Block copolymer, composition for pattern formation, method for producing block copolymer, and method for forming pattern

Abstract

To provide a novel block copolymer capable of forming a microdomain structure. The block copolymer contains an adamantyl (meth)acrylate polymer unit in which a monomer unit derived from an adamantyl (meth)acrylate is polymerized and a styrene polymer unit in which a monomer unit derived from styrene is polymerized.

Description

Block copolymer, pattern-forming composition, method for producing block copolymer, and method for pattern formation

[0001] The present invention relates to a block copolymer, a pattern-forming composition, a method for producing a block copolymer, and a pattern-forming method.

[0002] Patent Document 1 describes the synthesis of a polystyrene-polymethyl methacrylate diblock copolymer by living anionic polymerization, and also describes that a phase-separated structure such as a lamellar structure can be self-organized by annealing the diblock copolymer.

[0003] Patent Document 2 describes a method for forming a nanostructured pattern on a substrate, the method including the steps of coating a layer of a functional material with a block copolymer of at least an A polymer chain and a B polymer chain, drying the block copolymer to form ordered nanodomains, removing the A polymer chains of the block copolymer to form voids, and removing the functional material from the locations where the A polymer chains have been removed. Patent Document 2 describes that the A polymer chains include polymethyl methacrylate or polybutadiene, and that the B polymer chains include polystyrene. It also describes that these diblock copolymers undergo directed self-assembly.

[0004] Patent Document 3 describes a block copolymer in which the first block is a polymer having a repeating structure of structural units containing a hyperbranched structure containing a silicon atom in a side chain, and the second block is a polymer having a repeating structure of structural units derived from styrene. Patent Document 3 also describes that the block copolymer forms a structure with a regular periodic structure due to phase separation, and is used in self-assembly lithography.

[0005] Patent Document 4 describes a method for producing a polymer structure having a microphase-separated structure, in which a solution is formed using a selective solvent that does not dissolve one of the polymer chains of a block copolymer only at a temperature lower than the temperature at which the polymer chain becomes soluble, and the solution is then placed in a state at a temperature lower than the temperature at which the one polymer chain becomes soluble, thereby forming a microphase-separated structure. Patent Document 4 describes the use of PS (polystyrene)-b-PMMA (polymethyl methacrylate) or the like as the block copolymer.

[0006] Non-Patent Document 1 describes the formation of nanopatterns of PS (polystyrene)-b-PMMA (polymethyl methacrylate) by epitaxial self-assembly of PS (polystyrene)-b-PMMA (polymethyl methacrylate) on a substrate on which a pattern has been formed by lithography.

[0007] Non-Patent Document 2 describes the use of self-assembly of PS (polystyrene)-b-PDMS (polydimethylsiloxane) on a substrate by solvent annealing using mixed solvent vapors for lithography.

[0008] Japanese Patent Publication No. 2001-151834 Japanese Patent Publication No. 2008-149447 Japanese Patent Publication No. 2018-141046 Japanese Patent Publication No. 2008-13678

[0009] Kim. SO et. al., "Epitaxial self-assembly of block copolymers on lithographically defined nanopatterned substrates", Nature Vol. 424, 411-414, 24 JULY 2003.Kevin W. Gotrik et. al., "Morphology Control in Block Copolymer Films Using Mixed Solvent Vapors", ACS Nano Vol.6, No. 9, 8052-8059, 2012.

[0010] In recent years, the importance of microfabrication technologies, including lithography, has increased dramatically, as exemplified by the increasing performance of computers. However, the smaller the processing dimensions in lithography, the larger and higher-quality exposure equipment is required. This requires huge investments in equipment, and there is a demand for the creation of new, simpler, and less expensive microfabrication technologies.

[0011] As a microfabrication technology that does not rely on enlargement of exposure equipment, research is being conducted on the use of microdomain structures for surface patterning and microfabrication by forming a film of a block copolymer that undergoes microphase separation on a substrate, as described in, for example, Patent Documents 1 to 4. However, the pattern sizes obtained with self-assembling materials of block copolymers are mainly 20 to 200 nm, with the smallest being around 20 nm. However, pattern sizes of around 20 nm have not yet been put to practical use, and the uniformity and regularity of the pattern shape remain issues.

[0012] The present invention has been made in view of the above problems, and an object of the present invention is to provide a novel block copolymer capable of forming a microdomain structure, and related techniques.

[0013] In order to solve the above problems, a block copolymer according to one embodiment of the present invention is a block copolymer of an adamantyl (meth)acrylate polymer in which monomer units derived from adamantyl (meth)acrylate are polymerized, and a styrene polymer in which monomer units derived from styrene are polymerized.

[0014] A pattern-forming composition according to an aspect of the present invention includes the block copolymer according to an aspect of the present invention.

[0015] Furthermore, a method for producing a block copolymer according to one aspect of the present invention includes the steps of: polymerizing adamantyl (meth)acrylate in the presence of a reversible addition-fragmentation chain transfer agent and a radical generator to obtain an adamantyl (meth)acrylate polymer; and polymerizing the adamantyl (meth)acrylate polymer and styrene in the presence of the reversible addition-fragmentation chain transfer agent and the radical generator to obtain a block copolymer of the adamantyl (meth)acrylate polymer and a styrene polymer.

[0016] Furthermore, a pattern formation method according to one aspect of the present invention includes the steps of: applying the pattern formation composition according to one aspect of the present invention onto a substrate to form a film of the block copolymer; annealing the film to cause phase separation into an adamantyl (meth)acrylate polymer phase and a styrene polymer phase in the film; and etching the phase-separated film to decompose the adamantyl (meth)acrylate polymer and form a pattern from the styrene polymer phase.

[0017] According to one aspect of the present invention, a novel block copolymer capable of forming a microdomain structure can be provided.

[0018] HAdMA homopolymer 1 obtained in Synthesis Example 1 in the Examples of the present application １ 1 is a H-NMR spectrum of HAdMA-b-PS copolymer 1 obtained in Example 1 of the present application. １ 1H-NMR spectrum of HAdMA-b-PS copolymer 2 obtained in Example 2 of the present application. １1 is a H-NMR spectrum. These are AFM images of the state after solvent annealing under various conditions using HAdMA-b-PS copolymer 1 obtained in Example 1 of the present application. These are AFM images of the state after solvent annealing under various conditions using HAdMA-b-PS copolymer 2 obtained in Example 1 of the present application. This is a graph showing the pore size distribution of a pattern formed by HAdMA-b-PS copolymer 1 obtained in Example 1 of the present application, as determined by small-angle X-ray scattering (SAXS). This is a graph showing the pore size distribution of a pattern formed by PS-b-PMMA copolymer of Comparative Example 1 of the present application, as determined by small-angle X-ray scattering (SAXS). This is a graph showing the pore size distribution of DHAdMA homopolymer 1 obtained in Synthesis Example 4 in the Examples of the present application. １ 1H-NMR spectrum of DHAdMA-b-PS copolymer 1 obtained in Example 4 of the present application. １ 1A and 1B are H-NMR spectra. These are AFM images of the state after solvent annealing using DHAdMA-b-PS copolymer 1 obtained in Example 4 of the present application, with the ratio of each mixed solvent being varied. These are AFM images of the state after solvent annealing using DHAdMA-b-PS copolymer 1 obtained in Example 4 of the present application, with the time and temperature conditions being varied. These are AFM images of the state after solvent annealing using DHAdMA-b-PS copolymer 1 obtained in Example 4 of the present application, with the time conditions being varied. These are AFM images of the state after vacuum annealing (high-temperature vacuum heating) using DHAdMA-b-PS copolymer 1 obtained in Example 4 of the present application. The pore size distribution of the microstructure determined from the AFM phase image of DHAdMA-b-PS copolymer 1 in the sample subjected to solvent annealing with a heating time of 4 hours is shown in Figure 12. 1 shows the pore size distribution of the porous structure of a sample made from DHAdMA-b-PS copolymer 1, as measured by small-angle X-ray scattering.

[0019] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively.

[0020] In addition, in this specification, "(meth)acrylic" means one or both of acrylic and methacrylic. Specifically, the term "(meth)acrylic acid" means one or both of acrylic acid and methacrylic acid, and the term "(meth)acrylate" means one or both of "acrylate" and "methacrylate."

[0021] In this specification, microphase separation refers to phase separation at a micro level or below, and also refers to phase separation in which the pore size, particle size, or phase thickness of the domains formed by phase separation are controlled at a nano level.

[0022] <Block Copolymer> A block copolymer according to one aspect of the present invention is a block copolymer of an adamantyl (meth)acrylate polymer in which monomer units derived from adamantyl (meth)acrylate are polymerized, and a styrene polymer in which monomer units derived from styrene are polymerized.

[0023] The block copolymer according to one embodiment contains an adamantyl (meth)acrylate polymer, and therefore can produce, by self-assembly, a microdomain structure pattern with a pattern size of 10 nm or less, which is difficult to achieve with conventional block copolymers in semiconductor lithography technology, where miniaturization is progressing.

[0024] Furthermore, the new block copolymer based on hydroxyadamantyl methacrylate and styrene has excellent thermal stability and easily shows good pattern shape and reproducibility in the ultrafine region. Specifically, block copolymer materials and processes utilizing self-organized pattern formation by high-temperature vacuum heating or solvent annealing methods can also be brought to the market.

[0025] The weight-average molecular weight (Mw) of the adamantyl (meth)acrylate polymer contained in the block copolymer is preferably within the range of 5,000 to 60,000, and more preferably within the range of 7,000 to 45,000. The smaller the weight-average molecular weight (Mw) of the adamantyl (meth)acrylate polymer is within the range of 5,000 to 60,000, more preferably within the range of 7,000 to 45,000, the smaller the size of the microdomain structure pattern that can be self-assembled.

[0026] The polydispersity index (PDI) of the adamantyl (meth)acrylate contained in the block copolymer is preferably in the range of 1.01 to 1.4, more preferably in the range of 1.05 to 1.25. When the polydispersity index (PDI) of the adamantyl (meth)acrylate polymer is in the range of 1.07 to 1.15, the uniformity of the microdomain structure pattern can be improved.

[0027] The adamantyl (meth)acrylate polymer contained in the block copolymer is a polymer of monomer units derived from adamantyl (meth)acrylate, and the adamantyl (meth)acrylate monomer is a hydroxyadamantyl (meth)acrylate having at least one hydroxyl group, and may have other substituents such as alkyl groups and aryl groups, as long as the effects of the present invention are not impaired.

[0028] The adamantyl (meth)acrylate polymer is preferably a polymer of monomer units derived from hydroxyadamantyl (meth)acrylate, which provides a thermally decomposable polymer chain with a high decomposition temperature while facilitating control of self-organization for forming a microdomain structure pattern with a pattern size of 10 nm or less.

[0029] The styrene polymer contained in the block copolymer is a polymer of monomer units derived from styrene, and may have other substituents such as alkyl groups, aryl groups, etc., as long as the effects of the present invention are not impaired. By containing the styrene polymer, the block copolymer exhibits the effects of increasing hydrophobicity, increasing the coefficient of restitution between blocks, and widening the difference in etching resistance between blocks.

[0030] The block copolymer may be a diblock copolymer, a triblock copolymer, a tetrablock copolymer, or a star block copolymer, but is preferably a diblock copolymer from the viewpoint of forming a microphase-separated structure of a cylindrical or lamellar structure.

[0031] The block copolymer preferably has a structure represented by the following formula (1).

[0032] In the above formula (1), R １ is selected from hydrogen and a methyl group, R ２ is selected from hydrogen, a methyl group, and an ethyl group; R ３ is selected from hydrogen and a hydroxyl group; m is an integer from 10 to 300; and n is an integer from 10 to 300.

[0033] The weight-average molecular weight (Mw) of the block copolymer is preferably within the range of 8,000 to 100,000, and more preferably within the range of 9,000 to 60,000. The weight-average molecular weight (Mw) of the block copolymer is more preferably within the range of 8,000 to 100,000, preferably 9,000 to 60,000, from the viewpoint of facilitating the formation of a fine structure due to microphase separation, and is more preferably within the range of 8,000 to 100,000, preferably 9,000 to 60,000, from the viewpoint of facilitating the formation of a self-assembled structure due to microphase separation.

[0034] The molar ratio of the adamantyl (meth)acrylate-derived monomer units to the styrene-derived monomer units contained in the block copolymer is preferably 1:4 to 1:1. Adjusting the ratio of the adamantyl (meth)acrylate polymer to the styrene polymer contained in the block copolymer can be one means for controlling the microphase-separated structure. Examples of structures that can be formed by microphase separation of a block copolymer include a sea-island structure in which the smaller of the two phases, the adamantyl (meth)acrylate polymer phase and the styrene polymer phase, forms spherical domains; a cylindrical structure in which the smaller of the two phases forms columnar domains; and a lamellar structure in which the two phases each form sheet-like domains that are alternately stacked. A lamellar structure can be obtained, for example, by adjusting the ratio of the adamantyl (meth)acrylate polymer to the styrene polymer contained in the block copolymer to approach 1:1.

[0035] The block copolymer containing an adamantyl (meth)acrylate polymer and a styrene polymer can control the particle size of the spherical domains, the pore size of the cylindrical structure, the thickness or width of the sheet-like domain phase, or the line width of the pattern to 20 nm or less.

[0036] <Method for Producing Block Copolymers> The block copolymers may be produced by reversible addition-fragmentation chain transfer polymerization (RAFT). By employing the reversible addition-fragmentation chain transfer polymerization (RAFT) method, a novel block copolymer containing an adamantyl (meth)acrylate polymer can be precisely synthesized using adamantyl (meth)acrylate, which has large steric hindrance and a large difference in polarity from styrene.

[0037] The synthesis of the block copolymer includes (1) a step of synthesizing an adamantyl (meth)acrylate polymer by polymerizing adamantyl (meth)acrylate in the presence of a reversible addition-fragmentation chain transfer agent (RAFT agent) and a polymerization initiator, and a step of synthesizing a block copolymer of an adamantyl (meth)acrylate polymer and a styrene polymer by polymerizing the adamantyl (meth)acrylate polymer and styrene in the presence of the RAFT agent and a polymerization initiator.

[0038] Examples of RAFT agents include 2-cyano-2-propyl benzothioate, 2-cyano-2-propyl dodecyl trithiocarbonate, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, 2-cyano-2-propyl dodecyl trithiocarbonate, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid, etc. The amount of the RAFT agent added may be about 1 to 3 parts by weight, based on 100 parts by weight of the amount of monomers to be polymerized.

[0039] Examples of the radical generator include azo compounds such as azobisisobutyronitrile, azobis(2-methylbutyronitrile), and 2,2'-azobis-2,4-dimethylvaleronitrile, and organic peroxides. Examples of the organic peroxides include, but are not limited to, ketone peroxides such as methyl ethyl ketone peroxide, peroxyketals, hydroperoxides, dialkyl peroxides, etc. The amount of the radical generator to be added may be about 0.1 to 2.0 parts by weight, based on 100 parts by weight of the amount of the monomers to be polymerized.

[0040] Examples of solvents (reaction solvents) used in the synthesis of the block copolymer include, but are not limited to, ethers such as dioxane and tetrahydrofuran (THF), ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and polar solvents such as dimethyl sulfoxide (DMSO) and dimethylformamide (DMF).

[0041] Other examples of the refining solvent used in purifying the block copolymer include alcohols such as methanol, ketones such as acetone, and hydrocarbons such as hexane, and two or more of these may be used in combination.

[0042] <Pattern-forming composition> As described above, the block copolymer is a block copolymer of an adamantyl (meth)acrylate polymer and a styrene polymer, and therefore a microdomain structure pattern having a pattern size of 10 nm or less can be produced by self-assembly. Therefore, a pattern-forming composition containing the block copolymer according to one embodiment of the present invention is also within the scope of the present invention.

[0043] The pattern-forming composition contains a block copolymer of an adamantyl (meth)acrylate polymer and a styrene polymer, and may further contain a diluting solvent and other additives.

[0044] The dilution solvent contained in the pattern-forming composition may be selected from the reaction solvents and purification solvents explained in the production of the block copolymer described above, and is not limited thereto. Preferred examples include ethers such as anisole, esters such as ethyl lactate, and alcohols such as 2-butyl alcohol.

[0045] Although not limited, the content of the block copolymer contained in the pattern-forming composition may be within the range of 0.5 to 3.0% by weight.

[0046] The pattern-forming composition may contain other additives such as plasticizers, antioxidants, photodegradation inhibitors, and metal salts, as long as the effects of the present invention are not impaired.

[0047] The pattern-forming composition may also contain, for example, a crosslinking agent, a photoacid generator, a radical generator, and the like, within the scope of not impairing the effects of the present invention.

[0048] <Pattern Forming Method> A pattern forming method according to one aspect of the present invention includes the steps of: applying a pattern forming composition containing a block copolymer of an adamantyl (meth)acrylate polymer and a styrene polymer onto a substrate to form a film of the block copolymer; solvent annealing the film to cause phase separation (microphase separation) into an adamantyl (meth)acrylate polymer phase and a styrene polymer phase in the film; and heating the phase-separated film to decompose the adamantyl (meth)acrylate polymer, thereby forming a pattern from the styrene polymer phase.

[0049] The pattern forming method according to one aspect may further include a step of transferring the pattern to the substrate by etching the substrate on which the pattern has been formed.

[0050] Examples of substrates that can be used in the pattern forming method include silicon wafers, glass substrates, ITO substrates, quartz substrates, and flexible substrates.

[0051] (Step of forming a block copolymer film) In the step of forming a block copolymer film, a pattern-forming composition containing the block copolymer according to one embodiment of the present invention is applied onto a substrate to form a block copolymer film on the substrate.

[0052] Examples of the coating method for the pattern-forming composition include known coating methods such as spin coating, slit coating, and spray coating, and spin coating is preferred. The substrate coated with the pattern-forming composition may be heated and dried before being subjected to annealing, which will be described later, to remove the solvent contained in the pattern-forming composition from the film of the block copolymer.

[0053] (Phase Separation Step) In the phase separation step, the block copolymer film is annealed to separate the film into an adamantyl (meth)acrylate polymer phase and a styrene polymer phase. Phase separation between the adamantyl (meth)acrylate polymer phase and the styrene polymer phase can be achieved on the order of nanometers.

[0054] Annealing may be performed by high temperature vacuum heating or solvent annealing.

[0055] When phase separation is carried out by high-temperature vacuum heating, the substrate on which the block copolymer film has been formed may be heated, for example, at a heating temperature of 180 to 260° C. and a vacuum pressure of 0.01 to 0.10 kPa.

[0056] When the phase separation is carried out by a solvent annealing method, the substrate on which the block copolymer film has been formed may be heated at a temperature of 20 to 240° C., for example, so as to expose the block copolymer film to the vapor of a mixed solvent shown below.

[0057] The combination of solvents used in solvent annealing may be a combination of a good solvent or a poor solvent, and may be appropriately selected from, for example, hydrocarbon solvents such as hexane, chlorine-based solvents such as chloroform, ethers such as tetrahydrofuran, alcohols such as methanol, ethers such as tetrahydrofuran, and water. More specifically, the combination of solvents used in solvent annealing may be, for example, a combination of hexane and methanol, a combination of tetrahydrofuran and methanol, a combination of chloroform and methanol, a combination of water and methanol, or a combination of water and THF, but is not limited thereto, and THF alone may be used as the solvent for solvent annealing.

[0058] The composition ratio of the solvents used in the solvent annealing is preferably, for example, 0:100 to 100:0, which allows for more suitable control of the microphase-separated structure.

[0059] As described above, structures obtained by phase separation include an island-sea structure forming spherical domains, a cylindrical structure forming columnar domains, a lamellar structure in which sheet-like domains are alternately stacked, and a random micellar structure. These structures can be controlled by the molar ratio of each monomer unit constituting each block in the block copolymer and the annealing conditions.

[0060] (Pattern Forming Step) In the pattern forming step, a structure such as a sea-island structure forming spherical domains, a cylindrical structure forming columnar domains, or a lamellar structure formed from an adamantyl (meth)acrylate polymer phase and a styrene polymer phase may be formed by thermally decomposing the adamantyl (meth)acrylate polymer phase, thereby forming a pattern based on these structures in the styrene polymer phase.

[0061] The pattern formation step may be carried out, for example, by heating the adamantyl (meth)acrylate polymer phase at a temperature higher than the glass transition temperature of the adamantyl (meth)acrylate polymer. Furthermore, in the pattern formation step, the annealed block copolymer film may be irradiated with an electron beam before thermally decomposing the adamantyl (meth)acrylate polymer to lower the glass transition temperature of the adamantyl (meth)acrylate polymer.

[0062] Furthermore, the step of forming a pattern may involve decomposing the adamantyl (meth)acrylate polymer by dry etching, for example, in the same manner as in the transfer of a pattern to a substrate by etching, which will be described later.

[0063] (Step of Transferring a Pattern to a Substrate) The step of transferring a pattern to a substrate includes a step of etching the substrate on which the pattern made of the styrene polymer phase has been formed, thereby transferring the pattern to the substrate.

[0064] The transfer of the pattern to the substrate by etching may be carried out by, for example, dry etching. As the etchant (etching agent), a known etchant may be used, for example, C ２ F ６ It is preferable to use fluorine gas such as the following.

[0065] A metal or metal oxide layer can be formed on the substrate on which the pattern has been formed, following the pattern, and then the styrene polymer layer can be removed from the substrate by, for example, stripping with a stripping solvent and ashing.

[0066] <Pattern Forming Method According to Other Aspects> The pattern forming method according to one aspect of the present invention is not limited to the above aspect. For example, the pattern forming method according to one aspect may include a step of forming a predetermined pattern as a first pattern on a substrate by lithography before the step of forming a film of a block copolymer of an adamantyl (meth)acrylate polymer and a styrene polymer. In this case, after the formation of the first pattern, the pattern formed by the styrene polymer phase can be referred to as a second pattern.

[0067] (Step of forming first pattern) In the step of forming the first pattern, a film of an organosilane compound is formed on a substrate, a resist film is formed on the film of the organosilane compound, and a predetermined pattern is formed in the resist film using a photomask.

[0068] The coating of the organosilane compound is preferably a monomolecular layer of the organosilane compound, and may be formed by applying a solution of the organosilane compound onto a substrate, for example, by a CVD method, an ALD method, etc. The organosilane compound may be, for example, a silane compound such as phenylethyltrichlorosilane, or a polysilane compound such as poly(methylphenylsilane) or poly(diphenylsilane).

[0069] The resist film formed on the film of the organosilane compound is not limited, and may be formed using a known radically polymerizable or cationic polymerizable positive or negative photoresist agent. The exposure of the resist film may be appropriately determined depending on the type of photoresist agent and the desired pattern. After the desired pattern is developed on the resist film by exposure, for example, O ２ By etching, a resist film pattern may be formed on the organic silane compound film formed on the substrate.

[0070] Thereafter, by carrying out the steps from forming a film of the block copolymer to transferring the pattern onto the substrate, a desired fine pattern based on the first pattern can be formed on the substrate.

[0071] [Summary] The block copolymer according to aspect [1] of the present invention is a block copolymer containing an adamantyl (meth)acrylate polymer in which monomer units derived from adamantyl (meth)acrylate are polymerized, and a styrene polymer in which monomer units derived from styrene are polymerized.

[0072] In addition, in the block copolymer according to aspect [2] of the present invention, in the above aspect [1], it is preferable that the weight average molecular weight (Mw) of the adamantyl (meth)acrylate polymer is in the range of 5,000 to 60,000.

[0073] In addition, in the block copolymer according to aspect [3] of the present invention, in the above aspect [1] or [2], it is preferable that the polydispersity index (PDI) of the adamantyl (meth)acrylate polymer is in the range of 1.05 to 1.25.

[0074] In addition, the block copolymer according to aspect [4] of the present invention is preferably the block copolymer according to any one of the above aspects [1] to [3], wherein the weight average molecular weight (Mw) of the block copolymer is in the range of 8,000 to 100,000.

[0075] In addition, in the block copolymer according to aspect [5] of the present invention, in any one of the above aspects [1] to [4], the ratio of the adamantyl (meth)acrylate polymer to the styrene polymer contained in the block copolymer is preferably 1:4 to 1:1.

[0076] The block copolymer according to aspect [6] of the present invention, in any one of the above aspects [1] to [5], preferably has a structure represented by the following formula (1):

[0077] In the above formula (1), R １ is selected from hydrogen and a methyl group, R ２ is selected from hydrogen, a methyl group, and an ethyl group; R ３ is selected from hydrogen and a hydroxyl group; m is an integer from 10 to 300; and n is an integer from 10 to 300.

[0078] The pattern-forming composition according to the seventh aspect of the present invention may contain the block copolymer according to any one of the first to sixth aspects.

[0079] A method for producing a block copolymer according to aspect [8] of the present invention includes the steps of: polymerizing adamantyl (meth)acrylate in the presence of a reversible addition-fragmentation chain transfer agent and a radical generator to obtain an adamantyl (meth)acrylate polymer; and polymerizing the adamantyl (meth)acrylate polymer and styrene in the presence of the reversible addition-fragmentation chain transfer agent and the radical generator to obtain a block copolymer of the adamantyl (meth)acrylate polymer and a styrene polymer.

[0080] In the method for producing a block copolymer according to aspect [9] of the present invention, in the above aspect [8], the reversible addition-fragmentation chain transfer agent is preferably selected from 2-cyano-2-propyl benzothioate, 2-cyano-2-propyl dodecyl trithiocarbonate, and 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid.

[0081] A pattern formation method according to aspect

[10] of the present invention includes the steps of: applying the pattern formation composition of aspect [7] above onto a substrate to form a film of the block copolymer; annealing the film to cause phase separation into an adamantyl (meth)acrylate polymer phase and a styrene polymer phase in the film; and heating or etching the phase-separated film to decompose the adamantyl (meth)acrylate polymer and form a pattern with the styrene polymer phase.

[0082] The pattern forming method according to aspect

[11] of the present invention may be the above-mentioned aspect

[10] , further comprising the step of transferring the pattern to the substrate by etching the substrate on which the pattern has been formed.

[0083] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0084] An example of the present invention is described below. [1] Synthesis of AdMA Homopolymer [1-1] Synthesis of HAdMA Homopolymer (Synthesis Example 1) A reaction solution was prepared by adding 2.4 g of 3-hydroxy-1-methacryloyloxyadamantane (HAdMA), 45 mg of 2-cyano-2-propylbenzothioate (CPDB) as a RAFT agent, and 4 mg of AIBN as a polymerization initiator to 4.8 ml of 1,4-dioxane. The reaction solution was degassed with argon for 15 minutes and then stirred at 60°C for 18 hours to produce a crude product. The crude product was purified with acetone and dried under vacuum to produce HAdMA homopolymer 1 as a purified pink powder.

[0085]

[0086] (Synthesis Example 2) 2.4 g of 3-hydroxy-1-methacryloyloxyadamantane (HAdMA), 23 mg of 2-cyano-2-propylbenzothioate (CPDB) as a RAFT agent, and 2.2 mg of AIBN as a polymerization initiator were added to 4.8 ml of 1,4-dioxane to prepare a reaction solution. After degassing the reaction solution with argon for 15 minutes, the solution was stirred at 60° C. for 18 hours to react and obtain a crude product. The obtained crude product was purified with acetone and dried under vacuum to obtain HAdMA homopolymer 2 as a purified pink powder.

[0087] (Synthesis Example 3) 2.4 g of 3-hydroxy-1-methacryloyloxyadamantane (HAdMA), 15 mg of 2-cyano-2-propylbenzothioate (CPDB) as a RAFT agent, and 1.2 mg of AIBN as a polymerization initiator were added to 4.8 ml of 1,4-dioxane to prepare a reaction solution. This reaction solution was degassed with argon for 15 minutes and then stirred at 60° C. for 18 hours to react and obtain a crude product. The obtained crude product was purified with acetone and dried under vacuum to obtain HAdMA homopolymer 3 as a purified pink powder.

[0088] [1-2] Synthesis of DHAdMA homopolymer (Synthesis Example 4) 2.4 g of 3,5-dihydroxy-1-methacryloyloxyadamantane (DHAdMA), 21 mg of 2-cyano-2-propylbenzothioate (CPDB) as a RAFT agent, and 1.8 mg of AIBN as a polymerization initiator were added to 2.7 ml of dimethyl sulfoxide (DMSO) to prepare a reaction solution. After degassing the reaction solution with argon for 15 minutes, the solution was stirred at 60°C for 16 hours to react and obtain a crude product. The obtained crude product was purified with acetone and dried under vacuum to obtain DHAdMA homopolymer 1 as a purified pink powder.

[0089]

[0090] [1-3] １ H-NMR analysis (400 Hz, DMSO-d6) of HAdMA homopolymer 1 obtained in Synthesis Example 1. １ 1 shows the H-NMR spectrum, along with the relationship between each hydrogen atom and each signal in HAdMA homopolymer 1. Similarly, spectra similar to that of HAdMA homopolymer 1 were obtained for HAdMA homopolymer 2 and HAdMA homopolymer 3.

[0091] FIG. 8 shows the DHAdMA homopolymer 1 obtained in Synthesis Example 4. １ 1 is a H-NMR spectrum showing the relationship between each hydrogen atom and each signal in DHAdMA homopolymer 1.

[0092] The aromatic ring of the RAFT agent 2-cyano-2-propylbenzothioate (CPDB) １ The degree of polymerization n of HAdMA was calculated from the integral value of the spectrum of the hydroxyl group of HAdMA obtained by setting the integral value of the H-NMR spectrum to 5.00. １ The integral value of the H-NMR spectrum was set to 5.00, and the degree of polymerization n of DHAdMA was calculated from the integral value of the hydroxyl group spectrum. Table 1 shows the degrees of polymerization of HAdMA homopolymers 1 to 3 and DHAdMA homopolymer 1.

[0093]

[0094] [1-4] Gel Permeation Chromatography (GPC) Analysis GPC measurement was performed on each of HAdMA homopolymers 1 to 3 and DHAdMA homopolymer 1 under the following measurement conditions. From the results, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in terms of polystyrene were measured, and the polydispersity (Mw / Mn) was evaluated. GPC measurement apparatus: Waters system (Model No. 717, 1515, 2412, 2489) manufactured by Waters Corporation Column: Guard Column WAT054405 x 1 (manufactured by Waters Corporation) Syragel HT-6E x 1 (manufactured by Waters Corporation) Syragel HT-3 x 1 (manufactured by Waters Corporation) Column temperature: 25°C Detector: RI (differential refractive index detector) Solvent: tetrahydrofuran (THF) Flow rate: 1 mL / min Standard polystyrene: Standard SM-105 (Shodex)

[0095] Table 2 below shows the number average molecular weight (Mw), weight average molecular weight (Mw), and polydispersity index (PDI) of the HAdMA homopolymers as determined by GPC analysis.

[0096]

[0097] [1-5] Simultaneous thermogravimetry-differential thermal analysis (TG-DTA) The decomposition temperatures of HAdMA homopolymer 1 and DHAdMA homopolymer 1 were evaluated by simultaneous thermogravimetry-differential thermal analysis under the following conditions: Analysis start temperature: 235°C Analysis end temperature: 700°C Heating rate: 10°C / min Table 3 below shows the weight loss rates and decomposition temperatures of HAdMA homopolymer 1 and DHAdMA homopolymer 1.

[0098]

[0099] [2] Synthesis of AdMA-b-PS Copolymer [2-1] Synthesis of HAdMA-b-PS Copolymer (Example 1) A reaction solution was prepared by adding 0.42 g of HAdMA homopolymer 1, 0.42 g of styrene, and 4 mg of the polymerization initiator AIBN to 1.3 ml of 1,4-dioxane. The solution was degassed with argon for 15 minutes and then stirred at 60°C for 16 hours to react and obtain a crude product. The obtained crude product was purified with acetone and dried in vacuo to obtain a pink powder of HAdMA-b-PS copolymer 1 as a purified product.

[0100]

[0101] Example 2 A reaction solution was prepared by adding 0.5 g of HAdMA homopolymer 1, 0.3 g of styrene, and 1.2 mg of AIBN as a polymerization initiator to 2 ml of 1,4-dioxane. The reaction solution was degassed with argon for 15 minutes and then stirred at 60°C for 15 hours to react and obtain a crude product. The obtained crude product was purified with acetone and dried under vacuum to obtain a pink powder of HAdMA-b-PS copolymer 2 as a purified product.

[0102] Example 3 A reaction solution was prepared by adding 0.5 g of HAdMA homopolymer 2, 0.68 g of styrene, and 2.3 mg of the polymerization initiator AIBN to 15 ml of 1,4-dioxane. The reaction solution was degassed with argon for 15 minutes and then stirred at 60°C for 16 hours to obtain a crude product. The crude product was purified with acetone and dried under vacuum to obtain a pink powder of HAdMA-b-PS copolymer 3.

[0103] [2-2] Synthesis of DHAdMA-b-PS Copolymer (Example 4) 0.5 g of DHAdMA homopolymer 1, 0.72 g of styrene, and 2.3 mg of the polymerization initiator AIBN were added to 9.1 ml of dimethyl sulfoxide (DMSO) to prepare a reaction solution. The reaction solution was degassed with argon for 15 minutes and then stirred at 60°C for 16 hours to allow the reaction to proceed, yielding a crude product. The resulting crude product was purified with acetone and dried under vacuum to yield DHAdMA-b-PS copolymer 1 as a purified pink powder.

[0104]

[0105] HAdMA-b-PS copolymers 1 to 3 and DHAdMA-b-PS copolymer 1 １ The product was analyzed by H-NMR and GPC.

[0106] [2-3] １ H-NMR analysis of HAdMA-b-PS copolymer 1 in Example 1. １ 2 shows the H-NMR spectrum of HAdMA-b-PS copolymer 1. The relationship between each hydrogen atom and each peak in HAdMA-b-PS copolymer 1 is also shown in FIG.

[0107] FIG. 3 shows the HAdMA-b-PS copolymer 2 of Example 2. １ The H-NMR spectrum is shown in Figure 3. The relationship between each hydrogen atom and each peak in HAdMA-b-PS copolymer 2 is also shown. Similarly, a spectrum similar to that of HAdMA-b-PS copolymers 1 and 2 was obtained for HAdMA-b-PS copolymer 3. The protons bonded to the aromatic ring of styrene were １The integral ratio of the integral of the hydroxyl group protons in HAdMA, assuming an integral value of 5.00 in the H-NMR spectrum, was calculated, and the component ratio (molar ratio) of the monomer units derived from HAdMA to the monomer units derived from styrene was determined from this component ratio (molar ratio). Furthermore, the degree of polymerization of the styrene monomer units in HAdMA-b-PS copolymers 1 and 2 was calculated from this component ratio (molar ratio) and the degree of polymerization of HAdMA shown in Table 1 above. Table 4 below shows the degree of polymerization m of styrene, which is calculated from the component ratio (molar ratio) of the monomer units derived from HAdMA to the monomer units derived from styrene and the degree of polymerization n of HAdMA.

[0108] FIG. 9 shows the DHAdMA-b-PS copolymer 1 of Example 4. １ 9 shows the H-NMR spectrum. The relationship between each hydrogen atom and each peak in DHAdMA-b-PS copolymer 1 is also shown. In DHAdMA-b-PS copolymer 1, the protons bonded to the aromatic ring of styrene also bond. １ The integral ratio of the integral of the hydroxyl protons of DHAdMA, assuming an integral value of 5.00 in the H-NMR spectrum, was calculated, and the component ratio (molar ratio) of the monomer units derived from DHAdMA to the monomer units derived from styrene was calculated from this component ratio (molar ratio). Furthermore, the degree of polymerization of the styrene monomer units in DHAdMA-b-PS copolymer 1 was calculated from this component ratio (molar ratio) and the degree of polymerization of DHAdMA shown in Table 1 above. Table 4 below shows the component ratio (molar ratio) of the monomer units derived from DHAdMA to the monomer units derived from styrene, and the degree of polymerization (n) of DHAdMA, which can be calculated from this.

[0109]

[0110] [2-4] Gel Permeation Chromatography (GPC) Analysis GPC analysis of the HAdMA-b-PS copolymer and DHAdMA-b-PS copolymer was carried out under the same conditions as those for the HAdMA homopolymer obtained in each Synthesis Example. Table 5 below shows the number-average molecular weight (Mw), weight-average molecular weight (Mw), and polydispersity index (PDI) of the HAdMA-b-PS copolymer and DHAdMA-b-PS copolymer determined by GPC analysis.

[0111] [2-5] Simultaneous Thermogravimetry-Differential Thermal Analysis (TG-DTA) TG-DTA analysis of HAdMA-b-PS copolymer 1 and DHAdMA-b-PS copolymer 1 was carried out under the same conditions as those for the TG-DTA analysis of the homopolymers obtained in each Synthesis Example. Table 6 below shows the weight loss rates and decomposition temperatures of HAdMA-b-PS copolymer 1 and DHAdMA-b-PS copolymer 1.

[0112] From the evaluation results of the weight loss rate and decomposition temperature by TG-DTA analysis shown in Table 6, it can be confirmed that the HAdMA or DHAdMA block is decomposed in HAdMA-b-PS copolymer 1 and DHAdMA-b-PS copolymer 1.

[0113] [3] Evaluation of Solvent Annealing Using HAdMA-b-PS copolymer 1 of Example 1, HAdMA-b-PS copolymer 2 of Example 2, and DHAdMA-b-PS copolymer 1, pattern control by solvent annealing was evaluated.

[0114] (Sample Preparation 1) HAdMA-b-PS copolymers 1 and 2 were each dissolved individually in a mixed solvent consisting of anisole, ethyl lactate, and 2-butyl alcohol to prepare 1 wt % solutions. The prepared solutions were spin-coated onto a silicon wafer to a film thickness of approximately 10 nm, and then heated at 150°C for 1 minute using a hot plate. In this way, Sample 1, in which HAdMA-b-PS copolymer 1 was coated on a silicon wafer, and Sample 2, in which HAdMA-b-PS copolymer 2 was coated on a silicon wafer, were prepared.

[0115] (Sample Preparation 2) DHAdMA-b-PS copolymer 1 was dissolved in a mixed solvent of methanol and toluene to prepare a 1 wt % solution. The prepared solution was spin-coated onto a silicon wafer to a film thickness of approximately 20 nm, and the wafer was heated at 150°C for 1 minute using a hot plate. In this way, Sample 3 was prepared, in which DHAdMA-b-PS copolymer 1 was coated on a silicon wafer.

[0116] (Solvent Annealing-1) For Samples 1 and 2, a combined use of hexane and methanol was used and evaluated under the following conditions. The mixture ratio of hexane and methanol was adjusted using a Research Plus V, and 1 ml of the mixture was sealed in a 100 ml container and subjected to solvent annealing. Heating temperature: 23°C Condition: 1 atm

[0117] Figure 4 shows AFM images of Sample 1 using HAdMA-b-PS copolymer 1 after solvent annealing under various conditions. The top images in Figure 4 show the evaluation results after 25 minutes of solvent annealing, and the bottom images show the evaluation results after 2 hours and 25 minutes of solvent annealing. The top and bottom images in Figure 4 show, from left to right, the evaluation results of solvent annealing under conditions where the methanol:hexane ratio was 40:60, 75:25, 80:20, and 85:15.

[0118] Comparing the evaluation results for 25 minutes of solvent annealing shown in the upper row of Figure 4 with the evaluation results for 2 hours and 25 minutes shown in the lower row of Figure 4, it can be seen that by extending the solvent annealing time, a finer and denser porous pattern is formed. Furthermore, the first AFM image from the left in the lower row of Figure 4 confirms that a particularly dense and deep porous structure was formed after 2 hours and 25 minutes of solvent annealing at a methanol:hexane ratio of 85:15. Furthermore, it is believed that this material can be used for applications requiring fine processing of 10 nm or less, such as semiconductor processing.

[0119] Figure 5 shows AFM images of Sample 2 using HAdMA-b-PS copolymer 2 after solvent annealing under various conditions. The top images in Figure 5 show the evaluation results after 25 minutes of solvent annealing, and the bottom images show the evaluation results after 2 hours and 25 minutes of solvent annealing. The top and bottom images in Figure 5 show, from left to right, the evaluation results of solvent annealing under conditions where the methanol:hexane ratio was 20:80, 40:60, 60:40, and 80:20.

[0120] As shown in FIG. 5, HAdMA-b-PS copolymer 2 synthesized using HAdMA homopolymer 2 exhibited self-assembly of a micellar structure exhibiting a random pattern.

[0121] (Solvent Annealing-2(1)) For the solvent annealing of Sample 3, a combination of tetrahydrofuran (THF) and methanol was used and evaluated under the following conditions. The mixing ratio of tetrahydrofuran (THF) and methanol was adjusted using a Research Plus V, and 1 ml of the mixture was sealed in a 100 ml container and subjected to solvent annealing. Heating temperature: 23°C Condition: 1 atm

[0122] Figure 10 shows AFM images of the state after solvent annealing under various conditions for Sample 3 using DHAdMA-b-PS copolymer 1. Of the images in Figure 10, the top row shows the evaluation results of the topography image after solvent annealing, and the bottom row shows the evaluation results of the phase image after solvent annealing, at 2 hours and 25 minutes. The top and bottom images in Figure 10 show, from left to right, the evaluation results of solvent annealing under conditions where the methanol:THF ratio was 20:80, 40:60, 60:40, and 80:20.

[0123] Comparing the evaluation results after 25 minutes of solvent annealing (shown in the upper panel of Figure 10) with those after 2 hours and 25 minutes (shown in the lower panel of Figure 10), it can be seen that, like the HAdMA-b-PS copolymer, a finer and denser porous pattern is formed with the DHAdMA-b-PS copolymer by extending the solvent annealing time. Furthermore, the first AFM image from the left in the lower panel of Figure 10 confirms that a dense and deep porous structure is formed after 2 hours and 25 minutes of solvent annealing at a methanol:THF ratio of 40:60 to 80:20, preferably 40:60. This suggests that the DHAdMA-b-PS copolymer can be used for applications requiring fine processing of 10 nm or less, such as semiconductor processing.

[0124] (Solvent Annealing-2(2)) A plurality of samples 4 were prepared under the same conditions as sample 3 using DHAdMA-b-PS copolymer 1, except that the thickness was changed from 20 nm to 30 nm, and solvent annealing was performed on each of the samples 4. A combined system of tetrahydrofuran (THF) and methanol was used as the mixed solvent, and solvent annealing was performed at a heating temperature of 23°C for 24 hours.

[0125] Figure 11 shows AFM images of Sample 4 using DHAdMA-b-PS copolymer 1 after solvent annealing under various conditions. The top and bottom images in Figure 11 show the evaluation results of the topography image after solvent annealing, and the bottom images show the evaluation results of the phase image after solvent annealing, at 24 hours. The top and bottom images in Figure 11 show, from left to right, the evaluation results of solvent annealing under conditions where the methanol:THF ratio was 40:60, 30:70, 20:80, and 10:90. The top right images in the bottom row of Figure 11 for the 40% to 20% AFM images are FFT-processed versions of the images. The small windows in the bottom left of the 40% to 20% AFM images are enlarged views.

[0126] (Solvent Annealing-2(3)) Using DHAdMA-b-PS copolymer 1, a 30 nm thick sample was prepared under the same conditions as Sample 3 except for the film thickness, and evaluation was performed by changing the solvent annealing time and temperature. The mixed solvent used in the solvent annealing was set at a methanol:THF ratio of 40:60.

[0127] Figure 12 is an AFM image of the state after solvent annealing in a sample prepared under the same conditions as sample 3 using DHAdMA-b-PS copolymer 1. In Figure 12, the upper and lower rows show, from left to right, the evaluation results of solvent annealing under the conditions of 23 ° C, 2 hours and 25 minutes, 23 ° C, 4 hours, 23 ° C, 3 days, and 50 ° C, 1 hour heating. Of the images in Figure 12, the upper row shows the evaluation results of the shape image in solvent annealing, and the lower row shows the evaluation results of the phase image in solvent annealing. Note that the upper right image in each of the AFM images on the left side from the 4-hour condition in the lower row of Figure 12 is a figure obtained by FFT processing of each figure, and the small window drawing in the lower left of the AFM image is an enlarged view.

[0128] (Vacuum Annealing (High-Temperature Vacuum Heating)) A sample with a thickness of 30 nm was prepared by coating DHAdMA-b-PS copolymer 1 on a silicon wafer under the same conditions as sample 3 for solvent annealing except for the film thickness, and vacuum annealing was carried out at 26.3 kPa.

[0129] FIG. 13 shows AFM images of sample 3 using DHAdMA-b-PS copolymer 1 taken before and after vacuum annealing under various conditions. Of the images in FIG. 13, the top row shows the evaluation results of the shape images at 0 and 24 hours after vacuum annealing, and the bottom row shows the evaluation results of the phase images at 0 and 24 hours after vacuum annealing. In addition, in both the top and bottom images of FIG. 13, the left side shows the evaluation results of vacuum annealing without heat treatment, and the right side shows the evaluation results of vacuum annealing with heating at 200°C for 24 hours. Furthermore, from the AFM image in FIG. 13, it can be confirmed that a dense and deep porous structure was formed even after vacuum annealing, and it is believed that the sample can be used for applications requiring fine processing of 10 nm or less, such as semiconductor processing or templates that are durable up to high temperatures.

[0130] [4] Small-Angle X-Ray Scattering (SAXS) Test (Evaluation of HAdMA-b-PS Copolymer 1) The pore sizes of the porous structures formed by HAdMA-b-PS Copolymer 1 and a PS-b-PMMA (polystyrene-b-poly(methyl methacrylate)) block copolymer as a comparative example were evaluated by a small-angle X-ray scattering test.

[0131] HAdMA-b-PS copolymer 1 and PS-b-PMMA (polystyrene-b-poly(methyl methacrylate)) copolymer were individually dissolved in THF to a concentration of 5 wt %, and the solutions were air-dried to obtain samples of HAdMA-b-PS copolymer 1 and PS-b-PMMA (polystyrene-b-poly(methyl methacrylate)) copolymer. The pore size distributions of the porous structures formed by these copolymer samples were evaluated by small-angle X-ray scattering.

[0132] The conditions for the small-angle X-ray scattering test are as follows: NANO-Viewer device (manufactured by RIGAKU Corporation)

[0133] Figure 6 shows the pore size distribution of the microstructure formed by HAdMA-b-PS copolymer 1, as determined by small-angle X-ray scattering (SAXS), and Figure 7 shows the pore size distribution of the microstructure formed by PS-b-PMMA (polystyrene-b-poly(methyl methacrylate)) copolymer, as determined by small-angle X-ray scattering (SAXS). The small-angle X-ray scattering (SAXS) evaluation results in Figures 6 and 7 confirm that a microdomain structure with a pattern size of 10 nm or less is formed by self-assembly in HAdMA-b-PS copolymer 1. (Evaluation of DHAdMA-b-PS Copolymer 1) The pore size of the porous structure formed by DHAdMA-b-PS copolymer 1 was evaluated by small-angle X-ray scattering.

[0134] Figure 14 shows the pore size distribution of the microstructure obtained by FFT processing of the AFM image of DHAdMA-b-PS copolymer 1 in the sample that was solvent annealed for 4 hours after heating as shown in Figure 12. As shown in Figure 14, the microstructure formed by DHAdMA-b-PS copolymer 1 was confirmed to have a pore size of 32 nm and a deep microstructure.

[0135] A sample was prepared by dissolving DHAdMA-b-PS copolymer 1 in THF to a concentration of 5 wt % and then air-drying it. Figure 15 shows the pore size distribution of the porous structure of the sample prepared from DHAdMA-b-PS copolymer 1, measured by small-angle X-ray scattering.

[0136] From the evaluation results of the small angle X-ray scattering (SAXS) test shown in FIG. 15, it can be confirmed that a microdomain structure with a pattern size of 26 nm or less is formed by self-organization in DHAdMA-b-PS copolymer 1.

[0137] The present invention can be used, for example, as a material that can form highly regular nano-level fine patterns on a substrate.

Claims

1. A block copolymer of an adamantyl (meth)acrylate polymer in which monomer units derived from adamantyl (meth)acrylate are polymerized, and a styrene polymer in which monomer units derived from styrene are polymerized.

2. The block copolymer according to claim 1, wherein the weight average molecular weight (Mw) of the adamantyl (meth)acrylate polymer is in the range of 5,000 to 60,000.

3. The block copolymer of claim 1, wherein the polydispersity index (PDI) of the adamantyl (meth)acrylate polymer is in the range of 1.05 to 1.

25.

4. The block copolymer according to claim 1, wherein the weight average molecular weight (Mw) of the block copolymer is in the range of 8,000 to 100,000.

5. The block copolymer according to claim 1, wherein the molar ratio of the monomer units derived from adamantyl (meth)acrylate to the monomer units derived from styrene contained in the block copolymer is 1:4 to 1:

1.

6. Having a structure represented by the following formula (1): In the above formula (1), R １ is selected from hydrogen and a methyl group, R ２ is selected from hydrogen, a methyl group, and an ethyl group; R ３ is selected from hydrogen and a hydroxyl group; m is an integer from 10 to 300; and n is an integer from 10 to 300.

7. A pattern-forming composition comprising the block copolymer according to any one of claims 1 to 6.

8. A method for producing a block copolymer, comprising: a step of polymerizing adamantyl (meth)acrylate in the presence of a reversible addition-fragmentation chain transfer agent and a radical generator to obtain an adamantyl (meth)acrylate polymer; and a step of polymerizing the adamantyl (meth)acrylate polymer and styrene in the presence of the reversible addition-fragmentation chain transfer agent and the radical generator to obtain a block copolymer of the adamantyl (meth)acrylate polymer and a styrene polymer.

9. The method for producing a block copolymer according to claim 8, wherein the reversible addition-fragmentation chain transfer agent is selected from the group consisting of 2-cyano-2-propyl benzothioate, 2-cyano-2-propyl dodecyl trithiocarbonate, and 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid.

10. A pattern formation method comprising the steps of: applying the pattern formation composition according to claim 7 onto a substrate to form a film of the block copolymer; annealing the film to separate the film into an adamantyl (meth)acrylate polymer phase and a styrene polymer phase; and etching the phase-separated film to decompose the adamantyl (meth)acrylate polymer and form a pattern from the styrene polymer phase.

11. The pattern forming method according to claim 10, further comprising the step of transferring the pattern to the substrate by etching the substrate on which the pattern has been formed.

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