Compound, resin and photoresist composition

A photoresist composition which comprises a resin and an acid generator,

• wherein the resin comprises a structural unit represented by formula (I0), a structural unit represented by formula (a1-1), a structural unit represented by formula (a1-2), a structural unit represented by formula (a2-1) and a structural unit represented by formula (a3-4):
• wherein A1, A2 and A3 each independently represent a C2-C18 divalent hydrocarbon group, R1, R2, R3 and R4 each independently represent a hydrogen atom or a C1-C6 saturated hydrocarbon group, X1 and X2 each independently represent —O—CO—O— or —O—,
• wherein, in formulae (a1-1) and (a1-2), La1 and La2 each independently represents an oxygen atom or *—O—(CH2)k1—CO—O— in which * represents a binding site to —CO—, and k1 represents an integer of 1 to 7;
• Ra4 and Ra5 each independently represent a hydrogen atom or a methyl group;
• Ra6 and Ra7 each independently represent a C1-C8 alkyl group, a C3-C18 alicyclic hydrocarbon group, or a combination of them;
• m1 represents an integer of 0 to 14;
• n1 represents an integer of 0 to 10;
• and n1′ represents 0 to 3,
• wherein, in formula (a2-1), Ra14 represents a hydrogen atom or a methyl group, Ra15 and Ra16 each independently represent a hydrogen atom, a methyl group or a hydroxy group, La3 represents an oxygen atom or *—O—(CH2)k2—CO—O— in which * represents a binding site to —CO—, and k2 represents an integer of 1 to 7, and o1 represents an integer of 0 to 10, and
• wherein, in formula (a3-4), La7 represents a single bond, *-La8-O—, *-La8-CO—, *-La8-CO—O-La9-CO—O—, or *-La8-O—CO-La9-O—;
• * represents a binding site to oxygen group, La8 and La9 each represent a C1-C6 alkanediyl group, Ra25 is in occurrence a carboxyl group, a cyano group or a C1-C4 aliphatic hydrocarbon group, Ra24 represents a hydrogen atom, a halogen atom or a C1-C6 alkyl group optionally having a halogen atom, and w represents an integer of 0 to 8, and
• wherein the photoresist composition further comprises another resin which comprises a structural unit represented by formula (a4-0) and a structural unit represented by formula (a5-1), no structural unit represented by formula (I0) and no structural unit having an acid-labile group:
• wherein, in the formula (a4-0), R5 represents a hydrogen atom or a methyl group, L5 represents a single bond or a C1-C4 saturated aliphatic hydrocarbon group, L3 represents a C1-C8 perfluoroalkanediyl group, or a C3-C12 perfluorocycloalkanediyl group, and R6 represents a hydrogen atom or a fluorine atom,
• wherein, in the formula (a5-1), R51 represents a hydrogen atom or a methyl group;
• R52 represents a C3-C18 alicyclic hydrocarbon group, provided that the alicyclic hydrocarbon group has no substituent on the carbon atom bonded to L55;
• and L55 represents a single bond or a C1-C8 alkanediyl group where a methylene group can be replaced by an oxygen atom or carbonyl group.