Hypervalent bismuth compound, resist composition and pattern forming process

Abstract

The objective of this invention is to provide a non-chemically amplifying resist composition with excellent sensitivity and resolution in photolithography using high-energy rays, particularly electron beam (EB) lithography and EUV lithography, and a pattern forming method using the resist composition. The solution to this objective is a superatomic bismuth compound, represented by formula (1).

Description

[Technical Field]

[0001] This invention relates to a superatomic bismuth compound, a resistive composition, and a method for forming a pattern. [Previous Technology]

[0002] With the expansion of the IoT market, there is a growing demand for highly integrated, high-speed, and low-power LSIs, and the miniaturization of patterning is also progressing rapidly. In particular, logic devices are leading the way in miniaturization. As for the most advanced miniaturization technology, mass production of 10nm node devices using ArF immersion lithography with dual, triple, and quadruple patterning is already underway. In addition, research is progressing on the next generation of 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 Document 1). In order 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 claimed important, but also the control of acid diffusion is important (Non-Patent Document 2). However, chemical amplification inhibitors improve sensitivity and contrast through acid diffusion. Therefore, if acid diffusion is suppressed to the limit by lowering the post-exposure baking (PEB) temperature or shortening the PEB time, the sensitivity and contrast will be significantly reduced.

[0004] Adding an acid-generating agent that produces a bulky acid is effective in suppressing acid diffusion. Therefore, it has been proposed to use an acid-generating agent derived from the onium salt of a polymerizable olefin in polymer copolymerization. However, considering acid diffusion, in the patterning of resist films with a processing size of 16 nm or less, 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 amplifying inhibitor compositions include polymethyl methacrylate (PMMA). PMMA is a positive inhibitor composition material used to improve the solubility of developer solutions in organic solvents by breaking down the main chain and reducing the molecular weight through EUV irradiation.

[0006] Hydrosilsesquioxane (HSQ) is a cross-linked material formed by the condensation reaction of silanol produced by EUV irradiation, and is used as a negative resist component that is insoluble in alkaline developer. Additionally, chlorinated calixarnes also function as negative resist components. These negative resist components are suitable as pattern transfer materials with low edge roughness and very high resolution, exhibiting the resolving limits of exposure equipment, due to their small molecular size before cross-linking and the absence of blurring caused by acid diffusion. However, these materials have insufficient sensitivity and require further improvement.

[0007] One of the main reasons for the difficulty in developing materials for EUV lithography applications is the low number of photons in EUV exposure. EUV energy is much higher than ArF excimer laser light, and the number of photons in EUV exposure is only one-fourteenth that of ArF exposure. Furthermore, the size of the pattern formed by EUV exposure is less than half that of ArF exposure. Therefore, EUV exposure is easily affected by variations in the number of photons. Variations in the number of photons in extremely short wavelength emission regions constitute shot noise, a physical phenomenon that cannot be eliminated. Therefore, the so-called stochastics theory has attracted attention. While the effect of shot noise cannot be eliminated, we will discuss how to reduce it. Due to the effect of shot noise, not only will dimensional uniformity (CDU) and linewidth roughness (LWR) increase, but there is also a one in several million chance of observing hole blockage. Hole blockage leads to poor conductivity and transistor malfunction, thus adversely affecting the overall performance of the device. When considering practical sensitivity, resistive 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 influence of shot noise from the perspective of resistors, the introduction of elements with high absorption of EUV light has attracted attention. Patent Document 1 proposes a chemical amplification resist composition containing bismuth atoms with high absorption of EUV light. However, as mentioned above, chemical amplification resists cannot achieve excellent resolution in EUV lithography with increasingly smaller processing dimensions in the future.

[0009] Patent Document 2 claims the use of an organic solvent-based negative resist composition containing tin compounds. This is because tin, which has high absorption of 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, including insufficient solubility in the resist solvent, insufficient storage stability due to excessive reactivity, and defects caused by etching residue. [Prior Art Documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2018005224 [Patent Document 2] Japanese Patent Publication No. 2021503482 [Non-Patent Document]

[0011] [Non-Patent Literature 1] SPIE Vol. 5039 p1 (2003) [Non-Patent Literature 2] SPIE Vol. 6520 p65203L-1 (2007) [Summary of the Invention]

[0012] [Problem to be Solved by the Invention] The present invention has been made in view of the foregoing circumstances, and its object is to provide a non-chemically amplifying resist composition with excellent sensitivity and resolution in photolithography using high-energy rays, particularly in electron beam (EB) lithography and EUV lithography, and to provide a pattern forming method using the resist composition. [Means for Solving the Problem]

[0013] As a result of repeated and in-depth explorations by the inventors in order to achieve the aforementioned objectives, the following insights were obtained, and the present invention was thus completed: a resist composition with a superatomic bismuth compound having an aryl group substituted with a polymerizable group as the main component can provide a resist film with extremely high sensitivity and excellent resolution, which is extremely effective in precision microfabrication.

[0014] That is, the present invention provides the following inhibitor composition and pattern formation method. 1. A superatomic bismuth compound, represented by the following formula (1). [Chemical 1] In the formula, R1 and R2 are independently halogen atoms or hydrocarbon groups with 1 to 10 carbon atoms that may also contain heteroatoms. Furthermore, R1 and R2 may also be bonded to each other and form a ring together with the carbon atoms they are bonded to and the atoms between the carbon atoms. A1, A2 and A3 are independently hydrocarbon groups with 2 to 20 carbon atoms that contain polymerizable functional groups, and the hydrocarbon groups may also contain heteroatoms. Ar1, Ar2 and Ar3 are independently aryl groups with 6 to 20 carbon atoms, and in the aryl group, part 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 also contain heteroatoms. 2. A supraatomic bismuth compound as described in 1, wherein A1, A2, and A3 are acryloxy, methacryloxy, 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. 3. An inhibitor composition comprising a supraatomic bismuth compound as described in 1 or 2 and a solvent. 4. An inhibitor composition as described in 3, further comprising a free radical scavenger. 5. An inhibitor composition as described in 3 or 4, further comprising a surfactant. 6. A pattern forming method comprising the following steps: forming a resist film on a substrate using a resist composition as described in any one of 3. to 5; exposing the resist film to high-energy radiation; and developing the exposed resist film using an organic solvent as a developer to dissolve the unexposed areas, thereby forming a negative pattern in which the exposed areas are insoluble. [Effects of the Invention]

[0015] The resist composition of the present invention is particularly useful in EB lithography and EUV lithography, which has both high sensitivity and high resolution and is used to form fine patterns.

Implementation Method

[0016] [Superatomic Bismuth Compounds] Superatomic bismuth compounds are a general term for bismuth compounds that have valence electrons that exceed the octet rule in form. Examples of superatomic bismuth compounds include pentacoordinate bismuth compounds with an oxidation state of +5.

[0017] The superatomic bismuth compound of the present invention is a five-coordinate superatomic bismuth compound represented by the following formula (1). [Chemical 2]

[0018] In formula (1), R1 and R2 are halogen atoms or hydrocarbon groups with 1 to 10 carbon atoms that may contain heteroatoms. Furthermore, R1 and R2 may also bond to each other and form a ring together with the carbon atoms they are bonded to and the atoms between those carbon atoms.

[0019] Specific examples of the aforementioned halogen atoms include: fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.

[0020] The aforementioned hydrocarbon group can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include: alkyl groups with 1 to 10 carbon atoms such as methyl, ethyl, propyl, isopropyl, n-butyl, secondary butyl, tertiary butyl, tertiary pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbon groups with 3 to 10 carbon atoms such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norcamphenyl, tricyclo[5.2.1.02,6]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 them. Furthermore, some or all of the hydrogen atoms in the aforementioned hydrocarbon group can be replaced by a group containing heteroatoms such as oxygen, sulfur, nitrogen, or halogen atoms, and a portion of the -CH2- group in the aforementioned hydrocarbon group can also be replaced by a group containing heteroatoms such as oxygen, sulfur, or nitrogen atoms. This can result in the presence of hydroxyl, cyano, halogen, carbonyl, ether, thioether, ester, sulfonate, carbonate, carbamate, lactone, sulfonate, or carboxylic anhydride groups. Among these, R1 and R2 are preferably hydrocarbon groups with 1 to 4 carbon atoms.

[0021] In formula (1), A1, A2 and A3 are each a hydrocarbon group with 2 to 20 carbon atoms containing polymerizable functional groups, and the hydrocarbon group may also contain heteroatoms.

[0022] A1, A2 and A3 are preferably acryloxy, methacryloxy, 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.

[0023] Specific examples of the bases represented by A1, A2, and A3 can be listed below, but are not limited to these. Additionally, in the following formula, dashed lines represent atomic bonds with Ar1, Ar2, or Ar3. [Chemistry 3]

[0024] In formula (1), Ar1, Ar2, and Ar3 are each independently an aryl group with 6 to 20 carbon atoms, and in this aryl group, part or all of the hydrogen atoms on the aromatic ring may be replaced by halogen atoms or hydrocarbon groups with 1 to 20 carbon atoms containing heteroatoms. Examples of the aforementioned aryl groups include: phenyl, naphthyl, anthracenediyl, etc. Ar1, Ar2, and Ar3 are preferably phenyl or naphthyl, phenyl is more preferred, and 1,4-phenyl is even more preferred.

[0025] Specific examples of bismuth compounds with superatomic valences represented by formula (1) are shown below, but are not limited thereto. [Chemistry 4]

[0026] [Chemical 5]

[0027] [Chemical 6]

[0028] [Chemical 7]

[0029] [Inhibitor Composition] The inhibitor composition of the present invention contains the aforementioned superatomic bismuth compound as the main component.

[0030] The inhibitor composition of the present invention further contains an organic solvent. There are no particular limitations on the aforementioned organic solvent, provided it can dissolve the aforementioned superatomic bismuth compound and form a film. Specific examples of the aforementioned organic solvent 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; and propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol monoethyl ether. Ethers such as propylene glycol dimethyl ether and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tributyl acetate, tributyl 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.

[0031] The content of the aforementioned organic solvent is preferably 200 to 10,000 parts by mass relative to 100 parts by mass of all solid components in the inhibitor composition. Furthermore, in this invention, "solid components" refers to all components of the inhibitor composition except for the solvent. The aforementioned organic solvent may be used alone or in combination with two or more other solvents.

[0032] The inhibitor composition of the present invention may also contain free radical scavengers as other components. By containing free radical scavengers, the light reaction in photolithography can be controlled, and the sensitivity can be adjusted.

[0033] 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 inhibitor 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.

[0034] The inhibitor 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), etc. When the inhibitor composition of the present invention contains surfactants, their content relative to 100 parts by mass of the aforementioned superatomic bismuth compound is preferably 0.001 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass. The aforementioned surfactants may be used alone or in combination of two or more.

[0035] The resist composition of the present invention uses a superatomic bismuth compound as the main component as described above, and does not contain polymers (base polymers) with acid-dependent unstable groups, or molecular resist compositions containing photoacid generators, as found in conventional chemical amplification resist compositions. 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, especially EB and EUV, and form patterns. The mechanism is not fully elucidated, but phenomena such as the following can be speculated.

[0036] The superatomic 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 will undergo radical dissociation due to EUV exposure, and the polymerizable group on the aryl group will undergo radical polymerization due to the generated carboxylic acid ester free radicals, thereby increasing the molecular weight and forming a robust resist film.

[0037] In the resist film formed on the substrate in this manner, the superatomic bismuth compound, which is the main component of the resist film, will decompose due to light, thereby changing its polarity, and a negative pattern will be formed by using the development step.

[0038] In view of the foregoing speculation, the inhibitor composition of the present invention can be considered a non-chemically amplified inhibitor composition. Therefore, the blurring of the image due to acid diffusion that can be observed in conventional chemically amplified inhibitor compositions (compositions containing a base polymer and a photoacid generator) will not occur, and fine patterns can be resolved by using the inhibitor composition of the present invention.

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

[0040] In recent years, EUV resist compositions capable of forming fine patterns have been developed, including metal resists with tin compounds, which, like bismuth atoms, have high EUV light absorption capacity as the main component (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.

[0041] [Pattern Forming Method] When the resist composition of the present invention is used in the manufacture of various integrated circuits, known lithography techniques can be used. For example, a pattern forming method may include the following steps: 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 dissolve and the exposed areas do not dissolve.

[0042] 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.) with a film thickness of 0.01~2μm using appropriate coating methods such as spin coating, roll coating, flow coating, dip coating, spray coating, or blade coating. The substrate is then pre-baked on a hot plate at a temperature preferably 60~200°C for 10 seconds to 30 minutes, and more preferably 80~180°C for 30 seconds to 20 minutes to form a resist film.

[0043] Then, the aforementioned resist film is exposed using high-energy rays. Examples of such high-energy rays include: ultraviolet light, far-ultraviolet light, EB, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, synchrotron radiation, etc. When using ultraviolet light, far-ultraviolet light, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, synchrotron radiation, etc., irradiation is performed directly or using a mask to form the desired pattern, with an exposure dose preferably of about 1 to 300 mJ / cm², and more preferably about 10 to 200 mJ / cm². When using EB, high-energy rays are applied directly or using a mask to form the desired pattern, with an exposure dose preferably of about 0.1 to 5000 μC / cm², and more preferably about 0.5 to 4000 μC / cm². Furthermore, the resist composition of the present invention is particularly suitable for fine patterning using EB or EUV, especially in high-energy rays.

[0044] The inhibitor composition of the present invention needs to be baked after exposure (PEB). At this time, after exposure, it is preferably carried out on a heated plate or in an oven at 30~120°C for 10 seconds to 30 minutes, and more preferably at 60~100°C for 30 seconds to 20 minutes.

[0045] After exposure or PEB, an organic solvent is used as a developer to form a negative pattern that dissolves the unexposed areas but does not dissolve 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.

[0046] After development, rinsing should be performed as needed. The rinsing solution should preferably be a solvent that is miscible with the developer and does not dissolve the resist film. Ideally, solvents such as 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 can be used. Alternatively, water can be used instead of organic solvents as the rinsing solution.

[0047] By performing rinsing, the collapse of the resist pattern and the occurrence of defects can be reduced. Furthermore, rinsing is not necessary; by not performing rinsing, the amount of solvent used can be reduced. [Example]

[0048] Hereinafter, the present invention will be specifically described by way of example synthesis, example embodiment and comparative example, but the present invention is not limited to the following examples.

[0049] [1] Synthesis of superatomic bismuth [Synthetic Example 1] Synthesis of superatomic bismuth compound B-1 [Chemical 8]

[0050] Bismuth(III) chloride (22.91 g, 72.66 mmol) was dispersed in 100 mL of THF under 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 and 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 silicone column chromatography (developing solvent: hexane), thereby obtaining intermediate I-1 as white crystals (yield 24.83 g, 77.6%). The NMR spectrum of intermediate I-1 is shown below. 1H-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 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 supraatomic bismuth compound B-1 (yield 4.82 g, 63.7%) as white crystals. The NMR spectrum and MS data of supraatomic bismuth compound B-1 are shown below. ¹H-NMR (500 MHz, CDCl₃, δ in ppm): 8.18 (d, J=8.0 Hz, 6H), 7.59 (d, J=8.0 Hz, 6H), 6.71 (dd, J=17.7 and 10.9 Hz, 3H), 5.81 (dd, J=17.7 and 0.9 Hz, 3H), 5.32 (dd, J=10.9 and 0.9 Hz, 3H), 1.75 (s, 6H) Single quadruple electrode mass analysis (ESI): POSITIVE M+Na+ 659 (equivalent to C₂₈H₂₇BiNaO₄)

[0052] [Synthetic Example 2] Synthesis of the superatomic bismuth compound B-2 [Chemistry 9]

[0053] 0.6 g (0.94 mmol) of supraatomic bismuth compound B-1 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 supraatomic bismuth compound B-2 (yield 0.48 g, 84.9%) as white crystals. The NMR spectrum and MS data of supraatomic 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 quadruple electrode mass analysis (ESI): POSITIVE M+Na+ 783 (equivalent to C₃₈H₃₁BiNaO₄)

[0054] [Synthesis Example 3] Synthesis of the superatomic bismuth compound B-3: The starting materials were changed, but otherwise the same method as in Synthesis Examples 1 and 2 was used to synthesize the superatomic bismuth compound B-3 as shown below. [Chemical 10]

[0055] [2] Preparation of inhibitor compositions [Examples 1-1 to 1-6, Comparative Examples 1-1 to 1-5] The superatomic bismuth compound was dissolved in a solvent according to the composition shown in Table 1 below, and the resulting solution was filtered through a 0.2 μm Teflon (registered trademark) filter to obtain inhibitor compositions (R-01 to R-06) and comparative inhibitor compositions (CR-01, CR-02). Furthermore, the polymer, photoacid generator, sensitivity modifier, solvent and 0.01% by mass of surfactant (PF-636, manufactured by OMNOVA) were mixed according to the composition shown in Table 2 below, and then filtered through a 0.2 μm Teflon (registered trademark) filter to obtain comparative inhibitor compositions (CR-03 to CR-05).

[0056] [Table 1] inhibitor Composition Superatomic bismuth compounds (parts by weight) Solvent 1 (parts by weight) Solvent 2 (parts by weight) Example 1-1 R-01 B-1 (14.0) PGMEA(900) GBL(100) Examples 1-2 R-02 B-1 (14.0) HBM(1000) - Examples 1-3 R-03 B-2 (15.4) PGMEA(900) GBL(100) Examples 1-4 R-04 B-2 (15.4) HBM(1000) - Examples 1-5 R-05 B-3 (14.0) PGMEA(900) GBL(101) Examples 1-6 R-06 B-3 (14.0) HBM(1000) - Comparative Example 1-1 CR-01 O-1(14.0) HBM(1000) - Comparative Examples 1-2 CR-02 O-2 (14.0) HBM(1000) -

[0057] [Table 2] inhibitor Composition Basic polymers (parts by weight) Photoacid generator (parts by weight) Sensitivity modifier (parts by weight) Solvent 1 (parts by weight) Solvent 2 (parts by weight) Comparative Examples 1-3 CR-03 P-1(80) PAG-1(19.0) Q-1(6.2) PGMEA (1890) GBL(210) Comparative Examples 1-4 CR-04 P-1(80) PAG-2(21.0) Q-1(6.2) PGMEA (1890) GBL(210) Comparative Examples 1-5 CR-05 P-1(80) PAG-1(19.0) Q-2(2.6) PGMEA (1890) GBL(210)

[0058] In Tables 1 and 2, the organic solvent, the superatomic bismuth compound (O-1, O-2), the base polymer (P-1), the photoacid generator (PAG-1, PAG-2) and the sensitivity modifier (Q-1, Q-2) are as follows.

[0059] Organic solvents: PGMEA (propylene glycol monomethyl ether acetate), HBM (methyl 2-hydroxyisobutyrate), GBL (γ-butyrolactone)

[0060] Bismuth compounds with superatomic valences: O-1, O-2 [Chemical 11]

[0061] Basic polymer: P-1 [Chemical 12] Mw=8755 (converted to polystyrene), Mw / Mn=1.94

[0062] Photoacid generating agents: PAG-1, PAG-2 [Chemical 13]

[0063] Sensitivity modifiers: Q-1, Q-2 [Chemical 14]

[0064] [3] EUV lithography evaluation (line and space pattern, negative tone development) [Examples 2-1~2-6, Comparative Examples 2-1~2-5] Each resist composition (R-01~R-6, CR-01~CR-05) was spin-coated onto a Si substrate with a film thickness of 20 nm, which was formed with a silicon-containing spin-coated hard mask SHB-A940 (silicon content of 43% by mass) manufactured by Shin-Etsu Chemical Industry Co., Ltd. Using a heating plate, the film was pre-baked (PAB) at the temperature recorded in Table 3 for 60 seconds to obtain a resist film with a film thickness of 40 nm. Using an ASML NXE3400 EUV scanning exposure machine (NA 0.33, σ 0.9, 90-degree dipole illumination), a 48nm line-to-spacing (LS) 1:1 pattern was exposed. After exposure, the pattern was baked (PEB) on a heated plate at the temperatures described in Table 3 for 60 seconds, followed by development with the developer described in Table 3 for 30 seconds, forming an LS pattern with a spacing of 24nm and a pitch of 48nm. The sensitivity, LWR, and limiting resolution of the obtained LS pattern were evaluated using the methods described below. The results are shown in Table 3.

[0065] [Sensitivity Evaluation] The aforementioned LS pattern was observed using a Hitachi Advanced Technology (Group) Co., Ltd. measuring SEM (CG-6300). The optimal exposure Eop (mJ / cm2) for obtaining an LS pattern with a spacing width of 24nm and a pitch of 48nm was determined and set as the sensitivity.

[0066] [LWR Evaluation] For an LS pattern obtained by irradiation with the optimal exposure, the dimensions at 10 points along the longitudinal direction of the spacing width were measured using a Hitachi Advanced Technology Co., Ltd. 3x the standard deviation (σ) (3σ) was calculated from the results and set as LWR. The smaller this value, the smaller and more uniform the roughness of the spacing width pattern can be obtained.

[0067] [Evaluation of Limiting Resolution] Starting from the optimal exposure for forming the aforementioned LS pattern, the exposure was gradually increased in small increments. Using a Hitachi Advanced Technology (Group) Co., Ltd. (GMT) measuring SEM (CG-6300), the linewidth (nm) that limits the resolution during pattern formation was determined, and this value was defined as the limiting resolution (nm). The smaller this value, the better the limiting resolution, and the finer the pattern can be formed.

[0068] [Table 3] inhibitor Composition PAB / PEB (°C) Developer Eop (mJ / cm 2 ) LWR (nm) Limiting resolution (nm) Example 2-1 R-01 120 / 80 nBA 60 3.4 18 Example 2-2 R-02 120 / 80 nBA 61 3.7 20 Example 2-3 R-03 120 / 80 nBA 64 3.9 twenty one Examples 2-4 R-04 120 / 80 nBA 58 3.7 twenty one Examples 2-5 R-05 120 / 80 nBA 60 3.6 19 Examples 2-6 R-06 120 / 80 nBA 60 3.8 20 Comparative Example 2-1 CR-01 120 / 80 nBA 78 4.6 25 Comparative Example 2-2 CR-02 120 / 80 nBA 85 4.8 25 Comparative Examples 2-3 CR-03 105 / 90 nBA 73 4.8 twenty four Comparative Examples 2-4 CR-04 105 / 90 nBA 83 4.7 twenty four Comparative Examples 2-5 CR-05 105 / 90 nBA 73 4.8 twenty four

[0069] Developer: nBA (Butyl Acetate)

[0070] As shown in Table 3, the resist composition of the present invention still exhibits excellent sensitivity, LWR and resolution during negative tone development when forming LS patterns by EUV exposure.

[0071] [4] EUV lithography evaluation (contact hole pattern) [Examples 3-1~3-6, Comparative Examples 3-1~3-5] Each resist composition (R-01~R-6, CR-01~CR-05) was spin-coated onto a Si substrate with a silicon-containing spin-coated hard mask SHB-A940 (silicon content of 43% by mass) manufactured by Shin-Etsu Chemical Industry Co., Ltd. with a film thickness of 20 nm. The substrate was pre-baked (PAB) at the temperature recorded in Table 4 for 60 seconds using a heating plate to obtain a resist film with a film thickness of 50 nm. Then, the resist film was exposed using an ASML NXE3400 EUV scanning exposure machine (NA 0.33, σ 0.9 / 0.6, quadrupole illumination, mask for a 64nm pitch hole pattern on the wafer, +20% offset). It was then baked on a heated plate for 60 seconds at the temperatures described in Table 4 (PEB), followed by 30 seconds of development with the developer described in Table 4, to obtain a 32nm contact hole (CH) pattern. The sensitivity, CDU, and limiting resolution of the obtained CH pattern were evaluated using the methods described below. The results are shown in Table 4.

[0072] [Sensitivity Evaluation] For the aforementioned CH pattern, the Hitachi Advanced Technology Co., Ltd. (CG-6300) was used to observe the pattern and determine the optimal exposure Eop (mJ / cm2) for obtaining a hole pattern with a size of 32nm.

[0073] [CDU Evaluation] The dimensions of 50 CH patterns obtained by irradiation with the optimal exposure were measured, and the CDU was defined as three times the standard deviation (σ) obtained from the results (3σ). The smaller this value, the more uniform the aperture diameter of the pattern can be obtained.

[0074] [Evaluation of Limiting Resolution] By gradually reducing the exposure amount from the optimal exposure amount for forming the aforementioned CH pattern, the aperture diameter (nm) at the resolution limit during CH pattern formation was determined using a Hitachi Advanced Technology Co., Ltd. (CG-6300) measuring SEM, and this value was defined as the limiting resolution (nm). The smaller this value, the better the limiting resolution, and the finer the aperture diameter pattern can be obtained.

[0075] [Table 4] inhibitor Composition PAB / PEB (°C) Developer Eop (mJ / cm 2 ) CDU (nm) Limiting resolution (nm) Example 3-1 R-01 120 / 80 IPA 38 2.7 28 Example 3-2 R-02 120 / 80 IPA 41 2.9 29 Example 3-3 R-03 120 / 80 IPA 41 3.0 27 Examples 3-4 R-04 120 / 80 IPA 43 2.9 29 Examples 3-5 R-05 120 / 80 IPA 43 2.9 30 Examples 3-6 R-06 120 / 80 IPA 42 2.9 28 Comparative Example 3-1 CR-01 120 / 80 IPA 42 3.0 29 Comparative Example 3-2 CR-02 120 / 80 IPA 44 3.1 28 Comparative Example 3-3 CR-03 105 / 90 TMAH 48 3.8 33 Comparative Examples 3-4 CR-04 105 / 90 TMAH 45 3.9 34 Comparative Examples 3-5 CR-05 105 / 90 TMAH 51 3.9 33

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

[0077] As can be seen from the results shown in Table 4, the resist composition of the present invention has excellent sensitivity, CDU and resolution in the formation of contact hole patterns by EUV exposure.

Claims

1. A bismuth subatomic compound, represented by the following formula (1); wherein R1 and R2 are each independently a hydrocarbon group having 1 to 10 carbon atoms, which may also contain heteroatoms; furthermore, R1 and R2 may also bond to each other and form a ring together with the carbon atoms they bond to and the atoms between the carbon atoms; A1, A2 and A3 are each independently any one of the following groups, wherein the dashed line in the following formula represents the atomic bond with Ar1, Ar2 or Ar3; Ar1, Ar2 and Ar3 are each independently an aryl group having 6 to 20 carbon atoms, and in the aryl group, part or all of the hydrogen atoms on its aromatic ring may be replaced by halogen atoms or hydrocarbon groups having 1 to 20 carbon atoms, which may also contain heteroatoms.

2. An inhibitor composition comprising a superatomic bismuth compound as claimed in claim 1 and a solvent.

3. The inhibitor composition of claim 2 further contains a free radical scavenger.

4. The inhibitor composition of claim 2 further contains a surfactant.

5. A pattern forming method comprising the following steps: forming a resist film on a substrate using a resist composition as claimed in claim 2; exposing the resist film to high-energy radiation; and developing the exposed resist film using an organic solvent as a developer to dissolve the unexposed portions, thereby forming a negative pattern in which the exposed portions do not dissolve.