Radiation-sensitive composition and pattern formation method

Abstract

Provided are a radiation-sensitive composition and a pattern formation method capable of exhibiting sensitivity, CDU performance, and LWR performance at a sufficient level when a resist pattern is formed using next-generation technology. In the present invention, a radiation-sensitive composition contains: a polymer including structural units having an acid-dissociable group; a radiation-sensitive acid generator containing a first organic acid anion and a first onium cation; an acid diffusion control agent that contains a second organic acid anion and a second onium cation, and generates an acid having a higher pKa than an acid generated from the radiation-sensitive acid generator under exposure to radiation; and a solvent. The first organic acid anion contains an acid anion moiety and an aromatic ring having at least both a first substituent and a second substituent. The first substituent and the second substituent are each independently a hydroxy group, a sulfo group, or a sulfanyl group. At least one selected from the group consisting of the polymer, the radiation-sensitive acid generator, and the acid diffusion control agent contains an iodo 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 techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the polymer in an alkaline or organic solvent-based developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] In the photolithography technology, pattern miniaturization is promoted by using short-wavelength radiation such as an ArF excimer laser or by combining this radiation with liquid immersion lithography. As a next-generation technology, the use of even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is being promoted, and improvements in the performance of resist materials used for exposure to such radiation are being studied (Japanese Patent Laid-Open No. 2020-075910).

[0004] Japanese Patent Application Laid-Open No. 2020-075910

[0005] The above-mentioned next-generation technologies also require resist performance that is equal to or better than conventional performance in terms of sensitivity, critical dimension uniformity (CDU) performance, which is an index of uniformity of line width and hole diameter, and LWR (Line Width Roughness) performance, which indicates variation in line width and the line width of a resist pattern.

[0006] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method that can exhibit sufficient levels of sensitivity, CDU performance, and LWR performance when forming a resist pattern using next-generation technology.

[0007] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0008] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer including a structural unit having an acid-dissociable group; a radiation-sensitive acid generator including a first organic acid anion and a first onium cation; an acid diffusion controller including a second organic acid anion and a second onium cation, the acid diffusion controller generating an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation; and a solvent, wherein the first organic acid anion includes an acid anion moiety and an aromatic ring having at least both a first substituent and a second substituent, and the first substituent and the second substituent are each independently a hydroxy group, a sulfo group, or a sulfanyl group, and at least one selected from the group consisting of the polymer, the radiation-sensitive acid generator, and the acid diffusion controller includes an iodine group.

[0009] The radiation-sensitive composition exhibits excellent sensitivity, CDU performance, and LWR performance during resist pattern formation. While the reason for this is unclear, it is presumed as follows: At least one selected from the group consisting of a polymer, a radiation-sensitive acid generator, and an acid diffusion controller contains an iodine group. The iodine group (iodine atom) exhibits high absorption of radiation such as EUV with a wavelength of 13.5 nm, thereby increasing the photoelectron generation efficiency and enhancing the sensitivity of the resulting resist film. On the other hand, the use of an iodine group may increase the hydrophobicity of the radiation-sensitive composition, resulting in reduced solubility in a developer. In the radiation-sensitive composition, the first organic acid anion includes an acid anion moiety and an aromatic ring having at least both a first substituent and a second substituent, and the first substituent and the second substituent are each independently a hydroxy group, a sulfo group, or a sulfanyl group. By introducing highly polar first and second substituents into the aromatic ring contained in the first organic acid anion, the radiation-sensitive composition as a whole becomes hydrophilic, resulting in improved solubility in a developer and the ability to exhibit good CDU and LWR performance. Furthermore, the highly polar first and second substituents of the radiation-sensitive acid generator interact with the polar moiety of the polymer component (e.g., via hydrogen bonding), thereby increasing the glass transition temperature of the entire composition. This appropriately shortens the diffusion length of the acid generated from the radiation-sensitive acid generator, thereby improving CDU and LWR performance. It is believed that these combined effects enable the aforementioned resist performance to be exhibited.

[0010] In another embodiment, the present invention relates to a pattern forming method, comprising: a step of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; a step of exposing the resist film; and a step of developing the exposed resist film with a developer.

[0011] This pattern formation method uses the above-mentioned radiation-sensitive composition, which is capable of exhibiting excellent sensitivity, CDU performance, and LWR performance when forming a resist pattern, and therefore can efficiently form a high-quality resist pattern.

[0012] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0013] <Radiation-Sensitive Composition> The radiation-sensitive composition (hereinafter also referred to simply as "composition") according to this embodiment contains a polymer (hereinafter also referred to as "base polymer"), a radiation-sensitive acid generator, and an acid diffusion controller. The composition further contains a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0014] At least one selected from the group consisting of the polymer, the radiation-sensitive acid generator, and the acid diffusion controller contains an iodine group. This allows for increased sensitivity of the resulting resist film. The manner in which the iodine group is contained is not particularly limited, but it is preferably contained in the form of an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodine groups. In particular, it is preferred that at least one selected from the group consisting of the acid-dissociable group, the first organic acid anion, and the second organic acid anion contains an iodine group-containing aromatic ring structure.

[0015] By incorporating an iodine group into the base polymer, the radiation-sensitive acid generator, or the acid diffusion controller, the radiation absorption efficiency can be increased, and the secondary electron generation efficiency can be improved, thereby improving the sensitivity.

[0016] The aromatic ring in the iodo group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity.Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, heteroaromatic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, or combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0017] The number of iodo groups in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, and more preferably 1, 2 or 3.

[0018] <Polymer> The polymer (i.e., base polymer) is an aggregate of polymer chains containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)"). In addition to the structural unit (I), the base polymer may contain a structural unit (II) having a phenolic hydroxyl group or a structural unit (III) containing a lactone structure, etc. The composition may contain one or more types of base polymers. Each structural unit will be described below.

[0019] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. The structural unit (I) 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 a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. In the base polymer, it is preferable that the acid-dissociable group contains the above-mentioned iodine group-containing aromatic ring structure. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0020]

[0021] In the above formula (3), R １７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ L each independently represents a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO- or ＊ -L １１ａ represents COO-. １１ａis a substituted or unsubstituted arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.

[0022] The above R １７ From the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0023] L １１ａ Examples of the arenediyl group represented by the formula (I) include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl and naphthalenediyl groups. １１ａ As the alkyl group, a benzenediyl group is preferred.

[0024] L １１ａ Examples of the substituent that the arenediyl group represented by the formula (I) may have include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, and an alkoxy group.

[0025] L １１ａ Examples of the alkyl group as a substituent include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, and propyl. Examples of the fluorinated alkyl group include linear or branched fluorinated alkyl groups having 1 to 8 carbon atoms, such as trifluoromethyl and pentafluoroethyl. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as acetyloxy, propionyloxy, benzoyloxy, and acryloyloxy. Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, and a propoxy group.

[0026] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0027] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, isobutyl, and tert-butyl; alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

[0028] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; polycyclic alicyclic saturated hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group; monocyclic alicyclic unsaturated hydrocarbon groups such as a cyclopentenyl group and a cyclohexenyl group; and polycyclic alicyclic unsaturated hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group.

[0029] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0030] The above R １８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms is preferred.

[0031] R １９ and R ２０ The monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula １８ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms in the above formula, groups having 1 to 10 carbon atoms are exemplified.

[0032] R １９ and R ２０The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula １８ Examples of the monovalent alicyclic hydrocarbon group include those having 3 to 20 carbon atoms.

[0033] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded is not particularly limited as long as it is a group in which two hydrogen atoms have been removed from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above number of carbon atoms. It may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group.

[0034] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, and preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups are bridged alicyclic saturated hydrocarbon groups, such as bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1]heptane-2,2-diyl. ３，７ ] Decane-2,2-diyl group (adamantane-2,2-diyl group) and the like are preferred.

[0035] Among these, R １８ is an alkyl group, an alkenyl group, or a phenyl group having 1 to 4 carbon atoms, and R １９ and R ２０ are combined with each other, and the alicyclic structure formed together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0036] The above R １８ ~R ２０ Examples of the substituent that may be possessed by L include １１ａ Substituents that can be possessed by the arenediyl group represented by the following formula can be suitably employed.

[0037] Examples of the structural unit (I-1) include structural units represented by the following formulas (3-1) to (3-12) (hereinafter also referred to as "structural units (I-1-1) to (I-1-12)").

[0038]

[0039] In the above formulas (3-1) to (3-12), R １７ ~R ２０ has the same meaning as in formula (3). Ｌ１１ is a halogen atom, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. i and j are each independently an integer of 1 to 4. k and l are each 0 or 1. 3a are each independently an integer of 0 to 3. When 3a is 2 or more, multiple R Ｌ１１ are the same or different from each other.

[0040] i and j are preferably 1. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, an ethenyl group, a phenyl group, or an iodophenyl group. １９ and R ２０ R is preferably a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ is preferably an iodine atom or an alkoxy group. Ｌ１１ By employing an iodine atom as the aromatic ring structure, the above-mentioned iodo group-containing aromatic ring structure can be suitably introduced into the structural unit (I).

[0041] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (I).

[0042]

[0043] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer from 1 to 4.

[0044] The above R βｆ is preferably a hydrogen atom, a methyl group, or an ethyl group. １ As the number, 1 or 2 is preferred.

[0045] When the polymer contains the structural unit (I), the lower limit of the content of the structural unit (I) (total content when multiple types of structural unit (I) are present) relative to all structural units constituting the base polymer is preferably 20 mol%, more preferably 25 mol%, and even more preferably 30 mol%. The upper limit of this content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0046] (Structural Unit (II)) The structural unit (II) is a structural unit having a phenolic hydroxyl group. When the polymer contains the structural unit (II), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (II) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (II) is suitably applied to pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (II) is preferably represented by the following formula (2):

[0047] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. R １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４ is an integer from 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0048] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (II), the substituent is preferably a hydrogen atom or a methyl group.

[0049] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0050] R １０２ The halogen atom, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the above formula (3) is １１ａ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0051] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0052] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0053] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0054] The structural unit (II) is preferably a structural unit represented by the following formulas (2-1) to (2-20) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-20)").

[0055]

[0056]

[0057] In the above formulas (2-1) to (2-20), R β is the same as the above formula (2).

[0058] The lower limit of the content of the structural unit (II) (total content when multiple types of structural unit (II) are present) relative to all structural units constituting the base polymer is preferably 15 mol%, more preferably 25 mol%, and even more preferably 35 mol%. The upper limit of this content is preferably 85 mol%, more preferably 75 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (II) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity, CDU performance, and LWR performance.

[0059] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferable to polymerize the monomer in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then to obtain the structural unit (II) by deprotecting the phenolic hydroxyl group by hydrolysis. The hydroxystyrene may also be polymerized without protecting the phenolic hydroxyl group.

[0060] (Structural Unit (III)) The structural unit (III) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (III), the base polymer can adjust its solubility in a developer, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0061] Examples of the structural unit (III) include structural units represented by the following formulae (T-1) to (T-11).

[0062]

[0063] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. Ｌ４ and RＬ５ may be a divalent alicyclic group having 3 to 8 carbon atoms formed by combining together with the carbon atoms to which they are attached. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0064] The above R Ｌ４ and R Ｌ５ As a divalent alicyclic group having 3 to 8 carbon atoms formed by combining these together with the carbon atoms to which they are bonded, R １９ and R ２０ Among divalent alicyclic groups having 3 to 20 carbon atoms, which are formed by combining these together with the carbon atoms to which they are bonded, groups corresponding to structures having 3 to 8 carbon atoms can be suitably used. One or more hydrogen atoms on this alicyclic group may be substituted with a hydroxy group.

[0065] The above L ２ Examples of the divalent linking group represented by the formula (I) include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one group selected from the group consisting of -CO-, -O-, -NH-, and -S-.

[0066] Of these, the structural unit (III) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a norbornane lactone structure, and even more preferably a structural unit derived from norbornane lactone-yl (meth)acrylate.

[0067] The lower limit of the content of the structural unit (III) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on all structural units constituting the base polymer. The upper limit of the content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol% or less. By setting the content of the structural unit (III) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0068] (Structural Unit (IV)) The base polymer optionally has other structural units. Examples of the other structural units include structural unit (IV) containing a polar group (excluding those corresponding to structural unit (III)). By further including structural unit (IV), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0069] Examples of the structural unit (IV) include structural units represented by the following formula:

[0070]

[0071] In the above formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0072] When the base polymer has the structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of the structural unit (IV) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0073] (Structural Unit (VII)) The base polymer may contain a structural unit (VII) including a first acid-generating structure that has a third organic acid anion and a third onium cation and that generates an acid that dissociates the acid-dissociable group upon exposure. The onium salt structure formed by the third organic acid anion and the third onium cation (i.e., the first acid-generating structure) functions as a radiation-sensitive acid-generating structure.

[0074] When the base polymer contains the radiation-sensitive acid generating structure, the polarity of the base polymer in the exposed area increases, making it soluble in the developer when developed with an aqueous alkaline solution, but making it poorly soluble in the developer when developed with an organic solvent.

[0075] The form in which the third organic acid anion and the third onium cation are contained in the structural unit (VII) of the base polymer is not particularly limited. The base polymer may have the third organic acid anion as a side chain moiety, or the third onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding third organic acid anion or third onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the third organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the third onium cation is ionically bonded to the third organic acid anion as a counter ion of the third organic acid anion. On the other hand, when the third onium cation is bonded to the main chain of the base polymer as a side chain structure, the third organic acid anion is ionically bonded to the third onium cation as a counter ion of the third onium cation. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer have the third organic acid anion as a side chain moiety.

[0076] The third organic acid anion preferably has, as an acid anion moiety, at least one selected from the group consisting of a sulfonate anion and a sulfonimide anion. Examples of the acid generated by exposure include sulfonic acid and sulfonimide, corresponding to the acid anion moiety.

[0077] The third organic acid anion preferably includes, as a structure other than the acid anion moiety, —O—, —CO—, a cyclic structure, or a combination thereof. The combination also includes a structure (heterocyclic structure) in which —O— or —CO— is incorporated into the cyclic structure as a ring-forming moiety.

[0078] In the first acid generating structure, the third organic acid anion preferably has a sulfonate anion as the acid anion moiety, and an electron-withdrawing group is bonded to a carbon atom at the α- or β-position relative to the sulfur atom in the sulfonate anion. This allows the first acid generating structure to efficiently exhibit the above-mentioned function. Examples of the electron-withdrawing group include a fluorine atom, a fluorinated hydrocarbon group, a nitro group, and a cyano group. The fluorinated hydrocarbon group is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0079] The third organic acid anion preferably has an iodo group. The third organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0080] The third onium cation may be a radioactive onium cation. Examples of the radioactive onium cation include a sulfonium cation, a tetrahydrothiophenium cation, and an iodonium cation. Among these, a sulfonium cation or an iodonium cation is preferred, and a sulfonium cation is more preferred.

[0081] The third onium cation preferably has a fluoro group or an iodo group. The third onium cation preferably has a fluoro group-containing aromatic ring structure as a fluoro group-containing embodiment. The fluoro group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in an aromatic ring are substituted with fluoro groups. The aromatic ring in the fluoro group-containing aromatic ring structure can be suitably employed as the aromatic ring. Furthermore, the third onium cation preferably includes the iodo group-containing aromatic ring structure as a fluoro group-containing embodiment.

[0082] The structural unit (VII) having the above structures in combination can efficiently exhibit the above functions.

[0083] The structural unit (VII) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (VII-1)").

[0084]

[0085] In the formula, R Ｖ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ 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 some of the methylene groups constituting the alkylene group, cycloalkylene group, or arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ represents a single bond, an ether group, an ester group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and some 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 Rf may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. １ａ ~Rf ４ａ are each independently a hydrogen atom, a fluorine atom or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ ＋ is a sulfonium cation or an iodonium cation.

[0086] V ２ and V ３ The monovalent hydrocarbon group having 1 to 20 carbon atoms in the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group, or a sulfonium salt-containing group, an alkoxy group, or an alkoxycarbonyl group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group, or a sulfonate ester group.

[0087] The structural unit (IV-1) is preferably a structural unit represented by the following formula (a1-1):

[0088]

[0089] In the formula, R Ｖ , Rf １ａ ~Rf ４ａ , V １ and Z １ ＋ has the same meaning as in formula (a1) above. ４８ is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy 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 of 0 to 4. na is an integer of 0 to 3.

[0090] Examples of the third organic acid anion of the monomer that gives the structural unit (VII) (including the structural unit (IV-1)) include, but are not limited to, those shown below. In the following, the iodo group of the iodo group-containing aromatic ring structure may be a hydrogen atom or an iodo group of L in the above formula (3). １１ In the following formula, R Ｖ is synonymous with the above.

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] Z in the above formula (a1) １ａ ＋ As the onium cation, the first onium cation in the radiation-sensitive acid generator described below can be suitably used.

[0098] It is also possible to adopt an embodiment in which a third onium cation is bonded to the main chain as a side chain structure of the base polymer, and a third organic acid anion is bonded to the third onium cation by ionic bonding as a counter ion of the third onium cation. In this case, the third onium cation is bonded to the main chain via a divalent linking group or a single bond, and V in the above formula (a1) ２ From SO ３ － The divalent linking group is preferably L in the formula (3). １１ A group represented by the following formula can be preferably used.

[0099] When the base polymer has the structural unit (VII), the lower limit of the content of the structural unit (VII) (when multiple types are contained, the total content) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol% or less, and even more preferably 25 mol% or less. By setting the content of the structural unit (VII) within the above range, the function as an acid generating structure can be fully exhibited, and the above resist properties can be exhibited.

[0100] The monomer that provides the structural unit (VII-1) can be synthesized, for example, by a method similar to that for the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0101] (Structural Unit (VIII)) The base polymer may contain a structural unit (VIII) including a second acid generating structure having a fourth organic acid anion and a fourth onium cation, which generates an acid that does not dissociate the acid-dissociable group upon exposure. The onium salt structure formed by the fourth organic acid anion and the fourth 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 does not substantially dissociate the acid-dissociable group of the structural unit (I), and has the function of suppressing the diffusion of the acid generated from the first acid generating structure or the radiation-sensitive acid generator in unexposed areas through salt exchange. The acid generated from the second acid generating structure can be said to be a relatively weaker acid (an acid with a higher pKa) than the acid generated from the first acid generating structure. Whether the onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable group of the base polymer and the acidity of the onium salt structure or the acid generated.

[0102] The form in which the fourth organic acid anion and the fourth onium cation are contained in the structural unit (VIII) of the base polymer is not particularly limited. The base polymer may have the fourth organic acid anion as a side chain moiety or the fourth onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding fourth organic acid anion or the fourth onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the fourth organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the fourth onium cation is ionically bonded to the fourth organic acid anion as a counter ion of the fourth organic acid anion. On the other hand, when the fourth onium cation is bonded to the main chain of the base polymer as a side chain structure, the fourth organic acid anion is ionically bonded to the fourth onium cation as a counter ion of the fourth onium cation. From the viewpoint of development contrast, it is preferable that the base polymer have the fourth organic acid anion as a side chain moiety.

[0103] The fourth organic acid anion preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety, and more preferably has a carboxylate anion. However, when the fourth organic acid anion has the sulfonate anion, no electron-withdrawing group is bonded to the carbon atom at the α- or β-position relative to the sulfur atom in the sulfonate anion. Examples of the electron-withdrawing group include the electron-withdrawing group that the third organic acid anion may have in the first acid-generating structure. The acid generated by exposure is a carboxylic acid or sulfonic acid corresponding to the acid anion moiety.

[0104] The fourth organic acid anion preferably contains, as a structure other than the acid anion moiety, —O—, —CO—, a cyclic structure, or a combination thereof. As such a structure, the structures shown for the third organic acid anion can be suitably adopted.

[0105] The fourth organic acid anion preferably has an iodo group or a hydroxy group. The fourth organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0106] Examples of the quaternary onium cation include radiolytic and non-radiolytic onium cations. Examples of the radiolytic and non-radiolytic onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, and ammonium cation. Among these, sulfonium cation and iodonium cation are preferred, and sulfonium cation is more preferred.

[0107] The quaternary onium cation preferably has a fluoro group or an iodo group. The quaternary onium cation preferably contains the fluoro group-containing aromatic ring structure or the iodo group-containing aromatic ring structure as a mode of containing the fluoro group or the iodo group.

[0108] The structural unit (VIII) having the above structures in combination can efficiently exhibit the above functions.

[0109] The structural unit (VIII) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (VIII-1)").

[0110]

[0111] In formula (p1), R Ｐ is a hydrogen atom or a methyl group.

[0112] In formula (p1), X 1 is a single bond, an ester bond, an ether bond, a phenylene group, or a naphthylene group.

[0113] In formula (p1), X ２ represents a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may contain an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２ The hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a butane-2,2-diyl group, a butane-2,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-2 ... alkanediyl groups having 1 to 12 carbon atoms, such as diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group; cyclic saturated hydrocarbylene groups having 3 to 12 carbon atoms, such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group; and groups obtained by combining these.

[0114] In formula (p1), X 3 is a single bond, an ester bond or an ether bond.

[0115] In formula (p1), R Ｘis a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy 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.

[0116] In formula (p1), Z ２ ＋ is Z in the above formula (a1). １ａ ＋ is synonymous with.

[0117] In formula (p1), y1 is an integer of 0 to 3. When x1 is 2 or more, a plurality of R Ｘ are the same or different.

[0118] In formula (p1), y2 is 0 or 1.

[0119] Examples of the fourth organic acid anion of the monomer that gives the structural unit (VIII) include, but are not limited to, those shown below. １１ In the following formula, R Ｐ is the same as above. The fourth organic acid anion preferably has a carboxylate anion and a hydroxy group. In this case, it is preferable that the carboxylate anion and the hydroxy group are bonded to the same aromatic ring in the fourth organic acid anion, and it is more preferable that the carbon atom to which the carboxylate anion is bonded and the carbon atom to which the hydroxy group is bonded are directly bonded to each other in the same aromatic ring.

[0120]

[0121]

[0122]

[0123]

[0124] It is also possible to adopt an embodiment in which a quaternary onium cation is bonded to the main chain as a side chain structure of the base polymer, and a quaternary organic acid anion is bonded to the quaternary onium cation by ionic bonding as a counter ion of the quaternary onium cation. In this case, the quaternary onium cation is bonded to the main chain via a divalent linking group or a single bond, and X in the above formula (p1) １ From COO － The structure up to is preferably ionically bonded to the quaternary onium cation as a counter ion. １１ A group represented by the following formula can be preferably used.

[0125] When the base polymer contains the structural unit (VIII), the lower limit of the content of the structural unit (VIII) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol% or less, and even more preferably 25 mol% or less. When an optional acid diffusion controller is included, the total amount of the monomer that provides the structural unit (VIII) and the acid diffusion controller may be within the above range. By setting the content of the structural unit (VIII) within the above range, the function of the acid diffusion control structure can be fully exhibited.

[0126] When the base polymer contains the structural unit (VII) and the structural unit (VIII), one polymer chain may contain the structural unit (VII) and the structural unit (VIII), or one polymer chain may contain the structural unit (VII) and another polymer chain may contain the structural unit (VIII). It is sufficient that the polymer chain aggregate contains the structural unit (VII) and the structural unit (VIII).

[0127] (Method of Synthesizing Base Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0128] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0129] Examples of the solvent used in the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, and 2-heptanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; and alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-methoxy-2-propanol, and 4-methyl-2-pentanol. The solvents used in the polymerization may be used alone or in combination of two or more.

[0130] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0131] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 2,000, more preferably 3,000, even more preferably 4,000, and particularly preferably 4,500. The upper limit of Mw is preferably 20,000, more preferably 10,000, even more preferably 8,000, and particularly preferably 7,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0132] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0133] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0134] The lower limit of the content of the base polymer is preferably 40% by mass, more preferably 50% by mass, and even more preferably 55% by mass, relative to the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 80% by mass, more preferably 75% by mass, and even more preferably 70% by mass.

[0135] (Other Polymers) The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having 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, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer, and as a result, it is possible to modify the surface of the resist film during EUV exposure and control the distribution of the composition within the film.

[0136] The high-fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)"), and may also have the structural unit (I) or the structural unit (IV) of the base polymer, as necessary.

[0137]

[0138] In the above formula (5), R １３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, —COO—, or —SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. １４ 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.

[0139] The above R １３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0140] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a single bond and —COO— are preferred, and —COO— is more preferred.

[0141] The above R １４ Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0142] The above R １４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0143] The above R １４ As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropan-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group are even more preferable.

[0144] When the high-fluorine content polymer has the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of the structural unit (V) within the above range, the mass content of fluorine atoms in the high-fluorine content polymer can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film. As a result, the surface modification properties, component distribution controllability, and water repellency of the resist film can be further improved.

[0145] The high-fluorine content polymer may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VI)) in addition to or instead of the structural unit (V). By having the structural unit (f-2), the high-fluorine content polymer has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0146]

[0147] The structural unit (VI) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R Ｅ At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ｄｄ R has a structure in which -, a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0148] When the structural unit (VI) has an alkali-soluble group (x), RＦ is a hydrogen atom, and A １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ The binding site of W is shown. １ represents a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ is an oxygen atom, W １ is A １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R 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 may be the same or different. When the structural unit (VI) has an alkali-soluble group (x), it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VI) having an alkali-soluble group (x), A １ is an oxygen atom and W １ It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0149] When the structural unit (VI) has an alkali-dissociable group (y), R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-* or -SO ２ O-*. ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R Ｆ The binding site of W is shown. １ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ is -COO-*, -OCO-* or -SO ２ If O-*, then W １ or R Ｆ is A １ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom.１ is an oxygen atom, W １ , R Ｅ is a single bond, and R Ｄ is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ A carbonyl group is bonded to the end of the R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VI) has an alkali-dissociable group (y), the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. Examples of the structural unit (VI) having an alkali-dissociable group (y) include A １ is -COO-*, and R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0150] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0151] R Ｅ When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and even more preferably a group having a norbornane lactone structure.

[0152] When the high-fluorine-content polymer has the structural unit (VI), the lower limit of the content of the structural unit (VI) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of the structural unit (VI) within the above range, the solubility in an alkaline developer can be improved, thereby suppressing the occurrence of development defects.

[0153] (Other structural units) The high fluorine content polymer may contain the structural unit (I) or the structural unit (IV) of the base polymer as a structural unit other than the structural units listed above. When the high fluorine content polymer contains the structural unit (IV), the structural unit (IV) is preferably a structure containing a fluorine atom.

[0154] When the high fluorine content polymer contains the structural unit (I), the content ratio of the structural unit (I) in the high fluorine content polymer can suitably be the same as that described for the base polymer.

[0155] When the high-fluorine content polymer contains the structural unit (IV), the lower limit of the content of the structural unit (IV) in all structural units constituting the high-fluorine content polymer is preferably 50 mol%, more preferably 60 mol%, and even more preferably 65 mol%, and the upper limit of the content is preferably 99 mol%, more preferably 98 mol%, and even more preferably 95 mol%.

[0156] The lower limit of Mw of the high fluorine content polymer is preferably 2,000, more preferably 3,000, and even more preferably 4,000. The upper limit of Mw is preferably 20,000, more preferably 10,000, and even more preferably 7,000.

[0157] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0158] When the radiation-sensitive composition contains a high-fluorine-containing polymer, the content of the high-fluorine-containing polymer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the base polymer, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less.

[0159] By setting the content of the high fluorine-containing polymer within the above range, the high fluorine-containing polymer can be more effectively localized in the surface layer of the resist film, which in turn makes it possible to modify the surface of the resist film during EUV exposure and control the distribution of the composition within the film. The radiation-sensitive composition may contain one or more high fluorine-containing polymers.

[0160] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0161] <Radiation-Sensitive Acid Generator> The radiation-sensitive acid generator contains a first organic acid anion and a first onium cation, forming an onium salt structure. The radiation-sensitive acid generator is a component that generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer and generating a carboxyl group or the like. The radiation-sensitive acid generator may be contained in the radiation-sensitive composition in a form in which the onium salt structure exists alone as a compound (isolated from the polymer), in which the onium salt structure is incorporated as part of the polymer, or in both of these forms. The radiation-sensitive acid generator is preferably contained in the radiation-sensitive composition in a form in which the onium salt structure exists alone as a (low-molecular-weight) compound.

[0162] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0163] When the radiation-sensitive composition contains a radiation-sensitive acid generator, the polarity of the polymer in the exposed area increases, and the polymer becomes soluble in the developer in the case of aqueous alkaline development, while becoming poorly soluble in the developer in the case of organic solvent development.

[0164] The first organic acid anion includes an acid anion moiety and an aromatic ring having at least both a first substituent and a second substituent (hereinafter, the aromatic ring serving as the parent skeleton is also referred to as a "specific aromatic ring"). The first substituent and the second substituent are each independently a hydroxy group, a sulfo group, or a sulfanyl group.

[0165] The acid anion moiety is preferably a sulfonate anion or a sulfonimide anion, more preferably a sulfonate anion.

[0166] The specific aromatic ring may be the aromatic ring in the iodo group-containing aromatic ring structure. The specific aromatic ring may be either polycyclic or monocyclic, but is preferably a monocyclic ring, and more preferably a benzene ring. The number of specific aromatic rings in the radiation-sensitive acid generator is not particularly limited, but is preferably one, two, or three, and more preferably one or two, from the viewpoint of solubility.

[0167] At least one of the first substituent and the second substituent is preferably a hydroxy group, and more preferably both the first substituent and the second substituent are hydroxy groups in terms of solubility in a developer, CDU performance, and LWR performance.

[0168] Although the positions of the first and second substituents on the specific aromatic ring are not specified, it is preferable that the first and second substituents are present at the ortho-position (i.e., the carbon atom to which the first substituent is bonded is adjacent to the carbon atom to which the second substituent is bonded), which forms an intramolecular hydrogen bond, relatively increasing the acidity and enhancing the solubility of the radiation-sensitive acid generator, and also inducing an increase in the glass transition temperature due to interaction with the polymer, thereby improving the CDU performance and LWR performance due to the shortened diffusion.

[0169] The specific aromatic ring may have one or more substituents other than the first and second substituents. Examples of the other substituents include a halogen atom, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, and an alkoxy group. Examples of the other substituents include L in the above formula (3). １１ａ Substituents that can be possessed by the arenediyl group represented by the following formula can be suitably employed.

[0170] In terms of improving sensitivity, the first organic acid anion preferably contains the iodo group-containing aromatic ring structure. The specific aromatic ring may have an iodine atom as a substituent other than the first substituent and the second substituent, thereby forming the iodo group-containing aromatic ring structure. The first organic acid anion may contain the iodo group-containing aromatic ring structure in addition to the specific aromatic ring.

[0171] The first organic acid anion preferably contains —O—, —CO—, a cyclic structure, or a combination thereof. The combination also includes a structure (heterocyclic structure) in which —O— or —CO— is incorporated into the cyclic structure as a ring-forming moiety.

[0172] The cyclic structure may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to form a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the skeleton of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0173] The alicyclic structure may be R １８ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably employed.

[0174] As the aromatic ring structure, the aromatic rings (including aromatic hydrocarbon rings and heteroaromatic rings) shown in the iodo group-containing aromatic ring structure can be suitably used.

[0175] Examples of the heterocyclic structure 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 thietane, thiolane, and thiane; 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.

[0176] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof. Examples of such structures include structures represented by the following formulas (H-1) to (H-11).

[0177]

[0178] In the above formula, γ is an integer of 1 to 3.

[0179] Examples of the divalent heteroatom-containing group include —CO—, —CS—, —NR′—, —O—, —S—, and —SO ２ - or a divalent group formed by combining these groups, etc. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0180] In the radiation-sensitive acid generator, the acid anion moiety is preferably a sulfonate anion, and a fluorine atom or a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfur atom of the sulfonate anion, thereby allowing the radiation-sensitive acid generator to efficiently exhibit the above-mentioned functions.

[0181] The radiation-sensitive acid generator is preferably represented by the following formula (G-1).

[0182]

[0183] In formula (G-1), L１ is a single bond, an ether bond, or an ester bond, or an alkylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The alkylene group may be linear, branched, or cyclic.

[0184] R １ and R ２ are each independently a hydroxy group, a sulfo group, or a sulfanyl group.

[0185] R ３ and R ４ are each independently a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, or an alkylsulfonyloxy group having 1 to 20 carbon atoms, which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group, or an alkoxy group having 1 to 10 carbon atoms, or -NR ８ -C(=O)-R ９ Or -NR ８ -C(=O)-OR ９ and R ８ represents a hydrogen atom, or an alkyl group having 1 to 6 carbon atoms which may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms; R ９ is an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and may contain a halogen atom, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms. The alkyl group, alkoxy group, alkoxycarbonyl group, acyloxy group, acyl group, and alkenyl group may be linear, branched, or cyclic.

[0186] Of these, R ３ Examples of the hydroxyl group include -NR ８ -C(=O)-R ９ fluorine atom, chlorine atom, bromine atom, methyl group, methoxy group, etc. are preferred.

[0187] R ５ is g ４ When g is 1, it is a single bond or a divalent linking group having 1 to 20 carbon atoms; ４ When is 0, the carbon number is 1 to 20 (g １ The linking group is a linking group having a valence of +1. １８ Examples of the heteroatom-containing group include a monovalent hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (I), a group having the above-mentioned divalent heteroatom-containing group between carbon atoms of the hydrocarbon group (between two adjacent or non-adjacent carbon atoms), a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a group combining these. Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom. The linking group is -O-, -S-, -NR ＬＬ It is preferable that R contains -, -CO-, the above cyclic structure, or a combination thereof. ＬＬ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0188] Rf １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one of them is a fluorine atom or a trifluoromethyl group. １ and Rf ２ may combine to form a carbonyl group. ３ and Rf ４ are preferably both fluorine atoms.

[0189] g １ is an integer from 1 to 3. ２ and g ３ are each independently an integer of 0 to 2. ４ is 0 or 1. g ５ is an integer from 0 to 3. ６ is an integer from 0 to 2. ７ is 0 or 1. g ２ +g ５ is preferably an integer of 1 to 5, and more preferably an integer of 1 to 3. ４ If is 0, g２ is preferably 1 or 2. ４ If is 1, g ２ is 0, and g ５ is preferably an integer of 1 to 3.

[0190] Examples of the first organic acid anion of the radiation-sensitive acid generator represented by formula (G-1) above include, but are not limited to, those shown below. Note that, instead of the first organic acid anion having an iodo group-containing aromatic ring structure, a first organic acid anion not having an iodo group-containing aromatic ring structure can suitably be a structure in which the iodo group in the following formula is substituted with an atom or group other than an iodo group, such as a hydrogen atom or another substituent.

[0191]

[0192]

[0193]

[0194] Z １ ＋ is the first onium cation. The first onium cation preferably contains at least one of a fluoro group and an iodo group. The first onium cation preferably contains an aromatic ring having a fluoro group (hereinafter also referred to as a "fluoro group-containing aromatic ring structure"). The fluoro group-containing aromatic ring structure includes not only a structure in which a fluoro group is directly bonded to an aromatic ring, but also a structure in which a fluoro group is bonded to an aromatic ring via another structure. The aromatic ring in the fluoro group-containing aromatic ring structure can be suitably the same as the aromatic ring in the iodo group-containing aromatic ring structure.

[0195] The number of fluoro groups in the fluoro group-containing aromatic ring structure is not particularly limited, but is preferably 1, 2, 3, 4 or 5, and more preferably 1, 2, 3 or 4.

[0196] The first onium cation more preferably contains the iodo group-containing aromatic ring structure as an embodiment containing an iodo group.

[0197] The first onium cation is preferably a sulfonium cation or an iodonium cation, and more preferably a sulfonium cation.

[0198] The first onium cation is preferably represented by the following formula (Q-1):

[0199]

[0200] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or greater, multiple Ra2s may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or greater, multiple Ra3s may be the same or different. Ra3 represents a substituent. Ra1 and Ra2 may be bonded to each other to form a ring. When n1 is 2 or greater, multiple Ra1s may be bonded to each other to form a ring. When n2 is 2 or greater, multiple Ra2s may be bonded to each other to form a ring.

[0201] The substituents represented by Ra1, Ra2 and Ra3 are preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom or a halogenated hydrocarbon group.

[0202] The alkyl groups of Ra1 and Ra2 may be linear or branched. The alkyl groups preferably have 1 to 10 carbon atoms, and examples thereof 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. Of these, methyl, ethyl, n-butyl, and t-butyl are particularly preferred.

[0203] The cycloalkyl group of Ra1 and Ra2 includes a monocyclic or polycyclic cycloalkyl group (preferably a cycloalkyl group 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.

[0204] Examples of the alkyl group moiety of the alkoxy group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferred.

[0205] Examples of the cycloalkyl group moiety of the cycloalkyloxy group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0206] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1 and Ra2 include those previously listed as the alkoxy group of Ra1 and Ra2. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0207] Examples of the alkyl group moiety of the alkylsulfonyl group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. Furthermore, examples of the cycloalkyl group moiety of the cycloalkylsulfonyl group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. Particularly preferred of these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl groups.

[0208] Each of the groups Ra1 and Ra2 may further have a substituent, such as a halogeno group such as a fluoro group (preferably a fluoro group), a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, a cycloalkyloxyalkyl group, an alkoxycarbonyl group, a cycloalkyloxycarbonyl group, an alkoxycarbonyloxy group, and a cycloalkyloxycarbonyloxy group.

[0209] Examples of the halogen atom (halogeno group) of Ra1 and Ra2 include a fluorine atom (fluoro group), a chlorine atom (chloro group), a bromine atom (bromo group), and an iodine atom (iodine group), with a fluoro group and an iodo group being preferred.

[0210] The halogenated hydrocarbon group of Ra1 and Ra2 is preferably a halogenated alkyl group. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF ３ is more preferred.

[0211] As described above, Ra1 and Ra2 may be bonded 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 bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２ -, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more of these, and those having a total carbon number of 20 or less are preferred. When Ra1 and Ra2 are bonded to each other to form a ring, Ra1 and Ra2 are bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２It is preferable that they form - or a single bond. Among these, it is more preferable that they form -O-, -S- or a single bond, and it is particularly preferable that they form a single bond. Furthermore, when n1 is 2 or more, multiple Ra1's may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2's may be linked to each other to form a ring. Such an example includes an embodiment in which two Ra1's are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0212] Ra3 is preferably a fluoro group or a group having one or more fluoro groups. Examples of the group having a fluoro group include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluoro group. Among these, fluorinated alkyl groups are 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 , C.H. ２ CF ３ , C.H. ２ CH ２ CF ３ , C.H. ２ C ２ F ５ , C.H. ２ CH ２ C ２ F ５ , C.H. ２ C ３ F ７ , C.H. ２ CH ２ C ３ F ７ , C.H. ２ C ４ F ９ and CH ２ CH ２ C ４ F９ More preferred examples include CF ３ can be particularly preferably mentioned.

[0213] Ra3 is a fluoro group or CF ３ is preferably a fluoro group, and a fluoro group is more preferably a fluoro group.

[0214] n1 and n2 each independently represent preferably an integer of 0 to 3, more preferably an integer of 0 to 2.

[0215] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0216] (n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, n3=1 and Ra3 is a fluoro group or CF ３ When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently a fluoro group or CF ３ and n3=2 and Ra3 is a fluoro group or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluoro group or CF ３ When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluoro group or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluoro group or CF ３ a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluoro group or CF ３ and n3=5 and each Ra3 is independently a fluoro group or CF ３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently a fluoro group or CF ３ A combination in which:

[0217] Specific examples of such onium cations represented by the above formula (Q-1) include the following: The iodo group or fluoro group in the onium cations below may be substituted with a hydrogen atom or other substituent.

[0218]

[0219]

[0220]

[0221]

[0222] When the first onium cation is an iodonium cation, it is preferably a diaryliodonium cation, and more preferably the diaryliodonium cation has one or more fluoro or iodo groups.

[0223] The radiation-sensitive acid generator represented by formula (G-1) can be synthesized by a known method, particularly a salt exchange reaction. Known radiation-sensitive acid generators can also be used as long as they do not impair the effects of the present invention.

[0224] These radiation-sensitive acid generators may be used alone or in combination of two or more. The lower limit of the content of the radiation-sensitive acid generators (total content when multiple types are used) is preferably 10 parts by mass, more preferably 20 parts by mass, and even more preferably 25 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 100 parts by mass, more preferably 90 parts by mass, and even more preferably 80 parts by mass. When the base polymer contains structural unit (VII), the lower limit of the content of the radiation-sensitive acid generators (total content when multiple types are used) is preferably 2 parts by mass, more preferably 5 parts by mass, and even more preferably 8 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 30 parts by mass, more preferably 20 parts by mass, and even more preferably 15 parts by mass. This allows the resist pattern to exhibit excellent sensitivity, CDU performance, and LWR performance during formation.

[0225] <Acid Diffusion Controller> The acid diffusion controller contains a second organic acid anion and a second onium cation, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The acid diffusion controller does not substantially dissociate the acid-dissociable group of the base polymer under pattern formation conditions using the radiation-sensitive composition, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas through salt exchange.

[0226] By including the acid diffusion controller in the radiation-sensitive composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern that is superior in CDU performance and LWR performance.

[0227] The structure of the second organic acid anion is not particularly limited, but preferably contains —O—, —CO—, a cyclic structure, or a combination thereof. As the cyclic structure, a cyclic structure in a radiation-sensitive acid generator can be suitably used.

[0228] The second organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0229] In the acid diffusion controller, the second organic acid anion preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety (provided that, when the second organic acid anion has the sulfonate anion, neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfur atom of the sulfonate anion), which allows the acid diffusion controller to efficiently exhibit the second function.

[0230] Examples of the acid diffusion controller include a sulfonium salt compound represented by the following formula (8-1), an iodonium salt compound represented by the following formula (8-2), etc. Further examples include a compound containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and a compound containing an iodonium cation and an anion in the same molecule represented by the following formula (8-4).

[0231]

[0232] In the above formulas (8-1) to (8-4), J＋ is a sulfonium cation, and U ＋ is an iodonium cation. － and Q － are each independently OH － , R α -COO － , R α -SO ３ － In the above formulas (8-1) and (8-2), R α is a monovalent organic group having 1 to 30 carbon atoms. α is a single bond or a divalent organic group having 1 to 30 carbon atoms. Examples of this organic group include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of this hydrocarbon group or at the carbon chain terminal, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a combination thereof.

[0233] The monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group is R １８ Preferably, a monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by the following formula: As the divalent heteroatom-containing group and the monovalent heteroatom-containing group, preferably, the divalent heteroatom-containing group and the monovalent heteroatom-containing group in the radiation-sensitive acid generator described above can be used.

[0234] Examples of the second organic acid anion of the acid diffusion controller include, but are not limited to, those shown below. Examples also include compounds containing an iodonium cation and anion in the same molecule and compounds containing a sulfonium cation and anion in the same molecule. As the organic acid anion without an iodo group-containing aromatic ring structure, a structure in which the iodo group in the following formula is substituted with an atom or group other than the iodo group, such as a hydrogen atom or another substituent, can be suitably used.

[0235]

[0236]

[0237] The second onium cation is preferably a sulfonium cation or an iodonium cation, and more preferably a sulfonium cation.

[0238] The second onium cations preferably each independently contain at least one of a fluoro group and an iodo group. The second onium cation more preferably contains the fluoro group-containing aromatic ring structure. The second onium cation more preferably contains the iodo group-containing aromatic ring structure.

[0239] As the second onium cation in the acid diffusion controller, the first onium cation in the radiation-sensitive acid generator can be suitably used.

[0240] When the second onium cation is an iodonium cation, it is preferably a diaryliodonium cation, and more preferably the diaryliodonium cation has one or more fluoro groups.

[0241] The acid diffusion controller can be synthesized by a known method, particularly a salt exchange reaction. Known acid diffusion controllers can also be used as long as they do not impair the effects of the present invention.

[0242] These acid diffusion controllers may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (total content when multiple types are used) is preferably 2 parts by mass, more preferably 5 parts by mass, and even more preferably 8 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 40 parts by mass, more preferably 30 parts by mass, and even more preferably 25 parts by mass. When the base polymer contains the structural unit (VIII), the composition does not need to contain an acid diffusion controller. This allows the composition to exhibit excellent sensitivity, CDU performance, and LWR performance during resist pattern formation.

[0243] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the base polymer, the radiation-sensitive acid generator, the acid diffusion controller, and optional additives.

[0244] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0245] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based 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-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified. In the present embodiment, alcoholic 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 alcoholic solvents.

[0246] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0247] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0248] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0249] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0250] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0251] Among these, ester-based solvents and ether-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents and polyhydric alcohol partial ether-based solvents are more preferred, and propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0252] <Other Optional Components> The radiation-sensitive composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0253] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer, a radiation-sensitive acid generator, an acid diffusion controller, and a solvent, and, if necessary, other optional components, in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of approximately 0.05 μm to 0.4 μm. The solids concentration of the 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.

[0254] <Pattern Forming Method> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0255] According to the pattern formation method, a high-quality resist pattern can be formed because the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity, CDU performance, and LWR performance during pattern formation.

[0256] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed, if necessary, to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 160°C, preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0257] Furthermore, when the subsequent exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having at least one of the structural units (I) and (II) as the base polymer in the composition.

[0258] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is irradiated with radiation through a photomask to expose it. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. 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.

[0259] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0260] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0261] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, 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.

[0262] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent 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 the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, chain ketones are preferred, with 2-heptanone being more preferred. The content of the 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 the organic solvent in the developer include water and silicone oil.

[0263] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0264] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0265] [Measurement of Weight Average Molecular Weight (Mw), Number Average Molecular Weight (Mn), and Dispersity (Mw / Mn)] Measurements were performed by gel permeation chromatography (GPC) using Tosoh GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL") under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, and column temperature: 40°C, with monodisperse polystyrene as the standard.

[0266] [ １ H-NMR analysis and １３C-NMR Analysis] Measurement was carried out using a JEOL "JNM-Delta400".

[0267] <Synthesis of Polymer> 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 refer to a value when the total mass of the monomers used is 100 parts by mass, and mol % refers to a 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.

[0268]

[0269]

[0270] [Method of Polymer Synthesis] [Synthesis Example 1] (Synthesis of Polymer (P-1)) Compound (M-1) and compound (M-16) as monomers were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 45 / 55. Next, azobisisobutyronitrile (4 mol%) was added as an initiator to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass 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 an additional 3 hours, allowing the polymerization reaction to proceed for a total of 6 hours. After completion of the polymerization reaction, 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 relative to the polymerization solution, then filtered and dissolved in 1-methoxy-2-propanol (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After completion of the reaction, the residual solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass). The polymer was coagulated by dropping the solution into 500 parts by mass of water, and the resulting solid was filtered. The solution was dried at 50°C for 12 hours to synthesize a white powdery polymer (P-1). The Mw of the resulting polymer (P-1) was 5102, and the Mw / Mn was 1.57. １３As a result of C-NMR analysis, the content ratio of the structural unit derived from compound (M-1):the structural unit derived from compound (M-16) was 43:57 (mol %).

[0271] [Synthesis Examples 2 to 17] (Synthesis of Polymers (P-2) to (P-17)) Polymers (P-2) to (P-17) containing predetermined amounts of the types of monomers listed in Table 1 were obtained in the same manner as in Synthesis Example 1. Table 1 also shows the Mw, Mw / Mn, yield (%) of each obtained polymer, and the content of structural units derived from each monomer in each polymer.

[0272] Synthesis Example 18 Synthesis of Polymer (P-18) Compound (M-1), compound (M-26), and compound (M-27) as monomers were dissolved in 2-butanone (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 50 / 30 / 20. Azobisisobutyronitrile (AIBN) was added as an initiator in an amount of 6 mol % relative to the total amount of monomers to prepare a monomer solution. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel and heated to 80°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours. Thereafter, the mixture was further heated at 80°C for 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. Acetonitrile (100 parts by mass) and hexane (600 parts by mass) were added to the obtained polymerization solution and stirred. The lower layer was recovered and the solvent was removed to obtain polymer (P-18). The Mw of the obtained polymer (P-18) was 6,201, and the Mw / Mn was 1.46. １３ As a result of C-NMR analysis, the content ratio of the structural unit derived from compound (M-1): the structural unit derived from compound (M-26): the structural unit derived from compound (M-27) was 48:32:20 (mol %).

[0273] [Synthesis Examples 19 to 21] (Synthesis of Polymers (P-19) to (P-21)) Polymers (P-19) to (P-21) were obtained by compounding predetermined amounts of the types of monomers shown in Table 1 in the same manner as in Synthesis Example 18. Table 1 also shows the Mw, Mw / Mn, yield (%) of each obtained polymer, and the content of structural units derived from each monomer in each polymer.

[0274]

[0275] [Synthesis of Highly Fluorine-Containing Polymers] [Synthesis Example 22] (Synthesis of Polymer (E-1)) Compounds (M-24) and (M-25) as monomers were dissolved in 2-butanone (200 parts by mass) so that the molar ratio was 10 / 90. AIBN (5 mol % based on the total monomers) was added thereto as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and the mixture was purged with nitrogen for 30 minutes. The temperature inside the reaction vessel was brought to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition was designated as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The solvent was replaced with acetonitrile (400 parts by mass), and then hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was collected. This procedure was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of polymer (E-1) was obtained in good yield. １３ As a result of C-NMR analysis, the content ratio of the structural unit derived from compound (M-24):the structural unit derived from compound (M-25) was 9:91 (mol %).

[0276] Synthesis Example 23 (Synthesis of Polymer (E-2)) Polymer (E-2) was obtained by blending a predetermined amount of the type of monomer shown in Table 2 in the same manner as in Synthesis Example 22. Table 2 also shows the Mw, Mw / Mn, yield (%) of each obtained polymer, and the content of the structural unit derived from each monomer in each polymer.

[0277] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator, acid diffusion controller, and solvent that constitute the radiation-sensitive composition are described below.

[0278] [Radiation-sensitive acid generators] A-1 to A-17: Compounds represented by the following formulas (A-1) to (A-17)

[0279]

[0280]

[0281] Among the radiation-sensitive acid generators represented by the above formula, synthesis examples of the radiation-sensitive acid generators used in the examples are shown below.

[0282] <Synthesis of Radiation-Sensitive Acid Generator (1)> [Synthesis Example 24] (Synthesis of Radiation-Sensitive Acid Generator (A-1))

[0283]

[0284] Compound 1 (5.00 g, 1.0 eq.) was dissolved in 15 mL of pyridine, and the solution was cooled to 5°C. Acetic anhydride (7.10 g, 2.145 eq.) was then added dropwise, and the mixture was stirred at 5°C for 2 hours. After the reaction was completed, 200 mL of water was added to quench the reaction. After extraction with 50 mL of dichloromethane five times, the organic layer was washed with 100 mL of 2N aqueous HCl solution. The organic layer was dried over anhydrous sodium sulfate, filtered, concentrated, and dried to obtain compound 2 in an 84% yield.

[0285]

[0286] Compound 2 (3.50 g, 1.1 eq) was dissolved in dichloromethane (DCM) (30 mL) in a reaction vessel, and the solution was then cooled to 5°C. While still cooled at 5°C, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC.HCl) (2.82 g, 1.1 eq), pyridine (2.12 g, 2.0 eq), and compound 3 (5.00 g, 1.0 eq.) were added, and the solution was stirred at room temperature (RT) for 1 hour. After completion of the reaction, methanol (30 mL) was added to the solution to precipitate a powder, which was then stirred at room temperature for 30 minutes. The mixture was filtered and dried under vacuum to obtain compound 4 in a 79% yield. The resulting compound was used in the subsequent reaction.

[0287]

[0288] Compound 4 (5.80 g, 1.0 eq.) was added to a reaction vessel and dissolved in methanol (MeOH) (30 mL), followed by cooling to 5°C. After cooling, potassium carbonate (2.97 g, 2.2 eq.) was added portionwise over 0.5 hours, followed by stirring at 5°C for 1 hour. After completion of the reaction, the mixture was quenched with 100 mL of saturated aqueous ammonium chloride solution, and then extracted with ethyl acetate to separate the organic layer. The organic layer was dried over sodium sulfate, the solvent was removed, and the mixture was dried under vacuum to obtain compound 5 in a 98% yield.

[0289]

[0290] Compound 5 (4.89 g, 1.05 eq.), compound 6 (5.70 g, 1.00 eq.), p-toluenesulfonic acid monohydrate (p-TsOH·H ２ O) (0.521 g, 0.3 eq.) and 15 mL of toluene were added and stirred at 120°C for 5 hours. After cooling, 100 mL of ethyl acetate, 50 mL of acetonitrile, and 50 mL of saturated aqueous sodium bicarbonate were added, and the organic layer was separated. The organic layer was dried over sodium sulfate, the solvent was removed, and the mixture was purified using a column to obtain compound (A-1) in a yield of 77%.

[0291] [Synthesis Examples 25 to 40] (Synthesis of Radiation-Sensitive Acid Generators (A-2) to (A-17)) Compounds represented by the above formulae (A-2) to (A-17) were synthesized in the same manner as in Synthesis Example 24, except that the precursors and intermediates were appropriately changed.

[0292] [Acid diffusion controller] B-1 to B-6: Compounds represented by the following formulas (B-1) to (B-6)

[0293]

[0294] [Solvents] F-1 to F-2: Solvents F-1 to F-2 below F-1: Propylene glycol monomethyl ether acetate F-2: Propylene glycol monomethyl ether

[0295] [Preparation of Radiation-Sensitive Composition for Exposure to Extreme Ultraviolet (EUV)] [Example 1] 100 parts by mass of (P-1) as the polymer [A], 50 parts by mass of (A-1) as the radiation-sensitive acid generator, 15 parts by mass of (B-6) as the acid diffusion controller, 7.0 parts by mass of (E-2) as the high fluorine content polymer, and 4,280 parts by mass of (F-1) and 1,830 parts by mass of (F-2) as solvents were mixed together, and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-1).

[0296] [Examples 2 to 36 and Comparative Examples 1 to 3] Radiation-sensitive compositions (J-2) to (J-36) and (CJ-1) to (CJ-3) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 3 below were used.

[0297]

[0298] <Formation of Resist Pattern Using Radiation-Sensitive Composition for EUV Exposure> A composition for forming a bottom antireflective coating (Brewer Science's ARC66) was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron Limited's CLEAN TRACK ACT12), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. The radiation-sensitive composition for EUV exposure prepared above was applied to this bottom antireflective coating using the spin coater, and baked at 130°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 55 nm. Next, this resist film was exposed to light using an EUV exposure system (ASML's NXE3300) with NA=0.33, illumination conditions: Conventional s=0.89, and a mask: imecDEFECT32FFR02. After the exposure, PEB was performed for 60 seconds at 120° C. Thereafter, the resist film was subjected to alkaline development using a 2.38% by mass aqueous solution of TMAH as an alkaline developer, and after development, the resist film was washed with water and further dried to form a positive resist pattern (32 nm line and space pattern).

[0299] <Evaluation> The resist patterns formed using the above radiation-sensitive compositions for EUV exposure were evaluated for sensitivity, CDU performance, and LWR performance according to the methods described below. The results are shown in Table 4. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0300] [Sensitivity] In forming a resist pattern using the radiation-sensitive composition for EUV exposure, the exposure dose for forming a 32 nm line and space pattern is defined as the optimum exposure dose Eop, and this optimum exposure dose is defined as the sensitivity (mJ / cm ２ The sensitivity was 35 mJ / cm ２ The following cases are considered "good" and 35 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0301] [CDU Performance] A resist pattern was formed by adjusting the mask size so that a 25 nm contact hole pattern was formed by irradiating the Eop exposure dose calculated above. The formed resist pattern was observed from above using the scanning electron microscope. The hole diameter was measured at 16 points within a 500 nm range to determine the average value, and this average value was measured at a total of 500 points at any point. The 1 sigma value was calculated from the distribution of the measured values, and this was used as the CDU performance (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, and the better the performance. CDU performance can be evaluated as "good" when it is 2.0 nm or less, and "poor" when it is greater than 2.0 nm.

[0302] [LWR Performance] A resist pattern was formed by irradiating the resist with the optimal exposure dose Eop determined in the sensitivity evaluation described above, and adjusting the mask size to form a 32 nm line-and-space pattern. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 50 points, and a 3 sigma value was calculated from the distribution of the measured values. This 3 sigma value was used as the LWR performance (nm). The smaller the LWR value, the smaller the line chatter and the better the result. The LWR performance was evaluated as "good" when it was 2.5 nm or less, and as "poor" when it exceeded 2.5 nm.

[0303]

[0304] As is clear from the results in Table 4, the radiation-sensitive compositions of the examples all exhibited good performance in terms of sensitivity, CDU, and LWR.

[0305] The radiation-sensitive composition and pattern forming method of the present invention enable the formation of highly sensitive resist patterns with excellent CDU and LWR performance, and are therefore suitable for use in the fabrication of semiconductor devices, which are expected to become increasingly miniaturized in the future.

Claims

1. A polymer containing a structural unit having an acid-dissociable group, A radiation-sensitive acid generator containing a primary organic acid anion and a primary onium cation, An acid diffusion control agent comprising a second organic acid anion and a second onium cation, which generates an acid having a higher pKa than the acid generated from the above-mentioned radiation-sensitive acid generator upon irradiation with radiation, Solvent and Includes, The above-mentioned first organic acid anion comprises an acid anion portion and an aromatic ring having at least both a first substituent and a second substituent, wherein the first substituent and the second substituent are each independently a hydroxyl group, a sulfo group, or a sulfanyl group. A radiation-sensitive composition comprising at least one selected from the group consisting of the above polymer, the above radiation-sensitive acid generator, and the above acid diffusion control agent, which contains an iodine group.

2. The radiation-sensitive composition according to claim 1, wherein at least one of the first substituent and the second substituent is a hydroxyl group.

3. The radiation-sensitive composition according to claim 1, wherein the first substituent and the second substituent are located at the ortho position.

4. The radiation-sensitive composition according to claim 1, wherein the aromatic ring is a benzene ring.

5. The radiation-sensitive composition according to claim 1, wherein at least one selected from the group consisting of the polymer, the radiation-sensitive acid generator, and the acid diffusion control agent includes an iodine group-containing aromatic ring structure.

6. The radiation-sensitive composition according to claim 1, wherein at least one selected from the group consisting of the above-mentioned acid-dissociable group, the above-mentioned first organic acid anion, and the above-mentioned second organic acid anion contains an iodine group-containing aromatic ring structure.

7. The above-mentioned acid-dissociable group comprises an iodine-containing aromatic ring structure, wherein the radiation-sensitive composition is as described in claim 1.

8. The radiation-sensitive composition according to claim 1, wherein the structural unit having the above-mentioned acid-dissociable group is a structural unit represented by the following formula (3-4). 【Chemistry 1】 (In formula (3-4), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these independently represents either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. Each of the 3a values ​​is an independent integer between 1 and 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from one another. R Ｌ１１ R is a halogen atom, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or alkoxy group. Ｌ１１ (This is an iodine atom.)

9. The radiation-sensitive composition according to claim 5 or 6, wherein the number of iodine groups in the above-mentioned iodine group-containing aromatic ring structure is one, two, or three.

10. The radiation-sensitive composition according to claim 5 or 6, wherein the aromatic ring in the above-mentioned iodine group-containing aromatic ring structure is a benzene ring.

11. The above acid anion portion is a sulfonic acid anion. The radiation-sensitive composition according to any one of claims 1 to 6, wherein a fluorine atom or a fluorinated hydrocarbon group is bonded to a carbon atom adjacent to the sulfur atom of the sulfonic acid anion.

12. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the second organic acid anion has a sulfonic acid anion or a carboxylic acid anion (provided that if the second organic acid anion has a sulfonic acid anion, neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfur atom of the sulfonic acid anion).

13. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the first organic acid anion and the second organic acid anion each independently include an -O-, -CO-, a cyclic structure, or a combination thereof.

14. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the first onium cation and the second onium cation each independently contain at least one of a fluoro group and an iodine group.

15. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the first onium cation and the second onium cation are sulfonium cations.

16. The above-mentioned radiation-sensitive acid generator is the radiation-sensitive composition according to claim 1, represented by the following formula (G-1). 【Chemistry 2】 (In formula (G-1), L １ This is an alkylene group having 1 to 6 carbon atoms, which may be a single bond, an ether bond, or an ester bond, or which may contain an ether bond or an ester bond. R １ and R ２ is each independently a hydroxy group, a sulfo group or a sulfanyl group. R ３ and R ４ Each of these is independently a hydroxyl group, a carboxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxyl group, an amino group, or a C1-C10 alkoxy group, a C1-C20 alkyl group, a C1-C20 alkoxy group, a C2-C10 alkoxycarbonyl group, a C2-C20 acyloxy group, or a C1-C20 alkylsulfonyloxy group, or -NR ８ -C(=O)-R ９ Or -NR ８ -C(=O)-OR ９ That is. R ８ R is a C1-C6 alkyl group which may contain a hydrogen atom, or a halogen atom, a hydroxyl group, a C1-C6 alkoxy group, a C2-C6 acyl group, or a C2-C6 acyloxy group. ９ This group is an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and may also contain a halogen atom, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms. R ５ is, g ４ When it is 1, it is a single bond or a divalent linking group having 1 to 20 carbon atoms, g ４ When it is 0, (g) has 1 to 20 carbon atoms. １ It is a linking group with a +1 valence. Rf １ ~Rf ４ Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one of them is either a fluorine atom or a trifluoromethyl group. Rf １ and Rf ２ These may combine to form a carbonyl group. g １ g is an integer between 1 and 3. ２ and g ３ Each of these is an independent integer between 0 and 2. ４ g is either 0 or 1. ５ g is an integer between 0 and 3. ６ g is an integer between 0 and 2. ７ is 0 or 1. However, g ２ +g ５ (This is an integer between 1 and 5.)

17. In the above formula (G-1), g ４ The radiation-sensitive composition according to claim 16, wherein is 1.

18. In the above formula (G-1), g ４ is 1, g ２ is 0, and g ５ The radiation-sensitive composition according to claim 16, wherein is an integer from 1 to 3.

19. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the polymer further comprises a structural unit having a phenolic hydroxyl group.

20. A step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 6 to a substrate, The process of exposing the above-mentioned resist film, The process involves developing the exposed resist film with a developer solution. A pattern formation method, including the following.

21. The pattern forming method according to claim 20, wherein the exposure is performed using extreme ultraviolet light or an electron beam.

22. A radiation-sensitive acid generator represented by the following formula (G-1). 【Transformation 3】 (In formula (G-1), L １ This is an alkylene group having 1 to 6 carbon atoms, which may be a single bond, an ether bond, or an ester bond, or which may contain an ether bond or an ester bond. R １ and R ２ These are, independently, a hydroxyl group, a sulfo group, or a sulfanyl group. R ３ and R ４ Each of these is independently a hydroxyl group, a carboxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxyl group, an amino group, or a C1-C10 alkoxy group, a C1-C20 alkyl group, a C1-C20 alkoxy group, a C2-C10 alkoxycarbonyl group, a C2-C20 acyloxy group, or a C1-C20 alkylsulfonyloxy group, or -NR ８ -C(=O)-R ９ Or -NR ８ -C(=O)-OR ９ That is. R ８ R is a C1-C6 alkyl group which may contain a hydrogen atom, or a halogen atom, a hydroxyl group, a C1-C6 alkoxy group, a C2-C6 acyl group, or a C2-C6 acyloxy group. ９ This group is an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and may also contain a halogen atom, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms, or an acyloxy group having 2 to 6 carbon atoms. R ５ is, g ４ When it is 1, it is a single bond or a divalent linking group having 1 to 20 carbon atoms, g ４ When it is 0, (g) has 1 to 20 carbon atoms. １ It is a linking group with a +1 valence. Rf １ ~Rf ４ Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one of them is either a fluorine atom or a trifluoromethyl group. Rf １ and Rf ２ These may combine to form a carbonyl group. g １ g is an integer between 1 and 3. ２ and g ３ Each of these is an independent integer between 0 and 2. ４ g is either 0 or 1. ５ g is an integer between 0 and 3. ６ g is an integer between 0 and 2. ７ is 0 or 1. However, g ２ +g ５ (This is an integer between 1 and 5.)

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