Radiation-sensitive composition, pattern forming method, and onium salt

Abstract

The invention provides a radiation-sensitive composition, a pattern forming method and an onium salt. The radiation-sensitive composition can exhibit excellent sensitivity, CDU performance, DOF performance, pattern circularity, LWR performance, pattern rectangularity and development defect inhibition performance during pattern formation. A radiation-sensitive composition contains an onium salt represented by formula (1) (hereinafter also referred to as "onium salt (1)"), a polymer containing a structural unit (I) having an acid-dissociable group, and a solvent. (In formula (1), Ar1 represents a (a1 + b1 + 1)-valent aromatic ring; ar2 is a (a2 + b2 + 1)-valent aromatic ring; each of X1 and X2 independently represents a monovalent organic group having 1-20 carbon atoms, a cyano group, a nitro group or a halogen atom; when there are a plurality of X1 and X2, the plurality of X1 and X2 may be the same as or different from each other. Y1 represents a monovalent organic group having 4 to 20 carbon atoms or a monovalent perfluoroalkyl group having 1 to 20 carbon atoms, which is bonded to Ar1 via-O-,-S-or-SO2-; when a plurality of Y1 exist, the plurality of Y1 are the same as or different from each other; y2 is a monovalent organic group having 4 to 20 carbon atoms or a monovalent perfluoroalkyl group having 1 to 20 carbon atoms, which is bonded to Ar2 via-O-,-S-or-SO2-; if a plurality of Y2 are present, the plurality of Y2 are the same as or different from each other; l represents a single bond or a divalent linking group having 1-5 carbon atoms; a1, a2, b1 and b2 are each independently an integer of 0-5; in the case where the aromatic ring of Ar2 is a benzene ring, b1 + b2 > = 1)

Description

Technical Field

[0001] This invention relates to a radiosensitive linear composition, a patterning method, and an onium salt. Background Technology

[0002] Photolithography, which uses a resist composition, is used in the formation of fine circuits in semiconductor devices. A representative process involves, for example, generating an acid by exposing a resist composition film to a dielectric mask pattern and irradiating it with radiation. The acid is then used as a catalyst to create a difference in the solubility of the polymer in an alkaline or organic developer between the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

[0003] In the aforementioned photolithography technology, short-wavelength radiation such as ArF excimer lasers, or liquid immersion lithography (LIB), which involves exposure in a liquid medium filling the space between the lens and the resist film of the exposure apparatus, is used to advance pattern miniaturization. As a next-generation technology, photolithography using even shorter wavelength radiation such as electron beams, X-rays, and extreme ultraviolet (EUV) is also under investigation.

[0004] In efforts to advance further technological progress, the following technology has been proposed: a quenching agent (acid diffusion control agent) is formulated into the resist composition to capture acid that diffuses to the unexposed area through a salt exchange reaction, thereby improving the photolithography performance (Japanese Patent No. 5706778).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 5706778 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, it has been determined that the technique described results in increased roughness or development defects in the resist pattern after development.

[0010] Therefore, in efforts toward next-generation technologies, resist compositions are required to possess properties equivalent to or better than those of existing resists in terms of sensitivity or critical dimension uniformity (CDU) performance (as an indicator of linewidth or aperture uniformity), depth of focus (DOF) performance, pattern circularity (indicating the roundness of aperture shape), line width roughness (LWR) performance (indicating the deviation of the linewidth of the resist pattern), pattern rectangularity (indicating the rectangularity of the cross-sectional shape of the resist pattern), and development defect suppression.

[0011] The purpose of this invention is to provide a radiometric linear composition, a patterning method, and an onium salt that exhibits excellent sensitivity, CDU performance, DOF performance, pattern circularity, LWR performance, pattern rectangularity, and development defect suppression during pattern formation.

[0012] Technical means to solve the problem

[0013] The inventors have made repeated efforts to solve this problem and have found that the objective can be achieved by adopting the following structure, thus completing the present invention.

[0014] That is, in one embodiment of the present invention, therein relates to a radioactive linear composition comprising:

[0015] The onium salt represented by the following formula (1) (hereinafter also referred to as "onium salt (1)")

[0016] Polymers containing structural units (I) with acid-dissociable groups, and

[0017] Solvent.

[0018] [Chemistry 1]

[0019]

[0020] (In formula (1),

[0021] Ar 1 It is an aromatic ring with a valence of (a1+b1+1);

[0022] Ar 2 It is an aromatic ring with a valence of (a² + b² + 1).

[0023] X 1 and X 2 Each is independently a monovalent organic group, cyano group, nitro group, or halogen atom having 1 to 20 carbon atoms; in X 1 and X 2 When multiple X exist, multiple X 1 and X2 They are either the same as or different from each other;

[0024] Y 1 For use with Ar via -O-, -S- or -SO2- 1 The bond consists of a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms; in Y 1 In the case of multiple Ys, multiple Ys 1 They are the same or different;

[0025] Y 2 For use with Ar via -O-, -S- or -SO2- 2 The bond consists of a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms; in Y 2 In the case of multiple Ys, multiple Ys 2 They are the same or different;

[0026] L is a single bond or a divalent linker with 1 to 5 carbon atoms;

[0027] a1, a2, b1, and b2 are each an independent integer from 0 to 5; where, in Ar 2 (When the aromatic ring is a benzene ring, b1 + b2 ≥ 1.)

[0028] The radiosensitive linear composition contains an onium salt (1) as a quencher (acid diffusion control agent), thus exhibiting excellent resist properties such as sensitivity or CDU performance, DOF performance, pattern circularity, LWR performance, pattern rectangularity, and development defect suppression during pattern formation. The reason for this is not bound by any theory, but is speculated as follows. The inventors considered that the problem arose from the low solubility of the quencher in the solvent. That is, they speculated that in a quencher with a highly polar intramolecular salt (zwitterionic) structure, the overall polarity of the structure is also increased, resulting in reduced solubility in the solvent and insufficient dissolution in the organic solvent during development, thereby causing development defects or increased roughness. In the onium salt (1), by introducing a structure with relatively high hydrophobicity, the overall solubility of the molecule in the solvent or developer can be improved. Furthermore, by employing a carboxylate salt, it becomes strongly alkaline, thus providing excellent quencher function. It is speculated that through these synergistic effects, the radiosensitive linear composition can exert the properties of the resist at a high level.

[0029] In this specification, the term "organic group" refers to a group containing at least one carbon atom. This excludes groups that, as organic groups, are functional groups or characteristic groups (cyano, carboxyl, carbonyl, etc.) on their own.

[0030] In another embodiment, the present invention relates to a pattern forming method, comprising:

[0031] The process of directly or indirectly coating the radiosensitive linear composition onto a substrate to form a resist film;

[0032] The process of exposing the resist film; and

[0033] The process of developing the exposed resist film using a developing solution.

[0034] In the pattern forming method, since the sensible linear composition that exhibits excellent sensitivity or CDU performance, DOF performance, pattern circularity, LWR performance, pattern rectangularity, and development defect suppression during pattern forming is used, high-quality resist patterns can be formed with good yield.

[0035] In another embodiment of the invention, therein is a ium salt represented by the following formula (1).

[0036] [Chemistry 2]

[0037]

[0038] (In formula (1),

[0039] Ar 1 It is an aromatic ring with a valence of (a1+b1+1);

[0040] Ar 2 It is an aromatic ring with a valence of (a² + b² + 1).

[0041] X 1 and X 2 Each is independently a monovalent organic group, cyano group, nitro group, or halogen atom having 1 to 20 carbon atoms; in X 1 and X 2 When multiple X exist, multiple X 1 and X 2 They are either the same as or different from each other;

[0042] Y 1 For use with Ar via -O-, -S- or -SO2- 1 The bond consists of a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms; in Y 1 In the case of multiple Ys, multiple Ys 1 They are the same or different;

[0043] Y 2 For use with Ar via -O-, -S- or -SO2- 2 The bond consists of a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms; in Y 2 In the case of multiple Ys, multiple Ys 2They are the same or different;

[0044] L is a single bond or a divalent linker with 1 to 5 carbon atoms;

[0045] a1, a2, b1, and b2 are each an independent integer from 0 to 5; where, in Ar 2 (When the aromatic ring is a benzene ring, b1 + b2 ≥ 1.)

[0046] The onium salt (1) has good solubility in solvents or developers and can exert strong alkalinity in the resist film, thus it is preferred for radiosensitive linear compositions that require high levels of resist properties, primarily suppressing development defects. Detailed Implementation

[0047] The embodiments of the present invention will now be described in detail, but the present invention is not limited to these embodiments. Furthermore, combinations of preferred embodiments are also preferred.

[0048] <Radiosensitive Linear Composition>

[0049] The radiosensitive linear composition of this embodiment (hereinafter also simply referred to as the "composition") comprises an onium salt (1), a polymer, and a solvent. A radiosensitive linear acid generator may also be included if necessary. The composition may also contain any other arbitrary components without compromising the effects of the invention.

[0050] (Onium salt (1))

[0051] The onium salt (1) can function as a quencher for capturing acids in the unexposed or pre-exposed portions (also known as a "photodegradable alkali" or "acid diffusion control agent"). The onium salt (1) is represented by the formula (1).

[0052] As Ar 1 and Ar 2 The aromatic ring referred to is not particularly limited as long as it has an aromatic ring structure. Examples of aromatic rings include: aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, fennel ring, pyrene ring, fluorene ring, perylene ring, and cardamom ring; aromatic heterocycles such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring; or combinations thereof. Among these, benzene ring, naphthalene ring, and anthracene ring are preferred as aromatic rings, more preferably benzene ring and naphthalene ring, and even more preferably benzene ring. 1 Ar is a radical formed by removing (a1+b1+1) hydrogen atoms from the aromatic ring. 2 It is a radical formed by removing (a2+b2+1) hydrogen atoms from the aromatic ring.

[0053] The combination of ring structures is not limited to aromatic rings and is not particularly restricted. As a combination of ring structures, it can be any of the following: a condensed ring in which two adjacent rings share one side (two adjacent atoms); an aggregate ring in which two adjacent rings are bonded by a single bond; a spiro ring in which two adjacent rings share a carbon atom; or a bridged ring in which two adjacent rings share three or more consecutive atoms.

[0054] As X 1 and X 2 The monovalent organic group with 1 to 20 carbon atoms represented is not particularly limited, but may include: a monovalent hydrocarbon group with 1 to 20 carbon atoms; a group containing -CO-, -CS-, -O-, -S-, -SO2-, -NR'-, or a combination of two or more of these between carbon atoms or at the end of the hydrocarbon group (hereinafter also referred to as "base α"); a group formed by substituting a substituent for part or all of the hydrogen atoms contained in the hydrocarbon group or the base (α) (hereinafter also referred to as "base β"); or a combination of these. R' is a hydrogen atom or a monovalent hydrocarbon group with 1 to 10 carbon atoms. Wherein, X is... 1 and X 2 , with Y 1 and Y 2 Except for comparable structures.

[0055] Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms include: monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, or combinations thereof.

[0056] Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include straight-chain or branched saturated hydrocarbon groups having 1 to 20 carbon atoms, or straight-chain or branched unsaturated hydrocarbon groups having 1 to 20 carbon atoms.

[0057] Examples of monovalent alicyclic hydrocarbon groups with 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups are cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Preferred polycyclic cycloalkyl groups are bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclic decyl, and tetracyclic dodecyl. Preferred monocyclic unsaturated hydrocarbon groups are monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl. Preferred polycyclic unsaturated hydrocarbon groups are polycyclic cycloalkenyl groups such as norbornyl, tricyclic decenyl, and tetracyclic dodecenyl.

[0058] Examples of monovalent aromatic hydrocarbon groups with 6 to 20 carbon atoms include: aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthracene; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0059] The group (α) is preferably a heterocyclic group containing heteroatoms between the carbon-carbon atoms constituting the ring. Examples of heterocyclic groups include groups formed by removing a hydrogen atom from an aromatic heterocyclic structure, groups formed by removing a hydrogen atom from an aliphatic heterocyclic structure, and groups formed by combining these. Examples of heteroatoms include oxygen atoms, nitrogen atoms, and sulfur atoms.

[0060] Examples of aromatic heterocyclic structures include:

[0061] Aromatic heterocyclic structures containing oxygen atoms, such as furan, benzofuran, and dibenzofuran;

[0062] Aromatic heterocyclic structures containing nitrogen atoms, such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole;

[0063] Aromatic heterocyclic structures containing sulfur atoms, such as thiophene, benzothiophene, and dibenzothiophene;

[0064] Aromatic heterocyclic structures containing multiple heteroatoms, such as thiazoles, benzothiazoles, thiazides, and oxazines.

[0065] Examples of aliphatic heterocyclic structures include:

[0066] Aliphatic heterocyclic structures containing oxygen atoms, such as oxacyclopropane, tetrahydrofuran, tetrahydropyran, dioxacyclopentane, and dioxane;

[0067] Aliphatic heterocyclic structures containing nitrogen atoms, such as aziridine, pyrrolidine, piperidine, and piperazine;

[0068] Thietane, thietane, thiane, and other aliphatic heterocyclic structures containing sulfur atoms;

[0069] Aliphatic heterocyclic structures containing multiple heteroatoms, such as morpholine, 1,2-oxathionecyclopentane, and 1,3-oxathionecyclopentane.

[0070] Examples of aliphatic heterocyclic structures include lactone structures, cyclic carbonate structures, sulfonyl lactone structures, and structures containing cyclic acetals. Examples of such structures include those represented by formulas (H-1) to (H-11).

[0071] [Chemistry 3]

[0072]

[0073] In the formula, γ is an integer from 1 to 3.

[0074] Examples of substituents that replace some or all of the hydrogen atoms in the organic group include: halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups formed by replacing the hydrogen atoms of these groups with halogen atoms; and side oxygen groups (=O).

[0075] As X 1 and X 2 The halogen atoms represented can be listed as: fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.

[0076] As X 1 and X 2 Preferably, it is a monovalent hydrocarbon group with 1 to 10 carbon atoms, a group containing -O-, -CO-, or a combination thereof between carbon atoms or at the end of the hydrocarbon group, a group formed by substituting a hydrogen atom of the hydrocarbon group with a fluorine atom, or a halogen atom.

[0077] As Y 1 and Y 2 The monovalent organic group with 4 to 20 carbon atoms in it can preferably be X 1 and X 2 The groups represented are monovalent organic groups with carbon numbers 1 to 20, corresponding to those with carbon numbers 4 to 20. In the case of Y... 1 and Y 2 When the monovalent organic group with carbon number 4 to 20 is represented as y, Y 1 and Y 2 Each can be represented independently by the following formula.

[0078] [Chemistry 4]

[0079]

[0080] (In the formula, To be with Ar 1 Or Ar 2 (The bond structure.)

[0081] Y 1 Preferably via -O- and Ar 1 The bond consists of a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms, Y 2 Preferably via -O- and Ar 2 The bond consists of a monovalent organic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms.

[0082] Y 1 and Y 2The lower limit of the number of carbons in the monovalent organic group is preferably 5, more preferably 6, and even more preferably 7. The upper limit of the number of carbons is preferably 16, more preferably 12, and even more preferably 10. Thus, the onium salt (1) exhibits good solubility.

[0083] As Y 1 and Y 2 The monovalent perfluoroalkyl group represented by carbon number 1 to 20 can be either straight-chain or branched, for example: trifluoromethyl, perfluoroethyl, perfluoron-propyl, perfluoroisopropyl, perfluoron-butyl, perfluoroisobutyl, perfluorotert-butyl, perfluoron-pentyl, perfluoron-hexyl, etc.

[0084] As Y 1 and Y 2 The monovalent perfluoroalkyl group having 1 to 20 carbon atoms is preferably a monovalent perfluoroalkyl group having 1 to 10 carbon atoms, more preferably a monovalent straight-chain perfluoroalkyl group having 1 to 5 carbon atoms, and even more preferably a trifluoromethyl or perfluoroethyl group.

[0085] As a divalent linker with 1 to 5 carbon atoms represented by L, it is preferable to use X 1 and X 2 The group represented by the monovalent organic groups with carbon numbers of 1 to 20 is formed by removing one hydrogen atom from the group corresponding to carbon numbers of 1 to 5.

[0086] L is preferably a single bond or an alkyl dienyllium with 1 to 3 carbon atoms, more preferably a single bond, a methane dienyllium, or an ethane dienyllium, and even more preferably a single bond. Regarding the basicity of the onium salt (1), L is preferably bonded to I in the formula (1). + The adjacent positions of the bonded carbon atoms.

[0087] a1, a2, b1, and b2 are each preferably integers from 0 to 4, more preferably integers from 0 to 3, and even more preferably integers from 0 to 2.

[0088] In Ar 2 When the aromatic ring is a benzene ring, it is preferably 1≦b1+b2≦3, more preferably 1≦b1+b2≦2, and even more preferably b1+b2=1. Preferably, b1 is 0 and b2 satisfies the aforementioned range, more preferably b1 is 0 and b2 is 1.

[0089] The onium salt is preferably represented by the following formula (1-1), formula (1-2), or formula (1-3).

[0090] [Chemistry 5]

[0091]

[0092] (In equation (1-1), X) 1 X 2L, a1, a2, b1, and b2 have the same meaning as in equation (1); Y 11 and Y 21 Each is a monovalent organic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms, which is bonded to each aromatic ring of formula (1-1) via -O-, -S- or -SO2-; c1 is 0 or 1;

[0093] In equation (1-2), X 1 X 2 L, a1, and a2 have the same meaning as in equation (1); W 1 For alicyclic hydrocarbon structures, aromatic hydrocarbon structures, or aliphatic heterocyclic structures that form a condensation ring with the adjacent benzene ring of formula (1-2); Y 12 and Y 22 Each of the following is independently a monovalent organic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms bonded to each of the aromatic rings of formula (1-2) via -O-, -S- or -SO2-; b1 and b2 are independently integers from 0 to 5; c1 is 0 or 1;

[0094] In equation (1-3), L and X 1 X 2 a1 and a2 have the same meaning as in equation (1); Ar 23 It is an aromatic heterocycle; Y 13 Y is a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms that is bonded to an aromatic ring of formula (1-3) via -O-, -S-, or -SO2-; 23 For use with Ar via -O-, -S- or -SO2- 23 The bond consists of a monovalent organic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms; b1 and b2 are each an independent integer from 0 to 5; c1 is 0 or 1.

[0095] In the above equation (1-1), Y is used as... 11 and Y 21 The monovalent organic group with 4 to 20 carbon atoms that is bonded to each aromatic ring of formula (1-1) via -O-, -S-, or -SO2- can preferably be the Y group of formula (1). 1 The meaning represented by -O-, -S-, or -SO2- is related to Ar. 1 The bonded monovalent organic groups with 4 to 20 carbon atoms, and Y 2 The meaning represented by -O-, -S-, or -SO2- is related to Ar. 2 The bonded monovalent organic group has 4 to 20 carbon atoms. Similarly, regarding Y in formula (1-2) 12 and Y 22 The monovalent organic group represented and Y in formula (1-3)13 and Y 23 The monovalent organic group represented can also preferably be Y of formula (1). 1 The meaning represented by -O-, -S-, or -SO2- is related to Ar. 1 The bonded monovalent organic groups with 4 to 20 carbon atoms, and Y 2 The meaning represented by -O-, -S-, or -SO2- is related to Ar. 2 The bond consists of monovalent organic groups with 4 to 20 carbon atoms.

[0096] In the above equation (1-1), Y is used as... 11 and Y 21 The monovalent perfluoroalkyl group represented by carbon number 1 to 20 can preferably be Y of formula (1). 1 and Y 2 The terms represent monovalent perfluoroalkyl groups with 1 to 20 carbon atoms. Similarly, regarding Y in formulas (1-2)... 12 and Y 22 The monovalent perfluoroalkyl group represented and Y of formula (1-3) are also mentioned. 13 and Y 23 The monovalent perfluoroalkyl group represented can also preferably be Y of formula (1). 1 and Y 2 The term represents a monovalent perfluoroalkyl group.

[0097] In equations (1-1) to (1-3), c1 is preferably 0.

[0098] In the above equation (1-2), W is used as... 1 The alicyclic hydrocarbon structure, aromatic hydrocarbon structure, and aliphatic heterocyclic structure represented by the benzene ring adjacent to formula (1-2) forming a condensation ring can preferably be X of formula (1). 1 and X 2 The structure corresponding to the monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms in the formula (1), and X in the formula (1) 1 and X 2 The structures corresponding to the monovalent aromatic hydrocarbon groups with 6 to 20 carbon atoms in the formula (1) and X 1 and X 2 The aliphatic heterocyclic structure described in [the text]. Even if W 1 It has an alicyclic hydrocarbon structure or an aliphatic heterocyclic structure, and also exhibits aromaticity by combining with the adjacent benzene ring. Therefore, the benzene ring and W 1 The condensation ring is contained in Ar of formula (1) 2 In the aromatic ring. In W 1 In the case of an alicyclic hydrocarbon structure or an aliphatic heterocyclic structure, when dealing with W 1 When making observations, the carbon-carbon intercarbon bonds shared with the adjacent benzene ring are considered as single bonds.

[0099] In the above equation (1-2), W is used as... 1 The alicyclic hydrocarbon structure represented is preferably a cycloalkane structure with 3 to 10 carbon atoms, more preferably a cycloalkane structure with 4 to 7 carbon atoms, and even more preferably a cyclopentane structure or a cyclohexane structure.

[0100] In the above equation (1-2), W is used as... 1 The aromatic hydrocarbon structure represented is preferably an aromatic hydrocarbon structure with 6 to 12 carbon atoms, and more preferably a benzene ring structure.

[0101] In the above equation (1-2), W is used as... 1 The aliphatic heterocyclic structure represented is preferably an aliphatic heterocyclic structure containing oxygen atoms as ring constituent atoms, and more preferably a lactone structure, a cyclic acetal structure, or a cyclic ether structure.

[0102] In equations (1-2) to (1-3), b1 and b2 are preferably integers from 0 to 3, more preferably integers from 0 to 2, and even more preferably 0 or 1.

[0103] In the aforementioned equation (1-3), Ar is used as... 23 The aromatic heterocycle represented can preferably be X of formula (1). 1 and X 2 The aromatic heterocyclic structure described in [the text]. Wherein, as Ar... 23 Preferably, it is a 5-membered ring aromatic heterocyclic structure or a ring structure formed by the condensation of a 5-membered ring aromatic heterocyclic structure and an aromatic hydrocarbon structure.

[0104] While there is no particular limitation on the specific examples of the onium salt (1) represented by the formula (1), for example, the structures represented by the formulas (C-1) to (C-72) below can be listed.

[0105] [Chemistry 6]

[0106]

[0107] [Chemistry 7]

[0108]

[0109] [Chemistry 8]

[0110]

[0111] [Chemistry 9]

[0112]

[0113] The lower limit of the content of onium salt (1) (total of such onium salts when multiple onium salts are used together) relative to 100 parts by mass of the polymer described later is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, further preferably 1 part by mass, and particularly preferably 3 parts by mass. The upper limit of the content is preferably 80 parts by mass, more preferably 60 parts by mass, further preferably 50 parts by mass, and particularly preferably 40 parts by mass. By setting the content of onium salt (1) within the aforementioned range, the properties of the resist can be utilized during resist pattern formation.

[0114] (Synthesis method of onium salt (1))

[0115] For example, onium salt (1) can be synthesized according to the following process. Furthermore, to simplify the process, in the above formula (1), let Ar... 1 and Ar 2 The explanation is based on the benzene ring, with a1, a2, and b1 being 0 and b2 being 1. An iodobenzoic acid analog providing the carboxylate anion of the onium salt (1) is used as a starting material, reacted with an oxidizing agent, followed by reaction with a specified substituent (Y in the process). 2 The target ononium salt (1a) can be synthesized by a nucleophilic reaction of benzene with a (weak) base, followed by treatment with a (weak) base. Other structures can also be synthesized by appropriately changing the starting materials or the reagents reacting with them.

[0116] [Chemistry 10]

[0117]

[0118] (In the process, L and Y) 2 This has the same meaning as equation (1) mentioned above.

[0119] (polymer)

[0120] The polymer is an aggregate of polymeric chains having structural units (I) containing acid-dissociable groups (hereinafter, the polymer will also be referred to as the "base polymer"). An "acid-dissociable group" refers to a group that substitutes for hydrogen atoms in carboxyl groups, phenolic hydroxyl groups, alcoholic hydroxyl groups, sulfonyl groups, etc., and that dissociates under the action of an acid. The radiosensitive linear composition exhibits excellent pattern-forming properties due to the presence of structural units (I) in the polymer.

[0121] The base polymer preferably has, in addition to structural unit (I), structural unit (II) which includes at least one of the group consisting of lactone, cyclic carbonate, sulfonyl lactone, and lactam structures, as described later. It may also have other structural units besides structural unit (I) and structural unit (II). Each structural unit will be described below.

[0122] [Structural Unit (I)]

[0123] The structural unit (I) is a structural unit having an acid-dissociable group. As for the structural unit (I), there is no particular limitation as long as it contains an acid-dissociable group. Examples include structural units having a tertiary alkyl ester moiety, structural units having a tertiary alkyl substituted hydrogen atom of a phenolic hydroxyl group, structural units having an acetal bond, etc. From the viewpoint of improving the pattern-forming property of the radiosensitive linear composition, the structural unit represented by the following formula (3) is preferred (hereinafter also referred to as "structural unit (I-1)").

[0124] [Chemistry 11]

[0125]

[0126] In the above formula (3), R 17 It can be a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 18 R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. 19 and R 20 Each is independently a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms, or a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or represents R. 19 and R 20 These are divalent alicyclic groups with 3 to 20 carbon atoms that combine with each other and together with the carbon atoms they are bonded to form. L 11 express -COO-、 -L 11a COO- or -COOL 11a COO-. L 11a It can be a substituted or unsubstituted alkyl or aryl group. To be with R 17 The bonds formed by the carbon atoms that are bonded.

[0127] As the R 17 From the viewpoint of providing copolymerization of the monolithic structural unit (I-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0128] As L 11a The alkyl dienes represented can include methylene, ethane dienes, 1,3-propane dienes, 2,2-propane dienes, and other alkyl dienes with 1 to 10 carbon atoms. As L... 11a Preferably, it is methylene or ethanediyl.

[0129] As L 11a The aryl diols represented can include divalent aromatic hydrocarbon groups with 6 to 20 carbon atoms, such as phenyldiol and naphthyldiol. As L... 11a Preferably, it is phenylenediol.

[0130] As L 11a The substituents that the aryl dimethyl group may have include: halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxy carbonyloxy group, acyl group, acyloxy group, alkoxy group, etc.

[0131] As the R 18 The monovalent hydrocarbon groups represented by carbon 1 to 20 can be exemplified by: monovalent chain hydrocarbon groups with carbon 1 to 10, monovalent alicyclic hydrocarbon groups with carbon 3 to 20, and monovalent aromatic hydrocarbon groups with carbon 6 to 20.

[0132] As the R 18 ~R 20 The monovalent chain hydrocarbon groups representing 1 to 10 carbon atoms can be listed as monovalent straight-chain or branched saturated hydrocarbon groups representing 1 to 10 carbon atoms, or monovalent straight-chain or branched unsaturated hydrocarbon groups representing 1 to 10 carbon atoms.

[0133] As the R 18 ~R 20 The monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms represented can preferably be X of formula (1). 1 and X 2 The monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms.

[0134] As the R 18 The monovalent aromatic hydrocarbon group representing 6 to 20 carbon atoms can preferably be X of formula (1). 1 and X 2 The monovalent aromatic hydrocarbon groups with 6 to 20 carbon atoms.

[0135] As the R 18 The monovalent hydrocarbon group representing 1 to 20 carbon atoms may have substituents, preferably X of formula (1). 1 and X 2 The substituents that a monovalent organic group representing 1 to 20 carbon atoms may have.

[0136] As the R 18 Preferably, it is a straight-chain or branched saturated hydrocarbon group with 1 to 10 carbon atoms, or an alicyclic hydrocarbon group with 3 to 20 carbon atoms.

[0137] The R 19 and R 20There is no particular limitation on the divalent alicyclic group with 3 to 20 carbon atoms that are combined with each other and formed together with the bonded carbon atoms, as long as it is formed by removing two hydrogen atoms from the same carbon atom of the carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon constituting the aforementioned number of carbon atoms. It can be any type of monocyclic or polycyclic hydrocarbon group. As a polycyclic hydrocarbon group, it can be any type of bridged alicyclic or condensed alicyclic hydrocarbon group, and it can also be any type of saturated or unsaturated hydrocarbon group. Furthermore, a condensed alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group formed by multiple alicyclic rings sharing a common edge (the bond between two adjacent carbon atoms).

[0138] As a monocyclic alicyclic hydrocarbon group, saturated hydrocarbon groups are preferably cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, cyclooctanediyl, etc., and as unsaturated hydrocarbon groups, preferably cyclopentenidyl, cyclohexenidyl, cycloheptenidyl, cyclooctenidyl, cyclodecenidyl, etc. As a polycyclic alicyclic hydrocarbon group, bridged alicyclic saturated hydrocarbon groups are preferred, for example, bicyclic [2.2.1]heptane-2,2-diyl (norbornene-2,2-diyl), bicyclic [2.2.2]octane-2,2-diyl, tricyclic [3.3.1.1]... 3,7 Decane-2,2-diyl (adamantane-2,2-diyl), etc.

[0139] Of these, R is preferred. 18 It is an alkyl group having 1 to 4 carbon atoms, R 19 and R 20 The alicyclic structure formed by the combination of these carbon atoms and their bonds is a polycyclic or monocyclic cycloalkane structure.

[0140] As the R 18 ~R 20 The substituents that may be present can preferably be L. 11a The aryl dimethyl group represented may have substituents.

[0141] As a structural unit (I-1), for example, the structural units represented by the following equations (3-1) to (3-15) (hereinafter also referred to as "structural unit (I-1-1) to structural unit (I-1-15)") can be listed.

[0142] [Chemistry 12]

[0143]

[0144] [Chemistry 13]

[0145]

[0146] In equations (3-1) to (3-15), R 17 ~R 20 This has the same meaning as equation (3) mentioned above. RL11 It can be a halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or alkoxy group. i and j are each independently an integer from 1 to 4. k and l are 0 or 1. 3a are each independently an integer from 0 to 3. When 3a is 2 or more, multiple R L11 They can be the same or different. a4 is an integer from 1 to 3.

[0147] For i and j, 1 is preferred. For R 18 Preferably, it is methyl, ethyl, isopropyl, tert-butyl, vinyl, phenyl, or iodophenyl. As R 19 and R 20 Preferably, it is methyl, ethyl, or isopropyl. As R... L11 Preferably, it contains iodine atoms, hydroxyl groups, or alkoxy groups. By using iodine atoms as R... L11 The iodine group can be preferably introduced into the structural unit (I).

[0148] Furthermore, the polymer may also contain structural units represented by the following formulas (1f) to (2f) as structural units (I).

[0149] [Chemistry 14]

[0150]

[0151] In equations (1f) to (2f), R αf Each can be independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R βf Each is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. h1 is an integer from 1 to 4.

[0152] As the R βf Preferably, it contains hydrogen atoms, methyl groups, or ethyl groups. As h1, it is preferably 1 or 2.

[0153] The base polymer may contain one or a combination of two or more structural units (I).

[0154] The lower limit of the content ratio (total content ratio in the case of multiple structural units) of structural unit (I) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, further preferably 20 mol%, and particularly preferably 25 mol%. Furthermore, the upper limit of the content ratio is preferably 80 mol%, more preferably 75 mol%, further preferably 70 mol%, and particularly preferably 65 mol%. By setting the content ratio of structural unit (I) within the aforementioned range, the pattern-forming property of the radiosensitive linear composition can be further improved.

[0155] [Structural Unit (II)]

[0156] Structural unit (II) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, sulfonyl lactone structures, and lactam structures. By also having structural unit (II), the solubility of the base polymer in the developer can be adjusted, resulting in improved photolithography properties such as resolution of the photosensitive linear composition. Furthermore, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0157] As a structural unit (II), for example, the structural units represented by the following formulas (T-1) to (T-11) can be listed.

[0158] [Chemistry 15]

[0159]

[0160] In the formula, R L1 It can be a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R L2 ~R L5 Each of the following is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. L4 and R L5 It can also be a divalent alicyclic group with 3 to 8 carbon atoms, formed by mutual bonding and together with the carbon atoms they are bonded to. 2 It can be a single bond or a divalent linker. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

[0161] As the R L4 and R L5 The 3-8 carbon-numbered divalent alicyclic groups that combine with each other and together with the carbon atoms they bond to form can be represented by R in the above formula (3). 19 and R 20 The carbon atoms in the alicyclic group are 3 to 8 carbon atoms, which are formed by the combination of the carbon atoms and the bonds between them. One or more hydrogen atoms on the alicyclic group may also be substituted with hydroxyl groups.

[0162] As the L 2 Examples of divalent linkages include: divalent linear or branched hydrocarbon groups having 1 to 10 carbon atoms, divalent alicyclic hydrocarbon groups having 4 to 12 carbon atoms, or groups consisting of one or more of these hydrocarbon groups and at least one of the groups selected from -CO-, -O-, -NH-, and -S-.

[0163] As structural unit (II), these are preferably structural units containing a lactone structure, more preferably structural units containing a norbornene lactone structure, and even more preferably structural units derived from norbornene lactone-based esters of (meth)acrylate.

[0164] The lower limit of the content of structural unit (II) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. Furthermore, the upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of structural unit (II) within the aforementioned range, the photosensitive linear composition can further improve lithographic properties such as resolution and the adhesion between the formed resist pattern and the substrate.

[0165] [Structural Unit (III)]

[0166] In addition to the structural units (I) and (II) described above, the base polymer may also optionally have other structural units. Examples of these other structural units include structural units (III) containing polar groups (excluding those equivalent to structural unit (II)). By also having structural unit (III), the base polymer can adjust its solubility in the developer, thereby improving the photolithographic properties, such as resolution, of the radiosensitive linear composition. Examples of these polar groups include hydroxyl, carboxyl, cyano, nitro, and sulfonamide groups. Among these, hydroxyl and carboxyl groups are preferred, and hydroxyl groups are more preferred.

[0167] As a structural unit (III), for example, structural units represented by the following formulas can be listed.

[0168] [Chemistry 16]

[0169]

[0170] In the formula, R A It can be a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0171] When the base polymer contains structural unit (III) having the polar group, the lower limit of the content ratio of the structural unit (III) relative to all structural units constituting the base polymer is preferably 1 mol%, more preferably 2 mol%, and even more preferably 4 mol%. Furthermore, the upper limit of the content ratio is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content ratio of the structural unit (III) within the aforementioned range, the lithographic properties, such as resolution, of the radiosensitive linear composition can be further improved.

[0172] [Structural Unit (IV)]

[0173] As other structural units, in addition to the structural unit (III) having the polar group, the base polymer optionally contains structural units having phenolic hydroxyl groups (hereinafter also referred to as "structural unit (IV)"). Structural unit (IV) contributes to improved etch resistance and increased difference in developer solubility (solution contrast) between exposed and unexposed areas. It is particularly suitable for pattern formation using exposure based on radiation with wavelengths below 50 nm, such as electron beams or EUV. In this case, the polymer preferably has both structural unit (IV) and structural unit (I).

[0174] Structural units with phenolic hydroxyl groups are represented, for example, by the following formulas (4-1) to (4-4).

[0175] [Chemistry 17]

[0176]

[0177] In equations (4-1) to (4-4), R 41 Each of the following can be independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Each of the following can be independently a halogen atom, a trifluoromethyl group, a cyano group, an alkyl or alkoxy group having 1 to 6 carbon atoms, or an acyl, acyloxy, or alkoxy carbonyl group having 2 to 7 carbon atoms. When multiple Qs exist, they may be identical or different from each other. t is an integer from 0 to 4.

[0178] When obtaining a structural unit (IV), it is preferable to polymerize while the phenolic hydroxyl groups of the monomeric compound are protected by a protecting group such as a base-dissociating group (e.g., an acyl group), followed by hydrolysis and deprotection to obtain the structural unit (IV). Polymerization can also be carried out without protecting the phenolic hydroxyl groups.

[0179] In the case of polymers used for exposure to radiation with wavelengths below 50 nm, the lower limit of the content of structural unit (IV) relative to all structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%. Furthermore, the upper limit of the content is preferably 70 mol%, more preferably 60 mol%.

[0180] [Other structural units]

[0181] The base polymer may also contain structural units with alicyclic structures as represented by the following formula (6) as structural units other than the listed structural units (hereinafter also referred to as "structural unit (VII)").

[0182] [Chemistry 18]

[0183]

[0184] (In the above formula (6), R)1α It can be a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group; R 2α (A monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms)

[0185] In equation (6), R is used as 2α The monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms represented can preferably be X of formula (1). 1 and X 2 The monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms.

[0186] When the base polymer contains the structural unit (VII), the lower limit of the content of the structural unit (VII) relative to all structural units constituting the base polymer is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. Furthermore, the upper limit of the content is preferably 20 mol%, more preferably 15 mol%, and even more preferably 12 mol%.

[0187] (Synthetic methods of basic polymers)

[0188] Basic polymers can be synthesized, for example, by using free radical polymerization initiators, to polymerize monomers that provide each structural unit in a suitable solvent.

[0189] Examples of free radical polymerization initiators include: azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylpentanonitrile), dimethyl 2,2'-azobisisobutyrate, and other azo-based free radical initiators; and peroxide-based free radical initiators such as benzoyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These free radical initiators can be used alone or in combination of two or more.

[0190] Examples of solvents used in the polymerization include:

[0191] Alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane;

[0192] Cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decahydronaphthalene, and norbornene;

[0193] Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene;

[0194] Halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene;

[0195] Saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate;

[0196] Diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and other polyol partial ether acetates are solvents;

[0197] Ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone;

[0198] Ethers such as tetrahydrofuran, dimethoxyethane, diethoxyethane, and 1,4-dioxane;

[0199] Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-methoxy-2-propanol, and 4-methyl-2-pentanol;

[0200] Lactones such as γ-butyrolactone. The solvents used in the polymerization of these substances can be a single solvent or in combination of two or more solvents.

[0201] The reaction temperature in the polymerization is typically 40°C to 150°C, preferably 50°C to 120°C. The reaction time is typically 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0202] The molecular weight of the base polymer is not particularly limited, but a lower limit of 2,000, more preferably 3,000, and even more preferably 4,000 is preferred as the lower limit of the equivalent weight average molecular weight (Mw) of polystyrene obtained by gel permeation chromatography (GPC). An upper limit of 30,000, more preferably 20,000, and even more preferably 15,000 is preferred as the upper limit of the Mw. By setting the Mw of the base polymer within the aforementioned range, good heat resistance or developability can be obtained in the obtained resist film.

[0203] The ratio (Mw / Mn) of the base polymer to the equivalent number average molecular weight (Mn) of polystyrene obtained based on GPC is typically 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0204] The Mw and Mn values ​​of the polymers in this specification are values ​​determined using gel permeation chromatography (GPC) under the following conditions.

[0205] GPC tubing: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh)

[0206] Column temperature: 40℃

[0207] Dissolution solvent: Tetrahydrofuran

[0208] Flow rate: 1.0 mL / min

[0209] Sample concentration: 1.0% by mass

[0210] Sample injection volume: 100 μL

[0211] Detector: Differential refractometer

[0212] Standard material: Monodisperse polystyrene

[0213] The proportion of the base polymer relative to the total solids content of the radiosensitive linear composition is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more.

[0214] (Other polymers)

[0215] The radiosensitive linear composition of this embodiment may also include a polymer with a higher fluorine atom mass content than the base polymer (hereinafter also referred to as a "high fluorine content polymer") as another polymer. When the radiosensitive linear composition contains a high fluorine content polymer, it may be more concentrated on the surface of the resist film relative to the base polymer. As a result, the water repellency of the resist film surface during immersion exposure can be improved, or the surface modification of the resist film or the control of the distribution of the intrafilm composition can be achieved during EUV exposure.

[0216] As a high-fluorine-content polymer, it is preferred to have, for example, the structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)"), and may also have structural unit (I) or structural unit (III) in the base polymer as needed.

[0217] [Chemistry 19]

[0218]

[0219] In equation (5), R 13 It can be a hydrogen atom, a methyl group, or a trifluoromethyl group. G L It consists of a single bond, an alkyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH-, -OCONH-, or a combination thereof. R 14 It is a monovalent fluorinated chain hydrocarbon group with 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group with 3 to 20 carbon atoms.

[0220] As the R 13 From the viewpoint of providing copolymerization of the monolithic structural unit (V), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0221] As the G L From the viewpoint of providing copolymerization of the monolithic structural unit (V), single bonds and -COO- are preferred, and -COO- is more preferred.

[0222] As the R 14 The monovalent fluorinated chain hydrocarbon group represented by carbon 1 to 20 can be exemplified by those formed by substituting some or all of the hydrogen atoms of a straight-chain or branched alkyl group having carbon 1 to 20 carbon atoms with fluorine atoms.

[0223] As the R 14 The monovalent fluorinated alicyclic hydrocarbon groups with 3 to 20 carbon atoms represented can be those formed by replacing some or all of the hydrogen atoms in monocyclic or polycyclic hydrocarbon groups with 3 to 20 carbon atoms with fluorine atoms.

[0224] As the R 14 Preferably, it is a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably 2,2,2-trifluoroethyl, 2,2,3,3,3-pentafluoropropyl, 1,1,1,3,3,3-hexafluoropropane-2-yl and 5,5,5-trifluoro-1,1-diethylpentyl.

[0225] When a high-fluorine polymer has structural units (V), the lower limit of the content of structural units (V) relative to all structural units constituting the high-fluorine polymer is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. Furthermore, the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of structural units (V) within the aforementioned range, the mass content of fluorine atoms in the high-fluorine polymer can be adjusted more appropriately, further promoting the biased presence on the surface of the resist film. As a result, the water repellency of the resist film during immersion exposure can be further improved.

[0226] High-fluorine polymers may also have fluorine-containing structural units (hereinafter also referred to as structural units (VI)) as represented by the following formula (f-2), either together with or in place of structural unit (V). By having structural units (f-2) in high-fluorine polymers, the solubility in alkaline developers can be improved, and the generation of development defects can be suppressed.

[0227] [Chemistry 20]

[0228]

[0229] Structural unit (VI) is broadly classified into two cases: one with a base-soluble group (x) and the other with a group (y) that dissociates under the action of a base and has increased solubility in alkaline developing solutions (hereinafter also referred to as "base-dissociative group"). Both (x) and (y) are common, and in equation (f-2), R... C It can be a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R D A single bond, a hydrocarbon group with a carbon number of 1 to 20 and a valence of (s+1), wherein the R of the hydrocarbon group E The terminal bonds on the side contain oxygen atoms, sulfur atoms, and -NR. dd A structure consisting of a carbonyl group, -COO-, -OCO-, or -CONH-, or a structure in which a portion of the hydrogen atom of the hydrocarbon group is substituted by an organic group having a heteroatom. dd It consists of a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

[0230] When structural unit (VI) has a base-soluble group (x), R F A is a hydrogen atom. 1 For oxygen atoms, -COO- or -SO2O- . Indicates the bond in R F The part. W 1 It is a single bond, a hydrocarbon group with 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. In A... 1 In the case of oxygen atoms, W 1 For in A 1 The bonded carbon atom has a fluorine atom or a fluorinated hydrocarbon group of fluorine alkyl group. R E It is a single bond or a divalent organogroup with 1 to 20 carbon atoms. When s is 2 or 3, multiple R... E W 1 A 1 and R F They can be the same or different. By having a (x) alkali-soluble group in the structural unit (VI), the affinity for alkaline developers can be improved, and development defects can be suppressed. As the structural unit (VI) having the (x) alkali-soluble group, A is particularly preferred. 1 It is an oxygen atom and W 1 The case is 1,1,1,3,3,3-hexafluoro-2,2-methanediyl.

[0231] When the structural unit (VI) has a (y) base-dissociable group, R F A is a monovalent organic group with 1 to 30 carbon atoms. 1 For oxygen atoms, -NR aa -、-COO- -OCO- or -SO2O- R aa It consists of hydrogen atoms or monovalent hydrocarbon groups with 1 to 10 carbon atoms. Indicates the bond in R F The part. W 1 It is a single bond or a divalent fluorinated hydrocarbon group with 1 to 20 carbon atoms. R E It is a single bond or a divalent organogroup with 1 to 20 carbon atoms. In A 1 -COO- -OCO- or -SO2O- In the case of W 1 or R F In relation to A 1 The bonded carbon atom or the adjacent carbon atom has a fluorine atom. In A 1 In the case of oxygen atoms, W 1 R E For a single bond, R D R is a hydrocarbon group with 1 to 20 carbon atoms. E The structure formed by the terminal bond of a carbonyl group on the side, R F It is an organic group containing fluorine atoms. When s is 2 or 3, multiple R... E W 1 A 1 and R F They can be the same or different. By having a (y) alkali-dissociating group in the structural unit (VI), the surface of the resist film changes from hydrophobic to hydrophilic during the alkaline developing process. As a result, the affinity for the developer can be significantly improved, and developing defects can be suppressed more effectively. As the structural unit (VI) having the (y) alkali-dissociating group, A is particularly preferred. 1 -COO- And R F or W 1 Or both of these contain fluorine atoms.

[0232] As R C From the viewpoint of providing copolymerization of the monolithic structural unit (VI), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0233] When a high-fluorine polymer has a structural unit (VI), the lower limit of the content ratio of the structural unit (VI) relative to all structural units constituting the high-fluorine polymer is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%. Furthermore, the upper limit of the content ratio is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content ratio of the structural unit (VI) within the aforementioned range, the water repellency of the resist film during immersion exposure can be further improved, and the generation of development defects can be suppressed.

[0234] [Other structural units]

[0235] High-fluorine polymers may also contain structural units with alicyclic structures as represented by formula (6) as structural units other than those listed above.

[0236] When the high-fluorine polymer contains the aforementioned alicyclic structural unit, the proportion of the alicyclic structural unit relative to all structural units constituting the high-fluorine polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. Furthermore, the upper limit of this proportion is preferably 60 mol%, more preferably 50 mol%, and even more preferably 45 mol%.

[0237] The lower limit of Mw for the high-fluorine content polymer is preferably 3,000, more preferably 5,000, and even more preferably 7,000. Furthermore, the upper limit of Mw is preferably 30,000, more preferably 20,000, and even more preferably 12,000.

[0238] The lower limit of the Mw / Mn ratio for high-fluorine polymers is typically 1, more preferably 1.1. Furthermore, the upper limit of the Mw / Mn ratio is typically 5, preferably 3, and more preferably 2.

[0239] When the radiosensitive linear composition contains a high-fluorine polymer, the lower limit of the content of the high-fluorine polymer relative to 100 parts by weight of the base polymer is preferably 0.5 parts by weight, more preferably 1 part by weight, and even more preferably 2 parts by weight. Furthermore, the upper limit of this content is preferably 15 parts by weight, more preferably 10 parts by weight, and even more preferably 8 parts by weight.

[0240] By setting the content of the high-fluorine polymer within the aforementioned range, the high-fluorine polymer can be more effectively biased towards the surface of the resist film. As a result, the water repellency of the resist film surface during immersion exposure can be further improved, or the surface modification of the resist film or the control of the distribution of the film composition during EUV exposure can be achieved. The radiosensitive linear composition may contain one or more high-fluorine polymers.

[0241] (Synthesis methods of high fluorine content polymers)

[0242] High-fluorine polymers can be synthesized using the same methods as the base polymers.

[0243] (Radiosensitive linear acid generator)

[0244] The radiosensitive linear composition of this embodiment preferably further comprises a radiosensitive linear acid generator, which generates an acid with a lower pKa than the acid generated by the onium salt (1) upon irradiation (exposure) with radiation, i.e., a relatively strong acid. The acid generated by the radiosensitive linear acid generator upon exposure can dissociate the acid-dissociating groups of the polymer's structural unit (I), thereby generating carboxyl groups, etc. This function differs from that of the onium salt (1), which, under the patterning conditions of the radiosensitive linear composition, substantially does not dissociate the acid-dissociating groups of the polymer's structural unit (I), etc., and suppresses the diffusion of the acid generated by the radiosensitive linear acid generator in the unexposed areas. The difference in function between the onium salt (1) and the radiosensitive linear acid generator is determined by the energy required for the dissociation of the acid-dissociating groups of the polymer's structural unit (I), etc., and the acidity of the acid generated by the radiosensitive linear acid generator, etc. The form in which the radiosensitive linear acid generator is contained in the radiosensitive linear composition may be either a form in which it exists alone as a compound (free from the polymer), or a form incorporated as part of the polymer, or both of these forms, but the form in which it exists alone as a compound is preferred.

[0245] By including the radiosensitive linear acid generator in the radiosensitive linear composition, the polarity of the polymer in the exposure section increases. The polymer in the exposure section becomes soluble relative to the developer when developed in an alkaline aqueous solution, but becomes insoluble relative to the developer when developed in an organic solvent.

[0246] Examples of radiosensitive linear acid generators include: onium salts (excluding the onium salt (1)), sulfonylimide compounds, halogen-containing compounds, diazonium ketone compounds, etc. Examples of onium salts include: sulfonium salts, tetrahydrothiophene onium salts, ferrophosphate salts, phosphonium salts, diazonium salts, pyridinium salts, etc. Among these, sulfonium salts and ferrophosphate salts are preferred.

[0247] Sulfonic acids can be listed as acids generated by exposure. Radiation-sensitive linear acid generators that produce such acids can be compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are substituted on the carbon atom adjacent to the sulfonyl group. Particularly preferred radiation-sensitive linear acid generators are those that, in addition to the structure of the sulfonyl group and the carbon atom adjacent to it, also have a cyclic structure, -O-, -CO-, or a combination of two or more of these structures. As for the cyclic structure, polycyclic aliphatic hydrocarbon structures and polycyclic aliphatic heterocyclic structures are preferred.

[0248] These radiosensitive linear acid generators can be used alone or in combination of two or more. The lower limit of the content of the radiosensitive linear acid generator (the total of these in the case of multiple radiosensitive linear acid generators) relative to 100 parts by weight of the base polymer is preferably 2 parts by weight, more preferably 4 parts by weight, and even more preferably 6 parts by weight. Furthermore, the upper limit of this content relative to 100 parts by weight of the base polymer is preferably 60 parts by weight, more preferably 50 parts by weight, and even more preferably 45 parts by weight. Thus, the excellent resist properties described above can be achieved during resist pattern formation.

[0249] (solvent)

[0250] The radiosensitive linear composition of this embodiment contains a solvent. The solvent is not particularly limited as long as it is a solvent that can at least dissolve or disperse the onium salt (1) and the polymer, and, if necessary, a radiosensitive linear acid generator.

[0251] Examples of solvents include: alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, and hydrocarbon solvents.

[0252] Examples of alcohol-based solvents include:

[0253] Monohydric alcohol solvents with 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol.

[0254] Polyol solvents with 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol.

[0255] Polyol partial ether solvents, etc., are formed by etherifying a portion of the hydroxyl groups in the polyol solvent.

[0256] In this embodiment, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol solvent.

[0257] Examples of ether-based solvents include:

[0258] Dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether;

[0259] Tetrahydrofuran, tetrahydropyran, and other cyclic ether solvents;

[0260] Ether solvents containing aromatic rings, such as diphenyl ether and anisole (methyl phenyl ether);

[0261] Polyol ether solvents, such as propylene glycol monomethyl ether, are formed by etherifying the hydroxyl groups of the aforementioned polyol solvents.

[0262] Examples of ketone solvents include: acetone, butanone, methyl isobutyl ketone, and other chain-like ketone solvents.

[0263] Cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone;

[0264] 2,4-Pentanedione, acetone-acetone, acetophenone, etc.

[0265] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolium ketone and N-methylpyrrolidone.

[0266] N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropionic acid, and other chain amide solvents.

[0267] Examples of ester-based solvents include:

[0268] Monocarboxylic acid ester solvents such as n-butyl acetate;

[0269] Diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and other polyol partial ether acetates are solvents;

[0270] Lactone solvents such as γ-butyrolactone and valproic acid;

[0271] Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate;

[0272] Solvents such as propylene glycol diacetate, methoxytriethylene glycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate are polycarboxylic acid diesters.

[0273] Examples of hydrocarbon solvents include:

[0274] Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane;

[0275] Aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-pentylnaphthalene.

[0276] Among these, alcohol-based solvents and ester-based solvents are preferred, more preferably polyol partial ether solvents, polyol partial ether acetate solvents, lactone solvents, and monocarboxylic acid ester solvents, and even more preferably propylene glycol monomethyl ether, ethyl lactate, propylene glycol monomethyl ether acetate, and γ-butyrolactone. The radiosensitive composition may contain one or more solvents.

[0277] (Any other ingredients)

[0278] The radiosensitive linear composition may contain any other components besides the aforementioned ingredients. Examples of such other components include: crosslinking agents, pre-existing growth promoters, surfactants, compounds containing alicyclic skeletons, sensitizers, etc. One or more of these other components may be used individually or in combination. The content of these other components is typically 5 parts by weight or less relative to 100 parts by weight of the polymer.

[0279] <Preparation Method of Radiosensitive Linear Composition>

[0280] The radiosensitive linear composition can be prepared, for example, by mixing an onium salt (1), a polymer and solvent, a radiosensitive linear acid generator as needed, and a high-fluorine polymer in a prescribed ratio. The radiosensitive linear composition is preferably filtered after mixing, for example, using a filter with a pore size of approximately 0.1 μm to 0.5 μm. The concentration of the solid component in the radiosensitive linear composition is typically 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0281] <Pattern Formation Method>

[0282] A pattern forming method according to one embodiment of the present invention includes:

[0283] Step (1) (hereinafter also referred to as "resist film formation step") involves directly or indirectly coating the photosensitive linear composition onto a substrate to form a resist film;

[0284] Step (2) (hereinafter also referred to as the "exposure step") involves exposing the resist film to light; and

[0285] Step (3) (hereinafter also referred to as the “development step”) involves developing the exposed resist film using a developing solution.

[0286] According to the pattern forming method, since the photosensitive linear composition with excellent resist properties is used, high-quality resist patterns can be formed with good yield. The following describes each step.

[0287] [Resist film formation process]

[0288] In this process (process (1)), a photoresist film is formed using the aforementioned photosensitive linear composition. Examples of substrates for forming the photoresist film include, for example, silicon wafers, silicon dioxide, aluminum-clad wafers, and other known materials. Alternatively, organic or inorganic antireflective films disclosed in, for example, Japanese Patent Application Publication No. 6-12452 or Japanese Patent Application Publication No. 59-93448 may be formed on the substrate. Examples of coating methods include, for example, spin coating, cast coating, and roll coating. Pre-baking (PB) may be performed after coating as needed to allow the solvent in the coating to evaporate. The PB temperature is typically 60°C to 150°C, preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The thickness of the formed resist film is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0289] In the case of immersion exposure, regardless of the presence or absence of water-repellent polymer additives such as the high-fluorine-content polymer in the radiosensitive linear composition, a liquid-immersion protective film that is insoluble in the liquid-immersion liquid may be provided on the formed resist film to avoid direct contact between the immersion liquid and the resist film. As the liquid-immersion protective film, either a solvent-removable protective film that is peeled off with a solvent before the developing process (e.g., see Japanese Patent Application Laid-Open No. 2006-227632) or a developer-removable protective film that is peeled off simultaneously with the developing process (e.g., see WO2005-069076 and WO2006-035790) may be used. From the viewpoint of yield, a developer-removable liquid-immersion protective film is preferred.

[0290] Furthermore, when using radiation with a wavelength of 50 nm or less for the exposure process as the next step, it is preferable to use a polymer having the aforementioned structural unit (I) and structural unit (IV) as the base polymer in the composition.

[0291] [Exposure Process]

[0292] In this step (step (2)), a photomask (which may be immersed in a liquid medium such as water) exposes the resist film formed in step (1), i.e., the resist film formation step, to radiation. The radiation used for exposure can be, for example, electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays, depending on the linewidth of the target pattern; or charged particle beams such as electron beams and alpha rays. Among these, far ultraviolet light, electron beams, and EUV are preferred, and ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and ArF excimer laser light or EUV are even more preferred.

[0293] When exposure is performed by immersion exposure, the immersion liquid used can be, for example, water or a fluorine-based inactive liquid. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a temperature coefficient of refractive index that is as small as possible to minimize distortion of the optical image projected onto the film. Especially when the exposure light source is an ArF excimer laser (wavelength 193 nm), water is preferred in terms of ease of acquisition and ease of operation. When using water, additives that reduce the surface tension of water and increase surface activity can be added in small proportions. These additives are preferably those that do not dissolve the resist film on the wafer and whose effect on the optical coating on the lower surface of the lens is negligible. Distilled water is preferred as the water used.

[0294] Preferably, a post-exposure bake (PEB) is performed after the initial exposure. In the exposed portions of the resist film, the acid generated by the radiosensitive linear acid generator during exposure promotes the dissociation of acid-dissociative groups in the polymer or the like. This PEB creates a difference in solubility of the developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0295] [Developing process]

[0296] In this step (step (3)), the resist film exposed in step (2), i.e., the exposure step, is developed using a developing solution. This forms the desired resist pattern. Generally, after development, the film is rinsed with a solution such as water or alcohol and then dried.

[0297] As a developing solution for the development process, in the case of alkaline development, examples include alkaline aqueous solutions containing at least one of the following alkaline compounds: sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyl diethylamine, ethyl dimethylamine, triethanolamine, tetramethyl ammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous solution of TMAH is preferred, and a 2.38% by mass aqueous solution of TMAH is more preferred.

[0298] In addition, when developing with an organic solvent, examples of organic solvents include hydrocarbon-based solvents, ether-based solvents, ester-based solvents, ketone-based solvents, alcohol-based solvents, and solvents containing organic solvents. Examples of such organic solvents include one or more solvents listed as solvents for the radiosensitive linear composition. Among these, ether-based solvents, ester-based solvents, and ketone-based solvents are preferred. As an ether-based solvent, glycol ether-based solvents are preferred, more preferably ethylene glycol monomethyl ether or propylene glycol monomethyl ether. As an ester-based solvent, acetate-based solvents are preferred, more preferably n-butyl acetate or amyl acetate. As a ketone-based solvent, chain ketones are preferred, more preferably 2-heptanone. The content of organic solvent in the developing solution is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, particularly preferably 99% by mass or more. Other components in the developing solution besides the organic solvent include, for example, water and silicone oil.

[0299] As mentioned above, the developer can be either an alkaline developer or an organic solvent developer.

[0300] Examples of development methods include: immersing a substrate in a tank filled with developer for a fixed time (immersion method); developing a substrate by using surface tension to accumulate developer on the substrate surface and then allowing it to stand still for a fixed time (puddle method); spraying developer onto the substrate surface (spraying method); and continuously spraying developer onto a substrate rotating at a fixed speed while scanning the developer nozzle at a fixed speed (dynamic distribution method), etc.

[0301] <Onium Salt (1)>

[0302] In another embodiment of the present invention, the onium salt is represented by the following formula (1).

[0303] [Chemistry 21]

[0304]

[0305] (In formula (1),

[0306] L is a single bond or a divalent linker with 1 to 5 carbon atoms;

[0307] Ar 1 It is an aromatic ring with a valence of (a1+b1+1);

[0308] Ar 2 It is an aromatic ring with a valence of (a² + b² + 1).

[0309] X 1 and X 2 Each is an independent monovalent organic group having 1 to 20 carbon atoms;

[0310] Y 1 For use with Ar via -O-, -S- or -SO2- 1 The bond consists of a monovalent organic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms;

[0311] Y 2 For use with Ar via -O-, -S- or -SO2- 2 The bond consists of a monovalent organic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms;

[0312] a1, a2, b1, and b2 are each an independent integer from 0 to 5; where, in Ar 2 When the aromatic ring is a benzene ring, b1+b2≧1)

[0313] As the onium salt represented by formula (1) in this embodiment, the onium salt (1) contained in the radiosensitive linear composition may preferably be used.

[0314] Example

[0315] The present invention will now be described in detail based on embodiments, but the present invention is not limited to these embodiments. Methods for determining various physical properties are shown below.

[0316] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)]

[0317] The Mw and Mn of the polymer were determined under the conditions described above. Furthermore, the dispersity (Mw / Mn) was calculated based on the results of the Mw and Mn measurements.

[0318] [ 13 C-NMR ( 13 C-Nuclear Magnetic Resonance, 13 [C-NMR analysis]

[0319] polymers 13C-NMR analysis was performed using a nuclear magnetic resonance apparatus (JNM-Delta400 of Nippon Electron Ltd).

[0320] <Polymer Synthesis>

[0321] The following shows the monomers used in the synthesis of each polymer in each embodiment and comparative example. Furthermore, in the following synthesis examples, unless otherwise specified, parts by mass refer to the value when the total mass of the monomers used is set to 100 parts by mass, and mol% refers to the value when the total number of moles of the monomers used is set to 100 mol%.

[0322] [Chemistry 22]

[0323]

[0324] [Synthesis example 1]

[0325] (Synthesis of polymer (A-1))

[0326] Monomers (M-1), (M-2), (M-5), (M-11), and (M-14) were dissolved in 200 parts by mass of 2-butanone in a molar ratio of 40 / 10 / 20 / 25 / 5 (mol%). Azobisisobutyronitrile (AIBN) (5 mol% relative to the total 100 mol% of the monomers used) was added as an initiator to prepare a monomer solution. 100 parts by mass of 2-butanone were placed in a reaction vessel, purged with nitrogen for 30 minutes, and the reaction vessel was set to 80°C. The monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was water-cooled to below 30°C. The cooled polymerization solution was then added to methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, then filtered again, and dried at 50°C for 24 hours to obtain a white powdery polymer (A-1) (yield: 80%). The polymer (A-1) had a Mw of 7,100 and an Mw / Mn ratio of 1.61. Additionally, 13 The results of C-NMR analysis showed that the proportions of each structural unit derived from (M-1), (M-2), (M-5), (M-11) and (M-14) were 40.1 mol%, 9.0 mol%, 20.9 mol%, 24.8 mol% and 5.2 mol%, respectively.

[0327] [Synthetic Examples 2-11 and Synthetic Examples 21-22]

[0328] (Synthesis of polymers (A-2) to (A-11) and (A-21) to (A-22))

[0329] Polymers (A-2) to (A-11), and polymers (A-21) to (A-22) were synthesized in the same manner as in Synthesis Example 1, except that the monomers shown in Table 1 below were used with the types and proportions indicated in Table 1. The content (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are shown in Table 1 below. In addition, "-" in Table 1 below indicates that the corresponding monomer was not used (the same applies to subsequent tables).

[0330] [Table 1]

[0331]

[0332] [Synthesis Example 12]

[0333] (Synthesis of polymer (A-12))

[0334] Monomers (M-1), (M-15), and (M-18) were dissolved in 200 parts by mass of 1-methoxy-2-propanol at a molar ratio of 40 / 10 / 50 (mol%), and AIBN (5 mol%) was added as an initiator to prepare a monomer solution. 100 parts by mass of 1-methoxy-2-propanol was placed in a reaction vessel, purged with nitrogen for 30 minutes, and the reaction vessel was set to 80°C. The monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was water-cooled to below 30°C. The cooled polymerization solution was added to 2,000 parts by mass of hexane, and the precipitated white powder was filtered and separated. The filtered white powder was washed twice with hexane, filtered again, and dissolved in 300 parts by mass of 1-methoxy-2-propanol. Subsequently, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After the reaction was completed, the residual solvent was removed by distillation, and the obtained solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to solidify the polymer. The obtained solid was separated by filtration and dried at 50°C for 13 hours to obtain a white powder polymer (A-12) (yield: 81%). The Mw of polymer (A-12) was 5,700, and the Mw / Mn ratio was 1.66. Additionally, 13The results of C-NMR analysis showed that the proportions of each structural unit derived from (M-1), (M-15), and (M-18) were 39.8 mol%, 10.1 mol%, and 50.1 mol%, respectively.

[0335] [Synthesis Examples 13 to 15]

[0336] (Synthesis of polymers (A-13) to (A-15))

[0337] Using the monomers of the types and proportions shown in Table 2 below, polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that... Furthermore, regarding the monomers providing structural units (IV), in the polymers, by... 13 C-NMR measurements confirmed the disappearance of the carbonyl peak of the acetyl group, indicating that all the base-dissociated groups were hydrolyzed to become phenolic hydroxyl groups. The content ratio (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymer are shown in Table 2 below.

[0338] [Table 2]

[0339]

[0340] [Synthesis Example 16]

[0341] (Synthesis of high-fluorine polymer (F-1))

[0342] Monomers (M-2), (M-4), (M-15), (M-16), (M-20), and (M-22) were dissolved in 200 parts by mass of 2-butanone in a molar ratio of 10 / 20 / 5 / 5 / 40 / 20 (mol%). AIBN (3 mol%) was added as an initiator to prepare a monomer solution. 100 parts by mass of 2-butanone was placed in a reaction vessel, purged with nitrogen for 30 minutes, and the reaction vessel was set to 80°C. The monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was water-cooled to below 30°C. After replacing the solvent with acetonitrile (400 parts by mass), hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was recovered. This process was repeated three times. A solution of the high-fluorine polymer (F-1) was obtained by replacing the solvent with propylene glycol monomethyl ether acetate (Yield: 75%). The high-fluorine polymer (F-1) had a Mw of 9,800 and an Mw / Mn ratio of 1.71. Additionally, 13The results of C-NMR analysis showed that the proportions of each structural unit derived from (M-2), (M-4), (M-15), (M-16), (M-20) and (M-22) were 8.7 mol%, 19.3 mol%, 5.4 mol%, 6.1 mol%, 40.9 mol% and 19.6 mol%, respectively.

[0343] [Synthesis Examples 17 to 20]

[0344] (Synthesis of high-fluorine polymers (F-2) to high-fluorine polymers (F-5))

[0345] Using the monomers of the types and proportions shown in Table 3 below, high-fluorine polymers (F-2) to (F-5) were synthesized in the same manner as in Synthesis Example 16. The content (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained high-fluorine polymers are shown in Table 3 below.

[0346] [Table 3]

[0347]

[0348] <Synthesis of [C]onium salt (1)>

[0349] [Example C1]

[0350] (Synthesis of onium salts (C-1))

[0351] The [C]onium salt (C-1) was synthesized as an acid diffusion control agent according to the following synthetic procedure.

[0352] [Chemistry 23]

[0353]

[0354] 20.0 mmol of 2-iodobenzoic acid, 20.0 mmol of m-chloroperbenzoic acid (m-CPBA), 25.0 mmol of sulfuric acid, and 50 g of dichloromethane were added to a reaction vessel and stirred for 1 hour under ice bath cooling. Then, 30.0 mmol of n-octyloxybenzene was added and stirred for 3 hours in an additional manner. Finally, 100 g of saturated sodium bicarbonate aqueous solution was added, and the mixture was stirred again at room temperature for 24 hours. The resulting reaction solution was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was dried with sodium sulfate, the solvent was removed by distillation, and the solution was purified by recrystallization, thereby obtaining the onium salt (C-1) represented by formula (C-1) in good yield.

[0355] [Examples C2-C37]

[0356] (Synthesis of onium salts (C-2) to (C-37))

[0357] With appropriate changes to the raw materials and precursors, the salt compounds represented by the following formulas (C-2) to (C-37) as acid diffusion control agents are synthesized in the same manner as in Example C1.

[0358] [Chemistry 24]

[0359]

[0360] [Chemistry 25]

[0361]

[0362] The following compounds are used as components other than those used in the synthesis.

[0363] [Acid diffusion control agents other than onium salts (C-1) to (C-37)]

[0364] cc-1 to cc-7: Compounds represented by formulas (cc-1) to (cc-7) below (hereinafter, the compounds represented by formulas (cc-1) to (cc-7) are sometimes referred to as "compound (cc-1)" to "compound (cc-7)" respectively).

[0365] [Chemistry 26]

[0366]

[0367] [B]Radiosensitive linear acid generator

[0368] B-1 to B-7: Compounds represented by the following formulas (B-1) to (B-9).

[0369] [Chemistry 27]

[0370]

[0371] [[E]solvent]

[0372] E-1: Propylene glycol monomethyl ether

[0373] E-2: Propylene glycol monomethyl ether

[0374] E-3: γ-Butyrolactone

[0375] E-4: Ethyl lactate

[0376] [Preparation of Negative-Sensitive Radiolinear Compositions for ArF Exposure]

[0377] [Example 1]

[0378] A mixture of 100 parts by mass of (A-1) as polymer [A], 8.0 parts by mass of (B-1) as radiosensitive linear acid generator [B], 6.0 parts by mass of (C-1) as ononium salt (1) as [C], 5.0 parts by mass of (F-1) as high fluorine content polymer [F] (solid component), and 3,400 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as solvent [E] was prepared by filtering the mixture using a membrane filter with a pore size of 0.2 μm.

[0379] [Examples 2-67, Examples 96-97, and Comparative Examples 1-7]

[0380] Using the types and amounts of each component shown in Table 4 below, except that, the radiosensitive linear compositions (J-2) to (J-67), (J-96) to (J-97), and (CJ-1) to (CJ-7) were prepared in the same manner as in Example 1.

[0381] [Table 4]

[0382]

[0383] <Formation of resist patterns using ArF exposure negative-type radiometric linear composition>

[0384] Using a spin coater (Tokyo Electron, Inc.'s "CLEAN TRACK ACT12"), a lower layer film forming composition (Brewer Science, Inc.'s "ARC66") was coated onto a 12-inch silicon wafer, followed by heating at 205°C for 60 seconds to form a lower layer film with an average thickness of 100 nm. The prepared ArF exposure negative-type radiosensitive linear composition was then coated onto the lower layer film using the same spin coater and pre-baked at 100°C for 60 seconds (PB). Afterward, it was cooled at 23°C for 30 seconds to form a resist film with an average thickness of 110 nm. Next, the resist film was exposed using an ArF excimer laser immersion exposure apparatus (ASML's "TWINSCAN XT-1900i") with optical conditions of numerical aperture (NA) = 1.35 and dipole (σ = 0.9 / 0.7), using a mask pattern with 40 nm apertures and 80 nm spacing. After exposure, it was baked (PEB) at 100°C for 60 seconds. Subsequently, the resist film was developed using n-butyl acetate as an organic solvent and dried, thereby forming a negative resist pattern (40 nm apertures, 80 nm spacing).

[0385] <Evaluation>

[0386] For the resist patterns formed using the aforementioned ArF exposure negative-type radiometric linear composition, the sensitivity, CDU performance, DOF performance, pattern circularity, and number of development defects were evaluated according to the following methods. The results are shown in Table 5 below. Furthermore, the length of the resist patterns was measured using a scanning electron microscope (Hitachi High-Technologies, Inc.'s "CG-5000").

[0387] [sensitivity]

[0388] In the formation of the resist pattern using the aforementioned ArF exposure negative-sensitive linear composition, the exposure amount for forming a pattern with 40 nm apertures and 80 nm spacing is set as the optimal exposure amount, and the optimal exposure amount is set as the sensitivity (mJ / cm). 2 Regarding sensitivity, 35 mJ / cm 2 The following conditions are rated as "good" and will exceed 35 mJ / cm 2 The situation was rated as "poor".

[0389] [CDU Performance]

[0390] For a resist pattern with 40 nm apertures and 80 nm spacing, a total of 1,800 measurements were taken from the top of the pattern using the aforementioned scanning electron microscope at arbitrary points. The dimensional deviation (3σ) was calculated and set as the CDU performance (nm). Regarding CDU performance, a smaller CDU value indicates a smaller and better aperture deviation over a long period. For CDU performance, values ​​below 3.0 nm were rated as "good," and values ​​above 3.0 nm were rated as "poor."

[0391] [DOF performance]

[0392] In the resist patterns analyzed at the optimal exposure determined in the sensitivity evaluation, the depth of focus (DOF) of the formed aperture patterns with diameters of 30 nm or more and 50 nm or less was measured. Regarding DOF performance, cases above 100 nm were evaluated as "good," and cases below 100 nm were evaluated as "poor."

[0393] [Circularity of the pattern]

[0394] For the contact holes with a 40 nm aperture and an 80 nm spacing formed by the optimal exposure amount determined in the sensitivity evaluation, the scanning electron microscope was used to observe them from top view, and the longitudinal and transverse dimensions were measured respectively. If the ratio of the longitudinal dimension to the transverse dimension is 0.95 or higher but less than 1.05, the evaluation is "A" (extremely good); if it is 0.90 or higher but less than 0.95, or 1.05 or higher but less than 1.10, the evaluation is "B" (good); if it is less than 0.90 or higher than 1.10, the evaluation is "C" (poor).

[0395] [Number of developmental defects]

[0396] A contact hole pattern with 40 nm holes and 80 nm spacing was formed by exposing the resist film at the optimal exposure level, and this pattern was designated as a defect inspection wafer. The number of defects on the defect inspection wafer was measured using a defect inspection apparatus (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were identified as originating from the resist film, and their number was calculated. Regarding the number of defects after development, if the number of defects identified as originating from the resist film was 50 or less, it was rated as "good"; if it was more than 50, it was rated as "bad".

[0397] [Table 5]

[0398]

[0399] Based on the results in Table 5, it is clear that the linear sensible compositions of Examples 1-67 and Examples 96-97 exhibited good sensitivity, CDU performance, DOF performance, pattern circularity, and number of development defects when used for ArF exposure. In contrast, the linear sensible compositions of Comparative Examples 1-7 showed poor sensitivity, CDU performance, DOF performance, pattern circularity, and number of development defects compared to the examples. Therefore, it can be said that when the linear sensible compositions of Examples 1-67 and Examples 96-97 are used for negative ArF exposure, they exhibit good CDU performance, DOF performance, and pattern circularity while maintaining high sensitivity, and also demonstrate excellent performance in suppressing development defects.

[0400] <Preparation of positive radiosensitive linear compositions for ArF exposure>

[0401] [Example 68]

[0402] A radiosensitive linear composition (J-68) was prepared by mixing 100 parts by mass of (A-1) as polymer [A], 10.0 parts by mass of (B-7) as radiosensitive linear acid generator [B], 8.0 parts by mass of (C-2) as ononium salt (1) as [C], 3.0 parts by mass of (F-2) as high fluorine content polymer [F] (solid component) and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as solvent [E] and filtering the mixture using a membrane filter with a pore size of 0.2 μm.

[0403] [Examples 69-81 and Comparative Examples 8-10]

[0404] Using the types and amounts of each component shown in Table 6 below, except that, the radiosensitive linear compositions (J-69) to (J-81) and the radiosensitive linear compositions (CJ-8) to (CJ-10) were prepared in the same manner as in Example 68.

[0405] [Table 6]

[0406]

[0407] <Formation of resist patterns using ArF exposure positive-type radiosensitive linear composition>

[0408] Using a spin coater (Tokyo Electron, Inc.'s "CLEAN TRACK ACT12"), a lower layer film forming composition (Brewer Science's "ARC66") was coated onto a 12-inch silicon wafer, followed by heating at 205°C for 60 seconds to form a lower layer film with an average thickness of 100 nm. Using the same spin coater, an ArF exposure positive-type radiosensitive linear composition prepared as described above was coated onto the lower layer film, followed by pre-baking (PB) at 100°C for 60 seconds. Afterward, it was cooled at 23°C for 30 seconds to form a resist film with an average thickness of 120 nm. Next, the resist film was exposed using an ArF excimer laser immersion exposure apparatus (ASML's "TWINSCAN XT-1900i") with optical conditions of NA=1.35 and dipole (σ=0.9 / 0.7), using a mask pattern that separated 60 nm lines and space. After exposure, the resist film was baked at 100°C for 60 seconds (PEB). Then, the resist film was developed using a 2.38% by mass TMAH aqueous solution as an alkaline developer. After development, the film was rinsed with water and then dried to form a positive resist pattern (60 nm line and spatial pattern).

[0409] <Evaluation>

[0410] For resist patterns formed using ArF exposure positive-type radiosensitive linear composition, sensitivity, LWR performance, and pattern rectangularity were evaluated according to the following method. The results are shown in Table 7 below. For the length measurement of the resist patterns, a scanning electron microscope (Hitachi High-Technologies, Inc.'s "CG-5000") was used.

[0411] [sensitivity]

[0412] In the formation of a resist pattern using a positive-type radiosensitive linear composition for ArF exposure, the exposure amount for forming a 60 nm line and spatial pattern is set as the optimal exposure amount, and the optimal exposure amount is set as the sensitivity (mJ / cm). 2 Regarding sensitivity, at 30 mJ / cm 2 The following conditions are rated as "good": exceeding 30 mJ / cm². 2 In such cases, the evaluation is "poor".

[0413] [LWR Performance]

[0414] The optimal exposure determined in the sensitivity evaluation was used to form a 60 nm line-space resist pattern. The formed resist pattern was observed from above using a scanning electron microscope. The linewidth deviation of a total of 500 points was measured, and a 3-sigma value was determined based on the distribution of the measured values. This 3-sigma value was set as LWR (nm). A smaller LWR value indicates lower and better line roughness. Regarding LWR performance, a value below 3.0 nm was rated as "good," and a value above 3.0 nm was rated as "poor."

[0415] [Pattern Rectangularity]

[0416] The 60 nm line-space resist pattern formed by the optimal exposure determined in the sensitivity evaluation is observed using the scanning electron microscope, and the cross-sectional shape of the line-space pattern is evaluated. Regarding the rectangularity of the resist pattern, if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape is greater than 1.00 and less than 1.05, it is rated "A" (extremely good); if it is greater than 1.05 and less than 1.10, it is rated "B" (good); and if it is greater than 1.10, it is rated "C" (poor).

[0417] [Table 7]

[0418]

[0419] Based on the results in Table 7, it is clear that the radiosensitive linear compositions of Examples 68 to 81 exhibit good sensitivity, LWR performance, and pattern rectangularity when used for positive resist patterning based on ArF exposure. In contrast, the radiosensitive linear compositions of Comparative Examples 8 to 10 show inferior properties compared to the examples.

[0420] <Preparation of Positive Radiosensitive Linear Compositions for Extreme Ultraviolet (EUV) Exposure>

[0421] [Example 82]

[0422] A radiosensitive linear composition (J-82) was prepared by mixing 100 parts by mass of (A-12) as polymer [A], 30.0 parts by mass of (B-3) as radiosensitive linear acid generator [B], 20.0 parts by mass of (C-3) as ononium salt (1) as [C], 6.0 parts by mass of (F-5) as high fluorine content polymer [F] (solid component) and 6,100 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-4) as solvent [E] and filtering the mixture using a membrane filter with a pore size of 0.2 μm.

[0423] [Examples 83-94 and Comparative Examples 11-13]

[0424] Using the types and amounts of each component shown in Table 8 below, except that, the radiosensitive linear compositions (J-83) to (J-94) and the radiosensitive linear compositions (CJ-11) to (CJ-13) were prepared in the same manner as in Example 83.

[0425] [Table 8]

[0426]

[0427] <Formation of resist patterns using positive-type radiosensitive linear compositions for EUV exposure>

[0428] Using a spin coater (Tokyo Electron, Inc.'s "CLEAN TRACK ACT12"), a lower layer film forming composition (Brewer Science's "ARC66") was applied onto a 12-inch silicon wafer, followed by heating at 205°C for 60 seconds to form a lower layer film with an average thickness of 105 nm. The prepared EUV exposure positive-type radiosensitive linear composition was then applied onto the lower layer film using the same spin coater and subjected to a photolithography (PB) at 130°C for 60 seconds. Afterward, the film was cooled at 23°C for 30 seconds, resulting in a resist film with an average thickness of 50 nm. Next, the resist film was exposed using an EUV exposure apparatus (ASML's "NXE3300") with NA=0.33, conventional illumination conditions (s=0.89), and an imecDEFECT32FFR02 mask. Following exposure, a photolithography (PEB) was performed at 120°C for 60 seconds. Subsequently, the resist film was developed using a 2.38% by mass TMAH aqueous solution as an alkaline developer. After development, the film was washed with water and then dried to form a positive resist pattern (25 nm line and space pattern).

[0429] <Evaluation>

[0430] For resist patterns formed using positive-type radiosensitive linear compositions for EUV exposure, sensitivity, LWR performance, and pattern rectangularity were evaluated according to the following method. The results are shown in Table 9 below. For the length measurement of the resist patterns, a scanning electron microscope (Hitachi High-Technologies, Inc.'s "CG-5000") was used.

[0431] [sensitivity]

[0432] In the formation of a resist pattern using a positive-type radiosensitive linear composition for EUV exposure, the exposure amount for forming a 25 nm line and spatial pattern is set as the optimal exposure amount, and the optimal exposure amount is set as the sensitivity (mJ / cm). 2 Regarding sensitivity, at 50 mJ / cm 2 The following conditions are rated as "good", while conditions exceeding 50 mJ / cm are rated as "poor".

[0433] [LWR Performance]

[0434] The optimal exposure, determined in the sensitivity evaluation, is used to adjust the mask size to form a 25 nm line-space pattern, thereby creating a resist pattern. The formed resist pattern is observed from above using a scanning electron microscope. The linewidth deviation of a total of 500 points is measured, and a 3-sigma value is determined based on the distribution of these measurements. This 3-sigma value is set as LWR (nm). A smaller LWR value indicates less line wobble and better performance. Regarding LWR performance, values ​​below 3.0 nm are rated as "good," and values ​​above 3.0 nm are rated as "poor."

[0435] [Pattern Rectangularity]

[0436] The 25 nm line-space resist pattern formed by the optimal exposure determined in the sensitivity evaluation is observed using the scanning electron microscope, and the cross-sectional shape of the line-space pattern is evaluated. Regarding the rectangularity of the resist pattern, if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape is greater than 1.00 and less than 1.05, it is rated "A" (extremely good); if it is greater than 1.05 and less than 1.10, it is rated "B" (good); and if it is greater than 1.10, it is rated "C" (poor).

[0437] [Table 9]

[0438]

[0439] Based on the results in Table 9, it is clear that the radiosensitive linear compositions of Examples 82 to 94 exhibit good sensitivity, LWR performance, and pattern rectangularity when used for resist patterning applications based on EUV exposure. In contrast, the radiosensitive linear compositions of Comparative Examples 11 to 13 show inferior properties compared to the examples.

[0440] <Preparation of negative-type radiosensitive linear compositions for EUV exposure, formation and evaluation of resist patterns using said compositions>

[0441] [Example 95]

[0442] A radiosensitive linear composition (J-95) was prepared by mixing 100 parts by mass of (A-15) as polymer [A], 40.0 parts by mass of (B-4) as radiosensitive linear acid generator [B], 35.0 parts by mass of (C-17) as onium salt (1) as [C], 3.0 parts by mass of (F-5) as high fluorine content polymer [F] (solid component) and 6,110 parts by mass (4,280 / 1,830 (parts by mass)) of a mixed solvent of (E-2) / (E-4) as solvent [E] and filtering the mixture using a membrane filter with a pore size of 0.2 μm.

[0443] Using a spin coater (Tokyo Electron, Inc.'s "CLEAN TRACK ACT12"), a lower layer film forming composition (Brewer Science's "ARC66") was applied onto a 12-inch silicon wafer, followed by heating at 205°C for 60 seconds to form a lower layer film with an average thickness of 105 nm. The prepared radiosensitive linear composition (J-95) was then applied onto the lower layer film using the same spin coater and subjected to a photolithography (PB) at 130°C for 60 seconds. Afterward, it was cooled at 23°C for 30 seconds, thereby forming a resist film with an average thickness of 45 nm. Next, the resist film was exposed using an EUV exposure apparatus (ASML's "NXE3300") with NA=0.33, conventional illumination conditions (s=0.89), and a mask: imecDEFECT32FFR15. Following exposure, a photolithography (PEB) was performed at 120°C for 60 seconds. Subsequently, butyl acetate was used as an organic solvent developer to develop the resist film and then dried, thereby forming a negative resist pattern (20 nm pores, 40 nm spacing).

[0444] For the resist pattern using the radiosensitive linear composition (J-95), the sensitivity and CDU performance were evaluated in the same manner as those for the resist pattern using the negative radiosensitive linear composition for ArF immersion exposure. As a result, the radiosensitive linear composition of Example 95 exhibited good sensitivity and CDU performance even when forming a negative resist pattern using EUV exposure.

[0445] Industrial availability

[0446] The described photosensitive linear composition, patterning method, and onium salt can be used to form resist patterns with good sensitivity to exposure light and excellent CDU performance, DOF performance, pattern circularity, LWR performance, pattern rectangularity, and development defect suppression. Therefore, these are preferably used in the fabrication processes of semiconductor devices that are expected to be further miniaturized in the future.

Claims

1. A radiosensitive linear composition comprising: The onium salt represented by the following formula (1), Polymers containing structural units (I) with acid-dissociable groups, and Solvent. [Chemistry 1] (In formula (1), Ar1 is a (a1+b1+1) valence aromatic ring. Ar2 is an aromatic ring with a valence of (a2+b2+1). X1 and X2 are each independently a monovalent organic group, cyano group, nitro group, or halogen atom with 1 to 20 carbon atoms. When multiple X1 and X2 exist, the multiple X1 and X2 may be the same or different from each other. Y1 is a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms that is bonded to Ar1 via -O-, -S-, or -SO2-. When multiple Y1s are present, they may be identical or different from each other. Y2 is a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms bonded to Ar2 via -O-, -S-, or -SO2-. When multiple Y2s are present, they may be identical or different from each other. L is a single bond or a divalent linker with 1 to 5 carbon atoms. a1, a2, b1, and b2 are each an independent integer from 0 to 5. When the aromatic ring of Ar2 is a benzene ring, b1+b2≧1).

2. The radiosensitive linear composition according to claim 1, wherein, The onium salt is represented by the following formula (1-1), formula (1-2), or formula (1-3). [Chemistry 2] In formula (1-1), L, X1, X2, a1, a2, b1, and b2 have the same meaning as in formula (1). Y11 and Y21 are, independently, monovalent organic groups with 4 to 20 carbon atoms or monovalent perfluoroalkyl groups with 1 to 20 carbon atoms that are bonded to the aromatic rings of formula (1-1) via -O-, -S-, or -SO2-. c1 is 0 or 1. In formula (1-2), L, X1, X2, a1, and a2 have the same meaning as in formula (1). W1 is an alicyclic hydrocarbon structure, aromatic hydrocarbon structure, or aliphatic heterocyclic structure that forms a condensation ring with the adjacent benzene ring of formula (1-2). Y12 and Y22 are, independently, monovalent organic groups with 4 to 20 carbon atoms or monovalent perfluoroalkyl groups with 1 to 20 carbon atoms that are bonded to the aromatic rings of formula (1-2) via -O-, -S-, or -SO2-. b1 and b2 are, independently, integers from 0 to 5. c1 is 0 or 1. In formulas (1-3), L, X1, X2, a1, and a2 have the same meaning as in formula (1). Ar23 is an aromatic heterocycle. Y13 is a monovalent organometallic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms bonded to the aromatic ring of formula (1-3) via -O-, -S-, or -SO2-. Y23 is a monovalent organometallic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms bonded to Ar23 via -O-, -S-, or -SO2-. b1 and b2 are each independently an integer from 0 to 5. c1 is 0 or 1.

3. The radiosensitive linear composition according to claim 1, wherein, Y1 is a monovalent organogroup with 4 to 20 carbon atoms bonded to Ar1 via -O- or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms. Y2 is a monovalent organic group with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms that is bonded to Ar2 via -O-.

4. The radiosensitive linear composition according to claim 1, wherein, Ar1 is a benzene ring.

5. The radiosensitive linear composition according to any one of claims 1 to 4, wherein, L is a single bond and is bonded to the adjacent position of the carbon atom bonded by I+ in the formula (1).

6. The radiosensitive linear composition according to any one of claims 1 to 4, wherein, The content of the onium salt is 0.1 parts by mass or more and 80 parts by mass or less relative to 100 parts by mass of the polymer.

7. The radiosensitive linear composition according to any one of claims 1 to 4, wherein, The structural unit (I) is represented by the following equation (3). [Chemistry 3] (In formula (3), R17 can be a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R18 is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. R19 and R20 are, independently, monovalent substituted or unsubstituted chain hydrocarbon groups having 1 to 10 carbon atoms or monovalent substituted or unsubstituted alicyclic hydrocarbon groups having 3 to 20 carbon atoms, or represent divalent alicyclic groups having 3 to 20 carbon atoms formed by the combination of R19 and R20 with the carbon atoms to which they are bonded. L11 indicates -COO-、 -L11aCOO- or -COOL11aCOO-. L11a is a substituted or unsubstituted alkyl or aryl group. (The bond between the carbon atom bonded to R17).

8. The radiosensitive linear composition according to any one of claims 1 to 4, wherein, The structural unit (I) accounts for more than 5 mol% and less than 80 mol% of all structural units constituting the polymer.

9. The radiosensitive linear composition according to any one of claims 1 to 4, wherein, The polymer further comprises a structural unit (II) containing at least one of the group consisting of lactone structures, cyclic carbonate structures and sulfonyl lactone structures.

10. The radiosensitive linear composition according to claim 9, wherein, The structural unit (II) accounts for more than 5 mol% and less than 80 mol% of all structural units constituting the polymer.

11. The radiosensitive linear composition according to any one of claims 1 to 4, further comprising a radiosensitive linear acid generator, said radiosensitive linear acid generator producing an acid with a lower pKa than the acid produced by said onium salt upon irradiation with radiation.

12. A method for forming a pattern, comprising: The process of directly or indirectly coating a substrate with the radiosensitive linear composition according to any one of claims 1 to 4 to form a resist film; The process of exposing the resist film; and The process of developing the exposed resist film using a developing solution.

13. The pattern forming method according to claim 12, wherein, The exposure is performed using an ArF excimer laser or extreme ultraviolet light.

14. An onium salt, represented by the following formula (1). [Chemistry 4] (In formula (1), Ar1 is a (a1+b1+1) valence aromatic ring. Ar2 is an aromatic ring with a valence of (a2+b2+1). X1 and X2 are each independently a monovalent organic group, cyano group, nitro group, or halogen atom with 1 to 20 carbon atoms. When multiple X1 and X2 exist, the multiple X1 and X2 may be the same or different from each other. Y1 is a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms that is bonded to Ar1 via -O-, -S-, or -SO2-. When multiple Y1s are present, they may be identical or different from each other. Y2 is a monovalent organogroup with 4 to 20 carbon atoms or a monovalent perfluoroalkyl group with 1 to 20 carbon atoms bonded to Ar2 via -O-, -S-, or -SO2-. When multiple Y2s are present, they may be identical or different from each other. L is a single bond or a divalent linker with 1 to 5 carbon atoms. a1, a2, b1, and b2 are each an independent integer from 0 to 5. When the aromatic ring of Ar2 is a benzene ring, b1+b2≧1).

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