High-valence bismuth compound, resist composition, and pattern forming method

Abstract

The invention relates to a high-valence bismuth compound, a resist composition and a pattern forming method. The present invention addresses the problem of providing a non-chemically amplified resist composition having excellent sensitivity and resolution in optical lithography using high-energy rays, particularly electron beam (EB) lithography and EUV lithography, and a pattern forming method using the resist composition. [Solution] A high-valence bismuth compound represented by formula (1).

Description

Technical Field

[0001] This invention relates to high-valence bismuth compounds, resist compositions, and methods for pattern formation. Background Technology

[0002] With the expansion of the IoT market, there is a growing demand for high integration, high speed, and low power consumption in LSI (Light Silica) technology, and the miniaturization of patterning is also progressing rapidly. In particular, logic devices are leading the way in miniaturization. Regarding the most advanced miniaturization technologies, mass production of 10nm node devices using ArF immersion lithography with dual, triple, and quadruple patterning is already underway. Furthermore, research is progressing on next-generation 7nm node devices using extreme ultraviolet (EUV) lithography with a wavelength of 13.5nm.

[0003] As miniaturization progresses, image blurring caused by acid diffusion has become a problem (Non-Patent Literature 1). To ensure the resolution of fine patterns with a processing size of less than 45 nm, it has been proposed that not only is the improvement of dissolution contrast, as previously advocated, important, but also the control of acid diffusion is crucial (Non-Patent Literature 2). However, since chemically amplified resist compositions improve sensitivity and contrast through acid diffusion, if acid diffusion is suppressed to the limit by lowering the post-exposure baking (PEB) temperature or shortening the PEB time, sensitivity and contrast will be significantly reduced.

[0004] Adding acid-generating agents that produce bulky acids is effective in suppressing acid diffusion. Therefore, it has been proposed to use onium salts of polymerizable olefins as acid-generating agents in polymer copolymerization. However, considering acid diffusion, in the patterning of resist films with dimensions smaller than 16 nm, it is believed that chemically amplified resist compositions are no longer suitable for patterning, and the development of non-chemically amplified resist compositions is desired.

[0005] Materials used in non-chemically amplified resist compositions include polymethyl methacrylate (PMMA). PMMA is a positive resist composition that improves solubility in organic solvent developers by breaking down the main chain and reducing the molecular weight through EUV irradiation.

[0006] Hydrosilsesquioxane (HSQ) is a cross-linked material produced by the condensation reaction of silanols under EUV irradiation, thereby becoming a negative resist composition insoluble in alkaline developers. Chlorinated calixarnes also function as negative resist compositions. These negative resist compositions, due to their small molecular size before cross-linking and the absence of blurring caused by acid diffusion, can be used as pattern transfer materials with low edge roughness and very high resolution, exhibiting the resolving limits of exposure devices. However, the sensitivity of these materials is insufficient and further improvement is needed.

[0007] One of the main reasons hindering material development for EUV lithography applications is the low photon count in EUV exposure. EUV energy is significantly higher than ArF excimer lasers, and the photon count in EUV exposure is only one-fourteenth that of ArF exposure. Furthermore, the size of patterns formed by EUV exposure is less than half that of ArF exposure. Therefore, EUV exposure is susceptible to variations in photon count. These variations in photon count in extremely short wavelength emission regions constitute shot noise, a physical phenomenon that cannot be eliminated. Consequently, stochastics have become a focus. While shot noise cannot be eliminated, the discussion revolves around reducing its impact. Shot noise not only increases dimensional uniformity (CDU) and linewidth roughness (LWR), but also presents a one in a million chance of observing hole blockage. Hole blockage leads to poor conductivity and transistor malfunction, negatively impacting overall device performance. When considering practical sensitivity, resist compositions with PMMA and HSQ as the main components are significantly affected by stochastics and may not achieve the desired resolution.

[0008] As a method to reduce the impact of shot noise from the resist aspect, introducing elements with high absorption of EUV light has attracted attention. Patent Document 1 proposes a chemically amplified resist composition containing bismuth atoms with high absorption of EUV light. However, as mentioned above, chemically amplified resists cannot achieve excellent resolution in EUV lithography, which will continue to process increasingly smaller dimensions.

[0009] Patent document 2 claims to use an organic solvent negative resist composition containing tin compounds. This is because tin, which has high absorption under EUV light, is used as the main component, thus improving stochastics and achieving high sensitivity and high resolution. However, such a metal resist has many problems, such as insufficient solubility in the solvent used for resisting, insufficient storage stability due to excessive reactivity, and defects caused by residues after etching.

[0010] Existing technical documents

[0011] Patent documents

[0012] [Patent Document 1] Japanese Patent Application Publication No. 2018005224

[0013] [Patent Document 2] Japanese Patent Publication No. 2021503482

[0014] Non-patent literature

[0015] [Non-Patent Literature 1] SPIE Vol.5039p1 (2003)

[0016] [Non-Patent Literature 2] SPIE Vol.6520p65203L-1(2007) Summary of the Invention

[0017] [The problem that the invention aims to solve]

[0018] The present invention was made in view of the foregoing circumstances, and aims to provide a non-chemically amplified resist composition with excellent sensitivity and resolution in optical lithography using high-energy rays, especially in electron beam (EB) lithography and EUV lithography, and to provide a patterning method using the resist composition.

[0019] [Methods for solving the problem]

[0020] After repeated and in-depth explorations to achieve the aforementioned objectives, the inventors have obtained the following insights, and thus completed this invention: a resist composition with a high-valent bismuth compound having aryl groups substituted with polymerizable groups as the main component can provide a resist film with extremely high sensitivity and excellent resolution, which is extremely effective in precision micro-machining.

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

[0022] 1. A high-valence bismuth compound, represented by the following formula (1).

[0023] [Chemistry 1]

[0024]

[0025] In the formula, R 1 and R 2 Each group consists independently of a halogen atom, or may contain heteroatoms, and is a hydrocarbon group with 1 to 10 carbon atoms. Also, R 1 and R 2 They can also bond to each other and form rings together with the carbon atoms they are bonded to and the atoms between those carbon atoms.

[0026] A 1 A 2 and A 3 Each is independently a hydrocarbon group with 2 to 20 carbon atoms containing a polymerizable functional group, and the hydrocarbon group may also contain heteroatoms.

[0027] Ar 1 Ar 2 and Ar 3 Each is an arylene with 6 to 20 carbon atoms, and in this arylene, some or all of the hydrogen atoms on its aromatic ring may be replaced by halogen atoms or hydrocarbon groups with 1 to 20 carbon atoms that may contain heteroatoms.

[0028] 2. As in 1. high-valence bismuth compounds, where A 1A 2 and A 3 It can be acryloyloxy, methacryloyloxy, or may contain a cycloalkenyl group with 3 to 20 heteroatoms, a cycloalkenyloxy group with 3 to 20 heteroatoms, a cycloalkenylcarbonyloxy group with 3 to 20 heteroatoms, an alkenyl group with 2 to 20 heteroatoms, or an alkenyloxy group with 2 to 20 heteroatoms.

[0029] 3. A resist composition comprising a high-valent bismuth compound such as 1. or 2. and a solvent.

[0030] 4. As in 3, the resist composition also contains free radical scavengers.

[0031] 5. As in 3 or 4, the resist composition also contains surfactants.

[0032] 6. 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 3. to 5.

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

[0035] The previously exposed resist film is developed using an organic solvent as the developer, which dissolves the unexposed areas and forms a negative pattern in which the exposed areas do not dissolve.

[0036] [The effects of the invention]

[0037] The resist composition of the present invention is particularly useful in EB lithography and EUV lithography, as it combines high sensitivity and high resolution and is used to form fine patterns. Detailed Implementation

[0038] [High-valent bismuth compounds]

[0039] High-valence bismuth compounds are a general term for bismuth compounds that have valence electrons that exceed the octet rule. Examples of high-valence bismuth compounds include pentacoordinate bismuth compounds with an oxidation state of +5.

[0040] The high-valence bismuth compound of the present invention is a five-coordinate high-valence bismuth compound represented by the following formula (1).

[0041] [Chemistry 2]

[0042]

[0043] In equation (1), R 1 and R 2 Each group consists independently of a halogen atom, or may contain heteroatoms, and is a hydrocarbon group with 1 to 10 carbon atoms. Also, R 1and R 2 They can also bond to each other and form rings together with the carbon atoms they are bonded to and the atoms between those carbon atoms.

[0044] Specific examples of the aforementioned halogen atoms include: fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.

[0045] The aforementioned hydrocarbon groups can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include: methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, and other alkyl groups with 1 to 10 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 and adamantyl; alkenyl groups with 2 to 10 carbon atoms, such as vinyl and 2-propenyl; aryl groups with 6 to 10 carbon atoms, such as phenyl and naphthyl; and groups obtained by combining these. 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, or 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, or nitrogen atoms. As a result, groups may contain hydroxyl, cyano, halogen, carbonyl, ether, thioether, ester, sulfonate, carbonate, carbamate, lactone, sulopentabin, carboxylic anhydride, etc. Among these, R...] 1 and R 2 It should preferably be a hydrocarbon group with 1 to 4 carbon atoms.

[0046] In equation (1), A 1 A 2 and A 3 Each is independently a hydrocarbon group with 2 to 20 carbon atoms containing a polymerizable functional group, and the hydrocarbon group may also contain heteroatoms.

[0047] A 1 A 2 and A 3 It is preferably acryloyloxy, methacryloyloxy, or may contain a cycloalkenyl group with 3 to 20 carbon atoms, a cycloalkenyloxy group with 3 to 20 carbon atoms, a cycloalkenylcarbonyloxy group with 3 to 20 carbon atoms, an alkenyl group with 2 to 20 carbon atoms, or an alkenyloxy group with 2 to 20 carbon atoms.

[0048] A 1 A 2 and A 3 Specific examples of the groups represented can be listed below, but are not limited to. Additionally, in the following formula, the dashed line represents Ar... 1Ar 2 Or Ar 3 Atomic bonds.

[0049] [Chemistry 3]

[0050]

[0051] In equation (1), Ar 1 Ar 2 and Ar 3 Each aryl group is independently composed of 6 to 20 carbon atoms, and in this aryl group, some or all of the hydrogen atoms on the aromatic ring may be replaced by a halogen atom or a hydrocarbon group containing heteroatoms of 1 to 20 carbon atoms. Examples of the aforementioned aryl groups include: phenylene, naphthylene, anthracenediyl, etc. 1 Ar 2 and Ar 3 It is preferable to use phenylene or naphthylene, with phenylene being more preferred, and 1,4-phenylene being even more preferred.

[0052] Specific examples of high-valence bismuth compounds represented by equation (1) are listed below, but are not limited thereto.

[0053] [Chemistry 4]

[0054]

[0055] [Chemistry 5]

[0056]

[0057] [Chemistry 6]

[0058]

[0059] [Chemistry 7]

[0060]

[0061] [Resist Composition]

[0062] The resist composition of the present invention contains the aforementioned high-valence bismuth compound as the main component.

[0063] The resist composition of the present invention further contains an organic solvent. There are no particular limitations on whether the aforementioned organic solvent is capable of dissolving the aforementioned high-valence bismuth compound and forming a film. Specific examples of the aforementioned organic solvents include: ketones such as cyclohexanone, methyl-2-n-pentyl ketone, and methyl isopentyl 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; 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, tert-butyl acetate, tert-butyl propionate, and propylene glycol monotert-butyl ether acetate; carboxylic acids such as formic acid, acetic acid, and propionic acid; lactones such as γ-butyrolactone, and their mixed solvents.

[0064] The content of the aforementioned organic solvent, relative to 100 parts by mass of all solid components in the resist composition, is preferably 200 to 10,000 parts by mass. Furthermore, in this invention, "solid components" refers to all components of the resist composition, excluding the solvent. The aforementioned organic solvent may be used alone or in combination with two or more other solvents.

[0065] The resist composition of the present invention may also contain free radical scavengers as other components. By including free radical scavengers, the photoresponse in optical lithography can be controlled, and the sensitivity can be adjusted.

[0066] Examples of such free radical scavengers include hindered phenols, quinones, hindered amines, and thiols. Specifically, examples of hindered phenols include butylated hydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Examples of quinones include 4-methoxyphenol and hydroquinone. Examples of hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidine-N-oxy radical. Examples of thiols include dodecanethiol and hexadecanethiol. When the resist composition of the present invention contains the aforementioned free radical scavengers, their content in the total solid components is preferably 0.01 to 10% by mass. One of the aforementioned free radical scavengers may be used alone, or two or more may be used in combination.

[0067] The resist composition of the present invention may also contain surfactants as other components. Examples of such surfactants include FC-4432, FC-4430 (manufactured by 3M), or PF-636, PF-656, PF-6320, PF-6520 (manufactured by OMNOVA). When the resist composition of the present invention contains a surfactant, its content relative to 100 parts by weight of the aforementioned high-valent bismuth compound is preferably 0.001 to 20 parts by weight, more preferably 0.1 to 10 parts by weight. One of the aforementioned surfactants may be used alone, or two or more may be used in combination.

[0068] The resist composition of the present invention, as described above, uses a high-valent bismuth compound as the main component and does not contain known polymers (base polymers) containing acid-dependent unstable groups, such as those found in chemically amplified resist compositions, or molecular resist compositions containing photoacid generators. Furthermore, the base polymer refers to the polymer contained in the resist composition, and is the component (main component) with the largest quantity among the components other than the solvent. Also, in resist compositions containing a base polymer, the base polymer is a polymer whose solubility in the developer is altered by the action of the acid generated from the photoacid generator. However, although the resist composition of the present invention does not contain the aforementioned base polymer, it can still change the solubility in the developer in both unexposed and exposed areas by exposure, particularly EB and EUV, and form patterns. The mechanism is not fully elucidated, but phenomena such as the following can be speculated.

[0069] The high-valent bismuth compound used in this invention is a 5-coordinate compound represented by formula (1), consisting of an aryl group and two carboxylic acid ester coordinating bonds with remaining bismuth atoms. In such a 5-coordinate bismuth compound, the carboxyl group undergoes radical dissociation due to EUV exposure, while the polymerizable groups on the aryl group undergo radical polymerization due to the generated carboxylic acid ester radicals, thereby increasing the molecular weight and forming a robust resist film.

[0070] In this way, a high-valence bismuth compound, which is the main component of the resist film, is formed on the substrate. It decomposes under light, thereby changing its polarity, and a negative pattern is formed by the development step.

[0071] Based on the foregoing speculation, the resist composition of the present invention can be considered a non-chemically amplified resist composition. Therefore, the image blurring due to acid diffusion, which is observable in known chemically amplified resist compositions (composed of a base polymer and a photoacid generator), does not occur, and fine patterns can be distinguished by using the resist composition of the present invention.

[0072] The resist composition of this invention is particularly effective in EUV lithography. This is due to the presence of bismuth atoms with high absorption capacity for EUV light. In other words, shot noise is reduced, and higher resolution and lower LWR can be achieved.

[0073] In recent years, EUV resist compositions capable of forming fine patterns have included metal resists with tin compounds, which, like bismuth atoms, have high EUV light absorption capabilities as their main components (e.g., Patent Document 2). However, such metal resists suffer from problems such as insufficient solubility in coating solvents and poor storage stability. On the other hand, the resist composition of the present invention exhibits excellent solvent solubility. Furthermore, the resist composition of the present invention is applicable to negative modes, thus having a wide range of uses.

[0074] [Pattern Formation Method]

[0075] When the resist composition of the present invention is used in the manufacture of various integrated circuits, known photolithography techniques can be used. For example, in terms of pattern formation methods, a method comprising the following steps can be listed: 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 using an organic solvent as a developer to form a negative pattern in which the unexposed areas are dissolved and the exposed areas are not dissolved.

[0076] First, the resist composition of the present invention is coated onto a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective film, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.) using a suitable coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, or blade coating, with a coating film thickness of 0.01 to 2 μm. The substrate is then pre-baked on a hot plate, preferably at 60 to 200°C for 10 to 30 seconds, and more preferably at 80 to 180°C for 30 to 20 seconds, to form a resist film.

[0077] Then, the aforementioned photoresist film is exposed using high-energy radiation. Examples of such high-energy radiation include: ultraviolet light, far-ultraviolet light, EB, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, and synchrotron radiation. When using ultraviolet light, far-ultraviolet light, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, or synchrotron radiation, the exposure dose should be approximately 1–300 mJ / cm², either directly or using a mask used to form the desired pattern. 2 And preferably, it should be approximately 10–200 mJ / cm³. 2 Irradiation is performed in a manner that allows for direct exposure or by using a mask to form the desired pattern. When using EB (Extracorporeal Electron Microwave Oxide) for high-energy radiation, the exposure should be approximately 0.1–5000 μC / cm². 2 And preferably, it is about 0.5 to 4000 μC / cm. 2 The resist composition of the present invention is particularly suitable for fine patterning using EB or EUV, especially in high-energy radiation.

[0078] The resist composition of the present invention requires post-exposure baking (PEB). In this case, it is preferably carried out on a heated plate or in an oven at 30-120°C for 10-30 seconds, and more preferably at 60-100°C for 30-20 seconds.

[0079] After exposure or PEB, an organic solvent is used as the developer to form a negative pattern that dissolves the unexposed areas but not the exposed areas. Examples of developers used in this process include: 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methyl acetophenone, isopropanol, n-butanol, n-pentanol, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butyl acetate, isoamyl acetate, propyl formate, butyl formate, isobutyl formate, amyl formate, methyl valerate, methyl valerate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, emulsion... 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, ethyl 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, 4-methyl-2-pentanol, etc. These developers can be used alone or in combination of two or more.

[0080] After development, rinsing should be performed as needed. The rinsing solution should ideally be a solvent that is miscible with the developer and does not dissolve the resist film. Suitable solvents include alcohols with 3 to 10 carbon atoms, ether compounds with 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents with 6 to 12 carbon atoms. Alternatively, water can be used instead of organic solvents as the rinsing solution.

[0081] By performing rinsing, the collapse of the resist pattern and the occurrence of defects can be reduced. Furthermore, rinsing is not necessary, and by not performing rinsing, the amount of solvent used can be reduced.

[0082] Example

[0083] The present invention will be specifically described below with examples of synthesis, embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0084] [1] Synthesis of high-valent bismuth

[0085] [Synthetic Example 1] Synthesis of high-valent bismuth compound B-1

[0086] [Chemistry 8]

[0087]

[0088] Bismuth(III) chloride (22.91 g, 72.66 mmol) was dispersed in 100 mL of THF under a nitrogen atmosphere. The dispersion was cooled to 0 °C, and 2.0 M 4-vinylphenyl magnesium bromide (109 mL, 218 mmol) was added dropwise, maintaining the temperature with stirring for 1 hour. The temperature was then raised, and the mixture was stirred under reflux for another 2 hours. After the reaction was complete, 200 mL of saturated ammonium chloride aqueous solution was added under ice bath conditions, and the mixture was extracted with toluene (500 mL). The organic layer was washed three times with ultrapure water (200 mL), and the solvent was distilled off. Purification was performed by silica gel column chromatography (developing solvent: hexane), yielding intermediate I-1 as white crystals (yield 24.83 g, 77.6%). The NMR spectrum of intermediate I-1 is shown below.

[0089] 1 H-NMR (500MHz, CDCl3, δin ppm): 7.70 (d, J = 8.0Hz, 6H), 7.41 (d, J = 8.0Hz, 6H), 6.68 (dd, J = 17.1and 11.4Hz, 3H), 5.75 (dd, J = 17.1and 1.1Hz,3H),5.23(dd,J=11.4and1.1Hz,3H)

[0090] Intermediate I-1 (7 g, 13.50 mmol) was dispersed in 70 g of dichloromethane, and DAIB (4.34 g, 13.50 mmol) was added. The mixture was stirred at room temperature for 12 hours. The solvent was then distilled off, and 100 mL of hexane was added. The mixture was stirred at room temperature for 1 hour, and the solid was filtered. The resulting solid was dried at 40 °C to obtain high-valent bismuth compound B-1 as white crystals (yield 4.82 g, 63.7%). The NMR spectrum and MS data of high-valent bismuth compound B-1 are shown below.

[0091] 1 H-NMR (500MHz, CDCl3, δin ppm): 8.18 (d, J=8.0Hz, 6H), 7.59 (d, J=8.0Hz, 6H), 6.71 (dd, J=17.7and 10.9Hz, 3H), 5.81 (dd, J=17.7and 0.9Hz,3H),5.32(dd,J=10.9and0.9Hz,3H),1.75(s,6H)

[0092] Single Quadrupole Mass Analysis (ESI): POSITIVE M + Na +659 (equivalent to C) 28 H 27 BiNaO4)

[0093] [Synthetic Example 2] Synthesis of high-valent bismuth compound B-2

[0094] [Chemistry 9]

[0095]

[0096] High-valent bismuth compound B-1 (0.6 g, 0.94 mmol) was dispersed in 5 g of HBM, and benzoic acid (0.23 g, 1.88 mmol) was added. The mixture was stirred at 60 °C for 12 hours. The solvent was then distilled off, and 30 mL of methanol was added. The mixture was stirred at room temperature for 1 hour, and the solid was filtered. The resulting solid was dried at 40 °C to obtain high-valent bismuth compound B-2 as white crystals (yield 0.48 g, 84.9%). The NMR spectrum and MS data of high-valent bismuth compound B-2 are shown below.

[0097] 1 H-NMR (500MHz, CDCl3, δin ppm): 8.24(d,J=8.2Hz,6H),8.02(m,4H),7.62(d,J=8.2Hz,6H),7.32(m,6H),6.66(dd,J=17.5and 10.5Hz,3H),5.74(dd,J=17.5and0.9Hz,3H),5.35(dd,J=10.5and 0.9Hz,3H)

[0098] Single Quadrupole Mass Analysis (ESI): POSITIVE M + Na + 783 (equivalent to C) 38 H 31 BiNaO4)

[0099] [Synthetic Example 3] Synthesis of high-valent bismuth compound B-3

[0100] By changing the starting materials, but otherwise using the same method as in Synthesis Examples 1 and 2, the high-valent bismuth compound B-3 shown below was synthesized.

[0101] [Chemistry 10]

[0102]

[0103] [2] Preparation of the resist composition

[0104] [Examples 1-1 to 1-6, Comparative Examples 1-1 to 1-5]

[0105] High-valent bismuth compounds were dissolved in solvents according to the compositions shown in Table 1 below, and the resulting solutions were filtered through a 0.2 μm Teflon (registered trademark) filter to obtain resist compositions (R-01 to R-06) and comparative resist compositions (CR-01 and CR-02). Furthermore, polymers, photoacid generators, sensitivity modifiers, solvents, and 0.01% by mass of surfactant (PF-636, manufactured by OMNOVA) were mixed according to the compositions shown in Table 2 below, and then filtered through a 0.2 μm Teflon (registered trademark) filter to obtain comparative resist compositions (CR-03 to CR-05).

[0106] [Table 1]

[0107]

[0108] [Table 2]

[0109]

[0110] In Tables 1 and 2, the organic solvents, high-valent bismuth compounds (O-1, O-2), basic polymers (P-1), photoacid generators (PAG-1, PAG-2), and sensitivity modifiers (Q-1, Q-2) are as follows.

[0111] Organic solvent: PGMEA (propylene glycol monomethyl ether acetate)

[0112] HBM (methyl 2-hydroxyisobutyrate)

[0113] GBL (γ-butyrolactone)

[0114] High-valence bismuth compounds: O-1, O-2

[0115] [Chemistry 11]

[0116]

[0117] Basic polymer: P-1

[0118] [Chemistry 12]

[0119]

[0120] Mw = 8755 (converted to polystyrene), Mw / Mn = 1.94

[0121] Photoacid generators: PAG-1, PAG-2

[0122] [Chemistry 13]

[0123]

[0124] Sensitivity modifiers: Q-1, Q-2

[0125] [Chemistry 14]

[0126]

[0127] [3] Evaluation of EUV lithography (line and space pattern, negative tone development)

[0128] [Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-5]

[0129] Each resist composition (R-01 to R-6, CR-01 to CR-05) was spin-coated onto a Si substrate with a 20 nm thick silicon-containing spin-coating hard mask SHB-A940 (43% by mass silicon) manufactured by Shin-Etsu Chemical Co., Ltd. The substrate was pre-baked (PAB) for 60 seconds at the temperatures listed in Table 3 using a heated plate to obtain a 40 nm thick resist film. Using an ASML EUV scanning exposure machine NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination), a 48 nm line-to-spacing (LS) 1:1 pattern was exposed. Then, a pre-baking (PEB) was performed on the heated plate at the temperatures listed in Table 3 for 60 seconds, followed by development with the developer listed in Table 3 for 30 seconds to form an LS pattern with a 24 nm wide spacing and a 48 nm pitch. The sensitivity, LWR, and limit resolution of the obtained LS pattern were evaluated using the methods described below. The results are shown in Table 3.

[0130] [Sensitivity Evaluation]

[0131] The aforementioned LS pattern was observed using a Hitachi Advanced Technology Co., Ltd. (HIT) CG-6300 measuring SEM, and the optimal exposure Eop (mJ / cm²) for obtaining an LS pattern with a spacing width of 24nm and a pitch of 48nm was determined. 2 ), and make it a sensitivity.

[0132] [LWR Evaluation]

[0133] For an LS pattern obtained by irradiation with the optimal exposure, the dimensions at 10 points along the longitudinal direction of the spacing width are measured using a Hitachi Advanced Technology Co., Ltd. 3x the standard deviation (σ) (3σ) is calculated from the results and set as LWR. The smaller this value, the smaller the roughness and the more uniform the spacing width of the pattern can be obtained.

[0134] [Limited Resolution Evaluation]

[0135] By gradually increasing the exposure amount slightly from the optimal exposure for forming the aforementioned LS pattern, the linewidth (nm) at the resolvable limit during pattern formation was determined using a Hitachi Advanced Technology (Group) Co., Ltd. (CG-6300) measuring SEM, and this value was set as the limiting resolution (nm). The smaller this value, the better the limiting resolution and the finer the pattern can be formed.

[0136] [Table 3]

[0137]

[0138] Developer: nBA (Butyl acetate)

[0139] As shown in Table 3, the resist composition of the present invention exhibits excellent sensitivity, LWR and resolution during negative tone development when forming LS patterns for EUV exposure.

[0140] [4] Evaluation of EUV lithography (contact hole pattern)

[0141] [Examples 3-1 to 3-6, Comparative Examples 3-1 to 3-5]

[0142] Each resist composition (R-01 to R-6, CR-01 to CR-05) was spin-coated onto a Si substrate with a silicon-containing spin-coating hard mask SHB-A940 (43% by mass) manufactured by Shin-Etsu Chemical Co., Ltd., with a film thickness of 20 nm. The resist film was pre-baked (PAB) for 60 seconds at the temperatures listed in Table 4 using a heated plate to obtain a 50 nm thick resist film. Then, the resist film was exposed using an ASML EUV scanning exposure machine NXE3400 (NA 0.33, σ 0.9 / 0.6, quadrupole illumination, mask with a pitch of 64 nm and a +20% offset hole pattern on the wafer). The resist film was then baked (PEB) for 60 seconds at the temperatures listed in Table 4 on a heated plate, followed by development for 30 seconds using the developer listed in Table 4 to obtain a contact hole (CH) pattern with a size of 32 nm. For the obtained CH pattern, the sensitivity, CDU, and limiting resolution were evaluated using the following method. The results are shown in Table 4.

[0143] [Sensitivity Evaluation]

[0144] For the aforementioned CH pattern, a Hitachi Advanced Technology Co., Ltd.-manufactured SEM (CG-6300) was used for observation to determine the optimal exposure Eop (mJ / cm²) for obtaining a hole pattern with a size of 32nm. 2 ).

[0145] [CDU Evaluation]

[0146] The dimensions of 50 CH patterns obtained by irradiation with the optimal exposure were measured, and the standard deviation (σ) obtained from the results was set as CDU as three times the value of 3σ. The smaller this value, the more uniform the aperture diameter of the pattern can be obtained.

[0147] [Limited Resolution Evaluation]

[0148] By gradually reducing the exposure amount from the optimal exposure for forming the aforementioned CH pattern, the aperture diameter (nm) that can be resolved during CH pattern formation is determined using a Hitachi Advanced Technology (Group) Co., Ltd. (CG-6300) measuring SEM, and this value is set as the limiting resolution (nm). The smaller this value, the better the limiting resolution, and the finer the aperture diameter pattern can be obtained.

[0149] [Table 4]

[0150]

[0151] Developer: IPA (isopropanol)

[0152] TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0153] As shown in Table 4, the resist composition of the present invention exhibits excellent sensitivity, CDU, and resolution in the formation of contact hole patterns by EUV exposure.

Claims

1. A high-valence bismuth compound, represented by the following formula (1); In the formula, R 1 and R 2 Each of the following groups is a hydrocarbon group consisting of 1 to 10 carbon atoms, which may be independently composed of halogen atoms or may also contain heteroatoms; furthermore, R 1 and R 2 They can also bond to each other and form rings together with the carbon atoms they are bonded to and the atoms between those carbon atoms; A 1 A 2 and A 3 Each is independently a hydrocarbon group with 2 to 20 carbon atoms containing a polymerizable functional group, and the hydrocarbon group may also contain heteroatoms; Ar 1 Ar 2 and Ar 3 Each is an arylene with 6 to 20 carbon atoms, and in this arylene, some or all of the hydrogen atoms on its aromatic ring may be replaced by halogen atoms or hydrocarbon groups with 1 to 20 carbon atoms that may contain heteroatoms.

2. The high-valent bismuth compound according to claim 1, wherein, A 1 A 2 and A 3 It can be acryloyloxy, methacryloyloxy, or may contain a cycloalkenyl group with 3 to 20 heteroatoms, a cycloalkenyloxy group with 3 to 20 heteroatoms, a cycloalkenylcarbonyloxy group with 3 to 20 heteroatoms, an alkenyl group with 2 to 20 heteroatoms, or an alkenyloxy group with 2 to 20 heteroatoms.

3. A resist composition comprising a high-valence bismuth compound according to claim 1 or 2 and a solvent.

4. The resist composition according to claim 3 further contains a free radical scavenger.

5. The resist composition according to claim 3 further comprises a surfactant.

6. A pattern forming method, comprising the following steps: A resist film is formed on a substrate using the resist composition according to claim 3. The resist film was exposed to high-energy rays, and The exposed resist film is developed using an organic solvent as the developer, which dissolves the unexposed areas and forms a negative pattern in which the exposed areas do not dissolve.

Images