SALT, ACID GENERATOR, RESIST COMPOSITION AND METHOD FOR PRODUCING RESIST PATTERN

Abstract

A salt represented by formula (I), an acid generator and a resist composition:

##STR00001##

wherein R.sup.1, R.sup.2 and R.sup.3 each represent a hydroxy group, —O—R.sup.10, —O—CO—O—R.sup.10, —O-L.sup.1-CO—O—R.sup.10; R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 each represent a halogen atom, a hydroxy group, etc.; L.sup.1 represents an alkanediyl group; R.sup.10 represents an acid-labile group; X.sup.1, X.sup.2 and X.sup.3 each represent an oxygen atom or a sulfur atom; m1 and m7 represent an integer of 0 to 5, m2 to m6 and m8, m9 represent an integer of 0 to 4, in which 0≤m1+m7≤5, 0≤m2+m8≤4, 0≤m3+m9≤4, and at least one of m1, m2 and m3 represents an integer of 1 or more; X.sup.4 represents a single bond, —CH.sub.2—, —O—, —S—, etc.; and AI.sup.− represents an organic anion.

Claims

1. A salt represented by formula (I): ##STR00291## wherein, in formula (I), R.sup.1, R.sup.2 and R.sup.3 each independently represent a hydroxy group, —O—R.sup.10, —O—CO—O—R.sup.10, —O-L.sup.1-CO—O—R.sup.10, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 each independently represent a halogen atom, a hydroxy group, an alkyl fluoride group having 1 to 12 carbon atoms or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and —CH.sub.2— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO.sub.2—, L.sup.1 represents an alkanediyl group having 1 to 6 carbon atoms, R.sup.10 represents an acid-labile group, X.sup.1, X.sup.2 and X.sup.3 each independently represent an oxygen atom or a sulfur atom, m1 represents an integer of 0 to 5, and when m1 is 2 or more, a plurality of groups in parentheses may be the same or different from each other, m2 represents an integer of 0 to 4, and when m2 is 2 or more, a plurality of groups in parentheses may be the same or different from each other, m3 represents an integer of 0 to 4, and when m3 is 2 or more, a plurality of groups in parentheses may be the same or different from each other, m4 represents an integer of 0 to 4, and when m4 is 2 or more, a plurality of R.sup.4 may be the same or different from each other, m5 represents an integer of 0 to 4, and when m5 is 2 or more, a plurality of R.sup.5 may be the same or different from each other, m6 represents an integer of 0 to 4, and when m6 is 2 or more, a plurality of R.sup.6 may be the same or different from each other, m7 represents an integer of 0 to 5, and when m7 is 2 or more, a plurality of R.sup.7 may be the same or different from each other, m8 represents an integer of 0 to 4, and when m8 is 2 or more, a plurality of R.sup.8 may be the same or different from each other, m9 represents an integer of 0 to 4, and when m9 is 2 or more, a plurality of R.sup.9 may be the same or different from each other, in which 0≤m1+m7≤5, 0≤m2+m8≤4, 0≤m3+m9≤4, and at least one of m1, m2 and m3 represents an integer of 1 or more, X.sup.4 represents a single bond, —CH.sub.2—, —O—, —S—, —CO—, —SO— or —SO.sub.2—, and AI.sup.− represents an organic anion.

2. The salt according to claim 1, wherein X.sup.1, X.sup.2 and X.sup.3 are an oxygen atom.

3. The salt according to claim 1, wherein R.sup.1, R.sup.2 and R.sup.3 each independently represent —O—R.sup.10, —O—CO—O—R.sup.10, —O-L.sup.1-CO—O—R.sup.10, the acid-labile group as for R.sup.10 is a group represented by formula (1a) or a group represented by formula (2a): ##STR00292## wherein, in formula (1a), R.sup.aa1, R.sup.aa2 and R.sup.aa3 each independently represent an alkyl group having 1 to 8 carbon atoms which may have a substituent, an alkenyl group having 2 to 8 carbon atoms which may have a substituent, an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, or R.sup.aa1 and R.sup.aa2 are bonded to each other to form an alicyclic hydrocarbon group having 3 to 20 carbon atoms together with carbon atoms to which R.sup.aa1 and R.sup.aa2 are bonded, and * represents a bond: ##STR00293## wherein, in formula (2a), R.sup.aa1′ and R.sup.aa2′ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R.sup.aa3′ represents a hydrocarbon group having 1 to 20 carbon atoms, or R.sup.aa2′ and R.sup.aa3′ are bonded to each other to form a heterocyclic group having 3 to 20 carbon atoms together with —C—X.sup.a— to which R.sup.aa2′ and R.sup.aa3′ are bonded, and —CH.sub.2— included in the hydrocarbon group and the heterocyclic group may be replaced by —O— or —S—, X.sup.a represents an oxygen atom or a sulfur atom, and * represents a bond.

4. The salt according to claim 1, wherein at least one of R.sup.1, R.sup.2 and R.sup.3 is the hydroxy group.

5. The salt according to claim 1, wherein m1 is 0, 1 or 2, m2 is 0 or 1 and m3 is 0 or 1.

6. The salt according to claim 1, wherein m1 is 1 or more, at least one of the bonding sites of X.sup.1 is m-position or p-position with respect to a bonding site of S.sup.+.

7. The salt according to claim 1, wherein m1 is 0 or 1, m2 and m3 are 1 and more, at least one of the bonding sites of X.sup.2 is m-position or p-position with respect to a bonding site of S.sup.+, at least one of the bonding sites of X.sup.3 is m-position or p-position with respect to a bonding site of S.sup.+.

8. The salt according to claim 1, wherein m1 is 1 and more, m2 is 1 and more, and m3 is 1 and more.

9. The salt according to claim 8, wherein R.sup.1, R.sup.2 and R.sup.3 represent a hydroxy group.

10. The salt according to claim 8, wherein R.sup.1, R.sup.2 and R.sup.3 represent —O—R.sup.10.

11. The salt according to claim 8, wherein R.sup.1, R.sup.2 and R.sup.3 represent —O-L.sup.1-CO—O—R.sup.10.

12. The salt according to claim 1, wherein AI.sup.− is a sulfonic acid anion, a sulfonylimide anion, a sulfonylmethide anion or a carboxylic acid anion.

13. The salt according to claim 1, wherein AI.sup.− is a sulfonic acid anion, and the sulfonic acid anion is an anion represented by formula (I-A): ##STR00294## wherein, in formula (I-A), Q.sup.1 and Q.sup.2 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, L.sup.1 represents a saturated hydrocarbon group having 1 to 24 carbon atoms, —CH.sub.2— included in the saturated hydrocarbon group may be replaced by —O— or —CO—, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and Y.sup.1 represents a methyl group which may have a substituent or an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and —CH.sub.2— included in the alicyclic hydrocarbon group may be replaced by —O—, —SO.sub.2— or —CO—.

14. An acid generator comprising the salt according to claim 1.

15. A resist composition comprising the acid generator according to claim 14 and a resin having an acid-labile group.

16. The resist composition according to claim 15, wherein the resin having an acid-labile group includes at least one selected from the group consisting of a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2): ##STR00295## wherein, in formula (a1-1) and formula (a1-2), L.sup.a1 and L.sup.a2 each independently represent —O— or *—O—(CH.sub.2).sub.k1—CO—O—, k1 represents an integer of 1 to 7, and * represents a bond to —CO—, R.sup.a4 and R.sup.a5 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, R.sup.a6 and R.sup.a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups, 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.

17. The resist composition according to claim 15, wherein the resin having an acid-labile group includes a structural unit represented by formula (a2-A): ##STR00296## wherein, in formula (a2-A), R.sup.a50 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, R.sup.a51 represents a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group, A.sup.a50 represents a single bond or *—X.sup.a51-(A.sup.a52-X.sup.a52).sub.nb—, and * represents a bond to carbon atoms to which —R.sup.a50 is bonded, A.sup.a52 represents an alkanediyl group having 1 to 6 carbon atoms, X.sup.a51 and X.sup.a52 each independently represent —O—, —CO—O— or —O—CO—, nb represents 0 or 1, and mb represents an integer of 0 to 4, and when mb is an integer of 2 or more, a plurality of R.sup.a51 may be the same or different from each other.

18. The resist composition according to claim 15, further comprising a salt generating an acid having an acidity lower than that of an acid generated from the acid generator.

19. A method for producing a resist pattern, which comprises: (1) a step of applying the resist composition according to claim 15 on a substrate, (2) a step of drying the applied resist composition to form a composition layer, (3) a step of exposing the composition layer, (4) a step of heating the exposed composition layer, and (5) a step of developing the heated composition layer.

Description

EXAMPLES

[0812] The present invention will be described more specifically by way of Examples. Percentages and parts expressing the contents or amounts used in the Examples are by mass unless otherwise specified.

[0813] The weight-average molecular weight is a value determined by gel permeation chromatography. Analysis conditions of gel permeation chromatography are as follows.

[0814] Column: TSKgel Multipore HXL-M×3+guardcolumn (manufactured by TOSOH CORPORATION)

[0815] Eluent: tetrahydrofuran

[0816] Flow rate: 1.0 mL/min

[0817] Detector: RI detector

[0818] Column temperature: 40° C.

[0819] Injection amount: 100 μl

[0820] Molecular weight standards: polystyrene standard (manufactured by TOSOH CORPORATION)

[0821] Structures of compounds were confirmed by measuring a molecular ion peak using mass spectrometry (Liquid Chromatography: Model 1100, manufactured by Agilent Technologies, Inc., Mass Spectrometry: Model LC/MSD, manufactured by Agilent Technologies, Inc.). The value of this molecular ion peak in the following Examples is indicated by “MASS”.

Example 1: Synthesis of Salt Represented by Formula (I-8)

[0822] ##STR00262##

[0823] 20 Parts of a salt represented by formula (I-8-a), 2.28 parts of a compound represented by formula (I-8-c), 100 parts of ethyl acetate and 15 parts of tetrahydrofuran were mixed, followed by stirring at 23° C. for 30 minutes. To the mixed solution thus obtained, 6.55 parts of a compound represented by formula (I-8-b) was added, followed by stirring at 23° C. for 18 hours. To the reaction mass thus obtained, 20 parts of n-heptane and 70 parts of ion-exchanged water were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus recovered, 60 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated four times. The organic layer thus obtained was concentrated and then the concentrated mass was isolated from a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Inc., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 7.48 parts of a compound represented by formula (I-8-d).

##STR00263##

[0824] 0.95 Part of a compound represented by formula (I-8-d) and 10 parts of tetrahydrofuran were mixed, and after stirring at 23° C. for 30 minutes and further cooling to 5° C., 0.14 part of sodium hydride was added. To the mixture thus obtained, 1.81 parts of a salt represented by formula (I-8-e) was added, followed by stirring at 5° C. for 3 hours. To the mixture thus obtained, 6.30 parts of IN hydrochloric acid was added, followed by raising the temperature to 23° C. and further stirring at 23° C. for 6 hours. To the mixture thus obtained, 30 parts of chloroform and 15 parts of ion-exchanged water were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. The organic layer thus obtained was concentrated and then 1 part of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 1.52 parts of a salt represented by formula (I-8-f).

##STR00264##

[0825] 0.76 Part of a salt represented by formula (I-8-f), 1.20 parts of a salt represented by formula (I-8-g) and 20 parts of chloroform were added, followed by stirring at 23° C. for 3 hours. To the reaction product thus obtained, 15 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 15 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 1.5 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 1.11 parts of a salt represented by formula (I-8).

[0826] MASS (ESI (+) Spectrum): M.sup.+ 369.1

[0827] MASS (ESI (−) Spectrum): M.sup.+ 517.1

Example 2: Synthesis of Salt Represented by Formula (I-312)

[0828] ##STR00265##

[0829] 0.95 Part of a salt represented by formula (I-8-f) and 30 parts of dimethylformamide were mixed, and after stirring at 23° C. for 30 minutes, 0.16 part of potassium carbonate and 0.05 part of potassium iodide were added, followed by raising the temperature to 75° C. To the mixture thus obtained, 1.13 parts of a compound represented by formula (I-312-a) was added, followed by stirring at 75° C. for 5 hours and further cooling to 23° C. To the mixture thus obtained, 50 parts of chloroform and 20 parts of an aqueous 5% oxalic acid solution was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated to obtain 1.22 parts of a salt represented by formula (I-312-b).

##STR00266##

[0830] 0.98 Part of a salt represented by formula (I-312-b), 1.02 parts of a salt represented by formula (I-8-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.29 parts of a salt represented by formula (I-312).

[0831] MASS (ESI (+) Spectrum): M.sup.+ 575.2

[0832] MASS (ESI (−) Spectrum): M.sup.− 517.1

Example 3: Synthesis of Salt Represented by Formula (I-4)

[0833] ##STR00267##

[0834] 0.76 Part of a salt represented by formula (I-8-f), 0.78 part of a salt represented by formula (I-4-g) and 20 parts of chloroform was added, followed by stirring at 23° C. for 3 hours. To the reaction product thus obtained, 15 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 15 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 1.5 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 1.02 parts of a salt represented by formula (I-4).

[0835] MASS (ESI (+) Spectrum): M.sup.+ 369.1

[0836] MASS (ESI (−) Spectrum): M.sup.− 311.0

Example 4: Synthesis of Salt Represented by Formula (I-308)

[0837] ##STR00268##

[0838] 0.98 Part of a salt represented by formula (I-312-b), 0.66 part of a salt represented by formula (I-4-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 0.99 part of a salt represented by formula (I-308).

[0839] MASS (ESI (+) Spectrum): M.sup.+ 575.2

[0840] MASS (ESI (−) Spectrum): M.sup.− 311.0

Example 5: Synthesis of Salt Represented by Formula (I-320)

[0841] ##STR00269##

[0842] 0.98 Part of a salt represented by formula (I-312-b), 0.91 part of a salt represented by formula (I-320-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.34 parts of a salt represented by formula (I-320).

[0843] MASS (ESI (+) Spectrum): M.sup.+ 575.2

[0844] MASS (ESI (−) Spectrum): M.sup.− 467.1

Example 6: Synthesis of Salt Represented by Formula (I-328)

[0845] ##STR00270##

[0846] 0.98 Part of a salt represented by formula (I-312-b), 1.46 parts of a salt represented by formula (I-328-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.92 parts of a salt represented by formula (I-328).

[0847] MASS (ESI (+) Spectrum): M.sup.+ 575.2

[0848] MASS (ESI (−) Spectrum): M.sup.− 793.3

Example 7: Synthesis of Salt Represented by Formula (I-339)

[0849] ##STR00271##

[0850] 0.98 Part of a salt represented by formula (I-312-b), 0.84 part of a salt represented by formula (I-339-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.14 parts of a salt represented by formula (I-339).

[0851] MASS (ESI (+) Spectrum): M.sup.+ 575.2

[0852] MASS (ESI (−) Spectrum): M.sup.− 423.1

Example 8: Synthesis of Salt Represented by Formula (I-1992)

[0853] ##STR00272##

[0854] 0.95 Part of a compound represented by formula (I-8-d) and 10 parts of tetrahydrofuran were mixed, and after stirring at 23° C. for 30 minutes and further cooling to 5° C., 0.14 part of sodium hydride was added. To the mixture thus obtained, 1.81 parts of a salt represented by formula (I-8-e) was added, followed by stirring at 5° C. for 3 hours and further stirring at 23° C. for 1 hour. To the mixture thus obtained, 30 parts of chloroform and 15 parts of ion-exchanged water were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 1.89 parts of a salt represented by formula (I-1992-f).

##STR00273##

[0855] 0.76 Part of a salt represented by formula (I-1992-f), 0.91 part of a salt represented by formula (I-320-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.11 parts of a salt represented by formula (I-1992).

[0856] MASS (ESI (+) Spectrum): M.sup.+ 441.2

[0857] MASS (ESI (−) Spectrum): M.sup.− 467.1

Example 9: Synthesis of Salt Represented by Formula (I-2182)

[0858] ##STR00274##

[0859] 1.01 Parts of a compound represented by formula (I-2182-d) and 10 parts of tetrahydrofuran were mixed, and after stirring at 23° C. for 30 minutes and further cooling to 5° C., 0.14 part of sodium hydride was added. To the mixture thus obtained, 1.81 parts of a salt represented by formula (I-8-e) was added, followed by stirring at 5° C. for 3 hours and further stirring at 23° C. for 1 hour. To the mixture thus obtained, 30 parts of chloroform and 15 parts of ion-exchanged water were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 2.02 parts of a salt represented by formula (I-2182-f).

##STR00275##

[0860] 0.78 Part of a salt represented by formula (I-2182-f), 0.91 part of a salt represented by formula (I-320-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.23 parts of a salt represented by formula (I-2182).

[0861] MASS (ESI (+) Spectrum): M.sup.+ 453.2

[0862] MASS (ESI (−) Spectrum): M.sup.− 467.1

Example 10: Synthesis of Salt Represented by Formula (I-1612)

[0863] ##STR00276##

[0864] 2.10 Parts of a compound represented by formula (I-8-d) and 20 parts of tetrahydrofuran were mixed, and after stirring at 23° C. for 30 minutes and further cooling to 5° C., 0.28 part of sodium hydride was added. To the mixture thus obtained, 1.91 parts of a salt represented by formula (I-1612-e) was added, followed by stirring at 5° C. for 3 hours. To the mixture thus obtained, 12.60 parts of IN hydrochloric acid was added, followed by temperature rising to 23° C. and further stirring at 23° C. for 6 hours. To the mixture thus obtained, 50 parts of chloroform and 25 parts of ion-exchanged water were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 2.42 parts of a salt represented by formula (I-1612-f).

##STR00277##

[0865] 0.82 Part of a salt represented by formula (I-1612-f), 0.91 part of a salt represented by formula (I-320-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.29 parts of a salt represented by formula (I-1612).

[0866] MASS (ESI (+) Spectrum): M.sup.+ 477.1

[0867] MASS (ESI (−) Spectrum): M.sup.− 467.1

Example 11: Synthesis of Salt Represented by Formula (I-1232)

[0868] ##STR00278##

[0869] 1.20 Parts of a salt represented by formula (I-1612-f) and 30 parts of dimethylformamide were mixed, and after stirring at 23° C. for 30 minutes, 0.32 part of potassium carbonate and 0.10 part of potassium iodide was added, followed by temperature rising to 75° C. To the mixture thus obtained, 1.36 parts of a compound represented by formula (I-312-a) was added, followed by stirring at 75° C. for 5 hours and further cooling to 23° C. To the mixture thus obtained, 50 parts of chloroform and 20 parts of an aqueous 5% oxalic acid solution were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated to obtain 1.89 parts of a compound represented by formula (I-1232-f).

##STR00279##

[0870] 1.48 Parts of a salt represented by formula (I-1232-f), 0.91 part of a salt represented by formula (I-320-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 2.01 parts of a salt represented by formula (I-1232).

[0871] MASS (ESI (+) Spectrum): M.sup.+ 889.4

[0872] MASS (ESI (−) Spectrum): M.sup.− 467.1

Example 12: Synthesis of Salt Represented by Formula (I-1650)

[0873] ##STR00280##

[0874] 3.15 Parts of a compound represented by formula (I-8-d) and 30 parts of tetrahydrofuran were mixed, and after stirring at 23° C. for 30 minutes and further cooling to 5° C., 0.42 part of sodium hydride was added. To the mixture thus obtained, 2.01 parts of a salt represented by formula (I-1650-e) was added, followed by stirring at 5° C. for 3 hours. To the mixture thus obtained, 18.90 parts of IN hydrochloric acid was added, followed by temperature rising to 23° C. and further stirring at 23° C. for 6 hours. To the mixture thus obtained, 100 parts of chloroform and 50 parts of ion-exchanged water were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. The organic layer thus obtained was concentrated and then 5 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 3.11 parts of a salt represented by formula (I-1650-f).

##STR00281##

[0875] 0.99 Part of a salt represented by formula (I-1650-f), 0.91 part of a salt represented by formula (I-320-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 1.43 parts of a salt represented by formula (I-1650).

[0876] MASS (ESI (+) Spectrum): M.sup.+ 585.1

[0877] MASS (ESI (−) Spectrum): M.sup.− 467.1

Example 13: Synthesis of Salt Represented by Formula (I-1270)

[0878] ##STR00282##

[0879] 1.45 Parts of a salt represented by formula (I-1650-f) and 30 parts of dimethylformamide were mixed, and after stirring at 23° C. for 30 minutes, 0.48 part of potassium carbonate and 0.15 part of potassium iodide was added, followed by temperature rising to 75° C. To the mixture thus obtained, 2.04 parts of a compound represented by formula (I-312-a) was added, followed by stirring at 75° C. for 5 hours and further cooling to 23° C. To the mixture thus obtained, 50 parts of chloroform and 20 parts of an aqueous 5% oxalic acid solution were added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated to obtain 2.42 parts of a salt represented by formula (I-1270-f).

##STR00283##

[0880] 1.98 Parts of a salt represented by formula (I-1270-f), 0.91 part of a salt represented by formula (I-320-g), 30 parts of chloroform and 15 parts of ethyl acetate were mixed, followed by stirring at 23° C. for 2 hours. To the mixture thus obtained, 20 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 30 parts of tert-butyl methyl ether was added to the concentrated residue, followed by stirring at 23° C. for 30 minutes and further filtration to obtain 2.29 parts of a salt represented by formula (I-1232).

[0881] MASS (ESI (+) Spectrum): M.sup.+ 1203.5

[0882] MASS (ESI (−) Spectrum): M.sup.− 467.1

Synthesis of Resin

[0883] Compounds (monomers) used in synthesis of a resin (A) are shown below. Hereinafter, these compounds are referred to as “monomer (a1-1-3)” according to the formula number.

##STR00284##

Synthesis Example 1 [Synthesis of Resin A1]

[0884] Using a monomer (a1-4-2), a monomer (a1-1-3) and a monomer (a1-2-6) as monomers, these monomers were mixed in a molar ratio of 38:24:38 [monomer (a1-4-2):monomer (a1-1-3):monomer (a1-2-6)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile as an initiator was added in the amounts of 7 mol % based on the total molar number of all monomers, and then the polymerization was performed by heating at 85° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous p-toluenesulfonic acid solution (2.5% by weight) was added in the amount of 2.0 mass times the total mass of all monomers, followed by stirring for 6 hours and further isolation through separation. The organic layer thus obtained was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A1 (copolymer) having a weight-average molecular weight of about 5.3×10.sup.3 in a yield of 78%. This resin A1 has the following structural units.

##STR00285##

Synthesis Example 2 [Synthesis of Resin A2]

[0885] Using a monomer (a1-4-2) and a monomer (a1-2-6) as monomers, these monomers were mixed in a molar ratio of 38:62 [monomer (a1-4-2):monomer (a1-2-6)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile as an initiator was added in the amounts of 7 mol % based on the total molar number of all monomers, and then the polymerization was performed by heating at 85° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous p-toluenesulfonic acid solution (2.5% by weight) was added in the amount of 2.0 mass times the total mass of all monomers, followed by stirring for 6 hours and further isolation through separation. The organic layer thus obtained was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A2 (copolymer) having a weight-average molecular weight of about 5.4×10.sup.3 in a yield of 89%. This resin A2 has the following structural units.

##STR00286##

Synthesis Example 3 [Synthesis of Resin A3]

[0886] Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2) and a monomer (a1-4-2) as monomers, these monomers were mixed in a molar ratio of 20:35:3:15:27 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):monomer (a1-4-2)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the total molar number of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous p-toluenesulfonic acid solution (2.5% by weight) was added in the amount of 2.0 mass times the total mass of all monomers, followed by stirring for 12 hours and further isolation through separation. The organic layer thus obtained was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A3 having a weight-average molecular weight of about 5.3×10.sup.3 in a yield of 63%. This resin A3 has the following structural units.

##STR00287##

Synthesis Example 4 [Synthesis of Resin A4]

[0887] Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2) and a monomer (a1-4-13) as monomers, these monomers were mixed in a molar ratio of 20:35:3:15:27 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):monomer (a1-4-13)], these monomers were mixed in a molar ratio of 20:35:3:15:27 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):monomer (a1-4-13)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the total molar number of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous p-toluenesulfonic acid solution (2.5% by weight) was added in the amount of 2.0 mass times the total mass of all monomers, followed by stirring for 12 hours and further isolation through separation. The organic layer thus obtained was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A4 having a weight-average molecular weight of about 5.1×10.sup.3 in a yield of 61%. This resin A4 has the following structural units.

##STR00288##

<Preparation of Resist Composition>

[0888] As shown in Table 2, the following components were mixed and the mixture thus obtained was filtered through a fluororesin filter having a pore diameter of 0.2 μm to prepare resist compositions.

TABLE-US-00002 TABLE 2 Resist Acid composition Resin generator Salt (I) Quencher (C) PB/PEB Composition 1 A1 = 10 parts — I-312 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 2 A2 = 10 parts — I-312 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 3 A2 = 10 parts — I-4 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 4 A2 = 10 parts — I-8 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 5 A2 = 10 parts — I-308 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 6 A2 = 10 parts — I-320 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 7 A2 = 10 parts — I-328 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 8 A2 = 10 parts — I-339 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 9 A2 = 10 parts — I-1992 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 10 A2 = 10 parts — I-2182 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 11 A2 = 10 parts — I-1612 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 12 A2 = 10 parts — I-1232 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 13 A2 = 10 parts — I-1650 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 14 A2 = 10 parts — I-1270 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 15 A4 = 10 parts — I-312 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 16 A3 = 10 parts — I-312 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 17 A3 = 10 parts — I-4 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 18 A3 = 10 parts — I-8 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 19 A3 = 10 parts — I-308 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 20 A3 = 10 parts — I-320 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 21 A3 = 10 parts — I-328 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 22 A3 = 10 parts — I-339 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 23 A3 = 10 parts — I-1992 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 24 A3 = 10 parts — I-2182 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 25 A3 = 10 parts — I-1612 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 26 A3 = 10 parts — I-1232 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 27 A3 = 10 parts — I-1650 = 1.5 parts C1 = 0.35 part 100° C./130° C. Composition 28 A3 = 10 parts — I-1270 = 1.5 parts C1 = 0.35 part 100° C./130° C. Comparative A2 = 10 parts IX-1 = 1.5 parts — C1 = 0.35 part 100° C./130° C. Composition 1 Comparative A2 = 10 parts IX-2 = 1.5 parts — C1 = 0.35 part 100° C./130° C. Composition 2 Comparative A2 = 10 parts IX-3 = 1.5 parts — C1 = 0.35 part 100° C./130° C. Composition 3 Comparative A3 = 10 parts IX-1 = 1.5 parts — C1 = 0.35 part 100° C./130° C. Composition 4 Comparative A3 = 10 parts IX-2 = 1.5 parts — C1 = 0.35 part 100° C./130° C. Composition 5 Comparative A3 = 10 parts IX-3 = 1.5 parts — C1 = 0.35 part 100° C./130° C. Composition 6

<Resin>

[0889] A1 to A4: Resin A1 to Resin A4

<Salt (I)>

[0890] I-4: Salt represented by formula (I-4)

[0891] I-8: Salt represented by formula (I-8)

[0892] I-308: Salt represented by formula (I-308)

[0893] I-312: Salt represented by formula (I-312)

[0894] I-320: Salt represented by formula (I-320)

[0895] I-328: Salt represented by formula (I-328)

[0896] I-339: Salt represented by formula (I-339)

[0897] I-1232: Salt represented by formula (I-1232)

[0898] I-1270: Salt represented by formula (I-1270)

[0899] I-1612: Salt represented by formula (I-1612)

[0900] I-1650: Salt represented by formula (I-1650)

[0901] I-1992: Salt represented by formula (I-1992)

[0902] I-2182: Salt represented by formula represented by formula (I-2182)

<Acid Generator>

[0903] IX-1

[0904] IX-2

[0905] IX-3

##STR00289##

<Quencher (C)>

[0906] C1: synthesized by the method mentioned in JP 2011-39502 A

##STR00290##

<Solvent>

[0907]

TABLE-US-00003 Propylene glycol monomethyl ether acetate 400 parts Propylene glycol monomethyl ether 100 parts γ-Butyrolactone  5 parts
(Evaluation of Exposure of Resist Composition with Electron Beam)

[0908] Each 6 inch-diameter silicon wafer was treated with hexamethyldisilazane on a direct hot plate at 90° C. for 60 seconds. A resist composition was spin-coated on the silicon wafer in such a manner that the thickness of the composition layer became 0.04 μm. Then, the coated silicon wafer was prebaked on the direct hot plate at the temperature shown in the column “PB” of Table 2 for 60 seconds to form a composition layer. Using an electron-beam direct-write system (“ELS-F125 125 keV”, manufactured by ELIONIX INC.), contact hole patterns (hole pitch of 40 nm/hole diameter of 17 nm) were directly written on the composition layer formed on the wafer while changing the exposure dose stepwise after development.

[0909] After exposure, post-exposure baking was performed on the hot plate at the temperature shown in the column “PEB” of Table 2 for 60 seconds, followed by paddle development with an aqueous 2.38% by mass tetramethylammonium hydroxide solution for 60 seconds to obtain resist patterns.

[0910] In the resist pattern obtained after development, the exposure dose at which the diameter of holes formed became 17 nm was defined as effective sensitivity.

<Evaluation of CD Uniformity (CDU)>

[0911] In the effective sensitivity, the hole diameter of the pattern formed using a mask having a hole dimeter of 17 nm was determined by measuring 24 times per one hole and the average of the measured values was regarded as the average hole diameter. The standard deviation was determined under the conditions that the average diameter of 400 holes about the patterns formed using the mask having a hole dimeter of 17 nm in the same wafer was regarded to as population.

[0912] The results are shown in Table 3. The numerical value in the parenthesis represents the standard deviation (nm).

TABLE-US-00004 TABLE 3 Resist composition CDU Example 14 Composition 1 2.62 Example 15 Composition 2 2.65 Example 16 Composition 3 2.80 Example 17 Composition 4 2.73 Example 18 Composition 5 2.71 Example 19 Composition 6 2.59 Example 20 Composition 7 2.55 Example 21 Composition 8 2.56 Example 22 Composition 9 2.64 Example 23 Composition 10 2.62 Example 24 Composition 11 2.69 Example 25 Composition 12 2.55 Example 26 Composition 13 2.68 Example 27 Composition 14 2.56 Comparative Example 1 Comparative Composition 1 2.89 Comparative Example 2 Comparative Composition 2 2.92 Comparative Example 3 Comparative Composition 3 3.06

[0913] As compared with Comparative Compositions 1 to 3, Compositions 1 to 14 exhibited small standard deviation and satisfactory evaluation of CD uniformity (CDU).

(Evaluation of Exposure of Resist Composition with Electron Beam, Organic Solvent Development)

[0914] Each 6 inch-diameter silicon wafer was treated with hexamethyldisilazane on a direct hot plate at 90° C. for 60 seconds. A resist composition was spin-coated on the silicon wafer in such a manner that the thickness of the composition layer became 0.04 μm. Then, the coated silicon wafer was prebaked on the direct hot plate at the temperature shown in the column “PB” of Table 2 for 60 seconds to form a composition layer. Using an electron-beam direct-write system (“ELS-F125 125 keV”, manufactured by ELIONIX INC.), contact hole patterns (hole pitch of 40 nm/hole diameter of 17 nm) were directly written on the composition layer formed on the wafer while changing the exposure dose stepwise after development.

[0915] After exposure, post-exposure baking was performed on the hot plate at the temperature shown in the column “PEB” of Table 2 for 60 seconds, followed by development with butyl acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a developer at 23° C. for 20 seconds using the dynamic dispensing method to obtain resist patterns.

[0916] In the resist pattern obtained after development, the exposure dose at which the diameter of holes formed became 17 nm was defined as effective sensitivity.

<Evaluation of CD Uniformity (CDU)>

[0917] In the effective sensitivity, the hole diameter of the pattern formed using a mask having a hole dimeter of 17 nm was determined by measuring 24 times per one hole and the average of the measured values was regarded as the average hole diameter. The standard deviation was determined under the conditions that the average diameter of 400 holes about the patterns formed using the mask having a hole dimeter of 17 nm in the same wafer was regarded to as population.

[0918] The results are shown in Table 4. The numerical value in the parenthesis represents the standard deviation (nm).

TABLE-US-00005 TABLE 4 Resist composition CDU Example 28 Composition 15 2.55 Example 29 Composition 16 2.59 Example 30 Composition 17 2.75 Example 31 Composition 18 2.68 Example 32 Composition 19 2.63 Example 33 Composition 20 2.50 Example 34 Composition 21 2.45 Example 35 Composition 22 2.47 Example 36 Composition 23 2.56 Example 37 Composition 24 2.53 Example 38 Composition 25 2.64 Example 39 Composition 26 2.45 Example 40 Composition 27 2.62 Example 41 Composition 28 2.44 Comparative Example 4 Comparative Composition 4 2.90 Comparative Example 5 Comparative Composition 5 2.91 Comparative Example 6 Comparative Composition 6 3.12

[0919] As compared with Comparative Compositions 4 to 6, Compositions 15 to 28 exhibited small standard deviation and satisfactory evaluation of CD uniformity (CDU).

[0920] A resist composition including a salt of the present invention is capable of obtaining a resist pattern with satisfactory CD uniformity (CDU), and is therefore suited for fine processing of semiconductors and is industrially very useful.