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

Abstract

Provided are: a radiation-sensitive composition that can exhibit sensitivity, LWR, and a process window at sufficient levels, during formation of a resist pattern; a pattern forming method; an onium salt compound; and a polymer. The radiation-sensitive composition comprises: a polymer containing a structural unit (I) derived from an onium salt compound represented by formula (1); and a solvent. (In the formula, W is a cyclic structure configured together with two carbon atoms. The bond between carbon atoms, represented by the formula below, represents a single bond or a double bond.　A is a group represented by any of formula (A-1) to formula (A-7). (In the formulae, RA1 and RA2 are each a monovalent organic group having 1-20 carbon atoms). R1 is a monovalent organic group having 1-20 carbon atoms, a cyano group, a nitro group, a carboxy group, a hydroxy group, an amino group, a halogen atom, or a thiol group. Z+ is a monovalent radiation-sensitive onium cation. However, RA1, RA2, R1 or Z+ contains a polymerizable group).

Description

Radiation-sensitive compositions, pattern-forming methods, onium salt compounds, and polymers

[0001] The present invention relates to radiation-sensitive compositions, pattern-forming methods, onium salt compounds, and polymers.

[0002] Photolithography, which uses resist compositions, is employed to form fine circuits in semiconductor devices. A typical procedure involves, for example, generating acid by irradiating a resist composition film with radiation through a mask pattern. This acid then acts as a catalyst, creating a difference in the solubility of the polymer in alkaline or organic developers between the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

[0003] The above-mentioned photolithography techniques utilize short-wavelength radiation such as ArF excimer lasers, and further advance pattern miniaturization by employing liquid immersion lithography, a method in which exposure is performed with the space between the lens of the exposure apparatus and the resist film filled with a liquid medium. As next-generation technologies, lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered.

[0004] Regarding photoacid generators, which are the main components of resist compositions, perfluoroalkyl sulfonic acid, which can impart strong acid, is widely used to improve sensitivity and resolution. On the other hand, in recent years, due to growing environmental awareness, photoacid generators with reduced fluorine atom content are being investigated (see Japanese Patent Publication No. 7015295).

[0005] Patent No. 7015295

[0006] Even with photoacid generators that have reduced fluorine atom content, the resist performance in terms of sensitivity, LWR (Line Width Roughness), process window, etc., is required to be equivalent to or better than that of conventional products.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, an onium salt compound, and a polymer that can exhibit sufficient sensitivity, LWR, and process window during resist pattern formation.

[0008] As a result of intensive studies to solve this problem, the present inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention.

[0009] That is, in one embodiment, the present invention relates to a radiation-sensitive composition containing a polymer containing a structural unit (I) derived from an onium salt compound represented by the following formula (1) (hereinafter, also referred to as "onium salt compound (1)") and a solvent. (In formula (1), W is a cyclic structure having 3 to 40 ring members formed together with two carbon atoms in formula (1). The following formula between carbon-carbon represents a single bond or a double bond.) A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7) (hereinafter, these groups are also collectively referred to as "specific polar groups"). (In formula (A-3) and formula (A-4), R Ａ１ and R Ａ２ are each independently a monovalent organic group having 1 to 20 carbon atoms. * is a bond to a carbon atom.) R １ is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxy group, a hydroxy group, an amino group, a halogen atom, or a thiol group. When there are a plurality of R １ , the plurality of R １ are the same as or different from each other. m １ is an integer of 0 to 4. Z ＋ is a monovalent radiation-sensitive onium cation. However, the onium salt compound represented by formula (1) satisfies any one of the following requirements (1) to (4). Requirement (1): A is a group represented by the above formula (A-3), and R Ａ１ is a monovalent organic group having 2 to 20 carbon atoms containing a polymerizable group. Requirement (2): A is a group represented by the above formula (A-4), and R Ａ２ is a monovalent organic group having 2 to 20 carbon atoms containing a polymerizable group. Requirement (3): m １ is an integer of 1 to 4, and m １Individual R １ One of them is a monovalent organic group with 2 to 20 carbon atoms that contains a polymerizable group. Requirement (4): Z ＋ (This is a monovalent, radiation-sensitive onium cation containing a polymerizable group.)

[0010] The polymer of the radiation-sensitive composition contains structural unit (I) derived from the onium salt compound (1) as a radiation-sensitive acid-generating structure, and therefore exhibits excellent sensitivity, LWR, and process window during pattern formation. The reason for this is presumed to be as follows, although it is not bound by any theory.

[0011] In the onium salt compound (1), which is incorporated into the polymer as structural unit (I), a specific polar group containing a hydrogen atom is bonded to a carbon atom adjacent to the carbon atom to which the sulfonate anion is bonded. This stereochemistry creates a hydrogen bond between the sulfonate anion and the hydrogen atom of the specific polar group, stabilizing the anion. As a result, the strength of the generated acid increases, and the above-mentioned resist properties are exhibited. On the other hand, in conventional photoacid generators that position electron-withdrawing groups (including ester bonds) around the sulfonate anion, the sensitivity can be extremely low depending on their relative positions and the degree of freedom of the sulfonate anion. The onium salt compound (1) employs a strong oxidation mechanism that stabilizes the anion through hydrogen bonding between the sulfonate anion, which is bonded to the β-position carbon (ortho position if the cyclic structure is an aromatic ring) in the cyclic structure, and the specific polar group, rather than strong oxidation due to the arrangement of electron-withdrawing groups. This reduces the influence of electron-withdrawing groups and the degree of freedom of the sulfonate anion, and allows the sensitivity to be controlled within an appropriate range. Furthermore, since the onium salt structure, which acts as an acid-generating structure, is incorporated into the polymer, the diffusion length of the generated acid can be appropriately controlled, which is presumed to improve roughness. Note that an organic group is a group containing at least one carbon atom.

[0012] In another embodiment, the present invention relates to a pattern forming method comprising the steps of: applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

[0013] In this pattern formation method, since the above-mentioned radiation-sensitive composition, which has excellent sensitivity, LWR, and process window, is used during pattern formation, high-quality resist patterns can be formed with good yield.

[0014] In yet another embodiment, the present invention relates to an onium salt compound represented by the following formula (1). (In formula (1), W is a cyclic structure with 3 to 40 members, formed together with the two carbon atoms in formula (1). The following carbon-carbon expressions represent single or double bonds.) A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7). (In formulas (A-3) and (A-4), R Ａ１ and R Ａ２ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. * indicates a bond with a carbon atom. ) R １ R is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom, or a thiol group. １ If multiple R １ They are either identical or different from each other. １ Z is an integer between 0 and 4. ＋ A is a monovalent radiation-sensitive onium cation. However, the onium salt compound represented by the above formula (1) satisfies any one of the following requirements (1) to (4). Requirement (1): A is a group represented by the above formula (A-3), and R Ａ１ is a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group. Requirement (2): A is a group represented by the above formula (A-4), and R Ａ２ This is a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group. Requirement (3): m １ is an integer from 1 to 4, and m １ Individual R １One of them is a monovalent organic group with 2 to 20 carbon atoms that contains a polymerizable group. Requirement (4): Z ＋ (This is a monovalent, radiation-sensitive onium cation containing a polymerizable group.)

[0015] Because the onium salt compound has the specific structure described above, when applied to a polymer of a radiation-sensitive composition, it can exhibit excellent sensitivity, low wave ratio (LWR), and process window during pattern formation.

[0016] In a further embodiment, the present invention relates to a polymer comprising structural unit (I) derived from the above-mentioned onium salt compound.

[0017] Since the polymer contains structural unit (I) derived from the onium salt compound (1), when the polymer is applied to a radiation-sensitive composition, it can exhibit excellent sensitivity, LWR, and process window during pattern formation.

[0018] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. A preferred combination of embodiments is also preferable.

[0019] <Radiation-sensitive composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the composition") comprises a polymer and a solvent. It further comprises an acid diffusion control agent as needed. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

[0020] (Polymer) The polymer is an aggregate of polymerization chains containing structural unit (I) derived from the onium salt compound (1) (hereinafter, this polymer is also referred to as the "base polymer"). Preferably, the polymer contains structural unit (II) having an acid-dissociable group and structural unit (III) having a phenolic hydroxyl group, in addition to structural unit (I). The polymer may also contain other structural units other than structural units (I) to (III). Each structural unit will be described below.

[0021] [Structural Unit (I)] Structural unit (I) is a structural unit derived from the onium salt compound (1) represented by the above formula (1). The onium salt portion of structural unit (I), which includes an anion and a radiation-sensitive onium cation, functions as a radiation-sensitive acid-generating structure that generates acid upon irradiation (exposure) with radiation. If the onium salt compound (1) satisfies any of the above requirements (1) to (3), a so-called anion pendant structure is formed in structural unit (I), in which the anion of the onium salt compound (1) is bonded to the main chain of the polymer. If the onium salt compound (1) satisfies the above requirement (4), a so-called cation pendant structure is formed in structural unit (I), in which the radiation-sensitive onium cation of the onium salt compound (1) is bonded to the main chain of the polymer.

[0022] The cyclic structure with 3 to 40 members, formed with two carbon atoms represented by W, is not particularly limited, but preferred are alicyclic hydrocarbon structures with 3 to 20 carbon atoms, aromatic hydrocarbon structures with 6 to 20 carbon atoms, aliphatic heterocyclic structures with 3 to 20 carbon atoms, or aromatic heterocyclic structures with 3 to 20 carbon atoms. Alternatively, these cyclic structures may be combined. Examples of combinations include fused rings in which two adjacent rings share one edge (two adjacent interatomic bonds), ring aggregates in which two adjacent rings are joined by a single bond, and spiro rings in which two adjacent rings share one carbon atom. Fused rings are preferred as a combination.

[0023] As the above-mentioned alicyclic hydrocarbon structure having 3 to 20 carbon atoms, structures corresponding to monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms can be suitably adopted. Examples of the above-mentioned monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups include cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Preferred polycyclic cycloalkyl groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norborneyl, tricyclodecenyl, and tetracyclododecenyl groups. A bridged alicyclic hydrocarbon group is a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other are bonded together by a linking group containing one or more carbon atoms.

[0024] As the above-mentioned aromatic hydrocarbon structure having 6 to 20 carbon atoms, a structure corresponding to a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms can be suitably adopted. Examples of the above-mentioned monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthryl groups; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl groups.

[0025] Examples of the above-mentioned aliphatic heterocyclic structures having 3 to 20 carbon atoms include oxygen-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur-containing aliphatic heterocyclic structures such as thiethane, thiolane, and thian; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0026] Examples of the above aliphatic heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetals, and cyclic ketones. Such structures include, for example, those represented by the following formulas (H-1) to (H-13). Although all carbon-carbon bonds in the structural formulas shown below are saturated bonds, unsaturated bonds may be introduced as long as the valence allows.

[0027]

[0028] In the above formula, γ is an independent integer between 1 and 3.

[0029] Examples of the above-mentioned aromatic heterocyclic structures having 3 to 20 carbon atoms include: oxygen-containing aromatic heterocyclic structures such as furan, pyran, benzofuran, and benzopyran; nitrogen-containing aromatic heterocyclic structures such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole; sulfur-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple heteroatoms such as thiazole, benzothiazole, thiazine, and oxazine.

[0030] When the following carbon-carbon bond in W of formula (1) above represents a double bond, this double bond also includes the conjugated bond that occurs when a cyclic structure exhibits aromaticity.

[0031] Among these, the cyclic structure of W with 3 to 40 ring members is more preferably a polycyclic alicyclic hydrocarbon structure having 6 to 14 carbon atoms, an aromatic hydrocarbon structure having 6 to 12 carbon atoms, a monocyclic aliphatic unsaturated heterocyclic structure having 5 to 8 carbon atoms, or an aromatic heterocyclic structure having 5 to 8 carbon atoms, even more preferably an aromatic hydrocarbon structure having 6 to 10 carbon atoms, and particularly preferably a benzene ring.

[0032] In the above formulas (A-3) and (A-4), R Ａ１ and R Ａ２Examples of monovalent organic groups having 1 to 20 carbon atoms represented by include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups in which some or all of the hydrogen atoms of the hydrocarbon group are replaced with substituents (hereinafter also referred to as "group (α)"), groups containing a divalent heteroatom-containing linking group between carbon atoms or at the end of the hydrocarbon group or group (α) (hereinafter also referred to as "group (β)"), or combinations thereof. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0033] Examples of the above-mentioned 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.

[0034] Examples of the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms, or linear or branched unsaturated hydrocarbon groups having 1 to 20 carbon atoms.

[0035] As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms indicated in W above can be suitably adopted.

[0036] As the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms indicated in W above can be suitably adopted.

[0037] Examples of the above-mentioned divalent heteroatom-containing linking groups include -CO-, -CS-, -O-, -S-, and -SO ２ Examples include groups containing -, -NR'-, or combinations of two or more of these.

[0038] Examples of substituents that the above hydrocarbon group may have 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 in which the hydrogen atoms of these groups are substituted with halogen atoms; oxo groups (=O), etc.

[0039] In the above formulas (A-3) and (A-4), R Ａ１ and R Ａ２ Preferably, the group is a substituted or unsubstituted monovalent linear hydrocarbon group having 1 to 20 carbon atoms or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms; more preferably, a substituted or unsubstituted monovalent linear saturated hydrocarbon group having 1 to 10 carbon atoms or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms; even more preferably, a monovalent linear saturated hydrocarbon group having 1 to 5 carbon atoms or an unsubstituted phenyl group; and particularly preferably, a methyl group, an ethyl group, a phenyl group, an iodophenyl group, a diiodophenyl group, or a triiodophenyl group.

[0040] If the onium salt compound (1) satisfies requirement (1) or requirement (2) above, then R in formulas (A-3) and (A-4) above Ａ１ and R Ａ２ As a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group represented by R, Ａ１ and R Ａ２ A group obtained by incorporating a polymerizable group into the above-mentioned monovalent organic group having 1 to 20 carbon atoms can be suitably adopted. The group represented by formula (A-3) and the group represented by formula (A-4) are preferably the group represented by the following formulas (A-3-1) and (A-4-1), respectively.

[0041] (In formulas (A-3-1) and (A-4-1), R Ａ１１ and R Ａ２１ Each of these is independently a single bond, a divalent heteroatom-containing linking group, or a divalent organic group. G is a polymerizable group. R Ａ１１ The total number of carbon atoms in G, and R Ａ２１ The total number of carbon atoms in G is between 2 and 20, respectively.

[0042] In formulas (A-3-1) and (A-4-1) above, the polymerizable group represented by G is, for example, a group containing a carbon-carbon double bond. Typical structures include a structure containing an ethylenically unsaturated double bond, or a structure containing an ethylenically unsaturated double bond as a substructure constituting a ring. The polymerizable group may have substituents. Examples of structures containing an ethylenically unsaturated double bond include vinyl groups, vinyl ether groups, (meth)acryloyl groups, (meth)acryloyloxy groups, and (meth)acrylamide groups. Examples of structures containing an ethylenically unsaturated double bond as a substructure constituting a ring include norbornene, cyclopentadiene, and cyclohexene.

[0043] Examples of substituents when the polymerizable group has substituents include halogen atoms, monovalent organic groups having 1 to 20 carbon atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, oxo groups (=O), and the like.

[0044] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0045] As a monovalent organic group having 1 to 20 carbon atoms as the substituent, R in formula (A-3) above is Ａ１ A monovalent organic group having 1 to 20 carbon atoms, represented by [the formula shown], can be suitably used.

[0046] Specific examples of the polymerizable group mentioned above include, but are not limited to, structures represented by the following formula.

[0047] (In the formula, * represents R) Ａ１１ or R Ａ２１ (This is a bonding bond with the constituent atoms.)

[0048] R Ａ１１ and R Ａ２１ The divalent heteroatom-containing linking group represented by is R in the above formula (A-3). Ａ１ The divalent heteroatom-containing linking group shown above can be suitably adopted.

[0049] R Ａ１１ and R Ａ２１ The divalent organic group in is R in formula (A-3) above.Ａ１ Among the monovalent organic groups having 1 to 20 carbon atoms represented by [formula], groups obtained by removing one hydrogen atom from the group corresponding to 2 to 20 carbon atoms can be suitably adopted.

[0050] R Ａ１１ and R Ａ２１ Preferably, the linking group is a divalent heteroatom-containing linking group, a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or a combination thereof, or a single bond; more preferably, -CO-, -O-, -NH-, a substituted or unsubstituted benzenediyl group, a substituted or unsubstituted naphthalenediyl group, or a combination thereof, or a single bond. Ａ１１ and R Ａ２１ The substituents that it may have are R in formula (A-3) above. Ａ１ The substituents shown in can be suitably adopted. Among these, halogen atoms are preferred as substituents, and iodine atoms are more preferred.

[0051] R in formula (1) above １ As a monovalent organic group having 1 to 20 carbon atoms represented by the above formula (A-3), R Ａ１ A monovalent organic group having 1 to 20 carbon atoms, represented by [the formula shown], can be suitably used.

[0052] R in formula (1) above １ Examples of halogen atoms represented by include fluorine, chlorine, bromine, and iodine atoms. Preferably, chlorine, bromine, and iodine atoms are used as halogen atoms, with iodine atoms being more preferred.

[0053] m1 is preferably an integer between 0 and 3, and more preferably an integer between 0 and 2.

[0054] If the onium salt compound (1) satisfies the above requirement (3), m １ is an integer from 1 to 4, and m １ Individual R １ One of them is a monovalent organic group with 2 to 20 carbon atoms that contains a polymerizable group. １ If it is 1, then there is one R １ m is a monovalent organic group having 2 to 20 carbon atoms that contains polymerizable groups. １ If there are 2 or more, then there are 2 or more R１ One (or only) of these is a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group.

[0055] When the onium salt compound (1) satisfies the above requirement (3), R １ As a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group represented by , for example, R of formula (A-3) above when the onium salt compound (1) satisfies requirement (1) Ａ１ A monovalent organic group having 1 to 20 carbon atoms containing a polymerizable group represented by can be suitably used. In particular, R １ As a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group represented by the above formula (A-3-1), -R Ａ１１ -A group corresponding to G is preferred. In this case, R Ａ１１ Preferably, the linking group is a divalent heteroatom-containing linking group, a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or a combination thereof. ＊ , -OCO- ＊ , -CO-NH- ＊ , -NH-CO- ＊ A substituted or unsubstituted benzenediyl group, a substituted or unsubstituted naphthalenediyl group, or a combination thereof is more preferred. * represents a bond with a carbon atom constituting W. R １ The substituents that it may have are R in formula (A-3) above. Ａ１ The substituents shown in can be suitably adopted. Among these, halogen atoms are preferred as substituents, and iodine atoms are more preferred.

[0056] Specific examples of the anion of the onium salt compound (1) include, but are not limited to, the structures shown in the following formulas (1A-1) to (1A-42) and (1B-1) to (1B-8). The structures shown in the following formulas (1A-1) to (1A-34) relate to a mode in which the onium salt compound (1) is incorporated into structural unit (I) in an anion pendant form, and the structures shown in the following formulas (1B-1) to (1B-8) relate to a mode in which the onium salt compound (1) is incorporated into structural unit (I) in a cation pendant form.

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064] Z ＋ Examples of radiation-sensitive onium cations represented by include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0065] The above organic cation preferably has at least one selected from the group consisting of an iodine group, a fluoro group, and a trifluoromethyl group. By introducing these groups, the radiation absorption efficiency can be increased, thereby improving sensitivity.

[0066] If the onium salt compound (1) satisfies requirement (4), the sulfonium cation or iodonium cation as a monovalent radiation-sensitive onium cation containing a polymerizable group is preferably represented by the following formulas (X-1) to (X-6). ＋ If it does not contain polymerizable groups, then G-L in the following formula ｘ A structure excluding the corresponding structure can be suitably adopted.

[0067]

[0068] In the above formulas (X-1) to (X-6), G is independently a polymerizable group. Ｘ Each of these is independently a single bond, a divalent heteroatom-containing linking group, a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms, or a combination thereof. As the polymerizable group represented by G, the polymerizable group represented by G in the above formula (A-3-1) can be suitably adopted. ＸExamples of the divalent heteroatom-containing linking group represented by [the following formula] include R in the above formula (A-3). Ａ１ The above divalent heteroatom-containing linking group shown in [the above formula] can preferably be employed. L Ｘ Examples of the divalent hydrocarbon group having 1 to 10 carbon atoms represented by [the following formula] include a group obtained by removing one hydrogen atom from a group corresponding to 1 to 10 carbon atoms among the monovalent hydrocarbon groups having 1 to 20 carbon atoms shown in R in the above formula (A-3). Ａ１ When the divalent hydrocarbon group having 1 to 10 carbon atoms is substituted, the substituents shown in R in the above formula (A-3) can preferably be employed. Ａ１

[0069] In the above formula (X-1), R ａ１ , R ａ２ and R ａ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, -OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ , -O-, -CO- or a combination thereof, or represents a ring structure formed by combining two or more of these groups. The ring structure may be bonded to W-L Ｘ - in the above formula (X-1). The ring structure may contain a heteroatom such as O or S between the carbon-carbon bonds forming the skeleton. R Ｐ , R Ｑ and R Ｔ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2 and k3 are each independently an integer of 0 to 5. R ａ１ to R ａ３ as well as R Ｐ , R Ｑ and RＴ If each of them is multiple, then multiple R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ These may be the same or different.

[0070] In the above equation (X-2), R ｂ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxyl group. ｋ n is either 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When k4 is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ They may be the same or different, and there may be multiple R's. ｂ１ R may represent a ring structure formed by combining with other elements. ｂ２ This is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ k5 is a single bond or a divalent linking group. k5 is an integer from 0 to 4. ｂ２ If there are multiple R ｂ２ They may be the same or different, and there may be multiple R's. ｂ２ may represent a ring structure formed by combining with each other. q is an integer from 0 to 3. In the formula, S ＋ The ring structure containing may include heteroatoms such as O and S between the carbon-carbon bonds that form the skeleton.

[0071] In the above equation (X-3), R ｃ１ , R ｃ２ and R ｃ３ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0072] In the above equation (X-4), R ｇ１This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxyl group. ｋ２ n is either 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ They may be the same or different, and there may be multiple R's. ｇ１ R may represent a ring structure formed by combining with other elements. ｇ２ and R ｇ３ Each of these independently represents a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom having 6 to 12 carbon atoms, or a ring structure formed by combining these groups. k11 and k12 are each independently integers from 0 to 4. R ｇ２ and R ｇ３ If each of them is multiple, then multiple R ｇ２ and R ｇ３ These may be the same or different.

[0073] In the above equation (X-5), R ｄ１ and R ｄ２ Each of these independently represents a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by two or more of these groups combined. k6 and k7 are each independently integers from 0 to 5. R ｄ１ and R ｄ２ If each of them is multiple, then multiple R ｄ１ and R ｄ２ These may be the same or different.

[0074] In the above formula (X-6), R ｅ１ and R ｅ２ k8 and k9 are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms.

[0075] Specific examples of radiation-sensitive onium cations containing the polymerizable group mentioned above include, but are not limited to, the structures shown in formulas (1-2-1) to (1-2-46) below. Although the following formulas all show structures with polymerizable groups introduced, if the onium salt compound (1) satisfies any of the above requirements (1) to (3), a radiation-sensitive onium cation without polymerizable groups can be used. In this case, in the following formulas, G-L in formulas (X-1) to (X-6) above. Ｘ -The corresponding structure can be replaced with a hydrogen atom or other substituent, and a polymerizable group can be introduced to the anion. Other substituents include R in formula (A-3) above. Ａ１ The substituents shown in can be suitably adopted. Other substituents include halogen atoms, and more preferably fluorine atoms and iodine atoms.

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] The organic cation of structural unit (I) may be a diaryliodonium cation. The diaryliodonium cation preferably has one or more fluorine or iodine atoms. At least one of the aryl groups of the iodonium cation preferably has a fluorogroup-containing aromatic ring structure or an iodogroup-containing aromatic ring structure. A phenyl group is preferred as the aryl group. A polymerizable group may be bonded to the aryl group.

[0082] Specific examples of such iodonium cations are listed below. Although the following formulas all show structures in which the iodonium cation does not have polymerizable groups, if the onium salt compound (1) satisfies the above requirement (4), an iodonium cation with polymerizable groups can be used. In this case, in the following formula, the aryl group is connected to the G-L in formulas (X-1) to (X-6) above. Ｘ -The corresponding structure can be introduced, and the polymerizable group of the anion can be replaced with a hydrogen atom or other substituent. Other substituents include R in formula (A-3) above. Ａ１ The substituents shown in can be suitably adopted.

[0083]

[0084] The onium salt compound (1) can be obtained by appropriately combining the above anion and the above radiation-sensitive onium cation (the anion and the radiation-sensitive onium cation are not limited to the structures specifically shown). Specific examples, though not particularly limited, include structures of formulas (1-1) to (1-42) below.

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] The lower limit of the content of structural unit (I) (total content if multiple types are included) is preferably 1 mol%, more preferably 3 mol%, even more preferably 5 mol%, and particularly preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 50 mol%, more preferably 40 mol%, even more preferably 30 mol%, and particularly preferably 20 mol%. As a result, the composition can exhibit excellent sensitivity, LWR, and process window during resist pattern formation.

[0094] (Synthesis Method for Onium Salt Compound (1)) The synthesis method for onium salt compound (1) will be described in the case where A in formula (1) above is a hydroxyl group. Dihydroxybenzenesulfonic acid or a salt thereof (e.g., potassium salt) is reacted with (meth)acrylic acid halide to generate an anionic structure containing a polymerizable group, and this anionic structure is reacted with an onium cation halide salt corresponding to the onium cation (e.g., chloride salt) to carry out salt exchange, thereby synthesizing the desired onium salt compound (1). Onium salt compounds (1) having other structures can also be synthesized in a similar manner by appropriately selecting starting materials and precursors corresponding to the anion and onium cation.

[0095] [Structural Unit (II)] Structural unit (II) is a structural unit having an acid-dissociable group. An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group that dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer has structural unit (II).

[0096] Structural unit (II) is not particularly limited as long as it contains an acid-dissociable group, and examples include structural units having a tertiary alkyl ester moiety, a structure in which an aromatic group and an aliphatic hydrocarbon group are bonded to a secondary carbon atom in a secondary carboxylic acid ester structure, a structural unit having a structure in which a hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. However, from the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (II-1)") is preferred.

[0097]

[0098] In the above formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these independently represents either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

[0099] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (II-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0100] L １１ａ Examples of alkanediyl groups represented by include methylene groups, ethanediyl groups, 1,3-propanediyl groups, and 2,2-propanediyl groups, which have 1 to 10 carbon atoms. １１ａMethylene groups and ethanediyl groups are preferred as the base group.

[0101] L １１ａ Examples of allenediyl groups represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. １１ａ A benzenediyl group is preferred as the group.

[0102] L １１ａ The substituents that the arenediyl group represented by can have include, for example, halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; amino groups; alkoxy groups; alkoxycarbonyl groups; alkoxycarbonyloxy groups; acyl groups; acyloxy groups or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; oxo groups (=O), etc.

[0103] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (A-3), R Ａ１ Monovalent hydrocarbon groups having 1 to 20 carbon atoms, as shown in the above, can be suitably used.

[0104] The above R １８ Preferably, the hydrocarbon group is a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0105] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed when these are combined with the carbon atoms to which they are bonded, is R in formula (A-3) above. Ａ１ A group obtained by removing one hydrogen atom from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, as shown above, can be suitably adopted.

[0106] Among these, R １８ R is an alkyl group, alkenyl group, or phenyl group having 1 to 4 carbon atoms. １９ and R ２０ It is preferable that the alicyclic structure formed by combining these elements with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure.

[0107] The above R １８~R ２０ The substituents that can be present are L １１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0108] Examples of structural units (II-1) include those represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (II-1-1) to (II-1-15)").

[0109]

[0110]

[0111] In the above formulas (3-1) to (3-15), R １７ ~R ２０ This is equivalent to equation (3) above. R Ｌ１１ R is 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 integers from 1 to 4. k and l are 0 or 1. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0112] i and j are preferably 1 or 2. １８ Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, phenyl, and iodophenyl groups. １９ and R ２０ As such, methyl groups, ethyl groups, and isopropyl groups are preferred. Ｌ１１ By employing an iodine atom, an iodine group can be suitably introduced into the structural unit (II).

[0113] Furthermore, the polymer may contain structural units represented by the following formulas (1f) to (2f) as structural units (II).

[0114]

[0115] In the above equations (1f) to (2f), R αｆEach of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain-like alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0116] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0117] The lower limit of the content of structural unit (II) in the total structural units constituting the polymer (the total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, even more preferably 30 mol%, and particularly preferably 35 mol%. The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, even more preferably 50 mol%, and particularly preferably 45 mol%. By setting the content of structural unit (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0118] [Structural Unit (III)] Structural unit (III) is a structural unit having a phenolic hydroxyl group (excluding structures corresponding to structural units (I) to (II)). By including structural unit (III) in the polymer, the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity of the above-mentioned radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beams, etc. are used as the radiation irradiated in the exposure step in the resist pattern formation method, structural unit (III) contributes to improving etching resistance and improving the difference in developer solubility between the exposed and unexposed areas (dissolution contrast). In particular, it can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as electron beams and EUV. Structural unit (III) is preferably represented by the following formula (2).

[0119] (In the above formula (2), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊, -O- or -CONH- ＊ * indicates a bond on the aromatic ring side. １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxy group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４ m is an integer between 0 and 8, where 1 ≤ m ３ +m ４ ≤ 2n ３ (Saves +5.)

[0120] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (III), it is preferable that the atom is a hydrogen atom or a methyl group.

[0121] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0122] R １０２ In this mixture, iodine or fluorine atoms are preferred as halogen atoms, with iodine atoms being more preferred.

[0123] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0124] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0125] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0126] The above structural unit (III) is preferably a structural unit represented by the following formulas (2-1) to (2-25) (hereinafter also referred to as "structural unit (III-1) to structural unit (III-25)").

[0127]

[0128]

[0129] In the above equations (2-1) to (2-25), R β This is the same as equation (2) above.

[0130] When the base polymer has structural unit (III), the lower limit of the content of structural unit (III) (total content if multiple types are included) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total structural units constituting the polymer. The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of structural unit (III) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast.

[0131] [Structural Unit (IV)] The base polymer may contain structural unit (IV), which includes at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. By further containing structural unit (IV), the solubility of the base polymer in the developer can be adjusted, and as a result, the lithography performance such as resolution of the radiation-sensitive composition can be improved. In addition, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0132] As for the structural unit (IV), a structural unit containing a lactone structure is preferred, a structural unit containing a γ-butyrolactone structure or a norbornanelactone structure is more preferred, and a structural unit derived from γ-butyrolactone-yl (meth)acrylate or norbornanelactone-yl (meth)acrylate is even more preferred.

[0133] The lower limit of the content of structural units (IV) (total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of structural units (IV) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0134] [Structural Unit (V)] The base polymer may contain structural unit (V) containing a polar group (excluding those corresponding to structural units (I) to (IV)). The solubility of the base polymer in the developer can be adjusted by further containing structural unit (V). Examples of the above polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, sulfo groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred.

[0135] Examples of structural units (V) include structural units represented by the following formula.

[0136]

[0137]

[0138] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0139] When the base polymer has the above-mentioned structural unit (V), the lower limit of the content of structural unit (V) (total content if multiple types are included) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol%. By setting the content of structural unit (V) within the above range, the solubility of the base polymer in the developer can be efficiently adjusted.

[0140] [Structural Unit (VI)] The base polymer may include structural unit (VI), which has a second organic acid anion and a second onium cation, and includes a second acid generating structure that generates an acid by exposure without dissociating the acid-dissociable group. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the above-mentioned radiation-sensitive composition, the second acid generating structure substantially prevents the dissociation of the acid-dissociable group of structural unit (II), and has the function of suppressing the diffusion of acid generated from structural unit (I) or the radiation-sensitive acid generating agent (if included) in the unexposed area by salt exchange. The acid generated from the second acid generating structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from structural unit (I) or the radiation-sensitive acid generating agent. The distinction between the function of a radiation-sensitive acid-generating structure and an acid-diffusion-controlling structure is determined by the energy required for the dissociation of the acid-dissociable groups possessed by the polymer's structural unit (II), and the acidity of the acid generated from structural unit (I).

[0141] Examples of secondary organic acid anions that give structural unit (VI) include, but are not limited to, those listed below. While all of the secondary organic acid anions listed below have an iodine group or a hydroxyl group, structural unit (VI) does not necessarily require an iodine group or a hydroxyl group. For secondary organic acid anions that do not have an iodine group or a hydroxyl group, structures in which the iodine group or hydroxyl group in the following formula is replaced with a hydrogen atom or the substituent indicated by W in formula (1) above can be suitably adopted. It is preferable that the secondary organic acid anion has a carboxylic acid anion and a hydroxyl group. In this case, it is preferable that the carboxylic acid anion and the hydroxyl group are bonded to the same aromatic ring in the secondary organic acid anion, and it is more preferable that the carbon atom to which the carboxylic acid anion is bonded and the carbon atom to which the hydroxyl group is bonded are directly connected to each other on the same aromatic ring.

[0142]

[0143]

[0144] In the formula, R ＡThese are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0145] As the second onium cation of structural unit (VI), the radiation-sensitive onium cation of onium salt compound (1) (provided it does not contain polymerizable groups) can be suitably used.

[0146] In addition, a configuration can be adopted in which a second onium cation is bonded to the main chain as the side chain structure of the base polymer, and a second organic acid anion is ionically bonded to the second onium cation as a counterion. In this case, it is preferable that the second onium cation is bonded to the main chain via a divalent linking group or a single bond, and the anionic structure of the above formula is ionically bonded to the second onium cation as a counterion. The divalent linking group is L of formula (3) above. １１ A group represented by or the above-mentioned divalent heteroatom-containing linking group can be suitably adopted.

[0147] When the base polymer contains structural unit (VI), the lower limit of the content of structural unit (VI) (or the total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 10 mol%. By setting the content of structural unit (VI) within the above range, the structure can fully exhibit its function as an acid diffusion control structure.

[0148] (Method for synthesizing base polymers) Base polymers can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0149] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight-average molecular weight (Mw) in polystyrene terms, calculated by gel permeation chromatography (GPC), is preferably 2,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 16,000, and even more preferably 12,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0150] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0151] The methods for measuring Mw and Mn of polymers in this specification are as described in the examples.

[0152] The lower limit of the base polymer content is preferably 40% by mass, more preferably 50% by mass, and even more preferably 60% by mass, relative to the total solid content of the radiation-sensitive composition. The upper limit of the above content is preferably 99% by mass, and more preferably 90% by mass.

[0153] (Other Polymers) The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer with a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, it can be unevenly distributed on the surface of the resist film relative to the base polymer, and as a result, surface modification of the resist film and control of the distribution of the film composition during EUV exposure can be achieved.

[0154] As a high-fluorine-content polymer, it is preferable to have a structural unit (hereinafter also referred to as "structural unit (i)") having a structure in which a fluorine atom is bonded to the carbon atom at the α, β, or γ position of the ester bond, and may optionally have structural unit (II), structural unit (V), and other structural units in the base polymer. Examples of structural unit (i) include the structure represented by the following formula.

[0155]

[0156]

[0157] When a high-fluorine-content polymer contains structural unit (i), the lower limit of the content of structural unit (i) (total if multiple types are included) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol% relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content may be 100 mol%, 90 mol%, or 85 mol%. By setting the content of structural unit (i) within the above range, the surface segregation of the high-fluorine-content polymer and the solubility of the resist film surface can be improved.

[0158] The lower limit of Mw for the high-fluorine-content polymer is preferably 2,000, more preferably 4,000, and even more preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 15,000, and even more preferably 10,000.

[0159] The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, and 1.1 is more preferred. The upper limit of Mw / Mn is usually 5, 3 is preferred, and 2 is more preferred.

[0160] If the radiation-sensitive composition contains a high-fluorine content polymer, the amount of the high-fluorine content polymer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the base polymer. Furthermore, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less.

[0161] (Method for synthesizing high-fluorine content polymers) High-fluorine content polymers can be synthesized by the same method as the base polymer synthesis method described above.

[0162] (Radiation-sensitive acid generator) The radiation-sensitive composition of this embodiment may further contain a radiation-sensitive acid generator having a third organic acid anion and a third onium cation, which generates acid upon irradiation (exposure) with radiation. If the polymer contains structural unit (II) having an acid-dissociable group, the acid generated from the radiation-sensitive acid generator upon exposure can dissociate the acid-dissociable group of structural unit (II), generating a carboxyl group or the like. As for the form in which the radiation-sensitive acid generator is contained, it is preferable that it exists as a compound on its own (liberated from the polymer), rather than being incorporated as part of the polymer, as in the onium salt compound (1).

[0163] The radiation-sensitive composition contains the above-mentioned radiation-sensitive acid generator, which increases the polarity of the polymer in the exposed area. As a result, the polymer in the exposed area becomes soluble in the developer in the case of alkaline aqueous solution development, while it becomes sparingly soluble in the developer in the case of organic solvent development.

[0164] Examples of radiation-sensitive acid generators include onium salts (excluding the onium salt compound (1) mentioned above), sulfonimide compounds, halogen-containing compounds, and diazoketone compounds. Examples of onium salts include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts. Of these, sulfonium salts and iodonium salts are preferred. As the third onium cation, the radiation-sensitive onium cation of the onium salt compound (1) (excluding polymerizable groups) can be suitably used.

[0165] Acids generated by exposure include those that produce sulfonic acids upon exposure. Examples of such acids include compounds in which at least one carbon atom at the α or β position of a sulfo group is substituted with one or more fluorine atoms, fluorinated hydrocarbon groups, or cyano groups. Among these, those having a cyclic structure are particularly preferred as radiation-sensitive acid generators.

[0166] Examples of the third organic acid anion for the radiation-sensitive acid generator are, but are not limited to, those listed below. Note that the iodine group in the following formulas may be substituted with a hydrogen atom or other substituents.

[0167]

[0168]

[0169] These radiation-sensitive acid generators may be used individually or in combination of two or more. The lower limit of the content of the radiation-sensitive acid generator (or the total content when multiple radiation-sensitive acid generators are used in combination) is preferably 2 parts by mass, more preferably 5 parts by mass, and even more preferably 8 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the content is preferably 40 parts by mass, more preferably 30 parts by mass, and even more preferably 25 parts by mass, per 100 parts by mass of the base polymer. This allows the excellent resist properties described above to be exhibited during resist pattern formation.

[0170] (Acid Diffusion Control Agent) The radiation-sensitive composition may optionally contain an acid diffusion control agent. The acid diffusion control agent controls the diffusion phenomenon of acid generated from structural unit (I) or radiation-sensitive acid generator (if present) in the resist film upon exposure, and has the effect of suppressing undesirable chemical reactions in unexposed areas. In addition, the storage stability of the resulting radiation-sensitive composition is improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the setting time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0171] Examples of acid diffusion control agents include compounds represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compounds (I)"), compounds having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compounds (II)"), compounds having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compounds (III)"), amide group-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, and the like.

[0172]

[0173] In the above formula (7), R ２２ , R ２３ and R ２４ Each of these is independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0174] Examples of nitrogen-containing compounds (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0175] Examples of nitrogen-containing compounds (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0176] Examples of nitrogen-containing compounds (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0177] Examples of amide group-containing compounds include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0178] Examples of urea compounds include urea, methyl urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0179] Examples of nitrogen-containing heterocyclic compounds include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; and pyrazines and pyrazoles.

[0180] Furthermore, compounds having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of nitrogen-containing organic compounds having an acid-dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0181] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as an acid diffusion control agent. The acid generated from the above-mentioned radiation-sensitive weak acid generator is a weak acid that does not induce the dissociation of the acid-dissociable groups in the polymer under conditions that would normally cause the dissociation of those groups.

[0182] Examples of radiation-sensitive weak acid generators include onium salt compounds that decompose upon exposure and lose their ability to control acid diffusion. Examples of onium salt compounds include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Also, examples include compounds containing a sulfonium cation and anion in the same molecule, represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule, represented by the following formula (8-4).

[0183]

[0184] In the above formulas (8-1) to (8-4), J ＋ It is a sulfonium cation, U ＋ This is an iodonium cation. ＋ Examples of sulfonium cations represented by the above formulas (X-1) to (X-4) include U ＋Examples of iodonium cations represented by the above formulas (X-5) to (X-6) include iodonium cations represented by E. - and Q - Each of them is independent of OH - , R α -COO - , R α -SO ３ - This is an anion represented by R. α This refers to a single bond or a monovalent organic group having 1 to 30 carbon atoms. Examples of such organic groups include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups having a divalent heteroatom-containing linking group between carbon atoms or at the end of the carbon chain of the hydrocarbon group, groups in which some or all of the hydrogen atoms of the hydrocarbon group are replaced with a monovalent heteroatom-containing group, or combinations thereof. E - and Q - R α -SO ３ - In the case of R α SO in ３ - Neither the α-position nor the β-position carbon atom is bonded to an electron-withdrawing group. Examples of electron-withdrawing groups include fluorine atoms, fluorinated hydrocarbon groups, or cyano groups.

[0185] As a monovalent hydrocarbon group having 1 to 20 carbon atoms, R in the above formula (A-3) is Ａ１ Monovalent hydrocarbon groups having 1 to 20 carbon atoms, as shown in the above, can be suitably used.

[0186] Examples of heteroatoms that constitute a divalent heteroatom-containing linking group or a monovalent heteroatom-containing group include oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0187] As a divalent heteroatom-containing linking group, R in formula (A-3) above is Ａ１ The divalent heteroatom-containing linking group shown can be suitably adopted.

[0188] Examples of monovalent heteroatom-containing groups include hydroxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0189] Examples of anions for the above-mentioned acid diffusion control agent include, but are not limited to, those listed below. Compounds containing both an iodonium cation and anion within the same molecule, and compounds containing both a sulfonium cation and anion within the same molecule are also given as examples. The iodine group in the following formulas may be substituted with a hydrogen atom or other substituents.

[0190]

[0191]

[0192] As the onium cation in the above acid diffusion control agent, the structure of the radiation-sensitive onium cation (but without polymerizable groups) of structural unit (I) in the above base polymer can be suitably adopted.

[0193] The above-mentioned acid diffusion control agents can also be synthesized by known methods, particularly by salt exchange reactions.

[0194] These acid diffusion control agents may be used individually or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion control agent, the lower limit of the acid diffusion control agent content (total in the case of multiple types) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total amount of the onium salt compound (1) that gives the structural unit (I) of the base polymer and the radiation-sensitive acid generator (if included). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%.

[0195] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing the base polymer and optionally contained additives.

[0196] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0197] Examples of alcohol-based solvents include monoalcohol solvents having 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; polyhydric alcohol solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether solvents, such as propylene glycol monomethyl ether, in which some of the hydroxyl groups of the above-mentioned polyhydric alcohol solvents are etherified. In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0198] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

[0199] Examples of ketone solvents include: linear ketone solvents such as acetone, butanone, and methyl-isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0200] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain-like amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0201] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate.

[0202] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbencene, and n-amylnaphthalene.

[0203] Among these, ester solvents, ether solvents, and alcohol solvents are preferred, polyhydric alcohol partial ether acetate solvents, polyhydric alcohol partial ether solvents, and monoalcohol solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and diacetone alcohol are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0204] <Other Optional Components> The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization accelerators, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0205] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing a base polymer and a solvent with other optional components as needed in a predetermined ratio. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 0.05 μm to 0.4 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0206] <Pattern Forming Method> The pattern forming method in this embodiment includes the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (1) (hereinafter also referred to as the "resist film forming step"), exposing the resist film to light (2) (hereinafter also referred to as the "exposure step"), and developing the exposed resist film with a developer (3) (hereinafter also referred to as the "development step").

[0207] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, LWR, and process window during pattern formation is used, high-quality resist patterns can be efficiently formed. The following describes each step.

[0208] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the radiation-sensitive composition described above. Examples of substrates for forming this resist film include conventionally known materials such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective film, such as those disclosed in Japanese Patent Publication No. 6-12452 or Japanese Patent Publication No. 59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting, and roll coating. After coating, soft baking (SB) may be performed as needed to volatilize the solvent in the coating film. The SB temperature is usually 80°C to 180°C, with 100°C to 150°C being preferred. The SB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred. The thickness of the formed resist film is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0209] [Exposure Process] In this process (process (2) above), the resist film formed in the resist film formation process, which is process (1) above, is exposed by irradiating it with radiation through a photomask. The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; for example, electron beams and charged particle beams such as alpha rays. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0210] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from structural units (IIa) and radiation-sensitive acid generators during exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 50°C to 150°C, with 80°C to 130°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0211] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed with a developer. This allows a predetermined resist pattern to be formed. After development, it is common to wash with a rinsing solution such as water or alcohol and then dry it.

[0212] Examples of developers used in the above development process include, in the case of alkaline development, an alkaline aqueous solution containing at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium 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 TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0213] In addition, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As for ester solvents, acetic acid ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than organic solvents in the developer include water and silicone oil.

[0214] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by puddling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0215] <Onium Salt Compounds> Another embodiment of the onium salt compound is a compound represented by the following formula (1). (In formula (1), W is a cyclic structure with 3 to 40 members, formed together with the two carbon atoms in formula (1). The following carbon-carbon expressions represent single or double bonds.) A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7). (In formulas (A-3) and (A-4), R Ａ１ and R Ａ２Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. * indicates a bond with a carbon atom. ) R １ R is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom, or a thiol group. １ If multiple R １ They are either identical or different from each other. １ Z is an integer between 0 and 4. ＋ A is a monovalent radiation-sensitive onium cation. However, the onium salt compound represented by the above formula (1) satisfies any one of the following requirements (1) to (4). Requirement (1): A is a group represented by the above formula (A-3), and R Ａ１ is a monovalent organic group having 1 to 20 carbon atoms that contains a polymerizable group. Requirement (2): A is a group represented by the above formula (A-4), and R Ａ２ This is a monovalent organic group having 1 to 20 carbon atoms that contains a polymerizable group. Requirement (3): m １ is an integer from 1 to 4, and m １ Individual R １ One of them is a monovalent organic group having 1 to 20 carbon atoms that contains a polymerizable group. Requirement (4): Z ＋ (This is a monovalent, radiation-sensitive onium cation containing a polymerizable group.)

[0216] In this embodiment, the onium salt compound (1) that gives structural unit (I) contained in the above-mentioned radiation-sensitive composition can be suitably used as the onium salt compound represented by formula (1).

[0217] <Polymer> The polymer according to this embodiment is a polymer that includes structural unit (I) derived from the above onium salt compound.

[0218] As the polymer according to this embodiment, the polymer (base polymer) contained in the above-mentioned radiation-sensitive composition can be suitably used.

[0219] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" refer to mass unless otherwise specified. The measurement methods for each physical property are shown below.

[0220] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymers] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymers were measured by gel permeation chromatography (GPC) using Tosoh Corporation's GPC columns (two "G2000HXL" columns, one "G3000HXL" column, and one "G4000HXL" column) under the following conditions: Eluent: Tetrahydrofuran (Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Column temperature: 40°C Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0221] <Synthesis of [M] Monomer> [Example M-21] Synthesis of monomer (M-21) Monomer (M-21) was synthesized according to the reaction scheme below.

[0222]

[0223] 50 mmol of 2,4-dihydroxybenzenesulfonic acid, 110 mmol of triethylamine, and 200 mL of tetrahydrofuran were added to the reaction vessel and then cooled to 0°C. 60 mmol of methacryloyl chloride was added dropwise at 0°C and the mixture was stirred at room temperature for 3 hours. After removing the solvent, 200 mL of DCM (dichloromethane), 200 mL of ultrapure water, and 55 mmol of the compound represented by formula (C-1) were added to the reaction vessel and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography yielded monomer (M-21).

[0224] [Example M-22] Synthesis of monomer (M-22) Monomer (M-22) was synthesized according to the reaction scheme below.

[0225]

[0226] 500 mL of ultrapure water, 50 mmol of 2,4-dihydroxybenzenesulfonic acid, 50 mmol of iodine, 100 mL of potassium carbonate, and 1 mmol of potassium iodide were added to a reaction vessel and stirred at room temperature for 3 hours. After filtering the solid, it was washed with ultrapure water to obtain (pM-22). Next, monomer (M-22) was synthesized in the same manner as in Example M-21, except that (pM-22) was used instead of 2,4-dihydroxybenzenesulfonic acid and (C-2) was used instead of (C-1).

[0227] [Example M-23] Synthesis of monomer (M-23) As shown in the scheme below, (pM-23) was obtained in the same manner as in Example M-22, except that the equivalent amounts of 2,4-dihydroxybenzenesulfonic acid, iodine, potassium carbonate, and potassium iodide were adjusted. Next, monomer (M-23) was synthesized in the same manner as in Example M-21, except that (pM-23) was used instead of 2,4-dihydroxybenzenesulfonic acid in Example M-21, and (C-3) was used instead of (C-1).

[0228]

[0229] [Example M-24] Synthesis of monomer (M-24) Monomer (M-24) was synthesized according to the following reaction scheme.

[0230]

[0231] 50 mmol of 4-vinylbenzoic acid, 2 mmol of N,N-dimethylformamide, and 100 mL of acetonitrile were added to the reaction vessel and cooled to 0°C. 80 mmol of oxalyl dichloride was added dropwise, and the mixture was stirred at room temperature for 1 hour. After removing the solvent, (pM-A) was obtained. 50 mmol of 2,4-dihydroxybenzenesulfonic acid, 110 mmol of triethylamine, and 150 mL of tetrahydrofuran were added to the reaction vessel and cooled to 0°C. 45 mmol of (pM-A), dissolved in 50 mL of tetrahydrofuran, was added dropwise at 0°C and the mixture was stirred at room temperature for 3 hours. After removing the solvent, 200 mL of dichloromethane, 200 mL of ultrapure water, and 50 mmol of the compound represented by formula (C-4) were added to the reaction vessel and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. The monomer (M-24) was obtained by purification using silica gel chromatography.

[0232] [Examples M-25 to M-28] Synthesis of monomers (M-25) to (M-28) Monomers (M-25) to (M-28) were synthesized in the same manner as in Example M-21, except that the substrate used was appropriately selected.

[0233]

[0234] [Examples M-29 to M-30] Synthesis of monomers (M-29) to (M-30) Monomers (M-29) to (M-30) were synthesized in the same manner as in Example M-24, except that the substrate used was appropriately selected.

[0235]

[0236] [Example M-31] Synthesis of monomer (M-31) Monomer (M-31) was synthesized according to the following reaction scheme.

[0237]

[0238] 30 mmol of 4-hydroxystyrene, 33 mmol of monosodium 2-sulfoterephthalate, 33 mmol of EDC ((1-(3-dimethylaminopropyl)-3-ethylcarbodiimide)), 6 mmol of DMAP (4-dimethylaminopyridine), and 50 mL of tetrahydrofuran were added to the reaction vessel and stirred at room temperature for 2 hours. After removing the solvent, 50 mL of dichloromethane, 50 mL of ultrapure water, and 35 mmol of the compound represented by formula (C-5) were added to the reaction vessel and stirred at room temperature for 1 hour. The organic layer was separated and washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography yielded monomer (M-31).

[0239] [Examples M-32 to M-37] Synthesis of monomers (M-32) to (M-37) Monomers (M-32) to (M-37) were synthesized in the same manner as in Example M-31, except that the substrate used was appropriately selected.

[0240]

[0241] [Examples M-38 to M-41] Synthesis of monomers (M-38) to (M-41) Monomers (M-38) to (M-41) were synthesized in the same manner as in Example M-21, except that the substrate used was appropriately selected.

[0242]

[0243] [Examples M-42 to M-43] Synthesis of monomers (M-42) to (M-43) Monomers (M-42) to (M-43) were synthesized in the same manner as in Example M-24, except that the substrate used was appropriately selected.

[0244]

[0245] [Example M-44] Synthesis of monomer (M-44) Monomer (M-44) was synthesized according to the following reaction scheme.

[0246]

[0247] 50 mmol of 2,4-diaminobenzenesulfonic acid, 60 mmol of triethylamine, and 200 mL of tetrahydrofuran were added to the reaction vessel and cooled to 0°C. 50 mmol of methacryloyl chloride was added dropwise at 0°C and the mixture was stirred at room temperature for 3 hours. 100 mL of ethyl acetate and 50 mL of 2 M hydrochloric acid were added to separate the organic layer. The organic layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. The mixture was purified by silica gel chromatography to obtain (pM-44). 40 mmol of (pM-44), 50 mmol of triethylamine, and 100 mL of tetrahydrofuran were added to the reaction vessel and cooled to 0°C. 60 mmol of acetyl chloride was added dropwise at 0°C and the mixture was stirred at room temperature for 3 hours. After removing the solvent, 200 mL of dichloromethane, 200 mL of ultrapure water, and 55 mmol of the compound represented by formula (C-6) were added to the reaction vessel and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography yielded monomer (M-44).

[0248] [Examples M-45 to M-46] Synthesis of monomers (M-45) to (M-46) Monomers (M-45) to (M-46) were synthesized in the same manner as in Example M-44, except that the substrate used was appropriately selected.

[0249]

[0250] [Example M-47] Synthesis of monomer (M-47) Monomer (M-47) was synthesized according to the following reaction scheme.

[0251]

[0252] 50 mmol of 2-sulfobenzoic anhydride, 60 mmol of 4-vinylaniline, 60 mmol of potassium carbonate, and 200 mL of dichloromethane were added to the reaction vessel and stirred at room temperature for 3 hours. 50 mL of ultrapure water and 55 mmol of the compound represented by formula (C-2) were added to the reaction vessel and stirred at room temperature for 1 hour. The organic layer was separated and washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The mixture was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography yielded monomer (M-47).

[0253] [Examples M-48 to M-53] Synthesis of monomers (M-48) to (M-53) Monomers (M-48) to (M-53) were synthesized in the same manner as in Example M-47, except that the substrate used was appropriately selected.

[0254]

[0255] [Example M-54] Synthesis of monomer (M-54) Monomer (M-54) was synthesized according to the following reaction scheme.

[0256]

[0257] 100 mmol of 3,5-diiodosalicylic acid, 20 mmol of DMAP, 80 mL of t-butanol, and 20 mL of tetrahydrofuran were added to the reaction vessel and cooled to 0°C. 110 mmol of EDC was added at 0°C and the mixture was stirred at room temperature for 3 hours. After removing the solvent, 200 mL of dichloromethane and 200 mL of ultrapure water were added to the reaction vessel and the organic layer was separated. The organic layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography yielded (p3M-54).

[0258] 80 mmol of (p3M-54), 80 mmol of 4-vinylbenzoic acid, 16 mmol of DMAP, and 80 mL of tetrahydrofuran were added to the reaction vessel and then cooled to 0°C. 110 mmol of EDC was added at 0°C and the mixture was stirred at room temperature for 3 hours. After removing the solvent, 200 mL of dichloromethane and 200 mL of ultrapure water were added to the reaction vessel and the organic layer was separated. The organic layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The mixture was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography yielded (p2M-54).

[0259] 60 mmol of (p2M-54), 60 mL of dichloromethane, and 6 mmol of sulfuric acid were added to a reaction vessel and stirred at room temperature for 3 hours. The reaction solution was filtered, and the resulting solid was washed with dichloromethane to obtain (pM-54). 50 mmol of (pM-54), 55 mmol of the compound represented by formula (C-7), 50 mmol of 2-aminobenzenesulfonic acid, 1 mmol of DMAP, and 50 mL of tetrahydrofuran were added to the reaction vessel and cooled to 0°C. 55 mmol of EDC was added at 0°C and stirred at room temperature for 3 hours. After removing the solvent, 200 mL of dichloromethane and 200 mL of ultrapure water were added to the reaction vessel and the organic layer was separated. The organic layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography was performed to obtain monomer (M-54).

[0260] [Examples M-55 to M-59] Synthesis of monomers (M-55) to (M-59) Monomers (M-55) to (M-59) were synthesized in the same manner as in Example M-54, except that the substrate used was appropriately selected.

[0261]

[0262] [Example M-60] Synthesis of monomer (M-60) Monomer (M-60) was synthesized according to the following reaction scheme.

[0263]

[0264] 60 mmol of 2-amino-3,5-diiodobenzoic acid, 60 mmol of 2-sulfobenzoic anhydride, 60 mmol of potassium carbonate, and 200 mL of dichloromethane were added to the reaction vessel and stirred at room temperature for 3 hours. The solid was filtered and washed with 50 mL of ultrapure water and 50 mL of dichloromethane to obtain (pM-60). 50 mmol of (pM-60), 55 mmol of the compound represented by the above formula (C-7), 50 mmol of 4-vinylphenol, 1 mmol of DMAP, and 50 mL of tetrahydrofuran were added to the reaction vessel and then cooled to 0°C. 55 mmol of EDC was added at 0°C and stirred at room temperature for 3 hours. After removing the solvent, 200 mL of dichloromethane and 200 mL of ultrapure water were added to the reaction vessel and the organic layer was separated. The organic layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. Then it was dried over anhydrous sodium sulfate to remove the solvent. The monomer (M-60) was obtained by purification using silica gel chromatography.

[0265] [Example M-61] Synthesis of monomer (M-61) Monomer (M-61) was synthesized in the same manner as in Example M-60, except that the substrate used was appropriately selected.

[0266]

[0267] [Example M-62] Synthesis of monomer (M-62) Monomer (M-62) was synthesized according to the following reaction scheme.

[0268]

[0269] 50 mmol of the compound represented by formula (C-8), 60 mmol of triethylamine, and 100 mL of tetrahydrofuran were added to the reaction vessel and then cooled to 0°C. 60 mmol of methacryloyl chloride was added dropwise at 0°C and the mixture was stirred at room temperature for 3 hours. After removing the solvent, 200 mL of dichloromethane, 200 mL of ultrapure water, and 55 mmol of 2-hydroxybenzenesulfonic acid were added to the reaction vessel and the mixture was stirred at room temperature for 1 hour. The organic layer was separated and washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, once with 50 mL of 2 M hydrochloric acid, and once with 50 mL of ultrapure water. The layer was then dried over anhydrous sodium sulfate to remove the solvent. Purification by silica gel chromatography yielded monomer (M-62).

[0270] [Examples M-63 to M-67] Synthesis of monomers (M-63) to (M-67) Monomers (M-63) to (M-67) were synthesized in the same manner as in Example M-62, except that the substrate used was appropriately selected.

[0271]

[0272] <[A] Synthesis of Polymers> [Examples A-1 to A-68 and Comparative Examples A-69 to A-70] Synthesis of polymers (A-1) to (A-70) The monomers were combined in the compositions shown in Tables 1-1 and 1-2 below, and copolymerization was carried out under tetrahydrofuran (THF) solvent. The reaction solution was added to methanol to precipitate the copolymer, and after washing with hexane a predetermined number of times, it was isolated and dried to obtain polymers (A-1) to (A-70). The Mw and dispersion (Mw / Mn) of the polymers were measured by the above procedure.

[0273]

[0274]

[0275] The monomers used in the synthesis of the polymer, in addition to monomers (M-21) to (M-67), are listed below.

[0276]

[0277]

[0278]

[0279] <Preparation of Radiation-Sensitive Composition> The [B] radiation-sensitive acid generator, [Z] acid diffusion control agent, and [D] solvent used in the preparation of the radiation-sensitive composition are shown below. In the following examples and comparative examples, unless otherwise specified, "parts by mass" refers to the value when the mass of the [A] polymer used is 100 parts by mass.

[0280] [B] Radiation-sensitive acid generators [B] Compounds represented by the following formulas (B-1) to (B-4) (hereinafter also referred to as "radiation-sensitive acid generators (B-1) to (B-4)") were used as radiation-sensitive acid generators.

[0281]

[0282] [[Z] Acid Diffusion Controller] As the [[Z] acid diffusion controller, compounds represented by the following formulas (Z-1) to (Z-4) (hereinafter also referred to as "acid diffusion controllers (Z-1) to (Z-4)") were used.

[0283]

[0284] [[D] Solvent] As the [[D] solvent, the following organic solvents were used. (D-1): Propylene glycol monomethyl ether acetate (D-2): Propylene glycol monomethyl ether (D-3): Diacetone alcohol

[0285] [Examples 1 to 75 and Comparative Examples 1 to 3] Preparation of Radiation-Sensitive Composition [[A] Polymer, [[B] Radiation-Sensitive Acid Generator, [[Z] Acid Diffusion Controller, and [[D] Solvent were each blended in a specified amount. The obtained mixture was filtered through a membrane filter with a pore size of 0.20 μm to prepare a radiation-sensitive composition. The prepared radiation-sensitive compositions (R-1) to (R-75) and (CR-1) to (CR-3) are shown in Tables 2-1 and 2-2 below. The content of the [[Z] acid diffusion controller is expressed in mol% with respect to the total content of the monomer that gives the structural unit (I) of the [[A] polymer and the content of the [[B] radiation-sensitive acid generator.

[0286]

[0287]

[0288] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 40 nm thick underlayer film (AL412 (manufactured by Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron). After soft baking at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 50 nm thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA = 0.33, illumination conditions: Conventional s = 0.89, mask: imecDEFECT32FFR02). Subsequently, the resist film was subjected to PEB at 110°C for 60 seconds. Next, a 2.38% by mass aqueous TMAH solution was used to develop the image at 23°C for 30 seconds, forming a positive-type 40 nm line-and-space pattern.

[0289] <Evaluation> The sensitivity, LWR, and process window of each radiation-sensitive composition were evaluated by measuring each resist pattern formed as described above according to the method below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-4100") was used to measure the length of the resist patterns. The evaluation results are shown in Tables 3-1 and 3-2 below.

[0290] [Sensitivity] In forming the resist pattern described above, the exposure amount used to form the 40 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The smaller the sensitivity value, the better, as it allows for the formation of the desired resist pattern with less exposure.

[0291] [LWR] The formed resist pattern was observed from above using the scanning electron microscope described above. The line width was measured at 50 arbitrary points, and the 3-sigma value was determined from the distribution of these measurements. This was defined as the LWR (unit: nm). A smaller LWR value indicates less jaggedness in the lines and a better result.

[0292] [Process Window] Patterns were formed by varying the exposure from low to high exposure using a mask that forms a 40 nm line and space. Generally, connections between patterns are observed at low exposures, while defects such as pattern collapse are observed at high exposures. The difference between the upper and lower limits of the resist dimensions where these defects are not observed was defined as the "CD (Critical Dimension) margin." A larger CD margin value indicates a wider process window. A CD margin value of 19 nm or more was judged as "A" (excellent), 15 nm or more but less than 19 nm as "B" (good), 11 nm or more but less than 15 nm as "C" (somewhat poor), and less than 11 nm as "D" (poor).

[0293]

[0294]

[0295] As is clear from the results in Tables 3-1 and 3-2, all of the radiation-sensitive compositions of Examples 1 to 75 showed better sensitivity, LWR, and process window compared to the radiation-sensitive compositions of Comparative Examples 1 to 3.

[0296] The radiation-sensitive composition of the present invention, which contains a polymer comprising structural units derived from the onium salt compound (1) described above, exhibits good sensitivity to exposure, a wide process window, and excellent low-wavelength ratio (LWR). Therefore, the radiation-sensitive composition of the present invention, the pattern formation method using the same, the onium salt compound, and the polymer are suitable for semiconductor device processing processes and the like, where further miniaturization is expected in the future.

Claims

1. A radiation-sensitive composition comprising a polymer containing a structural unit (I) derived from an onium salt compound represented by the following formula (1) and a solvent. (In formula (1), W is a cyclic structure having 3 to 40 ring members formed together with two carbon atoms in formula (1). The following formula between carbon-carbon represents a single bond or a double bond.) A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7). (In formula (A-3) and formula (A-4), R Ａ１ and R Ａ２ are each independently a monovalent organic group having 1 to 20 carbon atoms. * is a bond to a carbon atom.) R １ is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxy group, a hydroxy group, an amino group, a halogen atom, or a thiol group. When a plurality of R １ are present, the plurality of R １ are the same as or different from each other. m １ is an integer of 0 to 4. Z ＋ is a monovalent radiation-sensitive onium cation. However, the onium salt compound represented by formula (1) satisfies any one of the following requirements (1) to (4). Requirement (1): A is a group represented by the above formula (A-3), and R Ａ１ is a monovalent organic group having 2 to 20 carbon atoms containing a polymerizable group. Requirement (2): A is a group represented by the above formula (A-4), and R Ａ２ is a monovalent organic group having 2 to 20 carbon atoms containing a polymerizable group. Requirement (3): m １ is an integer of 1 to 4, and one of the m １ R １ is a monovalent organic group having 2 to 20 carbon atoms containing a polymerizable group. Requirement (4): Z ＋ is a monovalent radiation-sensitive onium cation containing a polymerizable group.) 2. The radiation-sensitive composition according to claim 1, wherein W is an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, an aromatic hydrocarbon structure having 6 to 20 carbon atoms, an aliphatic heterocyclic structure having 3 to 20 carbon atoms, or an aromatic heterocyclic structure having 3 to 20 carbon atoms.

3. The radiation-sensitive composition according to claim 1, wherein the content of the structural unit (I) in the total number of constituent units of the polymer is 1 mol% or more and 30 mol% or less.

4. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the polymer further comprises a structural unit (II) having an acid-dissociable group.

5. The radiation-sensitive composition according to claim 4, wherein the above structural unit (II) is represented by the following formula (3). (In formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these independently represents either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

6. The radiation-sensitive composition according to claim 4, wherein the above structural unit (II) is represented by the following formula (3-1) or formula (3-9). (In equations (3-1) and (3-9), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ This is a methyl group, ethyl group, ethenyl group, isopropyl group, t-butyl group, or phenyl group. Ｌ１１ R is 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. Each of 3a is an integer from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ (These two elements are either identical or different. i is an integer between 1 and 4.) 7. The radiation-sensitive composition according to claim 4, wherein the content of structural unit (II) in the total structural units constituting the polymer is 10 mol% or more and 80 mol% or less.

8. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the polymer further comprises a structural unit (III) having a phenolic hydroxyl group.

9. The radiation-sensitive composition according to claim 8, wherein the content of structural unit (III) in the total structural units constituting the polymer is 20 mol% or more and 70 mol% or less.

10. A radiation-sensitive composition according to any one of claims 1 to 3, further comprising an acid diffusion control agent.

11. A pattern forming method comprising the steps of: applying a radiation-sensitive composition according to any one of claims 1 to 3 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

12. The pattern formation method according to claim 11, wherein the exposure is performed using an ArF excimer laser or extreme ultraviolet light.

13. An onium salt compound represented by the following formula (1). (In formula (1), W is a cyclic structure with 3 to 40 members, formed together with the two carbon atoms in formula (1). The following carbon-carbon expressions represent single or double bonds.) A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7). (In formulas (A-3) and (A-4), R Ａ１ and R Ａ２ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. * indicates a bond with a carbon atom. ) R １ R is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom, or a thiol group. １ If multiple R １ They are either identical or different from each other. １ Z is an integer between 0 and 4. ＋ A is a monovalent radiation-sensitive onium cation. However, the onium salt compound represented by the above formula (1) satisfies any one of the following requirements (1) to (4). Requirement (1): A is a group represented by the above formula (A-3), and R Ａ１ is a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group. Requirement (2): A is a group represented by the above formula (A-4), and R Ａ２ This is a monovalent organic group having 2 to 20 carbon atoms that contains a polymerizable group. Requirement (3): m １ is an integer from 1 to 4, and m １ Individual R １ One of them is a monovalent organic group with 2 to 20 carbon atoms that contains a polymerizable group. Requirement (4): Z ＋ (This is a monovalent, radiation-sensitive onium cation containing a polymerizable group.) 14. A polymer comprising structural unit (I) derived from the onium salt compound described in claim 13.

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