Radiation-sensitive resin composition

1. A radiation-sensitive resin composition comprising:

a polymer that includes a first structural unit shown by a formula (a1), a second structural unit shown by a formula (a2), and a third structural unit having a lactone structure; and

a photoacid generator, a content of the first structural unit in the polymer being 50 mol % or more based on total structural units included in the polymer,

wherein R 1 represents a hydrogen atom or a methyl group, and

each of R 2 , R 3 , and R 4 independently represents an alkyl group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, or

R 2 represents an alkyl group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, and R 3 and R 4 taken together represent a divalent alicyclic hydrocarbon group having 4 to 20 carbon atoms together with the carbon atom bonded to R 3 and R4,

wherein

R 5 represents a hydrogen atom or a methyl group,

R 6 represents a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms, and

A represents a trivalent organic group.

2. The radiation-sensitive resin composition according to claim 1 , wherein the first structural unit is a structural unit shown by a formula (a1-1),

wherein

each of R 1 and R 2 is a same as defined for the formula (a1), and

p is an integer from 0 to 4.

3. The radiation-sensitive resin composition according to claim 1 , wherein the photoacid generator includes a compound shown by a formula (B1),

wherein

R 7 represents a monovalent hydrocarbon group having 10 or more carbon atoms that includes an alicyclic skeleton, wherein the hydrocarbon group represented by R 7 is unsubstituted or a part or all of hydrogen atoms of the hydrocarbon group represented by R 7 are each substituted with a substituent,

E represents —O—, —CO—O—*, or —O—CO—*, wherein * indicates a site bonded to X,

k is 0 or 1,

X represents a divalent linear or branched alkanediyl group having 1 to 20 carbon atoms, wherein the alkanediyl group represented by X is unsubstituted or a part or all of hydrogen atoms of the alkanediyl group represented by X are each substituted with a substituent, and

M + represents a monovalent onium cation.

4. The radiation-sensitive resin composition according to claim 3 , wherein R 7 of the compound shown by the formula (B1) represents a hydrocarbon group that includes an adamantane skeleton.

5. The radiation-sensitive resin composition according to claim 3 , wherein the compound shown by the formula (B1) is a compound shown by a formula (B1-1),

wherein

each of E, k and M + is a same as defined for the formula (B1),

R 8 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms, wherein the hydrocarbon group represented by R 8 is unsubstituted or a part or all of hydrogen atoms of the hydrocarbon group represented by R 8 are each substituted with a substituent,

q is an integer from 0 to 4, wherein a plurality of R 8 s are either identical or different in a case where q is an integer from 2 to 4,

each of R 9 and R 10 independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 8 carbon atoms, wherein the hydrocarbon group represented by R 9 or R 10 is unsubstituted or a part or all of hydrogen atoms of the hydrocarbon group represented by R 9 or R 10 are each substituted with a substituent,

m is an integer from 0 to 10, wherein each of a plurality of R 9 s and a plurality of R 10 s are either identical or different in a case where m is an integer from 2 to 10,

each of R 11 and R 12 independently represents a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms, and

n is an integer from 1 to 4, wherein each of a plurality of R 11 s and a plurality of R 12 s are either identical or different in a case where n is an integer from 2 to 4.

6. The radiation-sensitive resin composition according to claim 3 , wherein M + of the compound shown by the formula (B1) represents a cation shown by a formula (b1), a cation shown by a formula (b2), or a combination thereof,

wherein

each of R 13 , R 14 and R 15 independently represents a linear or branched alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 18 carbon atoms, wherein the alkyl group or the aryl group represented by R 13 , R 14 and R 15 is unsubstituted or a part or all of hydrogen atoms of the alkyl group or the aryl group represented by R R 13 , R 14 and R 15 are each substituted with a substituent, or

R 13 represents a linear or branched alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 18 carbon atoms, wherein the alkyl group or the aryl group represented by R 13 is unsubstituted or a part or all of hydrogen atoms of the alkyl group or the aryl group represented by R 13 are each substituted with a substituent, and R 14 and R 15 , taken together represent a cyclic structure together with the sulfur atom bonded to R 14 and R 15 ,

R 16 —I + —R 17   (b2)

wherein

each of R 16 and R 17 independently represents a linear or branched alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 18 carbon atoms, wherein the alkyl group or the aryl group represented by R 16 and R 17 is unsubstituted or a part or all of hydrogen atoms of the alkyl group or the aryl group represented by R 16 and R 17 are each substituted with a substituent, or

R 16 and R 17 taken together represent a cyclic structure together with the iodine atom bonded to R 16 and R 17 .