Radiation-sensitive composition and pattern formation method

Abstract

Provided are a radiation-sensitive composition capable of exhibiting sufficient levels of sensitivity, CDU performance, and development defect suppression property during pattern formation while achieving a reduction of fluorine in a surface modifier, and a pattern formation method. The radiation-sensitive composition comprises: a first polymer having a structural unit containing an acid-dissociable group; a second polymer different from the first polymer; at least one selected from the group consisting of a radiation-sensitive acid generator containing an iodine group, and an acid diffusion control agent containing an iodine group; and a solvent. The content ratio of the second polymer to the total mass of the first polymer and the second polymer is 0.1-20 mass% inclusive. The second polymer includes a partial structure represented by formula (i), and has a structural unit (B1) not containing a fluorine atom. (In formula (i), R1, R2, and R3 are each independently an alkyl group having 1 to 10 carbon atoms, and * is a bond to a structure other than the partial structure in the structural unit (B1).)

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. As a next-generation technology, efforts are being made to utilize even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet).

[0004] In parallel with the trend toward shorter wavelength radiation, a technique has been proposed in which a hydrophobic resin is added to a resist composition as a surface modifier to improve process efficiency by modifying the surface of the resist film (WO 2020 / 129476).

[0005] International Publication No. 2020 / 129476

[0006] Due to the recent increase in environmental awareness, there is an increasing demand for reducing the fluorine content of surface modifiers, which often contain fluorine atoms. Even in resist compositions in which the fluorine content of surface modifiers is reduced, the same or better resist performance as conventional resists is required in terms of sensitivity, critical dimension uniformity (CDU) performance, which is an index of uniformity of line width and hole diameter, suppression of development defects, etc.

[0007] 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 during pattern formation while reducing the fluorine content of a surface modifier.

[0008] 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.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a first polymer having a structural unit containing an acid-dissociable group; a second polymer different from the first polymer; at least one selected from the group consisting of radiation-sensitive acid generators containing an iodo group and acid diffusion controllers containing an iodo group; and a solvent, wherein the content of the second polymer is 0.1% by mass or more and 20% by mass or less of the total mass of the first polymer and the second polymer, and the second polymer comprises a partial structure represented by the following formula (i) (hereinafter also referred to as "partial structure (i)") and has a structural unit (B1) that does not contain a fluorine atom: (In formula (i), R １ , R ２ and R ３ are each independently an alkyl group having 1 to 10 carbon atoms. * represents a bond to a structure other than the partial structure in the structural unit (B1).

[0010] This radiation-sensitive composition can exhibit excellent sensitivity, CDU performance, and development defect suppression during resist pattern formation. While the reason for this is unclear, it is presumed as follows: The second polymer has a highly hydrophobic partial structure (i) having a tertiary carbon bonded to three alkyl groups. Because this partial structure (i) has a relatively low surface free energy, the second polymer is unevenly distributed on the surface of the resist film and functions as a surface modifier. Furthermore, the structural unit (B1) containing the partial structure (i) does not contain a fluorine atom, which also contributes to reducing fluorine in the radiation-sensitive composition as a whole. Additionally, the fluorine-reducing second polymer increases solubility in a developer and improves development defect suppression. Furthermore, the radiation-sensitive composition contains at least one selected from the group consisting of a radiation-sensitive acid generator containing an iodine group and an acid diffusion controller containing an iodine group. Radiation such as EUV with a wavelength of 13.5 nm is highly absorbed by iodine groups (iodine atoms), which increases the secondary electron generation efficiency and enhances the sensitivity of the resulting resist film. It is presumed that the combined effects of these factors enable the above-mentioned resist performance to be exhibited.

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

[0012] This pattern formation method uses the above-mentioned radiation-sensitive composition, which is capable of exhibiting excellent sensitivity, CDU performance, and suppression of development defects when forming a resist pattern, and therefore can efficiently form a high-quality resist pattern.

[0013] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0014] Radiation-Sensitive Composition The radiation-sensitive composition (hereinafter also simply referred to as "composition") according to this embodiment includes a first polymer (hereinafter also referred to as "base polymer"), a second polymer, and a solvent. The composition further includes at least one selected from the group consisting of a radiation-sensitive acid generator containing an iodo group and an acid diffusion controller containing an iodo group. The composition may include other optional components as long as the effects of the present invention are not impaired.

[0015] When the composition contains a radiation-sensitive acid generator and an acid diffusion controller, the combination may be a combination of a radiation-sensitive acid generator containing an iodine group with an acid diffusion controller not containing an iodine group, a combination of a radiation-sensitive acid generator not containing an iodine group with an acid diffusion controller not containing an iodine group, or a combination of a radiation-sensitive acid generator containing an iodine group with an acid diffusion controller not containing an iodine group. Furthermore, a radiation-sensitive acid generator containing an iodine group and a radiation-sensitive acid generator not containing an iodine group may be used in combination, or an acid diffusion controller containing an iodine group and an acid diffusion controller not containing an iodine group may be used in combination. When the first polymer contains a structural unit (A4) (described below) having a radiation-sensitive acid generating structure, the composition may contain an acid diffusion controller not containing an iodine group but not a radiation-sensitive acid generator. When the first polymer contains a structural unit (A5) (described below) having an acid diffusion controlling structure, the composition may contain a radiation-sensitive acid generator containing an iodine group but not an acid diffusion controller.

[0016] <First Polymer> The first polymer (i.e., base polymer) is an assembly of polymer chains containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (A1)"). In addition to the structural unit (A1), the base polymer may also contain a structural unit (A2) having a phenolic hydroxyl group or a structural unit (A3) containing a lactone structure, etc. Each structural unit will be described below.

[0017] (Structural Unit (A1)) The structural unit (A1) is a structural unit having an acid-dissociable group. The structural unit (A1) is not particularly limited as long as it has an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. In the base polymer, it is preferable that the acid-dissociable group contains the above-mentioned iodine group-containing aromatic ring structure. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (A1-1)") is preferred.

[0018]

[0019] In the above formula (3), R １７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ L each independently represents a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO- or ＊ -L １１ａ represents COO-. １１ａ is a substituted or unsubstituted arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.

[0020] The above R １７ From the viewpoint of copolymerizability of the monomer that gives the structural unit (A1-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0021] 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 arenediyl group represented by the formula:

[0022] L １１ａ Examples of the substituent that the arenediyl group represented by the formula (I) may have include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an alkoxy group, and a hydroxy group.

[0023] L １１ａ Examples of the alkyl group as a substituent include linear or branched alkyl groups having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, and a propyl group. Examples of the fluorinated alkyl group include linear or branched fluorinated alkyl groups having 1 to 8 carbon atoms, such as a trifluoromethyl group and a pentafluoroethyl group. Examples of the alkoxy group include alkoxy groups having 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group, and a butoxy group. Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 10 carbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group, and a butoxycarbonyl group. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as a methoxycarbonyloxy group, a butoxycarbonyloxy group, and an adamantylmethyloxycarbonyloxy group. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as an acetyl group, a propionyl group, a benzoyl group, and an acryloyl group. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as an acetyloxy group, a propionyloxy group, a benzoyloxy group, and an acryloyloxy group. 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.

[0024] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0025] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, and isopentyl; alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

[0026] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; polycyclic alicyclic saturated hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group; monocyclic alicyclic unsaturated hydrocarbon groups such as a cyclopentenyl group and a cyclohexenyl group; and polycyclic alicyclic unsaturated hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group.

[0027] 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.

[0028] The above R １８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms is preferred.

[0029] R １９ and R ２０ The monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula １８ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms in the above formula, groups having 1 to 10 carbon atoms are exemplified.

[0030] R １９ and R ２０ The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula １８ Examples of the monovalent alicyclic hydrocarbon group include those having 3 to 20 carbon atoms.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Examples of the structural unit (A1-1) include structural units represented by the following formulas (3-1) to (3-10) (hereinafter also referred to as "structural units (A1-1-1) to (A1-1-10)").

[0036]

[0037] In the above formulas (3-1) to (3-10), 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, a hydroxy group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. i and j are each independently an integer of 1 to 4. k and l are each 0 or 1. 3a are each independently an integer of 0 to 3. When 3a is 2 or more, multiple R Ｌ１１ are the same or different from each other.

[0038] i and j are preferably 1 or 2. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, an ethenyl group, a phenyl group, or an iodophenyl group. １９ and R ２０ R is preferably a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ is preferably an iodine atom, an alkyl group, or an alkoxy group. Ｌ１１ By employing an iodine atom as the aryl group, an iodine group can be suitably introduced into the structural unit (A1).

[0039] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (A1).

[0040]

[0041] 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.

[0042] 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.

[0043] When the polymer contains the structural unit (A1), the lower limit of the content of the structural unit (A1) (total content when multiple types of structural unit (A1) are present) relative to all structural units constituting the base polymer is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%. The upper limit of this content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By ensuring that the content of the structural unit (A1) falls within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0044] (Structural Unit (A2)) The structural unit (A2) is a structural unit having a phenolic hydroxyl group (excluding the case where it corresponds to the structural unit (I)). When the polymer contains the structural unit (A2), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (A2) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (A2) is suitably applied to pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (A2) is preferably represented by the following formula (2):

[0045] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. R １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group. １０２ If there are multiple R１０２ 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 ４ is an integer from 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0046] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (A2), the substituent is preferably a hydrogen atom or a methyl group.

[0047] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0048] R １０２ The halogen atom, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the above formula (3) is １１ａ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0049] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0050] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0051] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0052] The structural unit (A2) is preferably a structural unit represented by the following formulas (2-1) to (2-20) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-20)").

[0053]

[0054]

[0055] In the above formulas (2-1) to (2-20), R βis the same as the above formula (2).

[0056] The lower limit of the content of the structural unit (A2) (the total content when multiple types of structural unit (A2) are present) is preferably 10 mol %, more preferably 15 mol %, and even more preferably 20 mol %, based on all structural units constituting the polymer. The upper limit of this content is preferably 70 mol %, more preferably 60 mol %, and even more preferably 55 mol %. By setting the content of the structural unit (A2) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity, CDU performance, and LWR performance.

[0057] When a monomer having a phenolic hydroxyl group, such as hydroxystyrene, is polymerized, it is preferable to polymerize the monomer in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then to obtain the structural unit (A2) by deprotecting the phenolic hydroxyl group through hydrolysis. The hydroxystyrene may also be polymerized without protecting the phenolic hydroxyl group.

[0058] (Structural Unit (A3)) The structural unit (A3) 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 (A3), 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.

[0059] Examples of the structural unit (A3) include structural units represented by the following formulae (T-1) to (T-10).

[0060]

[0061] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５are 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.

[0062] 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 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.

[0063] The above L ２ Examples of the divalent linking group represented by the formula (I) include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one group selected from the group consisting of -CO-, -O-, -NH-, and -S-.

[0064] Of these, the structural unit (A3) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a γ-butyrolactone structure or a norbornane lactone structure, and even more preferably a structural unit derived from γ-butyrolactone-yl (meth)acrylate or norbornane lactone-yl (meth)acrylate.

[0065] The lower limit of the content of the structural unit (A3) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on all structural units constituting the base polymer. The upper limit of the content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol% or less. By setting the content of the structural unit (A3) 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.

[0066] (Structural Unit (A4)) The structural unit (A4) has a first organic acid anion and a first onium cation, which form an onium salt structure (1). The onium salt structure (1) functions as a radiation-sensitive acid-generating structure and generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer and generating a carboxyl group or the like.

[0067] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0068] The form in which the first organic acid anion and the first onium cation are contained in the structural unit (A4) of the base polymer is not particularly limited. The base polymer may have the first organic acid anion as a side chain moiety, or the first onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the first organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the first onium cation is ionically bonded to the first organic acid anion as a counter ion of the first organic acid anion. On the other hand, when the first onium cation is bonded to the main chain of the base polymer as a side chain structure, the first organic acid anion is ionically bonded to the first onium cation as a counter ion of the first onium cation. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer have the first organic acid anion as a side chain moiety.

[0069] The first organic acid anion preferably has, as an acid anion moiety, at least one selected from the group consisting of a sulfonate anion, a carboxylate anion, and a sulfonimide anion. Examples of the acid generated by exposure include sulfonic acid, carboxylic acid, and sulfonimide, corresponding to the acid anion moiety.

[0070] Although the structure of the first organic acid anion other than the acid anion portion is not particularly limited, it preferably contains an iodine group in terms of sensitivity and CDU performance. Although the manner in which the iodine group is contained is not particularly limited, it is preferably contained in the form of an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodine groups. By containing an iodine group, it is possible to increase radiation absorption efficiency and improve secondary electron generation efficiency, thereby improving sensitivity.

[0071] The aromatic ring in the iodo group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity.Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, heteroaromatic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, or combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0072] The number of iodo groups in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 2 or 3.

[0073] The first organic acid anion preferably includes, in addition to or instead of the iodo group-containing aromatic ring structure, -O-, -CO-, a cyclic structure, or a combination thereof. Such combinations also include structures (heterocyclic structures) in which -O- or -CO- is incorporated into the cyclic structure as a ring-forming moiety.

[0074] The cyclic structure may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to form a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the skeleton of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0075] The alicyclic structure may be R １８ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably employed.

[0076] As the aromatic ring structure, the aromatic rings (including aromatic hydrocarbon rings and aromatic heterocycles) shown in the above iodine-containing aromatic ring structure can be suitably employed.

[0077] Examples of the heterocyclic structure include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan and benzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, and triazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0078] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof. Examples of such structures include structures represented by the following formulas (H-1) to (H-11).

[0079]

[0080] In the above formula, γ is an integer of 1 to 3.

[0081] The chain structure may be R １８ A structure corresponding to the monovalent chain hydrocarbon group having 1 to 20 carbon atoms in the above formula can be suitably employed.

[0082] 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.

[0083] The substituents that substitute a part or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include L １１ａ Substituents that can be possessed by the arenediyl group represented by the following formula can be suitably employed.

[0084] In the radiation-sensitive acid generating structure, the acid anion moiety is preferably a sulfonate anion, and a fluorine atom or a fluorinated hydrocarbon group is preferably bonded to the carbon atom adjacent to the sulfur atom of the sulfonate anion, thereby allowing the radiation-sensitive acid generating structure to efficiently exhibit the above-mentioned functions.

[0085] The first onium cation is preferably a sulfonium cation or an iodonium cation, and more preferably a sulfonium cation.

[0086] The first onium cation in the structural unit (A4) is preferably a fluorine-containing onium cation containing a fluorine atom. The fluorine-containing onium cation preferably has a fluorine-substituted aromatic ring structure. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0087] The first onium cation may have an iodo group. The first onium cation may contain the iodo group-containing aromatic ring structure.

[0088] The structural unit (A4) having the above structures in combination can efficiently exhibit the above functions.

[0089] The structural unit (A4) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (A4-1)") or a structural unit represented by the following formula (a2) (hereinafter also referred to as "structural unit (A4-2)").

[0090]

[0091] In the formula, R Ｖ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, and some of the methylene groups constituting the alkylene group, cycloalkylene group, or arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ represents a single bond, an ether group, an ester group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and some of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３ Some or all of the hydrogen atoms in Rf may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. ４３ ~R ４７ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom, and R ４３ and R ４４ and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. ４３ ~R ４５ and R ４６ ~R４７ Preferably, at least one of the groups contains a fluorine-substituted aromatic ring structure.

[0092] V ２ and V ３ , R ４３ ~R ４７ The monovalent hydrocarbon group having 1 to 20 carbon atoms in the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group, or a sulfonium salt-containing group, an alkoxy group, or an alkoxycarbonyl group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group, or a sulfonate ester group.

[0093] The structural units (A4-1) and (A4-2) are preferably represented by the following formulas (a1-1) and (a2-1), respectively.

[0094]

[0095] In the formula, R Ｖ , R ４３ ~R ４７ , Rf １ ~Rf ４ and V １ has the same meaning as in formula (a1) or (a2). ４８ is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 0 to 4. n is an integer of 0 to 3.

[0096] Examples of the first organic acid anion of the monomer that gives the structural unit (A4) (including the structural unit (A4-1) and the structural unit (A4-2)) include, but are not limited to, those shown below. Of the first organic acid anions shown below, all of the first organic acid anions that contain an aromatic ring structure have an iodine-substituted aromatic ring structure, but the structural unit (A4) does not necessarily require an iodine-substituted aromatic ring structure. As the first organic acid anion that does not have an iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with a hydrogen atom or another substituent can be preferably used. In the following formula, R Ｖ is synonymous with the above.

[0097]

[0098]

[0099]

[0100]

[0101]

[0102] In the above formula, R Ｖ has the same meaning as the above formula (a1).

[0103] The first onium cation of the structural unit (A4-1) is preferably represented by the following formula (Q-1).

[0104]

[0105] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or greater, multiple Ra2s may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or greater, multiple Ra3s may be the same or different. Ra3 represents a substituent. Ra1 and Ra2 may be bonded to each other to form a ring. When n1 is 2 or greater, multiple Ra1s may be bonded to each other to form a ring. When n2 is 2 or greater, multiple Ra2s may be bonded to each other to form a ring.

[0106] The substituents represented by Ra1, Ra2 and Ra3 are preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom or a halogenated hydrocarbon group.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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 ２ It 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.

[0117] Ra3 is preferably a fluorine atom, an iodine 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 ２CF 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 F ９ More preferred examples include CF ３ can be particularly preferably mentioned.

[0118] Ra3 is a fluorine atom, an iodine atom, or CF ３ is preferred, and a fluorine atom or an iodine atom is more preferred.

[0119] n1 and n2 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0120] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0121] (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 ３When (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 CF ３ 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:

[0122] Specific examples of such onium cations represented by the above formula (Q-1) include the following: The fluorine atom or iodine atom in the onium cations below may be substituted with a hydrogen atom or another substituent.

[0123]

[0124]

[0125]

[0126]

[0127]

[0128] When the onium cation of the structural unit (A4-2) contains a fluorine-substituted aromatic ring structure, the onium cation is preferably a diaryliodonium cation having one or more fluorine atoms.

[0129] When the base polymer contains the structural unit (A4), the lower limit of the content of the structural unit (A4) (the total content when multiple types are contained) is preferably 1 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on all structural units constituting the radiation-sensitive acid-generating polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By keeping the content of the structural unit (A4) within the above range, the function of the acid-generating structure can be fully exhibited.

[0130] The monomers that give the structural units (A4-1) and (A4-2) can be synthesized, for example, by a method similar to that for the sulfonium salts having polymerizable anions described in Japanese Patent No. 5201363.

[0131] (Structural Unit (A5)) The structural unit (A5) has a second organic acid anion and a second onium cation, which form an onium salt structure (2). The onium salt structure (2) functions as an acid diffusion control structure, and under pattern formation conditions using the radiation-sensitive composition, it does not substantially dissociate the acid-dissociable group in the base polymer, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generating structure or the radiation-sensitive acid generator in unexposed areas through salt exchange. The acid generated from the acid diffusion control structure can be said to be a relatively weaker acid (having a higher pKa) than the acid generated from the radiation-sensitive acid generating structure. Whether the onium salt structure functions as a radiation-sensitive acid generating structure or an acid diffusion control structure depends on the energy required to dissociate the acid-dissociable group in the base polymer and the acidity of the onium salt structure or the acid generated.

[0132] The form in which the second organic acid anion and the second onium cation are contained in the structural unit (A5) of the base polymer is not particularly limited. The base polymer may have the second organic acid anion as a side chain moiety or the second onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the second organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the second onium cation is ionically bonded to the second organic acid anion as a counter ion of the second organic acid anion. On the other hand, when the second onium cation is bonded to the main chain of the base polymer as a side chain structure, the second organic acid anion is ionically bonded to the second onium cation as a counter ion of the second onium cation. From the viewpoint of ease of polymerization, it is preferable that the base polymer have the second organic acid anion as a side chain moiety.

[0133] The second organic acid anion preferably has a carboxylic acid anion as an acid anion moiety, and the acid generated by exposure is a carboxylic acid corresponding to the acid anion moiety.

[0134] The structural unit (A5) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (A5-1)").

[0135]

[0136] In formula (p1), R A is a hydrogen atom or a methyl group.

[0137] In formula (p1), X 1 is a single bond, an ester bond, an ether bond, a phenylene group, or a naphthylene group.

[0138] In formula (p1), X ２ X is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the methylene group constituting the saturated hydrocarbylene group may be replaced by an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２The hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a butane-2,2-diyl group, a butane-2,3-diyl group, a 2-methylpropane-1,3 alkanediyl groups having 1 to 12 carbon atoms, such as 1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, and decane-1,10-diyl; cyclic saturated hydrocarbylene groups having 3 to 12 carbon atoms, such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl; and groups obtained by combining these.

[0139] In formula (p1), X 3 is a single bond, an ester bond or an ether bond.

[0140] In formula (p1), R Ｘ is a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms.

[0141] In formula (p1), R ４３ ~R ４５ has the same meaning as the above formula (a1).

[0142] In formula (p1), x1 is an integer of 0 to 3. When x1 is 2 or more, a plurality of R Ｘ are the same or different.

[0143] Examples of the second organic acid anion of the monomer that gives the structural unit (A5) include, but are not limited to, those shown below. Note that, although all of the second organic acid anions shown below have a hydroxy group, the structural unit (A5) does not necessarily require a hydroxy group. As the second organic acid anion that does not have a hydroxy group, a structure in which the hydroxy group in the following formula is substituted with a hydrogen atom or other substituent can be suitably used. In the following formula, R Ａ is the same as above.

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151] As the second onium cation of the structural unit (A5), a sulfonium cation represented by the above formula (Q-1) can be preferably used.

[0152] When the base polymer contains the structural unit (A5), the lower limit of the content of the structural unit (A5) (the total content when multiple types are contained) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, based on all structural units constituting the radiation-sensitive acid-generating polymer. The upper limit of the content is preferably 20 mol%, more preferably 15 mol%, and even more preferably 10 mol%. By keeping the content of the structural unit (A5) within the above range, the function as an acid diffusion-controlling structure can be fully exhibited.

[0153] (Structural Unit (A6)) The base polymer optionally has other structural units. Examples of the other structural units include the structural unit (A6) containing a polar group (excluding those corresponding to the structural unit (A3)). By further including the structural unit (A6), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0154] Examples of the structural unit (A6) include structural units represented by the following formulas.

[0155]

[0156] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0157] When the base polymer has the structural unit (A6) having the polar group, the lower limit of the content of the structural unit (A6) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of the structural unit (A6) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0158] (Method of Synthesizing Base Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0159] 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 Mw is preferably 20,000, more preferably 12,000, even more preferably 10,000, and particularly preferably 8,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0160] 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.

[0161] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0162] The lower limit of the content of the base polymer is preferably 40% by mass, more preferably 50% by mass, and even more preferably 55% by mass, based on the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 99% by mass, more preferably 95% by mass, and even more preferably 90% by mass.

[0163] <Second Polymer> The second polymer is a polymer different from the first polymer and has the structural unit (B1). However, the second polymer does not contain the structural unit (A2) having a phenolic hydroxyl group, or the content of the structural unit (A2) in the second polymer is lower than the content of the structural unit (A2) in the first polymer. The radiation-sensitive composition may contain one or more types of second polymers.

[0164] (Structural Unit (B1)) The structural unit (B1) contains a partial structure represented by the following formula (i) and does not contain a fluorine atom. (In formula (i), R １ , R ２ and R ３are each independently an alkyl group having 1 to 10 carbon atoms. * represents a bond to a structure other than the partial structure in the structural unit (B1).

[0165] R １ , R ２ and R ３ The alkyl group having 1 to 10 carbon atoms represented by the formula (3) is １８ Among the linear or branched alkyl groups shown as the monovalent chain hydrocarbon group having 1 to 20 carbon atoms in the above formula, groups corresponding to those having 1 to 10 carbon atoms can be suitably used.

[0166] R １ , R ２ and R ３ are each independently preferably an alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group.

[0167] The structural unit (B1) is preferably represented by the following formula (1-1) or (1-2). (In formulas (1-1) and (1-2), R Ｍ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｂ１ , L Ｂ３ and L Ｂ４ are each independently a single bond or a divalent linking group. Ｂ２ is a single bond or a divalent linking group in which the carbon atom adjacent to the oxygen atom is a tertiary carbon atom. Ｎ is an acid-dissociable group. １ , R ２ and R ３ has the same meaning as in formula (i) above.

[0168] L Ｂ１ , L Ｂ３ and L Ｂ４ Examples of the divalent linking group represented by the formula (I) include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 3 to 12 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 10 carbon atoms, and a group composed of one or more of these hydrocarbon groups and at least one group selected from the group consisting of -CO-, -O-, -NH-, and -S-.

[0169] The divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms includes R １８ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms in the above formula, groups in which one hydrogen atom has been removed from a group corresponding to 1 to 10 carbon atoms can be suitably used.

[0170] The divalent alicyclic hydrocarbon group having 3 to 12 carbon atoms includes R １８ Among the monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms in the above formula, groups in which one hydrogen atom has been removed from a group corresponding to a carbon number of 3 to 12 can be suitably used.

[0171] The divalent aromatic hydrocarbon group having 6 to 10 carbon atoms includes R １８ Among the monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms in the above formula, groups in which one hydrogen atom has been removed from a group corresponding to 6 to 10 carbon atoms can be suitably used.

[0172] L Ｂ１ is preferably a single bond or an arenediyl group, more preferably a single bond.

[0173] L Ｂ３ As the alkyl group, an alkanediyl group or a combination of an alkanediyl group and —O— is preferred, and a combination of a methylene group and —O— is more preferred.

[0174] L Ｂ２ The divalent linking group represented by the formula (I) in which the carbon atom adjacent to the oxygen atom is a tertiary carbon atom is preferably represented by the following formula (α):

[0175]

[0176] In the above formula (α), R ５０ and R ５１ L each independently represents a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a divalent alicyclic group having 3 to 10 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. ｂ２ is a single bond or a divalent linking group. * is a bond on the oxygen atom side. ** is a bond on the carbon atom side.

[0177] R５０ and R ５１ The monovalent hydrocarbon group having 1 to 10 carbon atoms represented by the formula (3) is R １８ Among monovalent hydrocarbon groups having 1 to 20 carbon atoms, those having 1 to 10 carbon atoms, represented by the following formula, can be suitably used.

[0178] R ５０ and R ５１ As a divalent alicyclic group having 3 to 10 carbon atoms formed by combining these together with the carbon atoms to which they are bonded, R １９ and R ２０ Among the 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 3 to 10 carbon atoms can be suitably used.

[0179] R ５０ and R ５１ is preferably the above-mentioned divalent alicyclic group having 3 to 10 carbon atoms or a monovalent linear hydrocarbon group having 1 to 10 carbon atoms, more preferably a divalent alicyclic group having 3 to 6 carbon atoms or a monovalent linear hydrocarbon group having 1 to 5 carbon atoms, and still more preferably a cyclopentanediyl group or a cyclohexanediyl group, or a methyl group or an ethyl group.

[0180] L ｂ２ The divalent linking group represented by the formula Ｂ１ , L Ｂ３ and L Ｂ４ A divalent linking group represented by the following formula can be preferably used.

[0181] L ｂ２ The divalent linking group represented by the formula (I) is preferably a divalent aromatic hydrocarbon group having 6 to 10 carbon atoms, more preferably a benzenediyl group.

[0182] R ５０ and R ５１ When L ｂ２ is preferably a single bond.

[0183] R Ｎ The acid-dissociable group represented by the formula (3) is R １８ , R １９ and R２０ and monovalent groups composed of carbon atoms to which these are bonded can be suitably employed.

[0184] Examples of the monomer that provides the structural unit (B1) include compounds represented by the following formulae (1-1-1) to (1-1-8) and (1-2-1) to (1-2-6).

[0185]

[0186] In the formula, R Ｍ has the same meaning as the above formula (1-1).

[0187] The lower limit of the content of the structural unit (B1) relative to all structural units constituting the second polymer is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol%. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of the structural unit (B1) within the above range, the surface modification effect of the second polymer on the resist film can be further improved, and excellent CDU performance and suppression of development defects can be achieved.

[0188] (Structural Unit (B2)) The second polymer may have a structural unit (B2) containing at least one selected from the group consisting of a lactone structure and a cyclic carbonate structure. When the second polymer has the structural unit (B2), it can exhibit excellent CDU performance and development defect suppression properties.

[0189] Examples of the structural unit (B2) include structural units containing a lactone structure and structural units containing a cyclic carbonate structure, which are structural units (A3) that the first polymer may have. Specifically, structural units represented by the above formulae (T-1) to (T-7) and (T-10) are preferred.

[0190] When the second polymer has the structural unit (B2), the lower limit of the content of the structural unit (B2) (total content when multiple types of structural unit (B2) are present) relative to all structural units constituting the second polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of this content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 45 mol%. By setting the content of the structural unit (B2) within the above range, it is possible to sufficiently suppress development defects while maintaining high sensitivity and good CDU performance.

[0191] (Structural Unit (B3)) The second polymer may have a structural unit (B3) containing an ammonium cation structure or a phosphonium cation structure and an acid anion. The structural unit (B3) does not have radiation sensitivity. The structural unit (B3) preferably has an intramolecular salt structure (a structure in which an anion moiety and a cation moiety are bonded by a covalent bond), and is more preferably represented by the following formula (B3). The second polymer may contain only one type of structural unit (B3), or may contain two or more types.

[0192] (In formula (B3), R ３１ , R ３２ and R ３３ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an alkyl group having 1 to 6 carbon atoms, or a halogenated alkyl group having 1 to 6 carbon atoms. ３１ represents a single bond, —O—, —CO—, —COO—, —NH—, —CONH—, or * １ -Ar ３１ -A ３３ -. Ar ３１ is a divalent aromatic ring group. ３３ is a single bond, —O—, —CO—, —COO—, —NH— or —CONH—. １ " is R ３３ represents the bond to the carbon atom to which it is bonded. ３１ is a single bond or E in formula (B3) ＋ is a divalent organic group having one or more carbon atoms and bonded to ＋ is a divalent group having an ammonium cation structure or a phosphonium cation structure.３２ is E in formula (B3) ＋ and D － is a divalent organic group having one or more carbon atoms, which is bonded to each of the above via the same or different carbon atoms. － is a monovalent group having an anionic structure.

[0193] In the above formula (B3), R ３１ and R ３２ A hydrogen atom is particularly preferred as R ３３ is preferably a hydrogen atom or a methyl group.

[0194] A ３１ but* １ -Ar ３１ -A ３３ -, Ar ３１ Examples of the divalent aromatic ring group represented by the formula (I) include a substituted or unsubstituted phenylene group.

[0195] B ３１ is E in the above formula (B3). ＋ and B is a divalent organic group having one or more carbon atoms bonded to ３２ With regard to the divalent organic group represented by the formula (I), examples of the divalent organic group include substituted or unsubstituted divalent hydrocarbon groups having 1 to 20 carbon atoms.

[0196] Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms include divalent chain hydrocarbon groups having 1 to 20 carbon atoms.

[0197] Examples of the divalent chain hydrocarbon group having 1 to 20 carbon atoms include linear or branched divalent saturated hydrocarbon groups having 1 to 20 carbon atoms.

[0198] B ３１ or B ３２ is a substituted hydrocarbon group, B ３１ or B ３２ Examples of the substituent that may be contained in the alkyl group include a halogen atom, a hydroxyl group, a cyano group, a nitro group, a halogenated alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkoxycarbonyl group having 2 to 6 carbon atoms.

[0199] In addition, B ３１ Is E ＋"Bonded at a carbon atom" means E ＋ (More specifically, E ＋ The nitrogen atom or phosphorus atom in ３１ It indicates that the carbon atom in the ３２ Is E ＋ and D － For each of the above, "bonded at a carbon atom" means E ＋ (More specifically, E ＋ The nitrogen atom or phosphorus atom in ３２ directly bonded to a carbon atom in － is B ３２ It indicates that the carbon atom in the ＋ B binds to ３１ Carbon atom in E ＋ B binds to ３２ Carbon atoms in and D － B binds to ３２ The carbon atoms in B may be primary, secondary or tertiary carbon atoms. ３１ or B ３２ It may be adjacent to an oxygen atom or a heteroatom-containing group such as a carbonyl group.

[0200] E ＋ is a divalent group having an ammonium cation structure or a phosphonium cation structure. ＋ Preferred specific examples of the divalent group represented by the formula (e-1), (e-2) or (e-3) below include structures represented by the formula (e-1), (e-2) or (e-3) below. (In formula (e-1), formula (e-2) and formula (e-3), R ３６ and R ３７ are each independently a monovalent hydrocarbon group, or R ３６ and R ３７ and are combined together to form R ３６ and R ３７ represents an aliphatic heterocyclic structure formed together with the nitrogen atom to which R is bonded. ３８ and R ３９ are each independently a monovalent hydrocarbon group, or R ３８ and R ３９ and are combined together to form R ３８ and R ３９represents a ring structure formed together with the phosphorus atom to which it is bonded. "*" represents a bond.)

[0201] In the above formulas (e-1) to (e-3), R ３６ , R ３７ , R ３８ or R ３９ Examples of the monovalent hydrocarbon group represented by the formula (I) include monovalent chain hydrocarbon groups having 1 to 10 carbon atoms.

[0202] As the monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms is preferred.

[0203] R ３６ and R ３７ are aligned with each other and R ３６ and R ３７ Examples of the aliphatic heterocyclic structure formed together with the nitrogen atom to which R is bonded include groups in which a hydrogen atom has been removed from a nitrogen atom constituting a nitrogen-containing aliphatic heterocyclic ring (for example, a piperidine ring). ３８ and R ３９ are aligned with each other and R ３８ and R ３９ Examples of the ring structure formed together with the phosphorus atom to which is bonded include groups formed by removing a hydrogen atom from a phosphorus atom constituting a phosphorus-containing heterocycle (e.g., a phosphinane ring, a phosphole ring, etc.). The nitrogen-containing aliphatic heterocyclic structure and the phosphorus-containing heterocyclic structure may each have a substituent such as an alkyl group in the ring.

[0204] E ＋ The divalent group represented by the formula (e-1) preferably has an ammonium cation structure, and among these, the group represented by the formula (e-1) or (e-2) is preferred.

[0205] D － is a monovalent group having an anionic structure. － A specific example of this is "-COO － ", "-SO ３ － ", "-PO ３ － ", "-POO － " or "-O － " are cited as examples.

[0206] Preferred specific examples of the structural unit (B3) include structural units represented by the following formula (1-1) or formula (1-2). (In formula (B3-1) and formula (B3-2), R ３１ , R ３２ , R ３３ , R ３６ , R ３７ , A ３１ , B ３１ and B ３２ are the same as those in formula (B3) above.

[0207] Specific examples of the structural unit (B3) include structural units represented by the following formulas.

[0208] (In the formula, R Ｂ is a hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an alkyl group having 1 to 6 carbon atoms, or a halogenated alkyl group having 1 to 6 carbon atoms.

[0209] When the second polymer has the structural unit (B3), the lower limit of the content of the structural unit (B3) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, based on all structural units constituting the second polymer. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of the structural unit (B3) within the above range, it is possible to sufficiently suppress development defects while maintaining high sensitivity and good CDU performance.

[0210] (Structural Unit (B4)) The second polymer may have a structural unit containing a fluorine atom, so long as it has the structural unit (B1) described above. That is, the second polymer has a structural unit (B1) that does not contain a fluorine atom and includes a partial structure represented by formula (i), but this does not mean that the second polymer does not contain any fluorine atoms. For example, the second polymer may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter, also referred to as structural unit (B4)). By having the structural unit (B4), the second polymer has improved solubility in an alkaline developer, and the occurrence of development defects can be suppressed.

[0211]

[0212] The structural unit (B4) 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-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0213] When the structural unit (B4) 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 (B4) 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 (B4) having an alkali-soluble group (x), A １ is an oxygen atom and W１ It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0214] When the structural unit (B4) has an alkali-dissociable group (y), R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-* or -SO ２ O-*. ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R Ｆ The binding site of W is shown. １ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ is -COO-*, -OCO-* or -SO ２ If O-*, then W １ or R Ｆ is A １ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １ is an oxygen atom, W １ , R Ｅ is a single bond, and R Ｄ is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ A carbonyl group is bonded to the end of the R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (B4) has (y) an alkali-dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. As the structural unit (B4) having (y) an alkali-dissociable group, A １ is -COO-*, and R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0215] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (B4), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0216] R Ｅ When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and even more preferably a group having a norbornane lactone structure.

[0217] When the second polymer has the structural unit (B4), the lower limit of the content of the structural unit (B4) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on all structural units constituting the second polymer. The upper limit of the content is preferably 20 mol%, more preferably 15 mol%, and even more preferably 12 mol%. By keeping the content of the structural unit (B4) within the above range, the solubility in an alkaline developer can be improved, thereby suppressing the occurrence of development defects.

[0218] (Structural Unit (B5)) The second polymer may have a structural unit (B5) containing a carboxy group. When the second polymer has the structural unit (B5), it can exhibit excellent development defect suppression properties. Examples of monomers that provide the structural unit (B5) include (meth)acrylic acid, (meth)acryloyloxyacetic acid, vinylbenzoic acid, vinylsalicylic acid, vinylphthalic acid, and (meth)acryloyloxybenzoic acid.

[0219] (Other Structural Units) The second polymer may contain, as a structural unit other than the structural units listed above, the structural unit (A1) in the first polymer serving as the base polymer (excluding the structure corresponding to the structural unit (B1)).

[0220] From the viewpoint of reducing the amount of fluorine, the second polymer preferably does not contain fluorine atoms.

[0221] When the second polymer contains the structural unit (A1), the lower limit of the content of the structural unit (A1) is preferably 5 mol %, more preferably 10 mol %, and even more preferably 15 mol %, based on all structural units constituting the second polymer, and the upper limit of the content is preferably 40 mol %, more preferably 30 mol %, and even more preferably 25 mol %.

[0222] The lower limit of the Mw of the second polymer is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of the Mw is preferably 20,000, more preferably 10,000, and even more preferably 9,000.

[0223] The lower limit of Mw / Mn of the second polymer is usually 1, and more preferably 1.1. The upper limit of Mw / Mn is usually 5, and preferably 3, and more preferably 2.

[0224] The lower limit of the content of the second polymer is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 5 parts by mass, relative to 100 parts by mass of the base polymer, and the upper limit of the content is preferably 25 parts by mass, more preferably 20 parts by mass, and even more preferably 15 parts by mass.

[0225] The lower limit of the content of the second polymer relative to the total mass of the first polymer and the second polymer is preferably 0.1 mass%, more preferably 0.5 mass%, and even more preferably 1 mass%, and the upper limit of the content is preferably 20 mass%, more preferably 15 mass%, and even more preferably 10 mass%.

[0226] (Method of Synthesizing Second Polymer) The second polymer can be synthesized by the same method as the method of synthesizing the base polymer described above.

[0227] <Radiation-Sensitive Acid Generator> The radiation-sensitive acid generator contains a third organic acid anion and a third onium cation, forming an onium salt structure. The radiation-sensitive acid generator is a component that generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer and generating a carboxyl group or the like. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low-molecular-weight compound (free from the polymer), and is different from a radiation-sensitive acid-generating structure in which the first organic acid anion or the first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure, such as the structural unit (A4) in the first polymer.

[0228] At least one selected from the group consisting of the third organic acid anion and the third onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0229] The structure of the third organic acid anion in the radiation-sensitive acid generator can suitably be the same as the structure of the first organic acid anion of the structural unit (A4) in the first polymer, except for the portion incorporated into the main chain of the first polymer.

[0230] Examples of the third organic acid anion of the radiation-sensitive acid generator include, but are not limited to, those shown below. Note that, instead of the third organic acid anion having an iodo group-containing aromatic ring structure, a third organic acid anion not having an iodo group-containing aromatic ring structure can suitably employ a structure in which the iodo group in the following formula is substituted with a hydrogen atom or another substituent.

[0231]

[0232]

[0233] The structure of the third onium cation in the radiation-sensitive acid generator can suitably be the same as the structure of the first onium cation in the structural unit (A4) in the first polymer. Of these, an iodonium cation is preferred because it may result in the formation of a resist pattern with a reduced number of development defects.

[0234] The above-mentioned radiation-sensitive acid generator can be synthesized by a known method, 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.

[0235] These radiation-sensitive acid generators may be used alone or in combination of two or more. The lower limit of the content of the radiation-sensitive acid generators (total amount when multiple types are used) is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 15 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 100 parts by mass, more preferably 90 parts by mass, and even more preferably 80 parts by mass. This allows for excellent sensitivity and CDU performance to be exhibited during resist pattern formation.

[0236] <Acid Diffusion Controller> The acid diffusion controller contains a quaternary organic acid anion and a quaternary onium cation, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The acid diffusion controller does not substantially dissociate the acid-dissociable group of the base polymer under pattern formation conditions using the radiation-sensitive composition, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas through salt exchange.

[0237] 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 with even more excellent CDU performance.

[0238] At least one selected from the group consisting of the quaternary organic acid anion and the quaternary onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0239] The structure of the fourth organic acid anion of the acid diffusion controller can suitably be the structure of the second organic acid anion of the structural unit (A5) in the first polymer, except for the portion incorporated into the main chain of the first polymer.

[0240] Examples of the fourth organic acid anion of the acid diffusion controller include, but are not limited to, those shown below. Examples also include compounds containing an iodonium cation and an anion in the same molecule and compounds containing a sulfonium cation and anion in the same molecule. As the organic acid anion without an iodo group-containing aromatic ring structure, a structure in which the iodo group in the following formula is substituted with an atom or group other than the iodo group, such as a hydrogen atom or another substituent, can be suitably used.

[0241]

[0242]

[0243] As the quaternary onium cation in the acid diffusion controller, the tertiary onium cation in the radiation-sensitive acid generator can be suitably used.

[0244] When the quaternary onium cation is an iodonium cation, it is preferably a diaryliodonium cation, and more preferably the diaryliodonium cation has one or more fluoro groups.

[0245] The acid diffusion controller can also be synthesized by known methods, particularly by salt exchange reaction.

[0246] These acid diffusion controllers may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (total content when multiple types are used) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 65 mol% relative to the number of moles of the structural unit (A4) of the first polymer or the number of moles of the radiation-sensitive acid generator. The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 75 mol%. This allows excellent sensitivity and CDU performance to be exhibited during resist pattern formation.

[0247] 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 one selected from the group consisting of the first polymer, the second polymer, the radiation-sensitive acid generator, and the acid diffusion controller, as well as optional additives and the like.

[0248] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0249] 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.

[0250] 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.

[0251] 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.

[0252] 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.

[0253] 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.

[0254] 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.

[0255] Among these, ester-based solvents and ether-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents and polyhydric alcohol partial ether-based solvents are more preferred, and propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0256] <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.

[0257] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer, a radiation-sensitive acid generator, an acid diffusion controller, and a solvent, and, if necessary, other optional components, in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of approximately 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0258] <Pattern Forming Method> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0259] According to the pattern formation method, a high-quality resist pattern can be formed because the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity, CDU performance, and suppression of development defects during pattern formation.

[0260] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed, if necessary, to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 160°C, preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0261] When the subsequent exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having at least one of the structural units (A1) and (A2) as the base polymer in the composition.

[0262] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is irradiated with radiation through a photomask to expose it. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0263] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0264] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0265] 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.

[0266] 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.

[0267] 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).

[0268] The present invention will be specifically explained below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples. Measurement methods for various physical properties are shown below.

[0269] [Mw and Mn] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns manufactured by Tosoh Corporation (two "G2000HXL", one "G3000HXL", and one "G4000HXL") under the following conditions: Eluent: tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40° C. Detector: differential refractometer Standard material: monodisperse polystyrene

[0270] <Synthesis of [A] First Polymer> Polymers (A-1) to (A-11) were synthesized as the [A] First Polymer according to the following method. Compounds represented by the above-mentioned monomers (M-1) to (M-24) (hereinafter also referred to as "monomers (M-1) to (M-24)") were used in the synthesis of the [A] First Polymer. 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 %.

[0271]

[0272]

[0273] [Polymer Synthesis Examples 1 to 11] Synthesis of First Polymers (A-1) to (A-11) Each monomer was combined and copolymerized in tetrahydrofuran (THF) solvent, followed by isolation and drying to obtain First Polymers (A-1) to (A-11) having the compositions shown below. The amount of each structural unit used, Mw, and Mw / Mn of the obtained First Polymers are shown in Table 1.

[0274]

[0275] Polymer Synthesis Example 12: Synthesis of Second Polymer (W-1) Compounds (M-7), (M-11), and (M-20) were dissolved in 2-butanone (100 parts by mass relative to the total amount of monomers) so that the molar ratio was 70 / 10 / 20. Azobisisobutyronitrile was added as an initiator to prepare a monomer solution. Meanwhile, 2-butanone was placed in an empty container, and the container was purged with nitrogen for 30 minutes. The container was heated to 80°C, and the monomer solution was added dropwise with stirring. After the dropwise addition was completed, the container was further heated to 80°C and then cooled to below 30°C. The polymerization solution was transferred to a separatory funnel, and hexane was added to uniformly dilute the polymerization solution. Methanol and water 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. In this manner, a propylene glycol monomethyl ether solution of the second polymer (W-1) was obtained.

[0276] Polymer Synthesis Examples 13 to 24 Synthesis of Second Polymers (W-2) to (W-13) Second polymers were synthesized in the same manner as in Polymer Synthesis Example 12, except that the types and amounts of monomers used were shown in Table 2 below. The amounts of each structural unit used, Mw, and Mw / Mn of the resulting second polymers are shown in Table 2.

[0277]

[0278] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator [B], the acid diffusion controller [C], and the solvent [D] used in the preparation of the radiation-sensitive composition are shown below. In the following examples and comparative examples, unless otherwise specified, "parts by mass" means a value when the mass of the first polymer [A] used is taken as 100 parts by mass, and "mol %" means a value when the number of moles of the structural unit (A4) of the first polymer [A] or the radiation-sensitive acid generator [B] used is taken as 100 mol %.

[0279] [B] Radiation-sensitive Acid Generator As the radiation-sensitive acid generator [B], compounds represented by (B-1) to (B-14) were used.

[0280]

[0281]

[0282] [C] Acid Diffusion Controller As the acid diffusion controller [C], compounds represented by the following formulae (C-1) to (C-7) were used.

[0283]

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

[0285] [Example 1] Preparation of Radiation-Sensitive Composition (R-1) [A] 100 parts by mass of (A-1) as a First Polymer, [W] 5 parts by mass of (W-1) as a Second Polymer, [B] 60 parts by mass of (B-1) as a radiation-sensitive acid generator, [C] 70 mol% of (C-1) as an acid diffusion controller relative to (B-1), [D] 1,300 parts by mass of (D-1) as a solvent, and 5,000 parts by mass of (D-2) were mixed. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0286] [Examples 2 to 44 and Comparative Examples 1 to 4] Preparation of radiation-sensitive compositions (R-2) to (R-41) and (CR-1) to (CR-4) Radiation-sensitive compositions (R-2) to (R-44) and (CR-1) to (CR-4) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 3 below were used.

[0287]

[0288] <Evaluation> The radiation-sensitive compositions prepared above were evaluated for sensitivity, CDU, and number of development defects according to the following methods. The evaluation results are shown in Table 4 below.

[0289] [Sensitivity] A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. Each radiation-sensitive composition shown in Table 3 was applied to this bottom antireflective coating using the spin coater, and baked at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 45 nm. This resist film was exposed to light using an EUV scanner ("NXE3300" from ASML) (NA 0.33, σ 0.9 / 0.6, quadrupole pole illumination, a hole pattern mask with a 50 nm pitch on the wafer and +20% bias). PEB was performed on a hot plate at 100°C for 60 seconds, and development was performed in a 2.38 mass% aqueous solution of tetramethylammonium hydroxide (TMAH) for 30 seconds to form a resist pattern with 25 nm holes and a 50 nm pitch (hereinafter also referred to as a "25 nm contact hole pattern"). The exposure dose for forming the 25 nm contact hole pattern was determined as the optimum exposure dose, and this optimum exposure dose was used for sensitivity (mJ / cm ２ The smaller the sensitivity, the better. The sensitivity was 60 mJ / cm ２ If it is less than 60 mJ / cm, it is rated as "A" (very good). ２ More than 63mJ / cm ２ The following cases are rated as "B" (good) and 63 mJ / cm ２ If the value exceeded this, it was evaluated as "C" (poor).

[0290] [CDU] A 25 nm contact hole pattern was formed in the same manner as above, using the optimal exposure dose determined in the [Sensitivity] section above. The formed resist pattern was observed from above using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), and a total of 800 hole diameters were measured at random points. The dimensional variation (3σ) was determined and this was taken as CDU (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better results. CDU was evaluated as "A" (very good) for values ​​less than 3.3 nm, "B" (good) for values ​​3.3 nm to 3.6 nm, and "C" (poor) for values ​​3.6 nm or greater.

[0291] [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.

[0292]

[0293] The resist patterns formed through the above-described EUV exposure were evaluated, and the radiation-sensitive compositions of the examples had good sensitivity and CDU, and the number of development defects was small.

[0294] The radiation-sensitive composition and the method for forming a resist pattern described above can form a resist pattern that has good sensitivity to exposure light and is excellent in CDU and the number of development defects, and therefore can be suitably used in the processing of semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a first polymer having a structural unit containing an acid dissociable group; a second polymer different from the first polymer; at least one selected from the group consisting of a radiation-sensitive acid generator containing an iodine group and an acid diffusion controller containing an iodine group; and a solvent, wherein the content of the second polymer in the total mass of the first polymer and the second polymer is 0.1 mass % or more and 20 mass % or less, and the second polymer has a partial structure represented by the following formula (i) and has a structural unit (B1) that does not contain a fluorine atom: (In formula (i), R １ , R ２ and R ３ are each independently an alkyl group having 1 to 10 carbon atoms. * is a bond to a structure other than the partial structure in the structural unit (B1).

2. The radiation-sensitive composition according to claim 1, wherein the structural unit (B1) is represented by the following formula (1-1) or (1-2): (In formulas (1-1) and (1-2), R Ｍ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. Ｂ１ , L Ｂ３ and L Ｂ４ Each of L is independently a single bond or a divalent linking group. Ｂ２ R is a single bond or a divalent linking group in which the carbon atom adjacent to the oxygen atom is a tertiary carbon atom. Ｎ is an acid dissociable group. １ , R ２ and R ３ has the same meaning as in formula (i) above.

3. The radiation-sensitive composition according to claim 1, wherein the content of the structural unit (B1) in all structural units constituting the second polymer is 30 mol % or more and 95 mol % or less.

4. The radiation-sensitive composition according to claim 1, wherein the second polymer has a structural unit (B2) containing at least one structure selected from the group consisting of a lactone structure and a cyclic carbonate structure.

5. The radiation-sensitive composition according to claim 1, wherein the second polymer has a structural unit (B3) containing an ammonium cation structure or a phosphonium cation structure and an acid anion.

6. The radiation-sensitive composition according to claim 1, wherein said second polymer does not contain fluorine atoms.

7. The radiation-sensitive composition according to claim 1, wherein the second polymer has a weight average molecular weight, calculated as polystyrene, of 10,000 or less.

8. The radiation-sensitive composition according to claim 1, wherein the content of the second polymer in the total mass of the first polymer and the second polymer is 0.1 mass % or more and 10 mass % or less.

9. The radiation-sensitive composition according to any one of claims 1 to 8, wherein the first polymer has a structural unit containing a phenolic hydroxyl group.

10. The radiation-sensitive composition according to any one of claims 1 to 8, wherein the radiation-sensitive acid generator contains an aromatic ring structure containing an iodine group.

11. The radiation-sensitive composition according to any one of claims 1 to 8, wherein the acid diffusion controller contains an aromatic ring structure containing an iodine group.

12. The radiation-sensitive composition according to any one of claims 1 to 8, which is intended for exposure to extreme ultraviolet light.

13. 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.

14. The pattern forming method according to claim 13, wherein the exposure is carried out with extreme ultraviolet light.

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