Method for forming negative resist pattern

Abstract

The invention relates to a negative resist pattern forming method. The invention provides a method for forming a negative resist pattern, which uses a non-chemically amplified resist composition having excellent sensitivity and resolution in lithography using high-energy rays. A negative resist pattern forming method includes: (i) a step of forming a resist film on a substrate using a resist composition including a hypervalent iodine compound, a carboxyl group-containing polymer, and a solvent; (ii) a step for exposing the resist film with a high-energy ray; and (iii) a step for developing the exposed resist film using a developer solution that dissolves the unexposed part but does not dissolve the exposed part.

Description

Technical Field

[0001] The present invention relates to a method for forming a negative resist pattern. Background Art

[0002] As the IoT market expands, demands for higher integration, higher speed, and lower power consumption in LSIs are increasing, leading to a rapid increase in the miniaturization of patterning. Logic devices, in particular, are driving miniaturization. As the most advanced miniaturization technology, mass production of 10nm node devices using double, triple, and quadruple patterning using ArF immersion lithography is underway, and research is already underway on next-generation 7nm node devices using extreme ultraviolet (EUV) lithography with a wavelength of 135nm.

[0003] As miniaturization progresses, image blurring caused by acid diffusion becomes a problem (Non-Patent Document 1). To ensure resolution of fine patterns below 45 nm, it has been proposed that controlling acid diffusion is important, in addition to improving the dissolution contrast as discussed in the prior art (Non-Patent Document 2). However, chemically amplified resist compositions improve sensitivity and contrast through acid diffusion. Therefore, reducing the post-exposure bake (PEB) temperature or shortening the PEB time to minimize acid diffusion significantly reduces sensitivity and contrast.

[0004] Adding an acid generator that generates a bulky acid to suppress acid diffusion is effective. Therefore, some have proposed copolymerizing an acid generator containing an onium salt of a polymerizable olefin in a polymer. However, in patterning resist films with a size of 16 nm or less, chemically amplified resist compositions are believed to be incapable of forming patterns due to acid diffusion, leading to a desire for the development of non-chemically amplified resist compositions.

[0005] Materials used in non-chemically amplified resist compositions include polymethyl methacrylate (PMMA). PMMA is a positive resist material whose main chain is cut by EUV irradiation, reducing its molecular weight and thus increasing its solubility in organic solvents.

[0006] Hydrogen silsesquioxane (HSQ) is a negative-tone resist material that becomes insoluble in alkaline developers through crosslinking caused by the condensation reaction of silanols generated by EUV irradiation. Chloro-substituted calixarenes also function as negative-tone resist materials. These negative-tone resist materials exhibit minimal edge roughness and very high resolution due to their small molecular size before crosslinking and the absence of blurring caused by acid diffusion. These materials are used as pattern transfer materials to achieve the resolution limit of exposure equipment. However, these materials suffer from insufficient sensitivity, and further improvement is needed.

[0007] The main reason why the development of materials for EUV lithography has become difficult is the low number of photons in EUV exposure. The energy of EUV is much higher than that of ArF excimer laser, and the number of photons in EUV exposure is 1 / 14 of the number of photons in ArF exposure. In addition, the size of the pattern formed by EUV exposure is less than half of that of ArF exposure. Therefore, EUV exposure is easily affected by the deviation of the number of photons. The variation in the number of photons in the range of extremely short wavelength radiation is shot noise, a physical phenomenon, and its influence cannot be eliminated. Therefore, the so-called probability theory (Stochastics) has attracted attention. Although the influence of shot noise cannot be eliminated, how to reduce this influence is being discussed. Not only do the dimensional uniformity (CDU) and line width roughness (LWR) increase due to the influence of shot noise, but the phenomenon of hole clogging is observed with a probability of one in millions. Therefore, if the hole is blocked, a conduction failure occurs, and the transistor does not operate, which has a negative impact on the performance of the entire device. Considering practical sensitivity, resist compositions containing PMMA or HSQ as main components are evaluated to be significantly affected by probability theory and cannot achieve the desired resolution performance.

[0008] As a method for reducing the effects of shot noise on the resist side, the introduction of elements with strong absorption of EUV light has attracted attention. Patent Document 1 proposes a chemically amplified resist composition containing iodine atoms with strong EUV absorption. However, as mentioned above, this chemically amplified resist composition cannot achieve excellent resolution performance in EUV lithography, which is expected to achieve increasingly finer dimensions.

[0009] Patent Document 2 proposes a negative-type resist composition using a tin compound. Because it has high EUV light absorption and is primarily composed of tin, it exhibits improved optical properties and can achieve high sensitivity and resolution. However, this metal resist suffers from numerous issues, including insufficient solubility in resist solvents, storage stability, and defects caused by post-etching residue.

[0010] In contrast, Patent Document 3 proposes a positive resist composition using a high-valent iodide. Because it contains iodine, which has a high absorption capacity for EUV light, it improves the probability theory similar to metal resists, enabling high sensitivity and high resolution. Furthermore, because it is composed solely of organic molecules, it can improve the developer solubility and residue-induced defects that are issues with metal resists. However, resist compositions used in photolithography include positive types that dissolve the exposed portion to form a pattern and positive types that retain the exposed portion to form a pattern. The easier-to-use option is selected depending on the desired resist pattern. Since this resist composition is positive, it cannot be used when the desired pattern is negative.

[0011] Prior art literature

[0012] Patent Literature

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-5224

[0014] [Patent Document 2] Japanese Patent Publication No. 2021-503482

[0015] [Patent Document 3] Japanese Patent Application Laid-Open No. 2023-167368

[0016] [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-180928

[0017] [Patent Document 5] Japanese Patent Application Laid-Open No. 2018-95853

[0018] Non-patent literature

[0019] [Non-Patent Document 1] SPIE Vol. 5039 p1 (2003)

[0020] [Non-Patent Document 2] SPIE Vol. 6520p65203L-1 (2007) Summary of the Invention

[0021] [Problems to be Solved by the Invention]

[0022] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a negative resist pattern forming method using a non-chemically amplified resist composition having excellent sensitivity and resolution in lithography using high-energy rays, particularly electron beam (EB) lithography and EUV lithography.

[0023] [Means for solving the problem]

[0024] The present inventors have conducted intensive research to achieve the above-mentioned objectives and have discovered that by combining a resist composition comprising a high-valent iodine compound having at least two acyloxy groups and a carboxyl-containing polymer as main components with an appropriate developer, a negative resist pattern having extremely high sensitivity and excellent resolution can be obtained, which is extremely effective for precise microfabrication, thereby completing the present invention.

[0025] That is, the present invention provides the following negative resist pattern forming method.

[0026] 1. A method for forming a negative resist pattern, comprising the following steps:

[0027] (i) forming a resist film on a substrate using a resist composition comprising a hypervalent iodine compound, a carboxyl group-containing polymer, and a solvent;

[0028] (ii) exposing the resist film to high-energy radiation;

[0029] (iii) The exposed resist film is developed using a developer that dissolves the unexposed portion but does not dissolve the exposed portion.

[0030] 2. The negative resist pattern forming method according to 1., wherein the developer is an alkaline developer.

[0031] 3. The negative resist pattern forming method according to 1. or 2., wherein the high-energy ray is an electron beam or extreme ultraviolet light.

[0032] 4. The negative resist pattern forming method according to any one of 1. to 3., wherein the hypervalent iodine compound is represented by the following formula (1):

[0033] [Chemistry 1]

[0034]

[0035] Wherein, n is an integer from 0 to 5,

[0036] 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, and R 1 and R 2 can 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,

[0037] R 3 is a halogen atom or a hydrocarbon group having 1 to 40 carbon atoms which may also contain heteroatoms. When n is 2 to 5, each R 3 They can be the same or different from each other.

[0038] 5. The negative resist pattern forming method according to any one of 1. to 4., wherein the carboxyl group-containing polymer comprises a repeating unit represented by the following formula (2):

[0039] [Chemistry 2]

[0040]

[0041] Where R A is a hydrogen atom, a halogen atom, a methyl group or a trifluoromethyl group,

[0042] X A is a single bond, phenylene, naphthylene or *-C(=O)-OX A1 -, X A1 is a saturated alkylene group, phenylene group or naphthylene group having 1 to 10 carbon atoms, and 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, but R A When X is methyl, ANot a single key.

[0043] 6. The negative resist pattern forming method according to any one of 1. to 5., wherein the resist composition further comprises a cross-linking agent.

[0044] 7. The negative resist pattern forming method according to any one of 1. to 6., wherein the resist composition further comprises a radical scavenger.

[0045] [Effects of the Invention]

[0046] The negative resist pattern forming method of the present invention is extremely useful for forming fine patterns, particularly in EB lithography and EUV lithography, in which both high sensitivity and high resolution are achieved. DETAILED DESCRIPTION

[0047] [Resist composition]

[0048] The resist composition used in the negative resist pattern forming method of the present invention comprises: a hypervalent iodine compound having at least two acyloxy groups, a carboxyl group-containing polymer, and a solvent.

[0049] [Hypervalent iodine compounds]

[0050] Hypervalent iodide is a general term for iodides having valence electrons that formally exceed the octet rule. The hypervalent iodide used in the present invention is not particularly limited as long as it has at least two acyloxy groups. Examples include tricoordinate iodides with an oxidation number of +3 and pentacoordinate iodides with an oxidation number of +5.

[0051] As the aforementioned hypervalent iodine compound, a tricoordinate hypervalent iodine compound represented by the following formula (1) is preferred.

[0052] [Chemistry 3]

[0053]

[0054] In formula (1), n ​​is an integer of 0 to 5.

[0055] 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 2They may also be bonded to each other and form a ring together with the carbon to which they are bonded and the carbon between them. Specific examples of the above-mentioned halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc. The aforementioned hydrocarbon groups 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 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 propenyl; 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 above 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 above hydrocarbon groups may be substituted by groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms. 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 R 2 A hydrocarbon group having 1 to 4 carbon atoms is preferred.

[0056] In formula (1), R 3 is a halogen atom or a hydrocarbon group having 1 to 40 carbon atoms which may also contain heteroatoms. When n is 2 to 5, each R 3 They may be the same as each other, and they may be different. Specific examples of the above-mentioned halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, and the like. The above-mentioned hydrocarbon groups having 1 to 40 carbon atoms may be saturated or unsaturated, and may be any of linear, branched, and cyclic. Specific examples thereof 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, some or all of the hydrogen atoms of the above hydrocarbon groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- of the above hydrocarbon groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms. 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 included.

[0057] Specific examples of the hypervalent iodine compound represented by formula (1) include the following compounds, but are not limited thereto.

[0058] [Chemistry 4]

[0059]

[0060] [Chemistry 5]

[0061]

[0062] [Chemistry 6]

[0063]

[0064] [Chemistry 7]

[0065]

[0066] [Chemistry 8]

[0067]

[0068] [Chemistry 9]

[0069]

[0070] [Carboxyl group-containing polymer]

[0071] The carboxyl group-containing polymer preferably comprises a carboxyl group-containing repeating unit. As the carboxyl group-containing repeating unit, a carboxyl group-containing repeating unit represented by the following formula (2) is preferred.

[0072] [Chemistry 10]

[0073]

[0074] In formula (2), R A is a hydrogen atom, a halogen atom, a methyl group or a trifluoromethyl group. A represents a single bond, phenylene, naphthylene or *-C(=O)-OX A1-.X A1 is a saturated alkylene group, phenylene group or naphthylene group having 1 to 10 carbon atoms, and 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. A When X is methyl, A Not a single key.

[0075] Specific examples of the aforementioned carboxyl-containing repeating units include but are not limited to the following examples. In the following formula, R A Same as above.

[0076] [Chemistry 11]

[0077]

[0078] [Chemistry 12]

[0079]

[0080] The aforementioned carboxyl-containing polymer may further include 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, but are preferably repeating units that can improve the solubility of the polymer in a solvent that is poorly soluble only by the repeating units having carboxyl groups. As such repeating units, it is preferred that the repeating units be repeating units having a hydrocarbon group having 1 to 20 carbon atoms that may include 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.

[0081] Specific examples of the aforementioned other repeating units include the following repeating units, but are not limited thereto. A Same as above.

[0082] [Chemistry 13]

[0083]

[0084] [Chemistry 14]

[0085]

[0086] [Chemistry 15]

[0087]

[0088] [Chemistry 16]

[0089]

[0090] [Chemistry 17]

[0091]

[0092] [Chemistry 18]

[0093]

[0094] [Chemistry 19]

[0095]

[0096] [Chemistry 20]

[0097]

[0098] [Chemistry 21]

[0099]

[0100] [Chemistry 22]

[0101]

[0102] [Chemistry 23]

[0103]

[0104] [Chemistry 24]

[0105]

[0106] [Chemistry 25]

[0107]

[0108] [Chemistry 26]

[0109]

[0110] [Chemistry 27]

[0111]

[0112] In the carboxyl-containing polymer, the content ratio (molar ratio) of the carboxyl-containing repeating unit and other repeating units is preferably carboxyl-containing repeating unit:other repeating unit=10:90-90:10, more preferably 15:85-85:15, further preferably 20:80-80:20.

[0113] The weight average molecular weight (Mw) of the carboxyl group-containing polymer is preferably 1000 to 500000, more preferably 3000 to 100000. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0114] Furthermore, when 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 impurities being observed in the pattern after exposure, or the pattern shape may be degraded. Therefore, as pattern patterns become increasingly finer, the influence of Mw and Mw / Mn tends to increase. Therefore, in order to obtain a resist composition suitable for fine pattern sizes, the carboxyl group-containing polymer preferably has a narrow Mw / Mn distribution of 1.0 to 2.0.

[0115] Examples of a method for synthesizing the carboxyl group-containing polymer include a method in which a monomer providing the repeating unit is added to an organic solvent with a radical polymerization initiator and then heated to polymerize the monomer.

[0116] 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), 2,2-azobis(2-methylpropionic acid) dimethyl ester, 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.

[0117] The above-mentioned polymerization initiator can be added to the above-mentioned monomer solution and supplied to the reactor, or it can be prepared separately from the above-mentioned monomer solution to prepare the starting aqueous solution and independently supply it to the reactor. Since it is possible to carry out polymerization reaction and generate ultrahigh molecular weight bodies due to the free radicals generated from the initiator during the standby time, it is better to prepare the monomer solution and the initiator solution independently and add them dropwise from the perspective of quality management. The acid-labile group can be directly used as the group introduced into the monomer, or it can be protected or partially protected after polymerization. In addition, in order to adjust the molecular weight, it is also possible to use known chain transfer agents such as dodecanethiol and 2-mercaptoethanol. In this case, the addition amount of these chain transfer agents is preferably 0.01 to 20 mol% relative to the total amount of the monomers to be polymerized.

[0118] In addition, the amount of each monomer in the monomer solution may be appropriately set so as to achieve, for example, an ideal content ratio of the repeating unit.

[0119] In the resist composition, the hypervalent iodine compound and the carboxyl group-containing polymer are preferably contained in a molar ratio of the hypervalent iodine compound to the carboxylic acid-containing repeating units in the polymer of 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. The hypervalent iodide 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.

[0120] [Solvent]

[0121] The aforementioned resist composition contains a solvent. The aforementioned solvent is not particularly limited as long as it can dissolve the high-valent iodine compound, the carboxyl-containing polymer and the following other components to 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 ether. 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.

[0122] In the resist composition, 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. It should be noted that, in the present invention, the term "solids" collectively refers to all components of the resist composition excluding the solvent. The solvents may be used alone or as a mixture of two or more.

[0123] [Other ingredients]

[0124] The resist composition may further include a surfactant. As the surfactant, a fluorine-based and / or polysilicone-based surfactant is preferred. Specific examples of such surfactants include the surfactants described in paragraph

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

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

[0125] When the resist composition contains the surfactant, the content thereof 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.

[0126] The resist composition may further include a radical scavenger. By adding the radical scavenger, the photoreaction in the photolithography process can be controlled and the sensitivity can be adjusted.

[0127] Specific examples of the above-mentioned free radical scavengers include hindered phenols, quinones, hindered amines, and thiol compounds. Specific examples of hindered phenols include butylated hydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Specific examples of quinones include 4-methoxyphenol (p-methoxyphenol) and hydroquinone. Specific examples of hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidinium-N-oxide. Specific examples of thiols include dodecyl mercaptan and hexadecyl mercaptan.

[0128] When the resist composition 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.

[0129] The resist composition may further include a crosslinking agent. By adding the crosslinking agent, the photoreaction in photolithography can be promoted to increase the sensitivity of the resist.

[0130] As a specific example of the above-mentioned cross-linking agent, compounds having carbon-carbon unsaturated groups such as vinyl, (meth) acrylate, allyl, alkynyl, and aromatic ring as functional groups can be listed. Specifically, as a specific example of the compound with vinyl, chain olefins, branched olefins, cyclic olefins, etc. that can have substituents can be listed. As a specific example of the compound with (meth) acrylate, acrylic acid, methacrylic acid, acrylate, methacrylate, etc. that can have substituents can be listed. As a specific example of the compound with allyl, allyl alcohol, allyl ether, allyl ester, acrylamide, allylamine, isocyanurates containing allyl, etc. that can have substituents can be listed. As a specific example of the compound with alkynyl, alkynyl alcohol, alkynyl ether, alkynyl ester, alkynamide, alkynamine, isocyanurates containing alkynyl, etc. that can have substituents can be listed. Specific examples of compounds having an aromatic ring include aromatic hydrocarbons, heteroaromatic hydrocarbons, styrene, stilbene, phenylacetylene, acenaphthylene, and chalcone, which may have a substituent. The crosslinking agent may have only one of the above functional groups, or may have multiple functional groups. The number of the functional groups contained in the crosslinking agent is 1 or more and 10 or less, more preferably 2 or more and 8 or less.

[0131] When the resist composition contains the crosslinking agent, its content is preferably 0.01 to 50% by mass based on the total solid content. The crosslinking agent may be used alone or in combination of two or more.

[0132] The resist composition contains a hypervalent iodide and a carboxyl-containing polymer as its main components, but does not contain a base polymer containing an acid-labile group or a photoacid generator, as is common in known chemically amplified resist compositions. However, the resist composition can form a negative-tone pattern, particularly by EB or EUV exposure, rendering the exposed portion insoluble in the developer. The mechanism for this is not fully understood, but the following is a hypothesis, for example.

[0133] The aforementioned hypervalent iodide is an iodide with at least two acyloxy groups. It is believed that by mixing such a hypervalent iodide with a carboxylic acid, an exchange of carboxylate ligands occurs in an equilibrium reaction. At this time, if the original carboxylate ligand can be removed by a certain method, a hypervalent iodide with a new ligand is generated. For example, iodobenzene diacetate, which is relatively easy to obtain as a hypervalent iodide, is mixed with a carboxylic acid with a large molecular weight, and the low-boiling acetic acid produced is removed, then ligand exchange is completed. Here, when the carboxylic acid compound is a polymer, the polymer becomes a high-molecular-weight hypervalent iodine compound cross-linked by the hypervalent iodine compound.

[0134] Polymers cross-linked with hypervalent iodide are formed during film formation. Even if these cross-linked polymers are pre-synthesized, they are insoluble in most organic solvents, making it impossible to prepare a solution. This is presumably because the solubility of hypervalent iodide, which is inherently low due to its high polarization, is further reduced by the use of high-molecular-weight carboxylic acid-containing polymers as ligands. Therefore, it is ideal to remove the original low-molecular-weight carboxylic acid components during film formation and the subsequent baking step, completing the ligand exchange reaction and simultaneously forming the resist film.

[0135] The resist film obtained from the above-mentioned resist composition comprises polymers cross-linked by hypervalent iodide generated during the film formation process. These polymers typically have low solubility, but when used in specific solvents such as alkaline aqueous solutions, they exhibit very high solubility due to ligand exchange reactions of the hypervalent iodide. However, these polymers decompose under the influence of light, transforming into chemical substances with low solubility in these solvents. As a result, the exposed portions become insoluble in the developer, presumably functioning as a negative-working resist composition.

[0136] Based on the above speculation, the resist composition is a non-chemically amplified resist composition and does not require a polymer containing acid-labile groups or a photoacid generator, as is the case with conventional chemically amplified resist compositions. Therefore, adverse effects caused by acid diffusion (e.g., image blurring) are avoided, enabling resolution of fine patterns.

[0137] This resist composition is particularly effective in EUV lithography. This is due to the presence of iodine atoms, which have a high absorption capacity for EUV light. This reduces shot noise, achieving higher resolution and lower LWR.

[0138] As an EUV resist composition capable of forming fine patterns, some people have reported using a metal resist (e.g., Patent Document 2) having a metal tin compound having a high absorption capacity for EUV light as the main component, similar to iodine atoms. However, as mentioned above, this metal resist has many problems, such as insufficient solubility in solvents, storage stability, and defects caused by residues after etching due to the inclusion of metal elements. On the other hand, since the aforementioned resist composition does not use metal elements, it is more advantageous than metal resist in terms of defects and has no problem with solubility in solvents. Due to these viewpoints, the aforementioned resist composition is more advantageous than metallic resist.

[0139] Patent documents 4 and 5 describe resist compositions containing hypervalent iodine compounds as additives and resist compositions in which hypervalent iodine compounds are introduced into the polymer backbone of a base polymer. However, in these patent documents, as the characteristics of the resist compositions, only the ability to improve line edge roughness is described, and the possibility of photolysis of the hypervalent iodine compound, or the possibility of the material of the non-chemically amplified resist composition functioning, is not mentioned at all. Furthermore, according to the description and specific examples of the admixture amount, the hypervalent iodide is not a main component. In addition, patent document 3 proposes a positive resist composition using a hypervalent iodide, but does not mention the possibility of the resist composition being able to function as a negative resist by combining it with an appropriate developer. Therefore, based on these documents, it is believed that a negative resist pattern forming method that can reduce shot noise in EUV lithography and can form fine patterns as a non-chemically amplified resist, as in the present invention, would not be expected. That is, the present invention clearly provides a novel negative resist pattern forming method.

[0140] [Negative Resist Pattern Formation Method]

[0141] The negative resist pattern forming method of the present invention comprises: (i) forming a resist film on a substrate using the resist composition; (ii) exposing the resist film to high-energy radiation; and (iii) developing the exposed resist film with a developer so as to dissolve the unexposed portions but not the exposed portions.

[0142] [Step (i)]

[0143] Step (i) is a step of forming a resist film on a substrate using the aforementioned resist composition. Specifically, the aforementioned resist composition is applied to a substrate (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective film, etc.) for integrated circuit manufacturing or a substrate (Cr, CrO, CrON, MoSi2, SiO2) for mask circuit manufacturing by an appropriate 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 film is then pre-baked 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.

[0144] [Step (ii)]

[0145] Step (ii) is a step of exposing the resist film to high-energy radiation. Specific examples of the high-energy radiation include ultraviolet radiation, far ultraviolet radiation, EB, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, synchrotron radiation, and the like. When ultraviolet radiation, far ultraviolet radiation, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, synchrotron radiation, and the like are used as the high-energy radiation, the exposure is preferably 1 to 300 mJ / cm2, either directly or through a mask for forming a target pattern. 2 About 10-200 mJ / cm 2 When EB is used as the high energy beam, the exposure dose is preferably 0.1 to 2000 μC / cm2, either directly or using a mask for forming a target pattern. 2 About 0.5 to 1500 μC / cm 2 It should be noted that the resist composition is particularly suitable for fine patterning using EB or EUV among high-energy rays.

[0146] After exposure, PEB needs to be performed. In this case, it is preferably performed 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.

[0147] [Step (iii)]

[0148] Step (iii) is a step of developing the exposed resist film after exposure or PEB using a developer that dissolves the unexposed portion but does not dissolve the exposed portion. In the present invention, a negative resist pattern can be obtained by development. The developer used at this time is not particularly limited as long as it dissolves the unexposed portion but does not dissolve the exposed portion. As such a solvent, an alkaline developer is preferred, and specific examples thereof include aqueous solutions of quaternary ammonium salts, ammonia, primary amines, secondary amines, tertiary amines, inorganic bases, etc. As the above-mentioned alkaline developer, an aqueous solution of a quaternary ammonium salt represented by tetramethylammonium hydroxide is preferred, and an aqueous solution with an alkali concentration of 0.1 to 20% by mass is more preferred. An appropriate amount of surfactant or alcohol may also be added to the aforementioned developer. In addition, these developers may be used alone or in combination of two or more.

[0149] After development, rinsing is performed as needed. A solvent that is miscible with the developer and does not dissolve the resist film is preferably used as the rinse solution. Preferred solvents include alcohols with 3 to 10 carbon atoms, ether compounds with 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents with 6 to 12 carbon atoms.

[0150] By performing rinsing, the collapse of the resist pattern and the generation of defects can be reduced. In addition, rinsing is not essential, and by not performing rinsing, the amount of solvent used can be reduced.

[0151] Example

[0152] Hereinafter, the present invention will be specifically described with reference to synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples.

[0153] [1] Synthesis of polymers

[0154] The monomers used in the synthesis of the polymer are as described below.

[0155] [Chemistry 28]

[0156]

[0157] [Chemistry 29]

[0158]

[0159] [Chemistry 30]

[0160]

[0161] [Synthesis Example 1] Synthesis of Polymer P-1

[0162] Under a nitrogen atmosphere, monomer a-1 (47 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. Under a nitrogen atmosphere, 55 g of MEK was placed in another flask and heated to 80°C while stirring, and then the above-mentioned monomer-polymerization initiator solution was added dropwise over 4 hours. After the addition was completed, stirring was continued 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 4000 g of vigorously stirred hexane, and the precipitated polymer was separated by filtration. The obtained polymer was washed twice with hexane (1200 g) and then vacuum dried at 50°C for 20 hours to obtain polymer P-1 as a white powder (yield 146 g, yield 96%). The Mw of polymer P-1 was 6600 and the Mw / Mn was 1.80. In addition, Mw is a polystyrene conversion measurement value obtained by GPC using THF as a solvent.

[0163] [Chemistry 31]

[0164]

[0165] [Synthesis Examples 2 to 10] Synthesis of Polymers P-2 to P-10

[0166] The polymers shown in Table 1 below were synthesized by the same method as in Synthesis Example 1 except that the types and blending ratios of the monomers were changed.

[0167] [Table 1]

[0168]

[0169]

[0170] [2] Preparation of resist composition

[0171] [Examples 1-1 to 1-15, Comparative Examples 1-1 to 1-2]

[0172] With the composition shown in Table 2 below, the hypervalent iodine compound, polymer, radical scavenger and cross-linking agent were dissolved in a solvent comprising a surfactant (PF-636, Omnova company system) of 0.01 mass %, and the resulting solution was filtered with a 0.2 μm Teflon (registered trademark) filter to prepare resist compositions (R-01 to R-15). In addition, with the composition shown in Table 3 below, the polymer, photoacid generator and sensitivity modifier were dissolved in a solvent comprising a surfactant (PF-636, Omnova company system) of 0.01 mass %, and the resulting solution was filtered with a 0.2 μm Teflon (registered trademark) filter to prepare comparative resist compositions (CR-01 to CR-02).

[0173] [Table 2]

[0174]

[0175]

[0176] [Table 3]

[0177]

[0178] In Tables 2 and 3, the hypervalent iodine compound (I-1 to I-3), the photoacid generator PAG-1, the sensitivity adjuster Q-1, the radical scavenger T-1, the crosslinking agent L-1 and the solvent are as described above.

[0179] [Chemistry 32]

[0180]

[0181] [Chemistry 33]

[0182]

[0183] [Chemistry 34]

[0184]

[0185] [Chemistry 35]

[0186]

[0187] [Chemistry 36]

[0188]

[0189] Solvent: PGMEA (propylene glycol monomethyl ether acetate)

[0190] AcOH (acetic acid)

[0191] HBM (2-hydroxyisobutyric acid methyl ester)

[0192] PA (propionic acid)

[0193] GBL (γ-butyrolactone)

[0194] [3]EUV lithography evaluation (line and space patterning)

[0195] [Examples 2-1 to 2-15, Comparative Examples 2-1 to 2-2]

[0196] Each resist composition (R-01 to R-15, CR-01 to CR-02) 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 4 to form a 40 nm thick resist film. The resist film was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90° dipole illumination) in a 36 nm line-to-space (LS) pattern of 1:1. PEB was performed on a 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, forming a negative-tone LS pattern with a space width of 18 nm and a pitch of 36 nm.

[0197] The obtained resist pattern was evaluated as follows. The results are shown in Table 4.

[0198] [Sensitivity evaluation]

[0199] The LS pattern was observed using a Hitachi Advanced Technologies Co., Ltd.-made CG-6300 SEM to determine the optimal exposure dose Eop (mJ / cm2) for an LS pattern with a spacing width of 18 nm and a pitch of 36 nm. 2 ) and use it as the sensitivity.

[0200] [LWR evaluation]

[0201] The LS pattern obtained by irradiation at the optimal exposure dose was measured at 10 locations along the length of the pitch width using a Hitachi Advanced Technologies Co., Ltd. length measurement SEM (CG-6300). The LWR (nm) was calculated as three times the standard deviation (σ) (3σ). The smaller this value, the less roughness and the more uniform the pitch width.

[0202] [Limiting resolution evaluation]

[0203] Using a Hitachi Advanced Technologies Co., Ltd. long-range scanning electron microscope (CG-6300), the line width (nm) at which resolution can be achieved when gradually increasing the exposure dose from the optimal exposure dose for forming the LS pattern was determined. This value was taken as the limiting resolution (nm). A smaller value indicates better limiting resolution, enabling finer pattern formation.

[0204] [Table 4]

[0205]

[0206] Developer: nBA (butyl acetate)

[0207] TMAH (2.38 mass% tetramethylammonium hydroxide aqueous solution)

[0208] The results shown in Table 4 indicate that the negative resist pattern forming method of the present invention can form a negative resist pattern having excellent sensitivity, LWR, and resolution in LS pattern formation by EUV exposure.

[0209] [4] EUV lithography evaluation (pillar pattern)

[0210] [Examples 3-1 to 3-15, Comparative Examples 3-1 to 3-2]

[0211] Each resist composition (R-01 to R-15, CR-01 to CR-02) was spin-coated onto a Si substrate having a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (Si content: 43 mass%) manufactured by Shin-Etsu Chemical Co., Ltd., formed thereon. PAB was then performed for 60 seconds using a hot plate at the temperature listed in Table 5 to produce a 50 nm thick resist film. Next, the resist film was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadrupole illumination, and a mask with a pillar pattern having a wafer size of 64 nm pitch and +20% bias). PEB was then performed for 60 seconds on a hot plate at the temperature listed in Table 5. Development was then performed for 30 seconds using the developer listed in Table 5 to produce a pillar pattern having a size of 32 nm.

[0212] The obtained resist pattern was evaluated as follows. The results are shown in Table 5.

[0213] [Sensitivity evaluation]

[0214] The column pattern was observed using a Hitachi Advanced Technologies Co., Ltd.-made long-range SEM (CG-6300) to determine the optimal exposure dose Eop (mJ / cm) for a column pattern with a size of 22 nm. 2 ) and use it as the sensitivity.

[0215] [CDU Evaluation]

[0216] The dimensions of 50 pillar patterns obtained by irradiation at the optimal exposure dose were measured, and the value (3σ) tripled from the standard deviation (σ) calculated from the results was used as CDU (nm). The smaller this value, the more uniform the pillar diameter pattern was.

[0217] [Limiting resolution evaluation]

[0218] Using a Hitachi Advanced Technologies Co., Ltd. long-range scanning electron microscope (CG-6300), the limiting pillar diameter (nm) at which the pillar pattern can be resolved was determined by gradually decreasing the exposure dose from the optimal exposure dose for forming the pillar pattern. This value was taken as the limiting resolution (nm). A smaller value indicates better limiting resolution, and patterns with finer pillar diameters can be formed.

[0219] [Table 5]

[0220]

[0221] The results shown in Table 5 show that the negative resist pattern forming method of the present invention can form a negative resist pattern having excellent sensitivity, CDU, and resolution in pillar pattern formation by EUV exposure.

Claims

1. A method for forming a negative resist pattern, comprising the following steps: (i) forming a resist film on a substrate using a resist composition comprising a hypervalent iodine compound, a carboxyl group-containing polymer, and a solvent; (ii) exposing the resist film to high-energy radiation; (iii) The exposed resist film is developed using a developer that dissolves the unexposed portion but does not dissolve the exposed portion.

2. The negative resist pattern forming method according to claim 1, wherein The developer is an alkaline developer.

3. The negative resist pattern forming method according to claim 1, wherein The high-energy rays are electron beams or extreme ultraviolet rays.

4. The negative resist pattern forming method according to any one of claims 1 to 3, wherein The hypervalent iodine compound is represented by the following formula (1): Wherein, n is an integer from 0 to 5, 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, and R 1 and R 2 can 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 is a halogen atom or a hydrocarbon group having 1 to 40 carbon atoms which may also contain heteroatoms. When n is 2 to 5, each R 3 They can be the same or different from each other.

5. The negative resist pattern forming method according to any one of claims 1 to 3, wherein The carboxyl group-containing polymer comprises a repeating unit represented by the following formula (2), Where R A is a hydrogen atom, a halogen atom, a methyl group or a trifluoromethyl group, X A is a single bond, phenylene, naphthylene or *-C(=O)-OX A1 -, X A1 is a saturated alkylene group, phenylene group or naphthylene group having 1 to 10 carbon atoms, and 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, but R A When X is methyl, A Not a single key.

6. The negative resist pattern forming method according to any one of claims 1 to 3, wherein The resist composition further includes a cross-linking agent.

7. The negative resist pattern forming method according to any one of claims 1 to 3, wherein The resist composition further includes a radical scavenger.

Images