Resist composition and patterning process

Abstract

To provide a non-chemically-amplified resist composition excellent in sensitivity and resolution in photolithography using high-energy radiation, and a patterning process using the resist composition.SOLUTION: A resist composition comprising a hypervalent iodine compound represented by the following formula (1), a carboxy-containing polymer having a specific structure, 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-type acid generator with a polymerizable unsaturated bond 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 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 describes 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, when used to pattern contact holes, an additional reversal process step is required, 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 present inventors discovered that a resist composition containing as its main components a specific hypervalent iodine compound and a polymer having a carboxy group and a specific cyclic structure provides a resist film that exhibits extremely high sensitivity and excellent resolution, and is therefore 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 hypervalent iodine compound represented by the following formula (1), a carboxy group-containing polymer, and a solvent: The resist composition, wherein the carboxy group-containing polymer comprises a repeating unit represented by the following formula (2), and at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (3), a repeating unit represented by the following formula (4), a repeating unit represented by the following formula (5), a repeating unit represented by the following formula (6), and a repeating unit represented by the following formula (7). [ka] (In the formula, n is an integer of 0 to 5. 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 2may 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 40 carbon atoms which may contain a halogen atom or a heteroatom. [ka] (In the formula, a is an integer of 0 to 2, b is an integer that satisfies 0≦b≦5+2a, and c is an integer of 0 to 2.) R A is a hydrogen atom, a fluorine 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 at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain. X B are each independently —CH— or —O—. R 11 is a hydroxy group, a halogen atom, a nitro group, a sulfo group, a carboxy group, an isocyanate group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, -N(R 11A )(R 11B ), -P(R 11C )(R 11D ), -B(OR 11E )(OR 11F ), -OR 11G , -C(=O)-OR 11G , -OC(=O)-R 11G R 11A and R 11B are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. 11C and R 11D are each independently a hydrocarbyl group having 1 to 20 carbon atoms. 11E and R 11Fare each independently a hydrocarbyl group having 1 to 20 carbon atoms. 11E and R 11F and may be bonded to each other to form a ring together with the boron atom to which they are attached. 11G are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R 12 , R 13 and R 15 ~R 17 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 12 and R 13 and may be bonded to each other to form a ring together with the carbon atoms to which they are attached, and R 15 and R 16 and / or R 16 and R 17 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 14 is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 2. A laminate comprising a substrate and a resist film obtained from the resist composition 1 on the substrate. 3. A laminate of 2, comprising an underlayer film between the substrate and the resist film. 4. 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; exposing the resist film to i-line, KrF excimer laser, ArF excimer laser, electron beam, or extreme ultraviolet light; and developing the exposed resist film using a developer. 5. The pattern forming method of 4, wherein the developer is an organic solvent. [Effects of the Invention]

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

[0016] [Resist composition] The resist composition of the present invention contains a predetermined hypervalent iodine compound and a carboxy group-containing polymer as main components.

[0017] [Hypervalent iodine compounds] The hypervalent iodine compound is a three-coordinate hypervalent iodine compound represented by the following formula (1). [ka]

[0018] In formula (1), n is an integer of 0 to 5.

[0019] 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 the carbon atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 10 carbon atoms 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 an allyl 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.

[0020] In formula (1), R 3 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 to 5, each R 3 may be the same or different. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 40 carbon atoms may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 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 2,6cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as a ]decanyl group, an adamantyl group, or an adamantylmethyl group; and aryl groups having 6 to 40 carbon atoms, such as a phenyl group, a naphthyl group, or an anthracenyl group. 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, so that the hydrocarbyl groups may contain 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)-), or the like.

[0021] Specific examples of the hypervalent iodine compound represented by formula (1) include, but are not limited to, the following: [ka]

[0022] [ka]

[0023] [ka]

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] [Carboxy group-containing polymer] The carboxyl group-containing polymer contains a repeating unit represented by the following formula (2) and at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (3), a repeating unit represented by the following formula (4), a repeating unit represented by the following formula (5), a repeating unit represented by the following formula (6), and a repeating unit represented by the following formula (7). [ka]

[0028] In formulas (2) to (7), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0029] In formula (2), 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 at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain.

[0030] In formula (3), a is an integer of 0 to 2. b is an integer that satisfies 0≦b≦5+2a.

[0031] In formula (3), R 11 is a hydroxy group, a halogen atom, a nitro group, a sulfo group, a carboxy group, an isocyanate group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, -N(R 11A )(R 11B ), -P(R 11C )(R 11D ), -B(OR 11E )(OR 11F ), -OR 11G , -C(=O)-OR 11G , -OC(=O)-R 11GR 11A and R 11B are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. 11C and R 11D are each independently a hydrocarbyl group having 1 to 20 carbon atoms. 11E and R 11F are each independently a hydrocarbyl group having 1 to 20 carbon atoms. 11E and R 11F and may be bonded to each other to form a ring together with the boron atom to which they are attached. 11G are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

[0032] In formula (4), c is an integer of 0 to 2.

[0033] In formula (4), X B are each independently —CH— or —O—.

[0034] In formulas (4) and (7), R 12 , R 13 and R 15 ~R 17 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 12 and R 13 and may be bonded to each other to form a ring together with the carbon atoms to which they are attached, and R 15 and R 16 and / or R 16 and R 17 may be bonded to each other to form a ring together with the carbon atoms to which they are attached.

[0035] In formula (6), R 14 is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

[0036] R 11 , R 12 , R 13 and R 15 ~R17 Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0037] R 11 ~R 17 and R 11A ~R 11G 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, 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 allyl group; aryl groups having 6 to 20 carbon atoms such as phenyl group and naphthyl group; and groups obtained by combining these. 11 ~R 17 and R 11G In the hydrocarbyl group represented by the formula (I), some or all of the hydrogen atoms may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups 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 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 acid anhydride (-C(=O)-OC(=O)-), etc.

[0038] Specific examples of the repeating unit represented by formula (2) include, but are not limited to, those shown below. Ais the same as above. [ka]

[0039] [ka]

[0040] Specific examples of the repeating unit represented by formula (3) include, but are not limited to, those shown below. A is the same as above. [ka]

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] Specific examples of the repeating unit represented by formula (4) include, but are not limited to, those shown below. A and X B is the same as above. [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] Specific examples of the repeating unit represented by formula (6) include, but are not limited to, those shown below. A is the same as above. [ka]

[0052] [ka]

[0053] Specific examples of the repeating unit represented by formula (7) include, but are not limited to, those shown below. A is the same as above. [ka]

[0054] [ka]

[0055] In the carboxy group-containing polymer, the molar ratio of the repeating units represented by formula (2) to the repeating units other than the repeating units represented by formula (2) is preferably 10:90 to 90:10, more preferably 15:85 to 85:15, and even more preferably 20:80 to 80:20.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Examples of organic solvents used in the polymerization reaction include 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% based on 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, and more preferably 2 to 12 hours from the viewpoint of production efficiency.

[0060] 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 then 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 an ultra-high molecular weight polymer. The acid labile group may be used as is after being introduced into the monomer, or may be protected or partially protected after polymerization. To adjust the molecular weight, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may be used in combination. 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.

[0061] 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.

[0062] In the resist composition of the present invention, the hypervalent iodine compound and the carboxy group-containing polymer are preferably contained in such a molar ratio that the content ratio of the hypervalent iodine compound to the carboxylic acid-containing repeating units in the polymer is 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. The hypervalent iodine compound may be used alone, or two or more types having different composition ratios, Mw, and / or Mw / Mn may be used in combination. The carboxy group-containing polymer may be used alone, or two or more types having different composition ratios, Mw, and / or Mw / Mn may be used in combination.

[0063] [solvent] The resist composition of the present invention contains a solvent. The solvent is not particularly limited as long as it can dissolve the hypervalent iodine compound, the carboxyl group-containing polymer, and other components described below and can form a film. Such a solvent is preferably an organic solvent, and examples thereof include ketones such as cyclohexanone, 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, methyl 2-hydroxyisobutyrate, and 4-methyl-2-pentanol; propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, and propylene glycol monomethyl ether. Examples of suitable solvents include ethers such as ethylene 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.

[0064] 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 solids content is a general term for all components of the resist composition excluding the solvent.

[0065] [Other ingredients] The resist composition of the present invention may further contain a surfactant. The surfactant is preferably a fluorine-based and / or silicon-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 silicon-based surfactants described in paragraph

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

[0066] When the resist composition of the present invention 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.

[0067] The resist composition of the present invention may further contain a radical scavenger. By adding a radical scavenger, it is possible to control the photoreaction during photolithography and adjust the sensitivity.

[0068] 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.

[0069] When the resist composition of the present invention 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.

[0070] As described above, the resist composition of the present invention contains a hypervalent iodine compound and a carboxyl group-containing polymer 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, particularly upon exposure to EB or EUV, becomes soluble in a developer in the exposed area, thereby forming a positive-tone pattern. The mechanism by which this occurs is not completely clear, but is presumed to be as follows.

[0071] The hypervalent iodine compound used in the present invention is a tricoordinate compound, as represented by formula (1), in which an aryl group is bonded to two carboxylate ligands. It is believed that when such a tricoordinate iodine compound is mixed with a carboxylic acid compound, an exchange of the carboxylate ligands occurs via an equilibrium reaction. If the original carboxylate ligands can be removed in some way, a hypervalent iodine compound bearing a new ligand is generated. For example, by mixing iodobenzene diacetate, a relatively readily available hypervalent iodine compound, with a high molecular weight carboxylic acid compound and removing the resulting low-boiling acetic acid, the ligand exchange is completed. If the carboxylic acid compound is a polymer, the polymers are crosslinked by the hypervalent iodine compound, resulting in a high molecular weight hypervalent iodine compound.

[0072] Polymers crosslinked with hypervalent iodine compounds are generated during film formation. This is because even if such crosslinked polymers are synthesized in advance, they are insoluble in most organic solvents, making it impossible to prepare a solution. This is presumably because hypervalent iodine compounds, which have low solvent solubility due to their inherent high polarization, become even less soluble when a high-molecular-weight carboxylic acid-containing polymer 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.

[0073] The resist film obtained from the resist composition of the present invention contains a polymer crosslinked by a hypervalent iodine compound generated during film formation, and therefore has extremely low solubility in organic solvents. However, when this polymer is decomposed by light, it becomes a monovalent iodine compound, and at the same time, the crosslinks between the polymers are released, resulting in a decrease in molecular weight. As a result, the exposed area becomes soluble in a developer, which is an organic solvent, and it is presumed that this composition functions as a positive resist composition.

[0074] The polymer used in the resist composition of the present invention is a copolymer containing a carboxy group-containing unit represented by formula (2) and a repeating unit represented by any one of formulas (3) to (7). The unit represented by any one of formulas (3) to (7) has a rigid structure having a cyclic structure, and therefore has excellent collapse resistance during, for example, line and space formation, and also improves etching resistance.

[0075] Based on the above assumption, the resist composition of the present invention is a non-chemically amplified resist composition and 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.

[0076] 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.

[0077] Metal resists containing metal tin compounds as their main component, which have a 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 does not contain metal elements, making it more advantageous than metal resists in terms of defects and also posing no problems with solvent solubility. Furthermore, by using the resist composition of the present invention, a positive-tone pattern can be formed by undeveloping or organic solvent development, thereby eliminating the need for a reversal process, which is typically performed in negative-tone development, even in contact hole formation processes. From these points of view, the resist composition of the present invention can be said to be more advantageous than metal resists.

[0078] 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 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 provides a clearly novel resist composition and pattern formation method.

[0079] [Pattern formation method] When the resist composition of the present invention is used for manufacturing various integrated circuits, known lithography techniques can be applied. For example, a pattern formation method can include a method comprising the steps of: using the resist composition to form a resist film on a substrate, 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.

[0080] 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.

[0081] 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 1500 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.

[0082] After exposure, PEB is performed as needed, preferably on a hot plate or in an oven at 30 to 150°C for 10 seconds to 30 minutes, more preferably at 60 to 120°C for 30 seconds to 20 minutes.

[0083] After exposure or PEB, patterning is performed by development using a developer as needed. In the present invention, the exposed area is solubilized by organic solvent development, resulting in a positive pattern. Developers used in this case include 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, isopropyl alcohol, n-butanol, n-pentanol, formic acid, acetic acid, propionic acid, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, hexyl acetate, cyclohexyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, 3-ethoxypropionate, and the like. Examples of organic solvents that can be used include ethyl lactate, 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, 2-phenylethyl acetate, 2-propanol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, 4-methyl-2-pentanol, toluene, anisole, and xylene. These organic solvents may be used alone or in combination of two or more.

[0084] 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.

[0085] 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]

[0086] 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.

[0087] [1] Polymer synthesis The monomers used in the synthesis of the polymer are as follows: [ka]

[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] [ka]

[0092] [Synthesis Example 1] Synthesis of Polymer P-1 A monomer-polymerization initiator solution was prepared by placing 56 g of monomer a-1, 36 g of monomer b-1, 5.4 g of V-601 (Fujifilm Wako Pure Chemical Industries, Ltd.), and 180 g of MEK in a flask under a nitrogen atmosphere. 55 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 P-1 as a white powder (yield: 90 g, 98%). The Mw of polymer P-1 was 8,000, and the Mw / Mn ratio was 1.42. The Mw is a polystyrene-equivalent value measured by GPC using THF as a solvent. [ka]

[0093] [Synthesis Examples 2 to 26] Synthesis of Polymers P-2 to P-26 The polymers shown in Table 1 below were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of the respective monomers were changed.

[0094] [Table 1]

[0095] [2] Preparation of resist composition [Examples 1-1 to 1-26, Comparative Examples 1-1 to 1-3] Resist compositions (R-01 to R-26 and CR-01) were prepared by dissolving a hypervalent iodine compound and a polymer in a solvent containing 0.01% by mass of a surfactant (PF-636, Omnova) according to the compositions shown in Table 2 below, and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter. Resist compositions (CR-02 to CR-03) 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 3 below, and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter.

[0096] [Table 2]

[0097] [Table 3]

[0098] In Tables 2 and 3, the hypervalent iodine compounds (I-1 to I-3), photoacid generator PAG-1, sensitivity adjuster Q-1 and solvents are as follows. [ka]

[0099] [ka]

[0100] [ka]

[0101] Solvent: PGMEA (propylene glycol monomethyl ether acetate) AcOH (acetic acid) GBL (γ-butyrolactone)

[0102] [3] EUV Lithography Evaluation (1) [Examples 2-1 to 2-26, Comparative Examples 2-1 to 2-3] Each resist composition (R-01 to R-26, CR-01 to CR-03) 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 4 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 4 for 60 seconds, followed by development for 30 seconds in the developer listed in Table 4 to form an LS pattern with a space width of 18 nm and a pitch of 36 nm.

[0103] The resulting resist patterns were evaluated as follows, and the results are shown in Table 4.

[0104] [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.

[0105] [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.

[0106] [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.

[0107] [Table 4]

[0108] Developer: nBA (butyl acetate) TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0109] The results shown in Table 4 demonstrate that the resist composition of the present invention is excellent in sensitivity, LWR, and resolution when forming an LS pattern by EUV exposure.

[0110] [4] EUV Lithography Evaluation (2) [Examples 3-1 to 3-26, Comparative Examples 3-1 to 3-3] Each resist composition (R-01 to R-26, CR-01 to CR-03) 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 5 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 5, and developed for 30 seconds using the developer listed in Table 5 to obtain a 32 nm hole pattern.

[0111] The resulting resist patterns were evaluated as follows, and the results are shown in Table 5.

[0112] [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.

[0113] [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.

[0114] [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.

[0115] [Table 5]

[0116] The results shown in Table 5 demonstrate that the resist composition of the present invention is excellent in sensitivity, CDU, and resolution when forming a contact hole pattern by EUV exposure.

Claims

1. A resist composition comprising a hypervalent iodine compound represented by the following formula (1), a carboxy group-containing polymer, and a solvent: The resist composition, wherein the carboxy group-containing polymer comprises a repeating unit represented by the following formula (2), and at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (3), a repeating unit represented by the following formula (4), a repeating unit represented by the following formula (5), a repeating unit represented by the following formula (6), and a repeating unit represented by the following formula (7): 【Chemical 1】 (wherein n is an integer from 0 to 5. 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 40 carbon atoms which may contain a halogen atom or a heteroatom. 【Chemistry 2】 (In the formula, a is an integer of 0 to 2. b is an integer satisfying 0≦b≦5+2a. c is an integer of 0 to 2.) R A is a hydrogen atom, a fluorine 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 at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain. X B are each independently —CH 2 - or -O-. R 11 is a hydroxy group, a halogen atom, a nitro group, a sulfo group, a carboxy group, an isocyanate group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, —N(R 11A )(R 11B ), -P(R 11C )(R 11D ), -B(OR 11E )(OR 11F ), -O-R 11G , -C(=O)-O-R 11G , —O—C(═O)—R 11G It is. 11A and R 11B are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. 11C and R 11D are each independently a hydrocarbyl group having 1 to 20 carbon atoms. 11E and R 11F are each independently a hydrocarbyl group having 1 to 20 carbon atoms. 11E and R 11F and may be bonded to each other to form a ring together with the boron atom to which they are bonded. 11G are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R 12 , R 13 and R 15 ~R 17 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 12 and R 13 and may be bonded to each other to form a ring together with the carbon atoms to which they are attached, and R 15 and R 16 and / or R 16 and R 17 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 14 is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

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

3. The laminate according to claim 2 , further comprising an underlayer film between the substrate and the resist film.

4. 10. 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 i-line, KrF excimer laser, ArF excimer laser, electron beam, or extreme ultraviolet light; and developing the exposed resist film using a developer.

5. 5. The pattern forming method according to claim 4, wherein the developer is an organic solvent.

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