Radiation-sensitive composition and pattern formation method

Abstract

Provided are a radiation-sensitive composition and a pattern formation method that are capable of, when forming a pattern, exhibiting sensitivity, CDU, development defect suppression property, and film thickness uniformity at levels equal to or higher than conventional levels.　This radiation-sensitive composition comprises: a first polymer having a structural unit (I) including an acid dissociable group; a second polymer different from the first polymer; and a solvent. The second polymer has a structural unit (i) derived from a compound represented by formula (ia). (In formula (ia), W represents a polymerizable group. L represents a linking group. A represents *-CO-NH- or *-NH-CO-. R1 represents: a monovalent hydrocarbon group having 1-20 carbon atoms; or a group including, between carbon atoms of the hydrocarbon group, -CO-, -CS-, -O-, -S-, -SO2-, -NR'-, or a combination of two or more thereof. R' represents a hydrogen atom or a hydrocarbon group having 1-10 carbon atoms.

Description

Radiation-sensitive composition and pattern forming method

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

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the polymer in an alkaline or organic solvent-based developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

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

[0004] As patterns become finer, a technique has been proposed in which a fluorine- or silicon-containing polymer is added to a resist composition for the purpose of controlling the quality of the resist film (Japanese Patent Application Laid-Open No. 2013-68646).

[0005] JP 2013-68646 A

[0006] In order to develop the above-mentioned next-generation technologies, resist performance equivalent to or better than conventional ones is required in terms of sensitivity, critical dimension uniformity (CDU) which is an index of uniformity of line width and hole diameter, suppression of development defects, film thickness uniformity, etc.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method which, when forming a pattern, can exhibit sensitivity, CDU, suppression of development defects, and film thickness uniformity at levels equal to or higher than conventional levels.

[0008] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a first polymer having a structural unit (I) containing an acid-labile group; a second polymer different from the first polymer; and a solvent, wherein the second polymer has a structural unit (i) derived from a compound represented by the following formula (ia): (In formula (ia), W represents a polymerizable group. L represents a single bond or a divalent linking group. A represents ＊ —CO—NH— or ＊ -NH-CO-. * indicates a bond on the W side. R １ represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having —CO—, —CS—, —O—, —S—, or —SO— between carbon atoms of the hydrocarbon group. ２ -, -NR'-, or a group containing a combination of two or more of these. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. １ When A in formula (ia) contains an aromatic hydrocarbon group, it contains at least one carbon atom or hetero atom between A in formula (ia) and the aromatic hydrocarbon group.

[0010] The radiation-sensitive composition can exhibit excellent sensitivity, as well as CDU, suppression of development defects, and film thickness uniformity that are equal to or better than those of conventional compositions during resist pattern formation. Although the reason for this is unclear, it is presumed to be as follows.

[0011] This radiation-sensitive composition achieves a balance between the hydrophilicity resulting from the amide bond portion of the structural unit (i) in the second polymer and the hydrophobicity resulting from the hydrocarbon group or the hydrocarbon group containing a heteroatom, thereby enabling appropriate modification of the film quality of the resist film. Furthermore, by assigning the film quality modifying function to the amide bond and the hydrocarbon group, etc., it becomes possible to design a resist film with a reduced amount of fluorine atoms, which can affect electron scattering. Furthermore, the structural unit (i) containing the hydrophilic amide bond can improve the solubility of the surface layer of the resist film in a developer during alkaline development after exposure. It is believed that these combined effects enable the resist performance described above to be exhibited.

[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, which is capable of exhibiting excellent sensitivity, as well as CDU, suppression of development defects, and film thickness uniformity equivalent to or greater than those of conventional compositions, when forming a resist pattern, and therefore can efficiently form a high-quality resist pattern.

[0014] As used herein, the term "organic group" refers to a group having at least one carbon atom.

[0015] 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.

[0016] Radiation-Sensitive Composition The radiation-sensitive composition according to this embodiment (hereinafter also referred to simply as the "composition") contains a first polymer (hereinafter also referred to as the "base polymer"), a second polymer, and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0017] <First Polymer> The first polymer (i.e., base polymer) is an aggregate of polymer chains having a structural unit (I) containing an acid-dissociable group. In addition to the structural unit (I), the base polymer may also contain a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (II)"), a structural unit containing a lactone structure or the like (hereinafter also referred to as "structural unit (III)"), a structural unit containing a polar group (hereinafter also referred to as "structural unit (IV)"), a structural unit containing an acid-generating structure (hereinafter also referred to as "structural unit (V)" or "structural unit (VI)" depending on the acid generated), etc.

[0018] The first polymer preferably contains an iodine group. By incorporating an iodine group into the base polymer, the radiation absorption efficiency increases, and the secondary electron generation efficiency increases, thereby improving sensitivity. The iodine group may be contained in the structural unit (I) or in another structural unit. In particular, it is preferable that the iodine group be contained in the acid-dissociable group (a portion that dissociates with acid) of the structural unit (I).

[0019] When an iodo group is introduced into the first polymer, the iodo group is preferably present in the form of an iodo group-containing aromatic ring structure, in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodo groups.

[0020] The aromatic ring in the iodo group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity.Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, aromatic heterocycles such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, and combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0021] The number of iodine atoms in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 1 or 2.

[0022] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. Upon exposure, an acid generated from the acid-generating structure in the base polymer containing the structural unit (II) or from the radiation-sensitive acid generator dissociates the acid-dissociable group in the structural unit (I) to generate a carboxyl group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0023] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, a structural unit having an acetal bond, etc. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (1) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0024] (In formula (1), R ａ is a hydrogen atom, a fluorine atom, a methyl group, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. α is a divalent linking group. １Ａ and R １Ｂ are each independently a hydrogen atom, a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, 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. １Ａ and R １Ｂ There is no case where both of Ar and Ar are hydrogen atoms. １ａ is a (p+q+1)-valent aromatic ring having 5 to 20 ring members. １０１ is a nitro group, a cyano group, a hydroxy group, an alkoxy group, or an amino group. １０１ If there are multiple R １０１ are the same or different. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1. p is an integer of 1 to 3. q is an integer of 0 to 3. However, p+q is 5 or less.

[0025] R ａ Examples of the alkyl group having 1 to 6 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group.

[0026] R ａWhen the alkyl group having 1 to 6 carbon atoms, represented by the formula (I), has a substituent, examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an amino group; an alkoxy group; an alkoxycarbonyl group; an alkoxycarbonyloxy group; an acyl group; an acyloxy group or a group in which a hydrogen atom of any of these groups has been substituted with a halogen atom; and an oxo group (═O).

[0027] R ａ Examples of the alkoxy group as a substituent include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, and a propoxy group. Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as a methoxycarbonyl group and an ethoxycarbonyl group. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as a methoxycarbonyloxy group, a butoxycarbonyloxy group, and an adamantylmethyloxycarbonyloxy group. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as an acetyl group, a propionyl group, a benzoyl group, and an acryloyl group. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as an acetyloxy group, a propionyloxy group, a benzoyloxy group, and an acryloyloxy group.

[0028] The above R ａ As the alkyl group, a hydrogen atom and a methyl group are preferred from the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1).

[0029] L α Examples of the divalent linking group represented by the formula (I) include a divalent hydrocarbon group such as an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, or an arenediyl group, a divalent heteroatom-containing group, a group in which the divalent heteroatom-containing group is incorporated between the carbon-carbon bonds of the divalent hydrocarbon group, or a group combining these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the divalent heteroatom-containing group include -CO-, -CS-, -O-, -S-, and -SO ２-, -NR'-, or a group consisting of two or more of these. Some or all of the hydrogen atoms in these groups can be substituted by R ａ may be substituted with a substituent that may be possessed by the group.

[0030] 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, or a 2,2-propanediyl group.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] L α The divalent linking group represented by the formula (I) is preferably an alkanediyl group or an arenediyl group, more preferably an alkanediyl group having 1 to 4 carbon atoms or an arenediyl group having 6 to 10 carbon atoms, and even more preferably a methanediyl group or a benzenediyl group.

[0035] R １Ａ and R １ＢExamples of the monovalent linear hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 2 to 10 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group. Examples of the monovalent linear or branched unsaturated hydrocarbon group having 2 to 10 carbon atoms include alkenyl groups such as an ethenyl group, a propenyl group, and a butenyl group; and alkynyl groups such as an ethynyl group, a propynyl group, and a butynyl group.

[0036] R １Ａ and R １Ｂ Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups include cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Preferred polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl groups. Note that a bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0037] R １Ａ and R １Ｂ As the divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, a group in which one hydrogen atom has been removed from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used.

[0038] R１Ａ and R １Ｂ is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R １Ａ and R １Ｂ are combined together together with the carbon atoms to which they are bonded, a divalent alicyclic group having 3 to 20 carbon atoms is preferred, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a divalent alicyclic group having 5 to 10 carbon atoms is more preferred, and a methyl group, an ethyl group, a cyclopentanediyl group, or a cyclohexanediyl group is even more preferred.

[0039] Ar １ａ As the aromatic ring in the above, the aromatic ring in the iodo group-containing aromatic ring structure can be suitably used. １ａ The aromatic ring in Ar is preferably a benzene ring, a thiophene ring or a furan ring, and more preferably a benzene ring. １ａ The aromatic ring having 5 to 20 ring members and a valence of (p+q+1) is represented by the above Ar １ａ A group in which (p+q+1) hydrogen atoms have been removed from the aromatic ring of the formula (I) can be suitably used.

[0040] R １０１ The alkoxy group represented by the formula (1) is R ａ Examples of the alkoxy groups include those shown as the substituents of the above.

[0041] p is preferably 1 or 2. q is preferably 0 or 1.

[0042] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (I).

[0043]

[0044] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer from 1 to 4.

[0045] The above R βｆ is preferably a hydrogen atom, a methyl group, or an ethyl group.１ As the number, 1 or 2 is preferred.

[0046] Specific examples of the structural unit (I) (including the structural unit (I-1)) are not particularly limited, but include structural units represented by the following formulae (1-1) to (1-60).

[0047]

[0048]

[0049]

[0050]

[0051]

[0052] In the formula, R ａ is synonymous with the above formula (1).

[0053] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved. When the acid-dissociable group has an iodine group, sensitivity can be further improved.

[0054] (Structural Unit (II)) The structural unit (II) is a structural unit having a phenolic hydroxyl group (excluding the structure corresponding to the structural unit (I)). When the base polymer contains the structural unit (II), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (II) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (II) is suitably applied to pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (II) is preferably represented by the following formula (2):

[0055] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ is a single bond, -COO- ＊ , —O— or —CONH— ＊ * is a bond on the aromatic ring side. １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４ are each independently an integer of 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0056] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (II), the alkyl group is preferably a hydrogen atom or a methyl group.

[0057] L ＣＡ is a single bond or -COO- ＊ is preferred.

[0058] R １０２ The halogen atom, alkyl group, alkoxycarbonyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the above formula (1) is ａ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom or a fluorine atom, more preferably an iodine atom.

[0059] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0060] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0061] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0062] The structural unit (II) is preferably a structural unit represented by the following formulas (2-1) to (2-24) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-24)").

[0063]

[0064]

[0065] In the above formulas (2-1) to (2-24), R β is the same as the above formula (2).

[0066] When the base polymer has the structural unit (II), the lower limit of the content of the structural unit (II) (total content when multiple types of structural unit (II) are present) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of this content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of the structural unit (II) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast.

[0067] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferable to polymerize the monomer in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then to obtain the structural unit (II) by deprotecting the phenolic hydroxyl group by hydrolysis. The hydroxystyrene may also be polymerized without protecting the phenolic hydroxyl group.

[0068] (Structural Unit (III)) The structural unit (III) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (III), the base polymer can adjust its solubility in a developer, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0069] Examples of the structural unit (III) include structural units represented by the following formulae (T-1) to (T-11).

[0070]

[0071] 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.

[0072] The above R Ｌ４ and R Ｌ５ Examples of 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 include R１Ａ and R １Ｂ 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.

[0073] 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-.

[0074] Of these, the structural unit (III) is preferably a structural unit containing a lactone structure, and more preferably a structural unit containing a γ-butyrolactone structure, a norbornane lactone structure, or an adamantane lactone structure.

[0075] When the base polymer has the structural unit (III), the lower limit of the content of the structural unit (III) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 55 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.

[0076] (Structural Unit (IV)) The structural unit (IV) is a structural unit containing a polar group (excluding those corresponding to the structural units (I) to (III)). By further including the structural unit (IV), the base polymer can adjust its solubility in a developer. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, a sulfo group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0077] Examples of the structural unit (IV) include structural units represented by the following formula:

[0078]

[0079]

[0080] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0081] When the base polymer has the structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) (when a plurality of types are contained, the total content) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol% relative to the total structural units constituting the base polymer.The upper limit of the content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol%.By making the content of the structural unit (IV) within the above range, the solubility of the base polymer in the developer can be efficiently adjusted.

[0082] (Structural Unit (V)) The base polymer may contain a structural unit (V) including a first acid generating structure that has a first organic acid anion and a first onium cation and generates an acid that dissociates the acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (i.e., the first acid generating structure) functions as a radiation-sensitive acid generating structure.

[0083] When the base polymer contains the radiation-sensitive acid generating structure, the polarity of the base polymer in the exposed area increases, making it soluble in the developer when developed with an aqueous alkaline solution, but making it poorly soluble in the developer when developed with an organic solvent.

[0084] The form in which the first organic acid anion and the first onium cation are contained in the structural unit (V) of the base polymer is not particularly limited. The base polymer may have the first organic acid anion as a side chain moiety, or the first onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the first organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the first onium cation is ionically bonded to the first organic acid anion as a counter ion of the first organic acid anion. On the other hand, when the first onium cation is bonded to the main chain of the base polymer as a side chain structure, the first organic acid anion is ionically bonded to the first onium cation as a counter ion of the first onium cation. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer have the first organic acid anion as a side chain moiety.

[0085] The first organic acid anion preferably has, as an acid anion moiety, at least one selected from the group consisting of a sulfonate anion and a sulfonimide anion. Examples of the acid generated by exposure include sulfonic acid and sulfonimide, corresponding to the acid anion moiety.

[0086] The first organic acid anion preferably includes, as a structure other than the acid anion moiety, -O-, -CO-, a cyclic structure, or a combination thereof. The combination also includes a structure (heterocyclic structure) in which -O- or -CO- is incorporated as a ring-forming moiety in the cyclic structure.

[0087] The cyclic structure may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to form a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the skeleton of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0088] The divalent heteroatom-containing group is L in the above formula (1). α The divalent heteroatom-containing groups shown in the following formula can be preferably employed.

[0089] The substituents that substitute a part or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include R ａ The substituents shown in the following can be preferably employed.

[0090] In the first acid generating structure, the first organic acid anion preferably has a sulfonate anion as the acid anion moiety, and an electron-withdrawing group is bonded to a carbon atom at the α- or β-position relative to the sulfur atom in the sulfonate anion. This allows the first acid generating structure to efficiently exhibit the above-mentioned function. Examples of the electron-withdrawing group include a fluorine atom, a fluorinated hydrocarbon group, a nitro group, and a cyano group. The fluorinated hydrocarbon group is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0091] The first organic acid anion preferably has an iodo group. The first organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0092] The first onium cation may be a radioactive onium cation. Examples of the radioactive onium cation include a sulfonium cation, a tetrahydrothiophenium cation, and an iodonium cation. Among these, a sulfonium cation or an iodonium cation is preferred, and a sulfonium cation is more preferred.

[0093] The first onium cation preferably has an iodo group. The first onium cation preferably contains the iodo group-containing aromatic ring structure.

[0094] The first onium cation in the structural unit (V) may be a fluoro-group-containing onium cation having a fluoro group. The fluoro-group-containing onium cation preferably has a fluoro-group-containing aromatic ring structure. The fluoro-group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with fluoro groups. The aromatic ring in the fluoro-group-containing aromatic ring structure can be suitably an aromatic ring in an iodine-group-containing aromatic ring structure. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0095] The structural unit (V) having the above structures in combination can efficiently exhibit the above functions.

[0096] The structural unit (V) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (V-1)").

[0097]

[0098] In the formula, R Ｖ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, or an amide bond, and some of the methylene groups constituting the alkylene group, cycloalkylene group, or arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ represents a single bond, an ether group, an ester group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and some of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３ Some or all of the hydrogen atoms in Rf may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. １ ~Rf ２are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. kk is an integer of 1 to 4. Z １ ＋ is a sulfonium cation or an iodonium cation.

[0099] V ２ and V ３ The monovalent hydrocarbon group having 1 to 20 carbon atoms in the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group, or a sulfonium salt-containing group, an alkoxy group, or an alkoxycarbonyl group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group, or a sulfonate ester group.

[0100] The structural unit (V-1) is preferably a structural unit represented by the following formula (a1-1).

[0101]

[0102] In the formula, R Ｖ , Rf １ ~Rf ２ , V １ , kk and Z １ ＋ has the same meaning as in formula (a1). ４８ is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 0 to 4. n is an integer of 0 to 3.

[0103] Examples of the first organic acid anion of the monomer that gives the structural unit (V) (including the structural unit (V-1)) include, but are not limited to, those shown below. In the following, the iodo group of the iodo group-containing aromatic ring structure may be a hydrogen atom or an R ａ In the following formula, R Ｖ is synonymous with the above.

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] In the above formula, R Ｖ has the same meaning as the above formula (a1).

[0111] Z in the above formula (a1) １ ＋ is preferably a sulfonium cation represented by the following formula (Q-1):

[0112]

[0113] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or greater, multiple Ra2s may be the same or different. Ra3 represents a substituent. n3 represents an integer of 0 to 5, and when n3 is 2 or greater, multiple Ra3s may be the same or different. Ra1 and Ra2 may be bonded to each other to form a ring. When n1 is 2 or greater, multiple Ra1s may be bonded to each other to form a ring. When n2 is 2 or greater, multiple Ra2s may be bonded to each other to form a ring.

[0114] The substituents represented by Ra1, Ra2 and Ra3 are preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom or a halogenated hydrocarbon group.

[0115] The alkyl groups of Ra1 and Ra2 may be linear or branched. The alkyl groups preferably have 1 to 10 carbon atoms, and examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl, 2-methylpropyl, 1-methylpropyl, t-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl. Of these, methyl, ethyl, n-butyl, and t-butyl are particularly preferred.

[0116] The cycloalkyl group of Ra1 and Ra2 includes a monocyclic or polycyclic cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Of these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0117] Examples of the alkyl group moiety of the alkoxy group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferred.

[0118] Examples of the cycloalkyl group moiety of the cycloalkyloxy group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0119] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1 and Ra2 include those previously listed as the alkoxy group of Ra1 and Ra2. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0120] Examples of the alkyl group moiety of the alkylsulfonyl group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. Also, examples of the cycloalkyl group moiety of the cycloalkylsulfonyl group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. Particularly preferred alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl.

[0121] Each of the groups Ra1 and Ra2 may further have a substituent, such as a halogen atom such as a fluorine atom (preferably a fluorine atom), a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, a cycloalkyloxyalkyl group, an alkoxycarbonyl group, a cycloalkyloxycarbonyl group, an alkoxycarbonyloxy group, and a cycloalkyloxycarbonyloxy group.

[0122] Examples of the halogen atom for Ra1 and Ra2 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and an iodine atom being preferred.

[0123] The halogenated hydrocarbon group of Ra1 and Ra2 is preferably a halogenated alkyl group. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF ３ is more preferred.

[0124] As described above, Ra1 and Ra2 may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 are bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２ -, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more thereof, and preferably has a total carbon number of 20 or less. When Ra1 and Ra2 are bonded to each other to form a ring, Ra1 and Ra2 are bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ It is preferable to form - or a single bond. Among these, it is more preferable to form -O-, -S- or a single bond, and it is particularly preferable to form a single bond. Furthermore, when n1 is 2 or more, multiple Ra1s may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2s may be linked to each other to form a ring. Such an example includes, for example, an embodiment in which two Ra1s are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0125] Ra3 is preferably a fluorine atom, a group having one or more fluorine atoms, or an iodine atom. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluorine atom. Among these, fluorinated alkyl groups are preferred, and CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ , C.H. ２ CF ３ , C.H. ２ CH ２CF ３ , C.H. ２ C ２ F ５ , C.H. ２ CH ２ C ２ F ５ , C.H. ２ C ３ F ７ , C.H. ２ CH ２ C ３ F ７ , C.H. ２ C ４ F ９ and CH ２ CH ２ C ４ F ９ More preferred examples include CF ３ are particularly preferred.

[0126] Ra3 is a fluorine atom, an iodine atom, or CF ３ is preferably, and more preferably, a fluorine atom or an iodine atom.

[0127] n1 and n2 each independently represent preferably an integer of 0 to 3, more preferably an integer of 0 to 2.

[0128] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0129] (n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, n3=1 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=2 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ A combination in which:

[0130] Specific examples of such sulfonium cations represented by the above formula (Q-1) include the following: The fluorine atom and iodine atom in the following sulfonium cations can be substituted with hydrogen atoms or R ａ It may be substituted with the substituents shown in the above.

[0131]

[0132]

[0133]

[0134]

[0135] The first onium cation of the structural unit (V) may be a diaryliodonium cation. The diaryliodonium cation preferably has one or more fluorine atoms or iodine atoms. At least one of the aryl groups of the iodonium cation preferably has a fluoro- or iodo-containing aromatic ring structure. The aryl group is preferably a phenyl group.

[0136] It is also possible to adopt an embodiment in which a first onium cation is bonded to the main chain as a side chain structure of the base polymer, and a first organic acid anion is bonded to the first onium cation as a counter ion through an ionic bond. In this case, the first onium cation is bonded to the main chain via a divalent linking group or a single bond, and V in the above formula (a1) ２ From SO ３ - The structure up to is preferably ionically bonded to the first onium cation as a counter ion. α The group represented by the following formula (I), the above divalent heteroatom-containing group, or a combination thereof can be suitably employed.

[0137] When the base polymer has the structural unit (V), the lower limit of the content of the structural unit (V) (when multiple types are contained, the total content) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of the structural unit (V) within the above range, the function as an acid generating structure can be fully exerted, and the above resist properties can be exhibited.

[0138] The monomer that provides the structural unit (V-1) can be synthesized, for example, in the same manner as in the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0139] (Structural Unit (VI)) The base polymer may contain a structural unit (VI) including a second acid generating structure having a second organic acid anion and a second onium cation, which generates an acid that does not dissociate the acid-dissociable group upon exposure. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the radiation-sensitive composition, the second acid generating structure does not substantially dissociate the acid-dissociable group of the structural unit (I), and has the function of suppressing the diffusion of acid generated from the first acid generating structure or the radiation-sensitive acid generator (if included) in unexposed areas through salt exchange. The acid generated from the second acid generating structure can be said to be a relatively weaker acid (an acid with a higher pKa) than the acid generated from the first acid generating structure. Whether the onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable group of the base polymer and the acidity of the onium salt structure or the acid generated.

[0140] The form in which the second organic acid anion and the second onium cation are contained in the structural unit (VI) of the base polymer is not particularly limited. The base polymer may have the second organic acid anion as a side chain moiety, or the second onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the second organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the second onium cation is ionically bonded to the second organic acid anion as a counter ion of the second organic acid anion. On the other hand, when the second onium cation is bonded to the main chain of the base polymer as a side chain structure, the second organic acid anion is ionically bonded to the second onium cation as a counter ion of the second onium cation. From the viewpoint of development contrast, it is preferable that the base polymer have the second organic acid anion as a side chain moiety.

[0141] The second organic acid anion preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety, and more preferably a carboxylate anion. However, when the second organic acid anion has the sulfonate anion, no electron-withdrawing group is bonded to the carbon atom at the α- or β-position relative to the sulfur atom in the sulfonate anion. Examples of the electron-withdrawing group include electron-withdrawing groups that the first organic acid anion may have in the first acid-generating structure. The acid generated by exposure is a carboxylic acid or sulfonic acid corresponding to the acid anion moiety.

[0142] The second organic acid anion preferably contains, as a structure other than the acid anion moiety, -O-, -CO-, a cyclic structure, or a combination thereof. As such a structure, the structures shown for the first organic acid anion can be suitably adopted.

[0143] The second organic acid anion preferably has an iodo group or a hydroxy group. The second organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0144] Examples of the second onium cation include radiolytic and non-radiolytic onium cations. Examples of the radiolytic and non-radiolytic onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, and ammonium cation. Among these, sulfonium cation and iodonium cation are preferred, and sulfonium cation is more preferred.

[0145] The second onium cation preferably has an iodo group. The second onium cation preferably contains the iodo group-containing aromatic ring structure.

[0146] The second onium cation in the structural unit (VI) preferably has the above-mentioned fluoro group-containing aromatic ring structure, which increases the radiation absorption efficiency and thereby improves sensitivity.

[0147] The structural unit (VI) having the above structures in combination can efficiently exhibit the above functions.

[0148] The structural unit (VI) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (VI-1)").

[0149]

[0150] In formula (p1), R A is a hydrogen atom or a methyl group.

[0151] In formula (p1), X 1 represents a single bond, an ester bond, an ether bond, a phenylene group, a naphthylene group, or a combination thereof.

[0152] In formula (p1), X ２ represents a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may contain an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２ The hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a butane-2,2-diyl group, a butane-2,3-diyl group, a 2-methylpropane-1,3-diyl group, a alkanediyl groups having 1 to 12 carbon atoms, such as diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group; cyclic saturated hydrocarbylene groups having 3 to 12 carbon atoms, such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group; and groups obtained by combining these.

[0153] In formula (p1), X 3 is a single bond, an ester bond or an ether bond.

[0154] In formula (p1), X1 ~X ２ Some or all of the hydrogen atoms in may be substituted with a substituent. ａ The substituents shown in the following can be preferably employed. 1 ~X ２ When has a phenylene group, it is preferred that some or all of the hydrogen atoms of the phenylene group are substituted with fluorine atoms or iodine atoms.

[0155] In formula (p1), Z ２ ＋ is Z in the above formula (a1). １ ＋ is synonymous with.

[0156] The second onium cation in the formula (p1) may be an iodonium cation. As the iodonium cation, a diaryliodonium cation shown as the onium cation of the structural unit (V-1) may be suitably used.

[0157] Examples of the second organic acid anion of the monomer that gives the structural unit (VI) include, but are not limited to, those shown below. Note that although all of the second organic acid anions shown below have an iodine group or a hydroxyl group, the structural unit (VI) does not necessarily require an iodine group or a hydroxyl group. The second organic acid anion that does not have an iodine group or a hydroxyl group is an anion in which the iodine group or the hydroxyl group in the following formula is replaced with a hydrogen atom or the R ａ In the following formula, a structure substituted with a substituent or the like shown in the following formula can be preferably employed. Ａ is the same as above. The second organic acid anion preferably has a carboxylate anion and a hydroxy group. In this case, it is preferable that the carboxylate anion and the hydroxy group are bonded to the same aromatic ring in the second organic acid anion, and it is more preferable that the carbon atom to which the carboxylate anion is bonded and the carbon atom to which the hydroxy group is bonded are directly bonded to each other in the same aromatic ring.

[0158]

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165] As the second onium cation of the structural unit (VI), a sulfonium cation represented by the above formula (Q-1) can be suitably used.

[0166] It is also possible to adopt an embodiment in which a second onium cation is bonded to the main chain as a side chain structure of the base polymer, and a second organic acid anion is bonded to the second onium cation by an ionic bond as a counter ion of the second onium cation. In this case, the second onium cation is bonded to the main chain via a divalent linking group or a single bond, and X in the above formula (p1) １ From COO - The structure up to is preferably ionically bonded to the second onium cation as a counter ion. α or the above-mentioned divalent heteroatom-containing group can be suitably employed.

[0167] When the base polymer contains the structural unit (VI), the lower limit of the content of the structural unit (VI) (the total content when multiple types are contained) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 20 mol%, based on the total amount of the monomer that provides the structural unit (V) and the radiation-sensitive acid generator (when both are contained). The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. When an optional acid diffusion controller is contained, the total amount of the monomer that provides the structural unit (VI) and the acid diffusion controller may be within the above range. By setting the content of the structural unit (VI) within the above range, the function of the acid diffusion control structure can be fully exhibited.

[0168] (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.

[0169] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight average molecular weight (Mw) as calculated on a polystyrene basis by gel permeation chromatography (GPC) is preferably 1,500, more preferably 1,800, and even more preferably 2,200. The upper limit of Mw is preferably 20,000, more preferably 16,000, and even more preferably 14,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0170] 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.

[0171] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0172] The lower limit of the content of the base polymer is preferably 40% by mass, more preferably 50% by mass, and even more preferably 60% by mass, based on the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 98% by mass, more preferably 96% by mass.

[0173] <Second Polymer> The radiation-sensitive composition of this embodiment includes a second polymer different from the base polymer. The second polymer has a structural unit (i).

[0174] It is preferable that the second polymer further contains, as a structural unit other than the structural unit (i), at least one selected from the group consisting of: a structural unit (ii) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure; a structural unit (iii) containing an alcoholic hydroxyl group; a structural unit (iv) containing an ammonium cation structure or a phosphonium cation structure and an acid anion; and a structural unit (v) containing a fluorine atom.

[0175] (Structural Unit (i)) The structural unit (i) is a structural unit derived from a compound represented by the following formula (ia). By introducing the structural unit (i) into the second polymer, it is possible to cause the structural unit (i) to be unevenly distributed in the surface layer of the resist film relative to the base polymer, and as a result, it is possible to control the surface modification of the resist film during EUV exposure, the distribution of the composition within the film, and improve the solubility in a developer. The second polymer may contain only one type of structural unit (i), or may contain two or more types. (In formula (ia), W represents a polymerizable group. L represents a single bond or a divalent linking group. A represents ＊ —CO—NH— or ＊ -NH-CO-. * indicates a bond on the W side. R １ represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having —CO—, —CS—, —O—, —S—, or —SO— between carbon atoms of the hydrocarbon group. ２ -, -NR'-, or a group containing a combination of two or more of these. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. １ When A in formula (ia) contains an aromatic hydrocarbon group, it contains at least one carbon atom or hetero atom between A in formula (ia) and the aromatic hydrocarbon group.

[0176] The polymerizable group represented by W includes an ethylenically unsaturated double bond or a structure containing an ethylenically unsaturated double bond as a partial structure constituting a ring. １ It may have a substituent other than the part bonded to

[0177] When the polymerizable group has a substituent, examples of the substituent include a halogen atom, a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a carboxy group, a cyano group, a nitro group, and an oxo group (═O).

[0178] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0179] Examples of the monovalent organic group having 1 to 20 carbon atoms include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (α) having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the terminal of the hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group or the group (α) have been substituted with a monovalent heteroatom-containing group, and combinations thereof.

[0180] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group 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, or a combination thereof.

[0181] The monovalent chain hydrocarbon group having 1 to 20 carbon atoms includes R １Ａ A group in which the monovalent hydrocarbon group having 1 to 10 carbon atoms shown in the above formula (I) is extended to have 20 carbon atoms can be suitably used.

[0182] The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms includes R １Ａ Examples of the monovalent alicyclic hydrocarbon groups include those having 3 to 20 carbon atoms shown in the following formula:

[0183] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0184] The divalent heteroatom-containing group is L in the above formula (1). α The divalent heteroatom-containing groups shown in the following formula can be preferably employed.

[0185] Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0186] Specific examples of the polymerizable group include, but are not limited to, structures represented by the following formulas:

[0187] (In the formula, * represents a bond on the L side.)

[0188] As the divalent linking group represented by L, a group in which one hydrogen atom has been removed from the monovalent organic group having 1 to 20 carbon atoms represented by W, or the divalent heteroatom-containing group can be suitably used.

[0189] The divalent linking group represented by L is preferably a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, a divalent chain hydrocarbon group having 1 to 10 carbon atoms, or a group formed by combining any of these groups with the above-mentioned divalent heteroatom-containing group, and some or all of the hydrogen atoms of these groups may be substituted with the above-mentioned monovalent heteroatom-containing group.

[0190] As the divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, a group in which one hydrogen atom has been removed from the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms shown above for W can be suitably used.

[0191] The divalent chain hydrocarbon group having 1 to 10 carbon atoms includes R １Ａ A group in which one hydrogen atom has been removed from a monovalent chain hydrocarbon group having 1 to 10 carbon atoms can be suitably used.

[0192] Among these, the divalent linking group represented by L is more preferably a benzenediyl group, a methylene group, an ethanediyl group, a propanediyl group, or a group formed by combining any of these groups with at least one selected from the group consisting of -O-, -CO-, and -NH-.

[0193] In the above formula (ia), A is ＊ It is preferably —CO—NH—.

[0194] R １ As the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I), the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) above can be suitably used.

[0195] In the above formula (ia), preferably, R １ represents a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or a group having —CO—, —CS—, —O—, —S—, or —SO— between carbon atoms of the aliphatic hydrocarbon group. ２-, -NR'-, or a group containing a combination of two or more of these. １ represents a substituted or unsubstituted monovalent aliphatic chain hydrocarbon group having 1 to 20 carbon atoms, or a group having —CO—, —CS—, —O—, —S—, or —SO— between carbon atoms of the aliphatic chain hydrocarbon group. ２ -, -NR'-, or a group containing a combination of two or more of these. １ is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a group containing -CO-, -O-, -S-, -NR'- or a combination of two or more of these between carbon atoms of the alkyl group. １ The alkyl group having 1 to 10 carbon atoms is preferably a branched alkyl group.

[0196] R １ When A in the formula (ia) contains an aromatic hydrocarbon group, at least one carbon atom or hetero atom is contained between A in the formula (ia) and the aromatic hydrocarbon group. In this case, a methylene group, an ethanediyl group, or a combination of these groups and -CO-, -CS-, -O-, -S-, -SO ２ It is preferred that -, -NR'- or a combination of two or more of these groups is present.

[0197] R １ The substituents of the formula (1) include R ａ The substituent is preferably a fluorine atom or a hydroxy group, more preferably a fluorine atom.

[0198] In the above formula (ia), R １ In the formula (I), the carbon atom bonded to A is preferably a tertiary carbon atom, which promotes uneven distribution of the second polymer on the resist film surface and improves the film quality modifying effect.

[0199] The compounds that provide the structural unit (i) are preferably represented by the following formulas (ia-1) to (ia-34), respectively.

[0200]

[0201]

[0202] The lower limit of the content of the structural unit (i) in all structural units constituting the second polymer (total when multiple types are included) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%, and the upper limit of the content may be 100 mol%, 98 mol%, or 96 mol%.

[0203] (Structural Unit (ii)) The structural unit (ii) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. As the structural unit (ii), the structural unit (III) in the base polymer can be suitably used. The second polymer may contain only one type of structural unit (ii), or may contain two or more types.

[0204] When the second polymer contains the structural unit (ii), the lower limit of the content of the structural unit (ii) (the total content when multiple types are contained) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on all structural units constituting the second polymer, and the upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 35 mol%.

[0205] (Structural Unit (iii)) The structural unit (iii) is a structural unit containing an alcoholic hydroxyl group. As the structural unit (iii), a structural unit having an alcoholic hydroxyl group (a structural unit not containing a phenolic hydroxyl group) among the structural units (IV) in the base polymer can be suitably used. The second polymer may contain only one type of structural unit (iii), or may contain two or more types.

[0206] When the second polymer contains the structural unit (iii), the lower limit of the content of the structural unit (iii) (the total content when multiple types are contained) is preferably 4 mol%, more preferably 8 mol%, and even more preferably 12 mol%, based on all structural units constituting the second polymer. The upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 35 mol%.

[0207] (Structural Unit (iv)) The structural unit (iv) is a structural unit containing an ammonium cation structure or a phosphonium cation structure and an acid anion. The structural unit (iv) does not have radiation sensitivity. The structural unit (iv) preferably has an intramolecular salt structure, and is more preferably represented by the following formula (B3). The second polymer may contain only one type of structural unit (iv), or may contain two or more types.

[0208] (In formula (B3), R ３１ , R ３２ and R ３３ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an alkyl group having 1 to 6 carbon atoms, or a halogenated alkyl group having 1 to 6 carbon atoms. ３１ represents a single bond, -O-, -CO-, -COO-, -NH-, -CONH- or * １ -Ar ３１ -A ３３ - is. Ar ３１ is a divalent aromatic ring group. ３３ is a single bond, —O—, —CO—, —COO—, —NH— or —CONH—. １ " is R ３３ represents the bond to the carbon atom to which it is bonded. ３１ is a single bond or E in formula (B3) ＋ is a divalent organic group having one or more carbon atoms and bonded to ＋ is a divalent group having an ammonium cation structure or a phosphonium cation structure. ３２ is E in formula (B3) ＋ and D - is a divalent organic group having one or more carbon atoms, which is bonded to each of the above via the same or different carbon atoms. - is a monovalent group having an anionic structure.

[0209] In the above formula (B3), R ３１ and R ３２ A hydrogen atom is particularly preferred as R ３３ is preferably a hydrogen atom or a methyl group.

[0210] A ３１ but*１ -Ar ３１ -A ３３ -, if Ar ３１ Examples of the divalent aromatic ring group represented by the formula (I) include a substituted or unsubstituted phenylene group.

[0211] B ３１ is E in the above formula (B3). ＋ and B is a divalent organic group having one or more carbon atoms bonded to ３２ With regard to the divalent organic group represented by the formula (I), examples of the divalent organic group include substituted or unsubstituted divalent hydrocarbon groups having 1 to 20 carbon atoms.

[0212] Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms include divalent chain hydrocarbon groups having 1 to 20 carbon atoms.

[0213] Examples of the divalent chain hydrocarbon group having 1 to 20 carbon atoms include linear or branched divalent saturated hydrocarbon groups having 1 to 20 carbon atoms.

[0214] B ３１ or B ３２ is a substituted hydrocarbon group, B ３１ or B ３２ Examples of the substituent that may be contained in the alkyl group include a halogen atom, a hydroxyl group, a cyano group, a nitro group, a halogenated alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkoxycarbonyl group having 2 to 6 carbon atoms.

[0215] In addition, B ３１ Is E ＋ "Bonded at a carbon atom" means E ＋ (More specifically, E ＋ The nitrogen atom or phosphorus atom in ３１ It indicates that the carbon atom in the ３２ Is E ＋ and D - For each of the above, "bonded at a carbon atom" means E ＋ (More specifically, E ＋ The nitrogen atom or phosphorus atom in ３２ directly bonded to a carbon atom in - is B ３２It indicates that the carbon atom in the ＋ B binds to ３１ Carbon atom in E ＋ B binds to ３２ Carbon atoms in and D - B binds to ３２ The carbon atoms in B may be primary, secondary or tertiary carbon atoms. ３１ or B ３２ It may be adjacent to an oxygen atom or a heteroatom-containing group such as a carbonyl group.

[0216] E ＋ is a divalent group having an ammonium cation structure or a phosphonium cation structure. ＋ Preferred specific examples of the divalent group represented by the formula (e-1), (e-2) or (e-3) below include structures represented by the formula (e-1), (e-2) or (e-3) below.

[0217] (In formula (e-1), formula (e-2) and formula (e-3), R ３６ and R ３７ are each independently a monovalent hydrocarbon group, or R ３６ and R ３７ and are combined together to form R ３６ and R ３７ represents an aliphatic heterocyclic structure formed together with the nitrogen atom to which R is bonded. ３８ and R ３９ are each independently a monovalent hydrocarbon group, or R ３８ and R ３９ and are combined together to form R ３８ and R ３９ represents a ring structure formed together with the phosphorus atom to which it is bonded. "*" represents a bond.)

[0218] In the above formulas (e-1) to (e-3), R ３６ , R ３７ , R ３８ or R ３９ Examples of the monovalent hydrocarbon group represented by the formula (I) include monovalent chain hydrocarbon groups having 1 to 10 carbon atoms.

[0219] As the monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms is preferred.

[0220] R ３６ and R ３７ are aligned with each other and R ３６ and R ３７ Examples of the aliphatic heterocyclic structure formed together with the nitrogen atom to which R is bonded include groups in which a hydrogen atom has been removed from a nitrogen atom constituting a nitrogen-containing aliphatic heterocyclic ring (for example, a piperidine ring). ３８ and R ３９ are aligned with each other and R ３８ and R ３９ Examples of the ring structure formed together with the phosphorus atom to which is bonded include groups formed by removing a hydrogen atom from a phosphorus atom constituting a phosphorus-containing heterocycle (e.g., a phosphinane ring, a phosphole ring, etc.). The nitrogen-containing aliphatic heterocyclic structure and the phosphorus-containing heterocyclic structure may each have a substituent such as an alkyl group in the ring.

[0221] E ＋ The divalent group represented by the formula (e-1) preferably has an ammonium cation structure, and among these, a group represented by the formula (e-1) or (e-2) above is preferred.

[0222] D - is a monovalent group having an anionic structure. - A specific example of this is "-COO - ", "-SO ３ - ", "-PO ３ - "," -POO - " or "-O - " are cited as examples.

[0223] Preferred specific examples of the structural unit (iv) include structural units represented by the following formula (B3-1) or formula (B3-2). (In formula (B3-1) and formula (B3-2), R ３１ , R ３２ , R ３３ , R ３６ , R ３７ , A ３１ , B ３１ and B ３２are the same as those in formula (B3) above.

[0224] Specific examples of the structural unit (iv) include structural units represented by the following formula:

[0225] (In the formula, R Ｂ is a hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an alkyl group having 1 to 6 carbon atoms, or a halogenated alkyl group having 1 to 6 carbon atoms.

[0226] When the second polymer contains the structural unit (iv), the lower limit of the content of the structural unit (iv) (the total content when multiple types are contained) is preferably 4 mol%, more preferably 8 mol%, and even more preferably 12 mol%, based on all structural units constituting the second polymer. The upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 35 mol%.

[0227] (Structural Unit (v)) The structural unit (v) is a structural unit containing a fluorine atom, different from the structural unit (i). The structural unit (v) is preferably represented by the following formula (E). (In the above formula (E), R Ｋ１ is a hydrogen atom, a fluorine atom, a methyl group, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. Ｅ is -COO- ＊ or -Ar Ｅ -COO- ＊ Ar Ｅ is a divalent aromatic ring. * is L Ｙ１ It is a bond on the side. Ｙ１ is a divalent hydrocarbon group having 1 to 10 carbon atoms or a divalent group having a lactone structure. Ｙ２ is -COO- ＊ or -OCO- ＊ is. ＊ is R ｆ１ It is a bond on the R side. ｆ１ is a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms. ｆ２ and R ｆ３are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms. ｆ２ and R ｆ３ If there are multiple R ｆ２ and R ｆ３ are the same or different, and s is an integer of 0 to 3. ｆ１ is a monovalent hydrocarbon group having 1 to 10 carbon atoms, s is an integer of 1 to 3, and ep is 0 or 1. However, when ep is 0, R ｆ１ is a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms.

[0228] R Ｋ１ The alkyl group having 1 to 6 carbon atoms represented by the formula (1) is ａ An alkyl group having 1 to 6 carbon atoms can be preferably used.

[0229] R Ｋ１ When the alkyl group having 1 to 6 carbon atoms represented by the formula (1) has a substituent, the substituent is preferably R ａ The substituents that may be possessed by the group may be suitably employed.

[0230] Ar Ｅ As the divalent aromatic ring represented by the formula (I), a group in which two hydrogen atoms have been removed from the aromatic ring shown in the iodo group-containing aromatic ring structure can be suitably used. Ｅ The divalent aromatic ring represented by the formula (I) is preferably a benzenediyl group.

[0231] L Ｙ１ As the divalent hydrocarbon group having 1 to 10 carbon atoms represented by the formula (1), α Among the divalent hydrocarbon groups, alkanediyl groups, cycloalkanediyl groups, alkenediyl groups, and arenediyl groups, which are exemplified as divalent linking groups represented by the formula (I), groups having 1 to 10 carbon atoms can be mentioned. Ｙ１ As the divalent hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I), a methylene group, an ethanediyl group, or a propanediyl group is preferred.

[0232] L Ｙ１Preferred examples of the divalent group having a lactone structure represented by the formula (I) include a γ-butyrolactonediyl group, a norbornanelactonediyl group, and an adamantanelactonediyl group.

[0233] L Ｙ２ is -COO- ＊ It is preferable that:

[0234] R ｆ１ Examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms represented by the formula (ia) include the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by W in the formula (ia) above, which correspond to the groups having 1 to 10 carbon atoms. ｆ１ As the monovalent hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I), a methyl group, an ethyl group, or a propyl group is preferred.

[0235] R ｆ１ , R ｆ２ and R ｆ３ Examples of the monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include fluorinated alkyl groups such as a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a pentafluoroethyl group, a 3,3,3-trifluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1-trifluoropropan-2-yl group, a 1,1,1,3,3,3-hexafluoropropan-2-yl group, a heptafluoro-n-propyl group, a heptafluoroisopropyl group, a 1,1,1-trifluoro-2-methyl-propan-2-yl group, a nonafluoro-n-butyl group, a nonafluoroisobutyl group, a nonafluoro-t-butyl group, a 2,2,3,3,4,4,5,5-octafluoro-n-pentyl group, a tridecafluoro-n-hexyl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group; Fluorinated alkenyl groups such as trifluoroethenyl and pentafluoropropenyl; and fluorinated alkynyl groups such as fluoroethynyl and trifluoropropynyl.

[0236] Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 10 carbon atoms include fluorinated cycloalkyl groups such as a fluorocyclopentyl group, a difluorocyclopentyl group, a nonafluorocyclopentyl group, a fluorocyclohexyl group, a difluorocyclohexyl group, an undecafluorocyclohexylmethyl group, a fluoronorbornyl group, and a fluoroadamantyl group; and fluorinated cycloalkenyl groups such as a fluorocyclopentenyl group and a nonafluorocyclohexenyl group.

[0237] R ｆ１ , R ｆ２ and R ｆ３ The monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) is preferably a monovalent fluorinated chain hydrocarbon group having 1 to 10 carbon atoms, more preferably a monovalent fluorinated chain hydrocarbon group having 1 to 6 carbon atoms, and even more preferably a monovalent fluorinated chain saturated hydrocarbon group having 1 to 4 carbon atoms.

[0238] s is preferably an integer of 0 to 2, and more preferably 0 or 1.

[0239] In the above formula (E), R ｆ１ is a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms, and s is preferably 0.

[0240] The monomers that give the structural unit (v) are preferably represented by the following formulas (E-1) to (E-12), respectively. Ｋ１ has the same meaning as formula (E) above.

[0241]

[0242] When the second polymer contains the structural unit (v), the lower limit of the content of the structural unit (v) (the total content when multiple types are contained) relative to all structural units constituting the second polymer is preferably 4 mol%, more preferably 8 mol%, and even more preferably 12 mol%. The upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 35 mol%. By setting the content of the structural unit (v) within the above range, the surface uneven distribution of the second polymer and the solubility of the surface layer of the resist film can be improved.

[0243] The upper limit of the Mw of the second polymer is usually 30,000, preferably 20,000, more preferably 18,000, and even more preferably 16,000. The lower limit of the Mw is preferably 2,000, more preferably 3,000, and even more preferably 3,500. By setting the Mw of the second polymer within the above range, the solubility, mobility, and glass transition temperature of the second polymer can be controlled within appropriate ranges.

[0244] The lower limit of Mw / Mn of the second polymer is usually 1, and more preferably 1.1. The upper limit of Mw / Mn is usually 5, and preferably 3, and more preferably 2.

[0245] The lower limit of the content of the second polymer is preferably 0.01 parts by mass, more preferably 0.1 parts by mass, and even more preferably 1 part by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 20 parts by mass, more preferably 15 parts by mass, and even more preferably 12 parts by mass. By setting the content of the second polymer within the above range, the second polymer can be more effectively localized in the surface layer of the resist film, thereby improving the solubility of the surface layer of the resist film during development and enabling control of the surface modification of the resist film and the distribution of the composition within the film during EUV exposure. The radiation-sensitive composition may contain one or more types of second polymer.

[0246] (Method of Synthesizing Second Polymer) The second polymer can be synthesized by the same method as the method of synthesizing the base polymer described above.

[0247] <Radiation-Sensitive Acid Generator> The radiation-sensitive composition may contain a radiation-sensitive acid generator. The radiation-sensitive acid generator contains a third organic acid anion and a third onium cation to form an onium salt structure. The radiation-sensitive acid generator is a component that generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer to generate a carboxyl group or the like. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low-molecular-weight compound (free from the polymer), and is different from the radiation-sensitive acid-generating structure in which the first organic acid anion or the first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure, such as the structural unit (V) in the base polymer.

[0248] At least one selected from the group consisting of the third organic acid anion and the third onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0249] The structure of the third organic acid anion of the radiation-sensitive acid generator is V in the above formula (a1) of the base polymer. ２ From SO ３ - In addition to the above structure, any conventionally known structure can be suitably adopted.

[0250] Examples of the third organic acid anion of the radiation-sensitive acid generator include, but are not limited to, those shown below. Note that, instead of the first organic acid anion having an iodo group-containing aromatic ring structure, a third organic acid anion not having an iodo group-containing aromatic ring structure can suitably be a structure in which the iodo group in the following formula is substituted with a hydrogen atom or another substituent.

[0251]

[0252]

[0253]

[0254]

[0255] The structure of the third onium cation in the radiation-sensitive acid generator can suitably be the same as the structure of the first onium cation in the structural unit (V) in the base polymer.

[0256] The above-mentioned radiation-sensitive acid generator can be synthesized by a known method, particularly by a salt exchange reaction. Known radiation-sensitive acid generators can also be used as long as they do not impair the effects of the present invention.

[0257] These radiation-sensitive acid generators may be used alone or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total content when multiple types are used) is preferably 1 part by mass, more preferably 2 parts by mass, and even more preferably 3 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the content is preferably 100 parts by mass, more preferably 60 parts by mass, and even more preferably 40 parts by mass. This allows excellent sensitivity to be exhibited during resist pattern formation.

[0258] <Acid Diffusion Controller> The radiation-sensitive composition may contain an acid diffusion controller. The acid diffusion controller contains a quaternary organic acid anion and a quaternary onium cation, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The acid diffusion controller does not substantially dissociate the acid-dissociable group of the base polymer under pattern formation conditions using the radiation-sensitive composition, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas through salt exchange.

[0259] By including the acid diffusion controller in the radiation-sensitive composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern that is superior in CDU and development contrast.

[0260] At least one selected from the group consisting of the quaternary organic acid anion and the quaternary onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0261] The structure of the fourth organic acid anion is not particularly limited, but preferably includes -O-, -CO-, a cyclic structure, or a combination thereof. As the cyclic structure, the cyclic structure in the first organic acid anion of the structural unit (V) of the base polymer can be suitably used.

[0262] In the acid diffusion controller, the fourth organic acid anion preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety (provided that, when the fourth organic acid anion has the sulfonate anion, neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfur atom of the sulfonate anion), which allows the acid diffusion controller to efficiently exhibit the above-mentioned function.

[0263] Examples of the acid diffusion controller include a sulfonium salt compound represented by the following formula (8-1), an iodonium salt compound represented by the following formula (8-2), etc. Further examples include a compound containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and a compound containing an iodonium cation and an anion in the same molecule represented by the following formula (8-4).

[0264]

[0265] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. - and Q - are each independently OH - , R α -COO - , R α -SO ３ - In the above formulas (8-1) and (8-2), R α is a monovalent organic group having 1 to 30 carbon atoms. αis a single bond or a divalent organic group having 1 to 30 carbon atoms. As the monovalent organic group having 1 to 30 carbon atoms, a group obtained by extending the monovalent organic group having 1 to 20 carbon atoms represented by W in formula (ia) to have 1 to 30 carbon atoms can be suitably used. As the divalent organic group having 1 to 30 carbon atoms, a group obtained by removing one hydrogen atom from the monovalent organic group having 1 to 30 carbon atoms can be suitably used.

[0266] Examples of the fourth organic acid anion of the acid diffusion controller include, but are not limited to, those shown below. Examples also include compounds containing an iodonium cation and an anion in the same molecule and compounds containing a sulfonium cation and anion in the same molecule. As the organic acid anion without an iodo group-containing aromatic ring structure, a structure in which the iodo group in the following formula is substituted with an atom or group other than the iodo group, such as a hydrogen atom or another substituent, can be suitably used.

[0267]

[0268]

[0269] As the quaternary onium cation in the acid diffusion controller, the structure of the first onium cation in the structural unit (V) in the base polymer can be suitably adopted.

[0270] The acid diffusion controller can also be synthesized by known methods, particularly by salt exchange reaction.

[0271] These acid diffusion controllers may be used alone or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion controller, the lower limit of the content of the acid diffusion controller (total content when multiple types are used) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, based on the total amount of the monomer that provides the structural unit (V) of the base polymer and the radiation-sensitive acid generator (when both are included). The upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 30 mol%.

[0272] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the base polymer and optional additives.

[0273] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0274] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-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 propylene glycol 1-monomethyl ether. In this 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.

[0275] 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.

[0276] 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.

[0277] 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.

[0278] 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.

[0279] 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.

[0280] Among these, alcohol-based solvents, ester-based solvents, and ether-based solvents are preferred, with monoalcohol-based solvents having 1 to 18 carbon atoms, polyhydric alcohol partial ether acetate solvents, and polyhydric alcohol partial ether solvents being more preferred, and diacetone alcohol, propylene glycol monomethyl ether acetate, and propylene glycol monomethyl ether being even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0281] <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.

[0282] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer, a second polymer, a solvent, and, if necessary, other optional components in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0283] <<Pattern Forming Method>> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0284] According to the pattern formation method, the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity, CDU, suppression of development defects, and film thickness uniformity during pattern formation, and therefore a high-quality resist pattern can be formed. Each step will be described below.

[0285] [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, soft baking (SB) may be performed, if necessary, to volatilize the solvent in the coating film. The SB temperature is typically 60°C to 160°C, preferably 80°C to 140°C. The SB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0286] When the subsequent exposure step is carried out using radiation with a wavelength of 50 nm or less, it is preferable to use a polymer having the structural unit (II) as the base polymer in the composition.

[0287] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is irradiated with radiation through a photomask to expose it. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0288] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0289] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0290] In the case of alkaline development, the developer used in the development may be, for example, 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, or 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.

[0291] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0292] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0293] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0294] [Measurement of Weight Average Molecular Weight (Mw), Number Average Molecular Weight (Mn), and Dispersity (Mw / Mn)] Measurements were performed by gel permeation chromatography (GPC) using Tosoh GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL") under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, and column temperature: 40°C, with monodisperse polystyrene as the standard.

[0295] [ １ H-NMR analysis and １３ C-NMR Analysis] Measurement was carried out using a JEOL "JNM-Delta400".

[0296] <Synthesis of Polymer> The monomers used in the synthesis of each polymer in each Example and Comparative Example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refer to a value when the total mass of the monomers used is 100 parts by mass, and mol % refers to a value when the total number of moles of the monomers used is 100 mol %. Furthermore, the present invention is not limited to the following structural units.

[0297] Among the monomers used in the synthesis of the polymers in each example, the structure of the monomer represented by formula (ia) is shown below.

[0298]

[0299] Among the monomers used in the synthesis of the polymers in each Example and Comparative Example, the structures of the monomers other than those mentioned above are shown below.

[0300]

[0301]

[0302]

[0303]

[0304]

[0305]

[0306]

[0307] Polymer (A) Synthesis Example 1: Synthesis of Polymer (A-1) as Second Polymer Compound (G-1) and compound (M-31) were dissolved in 2-butanone (200 parts by mass relative to the total monomer amount) so that the molar ratio in the final polymer was 70 / 30. Azobisisobutyronitrile (AIBN) was added as an initiator in an amount of 4 mol % relative to the total monomer amount to prepare a monomer solution. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel and heated to 80°C with stirring. The monomer solution prepared above was then added dropwise over 3 hours. The mixture was then heated at 80°C for another 3 hours. After the polymerization reaction was completed, the polymerization solution was cooled to room temperature. Acetonitrile (100 parts by mass) and hexane (600 parts by mass) were added to the resulting polymerization solution and stirred. The lower layer was recovered, and the solvent was removed to obtain Polymer (A-1). The Mw and Mw / Mn of the resulting polymer are shown in Table 1-1.

[0308] [Polymer (A) Synthesis Examples 2 to 64, Comparative Synthesis Examples 1 to 4] Synthesis of Polymers (A-2) to (A-68) Polymers (A-2) to (A-68) were obtained in the same manner as in Polymer (A) Synthesis Example 1, except that the types and amounts of monomers shown in Tables 1-1 and 1-2 were blended in the specified amounts. The Mw and Mw / Mn of each of the obtained polymers are shown in Tables 1-1 and 1-2.

[0309]

[0310]

[0311] [Polymer (P) Synthesis Example P1] Synthesis of Polymer (P-1) as First Polymer Compound (M-1) and compound (M-12) were dissolved in methanol (200 parts by mass relative to the total monomer amount) so that the molar ratio in the final polymer was 40 / 60. Next, 8 mol% of AIBN was added as an initiator relative to the total monomer amount to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass relative to the total monomer amount) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85°C for another 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. The cooled polymerization solution was added to hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane relative to the polymerization solution, and then redissolved in 1-methoxy-2-propanol (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70°C for 6 hours while stirring. After completion of the reaction, the remaining solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass). The resin was coagulated by dropping it into 500 parts by mass of water, and the resulting solid was filtered off. The resulting mixture was dried at 50°C for 12 hours to synthesize a white powdery polymer (P-1). The Mw and Mw / Mn of the resulting polymer are shown in Table 2-1.

[0312] [Polymer (P) Synthesis Examples P2 to P14, P17 to P42] Synthesis of Polymers (P-2) to (P-14) and (P-17) to (P-42) Polymers (P-2) to (P-14) and (P-17) to (P-42) were obtained in the same manner as in Polymer (P) Synthesis Example P1, except that the types and amounts of monomers shown in Tables 2-1 and 2-2 were blended in the specified amounts. The Mw and Mw / Mn of each obtained polymer are shown in Tables 2-1 and 2-2.

[0313] [Polymer (P) Synthesis Example P15] Synthesis of Polymer (P-15) Compounds (M-10) and (M-12) were dissolved in 2-butanone (200 parts by mass relative to the total monomer amount) so that the molar ratio in the final polymer was 40 / 60. Azobisisobutyronitrile (AIBN) was added as an initiator in an amount of 8 mol% relative to the total monomer amount to prepare a monomer solution. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel and heated to 80°C with stirring. The monomer solution prepared above was then added dropwise over 3 hours. The mixture was then heated at 80°C for another 3 hours. After the polymerization reaction was completed, the polymerization solution was cooled to room temperature. Acetonitrile (100 parts by mass) and hexane (600 parts by mass) were added to the resulting polymerization solution and stirred. The lower layer was recovered, and the solvent was removed to obtain Polymer (P-15). The Mw and Mw / Mn of the resulting polymer are shown in Table 2-1.

[0314] [Polymer (P) Synthesis Examples P16, P43 to P59] Synthesis of Polymers (P-16), (P-43) to (P-59) Polymers (P-16), (P-43) to (P-59) were obtained in the same manner as in Polymer (P) Synthesis Example P15, except that the types and amounts of monomers shown in Tables 2-1 and 2-2 were blended in the specified amounts. The Mw and Mw / Mn of each obtained polymer are shown in Tables 2-1 and 2-2.

[0315]

[0316]

[0317] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator, acid diffusion controller, and solvent that constitute the radiation-sensitive composition are described below.

[0318] [Radiation-sensitive acid generators] B-1 to B-14: Compounds represented by the following formulas (B-1) to (B-14).

[0319]

[0320]

[0321] [Acid Diffusion Controller] D-1 to D-9: Compounds represented by the following formulas (D-1) to (D-9): The amount of the acid diffusion controller is expressed as a molar ratio relative to the monomer compound that provides the structural unit (V) of the first polymer and the radiation-sensitive acid generator (if both are included).

[0322]

[0323] [Solvent] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol 1-monomethyl ether E-3: Diacetone alcohol

[0324] [Example 1] 0.1 parts by mass of the second polymer (A-1), 100 parts by mass of the first polymer (P-1), 20 parts by mass of the radiation-sensitive acid generator (B-1), 20 mol% of the acid diffusion controller (D-1) relative to (B-1), 2,800 parts by mass of the solvent (E-1), 2,000 parts by mass of (E-2), and 2,000 parts by mass of (E-3) were blended and mixed. Next, the resulting mixture was filtered through a membrane filter with a pore size of 0.20 μm to prepare a radiation-sensitive composition (R-1).

[0325] [Examples 2 to 148 and Comparative Examples 1 to 5] Radiation-sensitive compositions (R-2) to (R-148) and (CR-1) to (CR-5) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 3-1, 3-2, and 3-3 below were used.

[0326]

[0327]

[0328]

[0329] <Formation of Resist Pattern> (EUV Exposure, Alkali Development) The radiation-sensitive composition prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). A soft bake (SB) was performed at 130°C for 60 seconds, followed by cooling at 23°C for 30 seconds to form a 50-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300," ASML, NA = 0.33, illumination conditions: Conventional s = 0.89, mask imecDEFECT32FFR02). Next, PEB was performed on a hot plate at 100°C for 60 seconds, and development was performed using a 2.38 wt% TMAH aqueous solution at 23°C for 30 seconds to form a resist pattern with 25 nm holes and a 50 nm pitch (hereinafter also referred to as a "25 nm contact hole pattern").

[0330] <Evaluation> The resist patterns formed as described above were measured according to the following methods to evaluate the sensitivity, CDU, number of development defects, and film thickness uniformity of each radiation-sensitive composition. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-4100") was used to measure the resist patterns. The evaluation results are shown in Tables 4-1, 4-2, and 4-3 below.

[0331] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 25 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The sensitivity was 25 mJ / cm ２ If it is less than 25 mJ / cm, it is "A" (very good), and if it is less than 25 mJ / cm, it is "B" (very good). ２ 27.5mJ / cm or more ２ If it is less than 27.5 mJ / cm, it is "B" (good). ２ 30mJ / cm or more ２ The following cases are classified as "C" (fairly good), 30 mJ / cm ２ When the test result exceeded this, the test result was judged to be "D" (poor).

[0332] [CDU] A 25 nm contact hole pattern was formed in the same manner as described above, using the optimal exposure dose determined in the [Sensitivity] section above. The formed resist pattern was observed from above using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), and a total of 800 hole diameters were measured at random points. The dimensional variation (3σ) was determined and this was taken as CDU (nm). A smaller CDU value indicates a smaller and better long-period variation in hole diameter. CDU was evaluated as "A" (very good) for values ​​less than 3.6 nm, "B" (good) for values ​​3.6 nm to 3.8 nm, and "C" (poor) for values ​​3.8 nm or greater.

[0333] [Number of Development Defects] The number of defects on the wafer for the 25 nm contact hole pattern formed above was measured using a defect inspection device (KLA-Tencor's "KLA2925"). Among the defects measured, defects with a diameter of 0.5 μm or less were determined to be originating from the resist film. The number of development defects determined to be originating from the resist film was evaluated as "A" (very good) when the number of defects was less than 40, "B" (good) when the number was 40 or more but less than 70, "C" (fair) when the number was 70 or more but less than 100, and "D" (bad) when the number was more than 100.

[0334] [Thickness uniformity] Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron). After soft baking (SB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a resist film with a thickness of 45 nm. Next, using an optical interference film thickness measuring device VM-3210 (manufactured by SCREEN), the film thickness was measured at 21 points at 1-centimeter intervals from the center of the wafer to a radius of 10 centimeters in the vertical direction, and the variation (3σ) of the measured values ​​was determined to represent the film thickness uniformity. Film thickness uniformity was evaluated as "A" (very good) when it was less than 0.5 nm, "B" (good) when it was 0.5 nm or more but less than 1.0 nm, "C" (fairly good) when it was 1.0 nm or more but less than 1.5 nm, and "D" (poor) when it was 1.5 nm or more.

[0335]

[0336]

[0337]

[0338] As is clear from the results in Tables 4-1, 4-2 and 4-3, the radiation-sensitive compositions of the Examples all had better sensitivity, CDU, development defect suppression and film thickness uniformity than the radiation-sensitive compositions of the Comparative Examples.

[0339] The radiation-sensitive composition and pattern formation method of the present invention can improve sensitivity, CDU, suppression of development defects, and film thickness uniformity during pattern formation, and are therefore suitable for use in forming fine resist patterns in lithography processes for various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

a first polymer having a structural unit (I) containing an acid-dissociable group; a second polymer different from the first polymer; Solvent and Including, The second polymer has a structural unit (i) derived from a compound represented by the following formula (ia): Radiosensitive linear components. (In formula (ia), W is a polymerizable group. L is a single bond or a divalent linking group. A is, ＊ —CO—NH— or ＊ It is -NH-CO-. * indicates a bond on the W side. R １ represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having —CO—, —CS—, —O—, —S—, or —SO— between carbon atoms of the hydrocarbon group. ２ -, -NR'-, or a group containing a combination of two or more of these. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. １ When A in formula (ia) contains an aromatic hydrocarbon group, it contains at least one carbon atom or hetero atom between A in formula (ia) and the aromatic hydrocarbon group. In the above formula (ia), R １ represents a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or a group having —CO—, —CS—, —O—, —S—, or —SO— between carbon atoms of the aliphatic hydrocarbon group. ２ 2. The radiation-sensitive composition according to claim 1, wherein the group is -, -NR'-, or a group containing a combination of two or more of these. 　 In the above formula (ia), R １ represents a substituted or unsubstituted monovalent aliphatic chain hydrocarbon group having 1 to 20 carbon atoms, or a group having —CO—, —CS—, —O—, —S—, or —SO— between carbon atoms of the aliphatic chain hydrocarbon group. ２ 2. The radiation-sensitive composition according to claim 1, wherein the group is -, -NR'-, or a group containing a combination of two or more of these. 　 In the above formula (ia), A is ＊ The radiation-sensitive composition according to claim 1 , wherein the alkyl group is —CO—NH—. 　 In the above formula (ia), R １ 5. The radiation-sensitive composition according to claim 1, wherein the carbon atom bonded to A in the formula (I) is a tertiary carbon atom.

5. The radiation-sensitive composition according to claim 1, wherein the second polymer has a weight average molecular weight of 20,000 or less in terms of polystyrene. 　 The second polymer contains, as a structural unit other than the structural unit (i), a structural unit (ii) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure; a structural unit (iii) containing an alcoholic hydroxyl group; A structural unit (iv) containing an ammonium cation structure or a phosphonium cation structure and an acid anion, and Structural unit (v) containing a fluorine atom The radiation-sensitive composition according to any one of claims 1 to 4, further comprising at least one selected from the group consisting of:

5. The radiation-sensitive composition according to claim 1, wherein the structural unit (i) accounts for 20 mol % or more and 100 mol % or less of all structural units constituting the second polymer.

5. The radiation-sensitive composition according to claim 1, wherein the content of the second polymer is 0.1 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the first polymer.

5. The radiation-sensitive composition according to claim 1, wherein the first polymer has a structural unit containing a phenolic hydroxyl group. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein the first polymer contains an iodine group. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein the structural unit (I) is represented by the following formula (1): (In formula (1), R ａ is a hydrogen atom, a fluorine atom, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. L α is a divalent linking group. R １Ａ and R １Ｂ are each independently a hydrogen atom, a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, 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. １Ａ and R １Ｂ There is no case where both are hydrogen atoms. Ar １ａ is a (p+q+1)-valent aromatic ring having 5 to 20 ring members. R １０１ is a nitro group, a cyano group, a hydroxy group, an alkoxy group, or an amino group. １０１ If there are multiple R １０１ are the same or different from each other. 　 m1 and m2 each independently represent 0 or 1, provided that when m1 is 1, m2 is 1. p is an integer from 1 to 3, and q is an integer from 0 to 3, provided that p+q is 5 or less. 　 The radiation-sensitive composition according to any one of claims 1 to 4, further comprising a radiation-sensitive acid generator. 　 The radiation-sensitive composition according to any one of claims 1 to 4, further comprising an acid diffusion controller. 　 The radiation-sensitive composition according to any one of claims 1 to 4, which is for exposure to ArF excimer laser light or extreme ultraviolet light. 　 a step of directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 4 to a substrate to form a resist film; exposing the resist film to light; developing the exposed resist film with a developer; A pattern forming method comprising:

17. The pattern forming method according to claim 16, wherein the exposure is carried out with ArF excimer laser light or extreme ultraviolet light.

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