Process for producing photoresist pattern and photoresist composition

A process for producing a photoresist pattern comprising steps (1) to (5);

• (1) applying a photoresist composition onto a substrate, said photoresist composition comprising an acid generator and a resin which comprises a structural unit having an acid-labile group;
• (2) drying the applied composition to form a composition layer;
• (3) exposing the composition layer;
• (4) heating the exposed composition layer;
• and
• (5) developing the heated composition layer with a developer which comprises butyl acetate,
• wherein a distance of Hansen solubility parameters between the resin and butyl acetate is from 3.3 to 4.3,
• the distance is calculated from formula (1):
• R=(4×(δdR−15.8)2+(δpR−3.7)2+(δhR−6.3)2)1/2 (1)
• in which δdR represents a dispersion parameter of a resin, δpR represents a polarity parameter of a resin, δhR represents a hydrogen bonding parameter of a resin, and R represents a distance of Hansen solubility parameters,
• a film retention ratio of an exposed portion in the photoresist pattern relative to the composition layer is adjusted to 65% or more,
• the resin comprises
• a structural unit represented by formula (a1-1) and
• at least one selected from the group consisting of a structural unit represented by formula (a1-0) and a structural unit represented by formula (a1-2):
• wherein, in each formula,
• La01, La1 and La2 independently represent —O— or *—O—(CH2)k01—CO—O—, where k01 represents an integer of 1 to 7, and * represents a binding position to —CO—, Ra01, Ra4 and Ra5 independently represent a hydrogen atom or a methyl group, and Ra02, Ra03 and Ra04 independently represent a C1 to C8 alkyl group, a C3 to C18 alicyclic hydrocarbon group or combination thereof,
• Ra6 and Ra7 independently represents a C1 to C8 alkyl group, a C3 to C18 alicyclic hydrocarbon group or a combination thereof,
• m1 represents an integer of 0 to 14,
• n1 represents an integer of 0 to 10, and
• n1′ represents an integer of 0 to 3, and
• the total proportion of the structural unit represented by formula (a1-1) is 35% by mole or less with respect to the total structural units of the resin, and
• the total proportion of the structural unit represented by formula (a1-0) and the structural unit represented by formula (a1-2) is 50% by mole or more with respect to all of the structural units having an acid-labile group, and
• a structural unit represented by formula (a3-4):
• wherein Ra24 represents a hydrogen atom, a halogen atom or a C1 to C6 alkyl group which can have a halogen atom,
• La7 represents —O—, *—O-La8-O—, *—O-La8-CO—O—, *—O-La8-CO—O-La9-CO—O— or *—O-La8-O—CO-La9-O— where * represents a binding position to a carbonyl group, La8 and La9 independently represents a C1 to C6 alkanediyl group, and Ra25 in each occurrence represents a carboxy group, a cyano group or a C1 to C4 aliphatic hydrocarbon group, and
• w1 represents an integer of 0 to 8, and
• the proportion of the structural unit represented by formula (a3-4) is 30% by mole or more with respect to the total structural units of the resin, and
• the photoresist composition further comprises a resin comprising a structural unit represented by formula (a4-0):
• wherein R5 represents a hydrogen atom or a methyl group,
• L5 represent a single bond or a C1 to C4 saturated aliphatic hydrocarbon group, L3 represents a C1 to C8 perfluoroalkanediyl group or a C3 to C12 perfluorocycloalkanediyl group, and R6 represents a hydrogen atom or a fluorine atom, and
• a structural unit represented by formula (a5-1):
• wherein R51 represents a hydrogen atom or a methyl group,
• R52 represents a C3 to C18 alicyclic hydrocarbon group where a hydrogen atom can be replaced by a C1 to C8 aliphatic hydrocarbon group or a hydroxy group, provided that a hydrogen atom contained in the carbon atom bonded to L55 is not replaced by the C1 to C8 aliphatic hydrocarbon group, and
• L55 represents a single bond or a C1 to C18 divalent saturated hydrocarbon group where a methylene group can be replaced by an oxygen atom or a carbonyl group.