Resist composition and pattern forming method

Abstract

The invention relates to a resist composition and a pattern forming method. The present invention addresses the problem of providing: a resist composition which has excellent sensitivity, resolution, and LWR in optical lithography using high-energy rays, is stable, and is easy to handle; and a method for forming a pattern using the resist composition. The resist composition contains a metal complex having a metal atom and a ligand represented by the following formula (1a), (1b) or (1c). In the formula, R1, R2, R3, R4, R5, R6 and R7 are each independently a hydrogen atom, a carbonyl group, or a C1-20 hydrocarbon group which may contain a heteroatom. And * 1 and * 2 represent atomic bonds with metal atoms.

Description

TECHNICAL FIELD

[0001] The present application relates to a resist composition and a pattern forming method. BACKGROUND

[0002] With the expansion of the IoT market, further requirements are made for high integration, high speed, and low power consumption of LSIs, and the miniaturization of pattern rules is also rapidly progressing. In particular, logic devices are leading the miniaturization. As for the most advanced miniaturization technology, mass production of 10 nm node devices obtained by double patterning, triple patterning, and quadruple patterning of ArF immersion lithography is underway, and the exploration of 7 nm node devices obtained by extreme ultraviolet (EUV) lithography of the next generation wavelength of 13.5 nm is progressing.

[0003] With the progress of miniaturization, blurring of the image due to diffusion of acid also becomes a problem (Non-Patent Literature 1). In order to ensure the resolution of fine patterns of 45 nm or less in processing size, it has been proposed that not only the improvement of the dissolution contrast conventionally advocated is important, but also the control of acid diffusion is important (Non-Patent Literature 2). However, since a chemically amplified resist composition improves sensitivity and contrast by diffusion of acid, if acid diffusion is suppressed to the limit by lowering the post-exposure bake (PEB) temperature, or shortening the PEB time, etc., the sensitivity and contrast will be significantly reduced.

[0004] It is effective to add an acid generator that generates a bulky acid to suppress acid diffusion. Then, it has been proposed to copolymerize an onium salt of a polymerizable olefin in a polymer to add an acid generator. However, in the pattern formation of resist films of 16 nm or less in processing size, it is considered that from the viewpoint of acid diffusion, a chemically amplified resist composition cannot perform pattern formation, and the development of a non-chemically amplified resist composition is expected.

[0005] A material for a non-chemically amplified resist composition can be exemplified by polymethyl methacrylate (PMMA). PMMA is a positive resist material that improves the solubility to an organic solvent developer by cleavage of the main chain and reduction of the molecular weight due to electron beam (EB) or EUV irradiation, but has a disadvantage of low etching resistance and a large amount of outgassing at the time of exposure because it does not have a ring structure.

[0006] Hydrogensiloxane (HSQ) is crosslinked by condensation reaction of silanol generated by EB or EUV irradiation, and thereby becomes a material for a negative resist composition that is insoluble in an alkali developer. Also, a chloro-substituted calixarene functions as a material for a negative resist composition. These materials can be used as a pattern transfer material that has a small edge roughness and a very high resolution, and exhibits the resolution limit of an exposure device, because the molecular size before crosslinking is small and there is no blurring due to acid diffusion. However, the sensitivity of these materials is insufficient, and further improvement is required.

[0007] A major cause of difficulty in developing materials for EUV lithography applications can be listed as the small number of photons in EUV exposure. The energy of EUV is much higher than that of ArF excimer laser, and the number of photons in EUV exposure is 1 / 14 of that in ArF exposure. In addition, the size of the pattern formed by EUV exposure is less than half of that by ArF exposure. Therefore, EUV exposure is easily affected by variations in the number of photons. Variations in the number of photons in the region of emitted light of an extremely short wavelength are shot noise, a physical phenomenon, and the effect cannot be eliminated. Therefore, so-called Stochastics is of concern. Discussions are made on how to reduce the effect although the effect of shot noise cannot be eliminated. Due to the effect of shot noise, not only CDU (Critical Dimension Uniformity) and LWR (Line Width Roughness) become large, but also there is a probability of 1 in a million that a hole blocking phenomenon will be observed. If a hole is blocked, the transistor does not operate due to poor conduction, and therefore, the performance of the entire device is adversely affected.

[0008] As a method for reducing the effect of shot noise from the resist aspect, an inorganic resist composition using an element having a large absorption of EUV as a core has been proposed (Patent Literature 1). However, the inorganic resist composition has not been sufficient in terms of relatively high sensitivity so far, and there are many problems such as insufficient solubility in a solvent for the resist composition, storage stability, defects, and the like.

[0009] Non-Patent Literature 3 claims a negative resist composition using a tin compound. This is a non-chemically amplified resist composition using tin element having a high absorption of EUV as a main component, and although Stochastics is improved and sensitivity and resolution are greatly improved, there are difficulties in stability, and there are problems such as degradation in storage of the resist composition, change in performance due to post PEB delay (time elapsed from after PEB to before development: PPD), and the like.

[0010] Prior Art Documents

[0011] Patent Literature

[0012] [Patent Literature 1] Japanese Patent Application Laid-Open (kokai) No. 2015-108781

[0013] Non-Patent Literature

[0014] [Non-Patent Literature 1] SPIE Vol. 5039 p1 (2003)

[0015] [Non-Patent Literature 2] SPIE Vol. 6520 p65203L-1 (2007)

[0016] [Non-Patent Literature 3] SPIE Vol. 9051 p90511B-1 (2014) SUMMARY

[0017] [PROBLEMS TO BE SOLVED BY THE INVENTION]

[0018] The present application has been made in view of the foregoing circumstances, and aims to provide a resist composition which is excellent in sensitivity, resolution, and LWR, stable, and easy to handle, in optical lithography using high-energy rays, particularly in EB lithography and EUV lithography, and to provide a pattern forming method using the resist composition.

[0019] [MEANS FOR SOLVING PROBLEMS]

[0020] As a result of repeated and intensive studies in order to achieve the foregoing object, the present inventors have obtained the following insight, and completed the present application: a resist composition having a metal complex having a specific structure as a main component can provide a resist film which is high in sensitivity, and exhibits excellent resolution and LWR, and is also excellent in stability, and is extremely effective in precise fine processing.

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

[0022] 1. A resist composition comprising:

[0023] a metal complex having a metal atom, and a ligand represented by the following formula (la), (lb), or (lc).

[0024] [Chemical Formula 1]

[0025]

[0026] In the formula, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , and R 7 are each independently a hydrogen atom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which can also have a hetero atom, or a hydrocarbyl group having 1 to 20 carbon atoms which can also have a hetero atom. *1 and *2 represent atomic bonds to the metal atom.

[0027] 2. The resist composition according to 1, wherein the metal atom is zinc.

[0028] 3. The resist composition according to 1 or 2, wherein the metal complex is a zinc tetranuclear cluster represented by the following formula (2a).

[0029] [Chemical Formula 2]

[0030]

[0031] In the formula, X 1 X 2 X 3 X 4 X 5 and X 6 Each is an independent cross-linking ligand, and X 1 X 2 X 3 X 4 X 5 and X 6 At least one of them is a ligand represented by formula (1a), (1b) or (1c).

[0032] 4. A pattern forming method, comprising the following steps:

[0033] A resist film is formed on the substrate using a resist composition as described in any one of 1. to 3.

[0034] The aforementioned resist film was exposed to high-energy rays, and

[0035] The previously exposed resist film is developed to form a resist pattern.

[0036] 5. The pattern forming method as described in 4, wherein the aforementioned high-energy rays are EB or EUV.

[0037] [The effects of the invention]

[0038] The resist composition of the present invention, especially in EB lithography and EUV lithography, takes into account high sensitivity, high resolution, and excellent LWR. In addition, it also has good stability, so it is very useful for the formation of fine patterns. Detailed Implementation

[0039] [Resist Composition]

[0040] The resist composition of the present invention contains a metal complex having metal atoms and predetermined ligands.

[0041] [Metal complex]

[0042] The aforementioned metal complex comprises: a metal atom and a ligand represented by formula (1a), (1b), or (1c). The high bonding energy between the ligand and the metal atom stabilizes the complex. Therefore, the stability of the resist composition over time during storage and the subsequent stability of PEB are improved. That is, the performance degradation caused by PPD is reduced.

[0043] [Chemistry 3]

[0044]

[0045] In equations (1a) to (1c), R 1 R 2 R 3 R 4 R 5 R 6 and R 7 Each group is an alkyl group consisting of 2 to 20 carbon atoms, which may also contain heteroatoms, or an alkyl group consisting of 1 to 20 carbon atoms, which may also contain heteroatoms. The hydrocarbon group and the alkyl carbonyl group mentioned above may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, etc., alkyl groups with 1 to 20 carbon atoms; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornel, tricyclic [5.2.1.0] 2,6 [Cyclic saturated hydrocarbon groups with 3 to 10 carbon atoms, such as decyl, adamantyl, and adamantylmethyl; alkenyl groups with 2 to 20 carbon atoms, such as vinyl and 2-propenyl; aryl groups with 6 to 20 carbon atoms, such as phenyl and naphthyl; and groups obtained by combining them. Furthermore, some or all of the hydrogen atoms in the aforementioned hydrocarbon groups may be replaced by groups containing heteroatoms such as oxygen, sulfur, nitrogen, and halogen atoms, and a portion of the -CH2- group in the aforementioned hydrocarbon groups may also be replaced by groups containing heteroatoms such as oxygen, sulfur, and nitrogen atoms. As a result, groups may contain hydroxyl, cyano, halogen, carbonyl, ether, thioether, ester, sulfonate, carbonate, carbamate, lactone, sulfonyl ring, carboxylic anhydride, etc. In the formula, *1 and *2 represent atomic bonds with metal atoms.]

[0046] In the ligands represented by formulas (1a), (1b), or (1c), *1 and *2 can be bonded to the same metal atom to become chelate ligands, or they can be bonded to different metal atoms to become cross-linked ligands. It is preferable that *1 and *2 are bonded to different metal atoms to become cross-linked ligands. The ligands represented by formulas (1a), (1b), or (1c) can be used alone or in combination of two or more.

[0047] Specific examples of ligands represented by formulas (1a), (1b), or (1c) are shown below, but are not limited thereto. Additionally, in the following formulas, Me is a methyl group.

[0048] [Chemistry 4]

[0049]

[0050] [Chemistry 5]

[0051]

[0052] [Chemical Formula 6]

[0053]

[0054] [Chemical Formula 7]

[0055]

[0056] [Chemical Formula 8]

[0057]

[0058] [Chemical Formula 9]

[0059]

[0060] The aforementioned metal complex can have other ligands in addition to the ligand represented by formula (1a), (1b), or (1c).

[0061] The aforementioned other ligand is not particularly limited and can be a neutral ligand having a coordinating functional group such as an amino group, a carboxyl group, a hydroxyl group, an ether bond, a thiol group, a sulfide bond, a cyano group, a carbonyl group, a phosphine group, an imide group, a pyridine ring, a carbene, or the like, or an anionic ligand such as hydrido, amido, carboxylato, hydroxo, phenoxo, alkoxo, thiolato, cyanato, fluoro, iodo, chloro, bromo, oxo, alkyl, aryl, vinyl, alkinyl, cyclopentadienyl, or the like. Also, the aforementioned other ligand can be a monodentate ligand or a polydentate ligand. Furthermore, the aforementioned other ligand can be a terminal ligand that binds to a single metal atom or a bridging ligand that binds to multiple metal atoms. The aforementioned other ligand preferably uses an anionic ligand, and more preferably uses an anionic bridging ligand. The aforementioned other ligand can be used alone or in combination with two or more

[0062] The aforementioned metal atom is not particularly limited and is preferably an element having a high absorption efficiency for EUV light. Examples of such an element include Co, Ni, Cu, Zn, Ag, In, Sn, Sb, Te, Pt, and the like, and Zn is particularly preferable in view of ease of synthesis, handling, and availability of raw materials. Zinc is very effective for use in EUV lithography because of its high absorption efficiency for EUV light.

[0063] Specific examples of the aforementioned metal complex include those shown below, but are not limited thereto. In the following formulae, Me represents a methyl group.

[0064] [Chemical Formula 10]

[0065]

[0066] When the aforementioned metal complex produces isomers depending on the configuration of the ligands, a mixture of these isomers can be used, or only a single isomer can be used. Furthermore, when the aforementioned metal complex contains multiple ligands, a single metal complex with completely controlled ratios of each ligand can be used, or a mixture of metal complexes with different ratios of each ligand can be used.

[0067] The aforementioned metal complex is particularly well represented by a zinc tetranuclear cluster as shown in formula (2a). Such zinc clusters have excellent sensitivity and resolution due to their high density of zinc atoms with high absorption efficiency for EUV light.

[0068] [Chemistry 11]

[0069]

[0070] In the formula, X 1 X 2 X 3 X 4 X 5 and X 6 Each is an independent cross-linking ligand, and X 1 X 2 X 3 X 4 X 5 and X 6 At least one of them is a ligand represented by formula (1a), (1b), or (1c). X 1 X 2 X 3 X 4 X 5 and X 6 The number of ligands represented by formulas (1a), (1b) or (1c) should preferably be 1 or more and 6 or less, preferably 3 or more and 6 or less, and especially preferably 6.

[0071] Specific examples of zinc tetranuclear clusters represented by formula (2a) are shown below, but are not limited thereto. Additionally, in the following formula, Me represents a methyl group.

[0072] [Chemistry 12]

[0073]

[0074] [Chemistry 13]

[0075]

[0076] [Chemistry 14]

[0077]

[0078] [Chemical 15]

[0079]

[0080] The aforementioned metal complex can be used alone or in combination with two or more.

[0081] [Organic solvent]

[0082] The resist composition of the present application contains an organic solvent. The organic solvent is not particularly limited as long as it can dissolve the aforementioned metal complex and form a film. Examples of such an organic solvent include ketones such as cyclohexanone and methyl-2-n-amyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 2-hydroxyisobutyrate, t-butyl acetate, cyclohexyl acetate, t-butyl propionate, and propylene glycol mono-t-butyl ether acetate; lactones such as γ-butyrolactone; carboxylic acids such as acetic acid and propionic acid; aromatic compounds such as toluene, xylene, cresol, anisole, and benzyl fluoride; halogenated hydrocarbons such as dichloromethane, chloroform, and carbon tetrachloride; and a mixture thereof.

[0083] The content of the aforementioned organic solvent is preferably 200 to 20,000 parts by mass and more preferably 500 to 15,000 parts by mass with respect to 100 parts by mass of the aforementioned metal complex.

[0084] It is presumed that the resist composition of the present application changes the development resistance between the exposed portion and the unexposed portion and exhibits contrast by the photodecomposition of the metal complex as the main component and the subsequent agglomeration or crosslinking reaction between the partially destroyed metal complexes. This reaction is not a catalytic reaction, and therefore the resist composition of the present application functions as a non-chemically amplified resist composition. Thus, resolution can be performed even in a fine region where it is difficult to form a pattern with a known chemically amplified resist composition using a polymeric compound as the main component. In particular, in EUV lithography, since the aforementioned metal atom has a high EUV absorption ability, it becomes a resist composition with improved randomness and excellent sensitivity and LWR. Also, the aforementioned metal complex converges to a thermally stable structure, and therefore the storage stability is also excellent. Also, the performance does not change greatly with time after PEB.

[0085] [Photoacid generator]

[0086] The resist composition of the present application can also contain a photoacid generator as another component in addition to the metal complex and the organic solvent. By using a photoacid generator, it is expected to cause acid generation at the exposed portion and to promote the crosslinking reaction of the metal complex. Such a photoacid generator, if it is one that generates acid upon irradiation of high-energy rays, is not particularly limited, and known ones used for known chemically amplified resist compositions can be used, and it is preferable to be one that generates sulfonic acid, imide acid, or methylated acid. Examples of the desirable photoacid generator include a sulfonium salt, a sulfoxonium salt, a sulfonyl diazomethane, an N-sulfonyloxy imide, an oxime-O-sulfonic acid ester type acid generator, and the like. Specific examples of the aforementioned photoacid generator include those described in paragraphs

[0122] to

[0142] of Japanese Patent Application Publication No. 2008-111103, and those described in paragraphs

[0127] to

[0193] of Japanese Patent Application Publication No. 2022-163697.

[0087] When the resist composition of the present application contains the aforementioned photoacid generator, the content thereof is preferably 0.01 to 20 mass% in the total solid components. In addition, the solid components in the present application refer to the total of all components of the resist composition except for the solvent. The aforementioned photoacid generator can be used alone as one kind, or two or more kinds can be used in combination.

[0088] [Radical Scavenger]

[0089] The resist composition of the present application can also contain a radical scavenger as another component. By adding a radical scavenger, it is possible to control the photoreaction in optical lithography and adjust the sensitivity.

[0090] The aforementioned radical scavenger can use a hindered phenol, a quinone, a hindered amine, a thiol compound, and the like. Specific examples of the aforementioned hindered phenol include dibutylhydroxytoluene, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), and the like. Specific examples of the aforementioned quinone include 4-methoxyphenol (methoquinone), hydroquinone, and the like. Specific examples of the aforementioned hindered amine include 2,2,6,6-tetramethylpiperidine, 2,2,6,6-tetramethylpiperidine-N-oxyl, and the like. Specific examples of the aforementioned thiol include dodecanethiol, hexadecanethiol, and the like.

[0091] When the resist composition of the present application contains the aforementioned radical scavenger, the content thereof is preferably 0.01 to 10 mass% in the total solid components. The aforementioned radical scavenger can be used alone as one kind, or two or more kinds can be used in combination.

[0092] [Surfactant]

[0093] The resist composition of the present application can also contain a surfactant as another component. The aforementioned surfactant can be one described in Japanese Patent Application Publication No. 2010-215608, Japanese Patent Application Publication No. 2011-16746. Among these, FC-4430 (manufactured by 3M Company), SURFLON (registered trademark) S-381 (manufactured by AGC SEIMI CHEMICAL CO., LTD.), OLFINE (registered trademark) E1004 (manufactured by NISSHIN KAGAKU CO., LTD.), KH-20, KH-30 (manufactured by AGC SEIMI CHEMICAL CO., LTD.), an oxetane ring-opening polymer represented by the following formula (surf-1), and the like are preferable.

[0094] [Chemical Formula 16]

[0095]

[0096] In formula (surf-1), R is an aliphatic group having a valence of 2 to 4 and a carbon number of 2 to 5. In the aforementioned aliphatic group, in the case of a valence of 2, ethylene, 1,4-butylene, 1,2-propylene, 2,2-dimethyl-1,3-propylene, 1,5-pentylene, and the like can be exemplified, and in the case of a valence of 3 or 4, the following can be exemplified.

[0097] [Chemical Formula 17]

[0098]

[0099] In the formula, the dotted line is an atomic bond, and each is a partial structure derived from glycerol, trimethylol ethane, trimethylol propane, or neopentyl tetrol.

[0100] Among these, 1,4-butylene, 2,2-dimethyl-1,3-propylene, and the like are preferable.

[0101] Rf is a trifluoromethyl group or a pentafluoroethyl group, and is preferably a trifluoromethyl group. m is an integer of 0 to 3, n is an integer of 1 to 4, the sum of n and m is the valence of R, and is an integer of 2 to 4. A is 1. B is an integer of 2 to 25, and is preferably an integer of 4 to 20. C is an integer of 0 to 10, and is preferably 0 or 1. Also, the respective constituent units in formula (surf-1) are not limited in their arrangement, and can be bonded in blocks or randomly. For the production of the surfactant of the partially fluorinated oxetane ring-opening polymer system, see, for example, U.S. Patent No. 5650483.

[0102] When the resist composition of the present application contains the aforementioned surfactant, the content thereof is preferably 0.001 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, with respect to 100 parts by mass of the aforementioned metal complex. The aforementioned surfactant can be used alone or in combination with two or more kinds.

[0103] [Pattern forming method]

[0104] When the resist composition of the present application is used for various integrated circuit manufacturing, a known photolithography technique can be used. For example, as the pattern forming method, a method including the steps of forming a resist film on a substrate using the aforementioned resist composition, exposing the aforementioned resist film to high-energy rays, and developing the aforementioned exposed resist film can be exemplified.

[0105] First, the resist composition of the present application is coated on a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflection film, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.) in a manner that the coating film thickness becomes 0.01 to 2 μm using a suitable coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, blade coating, etc. It is heated on a hot plate. It is preferably heated at 60 to 200°C for 10 seconds to 30 minutes and more preferably at 80 to 180°C for 30 seconds to 20 minutes to form a resist film.

[0106] Then, the aforementioned resist film is exposed to high-energy rays. The aforementioned high-energy rays can be exemplified by ultraviolet rays, far ultraviolet rays, EB, EUV having a wavelength of 3 to 15 nm, X-rays, soft X-rays, excimer laser, γ-rays, synchrotron radiation, etc. When the aforementioned high-energy rays are ultraviolet rays, far ultraviolet rays, EUV, X-rays, soft X-rays, excimer laser, γ-rays, synchrotron radiation, etc., they are irradiated directly or using a mask for forming a pattern of interest in a manner that the exposure dose becomes preferably about 1 to 200 mJ / cm 2 and more preferably about 10 to 150 mJ / cm 2 . When the aforementioned high-energy rays are EB, they are drawn directly or using a mask for forming a pattern of interest in a manner that the exposure dose becomes preferably about 0.1 to 5000 μC / cm 2 and more preferably about 0.5 to 4000 μC / cm 2 . In addition, the resist composition of the present application is particularly suitable for fine patterning using EB or EUV among high-energy rays.

[0107] In order to promote the reaction after photodecomposition or to complete it, PEB can also be performed. When PEB is performed, it is preferably performed on a hot plate or in an oven after exposure in a manner that the temperature is preferably 30 to 200°C for 10 seconds to 30 minutes and more preferably 60 to 180°C for 30 seconds to 20 minutes.

[0108] The method of development performed after exposure or after PEB is any of wet development or dry development. In the case of wet development, alkali development or organic solvent development is used. In the case of the resist composition of the present application, organic solvent development is preferable. Wet development is performed by a method such as dip method, puddle method, spray method, and the like, on the exposed resist film for 3 seconds to 3 minutes, more preferably 5 seconds to 2 minutes, to form a desired pattern. The resist composition of the present application is negative type, and thus the portion irradiated with light is not dissolved in the developer, and the unexposed portion is dissolved.

[0109] As the organic solvent used as the developer, 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butenyl acetate, isoamyl acetate, propyl formate, cyclohexyl acetate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentalenate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, isoamyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, ethyl phenylacetate, benzyl formate, phenethyl formate, methyl 3-phenylpropionate, benzyl propionate, 2-phenylethyl acetate, dichloromethane, chloroform, carbon tetrachloride, formic acid, acetic acid, propionic acid, and the like can be used. These organic solvents can be used singly or in combination of two or more.

[0110] After development, if necessary, rinsing is performed. The rinsing solution is preferably a solvent which is miscible with the developer and does not dissolve the resist film. As such a solvent, an alcohol having 3 to 10 carbon atoms, an ether compound having 8 to 12 carbon atoms, an alkane, alkene, alkyne, or aromatic solvent having 6 to 12 carbon atoms can be desirably used.

[0111] Specific examples of the alcohol having 3 to 10 carbon atoms include n-propanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, t-amyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, 1-octanol, and the like.

[0112] Specific examples of the aforementioned ether compound having a carbon number of 8 to 12 include di-n-butyl ether, diisobutyl ether, di(secondary butyl) ether, di-n-pentyl ether, diisopentyl ether, di(secondary pentyl) ether, di(tertiary pentyl) ether, di-n-hexyl ether, and the like.

[0113] Specific examples of the aforementioned alkane having a carbon number of 6 to 12 include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, cyclononane, and the like. Specific examples of the aforementioned alkene having a carbon number of 6 to 12 include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, cyclooctene, and the like. Specific examples of the aforementioned alkyne having a carbon number of 6 to 12 include hexyne, heptyne, octyne, and the like.

[0114] Specific examples of the aforementioned aromatic solvent include toluene, xylene, ethylbenzene, cumene, tert-butylbenzene, mesitylene, and the like.

[0115] By performing the rinsing, collapse of the resist pattern and occurrence of defects can be reduced. Also, the rinsing is not essential, and by not performing the rinsing, the amount of solvent used can be reduced.

[0116] The developing method in the pattern forming method of the present application can also use dry development. Dry development refers to a developing method in which either the exposed portion or the unexposed portion is removed by an etching step using a gas. In the case of the present application, by removing the unexposed portion using an etching gas, a desired pattern can be formed. Dry etching can desirably use a gas containing nitrogen, helium, argon, carbon dioxide, carbon monoxide for dilution in a gas containing oxygen, hydrogen, ammonia, halogen, and the like.

[0117] [Examples]

[0118] Hereinafter, the present application will be specifically described by examples and comparative examples, but the present application is not limited to the following examples.

[0119] The metal complex used in the examples is represented by the following formula (M-1) to (M-3).

[0120] [Chemical 18]

[0121]

[0122] The metal complex represented by formula (M-1) was synthesized with reference to Communications Chemistry, 2021, 4, 133. The metal complex represented by (M-2) was synthesized with reference to Inorganic Chemistry, 2022, 61, 7869-7877. The metal complex represented by (M-3) was synthesized with reference to Nature Communications, 2016, 7, 13008.

[0123] [1] Preparation of resist composition

[0124] [Examples 1-1 to 1-5, Comparative Example 1-1]

[0125] Each component was dissolved in a solvent with the composition shown in Table 1 below, and the obtained solution was filtered with a Teflon (registered trademark) filter of 0.2 pm to thereby produce the resist compositions R-1 to R-5 of the present application and the comparative resist composition CR-1.

[0126] [Table 1]

[0127]

[0128]

[0129] In Table 1, Component A is a metal complex, Component B is a photoacid generator, and Component C is a radical scavenger. The structures of the compounds (M-1) to (M-3) used as Component A are as described above. The details of Components B and C are described below.

[0130] • P-1: triphenylsulfonium p-toluenesulfonate

[0131] • Sc-1: dibutylhydroxytoluene

[0132] In Table 1, CM-1 (tin compound) used in the comparative example was synthesized following Angewandte Chemie, International Edition (2017), 56(34), 10140-10144. The structure of CM-1 is described below.

[0133] [Chemical 19]

[0134]

[0135] [2] EB lithography evaluation

[0136] [Examples 2-1 to 2-5, Comparative Example 2-1]

[0137] The resist compositions (R-1 to R-5, CR-1) were spin-coated on a Si substrate on which an antireflection film DUV-42 manufactured by Nissan Chemical Industries, Ltd. was formed to a film thickness of 60 nm, and a prebake was performed at 100°C for 60 seconds using a hot plate to obtain a resist film having a film thickness of 40 nm. The resist film was exposed using an EB drawing device (ELS-F125, accelerating voltage 125 kV) manufactured by Elionix, Inc., and PEB was performed at the temperatures described in Table 2 on a hot plate for 60 seconds, and development was performed using 2-heptanone as a developer for 30 seconds, whereby a pattern was formed. As a result, a line-and-space (LS) pattern having a space width of 20 nm and a pitch of 40 nm was obtained. The sensitivity, LWR, and limit resolution were evaluated for the obtained LS pattern in accordance with the following methods. The results are shown in Table 2.

[0138] [evaluation of sensitivity]

[0139] The aforementioned LS pattern was observed using an electron microscope, and the optimum exposure dose Eop (μC / cm2) at which a LS pattern having a space width of 20 nm and a pitch of 40 nm could be obtained was determined, and this was taken as the sensitivity. 2

[0140] [evaluation of LWR]

[0141] The size of 10 places of the LS pattern obtained by irradiation at the optimum exposure dose was measured in the length direction of the space width using a CD-SEM (CG-5000) manufactured by Hitachi High-Technologies Corporation, and the value 3 times the standard deviation (σ) was determined from the results, and this was taken as the LWR. The smaller this value, the more uniform the space width of the pattern and the smaller the roughness.

[0142] [evaluation of limit resolution]

[0143] The limit line width (nm) at which resolution was performed when the exposure dose was gradually increased in small amounts from the optimum exposure dose to form a pattern was determined using a length SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limit resolution (nm). The smaller this value, the better the limit resolution, and the finer the pattern that can be formed.

[0144] [evaluation of post-exposure delay stability]

[0145] After exposure at the optimum exposure dose, PEB and development were performed using the aforementioned conditions. At this time, a wafer on which development was performed without delay after PEB and a pattern was formed (PPD0h), and a wafer on which development was performed after 6 hours of delay after PEB and a pattern was formed (PPD6h) were prepared. The line width of these wafers was determined using a length SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and the change (ΔPPD) in line width (CD) due to delay after exposure was determined. The results are shown in Table 2.

[0146] [table 2]​

[0147]

[0148]

[0149] From the results shown in Table 2, it is found that the resist composition of the present application is excellent in LWR and in ultimate resolution in the negative pattern formation using the organic solvent development of EB lithography. Further, it is confirmed that even if the post-exposure baking is performed, the CD change is small, and the pattern formation is stable. Also, in the resist composition of the present application, since the zinc atom having a high EUV light absorption ability is densely contained, a high sensitivity in EUV lithography is expected.

[0150] [3] Evaluation of storage stability

[0151] [Examples 3-1 to 3-5, Comparative Example 3-1]

[0152] The resist compositions R-1 to R-5 and CR-1 were visually observed for the occurrence of precipitation when left to stand for a certain period of time at normal temperature (20 ± 5°C). At this time, those which could be stored without the occurrence of precipitation for 6 months or more were evaluated as O, and those which had the occurrence of precipitation before 6 months were evaluated as X. The results are shown in Table 3.

[0153] [Table 3]

[0154] Resist composition Storage stability Example 3-1 R-1 ○ Example 3-2 R-2 ○ Example 3-3 R-3 ○ Example 3-4 R-4 ○ Example 3-5 R-5 ○ Comparative Example 3-1 CR-1 ×

[0155] As shown in the results of Table 3, it is found that the resist composition of the present application is excellent in storage stability and is good in handling.

Claims

1. A resist composition, comprising: a metal complex having a metal atom, and a ligand represented by the following formula (la), (lb) or (lc); wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , and R 7 are each independently a hydrogen atom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which can also contain a hetero atom, or a hydrocarbyl group having 1 to 20 carbon atoms which can also contain a hetero atom; and *1 and *2 represent a bond with a metal atom.

2. The resist composition according to claim 1, wherein, the metal atom is zinc.

3. The resist composition according to claim 1, wherein, the metal complex is a zinc tetranuclear cluster represented by the following formula (2a); wherein X 1 , X 2 , X 3 , X 4 , X 5 , and X 6 are each independently a cross-linking ligand, and at least one of X 1 , X 2 , X 3 , X 4 , X 5 , and X 6 is a ligand represented by formula (1a), (1b), or (1c).

4. A pattern forming method, having the following steps: forming a resist film on a substrate using the resist composition according to any one of claims 1 to 3, exposing the resist film to a high-energy ray, and developing the exposed resist film to form a resist pattern.

5. The pattern forming process according to claim 4, wherein the high-energy ray is EB or EUV.

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