WO2022049968A1 - Self-organizing film-forming composition, and method for forming pattern - Google Patents

Abstract

Provided are: a self-organizing film-forming composition capable of forming a self-organizing film having few coating defects; and a method for forming a pattern. This self-organizing film-forming composition contains a solvent and a first polymer having a first polymer chain and a second polymer chain that is different from the first polymer chain. The solvent is a mixture of two or more solvents selected from the group consisting of ester-based solvents and ketone-based solvents. The self-organizing film-forming composition contains a solvent and a first polymer having a first polymer chain and a second polymer chain that is different from the first polymer chain. The absolute value of the difference between the solubility parameter P of the first polymer and the solubility parameter S of the solvent is 0.35 or less.

Description

Composition for self-assembled monolayer formation and pattern formation method

The present invention relates to a composition for forming a self-assembled monolayer and a pattern forming method.

With the miniaturization of various electronic device structures such as semiconductor devices and liquid crystal devices, miniaturization of patterns in the pattern forming process is required. At present, for example, an ArF excimer laser can be used to form a fine pattern having a line width of about 50 nm, but even finer pattern formation is required.

In response to the above requirements, a method for forming a self-organizing pattern using a so-called self-organizing phase separation (microdomain) structure that spontaneously forms an order pattern has been proposed. As a method for forming such a self-assembling pattern, a block copolymer obtained by copolymerizing a monomer compound having one property and a monomer compound having different properties is used, and an ultrafine pattern is formed by self-assembling. Is known (see Patent Documents 1 to 3). According to this method, by annealing the film containing the block copolymer, it is possible to form a pattern in a self-aligned manner because the structures having the same properties are ordered to gather together. Further, a method of forming a fine pattern by self-assembling a composition containing a plurality of polymers having different properties from each other is also known (see Patent Documents 4 to 5).

Japanese Unexamined Patent Publication No. 2008-149447 Japanese Patent Publication No. 2002-591728 Japanese Patent Application Laid-Open No. 2003-218383 U.S. Patent Application Publication No. 2009/0214823 Japanese Unexamined Patent Publication No. 2010-58403

However, with the above-mentioned conventional technique, the coatability is not sufficient, and defects derived from foreign substances and aggregates (hereinafter, also referred to as "coating defects") are scattered in the obtained coating film.

The present invention has been made based on the above circumstances, and an object thereof is to provide a composition for forming a self-assembled monolayer and a pattern forming method capable of forming a self-assembled monolayer having few coating defects. To do.

As a result of repeated studies to solve this problem, the present inventors have suggested that the coating defect may be caused by the low solubility of the polymer in the composition for forming a self-assembling film in a solvent. I got the knowledge. As a result of further studies, it was found that the above object can be achieved by adopting the following configuration, and the present invention has been completed.

That is, the present invention, in one embodiment,
A first polymer (hereinafter, also referred to as “[A] polymer”) containing a first polymer chain and a second polymer chain different from the first polymer chain, and a solvent (hereinafter, “[B1] solvent”. Also called.)
Including
[B1] A composition for forming a self-assembled monolayer (hereinafter, also referred to as "composition (I)"", wherein the solvent is a mixture of two or more kinds of solvents selected from the group consisting of an ester solvent and a ketone solvent. ).

The present invention, in another embodiment,
[A] Contains a polymer and a solvent (hereinafter, also referred to as "[B2] solvent").
A composition for forming a self-assembled monolayer in which the absolute value of the difference between the solubility parameter P of the polymer [A] and the solubility parameter S of the solvent [B2] is 0.35 or less (hereinafter, “composition (II)). Also called.).

According to the composition (I) and the composition (II), in addition to or instead of using a mixed solvent of a specific solvent as the solvent to be blended with the first polymer, the solubility of each of the first polymer and the solvent is used. Since the parameters are close to each other, the solubility of the first polymer in the solvent can be improved, and as a result, the occurrence of coating defects can be reduced.

The present invention, in yet another embodiment,
A step of applying the above composition (I) or (II) on a substrate to form a coating film,
The present invention relates to a pattern forming method including a step of phase-separating the coating film to form a self-assembled monolayer and a step of removing a part of the phase of the self-assembled monolayer.

According to the pattern forming method, a pattern having a good shape can be formed by using a self-assembled monolayer having few coating defects. Therefore, these can be suitably used in a pattern forming step in manufacturing various electronic devices such as semiconductor devices and liquid crystal devices, which are required to be further miniaturized.

In the present specification, "self-assembling (Directed Self Assembly)" refers to a phenomenon in which an organization or structure is spontaneously constructed without being caused only by control from external factors.

It is a schematic diagram which shows an example of the state after forming a coating film on a substrate in the pattern forming method which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the state after forming the self-assembled monolayer in the pattern forming method which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the state after forming the lower layer film on the substrate in the pattern forming method which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the state after forming the pre-pattern on the underlayer film in the pattern forming method which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the state after forming the coating film in the region on the lower layer film sandwiched by the pre-pattern in the pattern forming method which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the state after forming the self-assembled monolayer in the region on the lower layer membrane sandwiched by the pre-pattern in the pattern formation method which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the state after removing a part phase and a pre-pattern of a self-assembled monolayer in the pattern formation method which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the self-assembled monolayer forming composition and the pattern forming method of the present invention will be described in detail with reference to the drawings.

<< First Embodiment >>
[Composition (I)]
The composition (I) contains the [A] polymer and the [B1] solvent. In addition to the [A] polymer and the [B1] solvent, the composition (I) is a second polymer having a smaller surface free energy than the [A] polymer (hereinafter, also referred to as “[C] polymer”). , Other components such as surfactants may be contained. Hereinafter, each component of the composition (I) will be described.

<[A] Polymer>
[A] The polymer is one or more kinds of polymers capable of forming a phase-separated structure by self-assembly. The [A] polymer is a so-called block copolymer containing a first polymerized chain and a second polymerized chain different from the first polymerized chain. Although one or more block copolymers can be used as the [A] polymer, only one type of block copolymer (hereinafter, also referred to as “[A1] block copolymer”) should be used. Is preferable. Further, the composition (I) may contain another polymer (hereinafter, also referred to as “[A2] polymer”) in addition to the [A] polymer as long as the phase-separated structure is formed.

([A1] block copolymer)
[A1] The block copolymer is a polymer having a structure in which a plurality of blocks are bonded. Each of the above blocks consists of a chain structure of structural units derived from one type of monomer. In such a [A1] block copolymer having a plurality of blocks, blocks of the same type aggregate with each other by heating or the like to form a phase composed of blocks of the same type. At this time, since the phases formed from different types of blocks do not mix with each other, it is presumed that a phase separation structure having an ordered pattern in which different types of phases are periodically and alternately repeated can be formed.

Examples of the [A1] block copolymer include diblock copolymers, triblock copolymers, and tetrablock copolymers. Among these, diblock copolymers and triblock copolymers are preferable, and diblock copolymers are more preferable, from the viewpoint that a pattern having a desired fine phase separation structure can be more easily formed.

Examples of the block include polystyrene block, poly (meth) acrylic acid ester block, polyvinyl acetal block, polyurethane block, polyurea block, polyimide block, polyamide block, epoxy block, novolak type phenol block, polyester block and the like.

From the viewpoint of easy formation of a phase-separated structure and easy removal of a phase, the [A1] block copolymer is preferably a polymer composed of a polystyrene block and a poly (meth) acrylic acid ester block.

[A1] When the block copolymer is a diblock copolymer, the abundance ratio of the structural unit (A) to the total of the two structural units (A) and (B) constituting these blocks based on the mass. Can be appropriately selected according to the line / space width ratio of the desired line space pattern, the size of the contact hole, and the like. When forming a lamellar structure, the abundance ratio of (A) is preferably 0.35 or more, more preferably 0.40 or more, from the viewpoint of forming a fine and good phase-separated structure. Further, 0.65 or less is preferable, and 0.60 or less is more preferable. When forming a cylinder structure, the abundance ratio of (A) is preferably 0.65 or more from the viewpoint of forming a fine and good phase-separated structure. Further, 0.85 or less is preferable, and 0.75 or less is more preferable.

([A1] Method for synthesizing block copolymer)
[A1] The block copolymer can be synthesized by forming each block in a desired order by living anionic polymerization, living radical polymerization, or the like. For example, it can be synthesized by connecting polystyrene blocks, poly (meth) acrylic acid ester blocks, other blocks and the like while polymerizing in a desired order, and then adding methanol or the like to terminate the polymerization.

For example, when synthesizing a [A1] block copolymer, which is a diblock copolymer composed of a polystyrene block and a poly (meth) acrylic acid ester block, first, an anionic polymerization initiator is used and styrene is used in a suitable solvent. Polystyrene blocks are synthesized by polymerizing. Next, it is connected to a polystyrene block and the (meth) acrylic acid ester is polymerized in the same manner to synthesize a poly (meth) acrylic acid ester block. Then, the polymerization is stopped by adding methanol or the like. Examples of the method for synthesizing each block include a method in which a solution containing a monomer is dropped into a reaction solvent containing an anionic polymerization initiator to carry out a polymerization reaction.

Examples of the solvent used for the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane;
Cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, norbornane;
Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, cumene;
Saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, methyl propionate;
Ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone;
Examples thereof include ethers such as tetrahydrofuran, dimethoxyethanes and diethoxyethanes. These solvents may be used alone or in combination of two or more.

Examples of the anionic polymerization initiator used in the above polymerization include alkyllithium, alkylmagnesium halide, naphthalene sodium, alkylated lanthanoid compounds and the like. Of these, when polymerizing using styrene and / or (meth) acrylic acid ester as the monomer, it is preferable to use an alkyllithium compound.

In the above polymerization, after forming each block in a desired order as described above, the polymerization terminal is treated with, for example, a terminal treatment agent containing a hetero atom, whereby the hetero atom is contained at the end of the block copolymer. It is also possible to introduce a group. [A1] By introducing a group containing a heteroatom at the end of the block copolymer, the phase separation in the composition (I) can be controlled to be better.

Examples of the terminal treatment agent containing the heteroatom include epoxy compounds such as 1,2-butylene oxide, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, propylene oxide, ethylene oxide, and epoxyamine;
Isocyanate compound, thioisocyanate compound, imidazolidinone, imidazole, aminoketone, pyrrolidone, diethylaminobenzophenone, nitrile compound, aziridine, formamide, epoxyamine, benzylamine, oxime compound, azine, pidrazone, imine, azocarboxylic acid ester, aminostyrene, vinyl Nitrogen-containing compounds such as pyridine, aminoacrylate, aminodiphenylethylene and imide compounds;
Silane compounds such as alkoxysilane, aminosilane, ketoiminosilane, isocyanatesilane, siloxane, glycidylsilane, mercaptosilane, vinylsilane, epoxysilane, pyridylsilane, piperazylsilane, pyrrolidonesilane, cyanosilane, and isocyanatesilane;
Examples thereof include tin halide, silicon halide, and carbon dioxide.

The [A1] block copolymer synthesized by the above polymerization is preferably recovered by the reprecipitation method. That is, after the polymerization reaction, the target copolymer is recovered as a powder by putting the reaction solution into the reprecipitation solvent. As the reprecipitation solvent, alcohols, alkanes and the like can be used alone or in combination of two or more. In addition to the reprecipitation method, the polymer can be recovered by removing low molecular weight components such as monomers and oligomers by a liquid separation operation, a column operation, an ultrafiltration operation, or the like.

[A1] The weight average molecular weight (Mw) of the block copolymer by gel permeation chromatography (GPC) is preferably 1,000 or more, more preferably 8,000 or more, still more preferably 20,000 or more, and 40. 000 or more is particularly preferable. Further, 150,000 or less is preferable, 100,000 or less is more preferable, 80,000 or less is further preferable, and 70,000 or less is particularly preferable. [A1] By setting the Mw of the block copolymer in the above range, a better phase separation structure can be formed.

The ratio (Mw / Mn) of Mw of the [A1] block copolymer to the number average molecular weight (Mn) is usually 1 or more. Further, it is usually 3 or less, more preferably 2 or less, further preferably 1.5 or less, and particularly preferably 1.2 or less. [A1] By setting the Mw / Mn of the block copolymer in the above range, a better phase-separated structure can be formed.

For Mw and Mn, Tosoh GPC columns (2 "G2000HXL", 1 "G3000HXL" and 1 "G4000HXL") were used, eluent: tetrahydrofuran (Wako Pure Chemical Industries, Ltd.), flow rate: 1.0 mL. / Min, sample concentration: 1.0% by mass, sample injection volume: 100 μL, column temperature: 40 ° C., measured by GPC using a differential refractometer as a detector and monodisperse polystyrene as a standard. Is.

([A2] polymer)
[A2] Examples of the polymer constituting the polymer include an acrylic polymer, a styrene polymer, a vinyl acetal polymer, a urethane polymer, a urea polymer, an imide polymer, and an amide polymer. Examples thereof include novolak-type phenol polymers and ester-based polymers. The polymer may be a homopolymer synthesized from one kind of monomer or a random copolymer synthesized from a plurality of kinds of monomers. [A1] A homopolymer or a random copolymer corresponding to each block composition constituting the block copolymer can be preferably adopted. When a polymer composed of a polystyrene block and a poly (meth) acrylic acid ester block is used as the [A1] block copolymer, a mixed system of an acrylic polymer and a styrene polymer may be used as the [A2] polymer. , A random copolymer of an acrylic monomer and a styrene monomer can be used.

([A2] Polymer Synthesis Method)
[A2] The polymer can be produced, for example, by polymerizing a monomer corresponding to each predetermined structural unit in an appropriate polymerization reaction solvent using a polymerization initiator such as a radical polymerization initiator. Examples of the method for synthesizing the polymer include a method in which a solution containing a monomer and a polymerization initiator is dropped onto a polymerization reaction solvent or a solution containing a monomer to carry out a polymerization reaction, and polymerization with a solution containing a monomer. A method in which a solution containing an initiator is separately added dropwise to a polymerization reaction solvent or a solution containing a monomer to carry out a polymerization reaction, a method containing a plurality of types of solutions containing each monomer and a solution containing a polymerization initiator. Examples thereof include a method in which the above is dropped into a polymerization reaction solvent or a solution containing a monomer to carry out the polymerization reaction.

Examples of the radical polymerization initiator include azobisisobutyronitrile (AIBN), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 2,2'-azobis (2-cyclopropylpro). Pionitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate and other azo radical polymerization initiators; benzoyl peroxide, t-butyl hydroperoxide , Peroxide radical polymerization initiators such as cumenehydroperoxide and the like. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferable, and AIBN is more preferable. These radical polymerization initiators can be used alone or in admixture of two or more.

As the solvent used for the above-mentioned polymerization, for example, the same solvent as those mentioned in the above-mentioned method for synthesizing the [A1] block copolymer can be used.

The reaction temperature in the above polymerization is usually 40 ° C. or higher, preferably 50 ° C. or higher. Further, it is usually 150 ° C. or lower, preferably 120 ° C. or lower. The reaction time in the above polymerization is usually 1 hour or more. Further, it is usually 48 hours or less, preferably 24 hours or less.

The polymer obtained by the above polymerization reaction is preferably recovered by the reprecipitation method in the same manner as the above-mentioned method for synthesizing the [A1] block copolymer.

The Mw of the [A2] polymer is not particularly limited, but is preferably 3,000 or more, more preferably 5,000 or more, further preferably 7,000 or more, and particularly preferably 8,000 or more. Further, 50,000 or less is preferable, 30,000 or less is more preferable, 20,000 or less is further preferable, and 15,000 or less is particularly preferable. By setting the Mw of the polymer in the above range, a finer pattern can be obtained from the composition (I), and the rectangularity of the pattern is also improved. If the Mw of the polymer is less than the above lower limit, the heat resistance of the self-assembled monolayer may decrease. If the Mw of the polymer exceeds the upper limit, a sufficiently fine pattern may not be obtained.

The Mw / Mn of the [A2] polymer is usually 1 or more. Further, it is usually 5 or less, preferably 3 or less, and more preferably 2 or less.

[A] The content of the polymer (the total of a plurality of types of polymers, if present) is preferably 70% by mass or more, preferably 80% by mass or more, based on the total solid content of the composition (I). More preferably, 90% by mass or more is further preferable, and 95% by mass or more is particularly preferable.

<[B1] solvent>
[B1] The solvent is a mixture of two or more kinds of solvents selected from the group consisting of an ester solvent and a ketone solvent. [B] As the solvent, two or more kinds may be selected from only the ester-based solvent, two or more kinds may be selected from only the ketone-based solvent, one or more kinds may be selected from the ester-based solvent, and one shall be selected from the ketone-based solvent. A mixture of more than one species may be selected and used as a mixed solvent. Considering the solubility of the polymer [A], the solvent [B1] is preferably a mixture of two solvents in which one is selected from the ester solvent and one is selected from the ketone solvent. [B1] The solvent may contain a solvent other than the ester solvent and the ketone solvent as long as the effect of the present invention is not impaired.

(Ester solvent)
The ester solvent is not particularly limited as long as it has an ester bond in the molecule and the polymer [A] exhibits solubility, and even if it is a chain ester solvent, it is a cyclic ester solvent (the ester bond is a ring). It may be a solvent which constitutes a part of the above.

Examples of the chain ester solvent include, for example.
Monocarboxylic acid ester solvents such as butyl acetate, ethyl lactate, butoxyethyl acetate, methoxybutyl acetate, cyclohexanol acetate;
Polyhydric alcohol carboxylate solvent such as propylene glycol diacetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate;
Polyhydric alcohol partial ether carboxylate solvent such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate;
Multivalent condensed alcohol partial ether carboxylate solvent such as diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate;
Triacetin polyvalent carboxylic acid ester solvent such as diethyl oxalate;
Examples thereof include carbonate solvents such as dimethyl carbonate and diethyl carbonate.

Examples of the cyclic ester solvent include β-propiolactone, γ-butyrolactone and the like.

As the ester solvent, a chain ester solvent is preferable from the viewpoint of solubility, coatability, and solvent removal property of the polymer [A]. The chain ester solvent preferably further contains an ether bond from the viewpoint of solubility and coatability of the polymer [A].

As the chain ester solvent, a monocarboxylic acid ester solvent, a polyhydric alcohol carboxylate solvent, a polyhydric alcohol partial ether carboxylate solvent and a polyhydric condensed alcohol partial ether carboxylate solvent are preferable, and a monocarboxylic acid ester is used. A system solvent and a polyhydric alcohol partially ether carboxylate system solvent are more preferable. Of these, butyl acetate, ethyl lactate, methoxybutyl acetate and propylene glycol monomethyl ether acetate are particularly preferable.

(Ketone solvent)
The ketone solvent is not particularly limited as long as it has a carbonyl group (excluding those contained in the ester bond) in the molecule and the [A] polymer exhibits solubility, and is a chain ketone solvent. Alternatively, it may be a cyclic ketone solvent.

Examples of the chain ketone solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-iso-butyl ketone, 2-heptanone, ethyl-n-butyl ketone, and methyl-n-. Examples thereof include hexyl ketone, di-iso-butyl ketone, trimethylnonanonone and the like.

The cyclic ketone solvent is preferably a cyclic ketone solvent having 5 to 8 ring members, and examples thereof include cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone.

As the ketone solvent, a cyclic ketone solvent is preferable from the viewpoint of solubility, coatability, and solvent removal property of the polymer [A]. Of these, cyclopentanone and cyclohexanone are more preferable, and cyclohexane is particularly preferable.

[B1] When the solvent contains both the ester solvent and the ketone solvent, the ratio of the ketone solvent to the total mass of the ester solvent and the ketone solvent is preferably 10% by mass or more, preferably 20% by mass or more. Is more preferable, and 30% by mass or more is further preferable. Further, 90% by mass or less is preferable, 80% by mass or less is more preferable, and 70% by mass or less is further preferable. By setting the content of the ketone solvent in the above range in the mixed solvent system of the ester solvent and the ketone solvent, the solubility of the polymer [A] can be improved and the suppression of coating defects is efficient. Can be planned.

(Other solvents)
[B1] The solvent may contain a solvent other than the ester solvent and the ketone solvent. Examples of other solvents include alcohol solvents, ether solvents, amide solvents, hydrocarbon solvents and the like.

Examples of the alcohol solvent include, for example.
Aliphatic monoalcoholic solvents with 1 to 18 carbon atoms such as 4-methyl-2-pentanol and n-hexanol;
An alicyclic monoalcohol solvent having 3 to 18 carbon atoms such as cyclohexanol;
Polyhydric alcohol solvent with 2 to 18 carbon atoms such as 1,2-propylene glycol;
Examples thereof include a polyhydric alcohol partially ether solvent having 3 to 19 carbon atoms such as propylene glycol monomethyl ether.

Examples of the ether solvent include, for example.
Dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, diheptyl ether;
Cyclic ether solvent such as tetrahydrofuran and tetrahydropyran;
Examples thereof include aromatic ring-containing ether solvents such as diphenyl ether and anisole.

Examples of the amide solvent include cyclic amide solvents such as N, N'-dimethylimidazolidinone and N-methylpyrrolidone;
Examples thereof include chain amide solvents such as N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide and N-methylpropionamide.

Examples of the hydrocarbon solvent include, for example.
An aliphatic hydrocarbon solvent having 5 to 12 carbon atoms such as n-pentane and n-hexane;
Examples thereof include aromatic hydrocarbon solvents having 6 to 16 carbon atoms such as toluene and xylene.

When the [B1] solvent contains another solvent, the content of the other solvent in the [B1] solvent is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 5% by mass or more. 10% by mass or more is particularly preferable. Further, 30% by mass or less is preferable, 25% by mass or less is more preferable, 20% by mass or less is further preferable, and 15% by mass or less is particularly preferable. [B1] When the solvent contains another solvent in the above range, a self-assembled monolayer having less defects in the ordered structure can be obtained while ensuring good filterability of the composition for forming a self-assembled monolayer. Can be formed.

[Other ingredients]
<[C] Polymer>
The [C] polymer is a polymer having a smaller surface free energy than the [A] polymer. As shown in FIG. 1, when the coating film 102 is formed on the substrate 101 by the composition (I) containing the [C] polymer (the forming method will be described later), the [C] polymer is [A]. Since the surface free energy is smaller than that of the polymer, it is considered that the [C] polymer is unevenly distributed in the upper region in the coating film 102 in the process of self-assembly. The phase separation of the [A] polymer proceeds better by the interaction between the [C] polymer unevenly distributed in the upper region in the coating film 102 and the [A] polymer existing in the region other than the upper region. It is possible to form a self-assembled film 103 (see FIG. 2) having a block phase (I) 103a and a block phase (II) 103b as a better phase separation structure, resulting in a more regular. It is possible to obtain a self-assembled film having few defects in the arrangement structure. As mentioned above, the reason why the phase separation is improved by the [C] polymer is not always clear, but for example, when the [C] polymer is not applied, the difference in surface free energy between the atmosphere and the [A] polymer is large. Due to its large size, phase separation in the substantially horizontal direction tends to be promoted, but by applying the [C] polymer, the difference in surface free energy from the polymer [A] becomes smaller, and the phase separation in the substantially horizontal direction becomes smaller. Since the phase separation is suppressed, it is conceivable that the phase separation in the substantially vertical direction is effectively carried out as a result. Finally, as shown in FIG. 2, the [C] polymer is unevenly distributed in the region 104 above the self-assembled monolayer 103.

The surface free energy of each polymer is obtained by spin-coating the solution of each polymer and then heating to form a thin film of each polymer. (1969) ”. K. According to the method of OWENS et al., The contact angle of a liquid such as pure water and methylene iodide on the thin film can be measured, and can be obtained from the measured values using the relationship of the following formula (X) and the following formula (Y). ..

(1 + cosθ) × γ _L = 2 (γ _S ^d × γ _L ^d ) ^1/2 + 2 (γ _S ^p × γ _L ^p ) ^1/2
... (X)
γ _S = γ _S ^d + γ _S ^p ... (Y)
(Γ _S : Surface free energy of polymer, γ _S ^d : ^Dispersion component of surface free energy of polymer, γ _Sp : Polar component of surface free energy of polymer, γ _L : Surface free energy of liquid, γ _L ^d : Dispersion component of the surface free energy of the liquid, γ _L ^p : Polar component of the surface free energy of the liquid, θ: Contact angle)

The value obtained by subtracting the surface free energy of the [C] polymer from the surface free energy of the [A] polymer is preferably 1 mN / m or more, more preferably 3 mN / m or more, still more preferably 5 mN / m or more, and 7 mN. It is particularly preferably / m or more, and even more preferably 9 mN / m or more. Further, 20 mN / m or less is preferable, 18 mN / m or less is more preferable, 15 mN / m or less is further preferable, 13 mN / m or less is particularly preferable, and 11 mN / m or less is even more preferable. By setting the surface free energy difference within the above range, the [C] polymer is more effectively unevenly distributed in the coating film forming step and the like, and the interaction between the [C] polymer and the [A] polymer is allowed to occur. It is considered that it can be enhanced more effectively, and as a result, a self-assembled membrane having less defects in the ordered arrangement structure can be obtained.

The [C] polymer is not particularly limited as long as the surface free energy is smaller than that of the [A] polymer, but is a structural unit containing a fluorine atom and / or a silicon atom (hereinafter, also referred to as “structural unit (I)”). It is preferable to have. Examples of the structural unit (I) containing a fluorine atom include 1,1,1,3,3,3-hexafluoro-2-propyl (meth) acrylate and 1,1-difluoro-1-ethoxycarbonylbutane-2. -Examples include structural units derived from (meth) acrylates containing a fluorine atom such as yl (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, and trifluoromethyl (meth) acrylate. The structural unit (I) containing a silicon atom is derived from, for example, a (meth) acrylate containing a silicon atom such as 2- (trimethylsilyl) ethyl (meth) acrylate and 2- (trimethoxysilyl) ethyl (meth) acrylate. Examples include structural units to be used. The content ratio of the structural unit (I) is preferably 10 mol% or more, more preferably 14 mol% or more, still more preferably 18 mol% or more, based on all the structural units constituting the [C] polymer. 22 mol% or more is particularly preferable. Further, 50 mol% or less is preferable, 45 mol% or less is more preferable, 40 mol% or less is further preferable, and 36 mol% or less is particularly preferable. By setting the content ratio of the structural unit (I) in the above range, the uneven distribution of the above-mentioned [C] polymer and the interaction between the [C] polymer and the [A] polymer are more effectively improved. be able to.

Further, the [C] polymer may have a structural unit other than the structural unit (I) (hereinafter, also referred to as “structural unit (II)”). Examples of the structural unit (II) include structural units derived from (meth) acrylic acid esters, structural units derived from styrene compounds, and the like.

Examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, norbornyl (meth) acrylate, and (meth) acrylic. Examples include adamantyl acid, tetrahydrofurfuryl (meth) acrylate, and the like.

Examples of the styrene compound include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 4-hydroxystyrene, 4- (t-butoxy) styrene and the like.

As the structural unit of the [C] polymer, it is considered that the interaction with the [A] polymer can be more appropriately enhanced, and from the viewpoint of forming a better phase-separated structure, the [A] polymer It is preferable to include at least a part of the structural units possessed by the polymer, and it is more preferable to include all the structural units possessed by the polymer [A]. For example, when the polymer [A] is a diblock copolymer of polystyrene block-tetrahydrofurfuryl block poly (meth) acrylate, the polymer [C] is derived from styrene in addition to the structural unit (I). It is preferable to have at least one of a structural unit derived from and a structural unit derived from tetrahydrofurfuryl (meth) acrylate, and both a structural unit derived from styrene and a structural unit derived from tetrahydrofurfuryl (meth) acrylate. It is more preferable to have.

As the [C] polymer, a random copolymer is preferable from the viewpoint of being able to more effectively exhibit the interaction with the [A] polymer and forming a better phase-separated structure.

In the [C] polymer, for example, a monomer giving each structural unit such as the structural unit (I) and the structural unit (II) is subjected to radical polymerization in the same manner as in the above-mentioned method for synthesizing the polymer [A]. It can be synthesized by polymerizing in an appropriate solvent using an agent or the like.

The Mw of the [C] polymer is preferably 1,000 or more, more preferably 5,000 or more, further preferably 8,000 or more, and particularly preferably 10,000 or more. Further, 100,000 or less is preferable, 60,000 or less is more preferable, 40,000 or less is further preferable, and 30,000 or less is particularly preferable. [C] By setting the Mw of the polymer in the above range, it is possible to form a self-assembled monolayer having less defects in the ordered structure.

The Mw / Mn of the [C] polymer is usually 1 or more, preferably 1.1 or more. Further, it is usually 5 or less, preferably 3 or less, more preferably 2.5 or less, further preferably 1.8 or less, and particularly preferably 1.5 or less. [C] By setting the Mw / Mn of the polymer in the above range, it is possible to form a self-assembled monolayer having less defects in the ordered structure.

<Surfactant>
The composition (I) may further contain a surfactant. When the composition (I) contains a surfactant, the applicability to a substrate or the like can be improved.

<Preparation method of composition (I)>
The composition (I) can be prepared, for example, by mixing the polymer [A], the solvent [B1], and if necessary, other components, and filtering the composition with a membrane filter having a pore size of about 200 nm. More preferably, it can be prepared by circulating filtration with a high-density polyethylene filter having a pore size of about 10 nm.

The solid content concentration of the composition (I) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, and particularly preferably 5% by mass or more. The upper limit of the solid content concentration of the composition (I) is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and particularly preferably 20% by mass or less.

<< Second Embodiment >>
[Composition (II)]
The composition (II) contains the [A] polymer and the [B2] solvent. In the composition (I), the [B1] solvent is specified from the viewpoint of being a mixture of predetermined solvents, whereas in the composition (II), the [B2] solvent is used as the solubility parameter of the [A] polymer. It is specified from the viewpoint of closeness. In the composition (II), the polymer [A], other components, the preparation method, etc. are the same as those in the composition (I). explain.

The solubility parameter value of the solvent is expressed using the Hansen solubility parameter. The Hansen solubility parameter can be obtained by dividing the solubility parameter introduced by Hildebrand into three components, the dispersion term δd, the polarity term δp, and the hydrogen bond term δh, and obtaining δ = (δd ² + δp ² + δh ² ) ^1/2 . can. The dispersion term δd indicates a non-polar interaction, the polar term δp indicates an interaction between dipoles, and the hydrogen bond term δh indicates a hydrogen bond interaction. The value of the Hansen solubility parameter is obtained by using computer software (product name "Hansen Solubility Parameters in Practice"). Further, when the solvent is a mixed solvent of two kinds of the solvent 1 and the solvent 2, the Hansen solubility parameter Am is δAm = X1 × δ1 + (1-X1) × δ2 (δ1 and δ2 are the solvent 1 and the solvent 2, respectively). It is a value of the Hansen solubility parameter. X1 is a molar fraction of the solvent 1 in the mixed solvent).

<[B2] solvent>
As the [B2] solvent, the absolute value of the difference between the solubility parameter P of the [A] polymer and the solubility parameter S of the [B2] solvent (hereinafter, also referred to as “(PS) value”) is 0. Use a solvent such that it is .35 or less. As a result, the solubility of the [A] polymer in the [B2] solvent can be improved, the generation of residues can be suppressed, and a self-assembled film with reduced coating defects can be formed.

Although the above (PS) value may be 0.35 or less, it is preferably 0.30 or less, more preferably 0.25 or less, further preferably 0.20 or less, still more preferably 0.15 or less. 0.10 or less is particularly preferable. There is no difference between the solubility parameter P of the [A] polymer and the solubility parameter S of the [B2] solvent, that is, the above (PS) value is preferably 0, but even if it is 0.001 or more. It may be 0.002 or more, or 0.005 or more.

[B2] As the solvent, as long as the above (PS) value is satisfied, only one kind of solvent may be used, or a mixture of a plurality of kinds of solvents may be used. When a mixture of a plurality of kinds of solvents is used, the solubility parameter of the mixture may satisfy the above (PS) value. From the viewpoint of ease of controlling the (PS) value, the [B2] solvent is preferably a mixture of a plurality of kinds of solvents having different solubility parameters. Among them, the [B2] solvent is preferably a mixture of a solvent having a solubility parameter S1 larger than the solubility parameter P and a solvent having a solubility parameter S2 smaller than the solubility parameter P. For example, by gradually adding a solvent having a solubility parameter S2 smaller than the solubility parameter P to a solvent having a solubility parameter S1 larger than the solubility parameter P, the solubility parameter of the mixture is approximated to the solubility parameter P of the polymer [A]. Can be made to. The same is true for the reverse operation.

As the specific [B2] solvent, the ester solvent, the ketone solvent, the alcohol solvent, the ether solvent, the amide solvent, the hydrocarbon solvent and the like exemplified in the composition (I) may be preferably used. can. From these solvents, one or more kinds of solvents satisfying the above (PS) value may be appropriately selected. Suitable solvents and combinations thereof are the same as in composition (I).

<< Third Embodiment >>
[Pattern formation method]
The pattern forming method according to the present embodiment is a step of applying the composition (I) or (II) on a substrate to form a coating film (hereinafter, also referred to as a “coating film forming step”), wherein the coating film is formed. A step of forming a self-assembled film by phase separation (hereinafter, also referred to as a “self-assembled film forming step”), and a step of removing a part of the phase of the self-assembled film (hereinafter, “removal step”). Also called.) Includes.

The self-assembled monolayer forming step preferably includes a step of heating the coating film (hereinafter, also referred to as a "heating step"). Further, a step of allowing the coating film to stand still (hereinafter, also referred to as “standing step”) may be provided before the heating step or at the same time as the heating step. Further, an annealing step for stabilizing the phase separation structure may be provided. Examples of the phase-separated structure formed in the self-assembled monolayer forming step include a sea-island structure, a cylinder structure, a co-continuous structure, and a lamellar structure. The phase separation structure may be partial.

In the pattern forming method, before the coating film forming step, a step of forming a lower layer film on the upper surface side of the substrate (hereinafter, also referred to as “lower layer film forming step”) and / or a pre-pattern on the upper surface side of the substrate is formed. A step of forming (hereinafter, also referred to as a “pre-pattern forming step”) may be further provided.

The pattern forming method may further include a step of removing the pre-pattern (hereinafter, also referred to as “pre-pattern removing step”) after the removing step, and the pattern formed after the removing step is used as a mask as described above. It is preferable to further include a step of etching the substrate (hereinafter, also referred to as “board pattern forming step”).

Therefore, the pattern forming method according to the present embodiment is typically a lower layer film forming step, a pre-pattern forming step, a coating film forming step, a self-assembling film forming step (standing step, heating step and annealing step). The removing step, the pre-pattern removing step, and the substrate pattern forming step are included in this order. Hereinafter, each process will be described with reference to the drawings. The case where the [A] polymer in the composition (I) or (II) is a [A1] block copolymer will be described as an example.

[Underlayer film forming process]
This step is a step of forming the lower layer film 105 on the upper surface side of the substrate 101. As a result, as shown in FIG. 3, a substrate with a lower layer film 105 having a lower layer film 105 formed on the substrate 101 can be obtained. The self-assembled monolayer 103, which will be described later, is formed on the underlayer film 105. Since the phase-separated structure of the self-assembled membrane 103 changes not only by the interaction between each block of the [A1] block copolymer contained in the composition (I), but also by the interaction with the underlying membrane 105. Having the underlayer film 105 may facilitate structural control. Further, when the self-assembled monolayer 103 is a thin film, the transfer process can be improved by having the underlayer film 105.

As the composition for forming the underlayer film used for forming the underlayer film 105, a conventionally known organic underlayer film forming material or the like can be used, for example, a composition for forming an underlayer film containing a cross-linking agent, a thermal acid generator, or the like. Can be mentioned.

The method for forming the underlayer film 105 is not particularly limited, but for example, the composition for forming the underlayer film is applied onto the substrate 101 by a known method such as a spin coating method, and then cured by exposure and / or heating to form the underlayer film 105. The method and the like can be mentioned. Examples of the radiation used for this exposure include visible light, ultraviolet rays, far ultraviolet rays, X-rays, electron beams, γ-rays, molecular rays, ion beams and the like. The heating temperature is not particularly limited, but is preferably 90 ° C. or higher. Further, 550 ° C or lower is preferable, 450 ° C or lower is more preferable, and 300 ° C or lower is further preferable. The heating time is preferably 5 seconds or longer, more preferably 10 seconds or longer, and even more preferably 20 seconds or longer. Further, 1,200 seconds or less is preferable, 600 seconds or less is more preferable, and 300 seconds or less is further preferable. The average thickness of the underlayer film 105 is not particularly limited, but is preferably 1 nm or more, more preferably 2 nm or more, still more preferably 3 nm or more. Further, 20,000 nm or less is preferable, 1,000 nm or less is more preferable, and 100 nm or less is further preferable.

[Pre-pattern formation process]
This step is a step of forming a pre-pattern. This pre-pattern may be formed on the substrate 101, or may be formed on the lower layer film 105 formed in the lower layer film forming step as shown in FIG. The shape of the phase-separated structure is controlled by the pre-pattern 106, and a finer pattern can be formed. That is, among the blocks contained in the [A1] block copolymer contained in the composition (I) or (II), the block having a high affinity with the side surface of the pre-pattern (referred to as "block (II)") is the pre-pattern. The block phase (II) 103b is formed along the block phase (II) 103b, and the block having a low affinity (referred to as “block (I)”) forms the block phase (I) 103a at a position away from the pre-pattern. As a result, the formed pattern becomes finer and better. Further, the phase separation structure of the self-assembled monolayer 103 can be finely controlled by the material, size, shape and the like of the pre-pattern. The pre-pattern 106 can be appropriately selected according to the pattern to be finally formed, and for example, a line-and-space pattern, a hole pattern, a cylinder pattern, or the like can be used.

When the pre-pattern 106 is provided, as described above, the phase separation structure of the self-assembled monolayer 103 is preferably formed along the pre-pattern 106, and the interface formed by the phase separation is the side surface of the pre-pattern 106. It is more preferable that they are substantially parallel. For example, when the [A1] block copolymer consists of a styrene block and a poly (meth) acrylic acid block and the pre-pattern has a high affinity with the styrene block, the phase of the styrene block is linear along the pre-pattern. It is formed, and next to it, a poly (meth) acrylic acid block phase and a styrene block phase are alternately arranged in this order to form a lamellar phase separation structure or the like. The phase separation structure formed is composed of a plurality of phases, and the interface formed from these phases is usually substantially vertical, but the interface itself does not necessarily have to be clear. Further, the phase separation structure obtained can be precisely controlled by the ratio of the length of each block chain in the block copolymer molecule, the length of the block copolymer molecule, the pre-pattern, the underlayer film, etc., and the desired fineness can be obtained. You can get a pattern.

Examples of the method for forming the pre-pattern 106 include the same method as the known resist pattern forming method. Further, as the composition used for forming the pre-pattern 106, a conventional resist composition such as a polymer having an acid dissociable group, a radiation-sensitive acid generator and a composition containing an organic solvent may be used. can. Specifically, for example, a commercially available chemically amplified resist composition is applied onto the substrate 101 or the underlayer film 105 to form a resist film. Next, the desired region of the resist film is irradiated with radiation through a mask having a specific pattern to expose the resist film. Examples of the radiation include electromagnetic waves such as ultraviolet rays, far ultraviolet rays, and X-rays; charged particle beams such as electron beams and α rays. Among these, far ultraviolet rays are preferable, ArF excimer laser light and KrF excimer laser light are preferable, and ArF excimer laser light is more preferable.

Further, as an exposure method, immersion exposure can be performed. Next, post-exposure baking (PEB) is performed, and development is performed using a developer such as an alkaline developer or an organic solvent to form a desired pre-pattern 106. It is preferable that the obtained pre-pattern 106 is further cured by heat treatment after irradiating it with ultraviolet rays of, for example, 254 nm or 193 nm. The heating temperature is usually 100 ° C. or higher and 250 ° C. or lower. The heating time is, for example, 1 minute or more and 30 minutes or less.

As a method for forming the pre-pattern 106, the same method as a known resist pattern forming method can be used. Further, as the composition for forming the pre-pattern, a conventional composition for forming a resist film can be used.

The surface of the pre-pattern 106 may be hydrophobized or hydrophilized. Specific treatment methods include hydrogenation treatment in which hydrogen plasma is exposed to hydrogen plasma for a certain period of time. By increasing the hydrophobicity or hydrophilicity of the surface of the pre-pattern 106, self-organization can be further promoted.

[Coating film forming process]
As shown in FIG. 5, this step is a step of forming the coating film 102 on the substrate 101 via the lower layer film 105. When the lower layer film 105 is not formed, the coating film 102 is directly formed on the substrate 101. The coating film 102 is formed by the composition (I) or (II). Examples of the substrate 101 include conventionally known wafers such as silicon wafers, silicon dioxide, and wafers coated with aluminum. Further, as described later, the underlayer film and / or the pre-pattern may be formed on the substrate. Examples of the method for forming the coating film 102 include rotary coating (spin coating), cast coating, roll coating and the like.

The average thickness of the coating film 102 to be formed is not particularly limited, but is preferably 0.2 nm or more, more preferably 1 nm or more, further preferably 2 nm or more, and particularly preferably 10 nm or more. Further, 1,000 nm or less is preferable, 200 nm or less is more preferable, 120 nm or less is further preferable, and 70 nm or less is particularly preferable.

[Self-assembled monolayer forming process]
The pattern forming method according to the present embodiment preferably includes a standing step and a heating step as the self-assembled monolayer forming step.

(Standing process)
This step is a step of allowing the coating film 102 formed in the coating film forming step to stand still. "Standing the coating film" means that the coating film-like state is maintained and does not move. By providing this step, a better phase separation structure can be formed. In this step, as long as the coating film retains the state of the coating film, a part or all of the [B1] solvent or the [B2] solvent may evaporate from the coating film.

The time for the standing step is preferably 1 minute or longer, more preferably 3 minutes or longer, and even more preferably 5 minutes or longer. By setting the above time in the above range, a better phase-separated structure can be formed, and thus a self-assembled monolayer having less defects in the ordered structure can be formed. From the viewpoint of productivity, the time is preferably 120 minutes or less, more preferably 60 minutes or less, further preferably 30 minutes or less, and particularly preferably 20 minutes or less.

After the standing step, a step of removing the solvent from the coating film (hereinafter, also referred to as “solvent removing step”) may be further provided. Examples of the method for performing the solvent removal step include a method of heating.

(Heating process)
This step is a step of heating the coating film 102. This step may be performed at any of the steps of the coating film forming step, the standing step, and the solvent removing step, but it is preferably performed in the standing step. By performing the heating step in the above-mentioned standing step, a better phase separation structure can be formed.

Examples of the heating method in the heating step include a method of heating with an oven, a hot plate, or the like.

The temperature of the heating step is preferably 40 ° C. or higher, more preferably 100 ° C. or higher, further preferably 150 ° C. or higher, and particularly preferably 200 ° C. or higher. Further, 300 ° C. or lower is preferable, 280 ° C. or lower is more preferable, 260 ° C. or lower is further preferable, and 240 ° C. or lower is particularly preferable. By setting the temperature of the heating step in the above range, a better phase separation structure can be formed.

The time of the heating step is preferably 1 minute or longer, more preferably 3 minutes or longer, and even more preferably 5 minutes or longer. Further, 120 minutes or less is preferable, 60 minutes or less is more preferable, 30 minutes or less is further preferable, and 20 minutes or less is particularly preferable. By setting the above time in the above range, a better phase separation structure can be formed.

After forming the phase-separated structure by the heating step, for example, ultraviolet rays of 254 nm or 193 nm may be further irradiated.

The self-assembled monolayer 103 is formed by forming the phase separation structure from the coating film 102. [A] The polymer is phase-separated in a direction substantially perpendicular to the substrate 101 to form a self-assembled monolayer 103. When the composition (I) contains the [C] polymer, for example, the [C] polymer is unevenly distributed above the self-assembled monolayer 103 to form the region 104, as shown in FIG.

The average thickness of the self-assembled monolayer 103 is not particularly limited, but is preferably 0.1 nm or more, more preferably 0.5 nm or more, further preferably 1 nm or more, and particularly preferably 10 nm or more. Further, 500 nm or less is preferable, 100 nm or less is more preferable, 60 nm or less is further preferable, and 40 nm or less is particularly preferable.

(Annealing process)
In the present embodiment, the pattern forming method may include a step of annealing the formed self-assembled monolayer 103 in order to make the phase separation structure of the self-assembled monolayer 103 clearer and more stable. Examples of the annealing method include a method of heating with an oven, a hot plate, or the like. The heating temperature is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and even more preferably 150 ° C. or higher. Further, 400 ° C. or lower is preferable, 350 ° C. or lower is more preferable, and 300 ° C. or lower is further preferable. The heating time is usually 30 seconds or longer, preferably 1 minute or longer, more preferably 2 minutes or longer, still more preferably 3 minutes or longer. Further, 120 minutes or less is preferable, 90 minutes or less is more preferable, and 60 minutes or less is further preferable.

[Removal process]
This step is a step of removing a part of the phase separation structure of the self-assembled monolayer 103. Further, the pre-pattern 106 can also be removed simultaneously with or separately from some of the above phases. As shown in FIGS. 6 and 7, the block phase (I) 103a and the pre-pattern 106 of the self-assembled monolayer 103 are removed by etching using the difference in the etching rate of each block phase separated by self-assembly. can do.

Before the above etching process, radiation may be applied if necessary. As the radiation, when the phase to be removed by etching is a polymethylmethacrylate block phase, radiation having a diameter of 254 nm can be used. Since the polymethylmethacrylate block phase is decomposed by the above irradiation, it becomes easier to etch.

As a method for removing a block phase of a part of the phase separation structure of the self-assembling film 103, for example, reactive ion etching (RIE) such as chemical dry etching and chemical wet etching; spatter etching, ion beam etching and the like. Known methods such as physical etching of the above can be mentioned. Of these, reactive ion etching (RIE) is preferable, and among them, chemical dry etching using CF ₄ , O ₂ gas, etc., and chemical wet etching (wet development) using a liquid etching solution such as an organic solvent and hydrofluoric acid are preferable. More preferred. Examples of the organic solvent include alkanes such as n-pentane, n-hexane and n-heptane, cycloalkanes such as cyclohexane, cycloheptane and cyclooctane, ethyl acetate, n-butyl acetate, i-butyl acetate and propionic acid. Saturated carboxylic acid esters such as methyl, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl n-pentyl ketone, alcohols such as methanol, ethanol, 1-propanol, 2-propanol and 4-methyl-2-pentanol. Kind and so on. These solvents may be used alone or in combination of two or more.

[Pre-pattern removal process]
This step is a step of removing the pre-pattern 106 as shown in FIGS. 6 and 7. By removing the pre-pattern 106, it becomes possible to form a finer and more complicated pattern. As a method for removing the pre-pattern 106, a method for removing a part of the phase separation structure described above can be applied. Further, this step may be performed at the same time as the removal step, or may be performed before or after the removal step.

[Substrate pattern forming process]
This step is a step of patterning by etching the lower layer film and the substrate using a pattern consisting of a part of the self-assembled monolayer remaining after the removal step as a mask. After the patterning on the substrate is completed, the phase used as the mask is removed from the substrate by a dissolution treatment or the like, and finally the patterned substrate can be obtained.

As the etching method, the same method as the method in the removal step can be used, and the etching gas and the etching solution can be appropriately selected depending on the material of the underlayer film and the substrate. For example, when the substrate is made of a silicon material, a mixed gas of Freon-based gas and SF4 can be used. When the substrate is a metal film, a mixed gas of BCl ₃ and Cl ₂ can be used. The pattern obtained by the pattern forming method is preferably used for a semiconductor element or the like, and the semiconductor element is also used for an LED, a solar cell or the like.

Further, even when the [A] polymer contains not only the [A1] block copolymer but also the [A2] polymer, the pattern can be similarly formed by the above method.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The measurement method of each physical property value is shown below.

[Mw and Mn]
Mw and Mn of the polymer are measured by gel permeation chromatography (GPC) using Tosoh's GPC columns (2 "G2000HXL", 1 "G3000HXL", 1 "G4000HXL") under the following conditions. did.
(Measurement condition)
Eluent: Tetrahydrofuran (Wako Pure Chemical Industries, Ltd.)
Flow rate: 1.0 mL / min Sample concentration: 1.0 mass%
Sample injection amount: 100 μL
Column temperature: 40 ° C
Detector: Differential refractometer Standard material: Monodisperse polystyrene

[ ¹³ C-NMR analysis]:
¹³ C-NMR analysis was performed using a nuclear magnetic resonance apparatus (“JNM-EX400” manufactured by JEOL Ltd.) and DMSO-d ₆ as a measurement solvent. The content ratio of each structural unit in the polymer was calculated from the area ratio of the peak corresponding to each structural unit in the spectrum obtained by ¹³ C-NMR.

<[A] Polymer synthesis>
[Synthesis Example 1] (Synthesis of block copolymer (P-1))
After drying the 500 mL flask reaction vessel under reduced pressure, 200 g of hydrochloric acid subjected to distillation dehydration treatment was injected under a nitrogen atmosphere, and the mixture was cooled to −78 ° C. Then, 0.27 g of a 1N cyclohexane solution of sec-butyllithium (sec-BuLi) was injected, and 10.7 g (0.103 mol) of styrene subjected to distillation dehydration treatment was added dropwise over 30 minutes. At this time, care was taken so that the internal temperature of the reaction solution did not exceed -60 ° C. After aging for 30 minutes after the completion of the dropping, 10.3 g (0.103 mol) of methyl methacrylate, which had been further subjected to distillation dehydration treatment, was dropped and injected over 30 minutes and reacted for 120 minutes. After that, 1 mL of methanol was injected as a terminal treatment agent to react. The temperature of the polymerization reaction solution was raised to room temperature, the obtained polymerization reaction solution was concentrated and replaced with propylene glycol methyl ether acetate (PGMEA), and then 1,000 g of a 2% by mass aqueous solution of oxalic acid was injected and stirred, and then allowed to stand. , The lower aqueous layer was removed. This operation was repeated 3 times to remove the Li salt, and then 1,000 g of ultrapure water was injected and stirred to remove the lower aqueous layer. This operation was repeated 3 times to remove oxalic acid, and then the obtained solution was concentrated and then added dropwise to 500 g of methanol to precipitate a polymer. The polymer obtained by filtration under reduced pressure was washed twice with methanol and then dried under reduced pressure at 60 ° C. to obtain 20.5 g of a white block copolymer (P-1).

The Mw of the block copolymer (P-1) was 51,000, and the Mw / Mn was 1.13. As a result of ¹³ C-NMR analysis, the content ratio of the styrene unit and the content ratio of the methyl methacrylate unit in the block copolymer (P-1) were 50.1 mol% and 49.9 mol%, respectively. .. The block copolymer (P-1) is a diblock copolymer.

[Synthesis Example 2]
<Synthesis of [C] polymer>
24.90 g (0.240 mol) of styrene, 40.66 g (0.239 mol) of tetrahydrofurfuryl methacrylate and 34.44 g (0.205 mol) of 2,2,2-trifluoroethyl methacrylate are dissolved in 200 g of 2-butanone. Then, a monomer solution containing 1.12 g of AIBN as a radical polymerization initiator was prepared. A 1,000 mL three-necked flask containing 100 g of 2-butanone was purged with nitrogen for 30 minutes, then heated to 80 ° C. with stirring in the reaction vessel, and the above-prepared monomer solution was poured over 3 hours using a dropping funnel. Dropped. The polymerization reaction was carried out for 6 hours, with the start of dropping as the polymerization start time. After completion of the polymerization, the polymerization reaction solution was cooled to 30 ° C. or lower by water cooling, and then the mixture was added to 2,000 g of methanol to filter off the precipitated white powder. The filtered white powder was dispersed in 400 g of methanol to form a slurry, washed and filtered twice, and then vacuum dried at 50 ° C. for 17 hours to obtain a polymer of the white powder (P-). 2) was obtained. The Mw of the polymer (P-2) was 20,070, and the Mw / Mn was 1.28. As a result of ¹³ C-NMR analysis, the content ratios of the structural units derived from styrene, the structural units derived from tetrahydrofurfuryl methacrylate and the structural units derived from 2,2,2-trifluoroethyl methacrylate were 34.7, respectively. It was mol%, 34.4 mol% and 30.9 mol%.

<Preparation of composition for self-assembled monolayer formation>
The components used in the preparation of the self-assembled monolayer formation composition are shown below.

[[A] Polymer]
A-1: Polymer (P-1) synthesized in the above synthesis example 1.

[[B] Solvent]
B-1: Propylene glycol monomethyl ether acetate B-2: Butyl acetate B-3: Cyclohexanone B-4: Ethyl lactate B-5: Cyclopentanone B-6: Diisoamyl ether

[[C] Polymer]
C-1: Polymer (P-2) synthesized in Synthesis Example 2 above.

[Example 1] (Preparation of composition for forming a self-assembled monolayer (S-1))
[A] 100 parts by mass of (A-1) as a polymer, 370 parts by mass of (B-1) and (B-2) 197 parts by mass as a solvent of [B] are mixed and dissolved to prepare a mixed solution. Obtained. The obtained mixed solution was filtered through a membrane filter having a pore size of 0.01 μm to prepare a composition for forming a self-assembled monolayer (S-1).

[Examples 2 to 6 and Comparative Examples 1 to 4]
The self-assembled monolayer forming compositions (S-2) to (S-6) and (CS-) were operated in the same manner as in Example 1 except that the components of the types and blending amounts shown in Table 1 below were used. 1)-(CS-4) were prepared.

[Evaluation of coating defect performance]
Using each of the self-assembled monolayer forming compositions prepared above, a coating film having a film thickness of 40 nm was formed on the surface of a 12-inch silicon wafer, and firing was performed at 100 ° C. for 60 seconds. The number of defects was measured by performing a defect inspection with a defect inspection device (“KLA2810” manufactured by KLA-Tencor) on the substrate on which the obtained film was formed. The defect suppression property was evaluated as "◯" when the number of defects was 150 or less per wafer, and "x" when the number of defects exceeded 150. The results are shown in Table 2.

<Pattern formation method>
A composition for forming an underlayer film containing a cross-linking agent is spin-coated on a 12-inch silicon wafer using a spin coater (“CLEAN TRACK ACT12” by Tokyo Electron Limited), and then baked at 150 ° C. for 60 seconds to form a film thickness. A 30 nm underlayer film was formed. Next, an ArF resist composition containing an acid dissociative polymer, a photoacid generator and an organic solvent was spin-coated on this underlayer film, and then prebaked (PB) at 100 ° C. for 60 seconds to a film thickness of 90 nm. A resist film was formed. Then, using an ArF immersion exposure apparatus (Nikon's "NSR S610C"), exposure was performed via a mask pattern under optical conditions of NA; 1.3, CrossPole, σ = 0.8 / 1. Then, PEB was performed at 150 ° C. for 60 seconds, then developed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. for 30 seconds, washed with water, and dried to obtain a line-and-space pattern having a line width of 100 nm. I got a pre-pattern. Next, this pre-pattern was irradiated with ultraviolet rays of 193 nm under the condition of 20 mJ / cm ² , and then baked at 210 ° C. for 2 minutes to obtain an evaluation substrate.

Next, each self-assembled monolayer forming composition was applied onto the evaluation substrate so as to have a thickness of 40 nm, and heated at 200 ° C. for 5 minutes for phase separation to form a microdomain structure. Furthermore, the methyl methacrylate phase is removed by irradiating with radiation of 193 nm at 20 mJ / cm ² and immersing it in a solution of methyl isobutyl ketone (MIBK) / 2-propanol (IPA) = 2/8 (mass ratio) for 30 minutes. And formed a pattern.

[Good pattern]
The formed pattern was observed using a scanning electron microscope (“S-4800” manufactured by Hitachi, Ltd.), and the goodness of the pattern was evaluated. The goodness of the formed pattern is "○ (good)" when the pattern can be confirmed and there are no defects (dislocation, bridge, missing line, etc.), and when the pattern formation is incomplete or defective. Was evaluated as "x (defective)". The evaluation results are shown in Table 2.

[Solubility parameter]
The measurement was carried out by the method described in the section of composition (II). The difference between the solubility parameter of the polymer [A] and the solubility parameter of the solvent [B] is shown in Table 2 as Δσ. The absolute value of Δσ is used for the actual evaluation.

As is clear from the results in Table 2, according to the composition for forming a self-assembled monolayer of the example, it is possible to form a coating film in which defects during coating are suppressed, and as a result, the formed pattern is formed. There are few defects and defects, and a phase-separated structure by self-assembly can be formed well. On the other hand, in the composition for forming a self-assembled film of the comparative example, the number of defects at the time of application is high, and probably due to this, the phase separation defects and defects of the formed pattern also increase, and the phase due to self-assembly is increased. It can be seen that the separated structure cannot be formed well.

According to the self-assembling composition and the pattern forming method of the present invention, it is possible to form a uniform coating film without residue defects in order to form a phase-separated structure by self-assembling well. Therefore, these can be suitably used for a lithography process in manufacturing various electronic devices such as semiconductor devices and liquid crystal devices, which are required to be further miniaturized.

101 Substrate 102 Coating film 103 Self-assembled film 103a Block phase (I)
103b block phase (II)
104 [C] Region where polymer is unevenly distributed 105 Underlayer film 106 Pre-pattern

Claims (12)

1. It contains a first polymer containing a first polymerized chain and a second polymerized chain different from the first polymerized chain, and a solvent.
   A composition for forming a self-assembled monolayer, wherein the solvent is a mixture of two or more kinds of solvents selected from the group consisting of an ester solvent and a ketone solvent.
2. The composition for forming a self-assembled monolayer according to claim 1, wherein the solvent is a mixed solvent of two kinds of the ester solvent and the ketone solvent.
3. The composition for forming a self-assembled monolayer according to claim 1 or 2, wherein the ketone solvent is a cyclic ketone solvent.
4. The composition for forming a self-assembled monolayer according to claim 3, wherein the cyclic ketone solvent has 5 to 8 ring members.
5. The composition for forming a self-assembled monolayer according to any one of claims 1 to 4, wherein the ester solvent is a chain ester solvent.
6. The composition for forming a self-assembled monolayer according to claim 5, wherein the chain ester solvent further contains an ether bond.
7. When the solvent contains both the ester solvent and the ketone solvent, the ratio of the ketone solvent to the total mass of the ester solvent and the ketone solvent is 10% by mass or more and 90% by mass or less. The composition for forming a self-assembling film according to any one of claims 1 to 6.
8. It contains a first polymer containing a first polymerized chain and a second polymerized chain different from the first polymerized chain, and a solvent.
   A composition for forming a self-assembled monolayer, wherein the absolute value of the difference between the solubility parameter P of the first polymer and the solubility parameter S of the solvent is 0.35 or less.
9. The composition for forming a self-assembled monolayer according to claim 8, wherein the solvent is a mixture of a plurality of kinds of solvents having different solubility parameters.
10. The self-assembling film forming composition according to claim 8 or 9, wherein the solvent is a mixture of a solvent having a solubility parameter S1 larger than the solubility parameter P and a solvent having a solubility parameter S2 smaller than the solubility parameter P. thing.
11. The composition for forming a self-assembled monolayer according to any one of claims 1 to 10, further comprising a second polymer having a smaller surface free energy than the first polymer.
12. A step of applying the composition for forming a self-assembled monolayer according to any one of claims 1 to 11 on a substrate to form a coating film.
    A pattern forming method comprising a step of phase-separating the coating film to form a self-assembled monolayer and a step of removing a part of the phase of the self-assembled monolayer.
    

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