Resist composition and pattern forming method

Abstract

To provide a non-chemically amplified resist composition excellent in sensitivity and resolution in photolithography using high-energy radiation, and a pattern forming method using the resist composition.SOLUTION: A resist composition comprises a hypervalent bismuth compound, a carboxylic acid compound, and a solvent.SELECTED DRAWING: None

Description

[Technical Field]

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

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

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

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

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

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

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

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

[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, poor storage stability due to excessive reactivity, and defects due to post-etching residues. [Prior art documents] [Patent documents]

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

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

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

[0013] As a result of extensive research into achieving the above-mentioned object, the inventors of the present invention discovered that a resist composition containing a specific bismuth compound and a carboxylic acid compound as its main components provides a resist film that exhibits extremely high sensitivity and excellent resolution, and is therefore extremely effective for precise microfabrication, which led to the completion of the present invention.

[0014] That is, the present invention provides the following resist composition and pattern forming method. 1. A resist composition comprising a hypervalent bismuth compound, a carboxylic acid compound, and a solvent. 2. The resist composition of 1, wherein the hypervalent bismuth compound is represented by the following formula (1): [ka] (In the formula, p, q, and r each independently represent 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 , R 4 and R 5 are each independently a halogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. 3. The resist composition of 1 or 2, 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 11 may be an ether bond, a carbonyl group, an azo group, a thioether bond, a carbonate bond, a carbamate bond, a sulfinyl group, or a sulfonyl group. Some or all of the hydrogen atoms in the 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.) 4. A pattern forming method comprising the steps of forming a resist film on a substrate using the resist composition of any one of 1 to 3, exposing the resist film to high-energy rays, and developing the exposed resist film using a developer. 5. The pattern formation method according to 4, wherein the high-energy radiation is EB or EUV. 6. The pattern forming method of 4 or 5, wherein the developer dissolves exposed areas but does not dissolve unexposed areas. 7. The pattern forming method of 4 or 5, wherein the developer dissolves the unexposed areas but does not dissolve the exposed areas. [Effects of the Invention]

[0015] The resist composition of the present invention achieves both high sensitivity and high resolution, and is extremely useful for forming fine patterns, particularly in EB lithography and EUV lithography. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Resist composition] The resist composition of the present invention contains a hypervalent bismuth compound and a carboxylic acid compound as main components.

[0017] [Hypervalent bismuth compounds] A hypervalent bismuth compound is a general term for bismuth compounds that have valence electrons that formally exceed the octet rule. Examples of hypervalent bismuth compounds include pentacoordinate bismuth compounds with an oxidation number of +5.

[0018] As the hypervalent bismuth compound, a pentacoordinate hypervalent bismuth compound represented by the following formula (1) is particularly preferred. [ka]

[0019] In formula (1), p, q and r each independently represent an integer of 0 to 5.

[0020] In formula (1), R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2may 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.

[0021] In formula (1), R 3 , R 4 and R 5are each independently a halogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. 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 methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0]. 2,6 ] cyclic saturated hydrocarbyl groups having 3 to 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. Furthermore, some or all of the hydrogen atoms in the hydrocarbyl 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, and some of the -CH2- groups in the hydrocarbyl group may be substituted with a group containing a heteroatom, such as an oxygen atom, a sulfur atom, or a nitrogen atom, resulting in the hydrocarbyl group containing a hydroxy group, a cyano group, a halogen atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, or a carboxylic anhydride (-C(=O)-OC(=O)-). When p is 2 to 5, each R 3 may be the same or different from each other, and when q is 2 to 5, each R 4 may be the same or different from each other, and when r is 2 to 5, each R 5 may be the same as or different from each other.

[0022] Specific examples of the hypervalent bismuth compound represented by formula (1) include, but are not limited to, the following: [ka]

[0023] [ka]

[0024] [ka]

[0025] [ka]

[0026] [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]

[0027] 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 12is 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Specific examples of the cyclic saturated hydrocarbon having 3 to 40 carbon atoms include cyclopropane, cyclobutane, cyclohexane, cycloheptane, cyclooctane, adamantane, and norbornane.

[0033] Specific examples of the cyclic unsaturated hydrocarbon having 3 to 40 carbon atoms include cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, and norbornene.

[0034] Specific examples of the aromatic hydrocarbon having 6 to 40 carbon atoms include benzene, naphthalene, and biphenyl.

[0035] 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.

[0036] 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.

[0037] 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 (-C(=O)-OC(=O)-), etc.

[0038] Specific examples of the carboxylic acid compound include, but are not limited to, the following: [ka]

[0039] [ka]

[0040] [ka]

[0041] In the resist composition of the present invention, the content ratio of the hypervalent bismuth compound to the carboxylic acid compound is preferably hypervalent bismuth 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 by molar ratio.

[0042] [solvent] The resist composition of the present invention contains a solvent. The solvent is not particularly limited as long as it can dissolve the hypervalent bismuth 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.

[0043] The content of the solvent in the resist composition of the present invention is preferably an amount such that the solids concentration in the resist composition is 0.1 to 20 mass%, more preferably 0.1 to 15 mass%, and even more preferably 0.1 to 10 mass%. In the present invention, the term "solids" refers collectively to all components of the resist composition other than the solvent. The solvents may be used alone or in combination of two or more.

[0044] [Other ingredients] The resist composition of the present invention may further contain a surfactant. The surfactant is preferably a fluorine-based and / or silicone-based surfactant. Specific examples of such surfactants include 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.

[0045] When the resist composition of the present invention contains the surfactant, the content thereof is preferably 0.0001 to 2 mass % of the total solid content. The surfactant may be used alone or in combination of two or more.

[0046] The resist composition of the present invention may further contain a radical scavenger. By adding a radical scavenger, it is possible to control the photoreaction during photolithography and adjust the sensitivity.

[0047] Specific examples of the radical scavengers include hindered phenols, quinones, hindered amines, and thiol compounds. Specific examples of the hindered phenols include dibutylhydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Specific examples of the quinones include 4-methoxyphenol (methoquinone) and hydroquinone. Specific examples of the hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidine-N-oxy radical. Specific examples of the thiols include dodecanethiol and hexadecanethiol.

[0048] When the resist composition of the present invention contains the radical scavenger, the content thereof is preferably 0.01 to 10 mass % of the total solid content. The radical scavenger may be used alone or in combination of two or more.

[0049] The resist composition of the present invention contains a hypervalent bismuth compound and a carboxylic acid compound as main components, but does not contain an acid-labile group-containing base polymer or a photoacid generator, as are contained in conventional chemically amplified resist compositions. However, the resist composition of the present invention undergoes a change in developer solubility in unexposed and exposed areas, particularly upon exposure to EB or EUV, enabling pattern formation. The mechanism behind this change is not completely clear, but is presumed to be as follows.

[0050] The hypervalent bismuth compound is a pentacoordinate compound, as represented by formula (1), in which an aryl group and two carboxylate ligands are bonded. When such a pentacoordinate bismuth compound is mixed with a carboxylic acid compound, an exchange of the carboxylate ligands is thought to occur through an equilibrium reaction. If the original carboxylate ligand can be removed in some way, a hypervalent bismuth compound with a new ligand is generated. For example, triphenylbismuth diacetate, a relatively readily available hypervalent bismuth compound, is mixed with a high-molecular-weight carboxylic acid compound, and the resulting low-boiling acetic acid is removed to complete the ligand exchange. A sufficiently large molecular weight ligand can form a robust resist film. In particular, using a carboxylic acid compound with multiple carboxyl groups (e.g., a dicarboxylic acid compound) is thought to be able to form a high-molecular-weight polyester structure containing the hypervalent bismuth compound, ensuring film formability.

[0051] Such a bond between the hypervalent bismuth compound and the carboxylic acid compound is generated during film formation. That is, by removing the original low-molecular-weight carboxylic acid component during film formation and in the subsequent baking step, the ligand exchange reaction is completed and a resist film is formed.

[0052] The formed film of hypervalent bismuth compound is decomposed by light, which changes its polarity, and a pattern is formed by the development process. By selecting an appropriate developer, either a positive or negative pattern can be formed.

[0053] Based on the above speculation, it can be said that the resist composition of the present invention is a non-chemically amplified resist composition. Therefore, the resist composition of the present invention does not suffer from the image blurring caused by acid diffusion that occurs in conventional chemically amplified resist compositions (compositions containing a base polymer and a photoacid generator), and makes it possible to resolve fine patterns.

[0054] The resist composition of the present invention is particularly effective in EUV lithography because it contains bismuth atoms with high absorption capacity for EUV light, which reduces shot noise and enables the achievement of higher resolution and lower LWR.

[0055] As an EUV resist composition capable of forming fine patterns, a metal resist containing, as its main component, a metal tin compound, which has a high absorption capacity for EUV light similar to that of bismuth atoms, has been reported (e.g., Patent Document 2). However, as mentioned above, such metal resists have problems such as insufficient solubility in solvents and storage stability. In contrast, the resist composition of the present invention has excellent solvent solubility. Furthermore, the resist composition of the present invention can be applied to both positive-tone and negative-tone resists, and therefore has a wide range of uses. For example, in the contact hole formation process, metal resists that are developed using negative-tone development require a reversal process step after pillar pattern formation, whereas positive-tone resists do not require such a step. Therefore, from the perspective of process simplicity, the resist composition of the present invention can be said to be more useful than metal resists.

[0056] [Pattern formation method] When the resist composition of the present invention is used in the manufacture of various integrated circuits, known lithography techniques can be applied. For example, a specific example of a pattern formation method includes a step of forming a resist film on a substrate using the resist composition, a step of exposing the resist film to high-energy rays, and a step of developing the exposed resist film using a developer.

[0057] First, the resist composition of the present invention is applied to a substrate for integrated circuit production (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating, etc.) or a substrate for mask circuit production (Cr, CrO, CrON, MoSi2, SiO2, etc.) by an appropriate coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, doctor coating, etc., to a coating thickness of 0.01 to 2 μm. This 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.

[0058] Next, the resist film is exposed 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 5000 μC / cm 2 either directly or using a mask for forming a desired pattern. 2 approximately, more preferably 0.5 to 4000 μC / cm 2 The resist composition of the present invention is particularly suitable for fine patterning using high-energy rays such as EB or EUV.

[0059] 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.

[0060] After exposure or PEB, patterning is performed using a developer. Specific examples of the developer used here include an alkaline aqueous solution such as a tetramethylammonium hydroxide aqueous solution, 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, isopropyl alcohol, n-butanol, n-pentanol, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, and ethyl propionate. Examples of organic solvents that can be used include ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, ethyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, 2-phenylethyl acetate, 2-propanol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, and 4-methyl-2-pentanol. In the present invention, organic solvent development dissolves exposed areas and leaves unexposed areas undissolved, forming a positive pattern, and aqueous alkaline development dissolves unexposed areas and leaves unexposed areas undissolved, forming a negative pattern. These developers may be used alone or in combination of two or more.

[0061] 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. Examples of such solvents that are preferably used 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. Alternatively, water may be used as a rinsing solution instead of an organic solvent.

[0062] 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]

[0063] 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.

[0064] [1] Preparation of resist composition [Examples 1-1 to 1-16, Comparative Examples 1-1 to 1-3] Resist compositions (R-01 to R-16) were prepared by dissolving a hypervalent bismuth compound and a carboxylic acid compound in a solvent according to the compositions shown in Table 1 below, and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter. Comparative resist compositions (CR-01 to CR-03) were also prepared by mixing a 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 mixture through a 0.2 μm Teflon (registered trademark) filter.

[0065] [Table 1]

[0066] [Table 2]

[0067] In Table 1, the hypervalent bismuth compounds (B-1 to B-3), carboxylic acid compounds (CA-1 to CA-11) and solvents are as follows. [ka]

[0068] [ka]

[0069] Solvent: PGMEA (propylene glycol monomethyl ether acetate) HBM (2-hydroxyisobutyric acid methyl ester) GBL (γ-butyrolactone)

[0070] 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]

[0071] [ka]

[0072] [ka]

[0073] [2] EUV lithography evaluation (line and space pattern, positive tone development) [Examples 2-1 to 2-16, Comparative Examples 2-1 to 2-3] Each resist composition (R-01 to R-16, 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 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd., and prebaked (PAB) for 60 seconds using a hot plate at the temperature listed in Table 3 to produce a 40 nm thick resist film. The resist film was exposed to a 48 nm line-and-space (LS) 1:1 pattern using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination), subjected to PEB on a hot plate at the temperature listed in Table 3 for 60 seconds, and developed for 30 seconds using the developer listed in Table 3 to form a 24 nm space width, 48 nm pitch LS pattern. The resulting resist patterns were evaluated as follows, and the results are shown in Table 3.

[0074] [Sensitivity evaluation] The LS 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 an LS pattern with a space width of 24 nm and a pitch of 48 nm was determined. 2 ) was calculated and used as the sensitivity.

[0075] [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.

[0076] [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.

[0077] [Table 3]

[0078] Developer: nBA (butyl acetate) TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0079] [3] EUV lithography evaluation (line and space pattern, negative tone development) [Examples 3-1 to 3-16, Comparative Examples 3-1 to 3-3] Each resist composition (R-01 to R-16, 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 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd., and prebaked (PAB) for 60 seconds using a hot plate at the temperature listed in Table 3 to produce a 40 nm thick resist film. The resist film was exposed to a 48 nm line-and-space (LS) 1:1 pattern using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination), subjected to PEB on a hot plate at the temperature listed in Table 3 for 60 seconds, and developed for 30 seconds using the developer listed in Table 3 to form a 24 nm space width, 48 nm pitch LS pattern. The resulting resist patterns were evaluated as follows, and the results are shown in Table 4.

[0080] [Sensitivity evaluation] The 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 an LS pattern with a space width of 24 nm and a pitch of 48 nm was determined. 2 ) was calculated and used as the sensitivity.

[0081] [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.

[0082] [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.

[0083] [Table 4]

[0084] The results shown in Tables 3 and 4 demonstrate that the resist composition of the present invention exhibits excellent sensitivity, LWR, and resolution in both positive tone and negative tone development when forming an LS pattern by EUV exposure.

[0085] [4] EUV lithography evaluation (contact hole pattern) [Examples 4-1 to 4-16, Comparative Examples 4-1 to 4-3] Each resist composition (R-01 to R-15, 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 pre-baked (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, wafer dimensions 64 nm pitch, +20% bias hole pattern mask), and PEB was performed on a hot plate at the temperature listed in Table 4 for 60 seconds. Development was then performed for 30 seconds using the developer listed in Table 4 to obtain a 32 nm hole pattern. The resulting resist patterns were evaluated as follows, and the results are shown in Table 5.

[0086] [Sensitivity evaluation] The contact hole pattern was observed using a length measuring SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the optimum exposure dose Eop (mJ / cm) for obtaining a hole pattern with a dimension of 32 nm was determined. 2 ) was calculated and used as the sensitivity.

[0087] [CD Uniformity (CDU) Evaluation] The dimensions of 50 hole 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 CDU (nm). The smaller this value, the more uniform the hole diameter pattern obtained.

[0088] [Limiting resolution evaluation] The limiting hole diameter (nm) that can be resolved when forming a hole pattern by gradually decreasing the exposure dose from the optimum exposure dose required to form the hole pattern was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a pattern with a finer hole diameter can be formed.

[0089] [Table 5]

[0090] The results shown in Table 5 demonstrate that the resist composition of the present invention is excellent in sensitivity, CDU, and resolution when forming a contact hole pattern by EUV exposure.

Claims

1. A resist composition comprising a hypervalent bismuth compound, a carboxylic acid compound, and a solvent.

2. 2. The resist composition according to claim 1, wherein the hypervalent bismuth compound is represented by the following formula (1): 【Chemical 1】 (In the formula, p, q, and r each independently represent 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 , R 4 and R 5 are each independently a halogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom.

3. 2. The resist composition 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.)

4. 4. A pattern forming method comprising the steps of: forming a resist film on a substrate using the resist composition according to claim 1; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer.

5. 5. The pattern forming method according to claim 4, wherein the high-energy beam is an electron beam or extreme ultraviolet light.

6. 5. The pattern forming method according to claim 4, wherein the developer dissolves the exposed area but does not dissolve the unexposed area.

7. 5. The pattern forming method according to claim 4, wherein the developer dissolves the unexposed areas but does not dissolve the exposed areas.

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