WO2024106167A1

WO2024106167A1 - Transition metal cluster compound, photosensitive composition, and pattern formation method

Info

Publication number: WO2024106167A1
Application number: PCT/JP2023/038693
Authority: WO
Inventors: 繁樹服部; 洋揮山本
Original assignee: 三菱ケミカル株式会社; 国立研究開発法人量子科学技術研究開発機構
Priority date: 2022-11-17
Filing date: 2023-10-26
Publication date: 2024-05-23

Abstract

Provided are a transition metal cluster compound that enables miniaturization of a circuit pattern; a photosensitive composition containing this compound; and a pattern formation method that uses this photosensitive composition.　The transition metal cluster compound is formed from a transition metal element and a ligand represented by general formula (1).　(In formula (1), X is a halogen element.)

Description

Transition metal cluster compound, photosensitive composition and pattern forming method

The present invention relates to a transition metal cluster compound suitable for use in ultra-microlithography processes such as the manufacture of ultra-LSIs and high-capacity microchips, as well as other photofabrication processes, a photosensitive composition containing the same, and a pattern formation method using the photosensitive composition.

2. Description of the Related Art Conventionally, in the manufacturing process of semiconductor devices, fine processing is carried out by lithography using a photoresist composition.
In semiconductor photolithography, circuit patterns become smaller as semiconductor devices become finer in accordance with Moore's Law, and further miniaturization is desired.
Photolithography is roughly divided into the shortening of wavelengths of the light source of the exposure tool and the photoresist that reacts to it. Photoresists are required to meet all of the requirements of high resolution, low roughness, and high sensitivity, and it is thought that conventional resists containing photoacid generators, known as chemically amplified resists, cannot handle ultra-fine patterns because the diffusion of acid leads to a decrease in resolution.

In recent years, non-chemically amplified photoresists based on compounds containing metal elements such as Zn and Sn have been proposed, and it has been reported that they can be used to form fine patterns using next-generation exposure equipment that uses EUV (extreme ultraviolet) light.

For example, the following Patent Documents 1 to 5 and Non-Patent Documents 1 to 3 disclose methods for forming resist patterns using EUV or electron beams.

JP 2015-108781 A JP 2001-072716 A JP 2017-173537 A JP 2012-185484 A JP 2021-102604 A

In photolithography, particularly in semiconductor photolithography technology, there is a demand for photosensitive compositions and pattern formation methods that can achieve even finer circuit patterns.

The object of the present invention is to provide a transition metal cluster compound capable of realizing fine circuit patterns, a photosensitive composition containing the same, and a pattern formation method using this photosensitive composition.

The present invention has the following aspects:

[1] A transition metal cluster compound composed of a transition metal element and a ligand represented by the following general formula (1).

(In formula (1), X is a halogen element.)

[2] The transition metal cluster compound according to [1], characterized in that X is composed of two or more different ligands represented by the general formula (1).

[3] The transition metal cluster compound according to [1] or [2], characterized in that the transition metal element is one or more selected from zirconium and hafnium.

[4] A transition metal cluster compound according to any one of [1] to [3], characterized in that it is composed of 4 to 6 transition metal elements and a ligand represented by the general formula (1).

[5] A transition metal cluster compound according to any one of [1] to [4], characterized in that X is selected from fluorine, chlorine, bromine, or iodine.

[6] The transition metal cluster compound according to [5], wherein X is fluorine.

[7] A method for producing a transition metal cluster compound according to any one of [1] to [6], comprising reacting an alkoxide solution of a transition metal element with 2-halogenated acrylic acid.

[8] A photosensitive composition containing a transition metal cluster compound according to any one of [1] to [6].

[9] The photosensitive composition according to [8], characterized in that it contains one or more selected from dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol, methyl alcohol, ethyl alcohol, 1-propanol, and 2-propanol.

[10] The photosensitive composition according to [9], which contains dimethylformamide.

[11] A photosensitive composition according to any one of [8] to [11], which reacts to light having a wavelength of 6.5 nm or more and 13.5 nm or less.

[12] A pattern forming method comprising the steps of applying the photosensitive composition according to any one of [8] to [11] to a substrate, exposing the composition to actinic radiation, and developing the composition using a developer.

[13] The pattern formation method according to [12], characterized in that the developer is one or more selected from dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol, methyl alcohol, ethyl alcohol, 1-propanol, and 2-propanol.

[14] A method for producing a substrate having a pattern layer obtained by the pattern formation method described in [12] or [13].

The transition metal cluster compound and photosensitive composition of the present invention have high sensitivity and high resolution, and can simultaneously satisfy high sensitivity, high resolution, good pattern shape and its reproducibility, and good line width roughness in ultrafine regions.
Here, line width roughness refers to the phenomenon in which the edge of the resist pattern and the substrate interface fluctuates irregularly in the direction perpendicular to the line direction due to the characteristics of the resist, so that the edge appears uneven when viewed from directly above the pattern. This unevenness is transferred during the etching process using the resist as a mask, degrading the electrical characteristics and reducing the yield.
According to the pattern forming method of the present invention using such a photosensitive composition of the present invention, it becomes possible to fully meet the recent demand for finer circuit patterns.

Detailed Description of the Invention

Hereinafter, the present invention will be described based on one embodiment, however, the present invention is not limited to this embodiment.
In this specification, there are some descriptions using "~" to express a numerical range from a lower limit value to an upper limit value, but the numerical range in this description is a numerical range specified as being equal to or greater than the lower limit value and equal to or less than the upper limit value, including the lower limit value and the upper limit value. In the present invention, a cluster compound means a metal complex molecule having a metal atom and a ligand, in which multiple metal atoms are bonded to each other directly or through a bridging ligand.

[Transition Metal Cluster Compounds]
A transition metal cluster compound according to one embodiment of the present invention (hereinafter also referred to as the present cluster compound) is composed of a transition metal element and a ligand represented by the following general formula (1). The present cluster compound may contain oxygen and/or hydroxyl groups in the structure, and may preferably contain μ-oxo (μ-O) and/or μ-hydroxy groups (μ-OH).

(In formula (1), X is a halogen element.)

The transition metal element of the present cluster compound is preferably one or more selected from zirconium, hafnium, and titanium, and among these, zirconium or hafnium is preferred. Hafnium is an element of the same group as zirconium and has very similar chemical and physical properties.
The number of transition metal elements in the present cluster compound is not limited, but is preferably 4 to 6, more preferably 5 to 6, and most preferably 6.

In the above general formula (1), X is preferably a halogen element selected from fluorine, chlorine, bromine, or iodine, and among these, fluorine is preferred. It is also preferred that X is composed of two or more different types, and in particular, one of them is preferably fluorine.

The ligand of the above general formula (1) preferably has a structure in which the oxygen anion site is bonded to a transition metal element. The structure of the ligand can be analyzed by NMR.

The molecular weight of the present cluster compound is preferably 1,000 to 5,000, more preferably 1,000 to 4,000, and even more preferably 1,500 to 3,000.
If the molecular weight of the cluster compound is equal to or less than the upper limit, the volume is small, so roughness and resolution are expected to be high, while if the molecular weight is equal to or more than the lower limit, the coating properties and etching resistance tend to be improved. Note that this molecular weight is a guideline, and does not determine the lithography properties by itself.

[Production method]
The present cluster compound can be produced, for example, by reacting a solution of an alkoxide of a transition metal element with a 2-halogenated acrylic acid.
More specifically, the transition metal element alkoxide solution and 2-haloacrylic acid are placed in a reaction vessel, stirred, and then stored for preferably 1 to 24 hours, more preferably 3 to 24 hours.
The precipitated crystals are then filtered to obtain the present cluster compound.
The storage temperature is preferably room temperature, specifically, preferably 15 to 40°C, more preferably 20 to 30°C.
The reaction vessel is preferably a sealed vessel, and for small volumes, for example, a Schlenk tube or the like can be used, and the reaction is preferably carried out in an argon atmosphere.

Examples of alkoxide solutions of transition metal elements include zirconium propoxide solution, zirconium n-butoxide, and zirconium 2-ethylhexoxide.

Examples of 2-halogenated acrylic acids include 2-fluoroacrylic acid, 2-chloroacrylic acid, 2-bromoacrylic acid, and 2-iodoacrylic acid.

The weight ratio of the transition metal element alkoxide solution to the 2-halogenated acrylic acid is preferably 1:2 to 1:20, and more preferably 1:3 to 1:10.

[Photosensitive Composition]
A photosensitive composition according to one embodiment of the present invention (hereinafter also referred to as the present photosensitive composition) contains the present cluster compound. The present photosensitive composition may contain only one type of the present cluster compound, or may contain two or more types of the present cluster compound.

The content of the present cluster compound in the present photosensitive composition is usually 30 to 100% by mass, preferably 40 to 100% by mass, and particularly preferably 50 to 100% by mass, based on the total of all components of the photosensitive composition other than the solvent.
When the content of the present cluster compound in the present photosensitive composition is equal to or greater than the above lower limit, good exposure sensitivity can be obtained.

[Photoacid generator]
The photosensitive composition can also function by including, together with the cluster compound, a photoacid generator that generates an acid upon the action of actinic radiation.
Examples of actinic radiation include the emission line spectrum of a mercury lamp, far ultraviolet light represented by an excimer laser, extreme ultraviolet light (EUV light), X-rays, and electron beams. From the viewpoint of resolution, it is preferable that the exposure wavelength is small, and EUV light emitting light with a wavelength of 6.5 nm or more and 13.5 nm or less is preferred.

The photoacid generator that generates an acid upon exposure to chemical radiation is not particularly limited as long as it is a known compound, but is preferably a compound that generates an organic acid, such as at least one of sulfonic acid, bis(alkylsulfonyl)imide, and tris(alkylsulfonyl)methide, upon exposure to chemical radiation.

The photoacid generators may be used alone or in combination of two or more. When two or more types are used in combination, for example, (1) two types of photoacid generators having different acid strengths are used in combination, or (2) two types of photoacid generators having different sizes (molecular weight or carbon number) of generated acids are used in combination, etc. are preferred.
Examples of the embodiment of (1) include a combined use of a sulfonic acid generator having fluorine and a tris(fluoroalkylsulfonyl)methide acid generator, a combined use of a sulfonic acid generator having fluorine and a sulfonic acid generator not having fluorine, and a combined use of an alkylsulfonic acid generator and an arylsulfonic acid generator.
As an example of the embodiment (2), it is possible to use in combination two kinds of acid generators which generate acid anions with a difference of 4 or more carbon atoms.

In particular, the present photosensitive composition is preferably a photosensitive composition for use with actinic radiation, and a photosensitive composition that reacts with actinic radiation is preferred because the development speed in a developer changes and a pattern can be formed after a certain period of development.
As the actinic radiation, a shorter light wavelength is preferable since higher resolution can be obtained, and light with a wavelength of 6.5 nm or more and 13.5 nm or less, that is, EUV light, is preferable.
That is, the present photosensitive composition is preferably a photosensitive composition that reacts to light having a wavelength of 6.5 nm or more and 13.5 nm or less.

The present photosensitive compound reacts with light even when used alone in the photosensitive composition. When a photoacid generator is added, it acts synergistically with the present cluster compound in the photosensitive composition to increase the photosensitivity of the present cluster compound. Therefore, when the photosensitivity of a photosensitive composition composed only of the present cluster compound is insufficient for the required specifications, it is preferable to add a photoacid generator.
When the present photosensitive composition contains a photoacid generator, the content of the photoacid generator in the present photosensitive composition (the total amount when a plurality of photoacid generators are used in combination) is preferably 0.1 to 30 mass %, more preferably 0.5 to 20 mass %, and even more preferably 1 to 15 mass %, based on the total of the components other than the solvent in the photosensitive composition.
When the content of the photoacid generator in the photosensitive composition is equal to or more than the above-mentioned lower limit, the effect of enhancing photosensitivity can be obtained, whereas when the content is equal to or less than the above-mentioned upper limit, the composition is less susceptible to the poor film-forming properties of the photoacid generator, and therefore good film-forming properties based on the photosensitive compound of the present invention can be obtained, which is preferable.

[solvent]
The photosensitive composition generally contains a solvent for preparing the composition.
The solvent for preparing the photosensitive composition is not particularly limited as long as it dissolves each component, but preferably contains one or more selected from dimethylformamide, dimethylsulfoxide, tetrahydrofuran, ethylene glycol, methyl alcohol, ethyl alcohol, 1-propanol, and 2-propanol. For example, alkylene glycol monoalkyl ether carboxylates (propylene glycol monomethyl ether acetate (PGMEA; 1-methoxy-2-acetoxypropane)), alkylene glycol monoalkyl ethers (propylene glycol monomethyl ether (PGME; 1-methoxy-2-propanol), alkyl lactate esters (ethyl lactate, methyl lactate, etc.), cyclic lactones (γ-butyrolactone, etc., preferably having 4 to 10 carbon atoms), linear or cyclic ketones (2-heptanone, cyclohexanone, etc., preferably having 4 to 10 carbon atoms), alkylene carbonates (ethylene carbonate, propylene carbonate, etc.), alkyl carboxylates (alkyl acetates such as butyl acetate are preferred), alkoxy alkyl acetates (ethyl ethoxypropionate), alkylamides (N,N-dimethylformamide), alkyl sulfoxides (dimethyl sulfoxide), etc. Other usable solvents include, for example, the solvents described in U.S. Patent Application Publication No. 2008/0248425 A1, paragraphs [0244] and thereafter.

Of the above, N,N-dimethylformamide, dimethyl sulfoxide, alkylene glycol monoalkyl ether carboxylate and alkylene glycol monoalkyl ether are preferred.

These solvents may be used alone or in combination of two or more. When two or more types are mixed, it is preferable to mix a solvent having a hydroxyl group with a solvent having no hydroxyl group.
As the solvent having a hydroxyl group, alkylene glycol monoalkyl ether is preferred, and as the solvent not having a hydroxyl group, alkylene glycol monoalkyl ether carboxylate, N,N-dimethylformamide, and dimethylsulfoxide are preferred.

The content of the solvent in the total amount of the photosensitive composition can be adjusted as appropriate depending on factors such as the thickness of the pattern film to be formed, but is generally adjusted so that the total concentration of the components other than the solvent in the photosensitive composition is 0.5 to 30% by mass, preferably 1.0 to 20% by mass, more preferably 1.5 to 10% by mass, and even more preferably 1.5 to 5% by mass.

[Surfactant]
The photosensitive composition of the present invention preferably further contains a surfactant, and the surfactant is preferably a fluorine-based and/or silicone-based surfactant.
Examples of surfactants that fall under these categories include Megafac F176 and Megafac R08 manufactured by Dainippon Ink and Chemicals, Inc., PF656 and PF6320 manufactured by OMNOVA, Troysol S-366 manufactured by Troy Chemical Co., Ltd., Fluorad FC430 manufactured by Sumitomo 3M Limited, and polysiloxane polymer KP-341 manufactured by Shin-Etsu Chemical Co., Ltd.
Moreover, surfactants other than fluorine-based and/or silicon-based surfactants can also be used, more specifically, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, etc.

Other known surfactants can be used as appropriate. Examples of usable surfactants include those described in paragraphs [0273] and onward in U.S. Patent Application Publication No. 2008/0248425 A1.

The surfactants may be used alone or in combination of two or more kinds.
The content of the surfactant is preferably from 0.0001 to 2% by mass, more preferably from 0.001 to 1% by mass, based on the total of all components other than the solvent in the photosensitive composition.

[Other additives]
In addition to the components described above, the present photosensitive composition may appropriately contain carboxylic acids, carboxylate onium salts, dissolution inhibiting compounds having a molecular weight of 3,000 or less as described in, for example, Proceeding of SPIE, 2724, 355 (1996), dyes, plasticizers, photosensitizers, light absorbers, antioxidants, and the like.
In particular, the carboxylic acid is preferably used to improve performance. As the carboxylic acid, an aromatic carboxylic acid such as benzoic acid or naphthoic acid is preferable.
The content of the carboxylic acid is preferably from 0.01 to 10% by mass, more preferably from 0.01 to 5% by mass, and further preferably from 0.01 to 3% by mass, based on the total of all components other than the solvent in the photosensitive composition.

[Method of producing the present photosensitive composition]
The present photosensitive composition can be produced by dissolving the present cluster compound, a photoacid generator used as necessary, and other components in a solvent for preparation of the solution, and filtering the solution through a filter as necessary. The filter is preferably made of polytetrafluoroethylene, polyethylene, or nylon with a pore size of 0.2 μm or less, more preferably 0.1 μm or less, and even more preferably 0.05 μm or less.

[Pattern Forming Method]
A pattern formation method according to one embodiment of the present invention (hereinafter also referred to as the present pattern formation method) comprises the steps of forming a photosensitive layer on a substrate using the present photosensitive composition, irradiating predetermined regions of the photosensitive layer with actinic radiation to perform pattern exposure, and developing the exposed photosensitive layer with a developer to selectively remove exposed or unexposed regions of the photosensitive layer.

[Photosensitive layer formation process]
The photosensitive layer can be formed by applying the photosensitive composition to a substrate (e.g., silicon, silicon dioxide coated) such as those used in the manufacture of integrated circuit elements by a suitable application method such as a spinner, and then drying at 50 to 150°C.
In this case, if necessary, a commercially available inorganic or organic anti-reflective film can be used, and further, an anti-reflective film can be applied to the lower layer of the resist.

[Exposure process]
In the present invention, unless otherwise specified, "exposure" includes not only exposure to far ultraviolet light represented by a mercury lamp or an excimer laser, X-rays, EUV light, and the like, but also drawing with particle beams such as electron beams and ion beams.
The exposure can be carried out by irradiating predetermined areas of the formed photosensitive layer with actinic radiation through a predetermined mask to perform pattern exposure, or by irradiating with an electron beam to perform pattern exposure by drawing (direct drawing) without using a mask.
The actinic radiation is not particularly limited, but examples thereof include KrF excimer laser, ArF excimer laser, EUV light, and electron beams. EUV light and electron beams are preferred, and as described above, EUV light that emits light with a wavelength of 6.5 nm or more and 13.5 nm or less is preferred.

After the exposure, baking (heating) may or may not be performed before development.
When baking (heating) is performed, the heating temperature is preferably from 50 to 150°C, more preferably from 60 to 150°C, and even more preferably from 80 to 140°C.
When baking (heating) is performed, the heating time is preferably from 30 to 300 seconds, more preferably from 30 to 180 seconds, and even more preferably from 30 to 90 seconds.
Heating can be carried out by a means provided in a normal exposure/developing machine, and may also be carried out using a hot plate or the like.

[Development process]
After exposure, development is carried out using a developer to selectively remove the exposed or unexposed areas of the photosensitive layer.

<Developer>
As the developer, it is preferable to use an organic solvent, preferably an organic solvent having a vapor pressure of 5 kPa or less, more preferably 3 kPa or less, and particularly preferably 2 kPa or less at 20° C. By making the vapor pressure of the organic solvent 5 kPa or less, evaporation of the developer on the substrate or in the developing cup is suppressed, improving the temperature uniformity within the surface of the pattern-formed substrate, and as a result, improving the dimensional uniformity within the surface of the pattern-formed substrate.

As the organic solvent used as the developer, various organic solvents are widely used. For example, at least one solvent selected from ester-based solvents, ketone-based solvents, alcohol-based solvents, amide-based solvents, sulfoxide-based solvents, ether-based solvents, hydrocarbon-based solvents, and the like can be used.
In particular, the developer preferably contains at least one solvent selected from the group consisting of amide-based solvents, ketone-based solvents, ester-based solvents, alcohol-based solvents, and ether-based solvents.

Examples of ester solvents include alkyl carboxylate solvents such as methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, ethyl-3-ethoxypropionate, propylene glycol diacetate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, and propyl lactate; alkylene glycol monoalkyl ether carboxylate solvents such as propylene glycol monomethyl ether acetate (PGMEA; also known as 1-methoxy-2-acetoxypropane), ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and propylene glycol monoethyl ether acetate; with butyl acetate, amyl acetate, ethyl lactate, and propylene glycol monomethyl ether acetate being more preferred.

Ketone solvents include, for example, 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetyl carbinol, acetophenone, methyl naphthyl ketone, isophorone, and propylene carbonate. Alkyl ketone solvents, such as methyl isobutyl ketone, methyl amyl ketone, cyclopentanone, and cyclohexanone, are more preferred.

Examples of alcohol-based solvents include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol including 1-propanol or 2-propanol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol such as n-hexyl alcohol, heptyl alcohol such as n-heptyl alcohol, octyl alcohol such as n-octyl alcohol, and decanol such as n-decanol; and glycols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, and 1,4-butylene glycol. Examples of such solvents include alkylene glycol monoalkyl ether solvents such as ethylene glycol monomethyl ether, propylene glycol monomethyl ether (PGME; also known as 1-methoxy-2-propanol), ethylene glycol monoethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, and triethylene glycol monoethyl ether; glycol ether solvents such as methoxymethylbutanol and propylene glycol dimethyl ether; and phenol solvents such as phenol and cresol. Of these, 1-hexanol, 2-hexanol, 1-octanol, 2-ethyl-hexanol, propylene glycol monomethyl ether, and cresol are more preferred.

As the amide solvent, for example, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric triamide, 1,3-dimethyl-2-imidazolidinone, etc. can be used.
As the sulfoxide solvent, for example, dimethyl sulfoxide can be used.

Ether solvents include, for example, the alkylene glycol monoalkyl ether solvents and glycol ether solvents described above, as well as dioxane, tetrahydrofuran, tetrahydropyran, etc.

Examples of hydrocarbon solvents include aromatic hydrocarbon solvents such as toluene and xylene, and aliphatic hydrocarbon solvents such as pentane, hexane, octane, decane, and dodecane.

The developer preferably contains one or more solvents selected from alkylene glycol monoalkyl ether carboxylate solvents, alkylene glycol monoalkyl ether solvents, alkyl carboxylate solvents, and alkyl ketone solvents, and more preferably contains one or more solvents selected from dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol, methyl alcohol, ethyl alcohol, 1-propanol, and 2-propanol.

As the developer, it is preferable to use a developer containing at least one organic solvent selected from the group consisting of ester solvents that do not have a hydroxyl group in the molecule, ketone solvents that do not have a hydroxyl group in the molecule, and ether solvents, amide solvents, and sulfoxide solvents that do not have a hydroxyl group in the molecule.

The organic solvent used as the developer in the present invention is preferably an organic solvent with a solubility parameter (SP value) of 7.5 to 15. An organic solvent with a solubility parameter of 7.5 or more is preferred because it increases the development speed of the dissolved area, while an organic solvent with a solubility parameter of 15 or less is preferred because it suppresses the development speed of the pattern forming area. It is more preferred that the solubility parameter of the organic solvent in the developer is 8 to 15.

In the present invention, the solubility parameter (SP value) is calculated by the method proposed by Fedors et al. Specifically, the value is determined by referring to "POLYMER ENGINEERING AND SCIENCE, FEBRUARY, 1974, Vol. 14, No. 2, ROBERT F. FEDORS. (pp. 147-154)". The SP value is a physical property value determined by the content of hydrophobic and hydrophilic groups in the molecule, and when a mixed solvent is used, it means the value for the mixture.

Organic solvents that satisfy the above SP values include N,N-dimethylformamide (SP value 12.1), dimethyl sulfoxide (SP value 14.5), diethylene glycol monomethyl ether (SP value = 10.7), triethylene glycol monomethyl ether (SP value = 10.7), ethylene glycol monoisopropyl ether (SP value = 10.9), ethylene glycol monobutyl ether (SP value = 10.2), diethylene glycol monobutyl ether (SP value = 10.0), triethylene glycol monobutyl ether (SP value = 10.1), P value = 10.0), ethylene glycol monoisobutyl ether (SP value = 9.1), ethylene glycol monohexyl ether (SP value = 9.9), diethylene glycol monohexyl ether (SP value = 9.7), diethylene glycol mono 2-ethylhexyl ether (SP value = 9.3), ethylene glycol monoallyl ether (SP value = 10.8), ethylene glycol monophenyl ether (SP value = 10.8), ethylene glycol monobenzyl ether (SP value = 10.9), propylene glycol monomethyl ether ether (SP value = 10.0), dipropylene glycol monomethyl ether (SP value = 9.7), tripropylene glycol monomethyl ether (SP value = 9.4), propylene glycol monopropyl ether (SP value = 9.6), dipropylene glycol monopropyl ether (SP value = 9.8), propylene glycol monobutyl ether (SP value = 9.0), dipropylene glycol monobutyl ether (SP value = 9.6), ethylene glycol monomethyl ether acetate (SP value = 10.0), ethylene glycol Examples include monoethyl ether acetate (SP value = 9.6), ethylene glycol monobutyl ether acetate (SP value = 8.9), diethylene glycol monoethyl ether acetate (SP value = 9.4), diethylene glycol monobutyl ether acetate (SP value = 9.0), propylene glycol monomethyl ether acetate (SP value = 9.4), propylene glycol monoethyl ether acetate (SP value = 9.0), and dipropylene glycol monomethyl ether acetate (SP value = 9.2).

The above organic solvents may be used in combination, or may be mixed with other solvents or water.

The concentration of the organic solvent (total if multiple organic solvents are mixed) in the developer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. It is particularly preferable for the developer to consist essentially of organic solvents. Note that the term "consisting essentially of organic solvents" includes cases in which the developer contains trace amounts of surfactants, antioxidants, stabilizers, defoamers, etc.

The water content in the developer is preferably 10% by weight or less, more preferably 5% by weight or less, particularly preferably 3% by weight or less, and most preferably substantially no water. By keeping the water content at 10% by weight or less, good development characteristics can be obtained.

If necessary, a suitable amount of a surfactant may be added to the developer used in the present invention.
As the surfactant, the same surfactants as those described above for use in the photosensitive composition of the present invention can be used.
The amount of the surfactant used is usually from 0.001 to 5% by weight, preferably from 0.005 to 2% by weight, and more preferably from 0.01 to 0.5% by weight, based on the total amount of the developer.

<Developing method>
Examples of the developing method that can be applied include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by piling up the developer on the substrate surface by surface tension and leaving it still for a certain period of time (paddle method), a method of spraying the developer on the substrate surface (spray method), and a method of continuously dispensing the developer while scanning a developer dispensing nozzle at a constant speed over a substrate rotating at a constant speed (dynamic dispense method).
After the development step, a step of stopping the development while replacing the solvent with another solvent may be carried out.
The development time is preferably a time sufficient for the cluster compound and the like in the unexposed or exposed areas of the photosensitive layer to be sufficiently dissolved, and is usually preferably from 10 to 300 seconds, more preferably from 20 to 120 seconds.
The temperature of the developer is preferably from 0 to 50°C, and more preferably from 15 to 35°C.
The amount of developer can be appropriately adjusted depending on the developing method.

[Rinse process]
The present pattern formation method may include a step of washing with a rinsing liquid containing an organic solvent after the developing step.

<Rinse solution>
The organic solvent used in the rinsing liquid preferably has a vapor pressure of 0.05 kPa or more and 5 kPa or less, more preferably 0.1 kPa or more and 5 kPa or less, and most preferably 0.12 kPa or more and 3 kPa or less at 20° C. By setting the vapor pressure of the organic solvent used in the rinsing liquid to 0.05 kPa or more and 5 kPa or less, the temperature uniformity within the wafer surface is improved, and further swelling caused by the penetration of the rinsing liquid is suppressed, improving the dimensional uniformity within the wafer surface.

As the rinse solution, various organic solvents can be used, but for the present cluster compound, it is preferable to use a rinse solution containing at least one organic solvent selected from hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents, amide solvents and ether solvents, or water.
More preferably, after the development, a step of washing is performed using a rinse solution containing at least one organic solvent selected from the group consisting of ketone solvents, ester solvents, alcohol solvents, amide solvents, and hydrocarbon solvents. Even more preferably, after the development, a step of washing is performed using a rinse solution containing at least one organic solvent selected from the group consisting of alcohol solvents and hydrocarbon solvents.
Specific examples of the ketone-based solvent, ester-based solvent, alcohol-based solvent, amide-based solvent, ether-based solvent, and hydrocarbon-based solvent used as the rinsing liquid are the same as those described above for the developer.
It is particularly preferable to use a rinse solution containing at least one organic solvent selected from the group consisting of monohydric alcohol solvents, hydrocarbon solvents, and amide solvents.

Here, examples of the monohydric alcohol solvent used in the rinsing step after development include linear, branched and cyclic monohydric alcohols. Specifically, 1-butanol, 2-butanol, 3-methyl-1-butanol, tert-butyl alcohol, isopropyl alcohol, cyclopentanol, cyclohexanol and the like can be used, and 1-butanol, 2-butanol, 3-methyl-1-butanol and isopropyl alcohol are preferred.
Examples of the hydrocarbon solvent include aromatic hydrocarbon solvents such as toluene and xylene, and aliphatic hydrocarbon solvents such as octane, decane, and dodecane.
As the amide solvent, N,N-dimethylformamide or the like can be used.

The above components may be mixed in combination, or may be mixed with organic solvents other than those listed above.

The organic solvent may be mixed with water, but the water content in the rinse solution is usually 30% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 3% by weight or less. It is most preferable that the rinse solution does not contain water. By keeping the water content at 30% by weight or less, good development characteristics can be obtained.

The rinse solution may contain a suitable amount of a surfactant.
As the surfactant, the same surfactants as those used in the photosensitive composition described above can be used, and the amount of the surfactant used is usually 0.001 to 5 mass %, preferably 0.005 to 2 mass %, and more preferably 0.01 to 0.5 mass %, based on the total amount of the rinse solution.

<Rinsing method>
In the rinsing step, the developed pattern-formed substrate is washed with a rinsing liquid containing the organic solvent.
The cleaning method is not particularly limited, but may be, for example, a method of continuously applying the rinse solution onto a substrate rotating at a constant speed (spin coating method), a method of immersing the substrate in a tank filled with the rinse solution for a certain period of time (dip method), a method of spraying the rinse solution onto the substrate surface (spray method), etc. Among these, it is preferable to perform the cleaning process by the spin coating method, rotate the substrate after cleaning at a rotation speed of 2000 to 4000 rpm, and remove the rinse solution from the substrate. The rotation time of the substrate can be set within a range that achieves removal of the rinse solution from the substrate depending on the rotation speed, but is usually 10 seconds to 3 minutes. It is preferable to perform rinsing at room temperature.
The rinsing time is preferably set so that the developing solvent does not remain on the substrate, and is usually preferably from 10 to 300 seconds, more preferably from 20 to 120 seconds.
The temperature of the rinse solution is preferably from 0 to 50°C, more preferably from 15 to 35°C.
The amount of the rinse solution can be appropriately adjusted depending on the rinse method.

[Post-processing process]
After the development treatment or rinsing treatment, a treatment can be carried out in which the developer or rinsing liquid adhering to the pattern is removed by using a supercritical fluid.
Furthermore, after the development treatment, rinsing treatment, or treatment with a supercritical fluid, a heat treatment can be carried out to remove the solvent remaining in the pattern. The heating temperature and time are not particularly limited as long as a good resist pattern can be obtained, and are usually 40 to 160° C. and 10 seconds to 3 minutes. The heat treatment may be carried out multiple times.

[Application]
The photosensitive composition and the pattern forming method are suitable for use in the production of semiconductor microcircuits, such as the manufacture of ultra-large scale integrated circuits and high-capacity microchips. During the production of semiconductor microcircuits, the resist film on which the pattern is formed is subjected to circuit formation and etching, and the remaining resist film portion is finally removed with a solvent or the like. Therefore, unlike so-called permanent resists used in printed circuit boards and the like, no resist film derived from the photosensitive composition remains in the final product, such as a microchip.

Below, one embodiment of the present invention will be described. However, the present invention is not limited to this embodiment. In the embodiment, "parts" and "%" are by weight unless otherwise specified.

The following compounds 1 to 3 were prepared. The composition and ligand structure of each compound were measured by ¹ H-NMR and MALDI-MS.

<Compound 1>
A reaction vessel was charged with 2.0 ml (6.2 mmol) of a zirconium propoxide solution (70% propanol solution) manufactured by Tokyo Chemical Industry Co., Ltd. and 2.51 g (23.56 mmol) of 2-chloroacrylic acid manufactured by Sigma-Aldrich Co., Ltd., and stored at room temperature for 8 hours. The precipitated crystals were filtered to obtain 1.37 g of a white powder.
^1H NMR ( _CDCl3 , ppm): δ 5.64 (m, 12H, CH), 5.09 ₍ m _, 12H, CH) _. MALDI-MS: 1615.3 (isotopic pattern: _{C24H28Cl8O30Zr6} ) _.
That is, Zr ₆ O ₄ (OH) ₄ ClAc ₁₂ (ClAc = 2-chloroacrylic acid).

<Compound 2>
A reaction vessel was charged with 1.0 ml (3.1 mmol) of a zirconium propoxide solution (70% propanol solution) manufactured by Tokyo Chemical Industry Co., Ltd. and 1.06 g (25.17 mmol) of 2-fluoroacrylic acid manufactured by Sigma-Aldrich, and the mixture was stored at room temperature for 8 hours. The precipitated crystals were filtered and washed with isopropyl alcohol to obtain 0.47 g of a white powder.
^1H NMR ( _CDCl3 , ppm): δ 5.85 (m, 12H, CH), 5.75 (m, 12H, CH). Anal. Calcd: C, 24.74; H, 1.61; F, 13.04; O, 29.29; Zr, 31.31. Found: C _, 23.0; H, 2.3; F, 7.9; O, 36.8; Zr, 30.0 _. _MALDI -MS: 1487.5 (isotopic pattern: _{C24H28F8O30Zr6} ) _.
That is, Zr ₆ O ₄ (OH) ₄ FAc ₁₂ (FAc=2-fluoroacrylic acid).

<Compound 3>
2.62 ml (8.12 mmol) of a zirconium propoxide solution (70% propanol solution) manufactured by Tokyo Chemical Industry Co., Ltd. and 2.51 g (25.17 mmol) of 2-bromoacrylic acid manufactured by Sigma-Aldrich were placed in a reaction vessel and stored at room temperature for 8 hours. The precipitated crystals were filtered and washed with isopropyl alcohol to obtain 3.41 g of a light brown powder.
^1H NMR ( _CDCl3 , ppm): δ 7.09 (m, 12H, CH), 6.40 ₍ m _, 12H, CH) _. MALDI-MS: 1966.8 (isotopic pattern: _{C24H28Br8O30Zr6} ) _.
That is, Zr ₆ O ₄ (OH) ₄ BrAc ₁₂ (BrAc = 2-bromoacrylic acid).

<Preparation of Photosensitive Composition (Resist Solution)>
Each of the above compounds 1 to 3 was dissolved in N,N-dimethylformamide at a concentration of 5% by mass, and the solution was filtered through a 0.2 μm filter to obtain a resist solution.

<Resist film formation and pattern drawing>
The prepared resist solution was applied onto a pattern-forming substrate (silicon wafer) by spin coating to form a resist film with a thickness of about 40 nm (pattern) and about 90 nm (sensitivity). The obtained resist film was baked at 90° C. for 90 seconds, and then pattern writing was performed using an electron beam lithography device (electron beam acceleration voltage: 100 keV).

<Developing>
After the pattern writing, Compounds 1 to 3 were developed with N,N-dimethylformamide (25° C., 60 seconds) to obtain negative patterns, which were designated as Examples 1 to 3, respectively.

<Sensitivity measurement>
Extreme ultraviolet (EUV) exposure was performed with varying doses of irradiation, and the film thickness of the developed pattern was measured with a contact step gauge. The dose of electron beam irradiation at which the amount of change in film thickness was maximized was determined as the sensitivity.
The results are shown in Table 1.

[Comparative Example 1]
Polystyrene (PS, weight average molecular weight 4000) manufactured by Aldrich was dissolved in propylene glycol monomethyl ether acetate at a concentration of 2% by mass, and the solution was filtered through a 0.2 μm filter to prepare a resist solution.

The resist solution of Comparative Example 1 was evaluated in the same manner as in Examples 1 to 3, and the results are shown in Tables 1 and 2.

The results in Table 1 show that the sensitivity is in the order of Example 2, Example 1, and Example 3, with Example 2 being the highest.

<Resolution evaluation>
The resolution of Examples 1 to 3 and Comparative Example 1 was evaluated using an electron beam lithography device. The resolution was evaluated by drawing a line and space (line:space=1:1) pattern with hp (half pitch) of 100 nm or 50 nm, developing it, and observing each pattern with a scanning electron microscope. When a line and space pattern with hp of 100 nm or 50 nm was confirmed, it was rated as "A", and when no pattern was confirmed, it was rated as "B".
The results are shown in Table 2.

[result]
Examples 1 to 3 were rated as A, and from the results of the electron beam (EB) writing test, it was understood that a line and space (L&S) pattern (1:1) with a half pitch (hp) of 100 nm or 50 nm could be formed, and that the sensitivity to EUV exposure was very high. The transition metal cluster compound consisting of halogenated acrylic acid and metal alkoxide can be used practically as a photoresist corresponding to ultrafine patterns.
In contrast, Comparative Example 1 was rated B at hp 50 nm, which is unsuitable for ultra-fine patterns and leaves room for improvement in practical use.

Claims

A transition metal cluster compound comprising a transition metal element and a ligand represented by the following general formula (1):

(In formula (1), X is a halogen element.)
The transition metal cluster compound according to claim 1, characterized in that X is composed of two or more different ligands represented by the general formula (1).
The transition metal cluster compound according to claim 1, characterized in that the transition metal element is one or more selected from zirconium and hafnium.
The transition metal cluster compound according to claim 1, characterized in that it is composed of 4 to 6 transition metal elements and a ligand represented by the general formula (1).
The transition metal cluster compound according to claim 1, characterized in that X is selected from fluorine, chlorine, bromine, or iodine.
The transition metal cluster compound according to claim 1, characterized in that X is fluorine.
A method for producing a transition metal cluster compound according to any one of claims 1 to 6, comprising reacting an alkoxide solution of a transition metal element with 2-halogenated acrylic acid.
A photosensitive composition comprising the transition metal cluster compound according to any one of claims 1 to 6.
The photosensitive composition according to claim 8, characterized in that it contains one or more selected from dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol, methyl alcohol, ethyl alcohol, 1-propanol, and 2-propanol.
The photosensitive composition according to claim 9, characterized in that it contains dimethylformamide.
The photosensitive composition according to claim 8, characterized in that it reacts to light having a wavelength of 6.5 nm or more and 13.5 nm or less.
A pattern forming method comprising the steps of applying the photosensitive composition according to claim 8 to a substrate, exposing the substrate to actinic radiation, and developing the substrate with a developer.
The pattern formation method according to claim 12, characterized in that the developer is one or more selected from dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol, methyl alcohol, ethyl alcohol, 1-propanol, and 2-propanol.
A method for producing a substrate having a patterned layer obtained by the pattern forming method according to claim 12.