Resist composition, laminate, and pattern forming method

Abstract

To provide a non-chemically amplified resist composition excellent in sensitivity and resolution in photolithography using high-energy radiation, a laminated film including a resist film obtained from the resist composition, and a pattern forming method using the resist composition.SOLUTION: A resist composition comprises a hypervalent bismuth compound, a carboxy group-containing polymer, and a solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resist composition, a laminate, 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 aims 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, a laminate film comprising a resist film obtained from the resist composition, 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 carboxy group-containing polymer 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 carboxy group-containing polymer, 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 carboxyl group-containing polymer contains a repeating unit represented by the following formula (2): [ka] (In the formula, R A each independently represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. X A is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX A1 -X A1 represents a linear, branched, or cyclic alkylene saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain. 4. A laminate comprising a substrate and a resist film formed on the substrate from a resist composition according to any one of 1 to 3. 5. The laminate of 4, further comprising a resist underlayer film between the substrate and the resist film. 6. A pattern forming method comprising the steps of: forming a resist film on a substrate, or on an underlayer film of a substrate laminated with an underlayer film, using the resist composition according to any one of 1 to 3; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer. 7. The pattern formation method according to claim 6, wherein the high-energy radiation is EB or EUV. 8. The pattern forming method according to 6 or 7, wherein the developer dissolves exposed areas but does not dissolve unexposed areas. 9. The pattern forming method according to 6 or 7, 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 carboxy group-containing polymer 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] [Carboxy group-containing polymer] The carboxyl group-containing polymer preferably contains a carboxyl group-containing repeating unit, which is preferably represented by the following formula (2): [ka]

[0027] In formula (2), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. A is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX A1 -X A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain.

[0028] Specific examples of the carboxy group-containing repeating unit include, but are not limited to, the following: A is the same as above. [ka]

[0029] [ka]

[0030] The carboxy group-containing polymer may further contain a repeating unit other than the carboxy group-containing repeating unit (hereinafter also referred to as "other repeating unit"). The other repeating unit is not particularly limited, but is preferably one that can improve the solubility in a solvent of a polymer that is poorly soluble in a solvent when it is a repeating unit having only a carboxy group. Preferred examples of such repeating units include repeating units having a hydrocarbyl group having 1 to 20 carbon atoms and optionally containing at least one selected from the group consisting of a fluorine atom, a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, an ester bond, an ether bond, a sulfide bond, a carbonate bond, a lactone ring, and a sultone ring.

[0031] Specific examples of the other repeating units include, but are not limited to, those shown below. A is the same as above. [ka]

[0032] [ka]

[0033] [ka]

[0034]

change

[0035]

change

[0036]

change

[0037]

change

[0038]

change

[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045] [ka]

[0046] In the carboxyl group-containing polymer, the molar ratio of the carboxyl group-containing repeating units to the other repeating units is preferably 10:90 to 90:10, more preferably 15:85 to 85:15, and even more preferably 20:80 to 80:20.

[0047] The weight average molecular weight (Mw) of the carboxy group-containing polymer is preferably 1,000 to 500,000, more preferably 3,000 to 100,000. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0048] Furthermore, if the carboxyl group-containing polymer has a broad molecular weight distribution (Mw / Mn), the presence of low-molecular-weight and high-molecular-weight polymers may result in the appearance of foreign matter on the pattern after exposure, or the pattern shape may be deteriorated. Therefore, since the effects of Mw and Mw / Mn tend to become greater as the pattern rule becomes finer, in order to obtain a resist composition that is suitable for use with fine pattern dimensions, it is preferable that the carboxyl group-containing polymer have a narrow Mw / Mn distribution of 1.0 to 2.0.

[0049] The carboxyl group-containing polymer can be synthesized, for example, by polymerizing a monomer that provides the repeating unit described above in an organic solvent with the addition of a radical polymerization initiator by heating.

[0050] Specific examples of organic solvents used in the polymerization reaction include toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), and γ-butyrolactone (GBL). Specific examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The amount of the polymerization initiator added is preferably 0.01 to 25 mol% based on the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150°C, and more preferably 60 to 100°C. The reaction time is preferably 2 to 24 hours, and more preferably 2 to 12 hours from the viewpoint of production efficiency.

[0051] The polymerization initiator may be added to the monomer solution and then fed to the reaction vessel. Alternatively, an initiator solution may be prepared separately from the monomer solution and then fed to the reaction vessel independently. From the perspective of quality control, it is preferable to prepare the monomer solution and the initiator solution independently and then dropwise add them, since radicals generated from the initiator during the waiting time may cause the polymerization reaction to proceed, resulting in the formation of an ultra-high molecular weight polymer. The acid labile group may be used as is after being introduced into the monomer, or may be protected or partially protected after polymerization. To adjust the molecular weight, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may be used in combination. In this case, the amount of the chain transfer agent added is preferably 0.01 to 20 mol % of the total amount of monomers to be polymerized.

[0052] The amount of each monomer in the monomer solution may be appropriately set so as to achieve the preferred content ratio of the repeating units described above.

[0053] In the resist composition of the present invention, the hypervalent bismuth compound and the carboxyl group-containing polymer are preferably contained in such a molar ratio that the content ratio of the hypervalent bismuth compound to the carboxylic acid-containing repeating units in the polymer is 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. The hypervalent bismuth compound may be used alone, or two or more types may be used in combination. The carboxyl group-containing polymer may be used alone, or two or more types having different composition ratios, Mw, and / or Mw / Mn may be used in combination.

[0054] [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 carboxyl group-containing polymer, 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.

[0055] 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.

[0056] [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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] The resist composition of the present invention contains a hypervalent bismuth compound and a carboxyl group-containing polymer 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.

[0062] The hypervalent bismuth compound is a pentacoordinate compound, as represented by formula (1), in which an aryl group and two carboxylate ligands are bonded. It is believed that when such a pentacoordinate bismuth compound is mixed with a carboxyl group-containing polymer, an exchange of the carboxylate ligands occurs through an equilibrium reaction. If the original carboxylate ligands 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 carboxyl group-containing polymer, and the resulting low-boiling acetic acid is removed to complete the ligand exchange. Because the hypervalent bismuth compound after ligand exchange contains a polymer component, it is possible to form a strong resist film.

[0063] Although such a conjugate of a hypervalent bismuth compound and a carboxyl group-containing polymer may be prepared before film formation, it is preferable to form it during film formation because of its low solvent solubility in most cases. That is, a mixture of a monomer of the hypervalent bismuth compound and a carboxyl group-containing polymer is dissolved in an organic solvent to prepare a resist solution, and a ligand exchange reaction is allowed to proceed during film formation and in the subsequent baking step, thereby forming a resist film in which the polymer is bound to the hypervalent bismuth compound.

[0064] In the laminate of the present invention in which a resist film is formed on a substrate in this manner, the polarity of the hypervalent bismuth compound, which is the main component of the resist film, is changed by decomposition by light, and a pattern is formed by a development step. Note that by appropriately selecting a developer, a positive or negative pattern can be formed.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] [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, or on an underlayer film of a substrate having an underlayer film laminated thereon, a step of exposing the resist film to high-energy rays, and a step of developing the exposed resist film using a developer.

[0069] First, the resist composition of the present invention is applied to a substrate for integrated circuit manufacturing, or to a substrate having a laminated underlayer film (e.g., Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating), or to a substrate for mask circuit manufacturing, or to a substrate having a laminated underlayer film (e.g., CrO, CrON, MoSi2, SiO2), by a suitable coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, or doctor coating, to a coating thickness of 0.01 to 2 μm. This is then prebaked on a hot plate, preferably at 60 to 200°C for 10 seconds to 30 minutes, more preferably at 80 to 180°C for 30 seconds to 20 minutes, to form a resist film. The underlayer film refers to a film formed between the substrate and the resist film in a multilayer resist process. The underlayer film is not particularly limited, and conventionally known underlayer films can be used.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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]

[0075] The present invention will be specifically explained below by showing synthesis examples, examples and comparative examples, but the present invention is not limited to the following examples.

[0076] [1] Polymer synthesis The monomers used in the synthesis of the polymer are as follows: [ka]

[0077] [ka]

[0078] [ka]

[0079] [Synthesis Example 1] Synthesis of Polymer P-1 A monomer-polymerization initiator solution was prepared by placing 56 g of monomer a-1, 105 g of monomer b-1, 5.4 g of V-601 (Fujifilm Wako Pure Chemical Industries, Ltd.), and 180 g of MEK in a flask under a nitrogen atmosphere. 55 g of MEK was placed in a separate flask under a nitrogen atmosphere and heated to 80°C with stirring. The monomer-polymerization initiator solution was then added dropwise over 4 hours. After the addition, the polymerization solution was stirred for 2 hours while maintaining the temperature at 80°C, and then cooled to room temperature. The resulting polymerization solution was added dropwise to 4000 g of vigorously stirred hexane, and the precipitated polymer was filtered. The resulting polymer was washed twice with 1200 g of hexane and then vacuum-dried at 50°C for 20 hours to obtain polymer P-1 as a white powder (yield: 155 g, 96%). The Mw of polymer P-1 was 7700, and the Mw / Mn ratio was 1.82. The Mw is a polystyrene-equivalent value measured by GPC using THF as a solvent. [ka]

[0080] [Synthesis Examples 2 to 10] Synthesis of Polymers P-2 to P-10 The polymers shown in Table 1 below were synthesized in the same manner as in Synthesis Examples, except that the types and blending ratios of the monomers were changed.

[0081] [Table 1]

[0082] [2] 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 carboxyl group-containing polymer in a solvent according to the compositions shown in Table 2 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 3 below, and filtering the mixture through a 0.2 μm Teflon (registered trademark) filter.

[0083] [Table 2]

[0084] [Table 3]

[0085] In Table 2, the hypervalent bismuth compounds (B-1 to B-3) and solvents are as follows. [ka]

[0086] Solvent: PGMEA (propylene glycol monomethyl ether acetate) HBM (2-hydroxyisobutyric acid methyl ester) GBL (γ-butyrolactone)

[0087] In Table 2, the base polymer (BP-1), photoacid generators (PAG-1, PAG-2) and sensitivity adjusters (Q-1, Q-2) are as follows. [ka]

[0088] [ka]

[0089] [ka]

[0090] [3] EUV lithography evaluation (line and space pattern, positive tone development) [Examples 2-1 to 2-12, Comparative Examples 2-1 to 2-3] Each resist composition (R-01 to R-12, 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 4 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), and then subjected to PEB 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 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.

[0091] [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.

[0092] [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.

[0093] [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.

[0094] [Table 4]

[0095] Developer: IPA (isopropyl alcohol) TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0096] [4] EUV lithography evaluation (line and space pattern, negative tone development) [Examples 3-1 to 3-4, Comparative Examples 3-1 to 3-3] Each resist composition (R-13 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 5 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 5 for 60 seconds, and developed for 30 seconds using the developer listed in Table 5 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 5.

[0097] [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.

[0098] [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.

[0099] [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.

[0100] [Table 5]

[0101] Developer: nBA (butyl acetate)

[0102] The results shown in Tables 4 and 5 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.

[0103] [5] EUV lithography evaluation (contact hole pattern) [Examples 4-1 to 4-12, Comparative Examples 4-1 to 4-3] Each resist composition (R-01 to R-12, 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 6 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 for 60 seconds at the temperature listed in Table 6. Development was performed for 30 seconds using the developer listed in Table 6 to obtain a 32 nm hole pattern. The resulting resist patterns were evaluated as follows, and the results are shown in Table 5.

[0104] [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.

[0105] [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.

[0106] [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.

[0107] [Table 6]

[0108] The results shown in Table 6 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 carboxy group-containing polymer, 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 carboxyl group-containing polymer contains a repeating unit represented by the following formula (2): 【Chemistry 2】 (In the formula, R A each independently represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. X A represents a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-X A1 - is. X A1 represents a linear, branched, or cyclic alkylene saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain.

4. A laminate comprising a substrate and a resist film formed on the substrate from the resist composition according to any one of claims 1 to 3.

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

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

7. 7. The pattern forming method according to claim 6, wherein the high-energy beam is an electron beam or extreme ultraviolet light.

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

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

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