Negative resist pattern formation method

Abstract

To provide a negative resist pattern formation method employing a non-chemically amplified resist composition having superior sensitivity and resolution when high-energy radiation is used in photolithography.SOLUTION: A negative resist pattern formation method comprises: (i) a step of forming a resist film on a substrate using a resist composition containing a hypervalent iodine compound, a carboxylic acid compound, and a solvent; (ii) a step of exposing the resist film to high-energy rays; and (iii) a step of developing the exposed resist film with a developer that dissolves the unexposed region but leaves the exposed region undissolved.SELECTED DRAWING: None

Description

[Technical Field]

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

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

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

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

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

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

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

[0008] As a method for reducing the impact of shot noise on the resist side, the introduction of elements that have high absorption of EUV light has attracted attention. Patent Document 1 proposes a chemically amplified resist composition containing iodine atoms that have high absorption of EUV light. However, as mentioned above, chemically amplified resist compositions cannot achieve excellent resolution performance in EUV lithography, which will see increasingly finer dimensions in the future.

[0009] Patent Document 2 proposes a negative resist composition using a tin compound. Because this composition contains tin, which has high absorption of EUV light, as its main component, it improves stochastics and achieves high sensitivity and high resolution. However, this type of metal resist has many issues, including insufficient solubility in resist solvents, storage stability, and defects caused by post-etching residues.

[0010] In response to this, Patent Document 3 proposes a positive resist composition using a hypervalent iodine compound. Because this composition contains iodine, which has high absorption of EUV light, it can achieve improved stochasticity, similar to that of metal resists, and achieve high sensitivity and high resolution. Furthermore, because it is composed solely of organic molecules, it can address issues with metal resists, such as developer solubility and defects caused by residues. However, resist compositions used in photolithography include positive-type resists, which form patterns by dissolving exposed areas, and negative-type resists, which form patterns by leaving exposed areas intact. While the most convenient type is selected depending on the shape of the desired resist pattern, this positive-type resist composition presents a problem in that it cannot be used when the desired pattern is negative. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2018-5224 [Patent Document 2] Special Publication No. 2021-503482 [Patent Document 3] Japanese Patent Application Publication No. 2023-167368 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-180928 [Patent Document 5] Japanese Patent Application Publication No. 2018-95853 [Non-patent literature]

[0012] [Non-Patent Document 1] SPIE Vol. 5039 p1 (2003) [Non-patent document 2] SPIE Vol. 6520 p65203L-1 (2007) Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for forming a negative resist pattern using a non-chemically amplified resist composition that exhibits excellent sensitivity and resolution in photolithography using high-energy rays, particularly electron beam (EB) lithography and EUV lithography. [Means for solving the problem]

[0014] As a result of extensive research into achieving the above-mentioned object, the present inventors have discovered that by combining a resist composition containing as main components a hypervalent iodine compound having at least two acyloxy groups and a carboxylic acid compound with an appropriate developer, a negative resist pattern exhibiting extremely high sensitivity and excellent resolution can be obtained, and this is extremely effective for precise microfabrication, leading to the completion of the present invention.

[0015] That is, the present invention provides the following method for forming a negative resist pattern. 1. (i) forming a resist film on a substrate using a resist composition containing a hypervalent iodine compound, a carboxylic acid compound, and a solvent; (ii) exposing the resist film to high-energy radiation; (iii) developing the exposed resist film using a developer that dissolves the unexposed areas but does not dissolve the exposed areas; A method for forming a negative resist pattern comprising: 2. The method for forming a negative resist pattern according to 1, wherein the developer is an alkaline developer. 3. The method for forming a negative resist pattern according to 1 or 2, wherein the high-energy radiation is EB or EUV. 4. The method for forming a negative resist pattern according to any one of 1 to 3, wherein the hypervalent iodine compound is represented by the following formula (1): [ka] (In the formula, n is an integer of 0 to 5. R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms. R 3 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 to 5, each R 3 may be the same as or different from each other.) 5. The method for forming a negative resist pattern according to any one of 1 to 4, wherein the carboxylic acid compound is represented by the following formula (2): [ka] (In the formula, m is an integer of 1 to 4. R 11 is an m-valent hydrocarbon group having 1 to 40 carbon atoms or an m-valent heterocyclic group having 2 to 40 carbon atoms, and when m is 2, R 11may be an ether bond, a carbonyl group, an azo group, a thioether bond, a carbonate bond, a carbamate bond, a sulfinyl group, or a sulfonyl group. Some or all of the hydrogen atoms in the m-valent hydrocarbon group or m-valent heterocyclic group may be substituted with a group containing a heteroatom, and some of the -CH2- groups in the m-valent hydrocarbon group may be substituted with a group containing a heteroatom. R 12 is a single bond or a hydrocarbylene group having 1 to 10 carbon atoms, and some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a hetero atom, or some of the -CH2- of the hydrocarbylene group may be substituted with a group containing a hetero atom. 12 may be the same as or different from each other.) 6. The method for forming a negative resist pattern according to 5, wherein m is an integer of 2 to 4. 7. The method for forming a negative resist pattern according to any one of 1 to 6, wherein the resist composition further contains a crosslinking agent. 8. The method for forming a negative resist pattern according to any one of 1 to 7, wherein the resist composition further contains a radical scavenger. [Effects of the Invention]

[0016] The method for forming a negative resist pattern of the present invention is extremely useful for achieving both high sensitivity and high resolution, particularly in EB lithography and EUV lithography, and for forming fine patterns. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Resist composition] The resist composition used in the method of forming a negative resist pattern of the present invention contains a hypervalent iodine compound having at least two acyloxy groups, a carboxylic acid compound, and a solvent.

[0018] [Hypervalent iodine compounds] The hypervalent iodine compound is a general term for iodine compounds having valence electrons that formally exceed the octet rule. The hypervalent iodine compound used in the present invention is not particularly limited as long as it has at least two acyloxy groups, and examples thereof include a tricoordinate iodine compound with an oxidation number of +3 and a pentacoordinate iodine compound with an oxidation number of +5.

[0019] The hypervalent iodine compound is preferably a three-coordinate hypervalent iodine compound represented by the following formula (1). [ka]

[0020] In formula (1), n ​​is an integer of 0 to 5.

[0021] In formula (1), R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between the carbon atoms. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 10 carbon atoms may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, and a tricyclo[5.2.1.0 2,6] cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as a decanyl group or an adamantyl group; alkenyl groups having 2 to 10 carbon atoms, such as a vinyl group or an allyl group; aryl groups having 6 to 10 carbon atoms, such as a phenyl group or a naphthyl group; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms, nitrogen atoms, or halogen atoms, and some of the -CH2- groups in the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms, or nitrogen atoms, resulting in the hydrocarbyl groups containing hydroxy groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), etc. 1 and R 2 is preferably a hydrocarbyl group having 1 to 4 carbon atoms.

[0022] In formula (1), R 3 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 to 5, each R 3 may be the same or different. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 40 carbon atoms may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, and a tricyclo[5.2.1.0 2,6cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as a ]decanyl group, an adamantyl group, or an adamantylmethyl group; and aryl groups having 6 to 40 carbon atoms, such as a phenyl group, a naphthyl group, or an anthracenyl group. Some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, or halogen atoms, and some of the -CH2- groups in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, or nitrogen atoms, so that the hydrocarbyl groups may contain hydroxy groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), or the like.

[0023] Specific examples of the hypervalent iodine compound represented by formula (1) include, but are not limited to, the following: [ka]

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] [Carboxylic acid compounds] The carboxylic acid compound used in the present invention may be any carboxylic acid compound generally defined in organic chemistry, but is preferably one represented by the following formula (2). [ka]

[0030] In formula (2), m is an integer of 1 to 4. 11 is an m-valent hydrocarbon group having 1 to 40 carbon atoms or an m-valent heterocyclic group having 2 to 40 carbon atoms, and when m is 2, R 11 may be an ether bond, a carbonyl group, an azo group, a thioether bond, a carbonate bond, a carbamate bond, a sulfinyl group, or a sulfonyl group. In addition, some or all of the hydrogen atoms of the m-valent hydrocarbon group or m-valent heterocyclic group may be substituted with a group containing a heteroatom, and some of the -CH2- of the m-valent hydrocarbon group may be substituted with a group containing a heteroatom. R 12 is a single bond or a hydrocarbylene group having 1 to 10 carbon atoms, and some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a hetero atom, or some of the -CH2- of the hydrocarbylene group may be substituted with a group containing a hetero atom. 12 may be the same as or different from each other.

[0031] R 11 The m-valent hydrocarbon group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. The m-valent hydrocarbon group is a group obtained by eliminating m hydrogen atoms from a hydrocarbon. Specific examples of the hydrocarbon include alkanes having 1 to 40 carbon atoms, alkenes having 2 to 40 carbon atoms, alkynes having 2 to 40 carbon atoms, saturated cyclic hydrocarbons having 3 to 40 carbon atoms, unsaturated cyclic hydrocarbons having 3 to 40 carbon atoms, and aromatic hydrocarbons having 6 to 40 carbon atoms.

[0032] Specific examples of the alkanes having 1 to 40 carbon atoms include methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, and structural isomers thereof.

[0033] Specific examples of the alkenes having 1 to 40 carbon atoms include ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, and structural isomers thereof.

[0034] Specific examples of the alkyne having 1 to 40 carbon atoms include acetylene, propyne, butyne, pentyne, hexyne, heptyne, octyne, nonyne, decyne, and structural isomers thereof.

[0035] Specific examples of the cyclic saturated hydrocarbon having 3 to 40 carbon atoms include cyclopropane, cyclobutane, cyclohexane, cycloheptane, cyclooctane, adamantane, and norbornane.

[0036] Specific examples of the cyclic unsaturated hydrocarbon having 3 to 40 carbon atoms include cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, and norbornene.

[0037] Specific examples of the aromatic hydrocarbon having 6 to 40 carbon atoms include benzene, naphthalene, and biphenyl.

[0038] R 11 The m-valent heterocyclic group represented by the following formula is a group obtained by eliminating m hydrogen atoms from a heterocyclic compound. Specific examples of the heterocyclic compound include furan, pyridine, pyrazole, and thiazolidine.

[0039] The m-valent hydrocarbon group or m-valent heterocyclic group may have some or all of its hydrogen atoms substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, and as a result, may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. Furthermore, the m-valent hydrocarbon group may have some of its -CH- groups substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, and as a result, may contain a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), etc.

[0040] R 12The hydrocarbylene group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,1 alkanediyl groups having 1 to 20 carbon atoms, such as a 2-diyl group; cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms, such as a cyclopentanediyl group, a cyclohexanediyl group, a norbornanediyl group, and an adamantanediyl group; unsaturated aliphatic hydrocarbylene groups having 2 to 20 carbon atoms, such as a vinylene group and a propene-1,3-diyl group; arylene groups having 6 to 20 carbon atoms, such as a phenylene group and a naphthylene group; and groups obtained by combining these. In addition, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, or some of the -CH- constituting the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbylene group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride or the like.

[0041] Of the carboxylic acid compounds represented by formula (2), those in which m is an integer of 2 to 4 are preferred. In this case, when mixed with a hypervalent iodine compound, a strong resist film with a high molecular weight is easily formed, which is preferred from the viewpoints of etching resistance and developer resistance.

[0042] Specific examples of the carboxylic acid compound include, but are not limited to, the following: [ka]

[0043] [ka]

[0044] [ka]

[0045] In the resist composition, the molar ratio of the hypervalent iodine compound to the carboxylic acid compound is preferably hypervalent iodine compound:carboxylic acid compound=10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. The hypervalent iodine compound may be used alone, or two or more types may be used in combination. The carboxylic acid compound may be used alone, or two or more types may be used in combination.

[0046] [solvent] The resist composition contains a solvent. The solvent is not particularly limited as long as it can dissolve the hypervalent iodine compound, the carboxylic acid compound, and other components described below 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, ethylene glycol monoethyl ether; Examples of suitable solvents include ethers such as propylene glycol dimethyl ether and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono tert-butyl ether acetate; carboxylic acids such as formic acid, acetic acid, and propionic acid; lactones such as γ-butyrolactone; and mixed solvents thereof.

[0047] The content of the solvent in the resist composition is preferably an amount such that the solids concentration in the resist composition is 0.1 to 20 mass%, more preferably 0.1 to 15 mass%, and even more preferably 0.1 to 10 mass%. In the present invention, the solids refer collectively to all components of the resist composition other than the solvent. The solvents may be used alone or in combination of two or more.

[0048] [Other ingredients] The resist composition may further contain a surfactant. The surfactant is preferably a fluorine-based and / or silicone-based surfactant. Specific examples of such surfactants include those described in paragraph

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

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

[0049] When the resist composition contains the surfactant, the content thereof is preferably 0.0001 to 2 mass % of the total solid content. The surfactant may be used alone or in combination of two or more.

[0050] The resist composition may further contain a radical scavenger, which can control photoreactions during photolithography and adjust sensitivity.

[0051] Specific examples of the radical scavenger include hindered phenols, quinones, hindered amines, and thiol compounds. Specific examples of hindered phenols include dibutylhydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Specific examples of quinones include 4-methoxyphenol (methoquinone) and hydroquinone. Specific examples of hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidine-N-oxy radical. Specific examples of thiols include dodecanethiol and hexadecanethiol.

[0052] When the resist composition contains the radical scavenger, the content thereof is preferably 0.01 to 10 mass % of the total solid content. The radical scavenger may be used alone or in combination of two or more.

[0053] The resist composition may further contain a crosslinking agent, which can accelerate the photoreaction during photolithography and increase the sensitivity of the resist.

[0054] Specific examples of the crosslinking agent include compounds having a carbon-carbon unsaturated bond as a functional group, such as a vinyl group, a (meth)acrylate group, an allyl group, an alkynyl group, or an aromatic ring. Specific examples of compounds having a vinyl group include linear alkenes, branched alkenes, and cyclic alkenes, which may have a substituent. Specific examples of compounds having a (meth)acrylate group include acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, which may have a substituent. Specific examples of compounds having an allyl group include allyl alcohol, allyl ether, allyl ester, allyl amide, allyl amine, and allyl group-containing isocyanurates, which may have a substituent. Specific examples of compounds having an alkynyl group include linear alkynes, branched alkynes, cyclic alkynes, alkynyl alcohols, alkynyl ethers, alkynyl esters, alkynyl amides, alkynyl amines, and alkynyl group-containing isocyanurates, which may have a substituent. Specific examples of compounds having an aromatic ring include arenes, heteroarenes, styrene, stilbene, phenylacetylene, acenaphthylene, chalcone, and the like, which may have a substituent. The crosslinking agent may have only one or more of the functional groups. The number of functional groups contained in the crosslinking agent is preferably 1 to 10, and more preferably 2 to 8.

[0055] When the resist composition contains the crosslinking agent, the content thereof is preferably 0.01 to 50 mass % of the total solid content. The crosslinking agents may be used alone or in combination of two or more.

[0056] The resist composition contains a hypervalent iodine compound and a carboxylic acid compound as its main components, but does not contain an acid-labile group-containing base polymer or a photoacid generator, which are contained in conventional chemically amplified resist compositions. However, the resist composition can form a negative pattern by rendering the exposed area insoluble in a developer, particularly upon exposure to EB or EUV. The mechanism behind this is not completely clear, but is presumed to be as follows.

[0057] The hypervalent iodine compound is a compound having at least two acyloxy groups. It is believed that when such a hypervalent iodine compound is mixed with a carboxylic acid compound, an exchange of carboxylate ligands occurs through an equilibrium reaction. If the original carboxylate ligand can be removed in some way, a hypervalent iodine compound having a new ligand is generated. For example, by mixing iodobenzene diacetate, a relatively readily available hypervalent iodine compound, with a carboxylic acid compound having a high molecular weight and removing the resulting low-boiling acetic acid, the ligand exchange is completed. If the ligand has a sufficiently high molecular weight, a strong resist film can be formed. In particular, if a carboxylic acid compound having multiple carboxy groups (e.g., a dicarboxylic acid compound) is used, it is believed that a high-molecular-weight polyester structure having the hypervalent iodine compound can be formed, ensuring film formability.

[0058] Such a bond between a hypervalent iodine compound and a carboxylic acid compound is generated during film formation. That is, by removing the low-molecular-weight carboxylic acid component generated during film formation and the subsequent baking step, the ligand exchange reaction is completed and a resist film is formed.

[0059] The resist film obtained from the resist composition is highly soluble in specific solvents such as alkaline aqueous solutions due to the ligand exchange reaction of hypervalent iodine. However, when decomposed by light, this is converted into chemical species with low solubility in those solvents. As a result, the exposed area becomes insoluble in the developer, and it is presumed that the resist film functions as a negative resist composition.

[0060] Based on the above speculation, it can be said that the resist composition is a non-chemically amplified resist composition. Therefore, the resist composition does not cause image blurring due to acid diffusion, which is seen in conventional chemically amplified resist compositions (compositions containing a base polymer and a photoacid generator), and makes it possible to resolve fine patterns.

[0061] The resist composition is particularly effective in EUV lithography because it contains iodine atoms with high absorption capacity for EUV light, which reduces shot noise and enables higher resolution and lower LWR.

[0062] As an EUV resist composition capable of forming fine patterns, a metal resist containing, as its main component, a metal tin compound that has a high absorption capacity for EUV light, similar to iodine atoms, has been reported (e.g., Patent Document 2). However, as mentioned above, such metal resists have many problems, such as insufficient solubility in solvents, poor storage stability, and defects due to post-etching residues caused by the inclusion of metal elements. On the other hand, since the resist composition does not use metal elements, it is more advantageous than metal resists in terms of defects and does not have any problems with solubility in solvents.

[0063] Patent Documents 4 and 5 describe resist compositions containing a hypervalent iodine compound as an additive, and resist compositions incorporating a hypervalent iodine compound into the polymer backbone of a base polymer. However, these patent documents only describe the ability of the resist composition to improve line edge roughness, and make no mention of the possibility of the hypervalent iodine compound undergoing photodecomposition or functioning as a material for a non-chemically amplified resist composition. Furthermore, according to the descriptions of the blending amounts and specific examples, the hypervalent iodine compound is not the main component. Patent Document 3 also proposes a positive resist composition using a hypervalent iodine compound, but does not mention the possibility that the resist composition could function as a negative resist by combining it with an appropriate developer. Therefore, these patent documents do not suggest a method for forming a negative resist pattern, as in the present invention, that can reduce shot noise in EUV lithography and form fine patterns as a non-chemically amplified resist. In other words, it can be said that the present invention provides a clearly novel method for forming a negative resist pattern.

[0064] [Method for forming negative resist pattern] The method for forming a negative resist pattern of the present invention includes the steps of: (i) forming a resist film on a substrate using the resist composition described above; (ii) exposing the resist film to high-energy rays; and (iii) developing the exposed resist film using a developer that dissolves unexposed areas but does not dissolve exposed areas.

[0065] [Step (i)] Step (i) is a step of forming a resist film on a substrate using the resist composition described above. Specifically, the resist composition is applied to a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.) by an appropriate coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, or doctor coating to a coating thickness of 0.01 to 2 μm. This is then prebaked on a hot plate, preferably at 60 to 200°C for 10 seconds to 30 minutes, more preferably at 80 to 180°C for 30 seconds to 20 minutes, to form a resist film.

[0066] [Step (ii)] 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 laser light, γ-rays, and synchrotron radiation. When ultraviolet radiation, far-ultraviolet radiation, EUV, X-rays, soft X-rays, excimer laser light, γ-rays, and synchrotron radiation are used as the high-energy radiation, the exposure dose is preferably 1 to 300 mJ / cm, either directly or using a mask for forming a desired pattern. 2 approximately, more preferably 10 to 200 mJ / cm 2 When EB is used as the high energy beam, the exposure dose is preferably 0.1 to 2000 μC / cm 2 directly or using a mask for forming a desired pattern. 2 approximately, more preferably 0.5 to 1500 μC / cm 2 The resist composition is particularly suitable for fine patterning using high-energy rays such as EB or EUV.

[0067] After exposure, PEB is performed as needed, preferably on a hot plate or in an oven at 30 to 120°C for 10 seconds to 30 minutes, more preferably at 60 to 100°C for 30 seconds to 20 minutes.

[0068] [Step (iii)] Step (iii) is a step of developing the exposed resist film after exposure or PEB using a developer that dissolves unexposed areas but not exposed areas. In the present invention, a negative resist pattern can be obtained by development. The developer used here is not particularly limited as long as it dissolves unexposed areas but not exposed areas. Such a solvent is preferably an alkaline developer, and specific examples thereof include aqueous solutions of quaternary ammonium salts, ammonia, primary amines, secondary amines, tertiary amines, inorganic alkalis, etc. The alkaline developer is preferably an aqueous solution of a quaternary ammonium salt, such as tetramethylammonium hydroxide, and particularly preferably has an alkali concentration of 0.1 to 20% by mass. A surfactant or alcohol may be added to the developer in an appropriate amount. These developers may be used alone or in combination.

[0069] After development, rinsing is performed as necessary. A preferred rinsing solution is a solvent that is miscible with the developer but does not dissolve the resist film. Preferred examples of such solvents include alcohols having 3 to 10 carbon atoms, ether compounds having 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents having 6 to 12 carbon atoms.

[0070] Rinsing can reduce the occurrence of resist pattern collapse and defects. Rinsing is not always necessary, and not performing rinsing can reduce the amount of solvent used. [Example]

[0071] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0072] [1] Preparation of resist composition [Examples 1-1 to 1-19, Comparative Examples 1-1 to 1-3] Resist compositions (R-01 to R-19) were prepared by dissolving a hypervalent iodine compound, a carboxylic acid compound, a radical scavenger, and a crosslinker in a solvent according to the compositions shown in Table 1 below, and filtering the resulting solutions through a 0.2 μm Teflon (registered trademark) filter. Comparative resist compositions (CR-01 to CR-03) were prepared by mixing a base polymer, a photoacid generator, a sensitivity adjuster, a solvent, and 0.01 mass% of a surfactant (PF-636, Omnova) according to the compositions shown in Table 2 below, and filtering the resulting solutions through a 0.2 μm Teflon (registered trademark) filter.

[0073] [Table 1]

[0074] [Table 2]

[0075] In Table 1, the hypervalent iodine compounds (I-1 to I-3), carboxylic acid compounds (CA-1 to CA-10), radical scavenger T-1, crosslinking agent L-1 and solvents are as follows. [ka]

[0076] [ka]

[0077] [ka]

[0078] [ka]

[0079] Solvent: PGMEA (propylene glycol monomethyl ether acetate) AcOH (acetic acid) HBM (2-hydroxyisobutyric acid methyl ester) PA (propionic acid) GBL (γ-butyrolactone)

[0080] In Table 2, the base polymer (P-1), photoacid generators (PAG-1, PAG-2) and sensitivity adjusters (Q-1, Q-2) are as follows. [ka] Mw=8755 (polystyrene equivalent), Mw / Mn=1.94

[0081] [ka]

[0082] [ka]

[0083] [2] EUV lithography evaluation (line and space patterns) [Examples 2-1 to 2-19, Comparative Examples 2-1 to 2-3] Each resist composition (R-01 to R-19, CR-01 to CR-03) was spin-coated onto a Si substrate coated with a 20 nm thick silicon-containing spin-on hard mask (SHB-A940, manufactured by Shin-Etsu Chemical Co., Ltd.) (43% silicon by mass), and then prebaked (PAB) for 60 seconds using a hotplate at the temperature listed in Table 3 to produce a 40 nm thick resist film. The resist film was exposed to a 36 nm line-and-space (LS) 1:1 pattern using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination), and then subjected to PEB for 60 seconds on a hotplate at the temperature listed in Table 3. Development was then performed for 30 seconds using the developer listed in Table 3 to form a negative LS pattern with a space width of 18 nm and a pitch of 36 nm. The resulting resist patterns were evaluated as follows, and the results are shown in Table 3.

[0084] [Sensitivity evaluation] The LS pattern was observed using a length measurement SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the optimum exposure dose Eop (mJ / cm) for obtaining an LS pattern with a space width of 18 nm and a pitch of 36 nm was determined. 2 ) was calculated and used as the sensitivity.

[0085] [LWR rating] The LS pattern obtained by irradiation with the optimum exposure dose was measured at 10 points in the longitudinal direction of the space width using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the LWR (nm) was calculated as three times the standard deviation (σ). The smaller this value, the less roughness and the more uniform the space width pattern obtained.

[0086] [Limiting resolution evaluation] The limiting line width (nm) that can be resolved when forming a pattern by gradually increasing the exposure dose from the optimum exposure dose at which the LS pattern is formed was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a finer pattern can be formed.

[0087] [Table 3]

[0088] Developer: nBA (butyl acetate) TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0089] The results shown in Table 3 demonstrate that the method for forming a negative resist pattern of the present invention makes it possible to form a negative resist pattern that is excellent in sensitivity, LWR, and resolution in LS pattern formation by EUV exposure.

[0090] [3] EUV lithography evaluation (pillar pattern) [Examples 3-1 to 3-19, Comparative Examples 3-1 to 3-3] Each resist composition (R-01 to R-19, CR-01 to CR-03) was spin-coated onto a Si substrate with a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd., and then subjected to PAB for 60 seconds at the temperature listed in Table 4 using a hot plate to produce a 50 nm thick resist film. The resist film was then exposed to light using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadruple pole illumination, on-wafer dimensions 64 nm pitch, +20% bias pillar pattern mask), subjected to PEB for 60 seconds on a hot plate at the temperature listed in Table 4, and developed for 30 seconds using the developer listed in Table 4 to obtain a 32 nm pillar pattern. The resulting resist patterns were evaluated as follows, and the results are shown in Table 4.

[0091] [Sensitivity evaluation] The pillar pattern was observed using a length measuring SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the optimum exposure dose Eop (mJ / cm) for obtaining a pillar pattern with a dimension of 22 nm was determined. 2 ) was calculated and used as the sensitivity.

[0092] [CDU Rating] The dimensions of 50 pillar patterns obtained by irradiation with the optimal exposure dose were measured, and the standard deviation (σ) calculated from the results was tripled (3σ) to obtain the CDU (nm). The smaller this value, the more uniform the pillar diameter pattern obtained.

[0093] [Limiting resolution evaluation] The limiting pillar diameter (nm) that can be resolved when forming a pillar pattern by gradually decreasing the exposure dose from the optimum exposure dose for forming the pillar pattern was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a pattern with a finer pillar diameter can be formed.

[0094] [Table 4]

[0095] The results shown in Table 4 demonstrate that the method for forming a negative resist pattern of the present invention makes it possible to form a negative resist pattern that is excellent in sensitivity, CDU, and resolution when forming a pillar pattern by EUV exposure.

Claims

1. (i) forming a resist film on a substrate using a resist composition containing a hypervalent iodine compound, a carboxylic acid compound, and a solvent; (ii) exposing the resist film to high-energy radiation; (iii) developing the exposed resist film using a developer that dissolves the unexposed areas but not the exposed areas; A method for forming a negative resist pattern comprising:

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

3. 2. The method for forming a negative resist pattern according to claim 1, wherein the high-energy beam is an electron beam or extreme ultraviolet light.

4. 4. The method for forming a negative resist pattern according to claim 1, wherein the hypervalent iodine compound is represented by the following formula (1): 【Chemical 1】 (wherein n is an integer from 0 to 5. R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms. R 3 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 to 5, each R 3 may be the same as or different from each other.)

5. 4. The method for forming a negative resist pattern according to claim 1, wherein the carboxylic acid compound is represented by the following formula (2): 【Chemistry 2】 (In the formula, m is an integer of 1 to 4. R 11 is an m-valent hydrocarbon group having 1 to 40 carbon atoms or an m-valent heterocyclic group having 2 to 40 carbon atoms, and when m is 2, R 11 may be an ether bond, a carbonyl group, an azo group, a thioether bond, a carbonate bond, a carbamate bond, a sulfinyl group, or a sulfonyl group. In addition, some or all of the hydrogen atoms of the m-valent hydrocarbon group or the m-valent heterocyclic group may be substituted with a group containing a hetero atom, and the —CH 2 A portion of - may be substituted with a group containing a hetero atom. R 12 represents a single bond or a hydrocarbylene group having 1 to 10 carbon atoms, and some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a hetero atom, and the —CH 2 When m is 2 to 4, each R 12 may be the same as or different from each other.)

6. 6. The method for forming a negative resist pattern according to claim 5, wherein m is an integer of 2 to 4.

7. 4. The method for forming a negative resist pattern according to claim 1, wherein the resist composition further contains a crosslinking agent.

8. 4. The method for forming a negative resist pattern according to claim 1, wherein the resist composition further contains a radical scavenger.

Images