or a divalent or trivalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and when D is trivalent, the carbon atom included in D and the carbon atom constituting the cyclic carbonate ester bind to each other to form a ring structure, and n represents an integer of 2 to 4.

8. The radiation sensitive resin composition according to claim 1 , wherein the content of said polymer (A) is in the range from 0.1 to 20 parts by mass based on 100 parts by mass of said polymer (B).

9. A method for forming a resist pattern, comprising:

(1) forming a photoresist film on a substrate by using said radiation sensitive resin composition according to claim 1 ,

(2) subjecting said photoresist film to a liquid immersion exposure process via a liquid immersion medium after setting said liquid immersion medium on said photoresist film,

(3) developing the photoresist film obtained after said liquid immersion exposure process to form a resist pattern.