Resist composition, laminate, and pattern forming method

Abstract

The invention relates to a resist composition, a laminate, and a pattern forming method. The present invention addresses the problem of providing: a non-chemically amplified resist composition having excellent sensitivity and resolution in optical lithography using high-energy rays; a laminated film provided with a resist film obtained from the resist composition; and a pattern forming method using the resist composition. The solution of this problem is a resist composition containing a superatomic bismuth compound, a carboxyl group-containing polymer, and a solvent.

Description

Technical Field

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

[0002] With the expansion of the IoT market, demands for higher integration, higher speed, and lower power consumption in LSIs are increasing, and the miniaturization of pattern patterns is also progressing rapidly. Logic devices, in particular, are leading the way in miniaturization. Among the most advanced miniaturization technologies, mass production of 10nm node devices using double, triple, and quadruple patterning using ArF immersion lithography is already underway, and research is progressing on 7nm node devices using the next-generation extreme ultraviolet (EUV) lithography with a wavelength of 13.5nm.

[0003] As miniaturization progresses, image blurring caused by acid diffusion has become a problem (Non-Patent Document 1). To ensure resolution in fine patterns with processing sizes below 45 nm, some have proposed that controlling acid diffusion is important, not just improving dissolution contrast, as previously advocated (Non-Patent Document 2). However, chemically amplified resist compositions improve sensitivity and contrast through acid diffusion. Therefore, limiting acid diffusion to the limit by lowering the post-exposure bake (PEB) temperature or shortening the PEB time can significantly reduce sensitivity and contrast.

[0004] Adding an acid generator that generates bulky acids to inhibit acid diffusion is effective. For this reason, acid generators that copolymerize onium salts with polymerizable olefins have been proposed. However, in patterning resist films with a process size of 16 nm or less, chemically amplified resist compositions are believed to be incapable of patterning due to acid diffusion, leading to a desire for the development of non-chemically amplified resist compositions.

[0005] Examples of materials used in non-chemically amplified resist compositions include polymethyl methacrylate (PMMA), a positive-tone resist material whose solubility in organic solvent developers is improved by EUV irradiation, as its main chain is cut and its molecular weight is reduced.

[0006] Hydrogen silsesquioxane (HSQ) is cross-linked by the condensation reaction of silanols produced by EUV irradiation, thereby becoming a negative resist material that is insoluble in alkaline developer. Furthermore, chlorine-substituted calixarene also functions as a negative resist material. Because these negative resist materials have a small molecular size before cross-linking and lack blurring due to acid diffusion, they can be used as pattern transfer materials with minimal edge roughness and very high resolution, exhibiting the resolution limit of exposure equipment. However, these materials have insufficient sensitivity and need further improvement.

[0007] The main reason for the difficulty in developing materials for EUV lithography is the low photon count during EUV exposure. EUV energy is much higher than that of ArF excimer lasers, and the photon count during EUV exposure is only one-fourteenth of that during ArF exposure. Furthermore, the size of a pattern formed using EUV exposure is less than half that of an ArF exposure. Therefore, EUV exposure is susceptible to photon count variation. Photon count variation in the extremely short-wavelength emission region is known as shot noise, a physical phenomenon that cannot be eliminated. Consequently, stochastics has attracted attention. While the effects of shot noise cannot be eliminated, how can they be reduced? Shot noise can lead to increased dimensional uniformity (CDU) and line width roughness (LWR), and there is also a one-in-million chance of pore blockage. Blocked pores result in poor conductivity and transistor inoperability, negatively impacting overall device performance. When considering practical sensitivity, resist compositions containing PMMA or HSQ as main components are significantly affected by stochastics and may not achieve the desired resolution.

[0008] As a method for reducing the effects of shot noise in resists, the introduction of elements that strongly absorb EUV light has attracted attention. Patent Document 1 proposes a chemically amplified resist composition containing iodine atoms that strongly absorb EUV light. However, as previously mentioned, chemically amplified resist compositions cannot achieve excellent resolution in EUV lithography, where process dimensions are increasingly miniaturized.

[0009] Patent Document 2 proposes a negative-type resist composition using a tin compound. This composition, which contains tin, a major element with high EUV light absorption, improves stochastics and achieves high sensitivity and resolution. However, such metal resists have numerous issues, including insufficient solubility in resist solvents, insufficient storage stability due to excessive reactivity, and defects caused by post-etching residue.

[0010] Prior art literature

[0011] Patent Literature

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-5224

[0013] [Patent Document 2] Japanese Patent Publication No. 2021-503482

[0014] Non-patent literature

[0015] [Non-Patent Document 1] SPIE Vol. 5039 p1 (2003)

[0016] [Non-Patent Document 2] SPIE Vol. 6520p65203L-1 (2007) Summary of the Invention

[0017] [Problems to be Solved by the Invention]

[0018] The present invention has been made in view of the above-mentioned situation, and its object is to provide a non-chemically amplified resist composition having excellent sensitivity and resolution in optical lithography using high-energy rays, especially electron beam (EB) lithography and EUV lithography, a stacked film having a resist film obtained from the resist composition, and a pattern forming method using the resist composition.

[0019] [Methods for solving the problem]

[0020] As a result of repeated and in-depth research to achieve the aforementioned objectives, the inventors have obtained the following insights, which have led to the completion of the present invention: a resist composition containing a specific bismuth compound and a carboxyl-containing polymer as main components can provide a resist film with extremely high sensitivity and excellent resolution, which is extremely effective in precise microfabrication.

[0021] That is, the present invention provides the following resist composition and pattern forming method.

[0022] 1. A resist composition comprising: a supervalent bismuth compound, a carboxyl group-containing polymer, and a solvent.

[0023] 2. The resist composition according to 1., wherein the supervalent bismuth compound is represented by the following formula (1).

[0024] [Chemistry 1]

[0025]

[0026] In the formula, p, q, and r are each independently an integer of 0 to 5.

[0027] R 1 and R 2 are each independently a halogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain a hetero atom. 1 and R 2 They may also be bonded to each other and to the carbon atoms to which they are bonded and the atoms between the carbon atoms to form a ring.

[0028] R 3 、R 4 and R 5 Each independently represents a halogen atom or a hydrocarbon group having 1 to 40 carbon atoms which may contain a heteroatom.

[0029] 3. The resist composition according to 1. or 2., wherein the carboxyl group-containing polymer comprises a repeating unit represented by the following formula (2).

[0030] [Chemistry 2]

[0031]

[0032] Where R A Each independently represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0033] X A is a single bond, phenylene, naphthylene or *-C(=O)-OX A1 -.X A1 A linear, branched, or cyclic saturated alkylene group, phenylene group, or naphthylene group having 1 to 10 carbon atoms. The saturated alkylene group may contain at least one selected from a hydroxyl group, an ether bond, an ester bond, and a lactone ring. * indicates an atomic bond to a carbon atom in the main chain.

[0034] 4. A laminate comprising: a substrate; and a resist film obtained from the resist composition according to any one of 1. to 3. on the substrate.

[0035] 5. The laminate according to 4., further comprising a resist underlayer film between the substrate and the resist film.

[0036] 6. A pattern forming method comprising the following steps:

[0037] Using the resist composition according to any one of 1. to 3., forming a resist film on a substrate or on a lower layer film of a substrate laminated with the lower layer film,

[0038] exposing the resist film to high-energy radiation, and

[0039] The exposed resist film is developed using a developer.

[0040] 7. The pattern forming method according to 6., wherein the high-energy rays are EB or EUV.

[0041] 8. The pattern forming method according to 6. or 7., wherein the developer dissolves the exposed portion and does not dissolve the unexposed portion.

[0042] 9. The pattern forming method according to 6. or 7., wherein the developer dissolves the unexposed portion and does not dissolve the exposed portion.

[0043] [Effects of the Invention]

[0044] The resist composition of the present invention is particularly useful for forming fine patterns while achieving both high sensitivity and high resolution in EB lithography and EUV lithography. DETAILED DESCRIPTION

[0045] [Resist composition]

[0046] The resist composition of the present invention contains a supervalent bismuth compound and a carboxyl group-containing polymer as main components.

[0047] [Supervalent Bismuth Compounds]

[0048] Supervalent bismuth compounds are a general term for bismuth compounds that formally have valence electrons exceeding the octet rule. Examples of the supervalent bismuth compounds include pentacoordinate bismuth compounds with an oxidation number of +5.

[0049] The aforementioned supervalent bismuth compound is particularly preferably a pentacoordinate supervalent bismuth compound represented by the following formula (1).

[0050] [Chemistry 3]

[0051]

[0052] In formula (1), p, q, and r are each independently an integer of 0 to 5.

[0053] In formula (1), R 1 and R 2 are each independently a halogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain a hetero atom. 1 and R 2 They may also bond to each other and form a ring together with the carbon atoms to which they are bonded and the atoms between the carbon atoms. Specific examples of the aforementioned halogen atoms include: fluorine atom, chlorine atom, bromine atom, iodine atom, etc. The aforementioned hydrocarbon group having 1 to 10 carbon atoms may be saturated or unsaturated, and may be straight-chain, branched, or cyclic. Specific examples thereof include: alkyl groups having 1 to 10 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, tricyclo[5.2.1.0 2,6 ] Cyclic saturated hydrocarbon groups having 3 to 10 carbon atoms, such as decyl and adamantyl; alkenyl groups having 2 to 10 carbon atoms, such as vinyl and allyl; aryl groups having 6 to 10 carbon atoms, such as phenyl and naphthyl; groups obtained by combining them, etc. In addition, part or all of the hydrogen atoms of the aforementioned hydrocarbon groups may be substituted by groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and part of the -CH2- of the aforementioned hydrocarbon groups may be substituted by groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, hydroxyl groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic anhydride (-C(=O)-OC(=O)-), etc. R 1 and R2 It is preferably a hydrocarbon group having 1 to 4 carbon atoms.

[0054] In formula (1), R 3 、R 4 and R 5 Each is independently a halogen atom, or a hydrocarbon group having 1 to 40 carbon atoms which may also contain a heteroatom. Specific examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc. The aforementioned hydrocarbon group having 1 to 40 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 40 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, tricyclo[5.2.1.0 2,6 ] cyclic saturated hydrocarbon groups having 3 to 40 carbon atoms, such as decyl, adamantyl, and adamantylmethyl; aryl groups having 6 to 40 carbon atoms, such as phenyl, naphthyl, and anthracenyl. In addition, part or all of the hydrogen atoms of the aforementioned hydrocarbon groups may be substituted by groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and part of the -CH2- of the aforementioned hydrocarbon groups may be substituted by groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, hydroxyl groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic anhydride (-C(=O)-OC(=O)-), and the like may be contained. When p is 2 to 5, each R 3 They can be the same or different. When q is 2 to 5, each R 4 They can be the same or different from each other. When r is 2 to 5, each R 5 They can be the same or different.

[0055] Specific examples of the supervalent bismuth compound represented by formula (1) include the following, but are not limited thereto.

[0056] [Chemistry 4]

[0057]

[0058] [Chemistry 5]

[0059]

[0060] [Chemistry 6]

[0061]

[0062] [Chemistry 7]

[0063]

[0064] [Carboxyl group-containing polymer]

[0065] The carboxyl group-containing polymer preferably contains a carboxyl group-containing repeating unit. The carboxyl group-containing repeating unit is preferably represented by the following formula (2).

[0066] [Chemistry 8]

[0067]

[0068] In formula (2), R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. A is a single bond, phenylene, naphthylene or *-C(=O)-OX A1 -.X A1 A saturated alkylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, wherein the saturated alkylene group may contain at least one selected from a hydroxyl group, an ether bond, an ester bond, and a lactone ring. * represents an atomic bond to a carbon atom of the main chain.

[0069] Specific examples of the aforementioned carboxyl group-containing repeating unit include, but are not limited to, the following. A Same as above.

[0070] [Chemistry 9]

[0071]

[0072] [Chemistry 10]

[0073]

[0074] The aforementioned carboxyl-containing polymer may further contain repeating units other than the aforementioned carboxyl-containing repeating units (hereinafter also referred to as other repeating units). The aforementioned other repeating units are not particularly limited, and for example, are preferably those that can improve the solubility of a polymer that is poorly soluble in a solvent when it contains only carboxyl-containing repeating units. Such repeating units are preferably repeating units having a hydrocarbon group having 1 to 20 carbon atoms and may also contain at least one of a hydroxyl group other than a phenolic hydroxyl group, a cyano group, a carbonyl group, an ester bond, an ether bond, a thioether bond, a carbonate bond, a lactone ring, and a sultone ring.

[0075] Specific examples of the aforementioned other repeating units include those shown below, but are not limited thereto. A Same as above.

[0076] [Chemistry 11]

[0077]

[0078] [Chemistry 12]

[0079]

[0080] [Chemistry 13]

[0081]

[0082] [Chemistry 14]

[0083]

[0084] [Chemistry 15]

[0085]

[0086] [Chemistry 16]

[0087]

[0088] [Chemistry 17]

[0089]

[0090] [Chemistry 18]

[0091]

[0092] [Chemistry 19]

[0093]

[0094] [Chemistry 20]

[0095]

[0096] [Chemistry 21]

[0097]

[0098] [Chemistry 22]

[0099]

[0100] [Chemistry 23]

[0101]

[0102] [Chemistry 24]

[0103]

[0104] [Chemistry 25]

[0105]

[0106] In the aforementioned carboxyl-containing polymer, the ratio (molar ratio) of the carboxyl-containing repeating unit to other repeating units is preferably carboxyl-containing repeating unit: other repeating unit = 10:90 to 90:10, more preferably 15:85 to 85:15, and even more preferably 20:80 to 80:20.

[0107] The weight average molecular weight (Mw) of the carboxyl 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.

[0108] Furthermore, if the molecular weight distribution (Mw / Mn) of the carboxyl group-containing polymer is relatively broad, low-molecular-weight and high-molecular-weight polymers may be present, leading to the possibility of foreign matter being observed on the pattern after exposure and deterioration of the pattern shape. Therefore, as pattern rules become finer, the influence of Mw and Mw / Mn tends to increase. Therefore, in order to obtain a resist composition ideally suited for fine pattern sizes, the carboxyl group-containing polymer preferably has a narrow Mw / Mn distribution of 1.0 to 2.0.

[0109] Examples of the method for synthesizing the carboxyl group-containing polymer include a method in which a monomer providing the repeating unit is added with a radical polymerization initiator in an organic solvent and heated to polymerize the monomer.

[0110] Specific examples of the organic solvent used in the polymerization reaction include toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), γ-butyrolactone (GBL), etc. 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, lauroyl peroxide, etc. The amount of the polymerization initiator added is preferably 0.01 to 25 mol% relative to the total amount of the 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 perspective of production efficiency.

[0111] The polymerization initiator can be added to the monomer solution and supplied to the reactor, or an initiator solution different from the monomer solution can be prepared and supplied to the reactor separately. Since there is a possibility that the polymerization reaction will proceed and form ultra-high molecular weight bodies due to free radicals generated from the initiator during the waiting time, the monomer solution and the initiator solution should be prepared separately and added dropwise from the perspective of quality control. The acid-labile group can be directly introduced into the monomer, or it can be protected or partially protected after polymerization. In addition, in order to adjust the molecular weight, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol can be used in combination. In this case, the amount of these chain transfer agents added is preferably 0.01 to 20 mol% relative to the total amount of the monomers to be polymerized.

[0112] The amount of each monomer in the monomer solution may be appropriately set, for example, so as to achieve an ideal content ratio of the repeating unit.

[0113] In the resist composition of the present invention, the supervalent bismuth compound and the carboxyl group-containing polymer are preferably contained in the polymer at a molar ratio of 10:90 to 90:10 relative to the carboxylic acid-containing repeating units, preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. The supervalent bismuth compound may be used alone or in combination of two or more. The carboxyl group-containing polymer may be used alone or in combination of two or more having different composition ratios, Mw values, and / or Mw / Mn values.

[0114] [Solvent]

[0115] The resist composition of the present invention contains a solvent. The aforementioned solvent is not particularly limited as long as it can dissolve the aforementioned super-valent bismuth compound, the carboxyl group-containing polymer and other components described later and can form a film. Such a solvent is preferably an organic solvent, and specific 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, 4-methyl-2-pentanol, and methyl 2-hydroxyisobutyrate; propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethyl Ethers such as glycol monoethyl ether, 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.

[0116] In the resist composition of the present invention, the solvent is preferably present in an amount such that the solids concentration in the resist composition is 0.1 to 20% by mass, more preferably 0.1 to 15% by mass, and even more preferably 0.1 to 10% by mass. In the present invention, the term "solids" collectively refers to all components of the resist composition other than the solvent. The solvent may be used alone or as a mixture of two or more.

[0117] [Other ingredients]

[0118] The resist composition of the present invention may further contain a surfactant. The surfactant is preferably a fluorine-based and / or silicone-based surfactant. Specific examples of such surfactants include the surfactants described in paragraph

[0276] of U.S. Patent Application Publication No. 2008 / 0248425. 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.

[0119] When the resist composition of the present invention contains the surfactant, its content is preferably 0.0001 to 2% by mass based on the total solid content. The surfactant may be used alone or in combination of two or more.

[0120] The resist composition of the present invention may further contain a radical scavenger. By adding a radical scavenger, the photoreaction in optical lithography can be controlled and the sensitivity can be adjusted.

[0121] Specific examples of the radical scavenger include hindered phenols, quinones, hindered amines, and thiol compounds. Specific examples of the hindered phenols include butylated hydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Specific examples of the quinones include 4-methoxyphenol (MEHQ) and hydroquinone. Specific examples of the hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidinium-N-oxide. Specific examples of the thiols include dodecanethiol and hexadecanethiol.

[0122] When the resist composition of the present invention contains the radical scavenger, the content thereof is preferably 0.01 to 10% by mass based on the total solid content. The radical scavengers may be used alone or in combination of two or more.

[0123] The resist composition of the present invention contains a supervalent bismuth compound and a carboxyl-containing polymer as main components, but does not contain a base polymer containing acid-labile groups or a photoacid generator, as found in conventional chemically amplified resist compositions. However, the resist composition of the present invention can form a pattern by varying its developer solubility between unexposed and exposed areas, particularly during EB or EUV exposure. The mechanism of this effect is not fully elucidated, but is speculated to be, for example, as follows.

[0124] The aforementioned supervalent bismuth compound is a pentavalent compound formed by bonding an aromatic group to two carboxylate ligands, as represented by formula (1). It is believed that when such a pentavalent bismuth compound is mixed with a carboxyl-containing polymer, an equilibrium reaction will occur, resulting in an exchange of carboxyl ligands. At this time, if the original carboxyl ligand can be removed by any method, a supervalent bismuth compound having new ligands will be generated. For example, if triphenylbismuth diacetate, which is relatively easy to obtain as a supervalent bismuth compound, is mixed with a carboxyl-containing polymer and the generated low-boiling acetic acid is removed, the ligand exchange will be completed. The supervalent bismuth compound after ligand exchange has a polymer component, so it can form a strong resist film.

[0125] Such a bonded product of a supervalent bismuth compound and a carboxyl-containing polymer can be prepared before film formation, but in many cases, it is preferably formed during film formation due to low solvent solubility. Specifically, a mixture of a supervalent bismuth compound monomer and a carboxyl-containing polymer is dissolved in an organic solvent to form a resist solution. This solution is then subjected to a ligand exchange reaction during film formation and in a subsequent baking step, thereby forming a resist film in which the polymer is bonded to the supervalent bismuth compound.

[0126] In the laminate of the present invention, in which a resist film is formed on a substrate in this manner, the hypervalent bismuth compound, the main component of the resist film, decomposes in response to light, causing a change in polarity. This allows for the formation of a pattern during the development step. Furthermore, by appropriately selecting a developer, either positive or negative-tone patterns can be formed.

[0127] Based on the above speculation, the resist composition of the present invention can be described as a non-chemically amplified resist composition. Therefore, the resist composition of the present invention does not suffer from the image blurring caused by acid diffusion observed in conventional chemically amplified resist compositions (compositions containing a base polymer and a photoacid generator), allowing for resolution of fine patterns.

[0128] The resist composition of the present invention is particularly effective in EUV lithography. This is due to the high absorption of EUV light by bismuth atoms. This reduces shot noise, enabling higher resolution and lower LWR.

[0129] With regard to EUV resist compositions that can form fine patterns, there are reports of metal resists (e.g., patent document 2) with metal tin compounds having high absorption capacity for EUV light, similar to bismuth atoms, as main components. However, as mentioned above, such metal resists have problems such as insufficient solubility in solvents and storage stability. On the other hand, the solvent solubility of the resist composition of the present invention is excellent. In addition, the resist composition of the present invention is applicable to either positive or negative types, so its use is wide. For example, in the contact hole formation step, the metal resist implemented with negative development requires an inversion processing step after the column pattern is formed, but the positive resist does not need such a step. Therefore, considering the viewpoint of ease of processing, the resist composition of the present invention can also be said to be more useful than the metal resist.

[0130] [Pattern Formation Method]

[0131] When the resist composition of the present invention is used in the manufacture of various integrated circuits, known photolithography techniques can be employed. For example, a specific example of a pattern forming method includes the following steps: using the resist composition to form a resist film on a substrate or on an underlayer film laminated on a substrate, exposing the resist film to high-energy radiation, and developing the exposed resist film using a developer.

[0132] First, the resist composition of the present invention is applied to a substrate for integrated circuit manufacturing or a substrate with an underlying film (e.g., Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective film), or a substrate for mask circuit manufacturing or a substrate with an underlying film (e.g., Cr, CrO, CrON, MoSi2, SiO2) by a suitable coating method such as spin coating, roller coating, flow coating, dip coating, spray coating, or blade coating to a coating thickness of 0.01 to 2 μm. The resist composition is then pre-baked on a hot plate at a temperature of preferably 60 to 200° C. for 10 seconds to 30 minutes, and more preferably at 80 to 180° C. for 30 seconds to 20 minutes, to form a resist film. The term "underlayer" refers to a film formed between the substrate and the resist film in a multilayer resist process. The aforementioned underlayer is not particularly limited, and known materials may be used.

[0133] Then, the resist film is exposed to high-energy radiation. Specific examples of the high-energy radiation include ultraviolet radiation, extreme ultraviolet radiation, EB, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, and synchrotron radiation. When ultraviolet radiation, extreme ultraviolet radiation, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, and synchrotron radiation are used as the high-energy radiation, the exposure dose is preferably about 1 to 300 mJ / cm2, either directly or through a mask for forming a target pattern. 2More preferably, it is about 10 to 200 mJ / cm 2 When EB is used as high energy ray, it is preferably irradiated with an exposure dose of about 0.1 to 5000 μC / cm2 directly or through a mask for forming the target pattern. 2 More preferably, it is about 0.5 to 4000 μC / cm 2 Furthermore, the resist composition of the present invention is particularly suitable for fine patterning using EB or EUV among high-energy rays.

[0134] After exposure, PEB is performed as needed, preferably on a hot plate or in an oven at 30-120° C. for 10 seconds to 30 minutes, more preferably at 60-100° C. for 30 seconds to 20 minutes.

[0135] After exposure or PEB, patterning is performed using a developer. Specific examples of the developer used at this time include alkaline aqueous solutions such as tetramethylammonium hydroxide aqueous solution or 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, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butyl acetate, isoamyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, 3-ethylhexyl acrylate ... Organic solvents such as ethyl oxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, isoamyl 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, and 4-methyl-2-pentanol can be used. In the present invention, development with an organic solvent forms a positive pattern in which the exposed portion dissolves and the unexposed portion does not dissolve, while development with an alkaline aqueous solution forms a negative pattern in which the unexposed portion dissolves and the exposed portion does not dissolve. These developers can be used alone or in combination of two or more.

[0136] After development, rinsing is performed as needed. The rinsing solution should preferably be a solvent that is miscible with the developer and does not dissolve the resist film. Suitable solvents include alcohols with 3 to 10 carbon atoms, ether compounds with 8 to 12 carbon atoms, alkanes, alkenes, and alkynes with 6 to 12 carbon atoms, and aromatic solvents. Alternatively, water can be used as the rinsing solution in place of the organic solvent.

[0137] By performing rinsing, the occurrence of resist pattern collapse and defects can be reduced. In addition, rinsing is not essential, and by not performing rinsing, the amount of solvent used can be reduced.

[0138] [Example]

[0139] Hereinafter, the present invention will be described in detail with reference to synthesis examples, examples, and comparative examples. However, the present invention is not limited to the following examples.

[0140] [1] Synthesis of polymers

[0141] The monomers used in the synthesis of the polymer are as follows.

[0142] [Chemistry 26]

[0143]

[0144] [Chemistry 27]

[0145]

[0146] [Chemistry 28]

[0147]

[0148] [Synthesis Example 1] Synthesis of Polymer P-1

[0149] Under a nitrogen atmosphere, monomer a-1 (56 g), monomer b-1 (105 g), 5.4 g of V-601 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 180 g of MEK were weighed in a flask to prepare a monomer-polymerization initiator solution. 55 g of MEK was weighed in another flask that had been adjusted to a nitrogen atmosphere, and after heating to 80°C while stirring, the aforementioned monomer-polymerization initiator solution was added dropwise over a period of 4 hours. After the addition was completed, the polymerization solution was stirred continuously for 2 hours while maintaining the temperature of the polymerization solution at 80°C, and then cooled to room temperature. The obtained polymerization solution was added dropwise to vigorously stirred hexane (4000 g), and the precipitated polymer was filtered. The obtained polymer was washed twice with hexane (1200 g) and then vacuum-dried at 50°C for 20 hours to obtain a white powdery polymer P-1 (yield 155 g, yield 96%). The Mw of polymer P-1 was 7700, and the Mw / Mn was 1.82. In addition, Mw is a polystyrene-equivalent measurement value obtained by GPC using THF as a solvent.

[0150] [Chemistry 29]

[0151]

[0152] [Synthesis Examples 2 to 10] Synthesis of Polymers P-2 to P-10

[0153] The polymers shown in the following Table 1 were synthesized in the same manner as in Synthesis Example 1 except that the types and blending ratios of the monomers were changed.

[0154] [Table 1]

[0155]

[0156] [2] Preparation of resist composition

[0157] [Examples 1-1 to 1-16, Comparative Examples 1-1 to 1-3]

[0158] A supervalent bismuth compound and a carboxyl group-containing polymer were dissolved in a solvent according to the composition shown in Table 2 below, and the resulting solution was filtered through a 0.2 μm Teflon (registered trademark) filter to prepare resist compositions (R-01 to R-16). Furthermore, a polymer, a photoacid generator, a sensitivity adjuster, a solvent, and 0.01 mass% of a surfactant (PF-636, manufactured by OMNOVA) were mixed according to the composition shown in Table 3 below, and the mixture was filtered through a 0.2 μm Teflon (registered trademark) filter to prepare comparative resist compositions (CR-01 to CR-03).

[0159] [Table 2]

[0160]

[0161] [Table 3]

[0162]

[0163] In Table 2, the hypervalent bismuth compounds (B-1 to B-3) and the solvents are as follows.

[0164] [Chemistry 30]

[0165]

[0166] Solvent: PGMEA (propylene glycol monomethyl ether acetate)

[0167] HBM (2-hydroxyisobutyric acid methyl ester)

[0168] GBL (γ-butyrolactone)

[0169] In Table 2, the base polymer (BP-1), the photoacid generators (PAG-1, PAG-2), and the sensitivity adjusters (Q-1, Q-2) are as follows.

[0170] [Chemistry 31]

[0171]

[0172] [Chemistry 32]

[0173]

[0174] [Chemistry 33]

[0175]

[0176] [3] EUV lithography evaluation (line and space patterning, positive tone development)

[0177] [Examples 2-1 to 2-12, Comparative Examples 2-1 to 2-3]

[0178] Each resist composition (R-01 to R-12, CR-01 to CR-03) was spin-coated onto a Si substrate having a 20 nm thick film of a Shin-Etsu Chemical Co., Ltd. silicon-containing spin-on hard mask SHB-A940 (silicon content: 43 mass%) formed thereon. The film was then prebaked (PAB) for 60 seconds using a hot plate at the temperature listed in Table 4 to form a 40 nm thick resist film. The resist film was then exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination) to form a 48 nm line-to-space (LS) pattern with a 1:1 ratio. PEB was then performed on the hot plate for 60 seconds at the temperature listed in Table 4, followed by development for 30 seconds using the developer listed in Table 4 to form an LS pattern with a 24 nm line width and a 48 nm pitch.

[0179] The obtained resist pattern was subjected to the following evaluation. The results are shown in Table 4.

[0180] [Sensitivity evaluation]

[0181] The LS pattern was observed using a Hitachi Advanced Technologies Co., Ltd.-made CG-6300 SEM. The optimal exposure dose Eop (mJ / cm2) for obtaining an LS pattern with a pitch width of 24 nm and a pitch of 48 nm was determined. 2 ) and let it be sensitivity.

[0182] [LWR evaluation]

[0183] For the LS pattern obtained with the optimal exposure, the dimensions were measured at 10 locations along the pitch width longitudinal direction using a Hitachi Advanced Technologies Co., Ltd. length measurement SEM (CG-6300). The results were used to calculate the value (3σ) times the standard deviation (σ), and this value was defined as the LWR (nm). The smaller this value, the less roughness and the more uniform the wide-pitch pattern.

[0184] [Limiting resolution evaluation]

[0185] The exposure dose was gradually increased from the optimal exposure dose for forming the LS pattern. Using a Hitachi Advanced Technologies Co., Ltd. long-range scanning electron microscope (CG-6300), the line width (nm) at which resolution was achieved during pattern formation was determined. This value was designated as the limiting resolution (nm). A smaller value indicates better limiting resolution, and finer patterns can be formed.

[0186] [Table 4]

[0187]

[0188] Developer: IPA (isopropyl alcohol)

[0189] TMAH (2.38 mass% tetramethylammonium hydroxide aqueous solution)

[0190] [4] EUV lithography evaluation (line and space patterning, negative tone development)

[0191] [Examples 3-1 to 3-4, Comparative Examples 3-1 to 3-3]

[0192] Each resist composition (R-13 to R-16, CR-01 to CR-03) was spin-coated onto a Si substrate having a 20 nm thick film of a Shin-Etsu Chemical Co., Ltd. silicon-containing spin-on hard mask SHB-A940 (silicon content: 43 mass%) formed thereon. The film was then prebaked (PAB) for 60 seconds using a hot plate at the temperature listed in Table 5 to form a 40 nm thick resist film. The resist film was then exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination) to form a 48 nm line-to-space (LS) pattern with a 1:1 ratio. PEB was then performed on a hot plate for 60 seconds at the temperature listed in Table 5, followed by development for 30 seconds using the developer listed in Table 5 to form an LS pattern with a 24 nm line width and a 48 nm pitch.

[0193] The obtained resist pattern was subjected to the following evaluation. The results are shown in Table 5.

[0194] [Sensitivity evaluation]

[0195] The above pattern was observed using a Hitachi Advanced Technologies Co., Ltd.-made CG-6300 SEM to obtain the optimal exposure dose Eop (mJ / cm2) for obtaining an LS pattern with a pitch width of 24 nm and a pitch of 48 nm. 2 ) and let it be sensitivity.

[0196] [LWR evaluation]

[0197] For the LS pattern obtained with the optimal exposure, the dimensions were measured at 10 locations along the pitch width longitudinal direction using a Hitachi Advanced Technologies Co., Ltd. length measurement SEM (CG-6300). The results were used to calculate the value (3σ) times the standard deviation (σ), and this value was defined as the LWR (nm). The smaller this value, the less roughness and the more uniform the wide-pitch pattern.

[0198] [Limiting resolution evaluation]

[0199] The exposure dose was gradually increased from the optimal exposure dose for forming the LS pattern. Using a Hitachi Advanced Technologies Co., Ltd. long-range scanning electron microscope (CG-6300), the line width (nm) at which resolution was achieved during pattern formation was determined. This value was designated as the limiting resolution (nm). A smaller value indicates better limiting resolution, and finer patterns can be formed.

[0200] [Table 5]

[0201]

[0202] Developer: nBA (butyl acetate)

[0203] The results shown in Tables 4 and 5 indicate that the resist composition of the present invention exhibits excellent sensitivity, LWR, and resolution when forming an LS pattern obtained by EUV exposure, regardless of whether the development is positive-tone or negative-tone.

[0204] [5] EUV lithography evaluation (contact hole pattern)

[0205] [Examples 4-1 to 4-12, Comparative Examples 4-1 to 4-3]

[0206] Each resist composition (R-01 to R-12, CR-01 to CR-03) was spin-coated onto a Si substrate having a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (silicon content: 43 mass%) manufactured by Shin-Etsu Chemical Co., Ltd., formed thereon. The resist film was prebaked (PAB) for 60 seconds using a hot plate at the temperature listed in Table 6 to form a 50 nm thick resist film. The resist film was then exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadrupole illumination, mask with a hole pattern having a 64 nm pitch and a +20% offset on the wafer). PEB was performed on a hot plate for 60 seconds at the temperature listed in Table 6, followed by development for 30 seconds using the developer listed in Table 6 to obtain a hole pattern having a size of 32 nm.

[0207] The obtained resist pattern was subjected to the following evaluation. The results are shown in Table 6.

[0208] [Sensitivity evaluation]

[0209] The contact hole pattern was observed using a Hitachi Advanced Technologies Co., Ltd. long-range SEM (CG-6300) to determine the optimal exposure dose (Eop) (mJ / cm) for obtaining a hole pattern with a size of 32 nm. 2 ) and let it be sensitivity.

[0210] [CD Uniformity (CDU) Evaluation]

[0211] The dimensions of 50 holes in the pattern obtained by irradiation with the optimal exposure dose were measured, and the value (3σ) tripled by the standard deviation (σ) obtained from the results was set as CDU (nm). The smaller this value, the more uniform the hole diameter pattern can be obtained.

[0212] [Limiting resolution evaluation]

[0213] The exposure dose was gradually reduced from the optimal dose for forming the aforementioned hole pattern. Using a Hitachi Advanced Technologies Co., Ltd. long-range SEM (CG-6300), the critical hole diameter (nm) at which the hole pattern could be resolved was determined. This value was designated as the critical resolution (nm). A smaller value indicates better critical resolution, and a pattern with a finer hole diameter can be obtained.

[0214] [Table 6]

[0215]

[0216] The results shown in Table 6 show that the resist composition of the present invention is excellent in sensitivity, CDU, and resolution in forming a contact hole pattern by EUV exposure.

Claims

1. A resist composition comprising: a supervalent bismuth compound, a carboxyl group-containing polymer, and a solvent.

2. The resist composition according to claim 1, wherein The supervalent bismuth compound is represented by the following formula (1): Wherein, p, q and r are each independently an integer from 0 to 5; R 1 and R 2 are independently a halogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain a hetero atom; and R 1 and R 2 They may also bond to each other and to the carbon atoms to which they are bonded and the atoms between the carbon atoms to form a ring; R 3 、R 4 and R 5 Each independently represents a halogen atom or a hydrocarbon group having 1 to 40 carbon atoms which may contain a heteroatom.

3. The resist composition according to claim 1, wherein The carboxyl group-containing polymer is a polymer containing a repeating unit represented by the following formula (2): Where R A each independently represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; X A is a single bond, phenylene, naphthylene or *-C(=O)-OX A1 -;X A1 It is a linear, branched or cyclic saturated alkylene group, phenylene group or naphthylene group having 1 to 10 carbon atoms, and the saturated alkylene group may also contain at least one selected from a hydroxyl group, an ether bond, an ester bond and a lactone ring; * represents an atomic bond to a carbon atom of the main chain. 4 . A laminate comprising: a substrate; and a resist film formed on the substrate and obtained from the resist composition according to claim 1 .

5. The laminate according to claim 4, wherein A resist underlayer film is provided between the substrate and the resist film.

6. A pattern forming method comprising the following steps: forming a resist film on a substrate or on a substrate having an underlayer film laminated thereon using the resist composition according to any one of claims 1 to 3, The resist film is exposed to high energy radiation, and The exposed resist film is developed using a developer.

7. The pattern forming method according to claim 6, wherein: The high-energy rays are electron beams or extreme ultraviolet rays.

8. The pattern forming method according to claim 6, wherein The developer dissolves the exposed portion and does not dissolve the unexposed portion.

9. The pattern forming method according to claim 6, wherein: The developer dissolves the unexposed portion but does not dissolve the exposed portion.

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