Resist composition and patterning process

Abstract

To provide a non-chemically amplified resist composition excellent in sensitivity and limiting resolution in photolithography using a high energy beam, and a pattern forming method using the resist composition.SOLUTION: The resist composition comprises a polymer containing a repeating unit having a hypervalent iodine structure represented by formula (1), a carboxy group-containing compound, and a solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resist composition and a pattern forming method. [Background technology]

[0002] As the IoT market expands, there is a growing demand for higher integration, higher speeds, and lower power consumption in LSIs, leading to rapid progress in miniaturization of pattern rules. Logic devices, in particular, are driving this miniaturization. The most advanced miniaturization technology is ArF immersion lithography, with double patterning, triple patterning, and quadruple patterning being used to mass-produce 10nm-node devices. Furthermore, studies are underway to develop 7nm-node devices using next-generation extreme ultraviolet (EUV) lithography with a wavelength of 13.5nm.

[0003] As miniaturization progresses, image blurring due to acid diffusion has become a problem (Non-Patent Document 1). It has been suggested that in order to ensure resolution in fine patterns with processing dimensions of 45 nm and below, not only is it important to improve dissolution contrast, as has been proposed in the past, but also to control acid diffusion (Non-Patent Document 2). However, because chemically amplified resist compositions increase sensitivity and contrast through acid diffusion, attempts to minimize acid diffusion by lowering the post-exposure bake (PEB) temperature or shortening the PEB time result in significant decreases in sensitivity and contrast.

[0004] Adding an acid generator that generates bulky acid is effective in suppressing acid diffusion. Therefore, copolymerization of an onium salt acid generator with a polymerizable olefin into a polymer has been proposed. However, for resist film pattern formation with feature sizes of 16 nm or less, it is believed that chemically amplified resist compositions cannot be used to form patterns due to acid diffusion, and the development of non-chemically amplified resist compositions is desired.

[0005] One material for non-chemically amplified resist compositions is polymethyl methacrylate (PMMA), a positive resist material whose main chain is cleaved by EUV irradiation, resulting in a decrease in molecular weight, which improves its solubility in organic solvent developers.

[0006] Hydrogen silsesquioxane (HSQ) is a negative resist material that becomes insoluble in alkaline developers due to crosslinking caused by the condensation reaction of silanols generated by EUV irradiation. Chlorine-substituted calixarenes also function as negative resist materials. These negative resist materials have small molecular size before crosslinking and are free of blurring due to acid diffusion, resulting in low edge roughness and extremely high resolution, and are used as pattern transfer materials to indicate the resolution limit of exposure equipment. However, these materials have insufficient sensitivity, and further improvement is needed.

[0007] One of the challenges in developing materials for EUV lithography is the low photon count in EUV exposure. EUV energy is much higher than that of ArF excimer laser light, and the photon count in EUV exposure is one-fourteenth that of ArF exposure. Furthermore, the pattern dimensions formed with EUV exposure are less than half those of ArF exposure. This makes EUV exposure susceptible to variations in photon count. The variations in photon count in the extremely short wavelength radiation region are a physical phenomenon known as shot noise, and this effect cannot be eliminated. Therefore, so-called stochastics has attracted attention. While the effects of shot noise cannot be eliminated, methods for reducing this effect are being discussed. Shot noise not only increases dimensional uniformity (CDU) and line width roughness (LWR), but also causes hole blockage with a probability of one in several million. Blocked holes cause poor electrical conduction, preventing transistor operation and adversely affecting overall device performance. When considering practical sensitivity, resist compositions containing PMMA or HSQ as the main component are significantly affected by stochastics and are unable to achieve the desired resolution performance.

[0008] As a method for reducing the impact of shot noise on the resist side, the introduction of elements that have high absorption of EUV light has attracted attention. Patent Document 1 proposes a chemically amplified resist composition containing iodine atoms that have high absorption of EUV light. However, as mentioned above, chemically amplified resist compositions cannot achieve excellent resolution performance in EUV lithography, where processing dimensions will become increasingly finer in the future. In particular, in line and space patterns, as pattern dimensions become smaller, pattern collapse and line breakage increase significantly, and reducing these occurrences leads to an improvement in limiting resolution.

[0009] Patent Document 2 proposes a negative resist composition using a tin compound. Because this composition contains tin, which has high absorption of EUV light, as its main component, it has improved stochastics and can achieve high sensitivity and high resolution. However, so-called metal resists of this type have many issues, such as insufficient solubility in resist solvents, storage stability, and defects due to post-etching residues. Furthermore, since metal resists are negative resists in which the exposed areas become insoluble in developer solutions by primarily becoming metal oxides, applying them to contact hole patterning requires an additional reversal process, which raises cost concerns. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2018-5224 [Patent Document 2] Special Publication No. 2021-503482 [Non-patent literature]

[0011] [Non-Patent Document 1] SPIE Vol. 5039 p1 (2003) [Non-patent document 2] SPIE Vol. 6520 p65203L-1 (2007) Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-chemically amplified resist composition that exhibits excellent sensitivity and limiting resolution in photolithography using high-energy rays, particularly electron beam (EB) lithography and EUV lithography, and a pattern formation method that uses the resist composition. [Means for solving the problem]

[0013] As a result of extensive research into achieving the above-mentioned object, the inventors of the present invention discovered that a resist composition containing as its main components a polymer having a specific hypervalent iodine structure and a carboxy group-containing compound provides a resist film that exhibits excellent resolution and is extremely effective for precise microfabrication, which led to the completion of the present invention.

[0014] That is, the present invention provides the following resist composition and pattern forming method. 1. A resist composition comprising a polymer containing a repeating unit having a hypervalent iodine structure represented by the following formula (1), a carboxy group-containing compound, and a solvent: [ka] (In the formula, m is 0 or 1. When m is 0, n is 0, 1, 2, 3, or 4, and when m is 1, n is 0, 1, 2, 3, 4, 5, or 6. R A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group. R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms. R 3is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. 2. The resist composition of 1, wherein the carboxy group-containing compound is a polymer containing a repeating unit represented by the following formula (2) or a compound represented by the following formula (3). [ka] (In the formula, R A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group. X A is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX A1 -X A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * represents a bond to a carbon atom in the main chain. k is 1, 2, 3 or 4. R 11 is a k-valent hydrocarbon group having 1 to 40 carbon atoms or a k-valent heterocyclic group having 2 to 40 carbon atoms, and when k is 2, R 11 may be an ether bond, a carbonyl group, an azo group, a thioether bond, a carbonate bond, a carbamate bond, a sulfinyl group, or a sulfonyl group. Some or all of the hydrogen atoms in the k-valent hydrocarbon group or k-valent heterocyclic group may be substituted with a group containing a heteroatom, and some of the -CH2- groups in the k-valent hydrocarbon group may be substituted with a group containing a heteroatom. R 12 is a single bond or a hydrocarbylene group having 1 to 10 carbon atoms, and some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a hetero atom, or some of the -CH2- of the hydrocarbylene group may be substituted with a group containing a hetero atom. When k is 2, 3, or 4, each R 12 may be the same as or different from each other.) 3. A laminate comprising a substrate and a resist film obtained from the resist composition 1 or 2 on the substrate. 4. The laminate of 3, comprising an underlayer film between the substrate and the resist film. 5. The laminate of 3 or 4, wherein the resist film is formed by ligand exchange between the hypervalent iodine compound and a carboxy group-containing compound. 6. A pattern forming method comprising the steps of: forming a resist film on a substrate, or on an underlayer film of a substrate laminated with an underlayer film, using the resist composition of 1 or 2; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer. [Effects of the Invention]

[0015] The resist composition of the present invention is extremely useful for achieving both high sensitivity and high resolution and for forming fine patterns, particularly in photolithography using i-line, KrF excimer laser light, ArF excimer laser light, EB, or EUV. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Resist composition] The resist composition of the present invention contains, as main components, a polymer having a predetermined hypervalent iodine structure (hereinafter also referred to as a hypervalent iodine-containing polymer) and a carboxy group-containing compound.

[0017] [Hypervalent iodine-containing polymers] The hypervalent iodine-containing polymer contains a repeating unit having a hypervalent iodine structure represented by the following formula (1). [ka]

[0018] In formula (1), m is 0 or 1. When m is 0, n is 0, 1, 2, 3, or 4, and when m is 1, n is 0, 1, 2, 3, 4, 5, or 6.

[0019] In formula (1), R A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group.

[0020] In formula (1), R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms.

[0021] R 1 and R 2 Specific examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0022] R 1 and R 2 The hydrocarbyl group having 1 to 10 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, and a tricyclo[5.2.1.0] 2,6] cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as a decanyl group or an adamantyl group; alkenyl groups having 2 to 10 carbon atoms, such as a vinyl group or a 2-propenyl group; aryl groups having 6 to 10 carbon atoms, such as a phenyl group or a naphthyl group; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms, nitrogen atoms, or halogen atoms, and some of the -CH2- groups in the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms, or nitrogen atoms, resulting in the hydrocarbyl groups containing hydroxy groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), etc. 1 and R 2 is preferably a hydrocarbyl group having 1 to 4 carbon atoms.

[0023] In formula (1), R 3 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom.

[0024] R 3 Specific examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0025] R 3 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0].2,6 ] cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms such as decanyl group and adamantyl group; alkenyl groups having 2 to 20 carbon atoms such as vinyl group and 2-propenyl group; aryl groups having 6 to 20 carbon atoms such as phenyl group and naphthyl group; and groups obtained by combining these. In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom or halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom or nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a halogen atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), etc.

[0026] Specific examples of the repeating unit represented by formula (1) include, but are not limited to, those shown below. A is the same as above. [ka]

[0027] The hypervalent iodine-containing polymer may further contain a repeating unit other than the repeating unit represented by formula (1) (hereinafter also referred to as "other repeating units"). The other repeating units are not particularly limited, but are preferably those that can improve the solubility in a solvent of a polymer that is poorly soluble in the hypervalent iodine-containing repeating unit alone. Furthermore, the other repeating units are preferably those that have a rigid skeleton and are primarily composed of a repeating unit having a cyclic structure that is expected to provide high etching resistance, or a repeating unit having a styrene skeleton.

[0028] Specific examples of the other repeating units include, but are not limited to, those shown below. A is the same as above, and X Bare each independently —CH— or —O—. [ka]

[0029] [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039]

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[0040]

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[0041]

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[0043]

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[0046]

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[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] [ka]

[0057] [ka]

[0058] In the hypervalent iodine-containing polymer, the content ratio (molar ratio) of the repeating unit represented by formula (1) to the other repeating units is preferably from 10:90 to 90:10, more preferably from 15:85 to 85:15, and even more preferably from 20:80 to 80:20, where the repeating unit represented by formula (1):the other repeating units.

[0059] The weight average molecular weight (Mw) of the hypervalent iodine-containing polymer is preferably 1,000 to 500,000, and more preferably 3,000 to 100,000. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0060] Furthermore, if the hypervalent iodine-containing polymer has a broad molecular weight distribution (Mw / Mn), the presence of low-molecular-weight and high-molecular-weight polymers may result in the appearance of foreign matter on the pattern after exposure, or the pattern shape may be deteriorated. Therefore, since the effects of Mw and Mw / Mn tend to become greater as the pattern rule becomes finer, in order to obtain a resist composition that is suitable for use with fine pattern dimensions, it is preferable that the hypervalent iodine-containing polymer have a narrow Mw / Mn distribution of 1.0 to 2.0.

[0061] Examples of methods for synthesizing the hypervalent iodine-containing polymer include a method in which an aryl iodide group-containing monomer is polymerized by heating in an organic solvent with the addition of a radical polymerization initiator, and then the iodine moiety is oxidized to form a hypervalent iodine-containing polymer.

[0062] Examples of organic solvents used in the polymerization reaction include anisole, toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, cyclopentanone, cyclohexanone, methyl ethyl ketone (MEK), propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), and γ-butyrolactone (GBL). Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The amount of these initiators added is preferably 0.01 to 25 mol% of the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150° C., more preferably 60 to 100° C. The reaction time is preferably 2 to 24 hours, more preferably 2 to 12 hours from the viewpoint of production efficiency.

[0063] The polymerization initiator may be added to the monomer solution and then fed to the reaction vessel. Alternatively, an initiator solution may be prepared separately from the monomer solution, and each may be fed to the reaction vessel independently. From the perspective of quality control, it is preferable to prepare the monomer solution and the initiator solution independently and then add them dropwise, since radicals generated from the initiator during the waiting time may cause the polymerization reaction to proceed, resulting in the formation of ultra-high molecular weight polymers. Furthermore, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may be used in combination to adjust the molecular weight. In this case, the amount of these chain transfer agents added is preferably 0.01 to 20 mol % of the total amount of monomers to be polymerized.

[0064] The amount of each monomer in the monomer solution may be appropriately set so as to achieve the preferred content ratio of the repeating units described above.

[0065] The hypervalent iodine-containing polymer may be used alone or in combination of two or more types having different composition ratios, Mw and / or Mw / Mn.

[0066] [Carboxy group-containing compounds] The carboxy group-containing compound is preferably a polymer containing a repeating unit represented by the following formula (2) or a compound represented by the following formula (3). [ka]

[0067] In formula (2), R A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group. A is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX A1 -X A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * represents a bond to a carbon atom in the main chain.

[0068] In formula (3), k is 1, 2, 3 or 4.

[0069] In formula (3), R 11 is a k-valent hydrocarbon group having 1 to 40 carbon atoms or a k-valent heterocyclic group having 2 to 40 carbon atoms, and when k is 2, R 11 may be an ether bond, a carbonyl group, an azo group, a thioether bond, a carbonate bond, a carbamate bond, a sulfinyl group, or a sulfonyl group. Some or all of the hydrogen atoms in the k-valent hydrocarbon group or k-valent heterocyclic group may be substituted with a group containing a heteroatom, and some of the -CH2- groups in the k-valent hydrocarbon group may be substituted with a group containing a heteroatom. R 12 is a single bond or a hydrocarbylene group having 1 to 10 carbon atoms, and some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a hetero atom, or some of the -CH2- of the hydrocarbylene group may be substituted with a group containing a hetero atom. When k is 2, 3, or 4, each R 12may be the same as or different from each other.

[0070] R 11 The k-valent hydrocarbon group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. The k-valent hydrocarbon group is a group obtained by eliminating k hydrogen atoms from a hydrocarbon. Examples of the hydrocarbon include alkanes having 1 to 40 carbon atoms, alkenes having 2 to 40 carbon atoms, alkynes having 2 to 40 carbon atoms, saturated cyclic hydrocarbons having 3 to 40 carbon atoms, unsaturated cyclic hydrocarbons having 3 to 40 carbon atoms, and aromatic hydrocarbons having 6 to 40 carbon atoms.

[0071] Examples of the alkanes having 1 to 40 carbon atoms include methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, and structural isomers thereof.

[0072] Examples of the alkenes having 1 to 40 carbon atoms include ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, and structural isomers thereof.

[0073] Examples of the alkyne having 1 to 40 carbon atoms include acetylene, propyne, butyne, pentyne, hexyne, heptyne, octyne, nonyne, decyne, and structural isomers thereof.

[0074] Examples of the cyclic saturated hydrocarbon having 3 to 40 carbon atoms include cyclopropane, cyclobutane, cyclohexane, cycloheptane, cyclooctane, adamantane, and norbornane.

[0075] Examples of the cyclic unsaturated hydrocarbon having 3 to 40 carbon atoms include cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, and norbornene.

[0076] Examples of the aromatic hydrocarbon having 6 to 40 carbon atoms include benzene, naphthalene, and biphenyl.

[0077] R11 The k-valent heterocyclic group represented by the following formula is a group obtained by eliminating k hydrogen atoms from a heterocyclic compound. Examples of the heterocyclic compound include furan, pyridine, pyrazole, and thiazolidine.

[0078] The k-valent hydrocarbon group or k-valent heterocyclic group may have some or all of its hydrogen atoms substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, and as a result, may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. Furthermore, the k-valent hydrocarbon group may have some of its -CH- groups substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, and as a result, may contain a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), etc.

[0079] R 11The hydrocarbylene group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,1 alkanediyl groups having 1 to 20 carbon atoms, such as a 2-diyl group; cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms, such as a cyclopentanediyl group, a cyclohexanediyl group, a norbornanediyl group, and an adamantanediyl group; unsaturated aliphatic hydrocarbylene groups having 2 to 20 carbon atoms, such as a vinylene group and a propene-1,3-diyl group; arylene groups having 6 to 20 carbon atoms, such as a phenylene group and a naphthylene group; and groups obtained by combining these. In addition, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, or some of the -CH- constituting the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbylene group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride or the like.

[0080] Among the carboxy group-containing compounds represented by formula (3), those in which k is 2, 3, or 4 are preferred. In this case, when mixed with a hypervalent iodine compound, a high-molecular-weight, strong resist film is easily formed, which is preferred from the viewpoints of etching resistance and developer resistance.

[0081] Specific examples of the carboxyl group-containing repeating unit represented by formula (2) include, but are not limited to, those shown below. A is the same as above. [ka]

[0082] [ka]

[0083] Specific examples of the carboxy group-containing compound represented by formula (3) include, but are not limited to, the following: [ka]

[0084] [ka]

[0085] [ka]

[0086] [ka]

[0087] [ka]

[0088] [ka]

[0089] The carboxyl group-containing polymer containing the repeating unit represented by formula (2) may further contain a repeating unit other than the repeating unit represented by formula (2) (hereinafter also referred to as "other repeating units"). The repeating unit other than the repeating unit represented by formula (2) is not particularly limited, but is preferably one that can improve the solubility in a solvent of a polymer that is poorly soluble in a repeating unit having a carboxyl group alone. Furthermore, the repeating unit other than the repeating unit represented by formula (2) is preferably a repeating unit having a cyclic structure with a rigid skeleton that is expected to have high etching resistance, or a repeating unit having a styrene skeleton.

[0090] Specific examples of repeating units other than the repeating unit represented by formula (2) include the same as those exemplified as specific examples of other repeating units that may be contained in the hypervalent iodine-containing polymer, but are not limited to these.

[0091] In the carboxyl group-containing polymer, the molar ratio of the carboxyl group-containing repeating units to the other repeating units is preferably 10:90 to 90:10, more preferably 15:85 to 85:15, and even more preferably 20:80 to 80:20.

[0092] The weight average molecular weight (Mw) of the carboxy group-containing polymer is preferably 1,000 to 500,000, more preferably 3,000 to 100,000. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0093] Furthermore, if the carboxyl group-containing polymer has a broad molecular weight distribution (Mw / Mn), the presence of low-molecular-weight and high-molecular-weight polymers may result in the appearance of foreign matter on the pattern after exposure, or the pattern shape may be deteriorated. Therefore, since the effects of Mw and Mw / Mn tend to become greater as the pattern rule becomes finer, in order to obtain a resist composition that is suitable for use with fine pattern dimensions, it is preferable that the carboxyl group-containing polymer have a narrow Mw / Mn distribution of 1.0 to 2.0.

[0094] The carboxyl group-containing polymer can be synthesized, for example, by polymerizing a monomer that provides the repeating unit described above in an organic solvent with the addition of a radical polymerization initiator by heating.

[0095] Specific examples of organic solvents used in the polymerization reaction include anisole, toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, cyclopentanone, cyclohexanone, methyl ethyl ketone (MEK), propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), and γ-butyrolactone (GBL). Specific examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The amount of the polymerization initiator added is preferably 0.01 to 25 mol% of the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150° C., more preferably 60 to 100° C. The reaction time is preferably 2 to 24 hours, more preferably 2 to 12 hours from the viewpoint of production efficiency.

[0096] The polymerization initiator may be added to the monomer solution and then fed to the reaction vessel. Alternatively, an initiator solution may be prepared separately from the monomer solution, and each may be fed to the reaction vessel independently. From the perspective of quality control, it is preferable to prepare the monomer solution and the initiator solution independently and then add them dropwise, since radicals generated from the initiator during the waiting time may cause the polymerization reaction to proceed, resulting in the formation of ultra-high molecular weight polymers. Furthermore, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may be used in combination to adjust the molecular weight. In this case, the amount of the chain transfer agent added is preferably 0.01 to 20 mol % of the total amount of monomers to be polymerized.

[0097] The amount of each monomer in the monomer solution may be appropriately set so as to achieve the preferred content ratio of the repeating units described above.

[0098] The carboxyl group-containing compounds may be used alone or in combination of two or more.

[0099] In the resist composition of the present invention, the content ratio of the hypervalent iodine-containing polymer to the carboxy group-containing compound (when the carboxy group-containing compound is a polymer, the content ratio of the hypervalent iodine-containing repeating units in the hypervalent iodine-containing polymer to the carboxy group-containing repeating units in the polymer) is preferably hypervalent iodine-containing polymer:carboxy group-containing compound=10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30, in molar ratio.

[0100] [solvent] The resist composition contains a solvent. The solvent is not particularly limited as long as it can dissolve the hypervalent iodine-containing polymer, the carboxyl group-containing compound, and other components described below and can form a film. Such a solvent is preferably an organic solvent, such as ketones such as cyclohexanone, anisole, methyl-2-n-pentyl ketone, and methyl isoamyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, 4-methyl-2-pentanol, and methyl 2-hydroxyisobutyrate; propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether; Examples of suitable solvents include ethers such as propylene glycol dimethyl ether and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono tert-butyl ether acetate; carboxylic acids such as formic acid, acetic acid, and propionic acid; lactones such as γ-butyrolactone; and mixed solvents thereof.

[0101] The content of the solvent in the resist composition of the present invention is preferably an amount such that the solids concentration in the resist composition is 0.1 to 20 mass%, more preferably 0.1 to 15 mass%, and even more preferably 0.1 to 10 mass%. In the present invention, the term "solids" refers collectively to all components of the resist composition other than the solvent. The solvents may be used alone or in combination of two or more.

[0102] [Other ingredients] The resist composition may further contain a surfactant. The surfactant is preferably a fluorine-based and / or silicone-based surfactant. Examples of such surfactants include those described in paragraph

[0276] of U.S. Patent Application Publication No. 2008 / 0248425. Furthermore, surfactants other than the fluorine-based and / or silicone-based surfactants described in paragraph

[0280] of U.S. Patent Application Publication No. 2008 / 0248425 may also be used.

[0103] When the resist composition contains the surfactant, the content thereof is preferably 0.0001 to 2 mass % of the total solid content. The surfactant may be used alone or in combination of two or more.

[0104] The resist composition may further contain a radical scavenger, which can control photoreactions during photolithography and adjust sensitivity.

[0105] Examples of the radical scavenger include hindered phenols, quinones, hindered amines, and thiol compounds. Specific examples of hindered phenols include dibutylhydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Examples of quinones include 4-methoxyphenol (methoquinone) and hydroquinone. Examples of hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidine-N-oxy radical. Examples of thiols include dodecanethiol and hexadecanethiol.

[0106] When the resist composition contains the radical scavenger, the content thereof is preferably 0.01 to 10 mass % of the total solid content. The radical scavenger may be used alone or in combination of two or more.

[0107] The resist composition may further contain a crosslinking agent, which promotes the crosslinking reaction during photolithography, improves the glass transition temperature of the pattern, and allows for the production of a pattern with excellent fine-line resolution.

[0108] Examples of the crosslinking agent include compounds having a carbon-carbon unsaturated bond as a functional group, such as a vinyl group, a (meth)acrylate group, an allyl group, an alkynyl group, or an aromatic ring. Specific examples of compounds having a vinyl group include linear alkenes, branched alkenes, and cyclic alkenes, which may have a substituent. Examples of compounds having a (meth)acrylate group include acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, which may have a substituent. Examples of compounds having an allyl group include allyl alcohols, allyl ethers, allyl esters, allyl amides, allyl amines, and allyl group-containing isocyanurates, which may have a substituent. Examples of compounds having an alkynyl group include linear alkynes, branched alkynes, cyclic alkynes, alkynyl alcohols, alkynyl ethers, alkynyl esters, alkynyl amides, alkynyl amines, and alkynyl group-containing isocyanurates, which may have a substituent. Examples of compounds having an aromatic ring include arenes, heteroarenes, styrene, stilbene, phenylacetylene, acenaphthylene, chalcone, and the like, which may have a substituent. The crosslinking agent may have only one of the above functional groups, or may have a plurality of functional groups. The number of the above functional groups contained in the crosslinking agent is preferably 1 to 10, and more preferably 2 to 8.

[0109] When the resist composition contains the crosslinking agent, the content thereof is preferably 0.01 to 50 mass % of the total solid content. The crosslinking agents may be used alone or in combination of two or more.

[0110] When the resist composition contains the crosslinking agent, it may further contain a photopolymerization initiator. The photopolymerization initiator generates radicals when irradiated with high-energy rays, and can promote crosslinking of the crosslinking agent.

[0111] Specific examples of the photopolymerization initiator include benzophenone, methyl O-benzoylbenzoate, 4-benzoyl-4'-methyldiphenyl ketone, dibenzyl ketone, fluorenone and other benzophenone derivatives; 2,2'-diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino acetophenone derivatives such as 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methylpropan-1-one and methyl phenylglyoxylate; thioxanthone derivatives such as thioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone and diethylthioxanthone; benzil, benzil dimethyl ketal ... Benzyl derivatives such as benzyl-β-methoxyethyl acetal; benzoin, benzoin methyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and other benzoin derivatives; 1-phenyl-1,2-butanedione-2-(O-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(O-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime, 1-phenyl-1, Oxime compounds such as 2-propanedione-2-(O-benzoyl)oxime, 1,3-diphenylpropanetrione-2-(O-ethoxycarbonyl)oxime, 1-phenyl-3-ethoxypropanetrione-2-(O-benzoyl)oxime-1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)]ethanone, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime);α-Hydroxyketone compounds such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]phenyl}-2-methylpropane; 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl) Examples of suitable compounds include α-aminoalkylphenone compounds such as butan-1-one; phosphine oxide compounds such as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; and titanocene compounds such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium.

[0112] When the resist composition contains the photopolymerization initiator, its content is preferably 0.1 to 10 mass %, more preferably 0.1 to 5 mass %, and most preferably 0.1 to 1 mass %, based on the total solid content. When the content is 0.1 mass % or more, a sufficient blending effect can be obtained.

[0113] As described above, the resist composition contains a hypervalent iodine-containing polymer and a carboxyl group-containing compound as main components, but does not contain an acid-labile group-containing polymer or a photoacid generator, which are contained in conventional chemically amplified resist compositions. However, the resist composition of the present invention can form a positive-tone pattern in which the exposed portions are soluble in a developer, or a negative-tone pattern in which the exposed portions are insoluble in a developer, particularly by EB or EUV exposure. The mechanism behind this is not completely clear, but is presumed to be as follows, for example.

[0114] The repeating unit having a hypervalent iodine structure represented by formula (1) has a three-coordinate structure with an aryl group and a carboxylate ligand. It is believed that when a hypervalent iodine-containing polymer containing such a repeating unit is mixed with a carboxyl group-containing compound, an exchange of the carboxylate ligand occurs via an equilibrium reaction. If the original carboxylate ligand can be removed in some way, a hypervalent iodine compound with a new ligand is generated. For example, if poly(p-iodobenzene diacetate) is mixed with a carboxyl group-containing compound as a hypervalent iodine-containing polymer and the resulting low-boiling acetic acid is removed, the ligand exchange is completed. Here, the hypervalent iodine-containing polymer is crosslinked by the carboxyl group-containing compound, resulting in the production of a polymer with a higher molecular weight.

[0115] The crosslinked polymer is generated during film formation. This is because even if such a crosslinked polymer is synthesized in advance, it is insoluble in most organic solvents and therefore a solution cannot be prepared. This is presumably because hypervalent iodine compounds, which are inherently highly polarizable and therefore have low solvent solubility, become even less soluble when a carboxyl group-containing compound is used as a ligand. Therefore, it is desirable to complete the ligand exchange reaction and form a resist film by removing the original low-molecular-weight carboxylic acid component during film formation and the subsequent baking process.

[0116] In the resist film obtained from the resist composition of the present invention, the polarity of the hypervalent iodine-containing polymer, which is the main component of the resist film, changes when exposed to light, and a pattern is formed by the development process. The mechanism by which this occurs is not completely clear, but is presumed to be as follows, for example.

[0117] The resist composition of the present invention can be either positive-working or negative-working depending on the selection of components. In the case of a positive-working resist composition, the composition contains a polymer to which a hypervalent iodine compound is bonded during film formation. This polymer is decomposed by light to form a monovalent iodine compound, and at the same time, the bond between the carboxyl group-containing compound and the hypervalent iodine compound is released, resulting in a decrease in molecular weight. It is believed that this results in the formation of a positive-working pattern in which the exposed areas are removed by an organic solvent.

[0118] On the other hand, negative-tone patterns contain polymers crosslinked by hypervalent iodine compounds generated during film formation. When these polymers are decomposed by light, crosslinks or re-crosslinking of bonds occurs, resulting in an increase in molecular weight and a change in polarity. As a result, it is presumed that a negative-tone pattern is formed in which the unexposed areas are removed by an alkaline aqueous solution.

[0119] The hypervalent iodine-containing polymer used in the present invention hardly volatilizes even under vacuum conditions during EB or EUV exposure. When a hypervalent iodine compound with a low molecular weight is used, the compound decomposed by exposure volatilizes under vacuum, causing significant exposure shrinkage of the resist film, contamination of the exposure machine by volatile components, and dimensional changes due to shrinkage of the resist pattern. Therefore, the use of the hypervalent iodine compound used in the present invention solves the above-mentioned problems. Furthermore, the use of a hypervalent iodine-containing polymer with a high molecular weight improves the glass transition temperature of the pattern, prevents pattern distortion, improves resolution, and improves etching resistance.

[0120] Based on the above assumptions, it can be said that the resist composition of the present invention is a non-chemically amplified resist composition. The resist composition of the present invention does not require an acid-labile group-containing polymer or a photoacid generator, as is the case with conventional chemically amplified resist compositions. Therefore, adverse effects due to acid diffusion (e.g., image blurring) do not occur, and fine patterns can be resolved.

[0121] The resist composition of the present invention is particularly effective in EUV lithography because it contains iodine atoms with high absorption capacity for EUV light, which reduces shot noise and enables the achievement of higher resolution and lower LWR.

[0122] Metal resists containing metal tin compounds as their main component, which have high absorption capacity for EUV light similar to that of iodine atoms, have been reported as EUV resist compositions capable of forming fine patterns (e.g., Patent Document 2). However, as mentioned above, such metal resists have many problems, such as insufficient solubility in solvents, poor storage stability, and defects due to post-etching residues caused by the inclusion of metal elements. On the other hand, the resist composition of the present invention is advantageous over metal resists in terms of defects because it does not contain metal elements, and it also has no issues with solubility in solvents. Furthermore, the resist composition of the present invention can be applied to both positive-tone and negative-tone resists, thereby offering a wide range of uses. For example, in the contact hole formation process, metal resists developed using negative-tone development require a reversal process step after pillar pattern formation, whereas positive-tone resists do not require such a step. Therefore, from the perspective of process simplicity, the resist composition of the present invention can be said to be more useful than metal resists.

[0123] Japanese Patent Publication No. 2015-180928 and Japanese Patent Publication No. 2018-95853 describe resist compositions containing a hypervalent iodine compound as an additive, and resist compositions incorporating a hypervalent iodine compound into the polymer backbone of a base polymer. However, these patent documents only describe the properties of the resist compositions as being able to improve line edge roughness, and make no mention of the possibility of the hypervalent iodine compound being photodecomposed or functioning as a material for a non-chemically amplified resist composition. Furthermore, according to the descriptions of the blending amounts and specific examples, the hypervalent iodine compound is not the main component. Therefore, these patent documents do not suggest a material that can reduce shot noise in EUV lithography and that can form fine patterns as a material for a non-chemically amplified resist composition, as described in the present invention. In other words, it can be said that the present invention clearly provides a novel resist composition and pattern formation method.

[0124] [Pattern formation method] When the resist composition of the present invention is used in the manufacture of various integrated circuits, known lithography techniques can be applied. For example, a pattern formation method can include a method comprising the steps of: forming a resist film on a substrate using the resist composition, or on an underlayer film of a substrate having an underlayer film laminated thereon; exposing the resist film to high-energy rays; and, if necessary, developing the exposed resist film using a developer.

[0125] First, the resist composition of the present invention is applied to a substrate for integrated circuit manufacturing, or to a substrate having a laminated underlayer film (e.g., Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating), or to a substrate for mask circuit manufacturing, or to a substrate having a laminated underlayer film (e.g., CrO, CrON, MoSi2, SiO2), by a suitable coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, or doctor coating, to a coating thickness of 0.01 to 2 μm. This is then prebaked on a hot plate, preferably at 60 to 200°C for 10 seconds to 30 minutes, more preferably at 80 to 180°C for 30 seconds to 20 minutes, to form a resist film. The underlayer film refers to a film formed between the substrate and the resist film in a multilayer resist process. The underlayer film is not particularly limited, and conventionally known underlayer films can be used.

[0126] Next, the resist film is exposed to high-energy radiation. Examples of the high-energy radiation include ultraviolet radiation, far ultraviolet radiation, EB, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation. When ultraviolet radiation, far ultraviolet radiation, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation are used as the high-energy radiation, the exposure dose is preferably 1 to 300 mJ / cm, either directly or using a mask for forming a desired pattern. 2 approximately, more preferably 10 to 200 mJ / cm 2 When EB is used as the high energy beam, the exposure dose is preferably 0.1 to 8000 μC / cm 2 directly or using a mask for forming a desired pattern. 2 approximately, more preferably 0.5 to 5000 μC / cm 2 The resist composition of the present invention is particularly suitable for fine patterning using high-energy rays such as EB or EUV.

[0127] After exposure, PEB is performed as needed, preferably on a hot plate or in an oven at 30 to 200°C for 10 seconds to 30 minutes, more preferably at 60 to 120°C for 30 seconds to 20 minutes.

[0128] After exposure or PEB, the film is developed with a developer as needed to perform patterning. The developer used in this case may be an aqueous alkali solution such as an aqueous tetramethylammonium hydroxide solution or an aqueous tetrabutylammonium hydroxide solution; 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, 5-methyl-2-hexanone, methylcyclohexanone, acetophenone, methylacetophenone, isopropyl alcohol, isoamyl alcohol, n-butanol, tert-butyl alcohol, tert-pentyl alcohol, n-pentanol, cyclohexanol, formic acid, acetic acid, propionic acid, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, cyclohexyl acetate, 4-tert-butylcyclohexyl acetate, octyl acetate, isobornyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, chloroform ... Ethyl lactate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, ethyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate Examples of organic solvents that can be used include ethyl acetate, 2-phenylethyl acetate, 2-propanol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 3-methyl-1-butanol, diacetone alcohol, 4-methyl-2-pentanol, 3-methylcyclohexanol, 3,5,5-trimethylhexyl alcohol, 2,6-dimethyl-4-heptanol, toluene, anisole, and ε-caprolactone. These developers may be used alone or in combination of two or more.

[0129] After development, rinsing is performed as necessary. A preferred rinsing solution is a solvent that is miscible with the developer but does not dissolve the resist film. Preferred examples of such solvents include alcohols having 3 to 10 carbon atoms, ether compounds having 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents having 6 to 12 carbon atoms.

[0130] Rinsing can reduce the occurrence of resist pattern collapse and defects. Rinsing is not always necessary, and not performing rinsing can reduce the amount of solvent used. [Example]

[0131] The present invention will be specifically explained below by showing synthesis examples, examples and comparative examples, but the present invention is not limited to the following examples.

[0132] In the synthesis examples below, the monomers used in the synthesis of the polymers are as follows: [ka]

[0133] [ka]

[0134] [ka] [1] Synthesis of iodine-containing polymers [Synthesis Example 1-1] Synthesis of iodine-containing polymer PI-2 A monomer-polymerization initiator solution was prepared by placing 43 g of monomer I-1, 57 g of monomer a-1, 4.2 g of V-601 (Fujifilm Wako Pure Chemical Industries, Ltd.), and 160 g of MEK in a flask under a nitrogen atmosphere. 80 g of MEK was placed in a separate flask under a nitrogen atmosphere and heated to 80°C with stirring. The monomer-polymerization initiator solution was then added dropwise over 4 hours. After the addition, the polymerization solution was stirred for 2 hours while maintaining the temperature at 80°C, and then cooled to room temperature. The resulting polymerization solution was added dropwise to 4,000 g of vigorously stirred hexane, and the precipitated polymer was filtered. The resulting polymer was washed twice with 1,200 g of hexane and then vacuum-dried at 50°C for 20 hours to obtain polymer PI-2 as a white powder (yield: 92 g, 92%). The Mw of polymer PI-2 was 7,000, and the Mw / Mn ratio was 1.44. The Mw is a polystyrene-equivalent value measured by GPC using THF as a solvent. [ka]

[0135] [Synthesis Examples 1-2 to 1-8] Synthesis of hypervalent iodine-containing polymers PI-1, PI-3 to PI-10 The polymers shown in Table 1 below were synthesized in the same manner as in Synthesis Example 1-1, except that the types and blending ratios of the monomers were changed.

[0136] [Table 1]

[0137] [2] Synthesis of hypervalent iodine-containing polymers [Synthesis Example 2-1] Synthesis of hypervalent iodine-containing polymer PH-2 Under a nitrogen atmosphere, polymer PI-2 (10 g) and 100 g of acetic anhydride were mixed in a flask, and 18 g of 35% hydrogen peroxide was added dropwise at room temperature. The reaction solution was stirred at room temperature for 2 hours, then stirred at 60°C for 5 hours, and then returned to room temperature and stirred for an additional 2 hours. Hexane was added to the resulting reaction solution, and the supernatant was removed to obtain 11.5 g of the target polymer PH-2 as an oil (94% yield). The Mw of polymer PH-2 was 8600, and the Mw / Mn ratio was 1.44. Note that Mw was measured using GPC in THF as a solvent, converted into polystyrene equivalents. [ka]

[0138] [Synthesis Examples 2-2 to 2-8] Synthesis of hypervalent iodine-containing polymers PH-1 and PH-3 to PH-10 The polymers shown in Table 2 below were synthesized in the same manner as in Synthesis Example 2-1, except that the type of iodine-containing polymer used was changed.

[0139] [Table 2]

[0140] [3] Synthesis of carboxyl group-containing polymers [Synthesis Example 3-1] Synthesis of carboxyl group-containing polymer P-1 Under a nitrogen atmosphere, a flask was charged with 22 g of monomer b-4, 78 g of monomer a-1, 5.4 g of V-601 (Fujifilm Wako Pure Chemical Industries, Ltd.), and 160 g of MEK to prepare a monomer-polymerization initiator solution. 55 g of MEK was charged to a separate flask under a nitrogen atmosphere and heated to 80°C with stirring. The monomer-polymerization initiator solution was then added dropwise over 4 hours. After the addition, the polymerization solution was stirred for 2 hours while maintaining the temperature at 80°C, and then cooled to room temperature. The resulting polymerization solution was added dropwise to 4,000 g of vigorously stirred hexane, and the precipitated polymer was filtered. The resulting polymer was washed twice with 1,200 g of hexane and then vacuum-dried at 50°C for 20 hours to obtain polymer P-1 as a white powder (yield: 100 g, 98%). The Mw of polymer P-2 was 7,000, and the Mw / Mn ratio was 1.44. The Mw is a polystyrene-equivalent value measured by GPC using THF as a solvent. [ka]

[0141] [Synthesis Examples 3-2 to 3-5] Synthesis of Carboxy Group-Containing Polymers P-2 to P-4 and Comparative Polymer P-5 The polymers shown in Table 3 below were synthesized in the same manner as in Synthesis Example 3-1, except that the types and blending ratios of the respective monomers were changed.

[0142] [Table 3]

[0143] [4] Preparation of resist composition [Examples 1-1 to 1-17, Comparative Examples 1-1 to 1-4] Resist compositions (R-01 to R-17, CR-01, and CR-02) were prepared by dissolving a hypervalent iodine compound and a carboxyl group-containing compound in a solvent containing 0.01% by mass of a surfactant (PF-636, Omnova) according to the compositions shown in Table 4 below, and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter. Resist compositions (CR-03 and CR-04) were prepared by dissolving a polymer, a photoacid generator, and a sensitivity adjuster in a solvent containing 0.01% by mass of a surfactant (PF-636, Omnova) according to the compositions shown in Table 5 below, and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter.

[0144] [Table 4]

[0145] [Table 5]

[0146] In Tables 4 and 5, the hypervalent iodine compound H-1, carboxy group-containing compounds m-1 to m-4, photoacid generator PAG-1, sensitivity adjuster Q-1 and solvent are as follows. [ka]

[0147] [ka]

[0148] [ka]

[0149] [ka]

[0150] Solvent: PGMEA (propylene glycol monomethyl ether acetate) AcOH (acetic acid) GBL (γ-butyrolactone)

[0151] [5] EUV lithography evaluation (line and space patterns) [Examples 2-1 to 2-17, Comparative Examples 2-1 to 2-4] Each resist composition (R-01 to R-17, CR-01 to CR-04) was spin-coated onto a Si substrate coated with a 20 nm thick silicon-containing spin-on hard mask (SHB-A940, manufactured by Shin-Etsu Chemical Co., Ltd.) (43% silicon by mass), and then prebaked (PAB) for 60 seconds on a hot plate at the temperature listed in Table 6 to produce a 40 nm thick resist film. The resist film was then exposed to light using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination) to form a 36 nm line-and-space (LS) 1:1 pattern. Then, PEB was performed on a hot plate at the temperature listed in Table 6 for 60 seconds, followed by development for 30 seconds using the developer listed in Table 6 to form an LS pattern with a space width of 18 nm and a pitch of 36 nm.

[0152] The resulting resist patterns were evaluated as follows, and the results are shown in Table 4.

[0153] [Sensitivity evaluation] The LS pattern was observed using a length measurement SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the optimum exposure dose Eop (mJ / cm) for obtaining an LS pattern with a space width of 18 nm and a pitch of 36 nm was determined. 2 ) was calculated and used as the sensitivity.

[0154] [LWR rating] The LS pattern obtained by irradiation with the optimum exposure dose was measured at 10 points in the longitudinal direction of the space width using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the LWR was calculated as three times the standard deviation (σ) (3σ). The smaller this value, the less roughness and the more uniform the space width pattern obtained.

[0155] [Limiting resolution evaluation] The limiting line width (nm) that can be resolved when forming a pattern by gradually increasing the exposure dose from the optimum exposure dose at which the LS pattern is formed was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a finer pattern can be formed.

[0156] [Table 6]

[0157] Developer: nBA (butyl acetate) TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0158] The results shown in Table 6 demonstrate that both positive-tone and negative-tone patterns can be formed depending on the developer used. Furthermore, when the resist compositions of the present invention were compared with Comparative Examples 2-1 and 2-2, which used low-molecular-weight hypervalent iodine compounds, they exhibited excellent resolution and LWR. They also exhibited excellent sensitivity, resolution, and LWR when compared with Comparative Examples 2-3 and 2-4, which were chemically amplified resist compositions using an acid-catalyzed reaction. Therefore, the resist compositions of the present invention demonstrated excellent resolution in LS pattern formation by EUV exposure.

[0159] [6] EUV lithography evaluation (contact hole pattern) [Examples 3-1 to 3-17, Comparative Examples 3-1 to 3-4] Each resist composition (R-01 to R-17, CR-01 to CR-04) was spin-coated onto a Si substrate with a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd., and then subjected to PAB for 60 seconds at the temperature listed in Table 7 using a hot plate to produce a 50 nm thick resist film. The resist film was then exposed to light using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadruple pole illumination, wafer dimensions 64 nm pitch, +20% bias hole pattern mask), subjected to PEB for 60 seconds on a hot plate at the temperature listed in Table 7, and developed for 30 seconds using the developer listed in Table 7 to obtain a 32 nm hole pattern.

[0160] The resulting resist patterns were evaluated as follows, and the results are shown in Table 7.

[0161] [Sensitivity evaluation] The contact hole pattern was observed using a length measuring SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the optimum exposure dose Eop (mJ / cm) for obtaining a hole pattern with a dimension of 22 nm was determined. 2 ) was calculated and used as the sensitivity.

[0162] [CDU Rating] The dimensions of 50 hole patterns obtained by irradiation with the optimal exposure dose were measured, and the CDU was calculated as three times the standard deviation (σ). The smaller this value, the more uniform the hole diameter pattern obtained.

[0163] [Limiting resolution evaluation] The limiting hole diameter (nm) that can be resolved when forming a hole pattern by gradually decreasing the exposure dose from the optimum exposure dose required to form the hole pattern was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a pattern with a finer hole diameter can be formed.

[0164] [Table 7]

[0165] The results shown in Table 7 demonstrate that both positive-tone and negative-tone patterns can be formed by selecting the right developer. Furthermore, when the resist compositions of the present invention were compared with Comparative Examples 3-1 and 3-2, which used low-molecular-weight hypervalent iodine compounds, they exhibited excellent resolution and CDU. They also exhibited excellent sensitivity, resolution, and CDU when compared with Comparative Examples 3-3 and 3-4, which used chemically amplified resist compositions using an acid-catalyzed reaction. Therefore, the resist compositions of the present invention demonstrated excellent resolution when forming contact hole patterns using EUV exposure.

Claims

1. A resist composition comprising a polymer containing a repeating unit having a hypervalent iodine structure represented by the following formula (1), a carboxy group-containing compound, and a solvent: 【Chemistry 1】 (In the formula, m is 0 or 1. When m is 0, n is 0, 1, 2, 3, or 4, and when m is 1, n is 0, 1, 2, 3, 4, 5, or 6. R A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group. R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms. R 3 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom.

2. 2. The resist composition according to claim 1, wherein the carboxy group-containing compound is a polymer containing a repeating unit represented by the following formula (2) or a compound represented by the following formula (3): 【Chemistry 2】 (In the formula, R A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group. X A represents a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-X A1 - is. X A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * represents a bond to a carbon atom in the main chain. k is 1, 2, 3 or 4. R 11 is a k-valent hydrocarbon group having 1 to 40 carbon atoms or a k-valent heterocyclic group having 2 to 40 carbon atoms, and when k is 2, R 11 may be an ether bond, a carbonyl group, an azo group, a thioether bond, a carbonate bond, a carbamate bond, a sulfinyl group, or a sulfonyl group. In addition, some or all of the hydrogen atoms of the k-valent hydrocarbon group or the k-valent heterocyclic group may be substituted with a group containing a hetero atom, and the —CH 2 A portion of - may be substituted with a group containing a hetero atom. R 12 represents a single bond or a hydrocarbylene group having 1 to 10 carbon atoms, and some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a hetero atom, and the —CH 2 When k is 2, 3, or 4, each R 12 may be the same as or different from each other.)

3. A laminate comprising a substrate and a resist film formed on the substrate from the resist composition according to claim 1 or 2.

4. The laminate according to claim 3 , further comprising an underlayer film between the substrate and the resist film.

5. 4. The laminate according to claim 3, wherein the resist film is formed by ligand exchange between the hypervalent iodine compound and a carboxy group-containing compound.

6. 3. A pattern forming method comprising the steps of: forming a resist film on a substrate, or on an underlayer film of a substrate having an underlayer film laminated thereon, using the resist composition according to claim 1; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer.

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