Hypervalent bismuth compound, resist composition and patterning process

Abstract

To provide a non-chemically amplified resist composition excellent in sensitivity and resolution in photolithography using high energy rays, especially electron beam (EB) lithography and EUV lithography, and to provide a pattern forming method using the resist composition.SOLUTION: A hypervalent bismuth compound represented by formula (1) and a resist composition containing the hypervalent bismuth compound as a main component are provided. Wherein R1 and R2 each independently represent a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a hetero atom; A1, A2 and A3 each independently represent a hydrocarbyl group having 2 to 20 carbon atoms which contains a polymerizable functional group and may contain a hetero atom; Ar1, Ar2 and Ar3 each independently represent an arylene group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms on the aromatic ring may be substituted with a halogen atom or a hydrocarbyl group having 1 to 2 carbon atoms which may contain a hetero atom. ) SELECTED DRAWING: None

Description

[Technical Field]

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

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

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

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

[0005] One example of a material for non-chemically amplified resist compositions is polymethyl methacrylate (PMMA), which is used in positive resist compositions. PMMA is irradiated with EUV light and its main chain is cleaved, reducing its molecular weight, thereby improving its solubility in organic solvent developers.

[0006] Hydrogen silsesquioxane (HSQ) is a material for negative resist compositions 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 materials for negative resist compositions. These materials for negative resist compositions have small molecular sizes before crosslinking and are free of blurring due to acid diffusion, resulting in low edge roughness and extremely high resolution. They are therefore 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 bismuth atoms that have high absorption of EUV light. However, as mentioned above, chemically amplified resists cannot achieve excellent resolution performance in EUV lithography, where processing dimensions will become increasingly finer in the future.

[0009] Patent Document 2 proposes an organic solvent negative resist composition that uses 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. 2018005224 [Patent Document 2] Published Patent Publication No. 2021503482 [Non-patent literature]

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

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

[0013] As a result of extensive research into achieving the above-mentioned object, the present inventors discovered that a resist composition containing as its main component a hypervalent bismuth compound having an aryl group substituted with a polymerizable group 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 hypervalent bismuth compound represented by the following formula (1): [ka] (In the formula, 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. A 1 , A 2 and A 3 are each independently a hydrocarbyl group having 2 to 20 carbon atoms and containing a polymerizable functional group, and the hydrocarbyl group may contain a heteroatom. Ar 1 , Ar 2 and Ar 3 are each independently an arylene group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms on the aromatic ring of the arylene group may be substituted with a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 2.A 1 , A 2 and A 3 wherein the aryl group is an acryloyloxy group, a methacryloyloxy group, a cycloalkenyl group having 3 to 20 carbon atoms which may contain a heteroatom, a cycloalkenyloxy group having 3 to 20 carbon atoms which may contain a heteroatom, a cycloalkenylcarbonyloxy group having 3 to 20 carbon atoms which may contain a heteroatom, an alkenyl group having 2 to 20 carbon atoms which may contain a heteroatom, or an alkenyloxy group having 2 to 20 carbon atoms which may contain a heteroatom. 3. A resist composition comprising one or two hypervalent bismuth compounds and a solvent. 4. The resist composition of 3, further comprising a radical scavenger. 5. The resist composition of 3 or 4, further comprising a surfactant. 6. A pattern forming method comprising the steps of: forming a resist film on a substrate using the resist composition of any one of 3 to 5; exposing the resist film to high-energy rays; and developing the exposed resist film using an organic solvent as a developer to dissolve unexposed areas and form a negative pattern in which exposed areas do not dissolve. [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] [Hypervalent bismuth compounds] Hypervalent bismuth compounds are compounds with valence electrons that exceed the octet rule. Hypervalent bismuth compounds include pentacoordinate bismuth compounds with an oxidation state of +5.

[0017] The hypervalent bismuth compound of the present invention is a pentacoordinate hypervalent bismuth compound represented by the following formula (1). [ka]

[0018] In formula (1), R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms.

[0019] Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0020] The hydrocarbyl group 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 methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl, n-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 10 carbon atoms, such as a decyl group or an adamantyl group; alkenyl groups having 2 to 10 carbon atoms, such as a vinyl group or a 2-propenyl group; aryl groups having 6 to 10 carbon atoms, such as a phenyl group or a naphthyl group; and groups obtained by combining these. Furthermore, 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, etc. Among these, R 1 and R 2 is preferably a hydrocarbyl group having 1 to 4 carbon atoms.

[0021] In formula (1), A 1 , A 2 and A 3 are each independently a hydrocarbyl group having 2 to 20 carbon atoms and containing a polymerizable functional group, and the hydrocarbyl group may contain a heteroatom.

[0022] A 1 , A 2 and A 3 Preferred examples of the alkyl group include an acryloyloxy group, a methacryloyloxy group, a cycloalkenyl group having 3 to 20 carbon atoms which may contain a heteroatom, a cycloalkenyloxy group having 3 to 20 carbon atoms which may contain a heteroatom, a cycloalkenylcarbonyloxy group having 3 to 20 carbon atoms which may contain a heteroatom, an alkenyl group having 2 to 20 carbon atoms which may contain a heteroatom, and an alkenyloxy group having 2 to 20 carbon atoms which may contain a heteroatom.

[0023] A 1 , A 2 and A 3Specific examples of the group represented by the formula include, but are not limited to, the groups shown below. In the formula below, the dashed line indicates the group represented by Ar 1 , Ar 2 or Ar 3 Represents a bond with . [ka]

[0024] In formula (1), Ar 1 , Ar 2 and Ar 3 are each independently an arylene group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms on the aromatic ring of the arylene group may be substituted with a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. Examples of the arylene group include a phenylene group, a naphthylene group, and an anthracenediyl group. Ar 1 , Ar 2 and Ar 3 is preferably a phenylene group or a naphthylene group, more preferably a phenylene group, and even more preferably a 1,4-phenylene group.

[0025] Specific examples of the hypervalent bismuth compound represented by formula (1) include, but are not limited to, the following: [ka]

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] [Resist composition] The resist composition of the present invention contains the above-mentioned hypervalent bismuth compound as a main component.

[0030] The resist composition of the present invention further contains an organic solvent. The organic solvent is not particularly limited as long as it can dissolve the hypervalent bismuth compound and form a film. Specific examples of the organic solvent 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; and propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, and propylene glycol monomethyl ether. Examples of suitable solvents include ethers such as diethyl 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.

[0031] The content of the organic solvent is preferably 200 to 10,000 parts by mass per 100 parts by mass of the total solid content in the resist composition. In the present invention, the solid content is a general term for all components of the resist composition other than the solvent. The organic solvents may be used alone or in combination of two or more.

[0032] The resist composition of the present invention may further contain a radical scavenger as an additional component. By including a radical scavenger, it is possible to control the photoreaction during photolithography and adjust the sensitivity.

[0033] Examples of such radical scavengers include hindered phenols, quinones, hindered amines, and thiol compounds. Specific examples of hindered phenols include dibutylhydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Examples of quinones include 4-methoxyphenol (methoquinone) 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 radical scavengers, the content thereof is preferably 0.01 to 10% by mass of the total solid content. The radical scavengers may be used alone or in combination of two or more.

[0034] The resist composition of the present invention may contain a surfactant as another component. Examples of the surfactant include FC-4432 and FC-4430 (manufactured by 3M), and PF-636, PF-656, PF-6320, and PF-6520 (manufactured by Omnova). When the resist composition of the present invention contains a surfactant, the content thereof is preferably 0.001 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the hypervalent bismuth compound. The surfactant may be used alone or in combination of two or more types.

[0035] As described above, the resist composition of the present invention is a molecular resist composition that contains a hypervalent bismuth compound as a main component and does not contain a polymer with an acid-labile group (base polymer) or a photoacid generator, as contained in conventional chemically amplified resist compositions. The term "base polymer" refers to the polymer contained in the resist composition that is the component (main component) with the highest content other than the solvent. In resist compositions containing a base polymer, the base polymer is a polymer whose solubility in a developer changes due to the action of an acid generated from a photoacid generator. However, despite not containing the base polymer, the resist composition of the present invention exhibits a change in solubility in a developer between unexposed and exposed areas, particularly upon exposure to EB and EUV, enabling the formation of a pattern. The mechanism behind this change is not completely clear, but the following phenomenon can be hypothesized.

[0036] The hypervalent bismuth compound used in the present invention is a pentacoordinate compound in which an aryl group and two carboxylate ligands are bonded to the bismuth atom, as represented by formula (1). When exposed to EUV, the carboxyl groups of such pentacoordinate bismuth compounds undergo radical dissociation, and the resulting carboxylate radicals cause radical polymerization of the polymerizable groups on the aryl groups, resulting in a high molecular weight and the formation of a strong resist film.

[0037] The resist film thus formed on the substrate undergoes a change in polarity as the hypervalent bismuth compound, which is the main component of the resist film, is decomposed by light, and a negative pattern is formed by a development step.

[0038] In light of the above speculation, the resist composition of the present invention can be said to be a non-chemically amplified resist composition. Therefore, the image blurring caused by acid diffusion, which is observed in conventional chemically amplified resist compositions (compositions containing a base polymer and a photoacid generator), does not occur, and by using the resist composition of the present invention, fine patterns can be resolved.

[0039] The resist composition of the present invention is particularly effective in EUV lithography. This is due to the presence of bismuth atoms, which have a high absorption capacity for EUV light. This means that shot noise is reduced, and higher resolution and lower LWR can be achieved.

[0040] Recent examples of EUV resist compositions capable of forming fine patterns include metal resists whose main component is a metal tin compound, which has high EUV light absorption capacity similar to that of bismuth atoms (see, for example, Patent Document 2). However, such metal resists have problems such as insufficient solubility in coating solvents and storage stability. On the other hand, the resist composition of the present invention has excellent solvent solubility. Furthermore, the resist composition of the present invention can be used in negative tones, and therefore has a wide range of uses.

[0041] [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 pattern formation method can include the steps of forming a resist film on a substrate using the resist composition, exposing the resist film to high-energy rays, and developing the exposed resist film using an organic solvent as a developer to dissolve unexposed areas and form a negative pattern in which exposed areas are not dissolved.

[0042] First, the resist composition of the present invention is applied to a substrate for integrated circuit production (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating, etc.) or a substrate for mask circuit production (Cr, CrO, CrON, MoSi2, SiO2, etc.) by an appropriate coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, doctor coating, etc., to a coating thickness of 0.01 to 2 μm. This is then pre-baked on a hot plate preferably at 60 to 200°C for 10 seconds to 30 minutes, more preferably at 80 to 180°C for 30 seconds to 20 minutes, to form a resist film.

[0043] Next, the resist film is exposed to high-energy radiation. Examples of the high-energy radiation include ultraviolet radiation, far ultraviolet radiation, EB, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation. When ultraviolet radiation, far ultraviolet radiation, EUV, X-rays, soft X-rays, excimer laser light, gamma 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.

[0044] The resist composition of the present invention is optionally subjected to post-exposure baking (PEB), which is preferably performed 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.

[0045] After exposure or PEB, the film is developed using an organic solvent as a developer to dissolve the unexposed areas and form a negative pattern in which the exposed areas do not dissolve. Examples of developers that can be used at this time include 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, ethyl propionate, and ethyl 3-ethoxypropionate. Examples of the developer include methyl lactate, 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. These developers may be used alone or in combination of two or more.

[0046] 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. Water may also be used as a rinsing solution instead of an organic solvent.

[0047] 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]

[0048] 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.

[0049] [1] Synthesis of hypervalent bismuth [Synthesis Example 1] Synthesis of hypervalent bismuth compound B-1 [ka]

[0050] Bismuth(III) chloride (22.91 g, 72.66 mmol) was dispersed in 100 mL of THF under a nitrogen atmosphere. This dispersion was cooled to 0 °C, and 2.0 M 4-vinylphenylmagnesium bromide (109 mL, 218 mmol) was added dropwise. The mixture was stirred for 1 hour while maintaining the temperature. The temperature was then raised and the mixture was stirred for an additional 2 hours under reflux. After the reaction was completed, 200 mL of saturated aqueous ammonium chloride was added in an ice bath, 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. Intermediate I-1 was obtained as white crystals by silica gel column chromatography (eluent: hexane) (yield: 24.83 g, 77.6%). The nuclear magnetic resonance spectrum of Intermediate I-1 is shown below. 1 H-NMR (500 MHz, CDCl3, δ in ppm); 7.70 (d, J=8.0Hz, 6H), 7.41 (d, J=8.0Hz, 6H), 6.68 (dd, J=17.1 and 11.4Hz, 3H), 5.75 (dd, J=17.1 and 1.1Hz, 3H), 5.23 (dd, J=11.4 and 1.1Hz, 3H)

[0051] Intermediate I-1 (7 g, 13.50 mmol) was dispersed in 70 g of methylene chloride, 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 off. The resulting solid was dried at 40 °C to obtain hypervalent bismuth compound B-1 as white crystals (yield: 4.82 g, 63.7%). The nuclear magnetic resonance spectrum and MS data of hypervalent bismuth compound B-1 are shown below. 1 H-NMR (500 MHz, CDCl3, δ in ppm); 8.18 (d, J=8.0Hz, 6H), 7.59 (d, J=8.0Hz, 6H), 6.71 (dd, J=17.7 and 10.9Hz, 3H), 5.81 (dd, J=17.7 and 0.9Hz, 3H), 5.32 (dd, J=10.9 and 0.9 Hz, 3H), 1.75 (s,6H) Single quadrupole mass spectrometry (ESI): POSITIVE M + Na + 659 (C 28 H 27 BiNaO4 equivalent)

[0052] [Synthesis Example 2] Synthesis of hypervalent bismuth compound B-2 [ka]

[0053] Hypervalent 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 off. The resulting solid was dried at 40°C to obtain hypervalent bismuth compound B-2 as white crystals (yield: 0.48 g, 84.9%). The nuclear magnetic resonance spectrum and MS data of hypervalent bismuth compound B-2 are shown below. 1H-NMR (500 MHz, CDCl3, δ in 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=17.5 and 10.5Hz, 3H), 5.74 (dd, J=17.5 and 0.9Hz, 3H), 5.35 (dd, J=10.5 and 0.9Hz, 3H) Single quadrupole mass spectrometry (ESI): POSITIVE M + Na + 783(C 38 H 31 BiNaO4 equivalent)

[0054] [Synthesis Example 3] Synthesis of hypervalent bismuth compound B-3 The following hypervalent bismuth element compound B-3 was synthesized in the same manner as in Synthesis Examples 1 and 2, except that the starting material was changed. [ka]

[0055] [2] Preparation of resist composition [Examples 1-1 to 1-6, Comparative Examples 1-1 to 1-5] Resist compositions (R-01 to R-06) and comparative resist compositions (CR-01, CR-02) were prepared by dissolving a hypervalent bismuth compound in a solvent according to the composition shown in Table 1 below and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter. Comparative resist compositions (CR-03 to CR-05) 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 composition shown in Table 2 below, and then filtering the mixture through a 0.2 μm Teflon (registered trademark) filter.

[0056] [Table 1]

[0057] [Table 2]

[0058] In Tables 1 and 2, the organic solvents, hypervalent bismuth compounds (O-1, O-2), base polymers (P-1), photoacid generators (PAG-1, PAG-2) and sensitivity adjusters (Q-1, Q-2) are as follows:

[0059] Organic solvent: PGMEA (propylene glycol monomethyl ether acetate) HBM (2-hydroxyisobutyric acid methyl ester) GBL (γ-butyrolactone)

[0060] Hypervalent bismuth compounds: O-1, O-2 [ka]

[0061] Base polymer: P-1 [ka] Mw=8755 (polystyrene equivalent), Mw / Mn=1.94

[0062] Photoacid generator: PAG-1, PAG-2 [ka]

[0063] Sensitivity adjuster: Q-1, Q-2 [ka]

[0064] [3] EUV lithography evaluation (line and space pattern, negative tone development) [Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-5] Each resist composition (R-01 to R-6, CR-01 to CR-05) was spin-coated onto a Si substrate coated with a 20 nm-thick silicon-containing spin-on hard mask (SHB-A940, manufactured by Shin-Etsu Chemical Co., Ltd.) (43% silicon by mass). The resist was then pre-baked (PAB) on a hot plate for 60 seconds at the temperature listed in Table 3 to produce a 40 nm-thick resist film. A 48 nm line-and-space (LS) 1:1 pattern was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination), followed by a 60-second PEB on a hot plate at the temperature listed in Table 3. Development was then performed for 30 seconds using the developer listed in Table 3 to form a 24 nm space-width, 48 nm pitch LS pattern. The resulting LS patterns were evaluated for sensitivity, LWR, and limiting resolution according to the following methods. The results are shown in Table 3.

[0065] [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.

[0066] [LWR rating] The LS pattern obtained by irradiating with the optimum exposure dose was measured at 10 points in the longitudinal direction of the space width using a Hitachi High-Technologies Corporation critical dimension SEM (CG-6300), and the LWR 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.

[0067] [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.

[0068] [Table 3]

[0069] Developer: nBA (butyl acetate)

[0070] The results shown in Table 3 demonstrate that the resist composition of the present invention is excellent in sensitivity, LWR, and resolution even in negative tone development when forming an LS pattern by EUV exposure.

[0071] [4] EUV lithography evaluation (contact hole pattern) [Examples 3-1 to 3-6, Comparative Examples 3-1 to 3-5] Each resist composition (R-01 to R-6, CR-01 to CR-05) 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 pre-baked (PAB) for 60 seconds at the temperature listed in Table 6 to produce a 50 nm thick resist film. The resist film was then exposed to light using an ASML NXE3400 EUV scanner (NA 0.33, σ 0.9 / 0.6, quadruple-pole illumination, wafer-mounted 64 nm pitch, +20% bias hole pattern mask), baked (PEB) for 60 seconds at the temperature listed in Table 6, and developed for 30 seconds using the developer listed in Table 6 to obtain a 32 nm contact hole (CH) pattern. The resulting CH patterns were evaluated for sensitivity, LWR, and limiting resolution according to the following methods. The results are shown in Table 4.

[0072] [Sensitivity evaluation] The CH 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 sought.

[0073] [CDU Rating] The dimensions of 50 CH patterns obtained by irradiation with the optimal exposure dose were measured, and the CDU was calculated as three times the standard deviation (σ). The smaller this value, the more uniform the hole diameter pattern obtained.

[0074] [Limiting resolution evaluation] The limiting hole diameter (nm) that can be resolved when forming a CH pattern by gradually decreasing the exposure dose from the optimum exposure dose at which the CH 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 pattern with a finer hole diameter can be formed.

[0075] [Table 4]

[0076] Developer: IPA (isopropyl alcohol) TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0077] The results shown in Table 4 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 hypervalent bismuth compound represented by the following formula (1): 【Chemistry 1】 (In the formula, 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. A 1 , A 2 and A 3 are each independently a hydrocarbyl group having 2 to 20 carbon atoms and containing a polymerizable functional group, and the hydrocarbyl group may contain a heteroatom. Ar 1 , Ar 2 and Ar 3 are each independently an arylene group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms on the aromatic ring of the arylene group may be substituted with a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

2. A 1 , A 2 and A 3 is an acryloyloxy group, a methacryloyloxy group, a cycloalkenyl group having 3 to 20 carbon atoms which may contain a heteroatom, a cycloalkenyloxy group having 3 to 20 carbon atoms which may contain a heteroatom, a cycloalkenylcarbonyloxy group having 3 to 20 carbon atoms which may contain a heteroatom, an alkenyl group having 2 to 20 carbon atoms which may contain a heteroatom, or an alkenyloxy group having 2 to 20 carbon atoms which may contain a heteroatom.

3. 3. A resist composition comprising the hypervalent bismuth compound according to claim 1 or 2 and a solvent.

4. 4. The resist composition according to claim 3, further comprising a radical scavenger.

5. 4. The resist composition according to claim 3, further comprising a surfactant.

6. 4. A pattern forming method comprising the steps of: forming a resist film on a substrate using the resist composition according to claim 3; exposing the resist film to high-energy rays; and developing the exposed resist film using an organic solvent as a developer to dissolve unexposed areas and form a negative pattern in which exposed areas are insoluble.

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