Radiation-sensitive composition and pattern formation method

Abstract

Provided are: a radiation-sensitive composition capable of exhibiting sensitivity, critical dimension uniformity (CDU), a process window, and a development defect-suppressing property at levels equal to or higher than those of existing compositions when forming a pattern; and a pattern formation method. The radiation-sensitive composition comprises a polymer and a solvent, and the polymer includes: a structural unit (I) containing an ester bond-containing monocyclic structure; a structural unit (II) derived from a compound represented by formula (1); and a structural unit (III) having a phenolic hydroxyl group. (In formula (1), Ar1 is a substituted or unsubstituted 3C-20C monovalent aromatic group. R1 is a hydrogen atom or a 1C-20C monovalent organic group, R2 is a 1C-20C monovalent organic group, or if R1 is a hydrogen atom, R2 is bonded to Ar1 and forms a ring structure together with the carbon atom to which R2 is bonded and the Ar1. R3 is a hydrogen atom, a halogen group, or a 1C-20C monovalent organic group. L1 is a single bond or a divalent linking group.)

Description

Radiation-sensitive composition and pattern-forming method

[0001] The present invention relates to a radiation-sensitive composition and a pattern-forming method.

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

[0003] The above-mentioned photolithography techniques utilize short-wavelength radiation such as ArF excimer lasers, or combine this radiation with liquid immersion lithography to advance pattern miniaturization. As a next-generation technology, efforts are being made to utilize even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet).

[0004] With the miniaturization of patterns, there is a demand for more functional resist compositions. A technique has been proposed to improve the development contrast of polymers, which are the main components of resist compositions (Japanese Patent Publication No. 2023-146349).

[0005] Japanese Patent Publication No. 2023-146349

[0006] In deploying the above-mentioned next-generation technologies, the resist composition is required to have resist performance equivalent to or better than conventional resists in terms of sensitivity, CDU, process window, and development defect suppression during pattern formation.

[0007] The present invention aims to provide a radiation-sensitive composition and a pattern-forming method that can exhibit sensitivity, CDU, process window, and development defect suppression at a level equivalent to or better than conventional methods during pattern formation.

[0008] The inventors of this invention conducted extensive research to solve this problem and, as a result, found that the above objective can be achieved by adopting the following configuration, thus completing the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition containing a polymer and a solvent, wherein the polymer includes a structural unit (I) containing a monocyclic structure having an ester bond, a structural unit (II) derived from a compound represented by the following formula (1), and a structural unit (III) having a phenolic hydroxyl group. (In formula (1), Ar １ is a monovalent aromatic group having 3 to 20 carbon atoms, which may be substituted or unsubstituted. R １ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ２ is a monovalent organic group having 1 to 20 carbon atoms, or when R １ is a hydrogen atom, R ２ is bonded to Ar １ and forms a ring structure together with the carbon atom to which R ２ is bonded and Ar １ . R ３ is a hydrogen atom, a halogeno group, or a monovalent organic group having 1 to 20 carbon atoms. L １ is a single bond or a divalent linking group.)

[0010] According to the radiation-sensitive composition, excellent sensitivity, CDU, process window, and development defect suppression ability can be exhibited during resist pattern formation. Although the reason for this is not clear, it is speculated as follows. In the structural unit (II), Ar １ , R １ , R ２The structure composed of carbon atoms to which these are bonded, and ester bonds bonded to these carbon atoms (hereinafter also referred to as the "dissociable structure"), is a structure that dissociates upon the action of acid or radiation to generate carboxyl groups. Because this dissociable structure allows for control of polymer solubility by dissociating not only with acid but also with radiation, sensitivity, development contrast, and exposure margin can be improved. Furthermore, the rigidity of the aromatic groups in the dissociable structure increases the glass transition temperature of the resist film, allowing for appropriate control of the diffusion length of acid generated by exposure. As a result, roughness can be improved. On the other hand, because the dissociable structure contains highly hydrophobic aromatic groups, the solubility of the dissociated components is low, which can lead to development defects. In this radiation-sensitive composition, a structural unit (I) containing an ester bond-containing monocyclic structure is introduced as a copolymer component of the polymer, thus exhibiting good solubility during alkaline development. It is presumed that the above-mentioned resist performance can be achieved through the combined effects of these factors.

[0011] In another embodiment, the present invention relates to a pattern forming method comprising the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

[0012] In this pattern formation method, since the above-mentioned radiation-sensitive composition is used, which exhibits excellent sensitivity, CDU, process window, and development defect suppression during pattern formation, high-quality resist patterns can be efficiently formed.

[0013] In this specification, terms are defined as follows: "Ester bond-containing monocyclic structure" refers to a monocyclic structure having an ester bond as a ring structure, and includes monocyclic lactone structures (carboxylic acid ester-containing monocyclic structures), monocyclic carbonate structures (carbonate ester-containing monocyclic structures), and monocyclic sultone structures (sulfonic acid ester-containing monocyclic structures). "Organic group" refers to a group containing at least one carbon atom. However, cyano groups, carboxyl groups, formyl groups, carbonyl groups, etc., which can function or be characteristic groups on their own as organic groups are excluded. "Fused ring structure" refers to a structure in which adjacent rings share one side (two adjacent atoms). "Bridged ring hydrocarbon group" refers to a polycyclic cyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms constituting the ring are bonded together by a linking group containing one or more carbon atoms. In structural formulas, the abbreviations for substituents are "Me" for methyl group, "Et" for ethyl group, and "Ph" for phenyl group.

[0014] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. Preferred combinations of embodiments are also preferred.

[0015] Radiation-sensitive composition The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a polymer (hereinafter also referred to as "base polymer") and a solvent. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

[0016] <Polymers> A polymer (i.e., a base polymer) is an aggregate of polymer chains containing the above-mentioned structural units (I), (II), and (III). In addition to structural units (I) to (III), the base polymer may also contain other structural units.

[0017] (Structural Unit (I)) Structural unit (I) is a structural unit that includes an ester bond-containing monocyclic structure. The ester bond-containing monocyclic structure preferably has a structure in which an ester bond is incorporated between the carbon atoms of a monocyclic cycloalkane, and examples include monocyclic lactone structures, monocyclic carbonate structures, and monocyclic sultone structures. Structural unit (I) may contain one or more ester bond-containing monocyclic structures. The polymer may contain one or more structural units (I).

[0018] The number of ring members in the above ester bond-containing monocyclic structure is not particularly limited, but a 5- to 8-membered ring is preferred, a 5- to 7-membered ring is more preferred, and a 5- or 6-membered ring is even more preferred.

[0019] The above ester bond-containing monocyclic structure may have substituents. Examples of substituents include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; amino groups; alkyl groups, alkoxy groups, aryloxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; or groups that combine these groups; oxo groups (=O), etc.

[0020] Examples of alkyl groups as substituents include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, and t-butyl groups. Examples of alkoxy groups include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as methoxy, ethoxy, and propoxy groups. Examples of aryloxy groups include aryloxy groups having 6 to 14 carbon atoms, such as phenyloxy groups. Examples of alkoxycarbonyl groups include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as methoxycarbonyl and ethoxycarbonyl groups. Examples of alkoxycarbonyloxy groups include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of acyl groups include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl groups, propionyl groups, benzoyl groups, and acryloyl groups. Examples of acyloxy groups include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as acetyloxy groups, propionyloxy groups, benzoyloxy groups, and acryloyloxy groups.

[0021] The above ester bond-containing monocyclic structure is preferably a monocyclic lactone structure.

[0022] Examples of structural units (I) include structures represented by the following formulas (T-1) to (T-4).

[0023]

[0024] In the above formulas (T-1) to (T-4), R Ｌ１ Each of these is independently a hydrogen atom, a halogeno group, or a monovalent organic group having 1 to 20 carbon atoms. Ｌ２ Each of these is an independent substituent. ２ Each of these is an independent single bond or a divalent linking group. Each of these is an independent integer from 1 to 3. Each of these is an independent integer from 0 to 2m+1. If k is 2 or greater, there are multiple R Ｌ２These are either identical or different from each other. In the above formula (T-1), the bond represented by the following formula is either a single bond or a double bond.

[0025] R Ｌ１ Examples of halogen groups represented by this formula include fluoro groups, chloro groups, bromo groups, and iodine groups.

[0026] R Ｌ１ Examples of monovalent organic groups having 1 to 20 carbon atoms represented by include monovalent hydrocarbon groups having 1 to 20 carbon atoms, a group (a) having a divalent heteroatom-containing linking group between carbon atoms (between two adjacent or non-adjacent carbon atoms) or at the end of the hydrocarbon group, a group (β) in which some or all of the hydrogen atoms of the hydrocarbon group or group (a) are replaced with a monovalent heteroatom-containing group, or combinations thereof.

[0027] Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, or combinations thereof.

[0028] Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0029] Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include cycloalkyl groups such as cyclopentyl and cyclohexyl groups; cycloalkenyl groups such as cyclopropenyl, cyclopentenyl, and cyclohexenyl groups; bridged ring saturated hydrocarbon groups such as norbornyl, adamantyl, and tricyclodecyl groups; and bridged ring unsaturated hydrocarbon groups such as norbornyl and tricyclodecenyl groups.

[0030] Examples of monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0031] Examples of heteroatoms that constitute a divalent heteroatom-containing linking group or a monovalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, halogen atoms, and the like.

[0032] Examples of divalent heteroatom-containing linking groups include -CO-, -CS-, -O-, -S-, and -SO ２ -, -NR'-, or a combination of two or more of these groups. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Unless otherwise specified, in this specification, divalent heteroatom-containing linking groups represent these structures.

[0033] Examples of monovalent heteroatom-containing groups include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0034] R Ｌ１ A hydrogen atom or a methyl group is preferred as the element.

[0035] R Ｌ２ As the substituent represented by , substituents that the above-mentioned ester bond-containing monocyclic structure may have can be suitably adopted. Ｌ２ Preferably, substituents represented by are alkyl groups and halogen atoms, and more preferably methyl groups, ethyl groups, and iodine atoms.

[0036] L ２ Examples of divalent linking groups represented by include divalent hydrocarbon groups that are alkanediyl groups, cycloalkanediyl groups, alkenediyl groups, or arenediyl groups; divalent heteroatom-containing linking groups; groups in which the divalent heteroatom-containing linking group is incorporated between the carbon-carbon bonds of the divalent hydrocarbon group or at the terminus of the divalent hydrocarbon group; or groups that combine these. Some or all of the hydrogen atoms in these groups may be substituted with substituents.

[0037] The alkanediyl group described above is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, or a 2,2-propanediyl group.

[0038] Examples of the above-mentioned cycloalkanediyl groups include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups; and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. A cycloalkanediyl group having 5 to 12 carbon atoms is preferred.

[0039] Examples of the alkenediyl group mentioned above include ethendiyl group, propenediyl group, and butenediyl group. A preferred alkenediyl group is one having 2 to 6 carbon atoms.

[0040] Examples of the above-mentioned arenediyl group include a benzenediyl group and a naphthalenediyl group. A preferred arenediyl group has 6 to 15 carbon atoms.

[0041] L ２ If the molecule has substituents, the substituents that the ester bond-containing monocyclic structure may have can be preferably adopted.

[0042] L ２ In terms of structural freedom and solubility, alkanediyl groups, divalent heteroatom-containing linking groups, or combinations thereof are preferred, and are C1-C4 alkanediyl groups, -COO- ＊ 、-CONR'- ＊ A group consisting of these, or a combination thereof, is more preferable, and a methanediyl group, an ethanediyl group, -COO-, -CONR'-, or a combination thereof is even more preferable. R' is as described above. * indicates a ring-side bond.

[0043] m is preferably 1 or 2, and more preferably 1.

[0044] k is preferably an integer between 0 and 3, more preferably an integer between 0 and 2, and even more preferably 0 or 1.

[0045] While there are no particular limitations on specific examples of monomeric compounds that give structural unit (I), examples include compounds represented by the following formula. In the following formula, R Ｌ１ This is equivalent to the above equations (T-1) to (T-4).

[0046]

[0047]

[0048] The lower limit of the content of structural unit (I) in the total structural units constituting the base polymer (the total content if multiple types exist) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. The upper limit of the content is preferably 70 mol%, more preferably 50 mol%, even more preferably 40 mol%, and particularly preferably 30 mol%. By setting the content of structural unit (I) within the above range, the radiation-sensitive composition can further improve the resist performance and the adhesion of the formed resist pattern to the substrate.

[0049] (Structural Unit (II)) Structural unit (II) is a structural unit derived from the compound represented by the following formula (1). (In formula (1), Ar １ R is a substituted or unsubstituted monovalent aromatic group having 3 to 20 carbon atoms. １ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ２ is a monovalent organic group having 1 to 20 carbon atoms, or R １ If R is a hydrogen atom, ２ Ar １ Accordingly, R ２ The carbon atoms and Ar that are bonded to it １ Together, they form a ring structure. ３ This is a hydrogen atom, a halogeno group, or a monovalent organic group having 1 to 20 carbon atoms. １ (This is a single bond or a divalent linking group.)

[0050] Ar １Examples of monovalent aromatic groups having 3 to 20 carbon atoms represented by include substituted or unsubstituted monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, substituted or unsubstituted monovalent aromatic heterocyclic groups having 3 to 20 carbon atoms, or combinations thereof.

[0051] As the above-mentioned monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, a group obtained by removing one hydrogen atom from an aromatic hydrocarbon ring having 6 to 20 carbon atoms can be suitably adopted. Examples of the above-mentioned aromatic hydrocarbon ring include a benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, and perylene ring.

[0052] As the above-mentioned monovalent aromatic heterocyclic group having 3 to 20 carbon atoms, a group obtained by removing one hydrogen atom from an aromatic heterocyclic ring having 3 to 20 carbon atoms can be suitably adopted. Examples of the above-mentioned aromatic heterocyclic rings include furan rings, pyrrole rings, thiophene rings, phosphole rings, pyrazole rings, oxazole rings, isoxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, triazine rings, carbazole rings, dibenzofuran rings, and the like.

[0053] Ar １ It is preferably a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and more preferably a substituted or unsubstituted phenyl group.

[0054] Ar １ If the molecule has substituents, the substituents that the ester bond-containing monocyclic structure may have can be preferably adopted. １ The aromatic group is preferably substituted with at least one selected from the group consisting of alkyl groups, halogeno groups, and alkoxy groups, and more preferably substituted with at least one selected from the group consisting of fluoro groups, iodo groups, methyl groups, and methoxy groups.

[0055] R １ and R ２ As a monovalent organic group having 1 to 20 carbon atoms, R Ｌ１ A monovalent organic group having 1 to 20 carbon atoms, represented by R, can be suitably used. １It is preferable that it is a monovalent organic group having 1 to 20 carbon atoms.

[0056] R １ If R is a hydrogen atom, ２ Ar １ Accordingly, R ２ The carbon atoms and Ar that are bonded to it １ Examples of ring structures formed together include alicyclic structures having 4 to 20 carbon atoms (hereinafter also referred to as "alicyclic structure (a)"). Examples of alicyclic structures having 4 to 20 carbon atoms include alicyclic hydrocarbon structures having 4 to 20 carbon atoms, and aliphatic heterocyclic structures having a divalent heteroatom-containing linking group between the carbon atoms of the alicyclic hydrocarbon structure. Examples of the above alicyclic hydrocarbon structures having 4 to 20 carbon atoms include R such as formula (T-1) above. Ｌ１ Among the monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms shown in [reference], structures corresponding to those with 4 to 20 carbon atoms can be suitably adopted. ２ and Ar １ The ring structure formed by the above is preferably a cycloalkane structure having 4 to 20 carbon atoms, more preferably a cycloalkane structure having 5 to 10 carbon atoms, and even more preferably a cyclopentane structure or a cyclohexane structure. In this case, the above alicyclic structure (a) and Ar １ The edges (two carbon-carbon bonds) shared in the fused ring with the aromatic structure are Ar １ Regardless of the π-electron conjugated system, it is treated as a single bond.

[0057] R １ and R ２ Each of these groups is preferably a monovalent linear hydrocarbon group having 1 to 10 carbon atoms, more preferably a monovalent linear saturated hydrocarbon group having 1 to 6 carbon atoms, and even more preferably a monovalent linear saturated hydrocarbon group having 1 to 4 carbon atoms, with methyl and ethyl groups being particularly preferred.

[0058] L １ As a divalent linking group represented by the above formula (T-1), L ２ A divalent linking group represented by L can be suitably adopted. １ As such, a single bond or an arenediyl group is preferred, and a single bond or a benzenediyl group is more preferred. １The divalent linking group represented by preferably does not have a hydroxyl group.

[0059] While there are no particular limitations on specific examples of monomeric compounds that give structural unit (II), examples include compounds represented by the following formula. In the following formula, R ３ This is equivalent to equation (1) above.

[0060]

[0061]

[0062]

[0063] The lower limit of the content of structural unit (II) in the total structural units constituting the polymer (the total content if multiple types exist) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural unit (II) within the above range, the radiation-sensitive composition can suitably exhibit good sensitivity, CDU, process window, and development defect suppression during pattern formation.

[0064] (Structural Unit (III)) Structural unit (III) is a structural unit having a phenolic hydroxyl group (however, it is different from structural unit (II)). Structural unit (III) contributes to improved etching resistance and improved difference in developer solubility between exposed and unexposed areas (dissolution contrast). It can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as KrF excimer lasers, electron beams, and EUV.

[0065] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0066] (In the above formula (4), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ or -O- or -CONR'- ＊* indicates a bond on the aromatic ring side. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxy group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４ m is an integer between 0 and 8, where 1 ≤ m ３ +m ４ ≤ 2n ３ (Saves +5.)

[0067] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (III), it is preferable that the atom is a hydrogen atom or a methyl group.

[0068] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0069] R １０２ In this mixture, fluorine or iodine atoms are preferred as halogen atoms.

[0070] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0071] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0072] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0073] The above structural unit (III) is preferably a structural unit represented by the following formula. In the following formula, R β This is the same as equation (4) above.

[0074]

[0075]

[0076] The lower limit of the content of structural unit (III) in the total structural units constituting the polymer (the total content if multiple types exist) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the above content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of structural unit (II) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast.

[0077] (Structural Unit (IV)) Structural unit (IV) is a structural unit containing a polar group (however, it differs from other structural units). The solubility of the base polymer in the developer can be adjusted by further containing structural unit (IV). Examples of the above polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, sulfo groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and carboxyl groups are more preferred.

[0078] Examples of structural units (IV) include structural units represented by the following formula.

[0079]

[0080]

[0081] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0082] When the base polymer has the above-mentioned structural unit (IV), the lower limit of the content of structural unit (IV) (total content if multiple types exist) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of structural unit (IV) within the above range, the solubility of the base polymer in the developer can be efficiently adjusted.

[0083] (Structural Unit (V)) The base polymer may contain a structural unit (V) having an acid-dissociable group (however, it is different from the structural unit (II)). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, etc., and dissociates by the action of an acid. The acid generated from the radiation-sensitive acid generator or the structural unit (VIIIa) of the polymer upon exposure dissociates the acid-dissociable group in the structural unit (V) to generate a carboxy group or the like. As a result, a difference in solubility in the developer between the exposed and unexposed portions of the resist film occurs, enabling pattern formation.

[0084] The structural unit (V) is not particularly limited as long as it has an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having an ester moiety derived from a secondary alcohol having an aromatic ring group and an aliphatic hydrocarbon group, a structural unit having a structure in which a hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, a structural unit having an acetal bond, and the like. From the viewpoint of improving the pattern-forming property of the radiation-sensitive composition, the structural unit represented by the following formula (3) (hereinafter, also referred to as "structural unit (V-1)") is preferable.

[0085]

[0086] In the above formula (3), R １７ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R １８ is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. R １９ and R ２０ are each independently a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or these groups are combined with each other to represent a divalent alicyclic group having 3 to 20 carbon atoms formed together with the carbon atom to which they are bonded. L １１ is ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ COO- represents. L １１ａ* is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

[0087] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (V-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0088] L １１ａ The alkanediyl group and arenediyl group represented by the above formula (T-1) are L ２ The alkanediyl group and arenediyl group shown in the above can be suitably adopted, respectively.

[0089] L １１ａ As substituents that the arenediyl group represented by can have, substituents that the above-mentioned ester bond-containing monocyclic structure can have can be suitably adopted.

[0090] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (T-1), R Ｌ１ Monovalent hydrocarbon groups having 1 to 20 carbon atoms, as shown in the above, can be suitably used.

[0091] The above R １８ Preferably, the hydrocarbon group is a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0092] The above R １９ and R ２０ When these are combined with each other, the divalent alicyclic group having 3 to 20 carbon atoms, which is formed together with the carbon atoms to which they are bonded, is R such as in the above formula (T-1). Ｌ１ A group obtained by removing one hydrogen atom from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, as shown above, can be suitably adopted.

[0093] Among these, R １８ R is an alkyl group or alkenyl group having 1 to 4 carbon atoms. １９ and R ２０ It is preferable that the alicyclic structure formed by combining these elements with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure.

[0094] The above R １８ ~R ２０ As substituents that can be present, substituents that can be present in the above-mentioned ester bond-containing monocyclic structure can be suitably adopted.

[0095] Examples of structural units (V-1) include those represented by the following formulas (3-1) to (3-12) (hereinafter also referred to as "structural units (V-1-1) to (V-1-12)").

[0096]

[0097] In the above equations (3-1) to (3-12), R １７ ~R ２０ This is equivalent to equation (3) above. R Ｌ１１ R is a halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or alkoxy group. i and j are each independently integers from 1 to 4. k and l are 0 or 1. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0098] i and j are preferably 1 or 2. １８ Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, and phenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group.

[0099] Furthermore, the polymer may contain structural units (V) represented by the following formulas (1f) to (2f).

[0100]

[0101] In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １is an integer between 1 and 4.

[0102] The above R βｆ Preferably, the element is a hydrogen atom, a methyl group, or an ethyl group. H1 is preferably 1 or 2.

[0103] When the base polymer contains structural unit (V), the lower limit of the content of structural unit (V) in relation to all structural units constituting the base polymer (the total content if multiple types exist) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of structural unit (V) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0104] (Structural Unit (VI)) The base polymer may contain structural units having fluorinated chain hydrocarbon groups (different from structural units (I) to (V)). This allows for surface modification of the resist film and control of the distribution of the film's composition during EUV exposure.

[0105] The structural unit (VI) is preferably a structural unit represented by the following formula (5).

[0106]

[0107] In the above formula (5), R １３ This is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ It consists of a single bond, an alkanediyl group with 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, and -SO ２ ONH-, -CONH-, -OCONH-, or a combination thereof. １４ This is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0108] The above R １３ From the viewpoint of copolymerization of monomers that give structural unit (VI), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0109] The above G ＬFrom the viewpoint of copolymerization of monomers that provide structural units (VI), single bonds and -COO- are preferred, and -COO- is more preferred.

[0110] The above R １４ Examples of monovalent fluorinated linear hydrocarbon groups having 1 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0111] The above R １４ Examples of monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0112] The above R １４ Preferably, the group is a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0113] When the base polymer has structural units (VI), the lower limit of the content of structural units (VI) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0114] (Structural Unit (VII)) The base polymer may contain structural units (different from structural units (I) to (VII)) having fluorinated chain hydrocarbon groups that can be soluble in alkali. This allows for surface modification of the resist film and control of the distribution of the film composition during EUV exposure, as well as improved solubility in alkaline developers and suppression of development defects.

[0115]

[0116] Structural units (VII) can be broadly classified into two types: (x) those having an alkali-soluble group, and (y) those having a group that dissociates under the action of alkali, increasing its solubility in an alkaline developer (hereinafter also simply referred to as an "alkali-dissociable group"). In both (x) and (y), in the above formula (f-2), R Ｃ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ R is a single bond, a (s+1) valent hydrocarbon group with 1 to 20 carbon atoms, and this hydrocarbon group Ｅ At the end of the side are an oxygen atom, a sulfur atom, and -NR ｄｄ -A structure to which a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms of this hydrocarbon group are substituted by an organic group having a heteroatom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

[0117] If structural unit (VII) has (x) an alkali-soluble group, R Ｆ A is a hydrogen atom, １ The oxygen atom is -COO-* or -SO ２ It is O-*. * is R Ｆ This indicates the binding site. １ This is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ If is an oxygen atom, W １ is A １ It is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which it is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. Having (x) an alkali-soluble group in structural unit (VII) increases its affinity for alkaline developer and suppresses development defects. A is an example of structural unit (VII) having an alkali-soluble group. １ is an oxygen atom and W １It is particularly preferable that the group is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0118] If structural unit (VII) has an alkali-dissociable group, R Ｆ A is a monovalent organic group having 1 to 30 carbon atoms. １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-*, or -SO ２ It is O-*. ａａ * is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Ｆ This indicates the binding site. １ R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ A is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ -COO-*, -OCO-*, or -SO ２ If it is O-*, then W １ Or R Ｆ is A １ It has a fluorine atom on the carbon atom bonded to it or on an adjacent carbon atom, or R Ｆ A is a perfluoroalkylaryl group. １ If is an oxygen atom, W １ , R Ｅ It is a single bond, R Ｄ R is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ It is a structure in which a carbonyl group is bonded to the terminal end, R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. The presence of a (y) alkali-dissociable group in structural unit (VII) causes the resist film surface to change from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. Examples of structural unit (VII) having a (y) alkali-dissociable group include A １ is -COO-*, R Ｆ Or W １Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0119] R Ｃ From the viewpoint of copolymerizability of monomers that provide structural unit (VII), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0120] When a high-fluorine-content polymer has structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0121] (Structural Unit (VIII)) Structural unit (VIII) includes an acid-generating structure which is an onium salt structure having an organic acid anion and an onium cation, and which generates acid upon exposure. This acid-generating structure functions as a radiation-sensitive acid-generating structure or an acid diffusion-controlling structure. When the acid-generating structure of structural unit (VIII) functions as a radiation-sensitive acid-generating structure, it is also called structural unit (VIIIa), and when it functions as an acid diffusion-controlling structure, it is also called structural unit (VIIIb). The distinction between these functions is determined by the organic acid anion. Each structural unit is described below.

[0122] (Structural Unit (VIIIa)) Structural unit (VIIIa) includes a first acid-generating structure. The first acid-generating structure has a first organic acid anion and a first onium cation, and generates an acid that dissociates the above-mentioned dissociable structure or acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (i.e., the first acid-generating structure) functions as a radiation-sensitive acid-generating structure. Because the base polymer contains the above-mentioned radiation-sensitive acid-generating structure, the polarity of the base polymer in the exposed area increases, making it soluble in the developer in the case of alkaline aqueous solution development, while it becomes sparingly soluble in the developer in the case of organic solvent development.

[0123] The form in which the first organic acid anion and the first onium cation are contained in the structural unit (VIIIa) of the base polymer is not particularly limited, and the base polymer may have the first organic acid anion as a side chain portion, or it may have the first onium cation as a side chain portion. Having it as a side chain portion means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. When the first organic acid anion is bonded to the main chain as a side chain structure of the base polymer, the first onium cation is ionically bonded to the first organic acid anion as its counterion. On the other hand, when the first onium cation is bonded to the main chain as a side chain structure of the base polymer, the first organic acid anion is ionically bonded to the first onium cation as its counterion. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer has the first organic acid anion as a side chain portion.

[0124] The above-mentioned first organic acid anion preferably has at least one selected from the group consisting of sulfonic acid anions, carboxylic acid anions, and sulfonimide anions as the acid anion portion. As for the acid generated by exposure, sulfonic acid, carboxylic acid, and sulfonimide can be cited, corresponding to the above-mentioned acid anion portion.

[0125] The above-mentioned first organic acid anion preferably includes, as a structure other than the acid anion portion, -O-, -CO-, a cyclic structure, or a combination thereof. This combination also includes structures (heterocyclic structures) in which -O- or -CO- are incorporated as ring-forming parts within the cyclic structure.

[0126] The cyclic structure may be monocyclic, polycyclic, or a combination thereof. Furthermore, the cyclic structure may be alicyclic, aromatic, heterocyclic, or a combination thereof. In the case of a combination, the cyclic structures may be linked by chain structures, and two or more cyclic structures may form fused ring structures, bridged ring structures, or spiro-ring structures. Divalent heteroatom-containing linking groups may exist between the carbon atoms forming the skeleton of 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 with other substituents.

[0127] The above alicyclic structure is R such as the above formula (T-1). Ｌ１ Structures corresponding to monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, as shown in [reference], can be suitably adopted.

[0128] The above aromatic ring structure is Ar as shown in formula (1) above. １ The aromatic hydrocarbon rings and aromatic heterocycles shown in the above can be suitably used.

[0129] Examples of the above heterocyclic structures include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thiethane, thiolane, and thian; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan and benzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, and triazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0130] Heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetals, or combinations thereof.

[0131] The above chain-like structure is R in formula (3) above. １９ and R ２０A structure corresponding to a monovalent chain hydrocarbon group having 1 to 10 carbon atoms can be suitably adopted.

[0132] As substituents that substitute for some or all of the hydrogen atoms on the carbon atoms of the above-mentioned cyclic or chain-like structure, substituents that the above-mentioned ester bond-containing monocyclic structure may have can be suitably adopted.

[0133] In the above-described first acid generation structure, the first organic acid anion preferably has a sulfonic acid anion as the acid anion portion, and an electron-withdrawing group is preferably bonded to the carbon atom at the α or β position of the sulfur atom in the sulfonic acid anion. This allows the first acid generation structure to efficiently exhibit the above-described function. Examples of electron-withdrawing groups include fluorine atoms, fluorinated hydrocarbon groups, nitro groups, and cyano groups. Preferred fluorinated hydrocarbon groups are difluoromethyl groups and perfluoroalkyl groups having 1 to 5 carbon atoms.

[0134] The above-mentioned first organic acid anion preferably has an iodine group. The above-mentioned first organic acid anion preferably contains an iodine group-containing aromatic ring structure as the form of iodine group inclusion. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are replaced by iodine groups. As the aromatic ring, the above-mentioned aromatic ring structure in the above-mentioned first organic acid anion can be suitably adopted.

[0135] Examples of the first onium cation mentioned above include radiodegradable onium cations. Examples of radiodegradable onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0136] The first onium cation described above preferably has an iodine group. The first onium cation preferably contains the iodine group-containing aromatic ring structure described above as the form in which the iodine group is contained.

[0137] The first onium cation in structural unit (VIIIa) is preferably a fluorogroup-containing onium cation having a fluorogroup together with or in place of an iodine group. The fluorogroup-containing onium cation preferably has a fluorogroup-containing aromatic ring structure. The fluorogroup-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are replaced with fluorogroups. As the aromatic ring in the fluorogroup-containing aromatic ring structure, the aromatic ring in the iodine group-containing aromatic ring structure can be suitably adopted. This can improve sensitivity by increasing the radiation absorption efficiency.

[0138] The structural unit (VIIIa) can efficiently perform the above-mentioned functions by combining the above-mentioned structures.

[0139] The structural unit (VIIIa) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (VIIIa-1)").

[0140]

[0141] In the formula, R Ｖ This is a hydrogen atom or a methyl group. V １ This is a single bond or an ester group. V ２ This is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, or an amide bond, and a portion of the methylene groups constituting the alkylene group, the cycloalkylene group, or the arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ This is a single bond, an ether group, an ester group, or a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and a portion of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３ Some or all of the hydrogen atoms in the compound may be substituted with heteroatoms, or with monovalent hydrocarbon groups having 1 to 20 carbon atoms that may contain heteroatoms. Rf １ ~Rf２ Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is a fluorine atom or a fluorinated hydrocarbon group. kk is an integer from 1 to 4. X １ ＋ This is a sulfonium cation or an iodonium cation.

[0142] V ２ and V ３ The C1-C20 monovalent hydrocarbon group in this is preferably a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C6-C20 aryl group. Some or all of the hydrogen atoms in these groups may be substituted with heteroatom-containing groups such as hydroxyl groups, carboxyl groups, halogen atoms, oxo groups, cyano groups, amide groups, nitro groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, alkoxy groups, or alkoxycarbonyl groups. Some of the methylene groups constituting these groups may be substituted with ether groups, ester groups, carbonyl groups, carbonate groups, or sulfonic acid ester groups.

[0143] The structural unit (VIIIa-1) is preferably a structural unit represented by the following formula (a1-1).

[0144]

[0145] In the formula, R Ｖ , Rf １ ~Rf ２ , V １ ,kk and X １ ＋ This is equivalent to the above formula (a1). R ４８ This is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxyl group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. ma is an integer from 0 to 4. na is an integer from 0 to 3.

[0146] Examples of the first organic acid anion of the monomer that gives structural unit (VIIIa) (including structural unit (VIIIa-1)) include, but are not limited to, the structure shown in the following formula. In the following, the iodine group of the iodine group-containing aromatic ring structure may be replaced with a hydrogen atom or a substituent that the above ester bond-containing monocyclic structure may have.

[0147]

[0148]

[0149]

[0150]

[0151] In the above formula, R Ｖ This is equivalent to equation (a1) above.

[0152] X in the above formula (a1) １ ＋ Preferably, it is a sulfonium cation represented by the following formula (Q-1).

[0153]

[0154] In the above formula (Q-1), Ra1 and Ra2 each independently represent substituents. n1 represents an integer from 0 to 5, and if n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer from 0 to 5, and if n2 is 2 or greater, multiple Ra2s may be the same or different. Ra3 represents a substituent. n3 represents an integer from 0 to 5, and if n3 is 2 or greater, multiple Ra3s may be the same or different. Ra1 and Ra2 may be linked to each other to form a ring. If n1 is 2 or greater, multiple Ra1s may be linked to each other to form a ring. If n2 is 2 or greater, multiple Ra2s may be linked to each other to form a ring.

[0155] Preferred substituents represented by Ra1, Ra2, and Ra3 are alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, alkylsulfonyl groups, hydroxyl groups, halogen atoms, and halogenated hydrocarbon groups.

[0156] The alkyl groups Ra1 and Ra2 may be linear or branched alkyl groups. Preferably, these alkyl groups have 1 to 10 carbon atoms, and examples include methyl, ethyl, n-propyl, i-propyl, n-butyl, 2-methylpropyl, 1-methylpropyl, t-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl groups. Of these, methyl, ethyl, n-butyl, and t-butyl groups are particularly preferred.

[0157] Examples of cycloalkyl groups for Ra1 and Ra2 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Of these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0158] Examples of the alkyl groups of the alkoxy groups of Ra1 and Ra2 include those previously listed as alkyl groups of Ra1 and Ra2. Methoxy, ethoxy, n-propoxy, and n-butoxy groups are particularly preferred as alkoxy groups.

[0159] Examples of the cycloalkyl group portions of Ra1 and Ra2 include those previously listed as cycloalkyl groups of Ra1 and Ra2. Cyclopentyloxy and cyclohexyloxy groups are particularly preferred as these cycloalkyl groups.

[0160] Examples of the alkoxy carbonyl groups of Ra1 and Ra2 include those previously listed as alkoxy groups of Ra1 and Ra2. Methoxycarbonyl groups, ethoxycarbonyl groups, and n-butoxycarbonyl groups are particularly preferred as alkoxycarbonyl groups.

[0161] Examples of the alkyl group portion of the alkylsulfonyl groups of Ra1 and Ra2 include those previously listed as alkyl groups of Ra1 and Ra2. Similarly, examples of the cycloalkyl group portion of the cycloalkylsulfonyl groups of Ra1 and Ra2 include those previously listed as cycloalkyl groups of Ra1 and Ra2. Among these alkylsulfonyl groups or cycloalkylsulfonyl groups, methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl groups are particularly preferred.

[0162] Each of the Ra1 and Ra2 groups may have further substituents. Examples of such substituents include halogen atoms such as fluorine atoms (preferably fluorine atoms), hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkoxy groups, cycloalkyloxy groups, alkoxyalkyl groups, cycloalkyloxyalkyl groups, alkoxycarbonyl groups, cycloalkyloxycarbonyl groups, alkoxycarbonyloxy groups, and cycloalkyloxycarbonyloxy groups.

[0163] Examples of halogen atoms for Ra1 and Ra2 include fluorine, chlorine, bromine, and iodine atoms, with fluorine and iodine atoms being preferred.

[0164] As the halogenated hydrocarbon groups of Ra1 and Ra2, halogenated alkyl groups are preferred. The alkyl groups and halogen atoms constituting the halogenated alkyl groups are the same as those described above. Among these, fluorinated alkyl groups are preferred, and CF ３ This is preferable.

[0165] As described above, Ra1 and Ra2 may be linked to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 are linked to each other to form a single bond or a divalent linking group. Examples of divalent linking groups include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２-, alkylene group, cycloalkylene group, alkenylene group, or combination of two or more of these, preferably with a total carbon number of 20 or less. When Ra1 and Ra2 are linked to each other to form a ring, Ra1 and Ra2 are linked to each other as -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ - or single bond formation is preferable. Among these, -O-, -S-, or single bond formation is more preferable, and single bond formation is particularly preferable. Furthermore, when n1 is 2 or more, multiple Ra1s may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2s may be linked to each other to form a ring. An example of such a configuration is one in which two Ra1s are linked to each other and form a naphthalene ring together with the benzene ring to which they are linked.

[0166] Ra3 is preferably a fluorine atom, a group having one or more fluorine atoms, or an iodine atom. Examples of groups having fluorine atoms include alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, and alkylsulfonyl groups, which are substituted with fluorine atoms as Ra1 and Ra2. Among these, fluorinated alkyl groups are particularly preferred, and CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ ,CH ２ CF ３ ,CH ２ CH ２ CF ３ ,CH ２ C ２ F ５ ,CH ２ CH ２ C ２ F ５ ,CH ２ C ３ F７ ,CH ２ CH ２ C ３ F ７ ,CH ２ C ４ F ９ and CH ２ CH ２ C ４ F ９ The following can be more preferably listed: CF ３ The following can be particularly preferred.

[0167] Ra3 is a fluorine atom, an iodine atom, or CF ３ It is preferable that it be a fluorine atom or an iodine atom.

[0168] n1 and n2 are each independently preferably integers between 0 and 3, and preferably integers between 0 and 2.

[0169] n3 is preferably an integer between 1 and 3, and more preferably 1 or 2.

[0170] (n1 + n2 + n3) is preferably an integer from 1 to 15, more preferably an integer from 1 to 9, even more preferably an integer from 2 to 6, and particularly preferably an integer from 3 to 6. When (n1 + n2 + n3) is 1, n3 = 1 and Ra3 is a fluorine atom, an iodine atom, or CF ３ It is preferable that (n1 + n2 + n3) is 2, then n1 = n3 = 1 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ The combinations are as follows, and n3=2 and Ra3 is a fluorine atom, an iodine atom or CF ３ The following combinations are preferred. When (n1 + n2 + n3) is 3, n1 = n2 = n3 = 1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ The following combinations are preferred. When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom or CF ３ The following combinations are preferred. When (n1 + n2 + n3) is 5, n1 = n2 = 1 and n3 = 3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３The combination is such that n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ The combinations are as follows: n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF ３ The following combinations are preferred. When (n1 + n2 + n3) is 6, n1 = n2 = n3 = 2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ The combination is preferable.

[0171] Specific examples of the sulfonium cation represented by the above formula (Q-1) include the structure represented by the following formula. The fluorine atom and iodine atom in the sulfonium cation below may be substituted with hydrogen atoms or substituents that the above ester bond-containing monocyclic structure may have.

[0172]

[0173]

[0174]

[0175]

[0176] The first onium cation of structural unit (VIIIa) may be a diaryliodonium cation. The diaryliodonium cation preferably has one or more fluorine or iodine atoms. At least one of the aryl groups of the iodonium cation preferably has a fluorogroup-containing aromatic ring structure or an iodogroup-containing aromatic ring structure. A phenyl group is preferred as the aryl group.

[0177] In this configuration, a first onium cation is bonded to the main chain as the side chain structure of the base polymer, and a first organic acid anion is ionically bonded to the first onium cation as its counterion. In this case, the first onium cation is bonded to the main chain via a divalent linking group or a single bond, and V in formula (a1) is formed. ２ From SO ３ -It is preferable that the structure up to this point is ionically bonded to the first onium cation as a counterion. The divalent linking group is L such as the above formula (T-1). ２ A divalent linking group represented by can be suitably adopted.

[0178] When the base polymer contains structural unit (VIIIa), the lower limit of the content of structural unit (VIIIa) (total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 10 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol% or less. By setting the content of structural unit (VIIIa) within the above range, the function as an acid-generating structure can be fully exhibited, and the above resist properties can be achieved.

[0179] The monomer that gives structural unit (VIIIa-1) can be synthesized, for example, by the same method as the sulfonium salt having a polymerizable anion described in Japanese Patent Publication No. 5201363.

[0180] (Structural Unit (VIIIb)) The base polymer may include a structural unit (VIIIb) having a second organic acid anion and a second onium cation, which generates an acid upon exposure that does not dissociate the dissociable structure or the acid-dissociable group. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid-generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the radiation-sensitive composition, the second acid-generating structure substantially prevents the dissociable structure of structural unit (II) or the acid-dissociable group of structural unit (V) from dissociating, and has the function of suppressing the diffusion of acid generated from the first acid-generating structure or the radiation-sensitive acid-generating agent (if included) in the unexposed area by salt exchange. The acid generated from the second acid-generating structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the first acid-generating structure or the radiation-sensitive acid-generating agent.

[0181] The above-mentioned second organic acid anion preferably has a sulfonic acid anion or a carboxylic acid anion as the acid anion portion. In the case of a sulfonic acid anion, it is preferable that no electron-withdrawing group is bonded to either the α-position or the β-position carbon atom of the sulfur atom in the sulfonic acid anion.

[0182] As for the structure of the second organic acid anion other than the acid anion portion, the structure of the first organic acid anion other than the acid anion portion can be suitably adopted.

[0183] Examples of secondary organic acid anions that give structural unit (VIIIb) are, but are not limited to, those listed below. Note that all of the secondary organic acid anions listed below have an iodine group or a hydroxyl group, but structural unit (VIIIb) does not necessarily require an iodine group or a hydroxyl group. As secondary organic acid anions that do not have an iodine group or a hydroxyl group, structures in which the iodine group or hydroxyl group in the following formula is replaced with a hydrogen atom or a substituent that the above-mentioned ester bond-containing monocyclic structure may have can be suitably adopted. It is preferable that the secondary organic acid anion has a carboxylic acid anion and a hydroxyl group. In this case, it is preferable that the carboxylic acid anion and the hydroxyl group are bonded to the same aromatic ring in the secondary organic acid anion, and it is more preferable that the carbon atom to which the carboxylic acid anion is bonded and the carbon atom to which the hydroxyl group is bonded are directly connected to each other in the same aromatic ring.

[0184]

[0185]

[0186]

[0187] In the formula, R A This is either a hydrogen atom or a methyl group.

[0188] As the second onium cation of structural unit (VIIIb), the sulfonium cation represented by the above formula (Q-1) can be suitably adopted.

[0189] In this configuration, a secondary onium cation is bonded to the main chain as the side chain structure of the base polymer, and a secondary organic acid anion is ionically bonded to the secondary onium cation as its counterion. In this case, it is preferable that the secondary onium cation is bonded to the main chain via a divalent linking group or a single bond, and that the structure of the secondary organic acid anion, excluding the polymerizable group (the structure corresponding to the ethylenically unsaturated bond in the above formula), is ionically bonded to the secondary onium cation as its counterion. The divalent linking group can be L such as the one in formula (T-1). ２ A divalent linking group represented by can be suitably adopted.

[0190] When the base polymer contains structural unit (VIIIb), the lower limit of the content of structural unit (VIIIb) (or the total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 10 mol%. By setting the content of structural unit (VIIIb) within the above range, the structure can fully exhibit its function as an acid diffusion control structure.

[0191] (Other structural units) The polymer may also contain structural units derived from styrene or iodostyrene (hereinafter also referred to as "structural units (IX)") as other structural units. When the base polymer has structural units (IX) having the polar group, the lower limit of the content of structural units (IX) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the content is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%.

[0192] (Method for synthesizing base polymers) Base polymers can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0193] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight-average molecular weight (Mw) in polystyrene terms, calculated by gel permeation chromatography (GPC), is preferably 1,000, more preferably 2,000, and even more preferably 2,500. The upper limit of Mw is preferably 20,000, more preferably 16,000, and even more preferably 12,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0194] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0195] The methods for measuring Mw and Mn of polymers in this specification are as described in the examples.

[0196] The lower limit of the base polymer content is preferably 40% by mass, more preferably 50% by mass, and even more preferably 60% by mass, relative to the total solid content of the radiation-sensitive composition. The upper limit of the above content is preferably 95% by mass, and more preferably 90% by mass.

[0197] (Other Polymers) The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer with a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, it can be unevenly distributed on the surface of the resist film relative to the base polymer, and as a result, surface modification of the resist film and control of the distribution of the film composition during EUV exposure can be achieved.

[0198] The high-fluorine-content polymer preferably contains structural unit (VII) of the base polymer. The high-fluorine-content polymer preferably further contains structural unit (III) or (IV) of the base polymer.

[0199] When a high-fluorine-content polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 60 mol%, and more preferably 70 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content may be 100 mol%, but is preferably 90 mol%.

[0200] When a high-fluorine-content polymer contains structural unit (III), the lower limit of the content of structural unit (III) is preferably 8 mol%, and more preferably 15 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 40 mol%, and more preferably 30 mol%.

[0201] When a high-fluorine-content polymer contains structural units (IV), the lower limit of the structural unit (IV) content is preferably 8 mol%, and more preferably 15 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 40 mol%, and more preferably 30 mol%.

[0202] The lower limit of Mw for the high-fluorine-content polymer is preferably 6,000, more preferably 7,000, and even more preferably 8,000. The upper limit of Mw is preferably 20,000, more preferably 14,000, and even more preferably 12,000.

[0203] The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, and 1.1 is more preferred. The upper limit of Mw / Mn is usually 5, 3 is preferred, and 2 is more preferred.

[0204] When the radiation-sensitive composition contains a high-fluorine content polymer, the lower limit of the percentage of the high-fluorine content polymer relative to the total amount of the base polymer and the high-fluorine content polymer is preferably 1% by mass, and more preferably 3% by mass. The upper limit of the percentage is preferably 15% by mass, and more preferably 10% by mass.

[0205] (Method for synthesizing high-fluorine content polymers) High-fluorine content polymers can be synthesized by the same method as the base polymer synthesis method described above.

[0206] <Radiation-sensitive acid generator> The radiation-sensitive composition may contain a radiation-sensitive acid generator. The radiation-sensitive acid generator contains a third organic acid anion and a third onium cation, forming an onium salt structure. The radiation-sensitive acid generator is a component that generates acid upon exposure. The acid generated upon exposure has the function of dissociating the dissociable structure or acid-dissociable group of the base polymer, generating carboxyl groups, etc. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low molecular weight compound (liberated from the polymer), and is different from the radiation-sensitive acid generating structure in which the first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer, as in the structural unit (VIIIa) in the base polymer.

[0207] At least one selected from the group consisting of the above-mentioned third organic acid anion and third onium cation preferably has an iodine group, and more preferably has the above-mentioned iodine group-containing aromatic ring structure.

[0208] The structure of the third organic acid anion in the radiation-sensitive acid generator is V in formula (a1) of the base polymer. ２ From SO ３ - The following structures can be suitably adopted.

[0209] Examples of the third organic acid anion of the radiation-sensitive acid generator include, but are not limited to, the structure represented by the following formula. Furthermore, a third organic acid anion without an iodine group-containing aromatic ring structure can be used instead of the first organic acid anion having an iodine group-containing aromatic ring structure. As the third organic acid anion without an iodine group-containing aromatic ring structure, a structure in which the iodine group in the following formula is replaced with a hydrogen atom or a substituent (excluding the iodine group) that the above-mentioned ester bond-containing monocyclic structure may have can be preferably adopted.

[0210]

[0211]

[0212]

[0213] The structure of the third onium cation in the radiation-sensitive acid generator can preferably adopt the structure of the first onium cation of structural unit (VIIIa) in the above-mentioned base polymer.

[0214] The above-mentioned radiation-sensitive acid generator can also be synthesized by known methods, particularly by salt exchange reactions. Known radiation-sensitive acid generators can also be used, as long as they do not impair the effects of the present invention.

[0215] These radiation-sensitive acid generators may be used individually or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total in the case of multiple types) is preferably 20 parts by mass, more preferably 35 parts by mass, and even more preferably 50 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 100 parts by mass, more preferably 85 parts by mass, and even more preferably 70 parts by mass. This allows for excellent sensitivity, CDU, and suppression of process window development defects during resist pattern formation.

[0216] <Acid Diffusion Control Agent> The radiation-sensitive composition may contain an acid diffusion control agent. The acid diffusion control agent contains a quaternary organic acid anion and a quaternary onium cation, and generates an acid with a higher pKa than the acid generated from the radiation-sensitive acid generator or structural unit (VIIIa) in the base polymer upon irradiation with radiation. Under pattern-forming conditions using the radiation-sensitive composition, the acid diffusion control agent has the function of substantially preventing the dissociable structure or acid-dissociable group of the base polymer from dissociating, and suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in the unexposed areas by salt exchange.

[0217] By including the above-mentioned acid diffusion control agent in the radiation-sensitive composition, acid diffusion in unexposed areas can be suppressed, enabling the formation of a resist pattern with superior resolution and development contrast.

[0218] At least one selected from the group consisting of the above-mentioned fourth organic acid anion and fourth onium cation preferably has an iodine group, and more preferably has the above-mentioned iodine group-containing aromatic ring structure.

[0219] Although the structure of the above-mentioned fourth organic acid anion is not specified, it is preferable that it includes -O-, -CO-, a cyclic structure, or a combination thereof. As the cyclic structure, the cyclic structure of the above-mentioned first organic acid anion of the structural unit (VIIIa) of the base polymer can be suitably adopted.

[0220] In the acid diffusion control agent, it is preferable that the fourth organic acid anion has a sulfonic acid anion or a carboxylic acid anion as the acid anion portion (however, if the fourth organic acid anion has a sulfonic acid anion, no electron-withdrawing group is bonded to either the α-position or β-position carbon atom of the sulfur atom in the sulfonic acid anion). This allows the acid diffusion control agent to efficiently perform the above function.

[0221] The structure of the fourth organic acid anion in the acid diffusion control agent can preferably be the structure obtained by removing the polymerizable group (the structure corresponding to the ethylenically unsaturated bond in the above formula) from the structure of the second organic acid anion of the base polymer.

[0222] Examples of the fourth organic acid anion for the above-mentioned acid diffusion control agent include, but are not limited to, those listed below. Compounds containing both an iodonium cation and anion within the same molecule, and compounds containing both a sulfonium cation and anion within the same molecule are also examples. As an organic acid anion that does not have an iodine group-containing aromatic ring structure, a structure in which the iodine group in the following formula is replaced with a hydrogen atom or a substituent (excluding the iodine group) that the above-mentioned ester bond-containing monocyclic structure may have can be preferably adopted.

[0223]

[0224]

[0225] As the fourth onium cation in the above acid diffusion control agent, the structure of the first onium cation of structural unit (VIIIa) in the above base polymer can be suitably adopted.

[0226] When the quaternary onium cation is an iodonium cation, it is preferably a diaryliodonium cation. The diaryliodonium cation more preferably has one or more fluoro or iodo groups. A phenyl group is preferred as the aryl group.

[0227] The above-mentioned acid diffusion control agents can also be synthesized by known methods, particularly by salt exchange reactions.

[0228] These acid diffusion control agents may be used individually or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion control agent, the lower limit of the acid diffusion control agent content (total in the case of multiple types) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total amount of the radiation-sensitive acid generator and the monomers that, if present, give the above-mentioned structural unit (VIIIa). The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%.

[0229] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing the base polymer and optionally contained additives.

[0230] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0231] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether solvents, such as propylene glycol monomethyl ether, in which some of the hydroxyl groups of the above-mentioned polyhydric alcohol solvents are etherified. In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0232] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

[0233] Examples of ketone solvents include: linear ketone solvents such as acetone, butanone, and methyl-isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0234] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain-like amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0235] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate.

[0236] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbencene, and n-amylnaphthalene.

[0237] Among these, ester solvents, ether solvents, and alcohol solvents are preferred, polyhydric alcohol partial ether acetate solvents, polyhydric alcohol partial ether solvents, and monoalcohol solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and diacetone alcohol are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0238] <Other Optional Components> The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization accelerators, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0239] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing a base polymer and a solvent with other optional components as needed in a predetermined ratio. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 0.05 μm to 0.4 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0240] <Pattern Forming Method> The pattern forming method in this embodiment includes the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (1) (hereinafter also referred to as the "resist film forming step"), exposing the resist film to light (2) (hereinafter also referred to as the "exposure step"), and developing the exposed resist film with a developer (3) (hereinafter also referred to as the "development step").

[0241] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, CDU, process window, and development defect suppression during pattern formation is used, high-quality resist patterns can be efficiently formed. The following describes each step.

[0242] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the above-mentioned radiation-sensitive composition. Examples of substrates for forming this resist film include conventionally known materials such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective film disclosed in, for example, Japanese Patent Publication No. 6-12452 or Japanese Patent Publication No. 59-93448 may be formed on the substrate. Examples of coating methods include spin coating, casting, and roll coating. After coating, soft baking (SB) may be performed as needed to volatilize the solvent in the coating film. The SB temperature is usually 60°C to 140°C, with 80°C to 120°C being preferred. The SB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred. The thickness of the formed resist film is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0243] [Exposure Process] In this process (process (2) above), the resist film formed in the resist film formation process, which is process (1) above, is exposed by irradiating it with radiation through a photomask. The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; for example, electron beams and charged particle beams such as alpha rays. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0244] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from structural units (VIIIa) and radiation-sensitive acid generators due to the exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 60°C to 140°C, with 80°C to 120°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0245] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed with a developer. This allows a predetermined resist pattern to be formed. After development, it is common to wash with a rinsing solution such as water or alcohol and then dry it.

[0246] Examples of developers used in the above development process include, in the case of alkaline development, an alkaline aqueous solution containing at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0247] In addition, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As for ester solvents, acetic acid ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than organic solvents in the developer include water and silicone oil.

[0248] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by puddling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0249] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0250] [Measurement of weight-average molecular weight (Mw), number-average molecular weight (Mn), and degree of dispersion (Mw / Mn)] These measurements were performed by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard, under the analytical conditions of Tosoh Corporation's GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL"), with a flow rate of 1.0 mL / min, elution solvent: tetrahydrofuran, and column temperature: 40°C.

[0251] [ １ H-NMR analysis and １３ [C-NMR Analysis] Measurements were taken using JEOL's "JNM-Delta400".

[0252] <Synthesis of Polymers> The monomers used in the synthesis of each polymer in each example and comparative example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass means the value when the total mass of the monomers used is 100 parts by mass, and mol% means the value when the total number of moles of the monomers used is 100 mol%. Furthermore, the present invention is not limited to the following structural units.

[0253] The structures of the monomers that give structural units (I) among the monomers used in the synthesis of the polymers in each example are shown below.

[0254]

[0255]

[0256] The structures of the monomers that give structural unit (II) among the monomers used in the synthesis of the polymers in each example are shown below.

[0257]

[0258]

[0259] The structures of the monomers that give structural units (V) among the monomers used in the synthesis of polymers in each example are shown below.

[0260]

[0261] The structures of the monomers that give structural unit (III) among the monomers used in the synthesis of the polymers in each example are shown below.

[0262]

[0263] The structures of the monomers that give structural units (IV), (VI) to (VII) among the monomers used in the synthesis of the polymer in each example are shown below.

[0264]

[0265] [Polymer Synthesis Example 1] Compounds (A-1), (B-1), and (M-1) as monomers for the synthesis of polymer (P-1) were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) so that the molar ratio in the final polymer was 60 / 30 / 10. Next, 10 mol% of 2,2'-azobis(methyl isobutyrate) was added as an initiator relative to the total amount of monomers to prepare a monomer solution. Meanwhile, 100 parts by mass of 1-methoxy-2-propanol (relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85°C for another 3 hours to carry out the polymerization reaction for a total of 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to room temperature. The cooled polymerization solution was added to hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane in the polymerization solution, filtered again, and dissolved in 1-methoxy-2-propanol (300 parts by mass). The polymer was added dropwise to 500 parts by mass of water to coagulate, and the resulting solid was filtered off. The mixture was dried at 50°C for 12 hours to obtain a white powdery polymer (P-1). The obtained polymer (P-1) had a Mw of 5,600 and an Mw / Mn ratio of 1.4.

[0266] [Polymer Synthesis Examples 2-83] (Synthesis of Polymers (P-2) to (P-83)) Polymers (P-2) to (P-83) were obtained by blending predetermined amounts of the monomers of the types listed in Tables 1-1 and 1-2 using the same procedure as in Polymer Synthesis Example 1. The Mw and Mw / Mn of each obtained polymer are shown together in Tables 1-1 and 1-2. Polymers (P-1) to (P-74) correspond to base polymers, polymers (P-75) to (P-78) correspond to high-fluorine-content polymers, and polymers (P-79) to (P-83) correspond to comparative polymers.

[0267]

[0268]

[0269] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator, acid diffusion control agent, and solvent used to prepare the radiation-sensitive composition are shown below.

[0270] [C] Radiation-sensitive acid generators: C-1 to C-9: Compounds represented by the following formulas (C-1) to (C-9).

[0271]

[0272]

[0273] [[D] Acid diffusion control agents] D-1 to D-9: Compounds represented by the following formulas (D-1) to (D-9).

[0274]

[0275]

[0276] [E] Solvents E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: Diacetone alcohol

[0277] [Preparation of Radiation-Sensitive Composition] [Example 1] 100 parts by mass of (P-1) as a polymer, 60 parts by mass of (C-1) as a radiation-sensitive acid generator, 40 mol% of (D-1) relative to (C-1) as an acid diffusion control agent, 2,800 parts by mass of (E-1) as a solvent, and 2,000 parts by mass of (E-2) and 2,000 parts by mass of (E-3) were mixed. This mixture was filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0278] [Examples 2-94 and Comparative Examples 1-5] Radiation-sensitive compositions (R-2) to (R-94) and (CR-1) to (CR-5) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 2-1 and 2-2 below were used.

[0279]

[0280]

[0281] <Formation of Resist Pattern> On the surface of a 12-inch silicon wafer with a 20 nm thick underlayer (AL412 (manufactured by Brewer Science)) formed on it, the radiation-sensitive compositions prepared above were applied using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron). After performing a soft bake (SB) at 100°C for 60 seconds, it was cooled at 23°C for 30 seconds to form a 30 nm thick resist film. This resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film was subjected to a post-exposure bake (PEB) at 100°C for 60 seconds. Next, the film was developed using a 2.38 wt% TMAH aqueous solution at 23°C for 30 seconds to form a positive-type 50 nm pitch, 25 nm contact hole pattern.

[0282] <Evaluation> The sensitivity, CDU, process window, and number of development defects of each radiation-sensitive composition were evaluated by measuring each resist pattern formed as described below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns. The evaluation results are shown in Tables 3-1 and 3-2 below.

[0283] [Sensitivity] In forming the resist pattern described above, the exposure amount used to form the 25 nm contact hole pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 40 mJ / cm². A smaller value indicates better sensitivity. ２ If the value is less than 40 mJ / cm², it is classified as "A" (very good). ２ More than 42mJ / cm ２ The following cases are classified as "B" (good), 42 mJ / cm². ２ If it exceeded this value, it was judged as "C" (defective).

[0284] [CDU Performance] A 25-nm contact hole pattern was formed by irradiating the optimum exposure dose obtained in the above sensitivity evaluation. The formed resist pattern was observed from the top of the pattern using the above scanning electron microscope. The variation in hole diameter was measured at a total of 600 points, and the 3-sigma value was obtained from the distribution of the measured values. This 3-sigma value was defined as CDU (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better performance. When the CDU was less than 2.8 nm, it was judged as "A" (extremely good); when it was 2.8 nm or more and 3.0 nm or less, it was judged as "B" (good); and when it exceeded 3.0 nm, it was judged as "C" (bad).

[0285] [Process Window] Using a mask for forming a 25-nm contact hole pattern, patterns were formed by changing the exposure dose from a low exposure dose to a high exposure dose. Generally, on the low exposure dose side, connection between patterns can be seen, and on the high exposure dose side, defects such as pattern breakage can be seen. The difference between the upper limit value and the lower limit value of the resist dimension where these defects are not seen was defined as "CD (Critical Dimension) margin". When the CD margin was 6.0 nm or more, it was judged as "A" (extremely good); when it was 4.0 nm or more and less than 6.0 nm, it was judged as "B" (good); and when it was less than 4.0 nm, it was judged as "C" (bad).

[0286] [Number of Development Defects] The resist film was exposed at the optimum exposure dose to form a 25-nm contact hole pattern, which was used as a wafer for defect inspection. The number of defects on this defect inspection wafer was measured using a defect inspection apparatus ("KLA2810" manufactured by KLA-Tencor). Then, the measured defects were classified into those determined to be from the resist film and foreign substances from the outside. When the number of defects determined to be from the resist film after development was less than 30, it was judged as "A" (extremely good); when it was 30 or more and 50 or less, it was judged as "B" (good); and when it exceeded 50, it was judged as "C" (bad).

[0287]

[0288]

[0289] As is clear from the results in Tables 3-1 and 3-2, the radiation-sensitive compositions of Examples 1 to 94 exhibited a good balance of sensitivity, CDU, process window, and development defect suppression compared to the radiation-sensitive compositions of Comparative Examples 1 to 5.

[0290] The radiation-sensitive composition and pattern-forming method of the present invention improve sensitivity, CDU, process window, and development defect suppression during pattern formation. Therefore, these can be suitably used for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A radiation-sensitive composition containing a polymer and a solvent, wherein the polymer contains a structural unit (I) containing a monocyclic structure having an ester bond, a structural unit (II) derived from a compound represented by the following formula (1), and a structural unit (III) having a phenolic hydroxyl group. (In formula (1), Ar １ is a monovalent aromatic group having 3 to 20 carbon atoms, which may be substituted or unsubstituted. R １ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ２ is a monovalent organic group having 1 to 20 carbon atoms, or when R １ is a hydrogen atom, R ２ is bonded to Ar １ and forms a ring structure together with the carbon atom to which R ２ is bonded and Ar １ . R ３ is a hydrogen atom, a halogeno group, or a monovalent organic group having 1 to 20 carbon atoms. L １ is a single bond or a divalent linking group.) 2. The radiation-sensitive composition according to claim 1, wherein the ester bond-containing monocyclic structure is a monocyclic lactone structure.

3. In the above formula (1), R １ The radiation-sensitive composition according to claim 1, wherein is a monovalent organic group having 1 to 20 carbon atoms.

4. In the above formula (1), R １ and R ２ The radiation-sensitive composition according to claim 1, wherein each of them is independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms.

5. In the above formula (1), Ar １ The radiation-sensitive composition according to claim 1, wherein is a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

6. In the above formula (1), Ar １ The radiation-sensitive composition according to claim 1, wherein the aromatic group is substituted with at least one selected from the group consisting of alkyl groups, halogeno groups, and alkoxy groups.

7. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the content of structural unit (I) in the total structural units constituting the polymer is 2 mol% or more and 70 mol% or less.

8. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the content of structural unit (II) in the total structural units constituting the polymer is 10 mol% or more and 80 mol% or less.

9. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the content of structural unit (III) in the total structural units constituting the polymer is 5 mol% or more and 60 mol% or less.

10. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the polymer further comprises a structural unit having an organic acid anion and an onium cation, and including an acid-generating structure that generates acid upon exposure.

11. The radiation-sensitive composition according to any one of claims 1 to 6, further comprising a high-fluorine-content polymer having a higher mass content of fluorine atoms than the polymer described above.

12. A pattern forming method comprising the steps of: applying a radiation-sensitive composition according to any one of claims 1 to 6 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

13. The pattern forming method according to claim 12, wherein the exposure is performed using extreme ultraviolet light or an electron beam.

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