Radiation-sensitive composition and pattern formation method

Abstract

Provided are a radiation-sensitive composition and a pattern formation method wherein sensitivity, CDU performance, and development defect suppression can be demonstrated at a sufficient level when next-generation technology is applied. [Solution] This radiation-sensitive composition includes: a polymer that includes a structural unit (I) represented by formula (1); a high-fluorine-content polymer that has a higher mass content of fluorine atoms than the aforementioned polymer; one or more types of onium salts including an organic acid anion and an onium cation; and a solvent, wherein at least some of the organic acid anions in the onium salt or salts include an iodine-substituted aromatic ring structure. (In formula (1), Rα is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group; Ar is an aromatic ring with 5-20 members and a valence of (p+q+r+1); R11 is a hydrogen atom or a C1-20 monovalent organic group; in cases in which a plurality of R11 moieties are present, the plurality of R11 moieties are the same as or different from each other; R12 is a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, or an acyl group; in cases in which a plurality of R12 moieties are present, the plurality of R12 moieties are the same as or different from each other; p and q are each independently an integer from 1 to 6; and r is an integer from 0 to 3.)

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] The photolithography technology described above uses short-wavelength radiation such as ArF excimer lasers, or combines this radiation with liquid immersion lithography to promote pattern miniaturization. Next-generation technologies are being developed that utilize even shorter-wavelength radiation such as electron beams, X-rays, and extreme ultraviolet (EUV), and resist materials containing polymers with benzene rings that have improved radiation absorption efficiency are also being considered (WO 2021 / 106535).

[0004] International Publication No. 2021 / 106535

[0005] In the above-mentioned next-generation technologies, in addition to various resist performances such as critical dimension uniformity (CDU) performance, which is an index of sensitivity and uniformity of line width and hole diameter, a sufficient level of development defect suppression, which suppresses defects during development, is also required.

[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 development defect suppression when next-generation technology is applied.

[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 (hereinafter also referred to as a "base polymer") containing a structural unit (I) represented by the following formula (1); a high-fluorine content polymer having a higher mass content of fluorine atoms than the above polymer; one or more onium salts containing an organic acid anion and an onium cation; and a solvent, wherein at least a part of the organic acid anions in the onium salt contain an iodine-substituted aromatic ring structure. (In formula (1), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ar is a (p+q+r+1)-valent aromatic ring having 5 to 20 ring members. R １１ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. １１ If there are multiple R １１ are the same or different. １２ is a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, or an acyl group. １２ If there are multiple R １２ are the same or different. p and q are each independently an integer of 1 to 6. r is an integer of 0 to 3.

[0009] This radiation-sensitive composition can exhibit excellent sensitivity, CDU performance, and development defect suppression during pattern formation. Although the reason for this is unclear, it is presumed as follows. The structural unit (I) contained in the base polymer and the iodine-substituted aromatic ring structure contained in the onium salt increase the secondary electron generation efficiency, resulting in high sensitivity of the radiation-sensitive composition. Furthermore, when the organic acid anion of the onium salt contains an iodine-substituted aromatic ring structure, acid diffusion can be controlled by the molecular weight of the iodine atom, thereby improving CDU performance. Furthermore, the polymer contains the structural unit (I), which reduces the contact angle of the resist film and increases its affinity with the developer. Additionally, the use of a high-fluorine-content polymer in combination with the base polymer allows the surface properties of the resist film to be appropriately controlled. It is presumed that these combined effects enable the aforementioned resist performance and development defect suppression to be exhibited.

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

[0011] In this pattern forming method, the above-mentioned radiation-sensitive composition is used, which provides excellent sensitivity, CDU performance, and suppression of development defects, and therefore a high-quality resist pattern can be efficiently formed.

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

[0013] Radiation-Sensitive Composition The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a base polymer, a high-fluorine content polymer, one or more onium salts, and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0014] <Polymer> The polymer (i.e., base polymer) is an aggregate of polymer chains containing the structural unit (I). In addition to the structural unit (I), the base polymer may also contain a structural unit (II) having a phenolic hydroxyl group or the like, a structural unit (III) having an acid-dissociable group, a structural unit (IV) containing a lactone structure or the like, etc. Each structural unit will be described below.

[0015] (Structural Unit (I)) The structural unit (I) is represented by the following formula (1). (In formula (1), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ar is a (p+q+r+1)-valent aromatic ring having 5 to 20 ring members. R １１ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. １１ If there are multiple R １１ are the same or different. １２ is a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, or an acyl group. １２ If there are multiple R １２are the same or different. p and q are each independently an integer of 1 to 6. r is an integer of 0 to 3.

[0016] Examples of the aromatic ring having 5 to 20 ring members represented by Ar include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, an anthracene ring, a phenalene ring, a phenanthrene ring, a pyrene ring, a fluorene ring, and a perylene ring; aromatic heterocycles such as a furan ring, a pyrrole ring, a thiophene ring, a phosphole ring, a pyrazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, and a triazine ring; and combinations thereof. Combinations may include fused rings (a structure in which two adjacent rings share one edge (a bond between two adjacent atoms)), ring aggregates in which adjacent rings are bonded by a single bond, or combinations thereof. The aromatic ring is preferably a benzene ring. Ar has a structure in which (p+q+r+1) hydrogen atoms have been removed from the above aromatic ring.

[0017] R １１ Examples of the monovalent organic group having 1 to 20 carbon atoms and represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between the 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. Note that an "organic group" is a group having at least one carbon atom.

[0018] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms 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.

[0019] 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.

[0020] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group and a cyclohexyl 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.

[0021] 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.

[0022] Examples of heteroatoms constituting the divalent or monovalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, halogen atoms, etc. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0023] 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.

[0024] 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.

[0025] R １２ As the alkyl group represented by the formula (I), a linear or branched alkyl group having 1 to 10 carbon atoms shown in the above-mentioned monovalent chain hydrocarbon group having 1 to 20 carbon atoms can be suitably used.

[0026] R １２Examples of the fluorinated alkyl group represented by the formula (I) include linear or branched fluorinated alkyl groups having 1 to 10 carbon atoms, such as trifluoromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 1,1,1,3,3,3-hexafluoropropyl group, heptafluoro n-propyl group, heptafluoro i-propyl group, nonafluoro n-butyl group, nonafluoro i-butyl group, nonafluoro t-butyl group, 2,2,3,3,4,4,5,5-octafluoro n-pentyl group, tridecafluoro n-hexyl group, and 5,5,5-trifluoro-1,1-diethylpentyl group.

[0027] R １２ Examples of the acyl group represented by the formula (I) include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as an acetyl group, a propionyl group, a butyryl group, an acryloyl group, a methacryloyl group, and a benzoyl group.

[0028] p and q are each independently preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and even more preferably 1 or 2. In particular, p is preferably 2.

[0029] r is preferably an integer of 0 to 2, and more preferably 0 or 1.

[0030] The structural unit (I) is preferably represented by the following formulas (1-1) to (1-32).

[0031]

[0032]

[0033] In the above formulas (1-1) to (1-32), R α is synonymous with the above formula (1).

[0034] The lower limit of the content of the structural unit (I) in the polymer (total content when multiple types of structural unit (I) are present) is preferably 1 mol %, more preferably 5 mol %, and even more preferably 8 mol %, based on all structural units constituting the polymer. The upper limit of the content is preferably 50 mol %, more preferably 40 mol %, even more preferably 30 mol %, and particularly preferably 20 mol %. By setting the content of the structural unit (I) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity, CDU performance, and development defect suppression.

[0035] (Structural Unit (II)) The structural unit (II) is a structural unit having a phenolic hydroxyl group. However, structural units (II) do not include those corresponding to the structural unit (I) and the structural unit (III) described below. When the polymer contains the structural unit (II), the solubility in a developer can be more appropriately adjusted, thereby further improving the sensitivity of the radiation-sensitive composition. 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 suitable for 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):

[0036] (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 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. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４is an integer from 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0037] 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.

[0038] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0039] R １０２ Examples of the alkyl group in the formula (I) 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.

[0040] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0041] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0042] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0043] The structural unit (II) is preferably a structural unit represented by the following formulas (2-1) to (2-10) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-10)"), or the like.

[0044]

[0045] In the above formulas (2-1) to (2-10), R β is the same as the above formula (2).

[0046] 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 polymer is preferably 10 mol%, more preferably 15 mol%, and even more preferably 20 mol%. The upper limit of the content is preferably 60 mol%, more preferably 55 mol%, and even more preferably 45 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 resolution.

[0047] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferred that the polymerization be carried out in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (for example, an acyl group), and then the structural unit (II) is obtained by deprotecting the phenolic hydroxyl group by hydrolysis.

[0048] (Structural Unit (III)) The structural unit (III) is a structural unit having an acid-dissociable group. However, structural units (III) do not include those corresponding to the structural unit (II). The structural unit (III) 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. 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 (III-1)") is preferred.

[0049]

[0050] In the above formula (3), R １７is 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-. １１ａ is a substituted or unsubstituted arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.

[0051] The above R １７ From the viewpoint of copolymerizability of the monomer that gives the structural unit (III-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0052] 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.

[0053] L １１ａ Examples of the substituent that the arenediyl group represented by the formula (I) may have 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.

[0054] L １１ａ The alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, and acyloxy group as the substituent of the formula (2) are R １０２ Suitable 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.

[0055] 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 10 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.

[0056] The above R １８ ~R ２０ Examples of the monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, and a monovalent linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms.

[0057] The above R １８ ~R ２０ The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is １１ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably used.

[0058] The above R １８ The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1) is １１ A monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in the above formula can be suitably used.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 The alicyclic structure formed by combining these together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0063] 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.

[0064] Examples of the structural unit (III-1) include structural units represented by the following formulas (3-1) to (3-9) (hereinafter also referred to as "structural units (III-1-1) to (III-1-9)").

[0065]

[0066] In the above formulas (3-1) to (3-9), 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 0 or 1.

[0067] 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 As the alkyl group, a methyl group or an ethyl group is preferred.

[0068] Furthermore, the resin may contain structural units represented by the following formulas (1f) to (2f) as the structural unit (III).

[0069]

[0070] 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.

[0071] 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.

[0072] When the resin contains the structural unit (III), the lower limit of the content of the structural unit (III) (total content when multiple types of structural unit (III) are present) relative to all structural units constituting the base resin is preferably 20 mol%, more preferably 30 mol%, and particularly preferably 40 mol%. The upper limit of the content is preferably 70 mol%, more preferably 60 mol%, still more preferably 50 mol%, and particularly preferably 70 mol%. By setting the content of the structural unit (III) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0073] (Structural Unit (IV)) The structural unit (IV) 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 (IV), 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.

[0074] Examples of the structural unit (IV) include structural units represented by the following formulae (T-1) to (T-11).

[0075]

[0076] 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 R Ｌ５ 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.

[0077] 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.

[0078] The above L ２Examples 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 -CO-, -O-, -NH-, and -S-.

[0079] Of these, the structural unit (IV) 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.

[0080] 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 all 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% or less. By setting the content of the structural unit (IV) 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.

[0081] (Method of Synthesizing Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a known radical polymerization initiator or the like.

[0082] 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 5,000. The upper limit of the Mw is preferably 20,000, more preferably 15,000, even more preferably 10,000, and particularly preferably 8,000. When the Mw of the polymer is within the above range, the heat resistance and developability of the resulting resist film are good.

[0083] 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.

[0084] The Mw and Mn of the polymer herein are values ​​measured using gel permeation chromatography (GPC) under the following conditions: GPC columns: two G2000HXL columns, one G3000HXL column, and one G4000HXL column (all manufactured by Tosoh Corporation); column temperature: 40°C; elution solvent: tetrahydrofuran; flow rate: 1.0 mL / min; sample concentration: 1.0 mass%; sample injection volume: 100 μL; detector: differential refractometer; standard material: monodisperse polystyrene.

[0085] The content of the polymer is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0086] <High-Fluorine Content Polymer> The high-fluorine content polymer is a polymer having a higher mass content of fluorine atoms than the base polymer. The high-fluorine content polymer is preferably, but not necessarily, unevenly distributed in the surface layer of the resist film relative to the base polymer. The inclusion of the high-fluorine content polymer makes it possible to control the state of the resist film surface and the component distribution in the resist film to desired states, thereby optimizing the development characteristics of the resulting resist film.

[0087] The high fluorine content polymer preferably has a structure that changes its solubility in an alkaline aqueous solution under the action of an alkali, thereby improving the solubility of the resist film in an alkaline developer during development and suppressing the occurrence of development defects.

[0088] The high-fluorine content polymer preferably has a fluorine atom-containing structural unit represented by the following formula (f-1) (hereinafter also referred to as structural unit (V)): By having the structural unit (V), the high-fluorine content polymer has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0089] The structural unit (V) is roughly classified into two types: (x) a structural unit having an alkali-soluble group, and (y) a structural unit 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-, 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.

[0090] When the structural unit (V) has an alkali-soluble group (x), R Ｆ 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 (V) has an alkali-soluble group (x), it is possible to increase the affinity for an alkaline developer and suppress development defects. As the structural unit (V) having an alkali-soluble group (x), A １ is an oxygen atom and W １It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0091] When the structural unit (V) 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-* 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 -COO-* 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 (V) has an alkali-dissociable group (y), the surface of the resist film changes from hydrophobic to hydrophilic in the alkaline development step. As a result, the affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. In other words, the alkali-dissociable group (y) in the structural unit (V) can suitably function as a structure whose solubility in an alkaline aqueous solution changes under the action of alkali. Examples of the structural unit (V) having an alkali-dissociable group (y) include A １ is -COO-*, and R Ｆ Or W １It is particularly preferred that both of them have a fluorine atom.

[0092] R Ｃ 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.

[0093] 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 more preferably a group having a norbornane lactone structure.

[0094] Examples of the structural unit (V) include structural units represented by the following formulae (f-1-1) to (f-1-8).

[0095]

[0096] In the formula, R Ｃ has the same meaning as the above formula (f-1).

[0097] When the high-fluorine-content polymer has the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol%, based on all structural units constituting the high-fluorine-content polymer. The content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (V) within the above range, it is possible to further improve the water repellency as well as the development defect suppression property.

[0098] The high fluorine content polymer may have a structural unit represented by the following formula (6) (hereinafter also referred to as "structural unit (VI)") in addition to or instead of the structural unit (V).

[0099] In the above formula (6), R １３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, —COO—, or —SO ２ ONH-, -CONH- or -OCONH-. 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.

[0100] The above R １３ 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.

[0101] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a single bond and —COO— are preferred, and —COO— is more preferred.

[0102] 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.

[0103] The above R １４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0104] 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 1,1,1,3,3,3-hexafluoropropyl group, a 5,5,5-trifluoro-1,1-diethylpentyl group, and a 1,1,1,2,2,3,3-heptafluoro-6-methyl-4-octyl group are even more preferable.

[0105] When the high-fluorine-content polymer has the structural unit (VI), the lower limit of the content of the structural unit (VI) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of the structural unit (VI) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, and the uneven distribution of fluorine atoms in the surface layer of the resist film can be further promoted.

[0106] The lower limit of Mw of the high fluorine content polymer is preferably 3,000, more preferably 4,000, even more preferably 5,000, and particularly preferably 6,000. The upper limit of Mw is preferably 30,000, more preferably 15,000, even more preferably 12,000, and particularly preferably 8,500.

[0107] The Mw / Mn of the high fluorine content polymer is usually at least 1, and more preferably at least 1.1. The Mw / Mn is usually at most 5, preferably at most 3, more preferably at most 2.5, and even more preferably at most 2.2.

[0108] The content of the high-fluorine-containing polymer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 1.5 parts by mass or more, relative to 100 parts by mass of the base polymer. The content is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and particularly preferably 5 parts by mass or less. By setting the content of the high-fluorine-containing polymer within the above range, the high-fluorine-containing polymer can be more effectively localized to the surface layer of the resist film, thereby suppressing development defects during development and suppressing elution from the upper part of the pattern, thereby improving development properties. The radiation-sensitive composition may contain one or more high-fluorine-containing polymers.

[0109] (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.

[0110] <Onium Salt> The onium salt contains an organic acid anion and an onium cation, and is a component that generates acid upon exposure. At least a portion of the organic acid anion in the onium salt contains an iodine-substituted aromatic ring structure. The iodine atom exhibits very high absorption of radiation such as EUV having a wavelength of 13.5 nm, thereby enhancing sensitivity. Furthermore, when the organic acid anion of the onium salt contains an iodine-substituted aromatic ring structure, acid diffusion can be controlled by the molecular weight of the iodine atom, thereby improving CDU performance.

[0111] As the aromatic ring in the iodine-substituted aromatic ring structure, an aromatic ring having 5 to 20 ring members represented by Ar in the above formula (1) can be suitably used. Among them, as the aromatic ring in the iodine-substituted aromatic ring structure, a benzene ring is preferable. The iodine-substituted aromatic ring structure is a structure in which some of the hydrogen atoms in these aromatic rings are substituted with iodine groups.

[0112] It is preferred that at least some of the onium cations in the onium salt contain an aromatic ring structure having a fluorine atom or an iodine-substituted aromatic ring structure. Radiation such as EUV with a wavelength of 13.5 nm is highly absorbed by fluorine atoms and iodine atoms, thereby enhancing the sensitivity of the radiation-sensitive composition. The term "aromatic ring structure having fluorine" includes not only a structure in which a fluorine atom is directly bonded to an aromatic ring structure, but also a structure in which a fluorine atom is bonded to an aromatic ring structure via another atom (for example, a structure in which a fluorine atom is bonded to a substituent bonded to an aromatic ring structure).

[0113] In this embodiment, as described above, at least a portion of the organic acid anions in the onium salt contain an iodine-substituted aromatic ring structure. Therefore, when at least a portion of the onium cations in the onium salt contain an aromatic ring structure having a fluorine atom, the iodine-substituted aromatic ring structure and the aromatic ring structure having a fluorine atom may be present in the same compound or in different compounds.

[0114] Although the form of the onium salt contained in the radiation-sensitive composition is not particularly limited, it is preferable that the onium salt be at least one selected from the group consisting of a radiation-sensitive acid generator containing the organic acid anion and the onium cation, and an acid diffusion controller containing the organic acid anion and the onium cation and generating an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The different functions of these are described below.

[0115] The acid generated by exposure of an onium salt is thought to have two functions in the radiation-sensitive composition depending on the strength of the acid. The first function is to dissociate the acid-dissociable group of a structural unit of the polymer containing the acid-dissociable group, thereby generating a carboxyl group or the like. An onium salt having this first function is called a radiation-sensitive acid generator. The second function is to inhibit the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas by salt exchange without substantially dissociating the acid-dissociable group of the polymer under pattern formation conditions using the radiation-sensitive composition. An onium salt having this second function is called an acid diffusion controller (also called a "photodegradable base"). The acid generated from the acid diffusion controller can be said to be a relatively weaker acid (having a higher pKa) than the acid generated from the radiation-sensitive acid generator. Whether an onium salt functions as a radiation-sensitive acid generator or an acid diffusion controller depends on the energy required for dissociation of the acid-dissociable group in the polymer, the acidity of the onium salt, etc. 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.

[0116] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0117] When the radiation-sensitive composition contains the radiation-sensitive acid generator, the polarity of the polymer in the exposed area increases, and the polymer in the exposed area becomes soluble in a developer in the case of development with an aqueous alkali solution, while becoming poorly soluble in the developer in the case of development with an organic solvent.

[0118] Furthermore, 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 pattern developability and CDU performance.

[0119] Regardless of the onium salt's incorporation form, the organic acid anion is preferably at least one selected from the group consisting of sulfonate anions, carboxylate anions, and sulfonimide anions. The onium cation is preferably at least one selected from the group consisting of sulfonium cations and iodonium cations. The onium salt can efficiently exhibit the above-described functions by combining these structures.

[0120] The acid generated upon exposure includes those which generate sulfonic acid, carboxylic acid, and sulfonimide upon exposure, corresponding to the above organic acid anions.

[0121] For example, onium salts that give sulfonic acids upon exposure include: (1) compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are bonded to a carbon atom at the α- or β-position relative to the sulfur atom in the sulfonate anion; and (2) compounds in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to a carbon atom at the α- or β-position relative to the sulfur atom in the sulfonate anion.

[0122] Examples of onium salts that give carboxylic acids upon exposure include: (3) compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are bonded to the carbon atom at the α- or β-position relative to the sulfur atom in the carboxylate anion; and (4) compounds in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom at the α- or β-position relative to the sulfur atom in the carboxylate anion.

[0123] Among these, the radiation-sensitive acid generator is preferably one corresponding to the above-mentioned (1), and the acid diffusion controller is preferably one corresponding to the above-mentioned (2), (3), or (4), with (2) or (4) being particularly preferred.

[0124] <Radiation-sensitive Acid Generator> The radiation-sensitive acid generator contains an organic acid anion and an onium cation. The radiation-sensitive acid generator is preferably represented by the following formula (A-1) or (A-2).

[0125]

[0126] In formulas (A-1) and (A-2), L １ 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.

[0127] R １ is 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.

[0128] Of these, R １ 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.

[0129] R ２When p is 1, it is a single bond or a divalent linking group having 1 to 20 carbon atoms, and when p is 2 or 3, it is a trivalent or tetravalent linking group having 1 to 20 carbon atoms. Examples of such linking groups include R １１ Examples of heteroaromatic rings include groups in which one hydrogen atom has been removed from a monovalent organic group having 1 to 20 carbon atoms, represented by the formula:

[0130] 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.

[0131] R ３ , R ４ , R ５ , R ６ and R ７ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. When the onium cation of the radiation-sensitive acid generator has a fluorine atom, R ３ , R ４ and R ５ At least one of R contains one or more fluorine atoms, ６ and R ７ At least one of R contains one or more fluorine atoms. ３ , R ４ and R ５Any two of the above may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, alkynyl groups having 2 to 12 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 12 carbon atoms. In addition, some or all of the hydrogen atoms of these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amide groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the carbon atoms of these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups, or sulfonate ester bonds.

[0132] p is an integer that satisfies 1≦p≦3. q and r are integers that satisfy 0≦q≦5, 0≦r≦3, and 0≦q+r≦5. q is preferably an integer that satisfies 1≦q≦3, more preferably 2 or 3. r is preferably an integer that satisfies 0≦r≦2.

[0133] Examples of organic acid anions of the radiation-sensitive acid generators represented by the above formulas (A-1) and (A-2) include, but are not limited to, those shown below. Note that all of the organic acid anions shown below have an iodine-substituted aromatic ring structure, but as organic acid anions that do not have an iodine-substituted aromatic ring structure, structures in which the iodine atom in the following formulas is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can be suitably used.

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155]

[0156]

[0157]

[0158]

[0159] The onium cation in the radiation-sensitive acid generator represented by formula (A-1) above is preferably represented by formula (Q-1) below.

[0160]

[0161] 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 preferably represents a fluorine atom or a group having one or more fluorine atoms. 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. When n1 is 1 or greater and n2 is 1 or greater, Ra1 and Ra2 may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom).

[0162] The substituents represented by Ra1 and Ra2 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] Each of the groups Ra1 and Ra2 may further have a substituent, such as a halogen atom such as a fluorine atom (preferably a fluorine atom), 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.

[0170] Examples of the halogen atom for Ra1 and Ra2 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and an iodine atom being preferred.

[0171] 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.

[0172] 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.

[0173] Ra3 is preferably a fluorine atom or a group having one or more fluorine atoms. Examples of the group having a fluorine atom 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 fluorine atom. 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 are particularly preferred.

[0174] Ra3 is a fluorine atom, an iodine atom, or CF ３ is preferred, and a fluorine atom or an iodine atom is more preferred.

[0175] As Ra3, the above-mentioned substituents represented by Ra1 and Ra2 may be adopted.

[0176] n1 and n2 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0177] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0178] (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 fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=2 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ A combination in which:

[0179] Specific examples of such onium cations represented by the above formula (Q-1) include the following: All of the following are sulfonium cation moieties containing an aromatic ring structure having a fluorine atom, but onium cations that do not contain an aromatic ring structure having a fluorine atom include fluorine atoms and CF in the following formula: ３ A structure in which the fluorine atom is substituted with an atom or group other than a fluorine atom, such as a hydrogen atom or other substituent, can be preferably employed.

[0180]

[0181]

[0182]

[0183] When the onium cation in the radiation-sensitive acid generator represented by formula (A-2) contains an aromatic ring structure having a fluorine atom, the onium cation is preferably a diaryliodonium cation having one or more fluorine atoms.

[0184] The radiation-sensitive acid generators represented by the formulas (A-1) and (A-2) can be synthesized by known methods, particularly by 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.

[0185] 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 generator (total amount when multiple types are present) is preferably 10 parts by mass, more preferably 20 parts by mass, still more preferably 30 parts by mass, and particularly preferably 40 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 70 parts by mass, more preferably 60 parts by mass, and still more preferably 50 parts by mass. This allows for excellent sensitivity and CDU performance to be exhibited during resist pattern formation.

[0186] <Acid Diffusion Controller> The acid diffusion controller contains an organic acid anion and an onium cation, and upon irradiation with radiation, generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator. The acid diffusion controller is preferably represented by the following formula (S-1) or (S-2):

[0187]

[0188] In formulas (S-1) and (S-2), R １Ｔ represents a hydrogen atom, a hydroxy group, a fluorine atom, a chlorine atom, an amino group, a nitro group, a cyano group, or an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, or an alkylsulfonyloxy group having 1 to 4 carbon atoms, which may be substituted with a halogen atom, or -NR ＴＡ -C(=O)-R ＴＢ Or -NR ＴＡ -C(=O)-OR ＴＢ It is. ＴＡ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ＴＢ is an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 8 carbon atoms.

[0189] The alkyl group having 1 to 6 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a cyclopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, an n-pentyl group, a cyclopentyl group, an n-hexyl group, and a cyclohexyl group. Examples of the alkyl moiety of the alkoxy group having 1 to 6 carbon atoms, the acyloxy group having 2 to 7 carbon atoms, and the alkoxycarbonyl group having 2 to 7 carbon atoms include the same as the specific examples of the alkyl group described above, and examples of the alkyl moiety of the alkylsulfonyloxy group having 1 to 4 carbon atoms include the specific examples of the alkyl group having 1 to 4 carbon atoms described above. The alkenyl group having 2 to 8 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a vinyl group, a 1-propenyl group, and a 2-propenyl group. Among these, R １ＴExamples of the alkyl group include a fluorine atom, a chlorine atom, a hydroxy group, an amino group, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an acyloxy group having 2 to 4 carbon atoms, and —NR ＴＡ -C(=O)-R ＴＢ , -NR ＴＡ -C(=O)-OR ＴＢ etc. are preferred.

[0190] R ３Ｔ , R ４Ｔ , R ５Ｔ , R ６Ｔ and R ７Ｔ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. When the onium cation of the acid diffusion controller has a fluorine atom, R ３Ｔ , R ４Ｔ and R ５Ｔ At least one of R contains one or more fluorine atoms, ６Ｔ and R ７Ｔ At least one of R contains one or more fluorine atoms. ３Ｔ , R ４Ｔ and R ５Ｔ Any two of the above may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, alkynyl groups having 2 to 12 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 12 carbon atoms. In addition, some or all of the hydrogen atoms of these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amide groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the carbon atoms of these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups, or sulfonate ester bonds.

[0191] L Ｔ is a single bond or a divalent linking group having 1 to 20 carbon atoms, and may contain an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group, or a carboxy group as a substituent. ＴIn terms of the remaining film ratio, is preferably a divalent linking group having 1 to 20 carbon atoms which may be substituted with the above-mentioned substituent.

[0192] md and nd are integers that satisfy 0≦md≦5, 0≦nd≦3, and 0≦md+nd≦5, but are preferably integers that satisfy 1≦md≦3 and 0≦nd≦2.

[0193] Examples of organic acid anions of the acid diffusion controller represented by formula (S-1) or (S-2) above include, but are not limited to, those shown below. Note that all of the organic acid anions shown below have an iodine-substituted aromatic ring structure, but the acid diffusion controller does not necessarily require an iodine-substituted aromatic ring structure. As organic acid anions that do not have an iodine-substituted aromatic ring structure, structures in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or another substituent, can be suitably used.

[0194]

[0195]

[0196]

[0197]

[0198]

[0199]

[0200] As the onium cation in the acid diffusion controller represented by the above formulas (S-1) and (S-2), the onium cation in the radiation-sensitive acid generator can be suitably used.

[0201] The acid diffusion controllers represented by the formulas (S-1) and (S-2) above can be synthesized by known methods, particularly by salt exchange reactions. Known acid diffusion controllers can also be used as long as they do not impair the effects of the present invention. Furthermore, the acid diffusion controllers of this embodiment also include those in which the organic acid anion and the onium cation share the same aromatic ring structure.

[0202] 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 amount when multiple types are present) is preferably 10 parts by mass, more preferably 20 parts by mass, even more preferably 30 parts by mass, and particularly preferably 40 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 70 parts by mass, more preferably 60 parts by mass, and even more preferably 50 parts by mass. This allows excellent sensitivity and CDU performance to be exhibited during resist pattern formation.

[0203] <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 at least the base polymer, the high-fluorine-content polymer, and the onium salt, as well as optional additives and the like.

[0204] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] Among these, alcohol-based solvents and ester-based solvents are preferred, polyhydric alcohol partial ether-based solvents and polyhydric alcohol partial ether acetate-based solvents are more preferred, and propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0212] <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.

[0213] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer, a high-fluorine-content polymer, an onium salt, 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 about 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.

[0214] <Pattern Forming Method> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly onto 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 (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film (hereinafter also referred to as a "development step").

[0215] According to the pattern forming method, a high-quality resist pattern can be formed because the radiation-sensitive composition is used, which has excellent sensitivity and CDU performance in the exposure step and excellent suppression of development defects in the development step. Each step will be described below.

[0216] [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 140°C, preferably 80°C to 120°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.

[0217] Furthermore, when the subsequent exposure step is carried out using radiation with a wavelength of 50 nm or less, it is preferable to use a polymer having the structural unit (I) and the structural unit (II), and optionally the structural unit (III), as the base polymer in the composition.

[0218] [Exposure Step] In this step (step (2) above), the resist film formed in the resist film formation step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion medium such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), 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, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0219] 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 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0220] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. 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.

[0221] 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.

[0222] 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.

[0223] 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).

[0224] 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.

[0225] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0226] <Synthesis of [Z] Monomer>

[0227] Synthesis Example 1: Synthesis of Compound (Z-1) Compound (Z-1) was synthesized according to the following reaction scheme.

[0228] Methyltriphenylphosphonium bromide (113 mmol) was added to a vessel containing tetrahydrofuran (150 mL) and cooled to -78°C. A 1.6 mol / L tetrahydrofuran solution (57 mL) of n-butyllithium was added dropwise to this vessel. The mixture was stirred at room temperature for 2 hours and cooled to 0°C. A 0.5 mol / L tetrahydrofuran solution (151 mL) of (P-1) (75.5 mmol) was added dropwise to this vessel and stirred at 0°C. A 2.0 mol / L aqueous hydrochloric acid solution was added, and the mixture was filtered through silica gel. Ethyl acetate was added to the filtrate, and the organic layer was washed with brine. The organic layer was dried over sodium sulfate and filtered. The target product was isolated by silica gel chromatography to obtain compound (Z-1).

[0229]

[0230] [Synthesis Examples 2 to 14: Synthesis of Compounds (Z-2) to (Z-14)] [Z] monomers represented by the following formulas (Z-2) to (Z-14) were synthesized by using the same procedure as in Synthesis Example 1, except that precursors were appropriately selected.

[0231]

[0232] <[A] 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" means a value when the total mass of the monomers used is taken as 100 parts by mass, and "mol %" means a value when the total number of moles of the monomers used is taken as 100 mol %.

[0233]

[0234] Polymer Synthesis Example 1: Synthesis of Polymer (A-1) The monomer compounds (Z-1), (M-2), and (M-7) were dissolved in propylene glycol monomethyl ether (200 parts by mass) to a molar ratio of 10 / 45 / 45. To this was added 2,2'-azobis(methyl isobutyrate) (10 mol%) as an initiator to prepare a monomer solution. Meanwhile, propylene glycol monomethyl ether (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. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. The polymerization solution was added dropwise to n-hexane (1,000 parts by mass) to coagulate and purify the polymer. To the recovered polymer, propylene glycol monomethyl ether (150 parts by mass), methanol (150 parts by mass), triethylamine (1.5 molar equivalents relative to the amount of compound (M-2) used), and water (1.5 molar equivalents relative to the amount of compound (M-2) used) were added. The mixture was refluxed at the boiling point and subjected to a hydrolysis reaction for 8 hours. After completion of the reaction, the solvent and triethylamine were distilled off under reduced pressure, and the resulting polymer was dissolved in acetone (150 parts by mass). The resulting polymer was added dropwise to water (2,000 parts by mass) to coagulate, and the resulting white powder was separated by filtration. The resulting mixture was dried at 50°C for 17 hours to obtain a white powdery polymer (A-1) in good yield.

[0235] [Polymer Synthesis Examples 2 to 29: Synthesis of Polymers (A-2) to (A-29)] Polymers (A-2) to (A-29) were synthesized in the same manner as in Polymer Synthesis Example 1, except that the monomer compositions shown in Table 1 were used.

[0236] The amounts of each structural unit used, Mw and Mw / Mn of the resulting polymer are shown in Table 1.

[0237]

[0238] Polymer Synthesis Example 30: Synthesis of Polymer (F-1) Compounds (M-9) and (M-15) were dissolved in 2-butanone (100 parts by mass relative to the total monomer amount) so that the molar ratio was 40 / 60. Azobisisobutyronitrile (5 mol % relative to the total monomer amount) was added as an initiator to prepare a monomer solution. Meanwhile, 2-butanone (50 parts by mass) was placed in an empty container and purged with nitrogen for 30 minutes. The container was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. After the dropwise addition was completed, the mixture was heated at 80°C for an additional 3 hours and then cooled to below 30°C. The polymerization solution was transferred to a separatory funnel, and hexane (150 parts by mass) was added to uniformly dilute the polymerization solution. Methanol (600 parts by mass) and water (30 parts by mass) were then added and mixed. After standing for 30 minutes, the lower layer was recovered, and the solvent was replaced with propylene glycol monomethyl ether acetate. In this way, a 10% propylene glycol monomethyl ether acetate solution of polymer (F-1) was obtained. Polymer (F-1) had Mw=7,200 and Mw / Mn=1.7.

[0239] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator (B) and acid diffusion controller (D) as onium salts, and the solvent (E) used in the preparation of the radiation-sensitive compositions of the following Examples and Comparative Examples are shown below.

[0240] [B] Radiation-sensitive Acid Generator Compounds represented by (B-1) to (B-12) were used as the radiation-sensitive acid generator.

[0241]

[0242]

[0243] [D] Acid Diffusion Controller Compounds represented by (D-1) to (D-8) were used as acid diffusion controllers.

[0244]

[0245] [E] Solvent E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether

[0246] [Example 1] 100 parts by mass of [A] polymer (A-1), 3 parts by mass (in terms of solids content) of [F] polymer (F-1), 45 parts by mass of [B] radiation-sensitive acid generator (B-1), [D] acid diffusion controller (D-1) in an amount of 45 mol% relative to the anion of (B-1), 5,500 parts by mass of [E] solvent (E-1), and 1,500 parts by mass of (E-2) were blended together. This mixture was filtered through a membrane filter having a pore size of 0.2 μm to prepare radiation-sensitive composition (R-1).

[0247] [Examples 2 to 46 and Comparative Examples 1 to 3] Radiation-sensitive compositions (R-2) to (R-46) and (CR-1) to (CR-3) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 2 below were used.

[0248]

[0249] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). Prebaking (PB) was performed at 100°C for 60 seconds, followed by cooling at 23°C for 30 seconds to form a 30-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300," ASML, NA=0.33, illumination conditions: Conventional s=0.89). The resist film was then subjected to PEB (post-exposure bake) at 100°C for 60 seconds. Next, development was carried out using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive-type 50 nm pitch, 25 nm contact hole pattern.

[0250] <Evaluation> The sensitivity, CDU performance, and number of development defects of each radiation-sensitive composition were evaluated by measuring each of the resist patterns formed above according to the methods described below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the resist patterns. The evaluation results are shown in Table 3 below.

[0251] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 25 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the sensitivity, the better. The sensitivity was 57 mJ / cm ２ If it is less than 57 mJ / cm, it is "A" (very good). ２ 60mJ / cm or more ２ Below "B" (good), 60mJ / cm ２ If it exceeded this, it was judged as "C" (poor).

[0252] [CDU Performance] Using the scanning electron microscope, a 25 nm contact hole pattern was observed from above, and a total of 800 lengths were measured at random points. The dimensional variation (3σ) was calculated and used as the CDU performance (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better performance. CDU performance was rated as "A" (very good) for CDU less than 3.6 nm, "B" (good) for CDU between 3.6 nm and 3.8 nm, and "C" (poor) for CDU greater than 3.8 nm.

[0253] [Number of Development Defects] A resist film was exposed to an optimum exposure dose and developed to form a 25 nm contact hole pattern. The number of defects on the wafer was measured using a defect inspection system (KLA-Tencor's "KLA2810"). Of the defects measured, defects with a diameter of 0.5 μm or less were determined to be originating from the resist film. The number of development defects was determined as "A" (very good) if the number of defects determined to be originating from the resist film was less than 30, "B" (good) if the number was 30 to 50, and "C" (poor) if the number was more than 50.

[0254]

[0255] As is clear from the results in Table 3, the radiation-sensitive compositions of the Examples were superior in sensitivity, CDU performance and development defect suppression to the Comparative Examples.

[0256] The radiation-sensitive composition and method for forming a resist pattern of the present invention can improve sensitivity, CDU performance, and the number of development defects compared to conventional methods, and therefore can be suitably used for forming fine resist patterns in lithography processes for various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A radiation-sensitive composition comprising: a polymer including a structural unit (I) represented by the following formula (1); a high-fluorine content polymer having a higher mass content of fluorine atoms than the above polymer; one or more onium salts including an organic acid anion and an onium cation; and a solvent, wherein at least a portion of the organic acid anions in the onium salt include an iodine-substituted aromatic ring structure. (In formula (1), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ar is a (p+q+r+1)-valent aromatic ring having 5 to 20 ring members. R １１ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. １１ When there are multiple R １１ are the same or different. １２ R is a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, or an acyl group. １２ When there are multiple R １２ are the same or different. p and q are each independently an integer of 1 to 6. r is an integer of 0 to 3.

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

3. The radiation-sensitive composition according to claim 1, wherein in the above formula (1), p and q each independently represent an integer of 1 to 3, r is 0 or 1, and 2≦p+q+r≦5 is satisfied.

4. The radiation-sensitive composition according to claim 1, wherein the content of said structural unit (I) in all structural units of said polymer is from 1 mol % to 30 mol %.

5. The radiation-sensitive composition according to claim 1, wherein the polymer further comprises a structural unit having an acid-dissociable group.

6. The radiation-sensitive composition according to claim 1, wherein the onium salt is at least one selected from the group consisting of: a radiation-sensitive acid generator comprising the organic acid anion and the onium cation; and an acid diffusion controller comprising the organic acid anion and the onium cation and generating an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon exposure to radiation.

7. The radiation-sensitive composition according to claim 6, wherein the onium cation in at least one selected from the group consisting of the radiation-sensitive acid generator and the acid diffusion controller contains an aromatic ring structure having a fluorine atom or an iodine-substituted aromatic ring structure.

8. The radiation-sensitive composition according to claim 1, wherein the onium cation is a sulfonium cation or an iodonium cation.

9. The radiation-sensitive composition according to any one of claims 1 to 8, wherein the high fluorine content polymer has a structure that changes its solubility in an alkaline aqueous solution by the action of an alkali.

10. A method for forming a pattern, comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 8 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

11. The method for forming a pattern according to claim 10, wherein the exposure is carried out with extreme ultraviolet rays or electron beams.

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