Resist material and patterning process

1 . A resist material comprising a base polymer and an acid generator, wherein the resist material contains, as the acid generator, a sulfonium salt or iodonium salt of a sulfonic acid bonded to a maleimide group represented by the following general formula (A-1) or (A-2),

wherein R 1 and R 2 each represent a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, or a branched, or cyclic alkyl group having 3 to 10 carbon atoms, R 1 and R 2 optionally being bonded to each other to form a ring; X represents a divalent linking group containing an ester bond and having 1 to 20 carbon atoms, the linking group optionally containing an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom; Rf 11 to Rf 14 each independently represent a hydrogen atom, a fluorine atom, an oxygen atom, a methyl group, or a trifluoromethyl group, provided that at least one of Rf 11 to Rf 14 is a fluorine atom or a trifluoromethyl group, and that when Rf 11 and Rf 12 are respectively an oxygen atom, Rf 11 and Rf 12 are a single oxygen atom bonded to a single carbon atom to form a carbonyl group; R 3 , R 4 , R 5 , R 6 , and R 7 each independently represent a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or a hydrocarbyl group having 1 to 25 carbon atoms and optionally containing a heteroatom, wherein the hydrocarbyl group is saturated or unsaturated and is linear, branched, or cyclic, some or all hydrogen atoms of these groups are optionally substituted with a hydroxy group, a carboxy group, a halogen atom, a cyano group, a nitro group, a mercapto group, a sultone group, a sulfonic group, or a sulfonium salt-containing group, and some carbon atoms of these groups are optionally substituted with an ether bond, an ester bond, a carbonyl group, an amide bond, a carbonate group, or a sulfonic acid ester group; and R 3 and R 4 are optionally bonded with each other to form a ring with a sulfur atom that is bonded thereto.

2 . The resist material according to claim 1 , further comprising one or more selected from an organic solvent and a surfactant.

3 . The resist material according to claim 1 , wherein the base polymer further contains at least one repeating unit selected from repeating units represented by the following general formulae (f1) to (f3),

wherein each R A independently represents a hydrogen atom or a methyl group; Z 1 represents a single bond, a phenylene group, a naphthylene group, —Z 11 —, —O—Z 11 —, —C(═O)—O—Z 11 —, or —C(═O)—NH—Z 11 —; Z 11 represents an alkanediyl group having 1 to 6 carbon atoms, an alkenediyl group having 2 to 6 carbon atoms, or a hydrocarbon group having 1 to 20 carbon atoms and optionally containing a phenylene group and optionally contains a carbonyl group, an ester bond, an ether bond, or a hydroxy group; Z 2A represents a single bond or an ester bond; Z 2B represents a single bond or a divalent group having 1 to 18 carbon atoms and optionally contains an ester bond, an ether bond, a lactone ring, a bromine atom, or an iodine atom; Z 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, —O—Z 31 —, —C(═O)—O—Z 31 —, or —C(═O)—NH—Z 31 —; Z 31 represents an alkanediyl group having 1 to 15 carbon atoms, an alkenediyl group having 2 to 15 carbon atoms, or a group containing a phenylene group and optionally contains a carbonyl group, an ester bond, an ether bond, a hydroxy group, or a halogen atom; Rf 1 to Rf 4 each independently represent a hydrogen atom, a fluorine atom, an oxygen atom, or a trifluoromethyl group, provided that at least one is a fluorine atom, and that when Rf and Rf 2 are respectively an oxygen atom, Rf 1 and Rf 2 are a single oxygen atom bonded to a single carbon atom to form a carbonyl group; R 21 to R 28 each independently represent a monovalent hydrocarbon group having 1 to 25 carbon atoms and optionally containing a heteroatom; any two of R 23 , R 24 , and R 25 or any two of R 26 , R 27 , and R 28 are optionally bonded with each other to form a ring with a sulfur atom that is bonded thereto; and M − represents a non-nucleophilic counter ion.

4 . The resist material according to claim 2 , wherein the base polymer further contains at least one repeating unit selected from repeating units represented by the following general formulae (f1) to (f3),

wherein each R A independently represents a hydrogen atom or a methyl group; Z 1 represents a single bond, a phenylene group, a naphthylene group, —Z 11 —, —O—Z 11 —, —C(═O)—O—Z 11 —, or —C(═O)—NH—Z 11 —; Z 11 represents an alkanediyl group having 1 to 6 carbon atoms, an alkenediyl group having 2 to 6 carbon atoms, or a hydrocarbon group having 1 to 20 carbon atoms and optionally containing a phenylene group and optionally contains a carbonyl group, an ester bond, an ether bond, or a hydroxy group; Z 2A represents a single bond or an ester bond; Z 2B represents a single bond or a divalent group having 1 to 18 carbon atoms and optionally contains an ester bond, an ether bond, a lactone ring, a bromine atom, or an iodine atom; Z 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, —O—Z 31 —, —C(═O)—O—Z 31 —, or —C(═O)—NH—Z 31 —; Z 31 represents an alkanediyl group having 1 to 15 carbon atoms, an alkenediyl group having 2 to 15 carbon atoms, or a group containing a phenylene group and optionally contains a carbonyl group, an ester bond, an ether bond, a hydroxy group, or a halogen atom; Rf 1 to Rf 4 each independently represent a hydrogen atom, a fluorine atom, an oxygen atom, or a trifluoromethyl group, provided that at least one is a fluorine atom, and that when Rf and Rf 2 are respectively an oxygen atom, Rf 1 and Rf 2 are a single oxygen atom bonded to a single carbon atom to form a carbonyl group; R 21 to R 28 each independently represent a monovalent hydrocarbon group having 1 to 25 carbon atoms and optionally containing a heteroatom; any two of R 23 , R 24 , and R 25 or any two of R 26 , R 27 , and R 28 are optionally bonded with each other to form a ring with a sulfur atom that is bonded thereto; and M − represents a non-nucleophilic counter ion.

5 . The resist material according to claim 1 , wherein the base polymer contains a repeating unit represented by the following general formula (a1) or a repeating unit represented by the following general formula (a2),

wherein each R A independently represents a hydrogen atom or a methyl group; X 1 represents a single bond or a linking group having 1 to 12 carbon atoms containing a phenylene group, a naphthylene group, an ester bond, an ether bond, or a lactone ring; X 2 represents a single bond or an ester bond; X 3 represents a single bond, an ether bond, or an ester bond; R 11 and R 12 each represent an acid-labile group; R 13 represents a fluorine atom, a trifluoromethyl group, a cyano group, a saturated hydrocarbyl group having 1 to 6 carbon atoms, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 7 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 7 carbon atoms, or a saturated hydrocarbyloxycarbonyl group having 2 to 7 carbon atoms; R 14 represents a single bond or an alkanediyl group having 1 to 6 carbon atoms, and some of the carbon atoms are optionally substituted with an ether bond or an ester bond; and “a” represents 1 or 2 and “b” represents an integer of 0 to 4, provided that 1≤a+b≤5.

6 . The resist material according to claim 5 , further comprising a dissolution inhibitor.

7 . The resist material according to claim 5 , being a chemically amplified positive resist material.

8 . The resist material according to claim 1 , wherein the base polymer does not contain an acid-labile group.

9 . The resist material according to claim 8 , further comprising a crosslinking agent.

10 . The resist material according to claim 8 , being a chemically amplified negative resist material.

11 . A patterning process comprising the steps of:

(1) forming a resist film on a substrate by using the resist material according to claim 1 ;

(2) exposing the resist film to a high-energy beam; and

(3) developing the exposed resist film by using a developer.

12 . The patterning process according to claim 11 , wherein after the step (1) and before the step (2), (1′) an entire surface of the resist film is exposed to light having a wavelength at which the sulfonium salt or iodonium salt of the sulfonic acid bonded to the maleimide group does not decompose.

13 . The patterning process according to claim 12 , wherein the wavelength at which the sulfonium salt or iodonium salt does not decompose is longer than a wavelength of 300 nm.

14 . The patterning process according to claim 11 , wherein the high-energy beam is a KrF excimer laser beam, an ArF excimer laser beam, an electron beam, or an extreme ultraviolet ray having a wavelength of 3 to 15 nm.