TW202600501A - Radiosensitive components, pattern forming methods, compounds and polymers - Google Patents

Abstract

The purpose of this invention is to provide a radiosensitive composition and a patterning method that can adequately improve sensitivity, CDU, and development defects when forming resist patterns using next-generation technologies. Additionally, the purpose is to provide a compound and polymer preferably used in the radiosensitive composition. A radiosensitive composition comprises: a polymer (A) containing a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by the following formula (1); and a solvent (E). (In formula (1), ^R1 and ^R2 are, respectively, a hydrogen atom, a halogen atom, or a monovalent organic group with 1 to 5 carbon atoms; ^L1 and ^L2 are, respectively, a single bond or a divalent linker; W is an aromatic ring; ^R3 is a divalent organic group with 1 to 20 carbon atoms; M ⁺ is a monovalent onium cation)

Description

Radiosensitive components, pattern forming methods, compounds and polymers

This invention relates to a radiosensitive composition, a pattern forming method, a compound, and a polymer.

Photolithography using resist compositions is employed in the formation of fine circuits for semiconductor devices. A representative process involves, for example, generating acid by exposing a resist composition film to a dielectric mask pattern and then using the acid as a catalyst to create a difference in the solubility of the polymer relative to an alkaline or organic solvent-based developer in the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

In the aforementioned photolithography technique, short-wavelength radiation such as ArF excimer lasers or a combination of such radiation with liquid immersion lithography is used to advance pattern miniaturization. As a next-generation technology, the aim is to utilize even shorter-wavelength radiation such as electron beams, X-rays, and extreme ultraviolet (EUV).

In the circuit formation of semiconductor devices based on photolithography, various studies have been conducted on photoacid generators, which are one of the main components of the corrosion inhibitor, in order to form finer corrosion inhibitor patterns (e.g., Japanese Patent Application Publication No. 2013-195844). [Prior Art Documents][Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2013-195844

[Problems to be Solved by the Invention] In the next-generation technology described above, the same or better performance of the corrosion inhibitor is required as before in terms of sensitivity, critical dimension uniformity (CDU) as an indicator of aperture uniformity, and development defects.

The purpose of this invention is to provide a radiosensitive composition and a method for patterning that can adequately improve sensitivity, CDU, and development defects when forming anti-corrosion patterns using next-generation technology. Furthermore, the purpose is to provide a compound and polymer preferably used in said radiosensitive composition. [Means of Problem Solving]

The inventors and others have made repeated efforts to solve this problem and have found that the above-mentioned purpose can be achieved by adopting the following structure, thus completing this invention.

That is, in one embodiment, the present invention relates to a radiosensitive composition comprising: a polymer (A) containing a structural unit (I) having an acid-dissociating group and a structural unit (II) derived from a compound represented by formula (1) below; and a solvent (E). [Chemistry 1] (In formula (1), ^R1 and ^R2 are, respectively, a hydrogen atom, a halogen atom, or a monovalent organic group with 1 to 5 carbon atoms; ^L1 and ^L2 are, respectively, a single bond or a divalent linker; W is an aromatic ring; ^R3 is a divalent organic group with 1 to 20 carbon atoms; M ⁺ is a monovalent onium cation)

This radiosensitive composition, due to the presence of polymer (A), can form an anti-corrosion film that exhibits sufficient sensitivity, CDU, and development defects, said polymer (A) comprising a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by said formula (1). For this reason, although not bound by any theory, it is inferred as follows.

It is speculated that the polymer (A) in the radiosensitive composition, due to having a structural unit (II) containing a rigid polycyclic structure, can increase the glass transition temperature (CDU) of the radiosensitive acid-generating polymer containing this structural unit (II). As a result, the diffusion length of the generated acid can be controlled, and the CDU is improved. Furthermore, it is speculated that while the polycyclic structure has low solubility in alkaline developing solutions, because the polymer (A) has a structural unit (I), the acid-dissociating groups of this structural unit (I) dissociate by acid to generate carboxyl groups, thereby improving the solubility in alkaline developing solutions despite containing a polycyclic structure. As a result, the generation of developing defects can be suppressed. It is speculated that the anti-corrosion properties can be enhanced through the combination of these properties.

In another embodiment, the present invention relates to a pattern forming method, comprising: a step of directly or indirectly coating the radiosensitive composition onto a substrate to form an anti-corrosion film; a step of exposing the anti-corrosion film; and a step of developing the exposed anti-corrosion film using a developing solution.

In this pattern forming method, since the radiosensitive component is used to form an anti-corrosion film with excellent sensitivity and CDU and reduced development defects, high-quality anti-corrosion patterns can be formed efficiently.

In another embodiment, this invention relates to a compound represented by the following formula (1'). [Chemistry 2] (In formula (1'), ^R1 and ^R2 are independently hydrogen atoms, halogen atoms, or monovalent organic groups with 1 to 5 carbon atoms, respectively; ^L1 and ^L2 are independently single or divalent linkages, respectively; W is an aromatic ring; ^X1 is an ester bond, amide bond, or sulfonamide bond; ^R5 is a divalent organic group with 1 to 15 carbon atoms; M ⁺ is a monovalent onium cation)

By fabricating a radiosensitive component containing this compound, an anti-corrosion film with excellent sensitivity and CDU and reduced development defects can be formed.

In another embodiment, the present invention relates to a polymer comprising a structural unit (I) having an acid-dissociative group and a structural unit (II) derived from a compound represented by formula (1) below. [Chemical 3] (In formula (1), ^R1 and ^R2 are, respectively, a hydrogen atom, a halogen atom, or a monovalent organic group with 1 to 5 carbon atoms; ^L1 and ^L2 are, respectively, a single bond or a divalent linker; W is an aromatic ring; ^R3 is a divalent organic group with 1 to 20 carbon atoms; M ⁺ is a monovalent onium cation)

By fabricating a radiosensitive composition containing the polymer, an anti-corrosion film with excellent sensitivity and CDU and reduced development defects can be formed.

The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. In addition, combinations of preferred embodiments are also preferred.

The radiosensitive composition of this embodiment (hereinafter also referred to as the "composition") comprises: a polymer (A) including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by formula (1); and a solvent (E). The composition may also contain any other components without prejudice to the effects of the invention.

<Polymer (A)> Polymer (A) is an aggregate of polymer chains comprising a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by formula (1) (hereinafter, this polymer is also referred to as "base polymer (A)"). This radiosensitive composition exhibits excellent CDU due to the presence of structural unit (II) in polymer (A). Furthermore, the presence of structural unit (I) in polymer (A) results in excellent pattern-forming properties, suppressing the generation of development defects.

The structural unit (I) and structural unit (II) may be contained in the same polymer chain, or structural unit (I) may be contained in one polymer chain and structural unit (II) may be contained in another polymer chain. The polymer chain as a whole constituting the base polymer (A) only needs to contain structural unit (I) and structural unit (II). The base polymer (A) may also contain other structural units besides structural unit (I) and structural unit (II). The structural units are described below.

[Structural Unit (I)] Structural unit (I) is a structural unit having an acid-dissociable group. An "acid-dissociable group" refers to a group that substitutes for the hydrogen atom in carboxyl, phenolic hydroxyl, alcoholic hydroxyl, sulfonyl, etc., and is dissociated by the action of an acid. Exposure causes the acid-dissociable group in structural unit (I) to dissociate, producing carboxyl groups, etc., due to the acid generated by a radiosensitive acid generator or a radiosensitive acid-generating polymer. This creates a difference in solubility of the resist film between the exposed and unexposed areas relative to the developing solution, enabling pattern formation. The radiosensitive composition, through the presence of structural unit (I) in the polymer (A), exhibits excellent pattern-forming properties and can suppress the generation of developing defects.

As for structural unit (I), there are no particular limitations as long as it contains an acid-dissociating group. For example, structural units with a tertiary alkyl ester moiety, structural units with a phenolic hydroxyl group whose hydrogen atom is substituted by a tertiary alkyl group, and structural units with acetal bonds are all examples. From the viewpoint of improving the pattern-forming properties of the radiosensitive composition, the structural unit represented by the following formula (2) (hereinafter also referred to as "structural unit (I-1)") is preferred. [Chemistry 4] (In the formula (2), ^RA is a hydrogen atom, a fluorine atom, an organic group with 1 to 3 carbon atoms, or a trifluoromethyl group; ^LA1 is a divalent linker; ^RA1 is a hydrogen atom or a monovalent hydrocarbon with 1 to 20 carbon atoms; ^RA2 and ^RA3 are each independently a monovalent organic group with 1 to 20 carbon atoms or a divalent cyclic group with 3 to 20 carbon atoms formed by combining ^RA2 and ^RA3 together with the carbon atoms they are bonded to; m1 and m2 are each independently 0 or 1; wherein, when m1 is 1, m2 is 1)

Examples of monovalent organic groups with 1 to 20 carbon atoms, represented by ^RA2 and ^RA3 , include: monovalent hydrocarbons with 1 to 20 carbon atoms, groups having divalent heteroatoms between carbon atoms or at the carbon chain end of the hydrocarbon, groups formed by substituting part or all of the hydrogen atoms of the hydrocarbon with a monovalent heteroatomation group, or combinations thereof.

Examples of monovalent hydrocarbons with 1 to 20 carbon atoms in the organic group include: monovalent chain hydrocarbons with 1 to 20 carbon atoms, monovalent alicyclic hydrocarbons with 3 to 20 carbon atoms, and monovalent aromatic hydrocarbons with 6 to 20 carbon atoms.

Examples of monovalent chain hydrocarbons having 1 to 20 carbon atoms include monovalent straight-chain or branched saturated hydrocarbons having 1 to 20 carbon atoms, and monovalent straight-chain or branched unsaturated hydrocarbons having 2 to 20 carbon atoms. Examples of monovalent straight-chain or branched saturated hydrocarbons having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-methylpropyl, 1-methylpropyl, tributyl, n-pentyl, isopentyl, and neopentyl. Examples of monovalent straight-chain or branched unsaturated hydrocarbons having 2 to 40 carbon atoms include alkenyl groups such as vinyl, propynyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

Examples of monovalent alicyclic hydrocarbons with 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbons and monocyclic or polycyclic unsaturated hydrocarbons. Examples of monocyclic saturated hydrocarbons include cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and other cycloalkyl groups. Examples of polycyclic saturated hydrocarbons include norbornel, adamantyl, tricyclodecyl, tetracyclododecyl, and other bridged alicyclic hydrocarbons. Examples of monocyclic unsaturated hydrocarbons include cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, and other monocyclic cycloalkenyl groups. Examples of polycyclic unsaturated hydrocarbons include norbornenyl, tricyclic decenyl, and tetracyclic dodecenyl. Furthermore, bridged alicyclic hydrocarbons refer to polycyclic alicyclic hydrocarbons in which two non-adjacent carbon atoms constituting the alicyclic ring are bonded together by a linker containing one or more carbon atoms.

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

Examples of heteroatoms that form a monovalent or divalent heteroatom-containing base include: oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of halogen atoms include: fluorine, chlorine, bromine, and iodine atoms.

Examples of monovalent heteroatom-containing bases include: hydroxyl, carboxyl, hydrogen thioyl, cyano, nitro, halogen atom, etc.

Examples of divalent heteroatom-containing bases include: -CO-, -C(=O)O-, -CS-, -NH-, -O-, -S-, -SO-, _-SO2- , or combinations thereof.

As divalent cyclic groups with 3 to 20 carbon atoms, formed by the combination of ^RA2 and ^RA3 and together with the bonded carbon atoms, examples can be listed of groups formed by removing two hydrogen atoms from a cyclic structure with 3 to 20 carbon atoms.

The cyclic structure having 3 to 20 carbon atoms can be any of a monocyclic, polycyclic, or combination thereof. Furthermore, the cyclic structure can be any of an alicyclic, aromatic, heterocyclic, or combination thereof. In the case of combinations, it can be a structure formed by chain bonding of the cyclic structure, or it can be a condensed ring structure, bridged ring structure, or spirocyclic structure formed by two or more ring structures. A divalent heteroatom-containing group may be present between the carbon atoms in the carbon-carbon backbone forming the cyclic or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic or chain structure may be substituted by other substituents.

As the alicyclic structure, the structure corresponding to the monovalent alicyclic hydrocarbons with 3 to 20 carbons in ^RA2 and ^RA3 is preferably adopted.

The aromatic ring structure can preferably be the structure corresponding to the monovalent aromatic hydrocarbons with 6 to 20 carbons in ^RA2 and ^RA3 .

Examples of such heterocyclic structures include: aliphatic heterocyclic structures containing oxygen atoms, such as oxadicyclopropane, tetrahydrofuran, tetrahydropyran, dioxadicyclopentane, and dioxane; aliphatic heterocyclic structures containing nitrogen atoms, such as aziridine, pyrrolidine, piperidine, and piperazine; aliphatic heterocyclic structures containing sulfur atoms, such as thiocyclobutane, thiocyclopentane, and thiazide; and morpholine, 1,2-oxadicyclothiocyclopentane, 1,3-oxadicyclothiocyclopentane, and thiocyclopentane. Aliphatic heterocyclic structures containing multiple heteroatoms, such as oxosulfur heterocyclic pentanes; aromatic heterocyclic structures containing oxygen atoms, such as furan, benzofuran, and dibenzofuran; aromatic heterocyclic structures containing nitrogen atoms, such as pyrrole, pyrazole, pyridine, pyrazine, pyrimidine, darazine, and triazine; aromatic heterocyclic structures containing sulfur atoms, such as thiophene; and aromatic heterocyclic structures containing multiple heteroatoms, such as oxazole, isothiazole, and thiazine.

The heterocyclic structure includes lactone structure, cyclic carbonate structure, sulfonyl lactone structure, cyclic acetal structure or combination thereof.

As the chain structure, the monovalent chain hydrocarbons with 1 to 20 carbon atoms in ^RA2 and ^RA3 or the divalent chain hydrocarbons obtained by removing one hydrogen atom from the monovalent chain hydrocarbons are preferably adopted.

As a divalent heteroatom-containing base, the divalent heteroatom-containing base shown in the monovalent organic bases with carbon numbers of 1 to 20 represented by ^RA2 and ^RA3 is preferably adopted.

Substituents that replace part or all of the hydrogen atoms on the carbon atoms of the cyclic or chain structure include, for example, halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; hydroxyl; carboxyl; cyano; nitro; alkyl; alkoxy; alkoxycarbonyl; alkoxycarbonyloxy; acetyl; acetoxy or groups formed by replacing the hydrogen atoms of these groups with halogen atoms (T).

The alkyl group serving as the substituent (T) may include, for example, methyl, ethyl, propyl, and other linear or branched alkyl groups having 1 to 8 carbon atoms. The alkoxy group may include, for example, methoxy, ethoxy, propoxy, and other linear or branched alkoxy groups having 1 to 8 carbon atoms. The alkoxycarbonyl group may include, for example, methoxycarbonyl, ethoxycarbonyl, and other alkoxy groups having 1 to 6 carbon atoms. The alkoxycarbonyloxy group may include, for example, methoxycarbonyloxy, butoxycarbonyloxy, and diamond methyloxycarbonyloxy, and other chain-like or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms. The amide group may include, for example, acetyl, propionic, benzoyl, and acrylyl, and other aliphatic or aromatic amide groups having 2 to 12 carbon atoms. Examples of acetylated ...

As for the ^RA2 and ^RA3 , they are preferably monovalent chain hydrocarbons having 1 to 10 carbon atoms, or divalent alicyclic groups having 3 to 20 carbon atoms formed by the combination of ^RA2 and ^RA3 with the bonded carbon atoms, more preferably monovalent straight chain hydrocarbons having 1 to 10 carbon atoms or divalent alicyclic groups having 5 to 10 carbon atoms, and even more preferably methyl, ethyl, isopropyl, tributyl, cyclopentanediyl, or cyclohexaneediyl.

The organic group representing 1 to 3 carbon atoms as ^RA is preferably a monovalent organic group representing 1 to 20 carbon atoms as ^RA2 and ^RA3 . Among these, the ^RA is preferably a hydrogen atom, a methyl group, or a methoxymethyl group.

Examples of divalent linking groups represented by ^LA1 include: alkyldiyl, cycloalkyldiyl, alkenyl, aryl, groups containing -CO-, -CS-, -O-, -S-, _-SO2- , -NR'-, or combinations of two or more of these between the carbon-carbon bonds of these groups, or groups formed by combining these groups. R' is a hydrogen atom or a monovalent hydrocarbon having 1 to 10 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted, for example, by substituents. As substituents, those that substitute some or all of the hydrogen atoms on the carbon atoms of the cyclic or chain structure are preferably used. Alternatively, the divalent linker represented by ^LA1 can preferably be a divalent group obtained by removing two hydrogen atoms from the heterocyclic structure.

Examples of alkyldiyl groups include methanediyl, ethanediyl, 1,3-propanediyl, and 2,2-propanediyl, which have 1 to 8 carbon atoms.

Examples of cycloalkyl diols include monocyclic cycloalkyl diols such as cyclopentanediol and cyclohexanediol; and polycyclic cycloalkyl diols such as norbornenediol and adamantanediol.

Examples of the alkenyl group include ethylenediol, propylenediol, and butenyldiol. Preferably, the alkenyl group has 2 to 6 carbon atoms.

Examples of aryl diols include phenyldiol, toluenediol, and naphthyldiol. Preferably, the aryl diol has 6 to 15 carbon atoms, and more preferably, it is phenyldiol.

The ^LA1 is preferably an aryl group with 6 to 15 carbon atoms, a divalent group formed by removing two hydrogen atoms from a heterocyclic structure, and more preferably a phenyldiyl or furandiyl group.

The monovalent hydrocarbon with 1 to 20 carbon atoms represented by ^RA1 is preferably one of the monovalent hydrocarbons with 1 to 20 carbon atoms in ^RA2 and ^RA3 . ^RA1 is preferably a monovalent chain hydrocarbon with 1 to 10 carbon atoms, a monovalent aromatic hydrocarbon with 6 to 20 carbon atoms, and more preferably a methyl, ethyl, substituted or unsubstituted phenyl group.

The value of m1 is preferably 0.

From a sensitivity perspective, the structural unit (I) preferably has an iodine group, and more preferably contains an iodine-containing aromatic ring structure. The iodine-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are substituted with iodine groups.

As for the aromatic ring in the iodine-containing aromatic ring structure, there is no particular limitation as long as it is an aromatic ring structure. Examples of aromatic rings include aromatic hydrocarbon rings, heteroaromatic rings, or combinations thereof. Preferably, the structure corresponding to the monovalent aromatic hydrocarbon group with 6 to 20 carbon atoms in ^RA2 and ^RA3 is adopted as the aromatic hydrocarbon ring. Preferably, the aromatic heterocyclic structure in the heterocyclic structure is adopted as the heterocyclic structure. Among these, a benzene ring is preferred as the aromatic ring.

The number of iodine atoms in the iodine-containing aromatic ring structure is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 3.

As a structural unit (I), for example, the structural units represented by the following equations (1-1) to (1-14) (hereinafter also referred to as "structural units (I-1) to structural units (I-14)") can be listed.

[Chemistry 5]

[Chemistry 6]

In equations (1-1) to (1-14), ^RA , ^RA1 to ^RA3 have the same meaning as in equation (2). X is a substituent, preferably the substituent (T). i and j are independent integers from 1 to 4. k and l are 0 or 1. a1 is an integer from 0 to 3. When a1 is 2 or more, multiple Xs may be the same or different. a4 is an integer from 1 to 3.

As i and j, 1 or 2 is preferred. As k and l, 1 is preferred. As ^RA1 , methyl, ethyl, phenyl, or iodophenyl is preferred. As ^RA2 and ^RA3 , methyl, ethyl, or isopropyl is preferred. As X, hydroxyl, iodine atom, or alkyl is preferred.

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

[Chemistry 7]

In formulas (1f) to (2f), R ^αf is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ^{R βf} is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. h1 is an integer from 1 to 4.

R ^βf is preferably a hydrogen atom, a methyl atom, or an ethyl atom. h1 is preferably 1 or 2.

Specific examples of structural units (I) are shown below, but are not limited to those.

[Chemistry 8] (In the formula, R ^A has the same meaning as the above formula (2))

[Chemistry 9] (In the formula, R ^A has the same meaning as the above formula (2))

The basic polymer (A) may contain one or more structural units (I).

The lower limit of the content ratio of the structural unit (I) (the aggregate content ratio in the case of multiple components) relative to all structural units constituting the base polymer (A) is preferably 10 mol%, more preferably 15 mol%, and even more preferably 20 mol%. The upper limit of the content ratio is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content ratio of the structural unit (I) within the aforementioned range, the pattern-forming property of the radiosensitive composition can be further improved, and the generation of development defects can be suppressed.

[Structural Unit (II)] Structural unit (II) is a structural unit derived from the compound represented by formula (1) below, and is a structural unit of an acid-generating structure comprising an acid that generates a dissociative group of the acid upon exposure. The polymer (A), by comprising structural unit (II), functions as a radiosensitive acid-generating polymer. [Chem. 10] (In formula (1), ^R1 and ^R2 are, respectively, a hydrogen atom, a halogen atom, or a monovalent organic group with 1 to 5 carbon atoms; ^L1 and ^L2 are, respectively, a single bond or a divalent linker; W is an aromatic ring; ^R3 is a divalent organic group with 1 to 20 carbon atoms; M ⁺ is a monovalent onium cation)

As the monovalent organic groups with carbon numbers of 1 to 5 represented by ^R1 and ^R2 , the corresponding carbon number of the monovalent organic groups with carbon numbers of 1 to 20 represented by ^RA2 and ^RA3 in formula (2) can be preferred.

As the divalent linker represented by ^L1 and ^L2 , the divalent linker represented by ^LA1 in formula (2) is preferably adopted. As ^L1 and ^L2 , they are preferably single bonds, alkyl groups with 1 to 5 carbon atoms, -O-, -S- or ^-NR11- ( ^R11 is a hydrogen atom or a monovalent hydrocarbon), more preferably single bonds, -O-, -S-, and even more preferably single bonds. As the monovalent hydrocarbon represented by ^R11 , the monovalent hydrocarbons with 1 to 20 carbon atoms in ^RA2 and ^RA3 in formula (2) are preferably adopted.

The aromatic ring represented by W is preferably an iodine-containing aromatic ring structure. Among these, benzene ring, naphthalene ring, anthracene ring or furan ring are preferred, benzene ring or naphthalene ring are more preferred, and naphthalene ring is even more preferred.

As a divalent organic group with 1 to 20 carbon atoms represented by R ³ , it is preferable to use a group obtained by removing one hydrogen atom from the monovalent organic groups with 1 to 20 carbon atoms represented by ^RA2 and ^RA3 in formula (2).

As the monovalent onium cation represented by M ⁺ , examples include radiosensitive onium cations. Examples of radiosensitive onium cations include strontium cations, tetrahydrothiophene onium cations, and monium cations. Among these, strontium cations or monium cations are preferred, and strontium cations are even more preferred.

From a sensitivity perspective, the onium cation preferably has an iodine group, and more preferably has an aromatic ring structure containing the iodine group.

The onium cation preferably has a fluorine group, and more preferably has a fluorine-containing aromatic ring structure. This increases radiation absorption efficiency, thereby improving sensitivity. The fluorine-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with fluorine groups. The aromatic ring in the fluorine-containing aromatic ring structure is preferably the aromatic ring in the iodine-containing aromatic ring structure. Among these, a benzene ring is preferred as the aromatic ring.

The number of fluorine atoms in the fluorine-containing aromatic ring structure is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 3.

The strontium cation is preferably represented by the following formula (Q-1).

[Chemistry 11]

In equation (Q-1), Ra ₁ to Ra ₃ each independently represent a substituent. n11 represents an integer from 0 to 5. When n11 is 2 or more, multiple Ra _1s can be the same or different. n12 represents an integer from 0 to 5. When n12 is 2 or more, multiple Ra _2s can be the same or different. n13 represents an integer from 0 to 5. When n13 is 2 or more, multiple Ra _3s can be the same or different. _{Ra 1} and Ra ₂ can be linked together to form a ring. When n11 is 2 or more, multiple Ra _1s can be linked together to form a ring. When n12 is 2 or more, multiple Ra _2s can be linked together to form a ring.

The substituents represented by Ra ₁ , Ra ₂ and Ra ₃ are preferably alkyl, cycloalkyl, alkoxy, cycloalkyloxy, alkoxycarbonyl, alkylsulfonyl, hydroxyl, cyano, halogen atom, or halogenated hydrocarbon.

The alkyl groups of Ra ₁ , Ra ₂ , and Ra ₃ can be either straight-chain or branched-chain alkyl groups. Preferably, the monovalent straight-chain or branched-chain saturated hydrocarbons of formula (2) having 1 to 20 carbon atoms in Ra ² and Ra ³ are used as alkyl groups. Among these, methyl, ethyl, n-butyl, and tributyl are particularly preferred.

As cycloalkyl groups of Ra ₁ , Ra ₂ , and Ra ₃ , monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups with 3 to 20 carbon atoms) can be listed, and the monocyclic saturated hydrocarbons in Ra ² and Ra ³ of formula (2) are preferably used. Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl are particularly preferred.

The alkyl portion of the alkoxy group of Ra ₁ , Ra ₂ , and Ra ₃ can be exemplified by those previously listed as alkyl groups of Ra ₁ , Ra ₂ , and Ra _3. The alkoxy group is particularly preferably methoxy, ethoxy, n-propoxy, and n-butoxy.

The cycloalkyl portion of the cycloalkyloxy group of Ra ₁ , Ra ₂ and Ra ₃ can be exemplified by those previously listed as cycloalkyl groups of Ra ₁ , Ra ₂ and Ra _3. Cycloalkyloxy groups are particularly preferred as cyclopentyloxy and cyclohexyloxy groups.

The alkoxy moiety of the alkoxy carbonyl group in Ra ₁ , Ra ₂ , and Ra ₃ can be exemplified by those previously listed as alkoxy groups in Ra ₁ , Ra ₂ , and Ra _3. Preferably, the alkoxy carbonyl group is methoxy carbonyl, ethoxy carbonyl, or n-butoxy carbonyl.

The alkyl portion of the alkyl sulfonyl group in Ra ₁ , Ra ₂ , and Ra ₃ can be exemplified by those previously listed as alkyl groups _in Ra ₁ , Ra ₂ , and Ra _3. Similarly, the cycloalkyl portion of the cycloalkyl sulfonyl group in Ra ₁ , Ra ₂ , and Ra ₃ can be exemplified by those previously listed as cycloalkyl groups in Ra 1, Ra ₂ , and Ra _3. Preferably, these alkyl sulfonyl or cycloalkyl sulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl.

The groups of Ra ₁ , Ra ₂ , and Ra ₃ may also have substituents. Examples of such substituents include: halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkoxy group, cycloalkyloxy group, alkoxyalkyl group, cycloalkyloxyalkyl group, alkoxycarbonyl group, cycloalkyloxycarbonyl group, alkoxycarbonyloxy group, and cycloalkyloxycarbonyloxy group.

As halogen atoms for Ra ₁ , Ra ₂ and Ra ₃ , fluorine atoms, chlorine atoms, bromine atoms and iodine atoms can be listed, with fluorine atoms and iodine atoms being preferred.

The halogenated hydrocarbons of _Ra1 , _Ra2 , and _Ra3 are preferably halogenated alkyl groups. Examples of alkyl and halogen atoms constituting the halogenated alkyl groups are as described above. Among these, fluorinated alkyl groups are preferred, and _CF3 is even more preferred.

As described above, Ra ₁ and Ra ₂ can be linked together to form a ring (i.e., a heterocyclic ring containing sulfur atoms). In this case, it is preferable that Ra ₁ and Ra ₂ are bonded together to form a single bond or a divalent linkage. Examples of divalent linkages include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO _2- , alkylene, cycloalkylene, alkenylene, or combinations of two or more of these, preferably with a total carbon number of 20 or less. When Ra ₁ and Ra ₂ are linked together to form a ring, Ra 1 and Ra 2 are preferably bonded together to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO _2- , or a single bond. Preferably, -O-, -S-, or single bonds are formed, and most preferably single bonds are formed. Furthermore, when n11 is 2 or more, multiple Ra _1s can be interconnected to form a ring, and when n12 is 2 or more, multiple Ra _2s can be interconnected to form a ring. As an example, one can illustrate this by having two Ra _1s interconnected and forming a naphthalene ring together with the bonded benzene rings.

Ra ₃ is preferably a fluorine atom or a group having one or more fluorine atoms. Examples of groups having fluorine atoms include alkyl, cycloalkyl, alkoxy, cycloalkyloxy, alkoxycarbonyl and alkylsulfonyl groups of Ra ₁ and Ra ₂ that are substituted with fluorine atoms. Fluorinated alkyl groups are preferably listed, _and more preferably _{CF3 , C2F5} , _C3F7 , _C4F9 , _C5F11 , _{C6F13 , C7F15 , C8F17 , CH2CF3 , CH2CH2CF3} , _{CH2C2F5 , CH2CH2C2F5 , CH2C3F7 , CH2CH2C3F7 , CH2C4F9 , and CH2CH2C4F9 ,} with _{CF3 being} particularly preferred _{. Ra3 is} preferably _{a fluorine} atom _{or CF3 , and} more preferably _{a fluorine atom .}

n11, n12 and n13 are each preferably integers from 0 to 3, and more preferably integers from 0 to 2.

Specific examples of onium cations represented by such formula (Q-1) can be listed below.

[Chemistry 12] (In the formula, tBu represents tertiary butyl, and Me represents methyl)

[Chemistry 13]

[Chemistry 14] (In the formula, Me represents methyl)

[Chemistry 15]

[Chemistry 16]

[Chemistry 17] (In the formula, Me represents methyl)

[Chemistry 18]

[Chemistry 19] (In the formula, Me represents methyl)

[Chemistry 20]

Specific examples of the aforementioned cations can be listed below. [Chemistry 21]

From a sensitivity perspective, the structural unit (II) preferably has an iodine group, and more preferably comprises an aromatic ring structure containing an iodine group. An iodine-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are substituted with an iodine group. The iodine-containing aromatic ring structure shown in the structural unit (I) is preferably adopted as the iodine-containing aromatic ring structure.

The structural unit (II) is preferably the structural unit represented by the following formula (1-1). [Chemistry 22] (In formula (1-1), X is an ester bond, ether bond, amide bond or sulfonamide bond; ^{R4 is} a divalent organic group with 1 to 10 carbon atoms; n is 0 or 1; ^Rf1 and ^Rf2 are independently hydrogen atoms, halogen atoms, hydroxyl groups, nitro groups, thiols, amino groups or monovalent organic groups with 1 to 20 carbon atoms; when there are multiple ^Rf1 and ^Rf2 , the multiple ^Rf1 and ^Rf2 are the same or different from each other; wherein, ^Rf1 or ^Rf2 on the carbon atom at the α or β position of the sulfur atom ^of _-SO3- is a fluorine atom or a fluorinated hydrocarbon group; m is an integer from 0 to 5; wherein, 1 ≦ m + n; ^R1 , ^R2 , ^L1 , ^L2 , W, M ⁺ have the same meaning as in formula (1))

As X, it is preferably an ester bond or an ether bond, more preferably an ester bond.

As a divalent organic group with 1 to 10 carbons represented by R ⁴ , it is preferable to use a group obtained by removing one hydrogen atom from the corresponding carbon number of the monovalent organic groups with 1 to 20 carbons represented by ^RA2 and ^RA3 in formula (2).

As the monovalent organic groups with carbon numbers of 1 to 20 represented by R ^f1 and R ^f2 , the monovalent organic groups with carbon numbers of 1 to 20 represented by ^RA2 and ^RA3 in formula (2) can be preferred.

The following structures can be listed as anionic structures of the compounds represented by the formula (1).

[Chemistry 23]

[Chemistry 24]

The compound represented by formula (1) can be obtained by suitably combining the anion with the onium cation. As a specific example, although there is no particular limitation, the structure of the following formula can be given as an example.

[Chemistry 25]

[Chemistry 26]

[Chemistry 27]

[Chemistry 28]

The base polymer (A) may contain one or more structural units (II).

The lower limit of the content ratio of the structural unit (II) (the aggregate content ratio in the case of multiple components) relative to all structural units constituting the base polymer (A) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. The upper limit of the content ratio is preferably 50 mol%, more preferably 40 mol%, and even more preferably 30 mol%. By setting the content ratio of structural unit (II) within the above range, the CDU can be increased.

(Structural unit (III)) Polymer (A) preferably contains structural unit (III) having phenolic hydroxyl groups. By including structural unit (III) in polymer (A), the solubility in the developing solution can be adjusted more appropriately, and as a result, the sensitivity of the radiosensitive composition can be further improved. In addition, when using radiation irradiated in the exposure step of a pattern formation method using KrF excimer laser, EUV, electron beam, etc. as resist, structural unit (III) helps to improve etching resistance and increase the difference in developing solution solubility between the exposed and unexposed areas (solution contrast). In particular, it can be preferably applied to pattern formation using exposure to radiation with wavelengths below 50 nm, such as electron beam or EUV. Structural unit (III) is preferably represented by the following formula (4).

[Chemistry 29] (In the formula (4), ^Rβ is a hydrogen atom, a fluorine atom, a methyl or trifluoromethyl atom; ^LCA is a single bond, -COO- ^* or -O-; * is a bond on the aromatic ring side; ^R102 is a halogen atom, a cyano, a nitro, an alkyl, an alkoxycarbonyl, a acetyl or aceoxy; when there are multiple ^R102 , the multiple ^R102 are the same or different from each other; _n3 is an integer from 0 to 2, _m3 is an integer from 1 to 8, _m5 is an integer from 0 to 8; wherein, 1≦ _m3 + _m5 ≦ _2n3 +5)

As for R ^β , from the viewpoint of providing copolymerization of the monomer of structural unit (III), it is preferably a hydrogen atom or a methyl group.

For ^LCA , a single key or -COO- ^* is preferred.

The halogen atom, alkyl group, alkoxycarbonyloxy group, amide group, or amide group in R ¹⁰² may preferably be one of the groups listed as the substituent (T). The halogen atom in R ¹⁰² is preferably an iodine atom.

As stated in n ₃ , it is more preferably 0 or 1, and even more preferably 0.

The value of _m3 is preferably an integer from 1 to 3, and more preferably 1 or 2.

The value of _m5 is preferably an integer from 0 to 3, and more preferably an integer from 0 to 2.

As the structural unit (III), it is preferably the structural unit represented by the following formula.

[Chemistry 30] (In the formula, ^Rβ is the same as in formula (4))

In obtaining structural unit (III), it is preferable to polymerize with the phenolic hydroxyl group protected by a basal-dissociating group (e.g., acetyl) during polymerization, followed by hydrolysis to deprotect the hydroxyl group, thereby obtaining structural unit (III). Alternatively, the phenolic hydroxyl group can be polymerized without protecting the monomer providing structural unit (III).

The base polymer (A) may contain one or more structural units (III).

When the base polymer contains structural unit (III), the lower limit of the content ratio of structural unit (III) (the total content ratio in the case of multiple structural units) relative to all structural units constituting the base polymer is preferably 15 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of the content ratio is preferably 50 mol%, more preferably 45 mol%, and even more preferably 40 mol%. By setting the content ratio of structural unit (III) within the aforementioned range, the radiosensitive composition can achieve further improvement in sensitivity and CDU.

[Structural Unit (IV)] The structural unit (IV) is a structural unit comprising at least one of the group consisting of lactone structures, cyclic carbonate structures, sulopentalide structures, and cyclic sulfone structures. By having more structural units (IV), the solubility of the base polymer (A) in the developing solution can be adjusted, resulting in improved lithography properties such as resolution in the radiosensitive composition. Furthermore, the adhesion between the resist pattern formed from the base polymer (A) and the substrate can be improved.

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

[Chemistry 31]

In the formula, ^RL1 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ^RL2 to ^RL5 are independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, a dimethylamino group, or -COOR ^L6 . ^RL6 is a monovalent hydrocarbon having 1 to 20 carbon atoms. ^RL4 and ^RL5 can also be divalent alicyclic hydrocarbons having 3 to 8 carbon atoms, bonded together with each other. ^L2 is a single bond or a divalent linker. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

As a divalent alicyclic hydrocarbon with 3 to 8 carbon atoms formed by the combination of ^RL4 and ^RL5 and together with the bonded carbon atoms, examples can be listed of groups formed by removing one hydrogen atom from the corresponding carbon number of monovalent alicyclic hydrocarbons with 3 to 20 carbon atoms in ^RA2 and ^RA3 of formula (2). One or more hydrogen atoms on the alicyclic hydrocarbon can also be replaced by hydroxyl groups.

As the monovalent hydrocarbons with 1 to 20 carbons represented by ^RL6 , the monovalent hydrocarbons with 1 to 20 carbons in ^RA2 and ^RA3 of formula (2) can be preferably adopted.

Examples of divalent linkers represented by ^L2 include: divalent linear or branched hydrocarbons having 1 to 10 carbon atoms, divalent alicyclic hydrocarbons having 4 to 12 carbon atoms, or hydrocarbons containing one or more of these hydrocarbons and at least one of the groups -CO-, -O-, -NH-, and -S-.

As a divalent linear or branched hydrocarbon with 1 to 10 carbon atoms in ^L2 , it is preferable to use a group obtained by removing one hydrogen atom from a monovalent linear hydrocarbon with 1 to 20 carbon atoms in ^RA2 and ^RA3 of formula (2).

As a divalent alicyclic hydrocarbon with 4 to 12 carbons in L ² , it is preferable to use a group obtained by removing one hydrogen atom from the corresponding carbon number of the monovalent alicyclic hydrocarbon with 3 to 20 carbons in ^RA2 and ^RA3 of formula (2).

As structural units (IVs), these are preferably structural units containing lactone structures, more preferably structural units containing norbornene lactone structures, and even more preferably structural units derived from norbornene lactone-based esters of (meth)acrylate.

The base polymer (A) may contain one or more structural units (IVs).

When the base polymer (A) contains the structural unit (IV), the lower limit of the content ratio of the structural unit (IV) (the aggregate content ratio in the case of multiple structural units) relative to all structural units constituting the base polymer (A) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. The upper limit of the content ratio is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content ratio of the structural unit (IV) within the aforementioned range, the radiosensitive composition can further improve lithography properties such as resolution and the adhesion between the formed resist pattern and the substrate.

[Structural Unit (V)] The base polymer (A) may optionally have other structural units besides the aforementioned structural unit. Examples of such other structural units include structural units (V) containing polar groups (excluding those equivalent to structural unit (III)). By having more structural units (V), the solubility of the base polymer (A) in the developing solution can be adjusted, resulting in improved photolithography properties such as resolution of the radiosensitive composition, which is therefore preferable. Examples of such polar groups include hydroxyl, carboxyl, cyano, nitro, sulfonamide, etc. Among these, hydroxyl and carboxyl are preferred, and hydroxyl is even more preferred.

As a structural unit (V), for example, structural units represented by the following formulas can be listed.

[Chemistry 32]

[Chemistry 33]

In the formula, R and ^K are hydrogen atoms, fluorine atoms, methyl groups, or trifluoromethyl groups.

When the base polymer (A) contains the structural unit (V), the lower limit of the content ratio of the structural unit (V) relative to all structural units constituting the base polymer (A) (the aggregate content ratio in the case of multiple structural units) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. Furthermore, the upper limit of the content ratio is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content ratio of the structural unit (V) within the aforementioned range, the lithography properties such as resolution of the radiosensitive composition can be further improved, which is therefore preferable.

(Method for synthesizing basic polymer (A)) Basic polymer (A) can be synthesized, for example, by using free radical polymerization initiators, etc., to polymerize monomers that provide each structural unit in a suitable solvent.

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

Examples of solvents used in the polymerization include: alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decahydronaphthalene, and norbornene; aromatics such as benzene, toluene, xylene, ethylbenzene, and cumene; and chlorobutanes, bromohexanes, dichloroethanes, and hexamethylene dibromide. The solvents used in the polymerization process include halogenated hydrocarbons such as dibromide and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate; lactones such as γ-butyrolactone and δ-valerolactone; ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; and alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-methoxy-2-propanol, and 4-methyl-2-pentanol. These solvents can be used alone or in combination.

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

The molecular weight of the base polymer (A) is not particularly limited, but as a lower limit for the converted weight average molecular weight (Mw) of polystyrene obtained by gel permeation chromatography (GPC), it is preferably 2,000, more preferably 3,000, further preferably 4,000, and particularly preferably 5,000. As an upper limit for Mw, it is preferably 30,000, more preferably 20,000, further preferably 12,000, and particularly preferably 10,000. By setting the Mw of the base polymer within the aforementioned range, the obtained anti-corrosion film can be endowed with good development properties.

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

The Mw and Mn values of the polymers in this specification are values determined using gel osmosis chromatography (GPC) under the conditions described in the embodiments.

The proportion of the base polymer (A) relative to the total solid content of the radiosensitive component is preferably 60% by mass or more, more preferably 65% by mass or more, and even more preferably 70% by mass or more.

The radiosensitive composition preferably includes, in addition to the polymer (A), a radiosensitive acid generator (C) or an acid diffusion control agent (D).

<Radiosensitive acid generator (C)> As the radiosensitive acid generator (C), examples include onium salt compounds (C) represented by the following formula (C-1). The radiosensitive acid generator (C) has an onium salt structure that exists alone as a low-molecular-weight compound (free from the polymer) and is different from the polymer (A) having the radiosensitive acid-generating structure (radiosensitive acid-generating polymer). [Chem. 34] (In formula (C-1), ^R40 is a monovalent organic group with 1 to 40 carbon atoms; ^Rf21 and ^Rf22 are independently hydrogen atoms, fluorine atoms, or monovalent fluorinated hydrocarbons, respectively; when multiple ^Rf21 and ^Rf22 exist, the multiple ^Rf21 and ^Rf22 are the same or different; n is an integer from 0 to 4; _Z2 ⁺ is a radiosensitive onium cation.)

As a monovalent organic group with carbon number 1 to 40 represented by R ⁴⁰ , examples can be listed of groups formed by expanding the monovalent organic groups with carbon number 1 to 20 represented by ^RA2 and ^RA3 in the above formula (2) to carbon number 1 to 40.

As the monovalent fluorinated hydrocarbons represented by ^Rf21 and ^Rf22 , examples include groups formed by substituting some or all of the hydrogen atoms of monovalent hydrocarbons having 1 to 40 carbon atoms with fluorine atoms. As the monovalent hydrocarbons having 1 to 40 carbon atoms, examples include groups formed by expanding the monovalent hydrocarbons having 1 to 20 carbon atoms in ^RA2 and ^RA3 of formula (2) to have 1 to 40 carbon atoms.

As specific examples of anions of onium salt compounds (C), although not limited, structures such as those described below can be listed.

[Chemistry 35]

[Chemistry 36]

[Chemistry 37]

[Chemistry 38]

[Chemistry 39]

[Chemistry 40]

As a specific example of a radiosensitive onium cation of an onium salt compound (C), although not limited, the monovalent onium cation represented by M ⁺ in the above formula (2) is preferably used.

As an onium salt compound (C), structures formed by any combination of the anion and the radiosensitive onium cation can be listed.

When the radiosensitive composition includes a radiosensitive acid generator (C), the lower limit of the content of the radiosensitive acid generator (C) (total content in the case of multiple generators) relative to 100 parts by weight of polymer (A) is preferably 0.5 parts by weight, more preferably 1 part by weight, and even more preferably 3 parts by weight. The upper limit of the content is preferably 100 parts by weight, more preferably 40 parts by weight, and even more preferably 30 parts by weight.

<Acid diffusion control agent (D)> The acid diffusion control agent (D) is not particularly limited, but preferably a bellium salt compound (D1) that produces an acid with a higher pKa than that produced by the radiosensitive acid generator, etc., by irradiation with radiation. The acid produced by the bellium salt compound (D1) is a weak acid that will not induce the dissociation of the acid dissociative groups under conditions that would cause the dissociation of the acid dissociative groups in the polymer. Furthermore, in this specification, the term "dissociation" of the acid dissociative groups refers to dissociation that occurs during baking after exposure at 110°C for 60 seconds.

The onium salt compound (D1) is preferably represented by formulas (8-1) to (8-4) below. [Chemical 41]

In formulas (8-1) and (8-2), J ⁺ represents a strontium cation, and U ⁺ represents a zinc cation. ^E- and ^Q- in formulas (8-1) and (8-2) are preferably selected independently from at least one of the groups consisting of ^{R8SO3- ,} _R8COO- ^, and ( ^R8SO2 ) _N- ^, more preferably ^{R8COO- .} Additionally, examples can be given of compounds containing both strontium cations and anions within the same molecule, as represented by formula (8-3) or compounds containing ^both zinc cations and anions within the same molecule, as represented by formula (8-4). In equations (8-3) and (8-4), J' ⁺ is a monovalent group having an strontium cation structure, and U' ⁺ is a monovalent group having a zinc cation structure. ^E'- and Q'- ⁱⁿ equations ( _8-3 ⁾ and (8-4) are preferably selected independently from at least one of the groups consisting of ^{-R81SO3- , -R81COO-} , _and ^{-R81SO2N -} _SO2R8 , more preferably ^-R81COO- . ^{R8 is} a monovalent organic group, and ^R81 is a single ^- bonded or divalent organic group.

As the monovalent organic group, a monovalent organic group with 1 to 40 carbons represented by R ⁴⁰ in the formula (C-1) is preferably adopted.

As the divalent organic group, it is preferable to use a group obtained by removing one hydrogen atom from a monovalent organic group with carbon numbers 1 to 40 represented by R ⁴⁰ in the formula (C-1).

As the onium salt compound (D1), examples of compounds represented by the following formulas can be listed.

[Chemistry 42]

[Chemistry 43]

[Chemistry 44]

The onium salt compound (D1) can also be synthesized by known methods, particularly salt exchange reactions.

These acid diffusion control agents (D) can be used alone or in combination of two or more. The lower limit of the content of the acid diffusion control agent (D) (total content in the case of multiple agents) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, relative to the total amount (100 mol%) of the radiosensitive acid generator and the radiosensitive acid-generating polymer contained in the composition. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%.

<Other Polymers> The radiosensitive composition of this embodiment may also include polymers with a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as "high-fluorine polymers") as other polymers. In the case where the radiosensitive composition contains high-fluorine polymers, they may be more concentrated on the surface of the anti-corrosion film relative to the base polymer. As a result, the water repellency of the surface of the anti-corrosion film during immersion exposure can be improved, or the surface modification or distribution of the intrafilm composition of the anti-corrosion film during EUV exposure can be achieved.

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

[Chemistry 45]

In formula (5), R ⁷³ is a hydrogen atom, a methyl group, or a trifluoromethyl group. ^GL is a single bond, an alkyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, -OCO-, -SO _2ONH- , -CONH-, -OCONH-, or a combination thereof. ^{R 74} is a monovalent fluorinated chain hydrocarbon having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon having 3 to 20 carbon atoms.

As for R ^{7 3} , from the viewpoint of providing copolymerization of the monomer of structural unit (VII), it is preferably hydrogen atom and methyl group, more preferably methyl group.

As for the ^GL , from the viewpoint of providing copolymerization of the monomer of the structural unit (VII), it is preferably a combination of at least one of the single bond, -COO-, -COO- and -OCO- with an alkyl diene having 1 to 5 carbon atoms, and more preferably -COO-.

As the monovalent fluorinated chain hydrocarbons with 1 to 20 carbon atoms represented by R ^{7 4} , examples include those formed by substituting some or all of the hydrogen atoms of straight or branched chain alkyl groups with 1 to 20 carbon atoms with fluorine atoms.

As for the monovalent fluorinated alicyclic hydrocarbons with 3 to 20 carbon atoms represented by R ^{7 4} , examples can be listed of monocyclic or polycyclic hydrocarbons with 3 to 20 carbon atoms in which some or all of the hydrogen atoms are replaced by fluorine atoms.

As R ^{7 4} , it is preferably a fluorinated chain hydrocarbon, and more preferably a fluorinated alkyl group.

When the high-fluorine polymer has structural unit (VII), the lower limit of the content ratio of structural unit (VII) relative to all structural units constituting the high-fluorine polymer is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%. Furthermore, the upper limit of the content ratio is preferably 90 mol%, more preferably 85 mol%, and even more preferably 80 mol%. By setting the content ratio of structural unit (VII) within the aforementioned range, the mass content of fluorine atoms in the high-fluorine polymer can be more appropriately adjusted, further promoting the biased presence on the surface of the anti-corrosion film. As a result, the water repellency of the anti-corrosion film during immersion exposure can be further improved.

High-fluorine polymers can also be combined with or replace structural unit (VII) to have structural units containing fluorine atoms as represented by the following formula (f-2) (hereinafter also referred to as structural unit (VIII)). By having structural unit (f-2) in high-fluorine polymers, the solubility in alkaline developing solutions is improved, and the generation of developing defects can be suppressed.

[Chemistry 46]

Structural unit (VIII) is broadly classified into two cases: one with an alkali-soluble group (x) and the other with a group (y) that dissociates under the influence of alkali and increases solubility in alkaline developing solutions (hereinafter also referred to as "alkali-dissociating group"). Both (x) and (y) are common to each other. In formula (f-2), RC is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. RD is a single-bonded (s+1) valent hydrocarbon with 1 to 20 carbon atoms, with an oxygen atom, a sulfur atom, -NR dd- , a carbonyl group, -COO-, -OCO-, or -CONH- bonded to the RE side of the hydrocarbon, or a structure in which a portion of the hydrogen atom in the hydrocarbon is replaced by an organic group having heteroatoms. R dd  represents a hydrogen atom or a monovalent hydrocarbon with 1 to 10 carbon atoms. s represents an integer from 1 to 3.

When structural unit (VIII) has an (x) alkali-soluble group, ^RF is a hydrogen atom, and ^A1 is an oxygen atom, -COO-*, or _-SO2O- *. * indicates the site bonded to ^RF . ^W1 is a single bond, an hydrocarbon with 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon. When ^A1 is an oxygen atom, ^W1 is a fluorinated hydrocarbon with a fluorine atom or fluoroalkyl group on the carbon atom bonded to ^A1 . ^RE is a single bond or a divalent organic group with 1 to 20 carbon atoms. When s is 2 or 3, multiple ^RE , ^W1 , ^A1 , and ^RF may be the same or different. By having a (x)-base-soluble group in structural unit (VIII), the affinity for alkaline developing solutions can be improved, and developing defects can be suppressed. As a structural unit (VIII) with a (x)-base-soluble group, it is particularly preferred that ^A1 is an oxygen atom and ^W1 is 1,1,1,3,3,3-hexafluoro-2,2-methanediyl.

When structural unit (VIII) has a (y) basal dissociative group, ^RF is a monovalent organic group with 1 to 30 carbon atoms, and ^A1 is an oxygen atom, -NR ^aa- , -COO-*, -OCO-*, or _-SO₂O- *. ^Raa is a hydrogen atom or a monovalent hydrocarbon with 1 to 10 carbon atoms. * indicates the site bonded to ^RF . ^W1 is a single bond or a divalent fluoride hydrocarbon with 1 to 20 carbon atoms. ^RE is a single bond or a divalent organic group with 1 to 20 carbon atoms. When ^A1 is -COO-*, -OCO-*, or _-SO₂O- *, ^W1 or ^RF has a fluorine atom on the carbon atom bonded to ^A1 or on the adjacent carbon atom. When ^A1 is an oxygen atom, ^W1 and ^RE are single bonds, ^RD is a structure formed by a carbonyl group bonded to the end of the ^RE side of an hydrocarbon group with 1 to 20 carbon atoms, and ^RF is an organic group with a fluorine atom. When s is 2 or 3, multiple ^RE , ^W1 , ^A1 , and ^RF can be the same or different. Because the structural unit (VIII) has a (y) alkali-dissociating group, the surface of the anti-corrosion film changes from hydrophobic to hydrophilic during the alkali developing step. As a result, the affinity for the developing solution can be significantly improved, and developing defects can be suppressed more effectively. As a structural unit (VIII) having a (y) base dissociation group, it is particularly preferred that ^A1 is -COO-* and ^RF or ^W1 or both have fluorine atoms.

From the perspective of providing copolymerization of the monomer of structural unit (VIII), the ^RC is preferably composed of hydrogen atoms and methyl groups, and more preferably methyl groups.

When ^RE is a divalent organic group, it is preferred to be a group with a lactone structure, more preferably a group with a polycyclic lactone structure, and even more preferably a group with a norbornene lactone structure.

In the case where the high-fluorine polymer has a structural unit (VIII), the lower limit of the content of structural unit (VIII) relative to all structural units constituting the high-fluorine polymer is preferably 30 mol%, more preferably 40 mol%. Furthermore, the upper limit of the content is preferably 100 mol%. By setting the content of structural unit (VIII) within the aforementioned range, the water-repellent properties of the resist film during immersion exposure can be further improved, and developing defects can be suppressed.

[Other structural units] High-fluorine polymers may also include structural units (I) in the base polymer as structural units other than those listed above.

In the case where the high-fluorine polymer contains structural unit (I), the proportion of each structural unit in the high-fluorine polymer can preferably be the proportion described in the base polymer.

The lower limit of the Mw of the high fluorine content polymer is preferably 2,000, more preferably 3,000, further preferably 4,000, and particularly preferably 5,000. Furthermore, the upper limit of the Mw is preferably 30,000, more preferably 20,000, further preferably 10,000, and particularly preferably 8,000.

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

When the radiosensitive component comprises a high-fluorine polymer, the content of the high-fluorine polymer is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, further preferably 1.5 parts by weight or more, and particularly preferably 2 parts by weight or more, relative to 100 parts by weight of the base polymer. Alternatively, it is preferably 15 parts by weight or less, more preferably 13 parts by weight or less, further preferably 10 parts by weight or less, and particularly preferably 8 parts by weight or less.

By setting the content of high-fluorine polymers within the aforementioned range, the high-fluorine polymers can be more effectively concentrated on the surface of the anti-corrosion film. As a result, the water repellency of the anti-corrosion film surface can be improved during liquid immersion exposure, or surface modification or control of the composition distribution of the anti-corrosion film during EUV exposure can be achieved. The radiosensitive composition may contain one or more high-fluorine polymers.

(Synthesis method of high fluorine content polymer) High fluorine content polymers can be synthesized using the same method as the synthesis method of the base polymer.

<Soluble (E)> The radiosensitive composition of this embodiment contains a solvent (E). The solvent (E) is not particularly limited as long as it is capable of dissolving or dispersing the polymer (A) and, if necessary, a radiosensitive acid generator, an acid diffusion control agent, etc.

As solvents, examples include: alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, and hydrocarbon solvents.

Examples of alcohol-based solvents include: isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, diacetone alcohol, and other monools with 1 to 18 carbon atoms; ethylene glycol, 1,2-propanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, and other polyols with 2 to 18 carbon atoms; and polyol partial ether solvents formed by etherifying a portion of the hydroxyl group of the aforementioned polyol solvents.

In this embodiment, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in alcohol solvents.

Examples of ether solvents include: dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; ether solvents containing aromatic rings such as diphenyl ether and anisole (methyl phenyl ether); and polyol ether solvents formed by etherifying the hydroxyl groups of the aforementioned polyol solvents.

Examples of ketone solvents include: acetone, butanone, methyl isobutyl ketone and other chain ketone solvents; cyclopentanone, cyclohexanone, methyl cyclohexanone and other cyclic ketone solvents; 2,4-pentanedione, acetone-acetone, acetophenone, etc.

Examples of acetamide solvents include cyclic acetamide solvents such as N,N'-dimethylimidazolidineone and N-methylpyrrolidone; and chain acetamide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionic acid.

Examples of ester solvents include: monocarboxylic acid ester solvents such as n-butyl acetate; polyol 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 valproic acid lactone; carbonate solvents such as diethyl carbonate, ethyl carbonate, and propyl carbonate; and polycarboxylic acid diester solvents such as propylene glycol diacetate, methoxytriethylene glycol acetate, diethyl oxalate, ethyl acetate, and diethyl phthalate.

Examples of hydrocarbon solvents include: aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-pentylnaphthalene.

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

(Other Optional Components) The radiosensitive composition may contain any other components besides the aforementioned components. Examples of such other optional components include: crosslinking agents, pre-existing growth promoters, surfactants, compounds containing alicyclic skeletons, sensitizers, etc. One or more of these other optional components may be used individually.

There are no particular limitations on the surfactant used, but non-fluorinated or non-silicone surfactants are preferred.

When the radiosensitive component contains a surfactant, the surfactant content is preferably 0.1 parts by weight or more, more preferably 0.3 parts by weight or more, relative to 100 parts by weight of the base polymer (A). Furthermore, it is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 1 part by weight or less.

<Preparation Method of Radiosensitive Composition> The radiosensitive composition can be prepared, for example, by mixing a polymer (A), a solvent (E), and, if desired, a radiosensitive acid generator (C), an acid diffusion control agent (D), a high-fluorine polymer, etc., in a predetermined ratio. Preferably, the radiosensitive composition is filtered after mixing, for example, using a filter with a pore size of approximately 0.05 μm to 0.40 μm. The solid content concentration of the radiosensitive composition is typically 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

The pattern forming method of this invention includes: a step (1) of directly or indirectly coating the radiosensitive composition onto a substrate to form an anti-corrosion film (hereinafter also referred to as the "anti-corrosion film forming step"); a step (2) of exposing the anti-corrosion film (hereinafter also referred to as the "exposure step"); and a step (3) of developing the exposed anti-corrosion film (hereinafter also referred to as the "development step").

According to the method for forming the resist pattern, since the radiosensitive composition is used to form a resist film with excellent sensitivity and CDU and reduced development defects, a high-quality resist pattern can be formed. The steps are explained below.

[Anticorrosion Film Formation Step] In this step (step (1)), an anticorrosion film is formed using the aforementioned radiosensitive composition. Examples of substrates for forming the anticorrosion film include silicon wafers, silicon dioxide wafers, aluminum-coated wafers, and other previously known materials. Alternatively, organic or inorganic antireflective films disclosed in, for example, Japanese Patent Application Publication No. 6-12452 or Japanese Patent Application Publication No. 59-93448 may be formed on the substrate. Examples of coating methods include, for example, spin coating, cast coating, and roller coating. After coating, pre-baking (PB) can be performed as needed to allow the solvent in the coating to evaporate. The PB temperature is typically 60°C to 150°C, preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

The lower limit of the thickness of the formed anti-corrosion film is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the film thickness is preferably 500 nm, more preferably 400 nm, and even more preferably 300 nm. For thick anti-corrosion films, when exposure using ArF excimer laser light is performed in the exposure step described later, the lower limit of the film thickness can be 100 nm, 150 nm, or 200 nm.

In the case of liquid immersion exposure, regardless of the presence or absence of water-repellent polymer additives such as high-fluorine polymers in the radiosensitive composition, in order to avoid direct contact between the liquid immersion liquid and the anti-corrosion film, a liquid immersion protective film that is insoluble in the liquid immersion liquid may be provided on the formed anti-corrosion film. As a protective film for liquid immersion, either a solvent-peelable protective film that is peeled off with a solvent before the developing step (e.g., see Japanese Patent Application Publication No. 2006-227632) or a developer-peelable protective film that is peeled off simultaneously with the developing step (e.g., see International Publication No. 2005/069076 and International Publication No. 2006/035790) can be used. From the viewpoint of yield, a developer-peelable liquid immersion protective film is preferred.

In addition, when using radiation with a wavelength of less than 50 nm as the next exposure step, it is preferable to use a polymer having the structural unit (I) and structural unit (III) as the base polymer in the composition.

[Exposure Step] In this step (step (2)), the anti-corrosion film formed in step (1), i.e., the anti-corrosion film formation step, is exposed to radiation by a photomask (which may be a liquid immersion solution such as water). The radiation used for exposure can be, for example, electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays, depending on the linewidth of the target pattern; or charged particle beams such as electron beams and alpha rays. Among these, far-ultraviolet light, electron beam, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beam, and EUV are even more preferred, and electron beam and EUV with wavelengths below 50 nm, which are positioned as next-generation exposure technologies, are even more preferred.

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

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

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

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

In addition, when developing with organic solvents, examples include: hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, and other organic solvents, or solvents containing organic solvents. Examples of such organic solvents include one or more solvents listed as solvents for the radiosensitive components. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As an ether solvent, glycol ether solvents are preferred, and more preferably ethylene glycol monomethyl ether or propylene glycol monomethyl ether. As an ester solvent, acetate ester solvents are preferred, and more preferably n-butyl acetate or amyl acetate. As a ketone solvent, chain ketones are preferred, and more preferably 2-heptanone. 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 most preferably 99% by mass or more. Other components in the developer besides organic solvent include, for example, water and silicone oil.

As mentioned above, the developing solution can be either an alkaline developing solution or an organic solvent developing solution. The appropriate solution can be selected depending on whether the desired positive or negative pattern is desired.

Examples of developing methods include: immersing a substrate in a tank filled with developer for a certain period of time (immersion method); using surface tension to deposit developer onto the substrate surface and holding it still for a certain period of time for development (puddle method); spraying developer onto the substrate surface (spraying method); and continuously spraying developer onto a substrate rotating at a certain speed while scanning the developer spray nozzle at a certain speed (dynamic dispensing method), etc.

The compound in this embodiment is represented by the following formula (1'). [Chemistry 47] (In formula (1'), ^R1 and ^R2 are independently hydrogen atoms, halogen atoms, or monovalent organic groups with 1 to 5 carbon atoms, respectively; ^L1 and ^L2 are independently single or divalent linkages, respectively; W is an aromatic ring; ^X1 is an ester bond, amide bond, or sulfonamide bond; ^R5 is a divalent organic group with 1 to 15 carbon atoms; M ⁺ is a monovalent onium cation)

As a divalent organic group with carbon number 1 to 15 represented by R ⁵ , it is preferable to use a group obtained by removing one hydrogen atom from the corresponding carbon number of the monovalent organic groups with carbon number 1 to 20 represented by ^RA2 and ^RA3 in formula (2).

^R1 , ^R2 , ^L1 , ^L2 , W, M ⁺ have the same meaning as the above formula (1).

The following structures can be listed as compounds represented by the formula (1').

[Chemistry 48]

[Chemistry 49]

This embodiment of the polymer relates to a polymer comprising a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by formula (1) below. [Chem. 50] (In formula (1), ^R1 and ^R2 are, respectively, a hydrogen atom, a halogen atom, or a monovalent organic group with 1 to 5 carbon atoms; ^L1 and ^L2 are, respectively, a single bond or a divalent linker; W is an aromatic ring; ^R3 is a divalent organic group with 1 to 20 carbon atoms; M ⁺ is a monovalent onium cation)

As the structural unit (II), those identical to the structural unit (II) of the polymer (A) in the radiosensitive composition can be preferably listed.

The structural unit (I) is preferably the structural unit represented by the following formula (2). [Chemistry 51] (In the formula (2), ^RA is a hydrogen atom, a fluorine atom, an organic group with 1 to 3 carbon atoms, or a trifluoromethyl group; ^LA1 is a divalent linker; ^RA1 is a hydrogen atom or a monovalent hydrocarbon with 1 to 20 carbon atoms; ^RA2 and ^RA3 are each independently a monovalent organic group with 1 to 20 carbon atoms or a divalent cyclic group with 3 to 20 carbon atoms formed by combining ^RA2 and ^RA3 together with the carbon atoms they are bonded to; m1 and m2 are each independently 0 or 1; wherein, when m1 is 1, m2 is 1)

As the structural unit (I), examples preferably include those identical to the structural unit (I) possessed by the polymer (A) in the radiosensitive composition. [Example]

The present invention will now be described in detail based on embodiments, but the present invention is not limited to those embodiments. The determination of various physical property values in the embodiments and comparative examples is carried out by the determination methods shown below.

[Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] were determined by gel osmosis chromatography (GPC) using monodisperse polystyrene as the standard, under the analytical conditions of a flow rate of 1.0 mL/min, a dissolution solvent of tetrahydrofuran, a sample concentration of 1.0% by mass, a sample injection volume of 100 μL, a column temperature of 40°C, and a detector of a differential refractometer. The dispersion ratio (Mw/Mn) was calculated based on the determination results of Mw and Mn.

[ ^1H -Nuclear Magnetic Resonance (NMR) Analysis and ^13C -NMR Analysis] ^1H -NMR and ^13C -NMR analyses were performed using a nuclear magnetic resonance apparatus (JNM-Delta400 of Nippon Electronics Co., Ltd.).

<Synthesis of Compound (A) (Radiosensitive Monomer)> [Synthetic Example A-1: Synthesis of Compound (A-1)] Compound (A-1) was synthesized according to the following synthetic procedure.

[Chemistry 52]

Compound (Z-1) (20 mmol) and dichloromethane (100 mL) were added to the reaction vessel and cooled to 0°C. Then, 1,1'-carbonylbis-1H-imidazole (30 mmol) and compound (Z-2) (30 mmol) were added, and the mixture was brought back to room temperature and stirred. The organic layer was washed twice with an ammonium chloride aqueous solution. The organic layer was dried with sodium sulfate and filtered. The solvent was removed by distillation, and the mixture was separated by column chromatography to obtain compound (A-1).

[Synthesis Examples A-2 to A-17, cA-18, and cA-19: Synthesis of Monomers (A-2) to A-17 and cA-18 to cA-19] Except for suitable changes to the starting materials and precursors, the compounds represented by the following formulas (A-2) to (A-17) and (cA-18) to (cA-19) were synthesized in the same manner as in Synthesis Example A-1.

[Chemistry 53]

[Chemistry 54]

[Chemistry 55]

The structures of monomers other than the monomers used in the synthesis of polymers in each embodiment and comparative example are shown.

[Chemistry 56]

<Synthesis of Polymer (P)> [Examples P-1 to P-39, Comparative Examples cP-1 to cP-5: Synthesis of Polymers (P-1) to (P-39) and (cP-1) to (cP-5)] The monomers were combined and copolymerized in 1-methoxy-2-propanol (200 parts by mass relative to all monomers). The cooled polymerization solution was added to hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered and separated. The filtered white powder was washed twice with 100 parts by mass relative to the polymerization solution of hexane, filtered and dissolved in 1-methoxy-2-propanol (300 parts by mass). The polymer was added dropwise to 500 parts by weight of water to cause coagulation, and the resulting solid was filtered and separated. It was dried at 50°C for 12 hours to obtain white powdered polymers (P-1) to (P-39) and (cP-1) to (cP-5). The composition of the obtained polymers was confirmed by ^1H -NMR, and the Mw and dispersity (Mw/Mn) were confirmed by the GPC conditions described above. The types and amounts of each monomer are shown in Tables 1 and 2. In Tables 1 and 2, "-" indicates that the corresponding component was not used. The same applies to subsequent tables.

[Table 1] Implementation Examples Polymer (P) Structural Unit (III) Structural Unit (I) Structural unit (II) etc. Structural units (IVs), etc. Mw Mw/Mn Kind Dosage (mol%) Kind Dosage (mol%) Kind Dosage (mol%) Kind Dosage (mol%) P-1 P-1 M-1 35 M-8 55 A-1 10 - - 5890 1.7 P-2 P-2 M-1 35 M-9 55 A-1 10 - - 6927 1.8 P-3 P-3 M-1 35 M-10 55 A-1 10 - - 6628 1.8 P-4 P-4 M-1 35 M-11 55 A-1 10 - - 6158 1.8 P-5 P-5 M-1 35 M-12 55 A-1 10 - - 5845 1.7 P-6 P-6 M-1 35 M-13 55 A-1 10 - - 6095 1.7 P-7 P-7 M-1 35 M-14 55 A-1 10 - - 5974 1.7 P-8 P-8 M-1 35 M-15 55 A-1 10 - - 5839 1.8 P-9 P-9 M-1 35 M-16 55 A-1 10 - - 6617 1.7 P-10 P-10 M-1 35 M-17 55 A-1 10 - - 6184 1.7 P-11 P-11 M-1 35 M-18 55 A-1 10 - - 6442 1.7 P-12 P-12 M-2 35 M-9 55 A-1 10 - - 6616 1.7 P-13 P-13 M-3 35 M-9 55 A-1 10 - - 6023 1.8 P-14 P-14 M-4 35 M-9 55 A-1 10 - - 5559 1.7 P-15 P-15 M-5 35 M-9 55 A-1 10 - - 6134 1.7 P-16 P-16 M-6 35 M-9 55 A-1 10 - - 5460 1.8 P-17 P-17 M-7 35 M-9 55 A-1 10 - - 5845 1.8 P-18 P-18 M-1 35 M-9 45 A-1 10 M-19 10 5565 1.8 P-19 P-19 M-1 35 M-9 45 A-1 10 M-20 10 6410 1.7 P-20 P-20 M-1 35 M-9 55 A-2 10 - - 5818 1.7 P-21 P-21 M-1 35 M-9 55 A-3 10 - - 6527 1.8 P-22 P-22 M-1 35 M-9 55 A-4 10 - - 6687 1.7 P-23 P-23 M-1 35 M-9 55 A-5 10 - - 5955 1.8 P-24 P-24 M-1 35 M-9 55 A-6 10 - - 6741 1.7 P-25 P-25 M-1 35 M-9 55 A-7 10 - - 6979 1.8 P-26 P-26 M-1 35 M-9 55 A-8 10 - - 6818 1.7 P-27 P-27 M-1 35 M-9 55 A-9 10 - - 6246 1.8 P-28 P-28 M-1 35 M-9 55 A-10 10 - - 5578 1.8 P-29 P-29 M-1 35 M-9 55 A-11 10 - - 6258 1.8 P-30 P-30 M-1 35 M-9 55 A-12 10 - - 5553 1.7 P-31 P-31 M-1 35 M-9 55 A-13 10 - - 6459 1.8 P-32 P-32 M-1 35 M-9 55 A-14 10 - - 6987 1.8 P-33 P-33 M-1 35 M-9 55 A-15 10 - - 5554 1.8 P-34 P-34 M-1 35 M-9 55 A-16 10 - - 5377 1.8 P-35 P-35 M-1 35 M-9 55 A-17 10 - - 6124 1.8 P-36 P-36 M-1 35 M-9 60 A-1 10 - - 5833 1.8 P-37 P-37 M-1 35 M-9 50 A-1 10 - - 6380 1.7 P-38 P-38 M-1 35 M-9 45 A-1 10 - - 6186 1.8 P-39 P-39 M-1 35 M-9 40 A-1 10 - - 5679 1.7

[Table 2] Comparative example Polymer (P) Structural Unit (III) Structural unit (I) etc. Structural unit (II) etc. Mw Mw/Mn Kind Dosage (mol%) Kind Dosage (mol%) Kind Dosage (mol%) cP-1 cP-1 M-1 35 M-9 55 cA-18 10 6889 1.7 cP-2 cP-2 M-1 35 M-9 55 cA-19 10 6907 1.7 cP-3 cP-3 M-1 35 cM-23 55 A-1 10 6742 1.7 cP-4 cP-4 M-1 35 cM-24 55 A-1 10 5993 1.8 cP-5 cP-5 M-1 35 cM-24 60 A-1 5 6947 1.7

[Synthesis of High-Fluoride Polymers] [Synthesis Example 1: Synthesis of Polymer (F-1)] The monomers were combined and copolymerized in 2-butanone (200 parts by mass) solvent. After polymerization, the polymerization solution was cooled to below 30°C by water cooling. The solvent was replaced with acetonitrile (400 parts by mass), and hexane (100 parts by mass) was added. The mixture was stirred and the acetonitrile layer was recovered. This process was repeated three times. The solvent was replaced with propylene glycol monomethyl ether acetate, thereby obtaining a solution of polymer (F-1) in good yield. The composition of the obtained polymer was confirmed by ^1H -NMR, and the Mw and dispersion (Mw/Mn) were confirmed by the GPC conditions. The composition, along with the types and amounts of the monomers, is shown in Table 3.

[Table 3] Synthesis example Polymer (F) Structural Unit (VIII) Mw Mw/Mn Kind Dosage (mol%) 1 F-1 M-21 30 5249 1.8 M-22 70

<Preparation of Radiosensitive Components> The following shows other radiosensitive acid generators, acid diffusion control agents and solvents that constitute radiosensitive components.

[Radiosensitive acid producers] Compounds represented by formulas (C-1) to (C-9) below. [Chem. 57]

[Acid diffusion control agents] Compounds represented by formulas (D-1) to (D-6) below. [Chemistry 58]

[Organic Solvent] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether

[Preparation of Radiosensitive Compositions] [Examples 1 to 69 and Comparative Examples 1 to 5] (P-1) to (P-39) as polymers, (C-1) to (C-9) as radiosensitive acid generators, (D-1) to (D-6) as acid diffusion control agents, (F-1) as a high-fluorine polymer, and (E-1) and (E-2) as organic solvents were mixed together. The resulting product was filtered using a 0.2 μm pore size membrane filter to prepare radiosensitive compositions (R-1) to (R-69) and (CR-1) to (CR-5). The types and amounts of each component are shown in Tables 4 and 5.

[Table 4] Radiosensitive components Polymer (P) Polymer (F) Radiosensitive acid-producing agent (C) Acid diffusion control agent (D) Solvent (E) Kind mass Kind mass Kind mass Kind mol% relative to acid-producing agents Kind mass Implementation Example 1 R-1 P-1 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 2 R-2 P-2 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 3 R-3 P-3 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 4 R-4 P-4 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 5 R-5 P-5 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 6 R-6 P-6 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 7 R-7 P-7 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 8 R-8 P-8 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 9 R-9 P-9 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 10 R-10 P-10 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 11 R-11 P-11 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 12 R-12 P-12 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 13 R-13 P-13 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 14 R-14 P-14 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 15 R-15 P-15 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 16 R-16 P-16 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 17 R-17 P-17 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 18 R-18 P-18 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 19 R-19 P-19 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 20 R-20 P-20 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 21 R-21 P-21 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 22 R-22 P-22 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 23 R-23 P-23 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 24 R-24 P-24 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 25 R-25 P-25 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 26 R-26 P-26 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 27 R-27 P-27 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 28 R-28 P-28 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 29 R-29 P-29 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 30 R-30 P-30 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 31 R-31 P-31 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 32 R-32 P-32 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 33 R-33 P-33 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 34 R-34 P-34 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 35 R-35 P-35 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 36 R-36 P-36 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 37 R-37 P-37 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 38 R-38 P-38 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 39 R-39 P-39 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000

[Table 5] Radiosensitive components Polymer (P) Polymer (F) Radiosensitive acid-producing agent (C) Acid diffusion control agent (D) Solvent (E) Kind mass Kind mass Kind mass Kind mol% relative to acid-producing agents Kind mass Implementation Example 40 R-40 P-20 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 41 R-41 P-21 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 42 R-42 P-22 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 43 R-43 P-23 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 44 R-44 P-24 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 45 R-45 P-25 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 46 R-46 P-26 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 47 R-47 P-27 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 48 R-48 P-28 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 49 R-49 P-29 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 50 R-50 P-30 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 51 R-51 P-31 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 52 R-52 P-32 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 53 R-53 P-33 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 54 R-54 P-34 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 55 R-55 P-35 100 - - - - D-1 40 E-1/E-2 4800/2000 Implementation Example 56 R-56 P-1 100 - - C-2 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 57 R-57 P-1 100 - - C-3 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 58 R-58 P-1 100 - - C-4 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 59 R-59 P-1 100 - - C-5 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 60 R-60 P-1 100 - - C-6 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 61 R-61 P-1 100 - - C-7 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 62 R-62 P-1 100 - - C-8 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 63 R-63 P-1 100 - - C-9 5 D-1 40 E-1/E-2 4800/2000 Implementation Example 64 R-64 P-1 100 - - C-1 5 D-2 40 E-1/E-2 4800/2000 Implementation Example 65 R-65 P-1 100 - - C-1 5 D-3 40 E-1/E-2 4800/2000 Implementation Example 66 R-66 P-1 100 - - C-1 5 D-4 40 E-1/E-2 4800/2000 Implementation Example 67 R-67 P-1 100 - - C-1 5 D-5 40 E-1/E-2 4800/2000 Implementation Example 68 R-68 P-1 100 - - C-1 5 D-6 40 E-1/E-2 4800/2000 Implementation Example 69 R-69 P-1 100 F-1 6 C-1 5 D-1 40 E-1/E-2 4800/2000 Comparative example 1 CR-1 CP-1 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Comparative example 2 CR-2 CP-2 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Comparative example 3 CR-3 CP-3 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Comparative example 4 CR-4 CP-4 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000 Comparative example 5 CR-5 CP-5 100 - - C-1 5 D-1 40 E-1/E-2 4800/2000

<Formation of Anti-corrosion Pattern> The prepared radiosensitive components were coated onto the surface of a 12-inch silicon wafer with a 20 nm thick lower layer film (AL412, manufactured by Brewer Science) using a spin coater (CLEAN TRACK ACT12). After a pre-bake (PB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 30 nm thick anti-corrosion film. The anti-corrosion film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, numerical aperture (NA) = 0.33, illumination conditions: conventional s = 0.89). The anti-corrosion film was then exposed to EUV light for 60 seconds at 100°C and subsequently baked (PEB). Next, it was developed using a 2.38% by mass TMAH aqueous solution at 23°C for 30 seconds to form a positive 36 nm contact hole pattern.

<Evaluation> The formed resist patterns were measured according to the following method to evaluate the sensitivity, CDU, and number of developing defects of each radiosensitive component. Furthermore, a scanning electron microscope (Hitachi High-Technologies CG-5000) was used for measuring the length of the resist patterns. The evaluation results are shown in Tables 6 and 7 below.

[Sensitivity] In the formation of the resist pattern, the exposure amount for forming the 36 nm contact hole pattern is set as the optimal exposure amount, and this optimal exposure amount is set as the sensitivity (mJ/ ^cm² ). The smaller the sensitivity value, the better. Regarding sensitivity, a value less than 40 mJ/ ^cm² is judged as "A" (extremely good), a value between 40 mJ/ ^cm² and 44 mJ/ ^cm² is judged as "B" (good), and a value exceeding 44 mJ/ ^cm² is judged as "C" (poor).

[CDU] In the formation of the resist pattern, a 36 nm contact hole pattern is formed. The formed resist pattern is observed from the top of the pattern using a scanning electron microscope. The deviation of the aperture at a total of 600 points is measured, and a 3 sigma value is calculated based on the distribution of the measured values. This 3 sigma value is set as CDU (nm). The smaller the CDU value, the smaller the aperture deviation over a long period, and the better. Regarding CDU, cases less than 3.0 nm are judged as "A" (extremely good), cases between 3.0 nm and 3.4 nm are judged as "B" (good), and cases exceeding 3.4 nm are judged as "C" (poor).

[Number of Development Defects] A 36 nm contact hole pattern is formed and a wafer is designated for defect inspection. The number of defects on the wafer is measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less are then identified as originating from the resist film, and their number is calculated. Regarding the number of defects after development, a condition where the number of defects identified as originating from the resist film is less than 35 is classified as "A" (Excellent), a condition where the number is 35 to 60 is classified as "B" (Good), and a condition where the number exceeds 60 is classified as "C" (Poor).

[Table 6] Sensitivity CDU Display defects Implementation Example 1 A A A Implementation Example 2 A A A Implementation Example 3 A A A Implementation Example 4 A A A Implementation Example 5 A A A Implementation Example 6 A A A Implementation Example 7 A A A Implementation Example 8 A A A Implementation Example 9 A A A Implementation Example 10 A A A Implementation Example 11 A A A Implementation Example 12 A A A Implementation Example 13 A A A Implementation Example 14 A A A Implementation Example 15 A A A Implementation Example 16 A A A Implementation Example 17 A A A Implementation Example 18 A A A Implementation Example 19 A A A Implementation Example 20 A B A Implementation Example 21 A B A Implementation Example 22 A A A Implementation Example 23 A A A Implementation Example 24 A A B Implementation Example 25 A B A Implementation Example 26 A A A Implementation Example 27 A A A Implementation Example 28 A A A Implementation Example 29 A A A Implementation Example 30 A A B Implementation Example 31 A A A Implementation Example 32 A A A Implementation Example 33 A A A Implementation Example 34 A A A Implementation Example 35 B A A Implementation Example 36 A A A Implementation Example 37 A A A Implementation Example 38 A A A Implementation Example 39 B A A

[Table 7] Sensitivity CDU Display defects Implementation Example 40 A B A Implementation Example 41 A B A Implementation Example 42 A A A Implementation Example 43 A A A Implementation Example 44 A A B Implementation Example 45 A B A Implementation Example 46 A A A Implementation Example 47 A A A Implementation Example 48 A A A Implementation Example 49 A A A Implementation Example 50 A A B Implementation Example 51 B A A Implementation Example 52 A A A Implementation Example 53 A A A Implementation Example 54 A A A Implementation Example 55 B A A Implementation Example 56 A A A Implementation Example 57 A A A Implementation Example 58 A A A Implementation Example 59 A A A Implementation Example 60 A A A Implementation Example 61 A A A Implementation Example 62 B A A Implementation Example 63 A A A Implementation Example 64 A A A Implementation Example 65 A A A Implementation Example 66 A A A Implementation Example 67 B A A Implementation Example 68 A A A Implementation Example 69 A A A Comparative example 1 C C B Comparative example 2 B C B Comparative example 3 B B C Comparative example 4 C C C Comparative example 5 B C B [Industry-level applicability]

According to the present invention, the method for forming a radiosensitive composition and resist pattern can improve sensitivity, CDU, and number of developing defects compared to previous methods. Therefore, these methods are better suited for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

without

Claims (18)

A radiosensitive composition comprising: a polymer (A) comprising a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by formula (1) below; and a solvent (E); [Chem. 1] (In formula (1), ^R1 and ^R2 are hydrogen atoms, halogen atoms or monovalent organic groups with 1 to 5 carbon atoms, respectively; ^L1 and ^L2 are single bonds or divalent linkages, respectively; W is an aromatic ring; ^R3 is a divalent organic group with 1 to 20 carbon atoms; M ⁺ is a monovalent onium cation). The radiosensitive composition as described in claim 1, wherein the structural unit (I) is represented by the following formula (2); [Chemistry 2] (In the formula (2), ^RA is a hydrogen atom, a fluorine atom, an organic group with 1 to 3 carbons or a trifluoromethyl group; ^LA1 is a divalent linker; ^RA1 is a hydrogen atom or a monovalent hydrocarbon with 1 to 20 carbons; ^RA2 and ^RA3 are each independently monovalent organic groups with 1 to 20 carbons or divalent cyclic groups with 3 to 20 carbons formed by combining ^RA2 and ^RA3 together with the carbon atoms they are bonded to; m1 and m2 are each independently 0 or 1; wherein, when m1 is 1, m2 is 1). The radiosensitive composition as described in claim 1, wherein the structural unit (II) is represented by the following formula (1-1); [Chemical 3] (In formula (1-1), X is an ester bond, ether bond, amide bond or sulfonamide bond; ^R4 is a divalent organic group with 1 to 10 carbon atoms; n is 0 or 1; ^Rf1 and ^Rf2 are independently hydrogen atoms, halogen atoms, hydroxyl groups, nitro groups, thiol groups, amino groups or monovalent organic groups with 1 to 20 carbon atoms; when there are multiple ^Rf1 and ^Rf2 , the multiple ^Rf1 and ^Rf2 are the same or different from each other; among them, ^Rf1 or ^Rf2 on the carbon atom at the α or β position of the sulfur atom ^of _-SO3- is a fluorine atom or a fluorinated hydrocarbon group; m is an integer from 0 to 5; among them, 1≦m+n; ^R1 , ^R2 , ^L1 , ^L2 , W, M ⁺ have the same meaning as the above formula (1). The radiosensitive composition as described in claim 1, wherein the aromatic ring in W of formula (1) is a benzene ring or a naphthalene ring. The radiosensitive composition as described in claim 1, wherein ^L1 and ^L2 are each independently a single bond, an alkyl group having 1 to 5 carbon atoms, -O-, -S- or ^-NR11- ( ^R11 is a hydrogen atom or a monovalent hydrocarbon). The radiosensitive composition as claimed in claim 1, wherein the structural unit (II) has an iodine group. The radiosensitive composition as claimed in claim 1, wherein the structural unit (I) has an iodine group. The radiosensitive composition as described in any one of claims 1 to 7, wherein the structural unit (II) accounts for more than 1 mol% and less than 50 mol% of all structural units constituting the polymer (A). The radiosensitive composition as described in any one of claims 1 to 7, wherein the structural unit (I) comprises 10 mol% or more and 80 mol% or less of all structural units constituting the polymer (A). The radiosensitive composition as described in any one of claims 1 to 7, wherein the polymer (A) further comprises a structural unit (III) having a phenolic hydroxyl group. The radiosensitive composition as claimed in claim 10, wherein the structural unit (III) comprises 15 mol% or more and 50 mol% or less of all structural units constituting the polymer (A). The radiosensitive composition as described in any of claims 1 to 7 further comprises a radiosensitive acid generator. The radiosensitive composition as described in any of claims 1 to 7 further comprises an acid diffusion control agent. A method for forming a pattern includes: a step of directly or indirectly applying a radiosensitive composition as described in any one of claims 1 to 7 onto a substrate to form an anti-corrosion film; a step of exposing the anti-corrosion film; and a step of developing the exposed anti-corrosion film using a developing solution. The pattern forming method as described in claim 14, wherein extreme ultraviolet light or an electron beam is used for the exposure. A compound is represented by the following formula (1'); [Chemistry 4] (In formula (1'), ^R1 and ^R2 are hydrogen atoms, halogen atoms or monovalent organic groups with 1 to 5 carbon atoms, respectively; ^L1 and ^L2 are single bonds or divalent linkages, respectively; W is an aromatic ring; ^X1 is an ester bond, amide bond or sulfonamide bond; ^R5 is a divalent organic group with 1 to 15 carbon atoms; M ⁺ is a monovalent onium cation). A polymer comprising a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by formula (1) below; [Chem. 5] (In formula (1), ^R1 and ^R2 are hydrogen atoms, halogen atoms or monovalent organic groups with 1 to 5 carbon atoms, respectively; ^L1 and ^L2 are single bonds or divalent linkages, respectively; W is an aromatic ring; ^R3 is a divalent organic group with 1 to 20 carbon atoms; M ⁺ is a monovalent onium cation). The polymer as claimed in claim 17, wherein the structural unit (I) is represented by the following formula (2); [Chemical 6] (In the formula (2), ^RA is a hydrogen atom, a fluorine atom, an organic group with 1 to 3 carbons or a trifluoromethyl group; ^LA1 is a divalent linker; ^RA1 is a hydrogen atom or a monovalent hydrocarbon with 1 to 20 carbons; ^RA2 and ^RA3 are each independently monovalent organic groups with 1 to 20 carbons or divalent cyclic groups with 3 to 20 carbons formed by combining ^RA2 and ^RA3 together with the carbon atoms they are bonded to; m1 and m2 are each independently 0 or 1; wherein, when m1 is 1, m2 is 1).