Radiation-sensitive composition, pattern formation method, and compound

Abstract

Provided are a radiation-sensitive composition and a pattern formation method that can exhibit, at the time of pattern formation, a sufficient level of sensitivity, LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity. This radiation-sensitive composition includes: a polymer that includes a structural unit (I) represented by formula (1); an onium salt that includes an organic acid anion including a cyclic structure, and an onium cation; and a solvent. (In formula (1), R1 is a hydrogen atom or a C1-20 monovalent organic group, L is a single bond or a divalent linking group, R2 is a C1-5 substituted or unsubstituted monovalent hydrocarbon group, R3 is a C1-10 monovalent organic group, a hydroxy group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group, in cases in which there are a plurality of R3s present, the plurality of R3s may be the same as or different from each other, and n is an integer from 0 to 10.)

Description

Radiation-sensitive composition, pattern forming method and compound

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

[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 alkaline or organic developers between exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The photolithography technology described above is promoting pattern miniaturization by using short-wavelength radiation such as ArF excimer lasers, and further by using liquid immersion lithography, in which exposure is performed with the space between the lens of the exposure device and the resist film filled with a liquid medium. Lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered as a next-generation technology.

[0004] Regarding polymers, which are the main component of resist compositions, polymers into which specific ring structures have been introduced in the side chains have been investigated from the viewpoint of pattern roughness (JP-A No. 2006-65211).

[0005] Japanese Patent Application Laid-Open No. 2006-65211

[0006] In these efforts toward next-generation technologies, in addition to sensitivity, resist performance that is equal to or better than conventional performance is required in terms of LWR (Line Width Roughness) performance, which indicates variations in line width and line width of the resist pattern, pattern rectangularity, which indicates the rectangularity of the cross-sectional shape of the resist pattern, suppression of development defects, critical dimension uniformity (CDU), which is an index of uniformity of line width and hole diameter, and pattern circularity, which indicates the circularity of the hole shape.

[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, LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity during pattern formation.

[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] That is, in one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer including a structural unit (I) represented by the following formula (1); an onium salt including an organic acid anion having a cyclic structure and an onium cation; and a solvent: (In the above formula (1), R １ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. L is a single bond or a divalent linking group. R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxy group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ If there are multiple R ３ are the same or different, and n is an integer from 0 to 10.

[0010] The radiation-sensitive composition contains a polymer having a specific polar polycyclic structure in its side chain and an onium salt having a cyclic structure in its anion, and therefore can exhibit excellent sensitivity, LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity during pattern formation. The reason for this is presumed to be as follows, without being bound by any theory.

[0011] The polar polycyclic structure (i.e., hydroxyadamantane structure) contained in the polymer can enhance the hydrophilicity of the polymer while improving etching resistance. Furthermore, the polymer has acid dissociation properties, which can improve the dissolution contrast in the developer between exposed and unexposed areas. Additionally, the onium salt containing the cyclic structure appropriately controls the diffusion length of the generated acid. It is believed that these synergistic effects enable the desired resist performance to be exhibited. The organic group refers to a group containing at least one carbon atom.

[0012] 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.

[0013] The pattern formation method uses the radiation-sensitive composition that can exhibit excellent sensitivity, LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity during pattern formation, and therefore can efficiently form a high-quality resist pattern.

[0014] In still another embodiment, the present invention relates to a compound represented by the following formula (1-a) (hereinafter also referred to as "compound (1-a)"). (In the above formula (1-a), R １ａ is a monovalent organic group having 1 to 20 carbon atoms. ２ａ is a substituted or unsubstituted monovalent hydrocarbon group having 3 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxy group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ If there are multiple R ３ are the same or different, and n is an integer from 0 to 10.

[0015] In still another embodiment, the present invention relates to a compound represented by the following formula (1-b) (hereinafter also referred to as "compound (1-b)"). (In the above formula (1-b), R １is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ is a divalent linking group. ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxy group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ If there are multiple R ３ are the same or different, and n is an integer from 0 to 10.

[0016] The compounds (1-a) and (1-b) have a polar polycyclic structure (i.e., a hydroxyadamantane structure) and an acid-dissociable group, and therefore have good roughness properties and development defect suppression properties, and are suitable as monomer compounds for constituting a polymer in a radiation-sensitive composition.

[0017] 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.

[0018] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") comprises a polymer containing the structural unit (I), an onium salt, and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired. This allows the resist film of the radiation-sensitive composition to be imparted with high levels of sensitivity, LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity.

[0019] (Polymer) The polymer is an aggregate of polymer chains containing the structural unit (I) represented by the above formula (1) (hereinafter, this polymer will also be referred to as a "base polymer"). In addition to the structural unit (I), the base polymer preferably contains a structural unit (II) (however different from the structural unit (I)) having an acid-dissociable group, which will be described later, and may contain structural units other than the structural units (I) and (II). Each structural unit will be described below.

[0020] [Structural Unit (I)] The structural unit (I) is a structural unit containing a polar polycyclic structure represented by the above formula (1). By having the structural unit (I), the base polymer can adjust its solubility in a developer and can exhibit pattern shape retention by increasing the glass transition temperature of the polymer.

[0021] In the above formula (1), R １ The monovalent organic group having 1 to 20 carbon atoms represented by the formula (I) includes a monovalent hydrocarbon group having 1 to 20 carbon atoms, -CO-, -CS-, -O-, -S-, -SO-, or -SO- between carbon atoms of the hydrocarbon group or at the end of the hydrocarbon group. ２ Examples include -, -NR'-, or a group containing a combination of two or more of these (hereinafter also referred to as "group (α)"), the above hydrocarbon group or a group in which some or all of the hydrogen atoms contained in the above group (α) have been substituted with substituents (hereinafter also referred to as "group (β)"), or a combination thereof. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0022] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and combinations thereof.

[0023] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, and a linear or branched unsaturated hydrocarbon group having 1 to 20 carbon atoms.

[0024] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups are cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Preferred polycyclic cycloalkyl groups are bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Preferred monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Preferred polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl groups.

[0025] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0026] The group (α) is also preferably a group containing a heterocyclic group containing a heteroatom between carbon atoms constituting the ring. Examples of the heterocyclic group include a group in which one hydrogen atom has been removed from an aromatic heterocyclic structure, a group in which one hydrogen atom has been removed from an aliphatic heterocyclic structure, and a group combining these. Examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0027] Examples of the aromatic heterocyclic structure include: oxygen atom-containing aromatic heterocyclic structures such as furan, benzofuran, and dibenzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole; sulfur atom-containing aromatic heterocyclic structures such as thiophene, benzothiophene, and dibenzothiophene; and aromatic heterocyclic structures containing multiple heteroatoms such as thiazole, benzothiazole, thiazine, and oxazine.

[0028] Examples of the aliphatic 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; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0029] Examples of the aliphatic heterocyclic structure include a lactone structure, a cyclic carbonate structure, a sultone structure, and a structure containing a cyclic acetal, such as those represented by the following formulas (H-1) to (H-11).

[0030]

[0031] In the above formula, γ is an integer of 1 to 3.

[0032] Examples of the substituent that substitutes some or all of the hydrogen atoms of the organic group include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; hydroxy groups; carboxy groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, and groups in which the hydrogen atoms of these groups are substituted with halogen atoms; and oxo groups (═O).

[0033] The above R １ From the viewpoint of copolymerizability of the monomer that provides the structural unit (I), the alkyl group is preferably a hydrogen atom or a monovalent organic group having 1 to 5 carbon atoms, more preferably a hydrogen atom or a monovalent hydrocarbon group having 1 to 5 carbon atoms, still more preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

[0034] The divalent linking group represented by L includes divalent hydrocarbon groups such as an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, and an arenediyl group; -CO-, -CS-, -O-, -S-, and -SO ２Examples of such heteroatom-containing groups include divalent heteroatom-containing groups such as -, -NR''-, and groups combining two or more of these groups; groups containing the above divalent heteroatom-containing group between the carbon-carbon bond of the above divalent hydrocarbon group; and groups combining these groups. R'' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms in these groups can be substituted with the above R １ The organic group represented by the formula (I) may be substituted with a substituent that the organic group represented by the formula (I) may have.

[0035] The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, a 2,2-propanediyl group, or a 2,2-butanediyl group.

[0036] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups, and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0037] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0038] Examples of the arenediyl group include a phenylene group, a tolylene group, a naphthylene group, etc. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

[0039] L is a single bond, or ＊ A combination of —COO— and an alkanediyl group is preferred, and a single bond, or ＊ A combination of —COO— and a methanediyl group is more preferred, and a single bond is even more preferred. ＊ is R １ is the bond to the carbon atom to which it is bonded.

[0040] R ２ The monovalent hydrocarbon group having 1 to 5 carbon atoms in R １Among the monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups having 1 to 5 carbon atoms can be suitably used.

[0041] R ２ When R has a substituent, the substituent may be any of the above-mentioned R １ It is possible to suitably employ a substituent that can be possessed by an organic group represented by the following formula: ２ When R has a substituent, ２ The number of carbon atoms in the group includes the number of carbon atoms in the substituent.

[0042] R ２ is preferably a substituted or unsubstituted chain hydrocarbon group having 1 to 4 carbon atoms, more preferably an unsubstituted chain hydrocarbon group having 1 to 4 carbon atoms, and even more preferably an unsubstituted chain hydrocarbon group having 2 to 4 carbon atoms, with an ethyl group, an n-propyl group, an isopropyl group, or a t-butyl group being particularly preferred.

[0043] R ３ The monovalent organic group having 1 to 10 carbon atoms represented by the above R １ Among the monovalent organic groups having 1 to 20 carbon atoms represented by the formula (R), groups having 1 to 10 carbon atoms can be suitably used. ３ If there is a ３ is preferably a hydroxy group.

[0044] n is preferably an integer of 0 to 6, more preferably an integer of 0 to 3, even more preferably an integer of 0 to 2, and particularly preferably 0 or 1.

[0045] Examples of the monomer that provides the structural unit (I) include compounds represented by the following formulae (1-1) to (1-27).

[0046]

[0047]

[0048] In the above formula, R １ is synonymous with the above formula (1).

[0049] The base polymer may contain one type of structural unit (I) or a combination of two or more types.

[0050] The lower limit of the content of the structural unit (I) in all structural units constituting the base polymer (the total content when multiple types are included) is preferably 1 mol%, more preferably 5 mol%, even more preferably 10 mol%, and particularly preferably 15 mol%. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, even more preferably 40 mol%, and particularly preferably 30 mol%. By setting the content of the structural unit (I) within the above range, the dissolution contrast between the exposed and unexposed areas and the pattern shape retention can be further improved.

[0051] [Structural Unit (II)] The structural unit (II) is a structural unit containing an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates by the action of an acid. The radiation-sensitive composition has excellent pattern formability due to the polymer containing the structural unit (II).

[0052] The structural unit (II) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter, also referred to as "structural unit (II-1)") is preferred:

[0053]

[0054] 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 hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ are each independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent 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.

[0055] The above R １７As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (II-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0056] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0057] The above R １８ ~R ２０ The chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (1) is １ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms in the above formula, groups corresponding to 1 to 10 carbon atoms can be suitably used.

[0058] The above R １８ ~R ２０ The alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is １ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably used.

[0059] The above R １８ The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1) is １ A monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in the above formula can be suitably used.

[0060] The above R １８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms is preferred.

[0061] The above R １９ and R ２０The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining chain hydrocarbon groups or alicyclic hydrocarbon groups represented by the formula (I) together with the carbon atoms to which they are bonded, is not particularly limited as long as it is a group formed by removing two hydrogen atoms from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above carbon number. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used, 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. Note that a fused alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group formed in such a way that multiple alicyclic rings share a side (a bond between two adjacent carbon atoms).

[0062] 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.

[0063] Among these, R １８ is an alkyl 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.

[0064] Examples of the structural unit (II-1) include structural units represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (II-1-1) to (II-1-15)").

[0065]

[0066]

[0067] In the above formulas (3-1) to (3-15), R １７ ~R ２０ has the same meaning as in formula (3). Ｌ１１ is a halogen atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. i and j are each independently an integer of 1 to 4. k and l are each 0 or 1. 3a are each independently an integer of 0 to 3. When 3a is 2 or more, multiple R Ｌ１１ are the same or different from each other. a4 is an integer of 1 to 3.

[0068] i and j are preferably 1. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclopentyl 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 By employing an iodine atom as the aryl group, an iodine group can be suitably introduced into the structural unit (II).

[0069] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (II).

[0070]

[0071] 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. h1 is an integer of 1 to 4.

[0072] The above R βｆ is preferably a hydrogen atom, a methyl group or an ethyl group. h1 is preferably 1 or 2.

[0073] The base polymer may contain one type of structural unit (II) or a combination of two or more types.

[0074] The lower limit of the content of the structural unit (II) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 1 mol%, more preferably 10 mol%, even more preferably 20 mol%, and particularly preferably 30 mol%. The upper limit of the content is preferably 80 mol%, more preferably 75 mol%, even more preferably 70 mol%, and particularly preferably 60 mol%. By setting the content of the structural unit (II) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0075] [Structural Unit (III)] The base polymer may contain, as another structural unit, a structural unit (III) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (III), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Furthermore, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0076] Examples of the structural unit (III) include structural units represented by the following formulae (T-1) to (T-11).

[0077]

[0078] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. Ｌ４ and R Ｌ５ may be a divalent alicyclic group having 3 to 8 carbon atoms formed by combining together with the carbon atoms to which they are attached. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0079] The above RＬ４ and R Ｌ５ The divalent alicyclic group having 3 to 8 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded includes R １９ and R ２０ Among divalent alicyclic groups having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, groups having 3 to 8 carbon atoms are exemplified. One or more hydrogen atoms on this alicyclic group may be substituted with a hydroxy group.

[0080] 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 -CO-, -O-, -NH-, and -S-.

[0081] Of these, as the structural unit (III), a structural unit containing a lactone structure is preferable, a structural unit containing a γ-butyrolactone structure or a norbornane lactone structure is more preferable, and a structural unit derived from γ-butyrolactone-yl-(meth)acrylate or norbornane lactone-yl (meth)acrylate is even more preferable.

[0082] The lower limit of the content of the structural unit (III) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, based on all structural units constituting the base polymer. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of the structural unit (III) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0083] [Structural Unit (IV)] The base polymer may contain, as another structural unit, for example, a structural unit (IV) containing a polar group (excluding those corresponding to the structural units (I) and (III)). By further containing the structural unit (IV), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0084] Examples of the structural unit (IV) include structural units represented by the following formula:

[0085]

[0086] In the above formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0087] When the base polymer has the structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 4 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 20 mol%, more preferably 10 mol%, and even more preferably 6 mol%. By setting the content of the structural unit (IV) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0088] [Structural Unit (V)] The base polymer optionally contains a structural unit (V) having a phenolic hydroxyl group as another structural unit. The structural unit (V) contributes to improving etching resistance and improving the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, it is suitable for pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV. In this case, it is preferable that the polymer contains the structural unit (II) in addition to the structural unit (V).

[0089] The structural unit (V) is represented by, for example, the following formulas (4-1) and (4-2).

[0090]

[0091] In the above formulas (4-1) to (4-2), R ４１ are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y is a halogen atom, a trifluoromethyl group, a cyano group, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or an acyl group, acyloxy group, or alkoxycarbonyl group having 2 to 7 carbon atoms. When there are multiple Ys, the multiple Ys may be the same or different. t is an integer of 0 to 4.

[0092] When obtaining the structural unit (V), it is preferable to polymerize the corresponding 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) during polymerization, and then perform hydrolysis to remove the protection to obtain the structural unit (V). The corresponding monomer may also be polymerized without protecting the phenolic hydroxyl group.

[0093] In the case of a polymer for exposure to radiation having a wavelength of 50 nm or less, the lower limit of the content of the structural unit (V) is preferably 10 mol %, more preferably 15 mol %, based on all structural units constituting the polymer, and the upper limit of the content is preferably 50 mol %, more preferably 40 mol %.

[0094] [Other Structural Units] The base polymer may contain a structural unit (VIII) having an alicyclic structure represented by the following formula (6) as a structural unit other than the structural units listed above. (In the above formula (6), R １α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0095] In the above formula (6), R ２α The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (3) is １８ ~R ２０A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms and represented by the following formula can be suitably used.

[0096] When the base polymer contains the structural unit (VIII), the lower limit of the content of the structural unit (VIII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer, and the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0097] (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.

[0098] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used alone or in combination of two or more.

[0099] Examples of the solvent used in the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; ketones such as acetone, 2-butanone (methyl ethyl ketone), 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone; Examples of the solvent include ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes, and 1,4-dioxanes; partial ethers of polyhydric alcohols such as propylene glycol monomethyl ether; alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol; and lactones such as γ-butyrolactone. These solvents used in the polymerization may be used alone or in combination of two or more.

[0100] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0101] 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 30,000, more preferably 20,000, even more preferably 12,000, 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.

[0102] 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.

[0103] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0104] GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh Corporation) Column temperature: 40°C Elution solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection volume: 100 μL Detector: differential refractometer Standard material: monodisperse polystyrene

[0105] The content of the base polymer is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0106] (Other Polymers) The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer. As a result, it is possible to increase the water repellency of the surface of the resist film during immersion exposure, and to modify the surface of the resist film during EUV exposure and control the distribution of composition within the film.

[0107] The high-fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (VI)"), and may also have the structural unit (II) or the structural unit (IV) of the base polymer, as necessary.

[0108]

[0109] In the above formula (5), R １３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, —COO—, or —SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. １４ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0110] The above R １３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0111] Above G Ｌ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a single bond, —COO—, or a combination of —COO— and an alkanediyl group having 1 to 5 carbon atoms is preferred, and —COO— is more preferred.

[0112] The above R １４ Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0113] The above R １４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0114] The above R １４As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group are even more preferable.

[0115] When the high-fluorine content polymer has the structural unit (VI), the lower limit of the content of the structural unit (VI) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of the structural unit (VI) within the above range, the mass content of fluorine atoms in the high-fluorine content polymer can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0116] The high-fluorine content polymer may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VII)) in addition to or instead of the structural unit (VI). By having the structural unit (f-2), the high-fluorine content polymer has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0117]

[0118] The structural unit (VII) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R Ｅ At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ｄｄR 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.

[0119] When the structural unit (VII) has (x) an alkali-soluble group, 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 (VII) has (x) an alkali-soluble group, it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VII) having (x) an alkali-soluble group, A １ is an oxygen atom and W １ It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0120] When the structural unit (VII) has (y) an alkali-dissociable group, 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. １is 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 (VII) 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 (VII) 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.

[0121] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0122] 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.

[0123] When the high-fluorine content polymer has the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 60 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 80 mol%. By setting the content of the structural unit (VII) within the above range, the water repellency of the resist film during immersion exposure, the suppression of development defects, and the surface modification of the resist film during EUV exposure and the control of the distribution of the composition within the film can be further improved.

[0124] [Other Structural Units] The high fluorine content polymer may contain, as structural units other than the structural units listed above, structural units (I), (IV), (VIII), etc. in addition to the structural unit (II) in the base polymer.

[0125] When the high-fluorine content polymer contains the structural unit (II), the lower limit of the content of the structural unit (II) is preferably 2 mol %, more preferably 5 mol %, and even more preferably 8 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 50 mol %, more preferably 40 mol %, and even more preferably 35 mol %.

[0126] When the high-fluorine content polymer contains the structural unit (I) or (IV), the lower limit of the content of the structural unit (I) or (IV) is preferably 1 mol %, more preferably 4 mol %, and even more preferably 8 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 40 mol %, more preferably 30 mol %, and even more preferably 25 mol %.

[0127] When the high-fluorine content polymer contains the structural unit (VIII), the lower limit of the content of the structural unit (VIII) is preferably 10 mol %, more preferably 20 mol %, and even more preferably 25 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 60 mol %, more preferably 50 mol %, and even more preferably 40 mol %.

[0128] The lower limit of Mw of the high fluorine content polymer is preferably 4,000, more preferably 6,000, even more preferably 8,000, and particularly preferably 10,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, even more preferably 18,000, and particularly preferably 16,000.

[0129] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0130] When the radiation-sensitive composition contains a high-fluorine-containing polymer, the content of the high-fluorine-containing polymer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of the base polymer, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 6 parts by mass or less, and particularly preferably 4 parts by mass or less.

[0131] By setting the content of the high-fluorine-containing polymer within the above range, the high-fluorine-containing polymer can be more effectively localized in the surface layer of the resist film, thereby further improving the water repellency of the surface of the resist film during immersion lithography. Furthermore, the surface modification of the resist film and the distribution of the composition within the film during EUV exposure can be highly controlled. The radiation-sensitive composition may contain one or more high-fluorine-containing polymers.

[0132] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0133] (Onium Salt) The onium salt contains an organic acid anion having a cyclic structure and an onium cation, and functions as a component that generates an acid when irradiated with radiation. The cyclic structure is R １ a structure corresponding to a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula (1), １ a structure corresponding to a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in the above formula (1), １Examples of the heterocyclic group include structures corresponding to the above heterocyclic groups in the formula:

[0134] The acid generated by exposure of the onium salt is thought to have two functions in the radiation-sensitive composition, depending on the strength of the acid. The first function is that the acid generated by exposure induces dissociation of acid-dissociable groups in the base polymer (including both acid-dissociable groups in the structural unit (I) and acid-dissociable groups in the structural unit (II)), thereby generating carboxyl groups and the like. An onium salt having this first function is called a radiation-sensitive acid generator. The second function is that under pattern formation conditions using the radiation-sensitive composition, the acid does not substantially induce dissociation of acid-dissociable groups in the base polymer, but captures protons from the acid generated from the radiation-sensitive acid generator in unexposed areas, thereby suppressing diffusion. An onium salt having this second function is called an acid diffusion controller. The acid generated from the acid diffusion controller can be said to be a relatively weaker acid (having a higher pKa) than the acid generated from the radiation-sensitive acid generator. Whether an onium salt functions as a radiation-sensitive acid generator or an acid diffusion controller is determined by the energy required to dissociate the acid-dissociable group of the base polymer and the acidity of the onium salt. The onium salt may be contained in the radiation-sensitive composition in a form in which the onium salt structure exists as a compound by itself (isolated from the polymer), in which the onium salt structure is incorporated as part of the polymer, or in both of these forms. The onium salt is preferably contained in the radiation-sensitive composition in a low-molecular-weight form in which the onium salt structure exists as a compound by itself (isolated from the polymer).

[0135] In this specification, the term "dissociation" of an acid-dissociable group refers to dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0136] When the radiation-sensitive composition contains the radiation-sensitive acid generator, the polarity of the base polymer in the exposed area increases, and the base polymer in the exposed area becomes soluble in the developer in the case of alkaline aqueous solution development, while becoming poorly soluble in the developer in the case of organic solvent development.

[0137] Furthermore, by including the acid diffusion controller in the radiation-sensitive composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern that is even more excellent in LWR performance and CDU performance.

[0138] In the radiation-sensitive acid generator, the organic acid anion preferably has a sulfonate anion, and a fluorine atom, a fluorinated hydrocarbon group, or a cyano group bonded to at least one carbon atom selected from the group consisting of a carbon atom at the α-position and a carbon atom at the β-position relative to the sulfur atom in the sulfonate anion, thereby enabling the radiation-sensitive acid generator to efficiently exhibit the first function.

[0139] In the acid diffusion controller, the organic acid anion preferably has a sulfonate anion or a carboxylate anion (however, when the organic acid anion has the sulfonate anion, a fluorine atom or a fluorinated hydrocarbon group is not bonded to either the carbon atom at the α-position or the carbon atom at the β-position relative to the sulfur atom in the sulfonate anion), which allows the acid diffusion controller to efficiently exhibit the second function.

[0140] Hereinafter, the case where the onium salt is a radiation-sensitive acid generator and the case where the onium salt is an acid diffusion controller will be described separately. The radiation-sensitive composition may contain an onium salt as a radiation-sensitive acid generator, an onium salt as an acid diffusion controller, or both an onium salt as a radiation-sensitive acid generator and an onium salt as an acid diffusion controller.

[0141] (Radiation-Sensitive Acid Generator) The radiation-sensitive acid generator is preferably represented by the following formula (p-1). (In the above formula (p-1), R ｐ１ is a monovalent group containing a cyclic structure having 5 or more ring members. ｐ２ is a divalent linking group. ｐ３ and R ｐ４ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ｐ５ and R ｐ６are each independently a fluorine atom, a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms, or a cyano group. ｐ１ is an integer from 0 to 10. ｐ２ is an integer from 0 to 10. ｐ３ is an integer from 0 to 10. ｐ１ +n ｐ２ +n ｐ３ If is 0, R ｐ１ has an aromatic ring structure as the cyclic structure, and the aromatic ring structure is -SO ３ － Combine with n ｐ１ If there are two or more R ｐ２ are the same or different. ｐ２ If there are two or more R ｐ３ are the same or different, and multiple R ｐ４ are the same or different. ｐ３ If there are two or more R ｐ５ are the same or different, and multiple R ｐ６ are the same or different. ＋ is a monovalent onium cation.

[0142] R ｐ１ Examples of the monovalent group containing a cyclic structure represented by the formula (I) include a monovalent group containing an alicyclic structure having 5 or more ring members, a monovalent group containing an aliphatic heterocyclic structure having 5 or more ring members, a monovalent group containing an aromatic ring structure having 6 or more ring members, a monovalent group containing an aromatic heterocyclic structure having 6 or more ring members, or a combination thereof. The embodiment of the combination of cyclic structures may be any of a fused ring structure, a ring assembly structure (a structure in which two adjacent rings are bonded by a single bond), and a spiro ring structure.

[0143] Examples of the alicyclic structure having 5 or more ring members include: monocyclic cycloalkane structures such as a cyclopentane structure, a cyclohexane structure, a cycloheptane structure, a cyclooctane structure, a cyclononane structure, a cyclodecane structure, and a cyclododecane structure; monocyclic cycloalkene structures such as a cyclopentene structure, a cyclohexene structure, a cycloheptene structure, a cyclooctene structure, and a cyclodecene structure; polycyclic cycloalkane structures such as a norbornane structure, an adamantane structure, a tricyclodecane structure, and a tetracyclododecane structure; and polycyclic cycloalkene structures such as a norbornene structure and a tricyclodecene structure.

[0144] Examples of the aliphatic heterocyclic structure having 5 or more ring members include: lactone structures such as a pentanolactone structure, a hexanolactone structure, and a norbornanelactone structure; sultone structures such as a pentanosultone structure, a hexanosultone structure, and a norbornanesultone structure; oxygen atom-containing heterocyclic structures such as an oxacyclopentane structure, an oxacycloheptane structure, and an oxanorbornane structure; nitrogen atom-containing heterocyclic structures such as an azacyclopentane structure, an azacyclohexane structure, and a diazabicyclooctane structure; sulfur atom-containing heterocyclic structures such as a thiacyclopentane structure, a thiacyclohexane structure, and a thianorbornane structure; １ Examples of the cyclic carbonate structure and the cyclic acetal structure include:

[0145] Examples of the aromatic ring structure having six or more ring members include a benzene structure, a naphthalene structure, a phenanthrene structure, and an anthracene structure.

[0146] Examples of the aromatic heterocyclic structure having 6 or more ring members include oxygen atom-containing heterocyclic structures such as a furan structure, a pyran structure, and a benzopyran structure, and nitrogen atom-containing heterocyclic structures such as a pyridine structure, a pyrimidine structure, and an indole structure.

[0147] R ｐ１The lower limit of the number of ring members of the cyclic structure may be 5, 6, 7, 8, or 9. On the other hand, the upper limit of the number of ring members may be 15, 14, 13, or 12.

[0148] R ｐ１ Some or all of the hydrogen atoms in the cyclic structure may be substituted with a substituent. Examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom, hydroxy group, carboxy group, cyano group, nitro group, alkoxy group, alkoxycarbonyl group, alkoxycarbonyloxy group, acyl group, and acyloxy group. Among these, a hydroxy group is preferred.

[0149] R ｐ１ Among these, preferred are monovalent groups containing an alicyclic structure having 5 or more ring members and monovalent groups containing an aliphatic heterocyclic structure having 5 or more ring members, more preferred are monovalent groups containing an alicyclic structure having 6 or more ring members and monovalent groups containing an aliphatic heterocyclic structure having 6 or more ring members, even more preferred are monovalent groups containing an alicyclic structure having 6 or more ring members and monovalent groups containing an aliphatic heterocyclic structure having 6 or more ring members, and particularly preferred are adamantyl group, hydroxyadamantyl group, norbornane lactone-yl group, norbornane sultone-yl group and 5-oxo-4-oxatricyclo[4.3.1.1 ３，８ ]undecanyl is more preferred, and adamantyl is especially preferred.

[0150] R ｐ２ Suitable examples of the divalent linking group represented by R include the divalent linking group represented by L in the above formula (1). ｐ２ The divalent linking group represented by the formula (I) is preferably —COO—, —OCO—, an alkanediyl group, a cycloalkanediyl group, or a combination thereof.

[0151] R ｐ３ and R ｐ４ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (R) include an alkyl group having 1 to 20 carbon atoms. ｐ３ and R ｐ４Examples of the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a fluorinated alkyl group having 1 to 20 carbon atoms. ｐ３ and R ｐ４ As the alkyl group, a hydrogen atom, a fluorine atom and a fluorinated alkyl group are preferred, a fluorine atom and a perfluoroalkyl group are more preferred, and a fluorine atom and a trifluoromethyl group are even more preferred.

[0152] R ｐ５ and R ｐ６ Examples of the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a fluorinated alkyl group having 1 to 20 carbon atoms. ｐ５ and R ｐ６ As the alkyl group, a fluorine atom and a fluorinated alkyl group are preferred, a fluorine atom and a perfluoroalkyl group are more preferred, a fluorine atom and a trifluoromethyl group are further preferred, and a fluorine atom is particularly preferred.

[0153] n ｐ１ is preferably an integer of 0 to 5, more preferably an integer of 0 to 3, still more preferably an integer of 0 to 2, and particularly preferably 0 or 1.

[0154] n ｐ２ is more preferably an integer of 0 to 2, further preferably 0 or 1, and particularly preferably 0.

[0155] n ｐ３ is preferably an integer of 0 to 5, more preferably an integer of 1 to 4, even more preferably an integer of 1 to 3, and particularly preferably 1 or 2. ｐ３ By making n equal to or greater than 1, the strength of the acid generated from the compound of formula (p-1) can be increased, and as a result, the sensitivity, LWR performance, CDU performance, etc. of the radiation-sensitive resin composition can be further improved. ｐ３ The upper limit of is preferably 4, more preferably 3, and even more preferably 2.

[0156] In the above formula (p-1), n ｐ１ +n ｐ２ +n ｐ３ is an integer between 0 and 30. ｐ１ +n ｐ２ +n ｐ３If is 0, R ｐ１ has an aromatic ring structure as the cyclic structure, and the aromatic ring structure is —SO ３ － The aromatic ring structure preferably contains a fluorine atom. ｐ１ +n ｐ２ +n ｐ３ The lower limit of n is preferably 2, more preferably 4. ｐ１ +n ｐ２ +n ｐ３ The upper limit of is preferably 20, more preferably 10.

[0157] In the formula (p-1), the Z ＋ Examples of the monovalent onium cation represented by the formula (X-1) include onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of the onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, phosphonium cation, diazonium cation, pyridinium cation, and ammonium cation. Among these, sulfonium cation or iodonium cation is preferred. The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0158]

[0159] In the above formula (X-1), R ａ１ , R ａ２ and R ａ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, or —OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ, —O—, —CO—, or a combination thereof, or a ring structure formed by combining two or more of these groups. The ring structure may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton. Ｐ , R Ｑ and R Ｔ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently an integer of 0 to 5. R ａ１ ~R ａ３ and R Ｐ , R Ｑ and R Ｔ If there are multiple R ａ１ ~R ａ３ and R Ｐ , R Ｑ and R Ｔ may be the same or different.

[0160] In the above formula (X-2), R ｂ１ is a substituted or unsubstituted linear or branched alkyl group or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. ｋ is 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ may be the same or different, and multiple R ｂ１ may represent a ring structure formed by combining with each other. ｂ２ is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ is a single bond or a divalent linking group. k5 is an integer of 0 to 4. R ｂ２ If there are multiple R ｂ２may be the same or different, and multiple R ｂ２ may represent a ring structure formed by combining with each other, and q is an integer of 0 to 3. ＋ The ring structure containing the following may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton.

[0161] In the above formula (X-3), R ｃ１ , R ｃ２ and R ｃ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0162] In the above formula (X-4), R ｇ１ is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. ｋ２ is 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ may be the same or different, and multiple R ｇ１ may represent a ring structure formed by combining with each other. ｇ２ and R ｇ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, or a ring structure formed by combining these groups together. k11 and k12 are each independently an integer of 0 to 4. R ｇ２ and R ｇ３ If there are multiple R ｇ２ and R ｇ３ may be the same or different.

[0163] In the above formula (X-5), R ｄ１and R ｄ２ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by combining two or more of these groups. k6 and k7 are each independently an integer of 0 to 5. R ｄ１ and R ｄ２ If there are multiple R ｄ１ and R ｄ２ may be the same or different.

[0164] In the above formula (X-6), R ｅ１ and R ｅ２ are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 are each independently an integer of 0 to 4.

[0165] Specific examples of the onium cation include, but are not limited to, structures of the following formulae (1-2-1) to (1-2-53).

[0166]

[0167]

[0168]

[0169] Examples of the radiation-sensitive acid generator represented by formula (p-1) include radiation-sensitive acid generators represented by formulas (p-1-1) to (p-1-70) below (hereinafter also referred to as "radiation-sensitive acid generator (p-1-1) to radiation-sensitive acid generator (p-1-70)").

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176] In the above formulas (p-1-1) to (p-1-70), Z ＋ is a monovalent onium cation.

[0177] The lower limit of the content of the onium salt as the radiation-sensitive acid generator (the total amount when multiple types of onium salts are included) is preferably 1 part by mass, more preferably 5 parts by mass, and even more preferably 8 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 35 parts by mass. The content of the onium salt as the radiation-sensitive acid generator is appropriately selected depending on the type of polymer used, exposure conditions, desired sensitivity, and the like. This allows the resist pattern to exhibit excellent sensitivity, LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity during resist pattern formation.

[0178] (Method for Synthesizing Radiation-Sensitive Acid Generator) The radiation-sensitive acid generator represented by formula (p-1) can be synthesized by a known method, particularly by a salt exchange reaction. Other known radiation-sensitive acid generators can also be used in combination as long as the effects of the present invention are not impaired.

[0179] (Acid Diffusion Controller) Examples of the acid diffusion controller include onium salts that decompose upon exposure to light and lose their acid diffusion controllability. Examples of such onium salts include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Other examples include compounds in which a sulfonium cation and an organic acid anion are bonded, represented by the following formula (8-3), and compounds in which an iodonium cation and an organic acid anion are bonded, represented by the following formula (8-4).

[0180]

[0181] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation.＋ Examples of the sulfonium cation represented by the formula (X-1) to (X-4) include sulfonium cations represented by the formula (X-1) to (X-4), and U ＋ Examples of the iodonium cation represented by the formula (X-5) to (X-6) include the iodonium cation represented by the formula (X-6). － and Q － are each independently R α -COO － , R α -SO ３ － It is an organic acid anion represented by the formula: R α is a single bond or a monovalent organic group having 1 to 30 carbon atoms. As this organic group, R １ A group in which the number of carbon atoms of a monovalent organic group having 1 to 20 carbon atoms, represented by the following formula (I) is extended to 30, can be suitably used.

[0182] R α is R in the above formula (p-1). ｐ１ It is preferable that the ring structure contains a cyclic structure represented by the formula (1). Examples of the cyclic structure include alicyclic hydrocarbon structures such as a norbornane structure, an adamantane structure, and a cyclic terpene structure, and aromatic hydrocarbon structures such as a benzene structure and a naphthalene structure. Some or all of the hydrogen atoms in the cyclic structure may be substituted with a substituent. Examples of the substituent include R １ Substituents that can be possessed by the organic group represented by the following formula can be suitably employed.

[0183] Examples of the acid diffusion controller include compounds represented by the following formula:

[0184]

[0185]

[0186]

[0187] The lower limit of the content of the onium salt as the acid diffusion controller 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 polymer. The upper limit of the content is preferably 40 parts by mass, more preferably 30 parts by mass, and even more preferably 25 parts by mass. By setting the content of the acid diffusion controller within the above range, the lithography performance of the radiation-sensitive composition can be further improved. The radiation-sensitive composition may contain one or more types of acid diffusion controllers.

[0188] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt compound (1) and the polymer, as well as an optional acid diffusion controller and the like.

[0189] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0190] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 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, such as 3-methoxybutanol and propylene glycol monomethyl ether (1-methoxy-2-propanol). 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.

[0191] 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.

[0192] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, and methyl-isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; 2,4-pentanedione, acetonylacetone, and acetophenone.

[0193] 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.

[0194] 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.

[0195] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0196] Among these, ester-based solvents, ether-based solvents, and alcohol-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, polyhydric alcohol ether-based solvents, lactone-based solvents, and alcohol acid ester-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, γ-butyrolactone, and ethyl lactate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0197] (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.

[0198] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a polymer, an onium salt, and, if necessary, a high-fluorine-content polymer, and a solvent in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.40 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.

[0199] <Pattern Forming Method> A pattern forming method according to one embodiment of the present invention 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 (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film (hereinafter also referred to as a "development step").

[0200] According to the pattern forming method, a high-quality resist pattern can be formed because the radiation-sensitive composition is used, which is capable of forming a resist film that is excellent in sensitivity, LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity in the exposure step. Each step will be described below.

[0201] [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, if necessary, pre-baking (PB) may be performed to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 150°C, and preferably 80°C to 140°C. The PB time is typically 5 to 600 seconds, and preferably 10 to 300 seconds.

[0202] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 20 nm, and even more preferably 30 nm. The upper limit of the thickness is preferably 500 nm, more preferably 400 nm, and even more preferably 300 nm. In particular, when a thick resist film is exposed to ArF excimer laser light in the exposure step described below, the lower limit of the thickness may be 100 nm, 150 nm, or 200 nm.

[0203] When performing immersion exposure, regardless of whether the radiation-sensitive composition contains a water-repellent polymer additive such as a high-fluorine-content polymer, a protective film for immersion exposure that is insoluble in the immersion liquid may be provided on the formed resist film in order to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion exposure may be either a solvent-peelable protective film that is peeled off with a solvent before the development step (see, for example, JP-A 2006-227632), or a developer-peelable protective film that is peeled off simultaneously with development in the development step (see, for example, WO 2005-069076 and WO 2006-035790). However, from the viewpoint of throughput, it is preferable to use a developer-peelable protective film for immersion exposure.

[0204] Furthermore, when the subsequent exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural unit (I), the structural unit (II), the structural unit (IV), the structural unit (V), etc. as the base polymer in the composition.

[0205] [Exposure Step] In this step (step (2) above), the resist film formed in the resist film formation step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion liquid such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0206] When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible so as to minimize distortion of the optical image projected onto the film. However, particularly when the exposure light source is an ArF excimer laser beam (wavelength 193 nm), water is preferred from the above-mentioned viewpoints, as well as from the viewpoints of ease of availability and ease of handling. When water is used, a small proportion of an additive that reduces the surface tension of water and increases its surfactant power may be added. It is preferable that this additive does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0207] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0208] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0209] 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.

[0210] 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, ether solvents, ester solvents, and ketone solvents are preferred. As ether solvents, glycol ether solvents are preferred, with ethylene glycol monomethyl ether and propylene glycol monomethyl ether being more preferred. As ester solvents, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As ketone solvents, 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.

[0211] As mentioned above, the developer may be either an alkaline developer or an organic solvent developer, and can be appropriately selected depending on whether the desired pattern is a positive or negative pattern.

[0212] 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 developing by piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time (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 rotating at a constant speed (dynamic dispense method).

[0213] Compound (1-a) The compound (1-a) is a compound represented by the following formula (1-a): (In the above formula (1-a), R １ａ is a monovalent organic group having 1 to 20 carbon atoms. ２ａ is a substituted or unsubstituted monovalent hydrocarbon group having 3 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxy group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ If there are multiple R ３ are the same or different, and n is an integer from 0 to 10.

[0214] In the above formula (1-a), R １ａ The monovalent organic group having 1 to 20 carbon atoms represented by the formula (1) is R １ The monovalent organic groups having 1 to 20 carbon atoms shown in the following formula can be suitably used.

[0215] R ２ａ The monovalent hydrocarbon group having 3 to 5 carbon atoms in the formula (1) is R ２ Among the monovalent hydrocarbon groups having 1 to 5 carbon atoms in the above formula, groups having 3 to 5 carbon atoms can be suitably used. ２ａ When R has a substituent, the substituent may be any of the above-mentioned R １ Substituents that can be possessed by the organic group represented by the following formula can be suitably employed.

[0216] In the above formula (1-a), R ３ and n have the same meanings as in formula (1) above.

[0217] Specific examples of the compound (1-a) include compounds represented by the above formulas (1-3), (1-4), (1-6), and (1-19) to (1-22).

[0218] Compound (1-b) The compound is represented by the following formula (1-b): (In the above formula (1-b), R １ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ is a divalent linking group. ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxy group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ If there are multiple R ３ are the same or different, and n is an integer from 0 to 10.

[0219] In the above formula (1-b), L ｂ As the divalent linking group represented by the formula (1), the divalent linking group represented by L in the formula (1) can be suitably used.

[0220] In the above formula (1-b), R １ , R ２ , R ３ and n have the same meanings as in formula (1) above.

[0221] Specific examples of the compound (1-b) include compounds represented by the above formulas (1-8) to (1-18) and (1-23) to (1-26).

[0222] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0223] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0224] [ １３ C-NMR analysis of polymer １３C-NMR analysis was carried out using a nuclear magnetic resonance spectrometer (JNM-Delta400 manufactured by JEOL Ltd.).

[0225] <Synthesis of Compounds (Monomers)> Of the compounds used as monomers in the synthesis of each polymer, the compounds represented by the following formulas (M-1) to (M-18) (hereinafter also referred to as "compound (M-1)" or "monomer (M-1)") were synthesized according to the following procedure.

[0226] Synthesis Example m1 (Synthesis of Monomer (M-1)) Compound (M-1) was synthesized according to the following synthesis scheme.

[0227] A reaction vessel was charged with 20.0 mmol of 5-hydroxy-2-adamantanone, 2.0 mmol of pyridinium paratoluenesulfonate, 25.0 mmol of 3,4-dihydro-2H-pyran, and 50 g of dichloromethane, and the mixture was stirred at room temperature for 10 hours. Subsequently, a saturated aqueous solution of sodium bicarbonate was added to the reaction solution to terminate the reaction, and then dichloromethane was added for extraction, and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying over sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain the alcohol-protected compound in good yield.

[0228] To the above-mentioned alcohol-protected product, 30.0 mmol of ethylmagnesium bromide and 50 g of tetrahydrofuran were added, and the mixture was stirred at 60°C for 5 hours. Thereafter, a saturated aqueous solution of ammonium chloride was added to the reaction solution to terminate the reaction, and then ethyl acetate was added for extraction and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying with sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain the compound represented by the above formula (M-1-a) (hereinafter also referred to as "compound (M-1-a)") in good yield.

[0229] To compound (M-1-a), 20.0 mmol of methacryloyl chloride, 20.0 mmol of triethylamine, and 50 g of tetrahydrofuran were added, and the mixture was stirred at 60°C for 5 hours. Then, 100 g of 1 M hydrochloric acid was added to the reaction solution, and the mixture was stirred at room temperature for 2 hours. After that, a saturated aqueous solution of sodium bicarbonate was added to terminate the reaction, and then ethyl acetate was added for extraction and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying with sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography, thereby obtaining the compound represented by formula (M-1) in good yield.

[0230] [Synthesis Examples m2 to m4] (Synthesis of Monomer (M-2), Monomer (M-5), and Monomer (M-7)) Compounds represented by the following formulae (M-2), (M-5), and (M-7) were synthesized in the same manner as in Synthesis Example m1, except that the raw materials and precursors were appropriately changed.

[0231]

[0232] Examples M1 to M3 (Synthesis of Monomer (M-3), Monomer (M-4), and Monomer (M-6)) Compounds represented by the following formulae (M-3), (M-4), and (M-6) were synthesized in the same manner as in Synthesis Example m1, except that the raw materials and precursors were appropriately changed.

[0233]

[0234] Example M4 Synthesis of Monomer (M-8) Compound (M-8) was synthesized according to the following synthesis scheme.

[0235] To a reaction vessel were added 20.0 mmol of compound (M-1-a), 20.0 mmol of bromoacetyl bromide, 20.0 mmol of triethylamine, and 50 g of dichloromethane, followed by stirring at room temperature for 10 hours. Subsequently, a saturated aqueous ammonium chloride solution was added to the reaction solution to terminate the reaction, followed by extraction with dichloromethane and separation of the organic layer. The resulting organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain the compound represented by the above formula (M-1-b) (hereinafter also referred to as "compound (M-1-b)") in good yield.

[0236] To the compound (M-1-b), 30.0 mmol of methacrylic acid, 30.0 mmol of cesium carbonate, and 50 g of dimethylformamide were added, and the mixture was stirred at 60°C for 5 hours. Then, 200 g of 1 M hydrochloric acid was added to the reaction solution, and the mixture was stirred at room temperature for 3 hours. After that, a saturated aqueous solution of sodium bicarbonate was added to terminate the reaction, and then ethyl acetate was added for extraction and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying with sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography, yielding the compound represented by the above formula (M-8) in good yield.

[0237] [Examples M5 to M7] (Synthesis of Monomer (M-9) to Monomer (M-11)) Compounds represented by the following formulas (M-9) to (M-11) were synthesized in the same manner as in Example M4, except that the raw materials and precursors were appropriately changed.

[0238]

[0239] Example M8 Synthesis of Monomer (M-12) Compound (M-12) was synthesized according to the following synthesis scheme.

[0240] To a reaction vessel, 20.0 mmol of the compound (M-1-b), 25.0 mmol of zinc powder, 2.00 mmol of chlorotrimethylsilane, and 50 g of tetrahydrofuran were added and stirred at room temperature for 1 hour. Subsequently, 30.0 mmol of methyl ethyl ketone was added to the reaction solution, and the mixture was further stirred at room temperature for 8 hours. Subsequently, a saturated aqueous solution of ammonium chloride was added to the reaction solution to terminate the reaction, followed by extraction with ethyl acetate and separation of the organic layer. The resulting organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying over sodium sulfate, the solvent was distilled off, and the resulting mixture was purified by column chromatography to obtain an alcohol form in good yield.

[0241] To the alcohol compound, 20.0 mmol of methacryloyl chloride, 20.0 mmol of triethylamine, and 50 g of tetrahydrofuran were added, and the mixture was stirred at 60°C for 5 hours. Then, 100 g of 1 M hydrochloric acid was added to the reaction solution, and the mixture was stirred at room temperature for 1 hour. After that, a saturated aqueous solution of sodium bicarbonate was added to terminate the reaction, and then ethyl acetate was added for extraction and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying with sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography, thereby obtaining the compound represented by the above formula (M-12) in good yield.

[0242] [Examples M9 to M10] (Synthesis of Monomer (M-13) to Monomer (M-14)) Compounds represented by the following formulas (M-13) to (M-14) were synthesized in the same manner as in Example M8, except that the raw materials and precursors were appropriately changed.

[0243]

[0244] Example M11 Synthesis of Monomer (M-15) Compound (M-15) was synthesized according to the following synthesis scheme.

[0245] 20.0 mmol of 3-hydroxy-1-adamantanecarboxylic acid, 20.0 mmol of methacryloyl chloride, 25.0 mmol of pyridine, and 50 g of acetonitrile were added to a reaction vessel and stirred at room temperature for 6 hours. Subsequently, saturated aqueous ammonium chloride solution was added to the reaction solution to terminate the reaction, and then ethyl acetate was added for extraction and the organic layer was separated. The resulting organic layer was washed with saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off, and the carboxylic acid was obtained in good yield by purifying by column chromatography.

[0246] To the carboxylic acid compound, 20.0 mmol of oxalyl chloride and 50 g of acetonitrile were added and stirred at 40°C for 1 hour. Then, 20.0 mmol of the compound (M-1-a), 20.0 mmol of triethylamine, and 2.0 mmol of 4-dimethylaminopyridine were added to the reaction solution, and the mixture was stirred at 80°C for 7 hours. Then, 200 g of 1 M hydrochloric acid was added to the reaction solution, and the mixture was stirred at room temperature for 3 hours. After that, a saturated aqueous solution of sodium bicarbonate was added to terminate the reaction, and then ethyl acetate was added for extraction and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying over sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain the compound represented by formula (M-15) in good yield.

[0247] [Examples M12 to M14] (Synthesis of Monomer (M-16) to Monomer (M-18)) Compounds represented by the following formulas (M-16) to (M-18) were synthesized in the same manner as in Example M11, except that the raw materials and precursors were appropriately changed.

[0248]

[0249] Among the monomers used in the synthesis of each polymer, monomers other than monomer (M-1) to monomer (M-18) are shown below. Hereinafter, the compounds represented by formulas (m-1) to (m-23) may be referred to as "compound (m-1)" to "compound (m-23)" or "monomer (m-1)" to "monomer (m-23)," respectively.

[0250]

[0251] <Synthesis of Polymers> In the following synthesis examples, unless otherwise specified, "parts by mass" means a value when the total mass of the monomers used in the synthesis of each polymer is taken as 100 parts by mass, and "mol %" means a value when the total number of moles of the monomers used in the synthesis of each polymer is taken as 100 mol %.

[0252] Synthesis Example 1 Synthesis of Polymer (A-1) Monomer (M-1), monomer (m-1), and monomer (m-5) were dissolved in 2-butanone (200 parts by mass) to give a molar ratio of 25 / 50 / 25 (mol %), and AIBN (azobisisobutyronitrile) (5 mol % relative to 100 mol % of the total monomers used) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in an empty reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was separated by filtration. The filtered white powder was washed twice with methanol, filtered, and dried at 50°C for 10 hours to obtain a white powdery polymer (A-1) (yield: 85%). The Mw of the polymer (A-1) was 6,600, and the Mw / Mn was 1.61. １３ As a result of C-NMR analysis, the contents of the structural units derived from the monomer (M-1), the monomer (m-1), and the monomer (m-5) were 24.2 mol%, 50.2 mol%, and 25.6 mol%, respectively.

[0253] [Synthesis Examples 2 to 27] (Synthesis of Polymers (A-2) to (A-27)) Polymers (A-2) to (A-27) were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of monomers shown in Tables 1 and 2 below were used. The content (mol %) of each structural unit and physical properties (Mw, Mw / Mn) of the obtained polymers are also shown in Tables 1 and 2 below. In Tables 1 to 4 below, "-" indicates that the corresponding monomer was not used.

[0254]

[0255]

[0256] Synthesis Example 28 Synthesis of Polymer (A-28) Monomer (M-1), monomer (m-1), and monomer (m-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) to give a molar ratio of 25 / 50 / 25 (mol %), and AIBN (5 mol %) was added as an initiator to prepare a monomer solution. 1-Methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled with water to below 30°C. The cooled polymerization solution was poured into hexane (2,000 parts by mass), and the precipitated white powder was separated by filtration. The white powder collected by filtration was washed twice with hexane, filtered, and then dissolved in 1-methoxy-2-propanol (300 parts by mass). Methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were then added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After completion of the reaction, the remaining solvent was distilled off. The resulting solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to coagulate the resin. The resulting solid was collected by filtration and dried at 50°C for 13 hours to obtain a white powdery polymer (A-28) (yield: 65%). The Mw of the polymer (A-28) was 7,000, and the Mw / Mn was 1.61. １３ As a result of C-NMR analysis, the contents of the structural units derived from the monomer (M-1), the monomer (m-1) and the monomer (m-18) were 25.2 mol %, 50.2 mol % and 24.6 mol %, respectively.

[0257] [Synthesis Examples 29 to 34] (Synthesis of Polymers (A-29) to (A-34)) Polymers (A-29) to (A-34) were synthesized in the same manner as in Synthesis Example 28, except that the types and blending ratios of monomers shown in Table 3 below were used. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained polymers are also shown in Table 3 below.

[0258] The monomer that provides the structural unit (V) in the polymer is １３C-NMR measurement confirmed that the peaks of the carbonyl groups of the acetyl groups had disappeared, and substantially all of the alkali-dissociable groups had been hydrolyzed to phenolic hydroxyl groups.

[0259]

[0260] Synthesis Example 35 (Synthesis of High Fluorine Content Polymer (E-1)) Monomer (m-2) and monomer (m-14) were dissolved in 2-butanone (200 parts by mass) to give a molar ratio of 30 / 70 (mol %), and AIBN (2 mol %) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerized solution was cooled with water to below 30°C. The solvent was replaced with acetonitrile (400 parts by mass), and then hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was recovered. This operation was repeated three times. The solvent was replaced with propylene glycol monomethyl ether acetate, yielding a solution of high fluorine content polymer (E-1) (yield: 87%). The high fluorine content polymer (E-1) had an Mw of 14,800 and an Mw / Mn ratio of 1.70. １３ As a result of C-NMR analysis, the contents of the structural units derived from the monomer (m-2) and the monomer (m-14) were 29.7 mol % and 70.3 mol %, respectively.

[0261] [Synthesis Examples 36 to 40] (Synthesis of high fluorine content polymers (E-2) to (E-6)) High fluorine content polymers (E-2) to (E-6) were synthesized in the same manner as in Synthesis Example 35, except that the types and blending ratios of monomers shown in Table 4 below were used. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained polymers are also shown in Table 4 below.

[0262]

[0263] <Preparation of Radiation-Sensitive Composition> Components other than the polymer (A) and the high-fluorine-content polymer (E) used in the preparation of each radiation-sensitive composition are shown below.

[0264] [B] Onium salts as radiation-sensitive acid generators (hereinafter also referred to as "radiation-sensitive acid generators") B-1 to B-12: Compounds represented by the following formulae (B-1) to (B-12):

[0265]

[0266] [C] Onium salts as acid diffusion controllers (hereinafter also referred to as "acid diffusion controllers") C-1 to C-6: Compounds represented by the following formulae (C-1) to (C-6):

[0267]

[0268] [D] Solvent D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol monomethyl ether D-3: γ-butyrolactone D-4: Ethyl lactate

[0269] <Preparation of positive-tone radiation-sensitive composition for ArF exposure> [Example 1] 100 parts by mass of [A] polymer (A-1), 10.0 parts by mass of [B] radiation-sensitive acid generator (B-1), 6.0 parts by mass of [C] acid diffusion controller (C-1), 3.0 parts by mass (solids content) of [E] high-fluorine content polymer (E-1), and 3,400 parts by mass of [D] solvent mixed solvent in a ratio of (D-1) / (D-2) / (D-3)=1500 / 1700 / 200 (parts by mass), were mixed and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-1).

[0270] [Examples 2 to 32, Examples 34 to 40, Examples 101 to 106, and Comparative Examples 1 to 7] Radiation-sensitive compositions (J-2) to (J-32), (J-34) to (J-40), (J-101) to (J-106), and (CJ-1) to (CJ-7) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 5 and 6 below were used.

[0271]

[0272]

[0273] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF Exposure> 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 100 nm. A positive radiation-sensitive composition for ArF exposure was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 100 nm. Next, this resist film was exposed to light through a 50 nm line-and-space mask pattern using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and annular (σ = 0.8 / 0.6). After exposure, a PEB (post-exposure bake) was performed at 100°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% aqueous TMAH solution as an alkaline developer, and after development, it was washed with water and further dried to form a positive resist pattern (50 nm line-and-space pattern).

[0274] <Evaluation> Resist patterns formed using the positive radiation-sensitive compositions for ArF exposure were evaluated for sensitivity, LWR performance, resist pattern rectangularity, and development defect suppression according to the methods described below. The results are shown in Table 7. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0275] [Sensitivity] In forming a resist pattern using a positive radiation-sensitive composition for ArF exposure, the exposure dose required to form a 50 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The sensitivity was 30 mJ / cm ２ The cases below are evaluated as "good" and 30 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0276] [LWR Performance] A resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation above, and adjusting the mask size to form a 50 nm line-and-space pattern. The formed resist pattern was observed from above the pattern using a scanning electron microscope. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line roughness and the better the result. The LWR performance was evaluated as "good" when it was 3.5 nm or less, and as "poor" when it exceeded 3.5 nm.

[0277] [Rectangularity of Resist Pattern] A 50 nm line-and-space resist pattern formed by irradiating with the optimum exposure dose obtained in the above sensitivity evaluation was observed using a scanning electron microscope, and the cross-sectional shape of the line-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape was 1.00 or more and 1.05 or less, "B" (good) if it was more than 1.05 and 1.10 or less, and "C" (poor) if it was more than 1.10.

[0278] [Number of Development Defects] A resist film was exposed at an optimum exposure dose to form a 50 nm line-and-space resist pattern, which was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 5 μm or less were determined to be derived from the resist film, and the number of defects was calculated. After development, the number of defects determined to be derived from the resist film was evaluated as "good" when the number of defects was 100 or less, and as "poor" when the number of defects was more than 100.

[0279]

[0280] As is clear from the results in Table 7, when the radiation-sensitive compositions of the Examples were used for ArF exposure, they exhibited good sensitivity, LWR performance, resist pattern rectangularity, and development defect suppression. In contrast, the Comparative Examples were inferior to the Examples in each of the properties. Therefore, it can be said that when the radiation-sensitive compositions of the Examples are used for ArF exposure, it is possible to form resist patterns that have high sensitivity, good LWR performance, and resist pattern shape, and that are capable of suppressing development defects.

[0281] <Preparation of Positive Radiation-Sensitive Composition for Extreme Ultraviolet (EUV) Exposure> [Example 41] 100 parts by mass of [A] polymer (A-28), 30.0 parts by mass of [B] radiation-sensitive acid generator (B-1), 20.0 parts by mass of [C] acid diffusion controller (C-1), [E] high fluorine content polymer (E-6), and 6,100 parts by mass of [D] solvent mixed solvent with a (D-1) / (D-2) / (D-4) ratio of 1500 / 4500 / 100 (parts by mass) ratio were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare radiation-sensitive composition (J-41).

[0282] Examples 42 to 49 and Comparative Examples 8 to 12 Radiation-sensitive compositions (J-42) to (J-49) and (CJ-8) to (CJ-12) were prepared in the same manner as in Example 40, except that the types and amounts of each component shown in Table 8 below were used.

[0283]

[0284] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for EUV Exposure> A composition for forming a bottom antireflective coating (Brewer Science's ARC66) was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron Limited's CLEAN TRACK ACT12), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. A positive radiation-sensitive composition for EUV exposure 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 55 nm. Next, this resist film was exposed using an EUV exposure apparatus (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% aqueous TMAH solution as an alkaline developer, and after development, the resist film was washed with water and further dried to form a positive resist pattern (20 nm line and space pattern).

[0285] <Evaluation> The sensitivity and LWR performance of the resist patterns formed using the positive radiation-sensitive compositions for EUV exposure were evaluated according to the methods described below. The results are shown in Table 9. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0286] [Sensitivity] In forming a resist pattern using a positive radiation-sensitive composition for EUV exposure, the exposure amount for forming a 20 nm line and space pattern is defined as the optimum exposure amount, and this optimum exposure amount is defined as the sensitivity (mJ / cm ２ The sensitivity was 40 mJ / cm ２ The following cases are considered "good" and 40 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0287] [LWR Performance] A resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation above, and adjusting the mask size to form a 20 nm line-and-space pattern. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line chatter and the better the result. The LWR performance was evaluated as "good" when it was 4.0 nm or less, and as "poor" when it exceeded 4.0 nm.

[0288]

[0289] As is clear from the results in Table 9, the radiation-sensitive compositions of the Examples had good sensitivity and LWR performance when used for EUV exposure. In contrast, the Comparative Examples were inferior in each property to the Examples.

[0290] Preparation of Negative Radiation-Sensitive Composition for ArF Exposure, and Formation and Evaluation of Resist Pattern Using This Composition Example 50 100 parts by mass of [A] polymer (A-20), 7.0 parts by mass of [B] radiation-sensitive acid generator (B-9), 4.0 parts by mass of [C] acid diffusion controller (C-1), 4.0 parts by mass (solids content) of [E] high-fluorine content polymer (E-3), and 3,230 parts by mass of [D] solvent mixed solvent with a (D-1) / (D-2) / (D-3) ratio of 2240 / 960 / 30 (mass ratio), were mixed, and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-50).

[0291] 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 having an average thickness of 85 nm. A negative radiation-sensitive composition for ArF exposure (J-50) was applied to this bottom antireflective coating using the spin coater, and prebaked at 90°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film having an average thickness of 90 nm. Next, this resist film was exposed to light using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and annular (σ = 0.8 / 0.6) through a mask pattern with 60 nm holes and a 120 nm pitch. After exposure, a post-exposure bake (PEB) was performed at 90°C for 60 seconds. The resist film was then developed using n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (a pattern with 60 nm holes and a 120 nm pitch).

[0292] The resist patterns prepared using the negative-working radiation-sensitive composition for ArF exposure were evaluated for sensitivity in the same manner as in the evaluation of the resist patterns prepared using the positive-working radiation-sensitive composition for ArF exposure. The CDU performance and pattern circularity were also evaluated according to the following methods.

[0293] [CDU Performance] Contact holes with a 60 nm hole and a 120 nm pitch were formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The variation in the diameter of the contact holes was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as CDU (nm). The smaller the CDU value, the smaller the hole roughness and the better the result. CDU performance was evaluated as "good" when it was less than 3.5 nm, and as "poor" when it was 3.5 nm or more.

[0294] [Pattern circularity] The 60 nm holes and 120 nm pitch contact holes formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation were observed in plan view using the scanning electron microscope, and their vertical and horizontal sizes were measured. A ratio of vertical size to horizontal size of 0.95 or more and less than 1.05 was evaluated as "A" (very good), a ratio of 0.90 or more and less than 0.95 or 1.05 or more and less than 1.10 was evaluated as "B" (good), and a ratio of less than 0.90 or 1.10 or more was evaluated as "C" (poor).

[0295] As a result, the radiation-sensitive composition of Example 50 exhibited good sensitivity, CDU performance, and pattern circularity even when a negative resist pattern was formed by ArF exposure.

[0296] <Preparation of Negative Radiation-Sensitive Composition for EUV Exposure, and Formation and Evaluation of Resist Pattern Using This Composition> [Example 51] 100 parts by mass of [A] (A-29) as a polymer, [B] 50.0 parts by mass of (B-11) as a radiation-sensitive acid generator, [C] 40.0 parts by mass of (C-5) as an acid diffusion controller, [E] 5.0 parts by mass of (E-6) as a high-fluorine-content polymer, and [D] 6,000 parts by mass of a mixed solvent in which (D-1) / (D-2)=1000 / 5000 (mass ratio) as a solvent were mixed, and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-51).

[0297] 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. A negative radiation-sensitive composition for EUV exposure (J-51) 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 55 nm. Next, this resist film was exposed to light using an EUV exposure system ("NXE3300" from ASML) with NA=0.33, illumination conditions: Conventional s=0.89, and a mask: imecDEFECT32FFR15. After the exposure, PEB was performed for 60 seconds at 120° C. Thereafter, the resist film was developed with n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (a contact hole pattern with 20 nm holes and a 40 nm pitch).

[0298] The resist pattern formed using the negative-tone radiation-sensitive composition for EUV exposure was evaluated in the same manner as the evaluation of the resist pattern formed using the negative-tone radiation-sensitive composition for ArF exposure. As a result, the radiation-sensitive composition of Example 51 exhibited good sensitivity, CDU performance, and pattern circularity, even when a negative-tone resist pattern was formed by EUV exposure.

[0299] The radiation-sensitive composition and pattern forming method described above can form a resist pattern that has good sensitivity to exposure light and is excellent in LWR performance, pattern rectangularity, development defect suppression, CDU performance, and pattern circularity. Therefore, these compositions can be suitably used in processing processes for semiconductor devices, which are expected to become increasingly miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a polymer containing a structural unit (I) represented by the following formula (1); an onium salt containing an organic acid anion having a cyclic structure and an onium cation; and a solvent. (In the above formula (1), R １ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. L is a single bond or a divalent linking group. R ２ R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxyl group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ When there are multiple R ３ are the same or different; n is an integer from 0 to 10.

2. R １ 2. The radiation-sensitive composition according to claim 1, wherein is a monovalent organic group having 1 to 5 carbon atoms.

3. The radiation-sensitive composition according to claim 1, wherein n is 0 or 1.

4. The radiation-sensitive composition according to claim 1, wherein the content of the structural unit (I) in all structural units constituting the polymer is from 1 mol % to 60 mol %.

5. The radiation-sensitive composition according to claim 1, wherein the polymer further comprises a structural unit (II) which is different from the structural unit (I) and has an acid-dissociable group.

6. The radiation-sensitive composition according to claim 5, wherein the content of the structural unit (II) in all structural units constituting the polymer is from 1 mol % to 60 mol %.

7. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the organic acid anion has a sulfonate anion, and a fluorine atom, a fluorinated hydrocarbon group, or a cyano group is bonded to at least one selected from the group consisting of a carbon atom at the α-position and a carbon atom at the β-position relative to a sulfur atom in the sulfonate anion.

8. The radiation-sensitive composition according to any one of claims 1 to 6, wherein the organic acid anion has a sulfonate anion or a carboxylate anion (provided that, when the organic acid anion has the sulfonate anion, a fluorine atom or a fluorinated hydrocarbon group is not bonded to both the carbon atom at the α-position and the carbon atom at the β-position relative to the sulfur atom in the sulfonate anion).

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

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

11. The pattern forming method according to claim 10, wherein the exposure is carried out with an ArF excimer laser or extreme ultraviolet light.

12. A compound represented by the following formula (1-a): (In the above formula (1-a), R １ａ R is a monovalent organic group having 1 to 20 carbon atoms. ２ａ R is a substituted or unsubstituted monovalent hydrocarbon group having 3 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxyl group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ When there are multiple R ３ are the same or different; n is an integer from 0 to 10.

13. A compound represented by the following formula (1-b): (In the above formula (1-b), R １ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ is a divalent linking group. ２ R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 5 carbon atoms. ３ R is a monovalent organic group having 1 to 10 carbon atoms, a hydroxyl group, a nitro group, a cyano group, an amino group, a halogen atom, or a sulfanyl group. ３ When there are multiple R ３ are the same or different; n is an integer from 0 to 10.

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