WO2016133115A1 - Self-organized-film forming method, pattern forming method, and self-organized-film forming composition - Google Patents

Abstract

The present invention relates to a self-organized-film forming method comprising a step for forming a coating film on a substrate by using a self-organized-film forming composition that contains a solvent and at least one type of a first polymer that can form a phase-separated structure through self-organization, wherein the solvent contains an aromatic-ring-containing compound. It is preferred that self-organized-film forming method further comprise a step for heating the coating film. It is preferred that the solvent contain the aromatic-ring-containing compound at 80 mass% or less and 50 mass% or more. It is preferred that the self-organized-film forming composition further contain a second polymer having smaller surface free energy than the first polymer and that the second polymer be unevenly distributed above the self-organized film.

Description

Method for forming self-assembled film, method for forming pattern, and composition for forming self-assembled film

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

With the miniaturization of various electronic device structures such as semiconductor devices and liquid crystal devices, pattern miniaturization is required in the pattern formation process. At present, it is possible to form a fine pattern with a line width of about 50 nm using, for example, an ArF excimer laser, but further fine pattern formation has been required.

In response to the above requirements, a method of forming a self-organized pattern using a so-called self-organized phase separation (microdomain) structure that spontaneously forms an ordered pattern has been proposed. As a method for forming such a self-assembled pattern, an ultrafine pattern is formed by self-assembly using a block copolymer obtained by copolymerizing a monomer compound having one property and a monomer compound having a different property. There are known methods for forming (see JP 2008-149447 A, JP 2002-519728 A and JP 2003-218383 A). According to this method, by annealing the film containing the block copolymer, a structure can be formed in a self-aligned manner in order to arrange the structures having the same properties so as to gather together. Also known is a method of forming a fine pattern by self-organizing a composition containing a plurality of polymers having different properties (US Patent Application Publication No. 2009/0214823 and JP 2010-58403 A). (See the publication).

However, in the above conventional technique, the phase separation structure formed by self-organization is not sufficiently good, and the coating property is not sufficient, so that the occurrence of defects in the formed self-assembled film is suppressed. There is an inconvenience that can not be done.

JP 2008-149447 A JP-T-2002-519728 JP 2003-218383 A US Patent Application Publication No. 2009/0214823 JP 2010-58403 A

The present invention has been made based on the above circumstances, and an object thereof is to provide a method for forming a self-assembled film that can form a self-assembled film with few defects.

The invention made in order to solve the above problems includes one or more first polymers (hereinafter also referred to as “[A] polymers”) and a solvent (hereinafter referred to as “a polymer”) that can form a phase separation structure by self-assembly. , A process for forming a coating film on a substrate (hereinafter, referred to as “composition (I)”) (hereinafter also referred to as “composition (I)”). A coating film forming step), and the [B] solvent includes an aromatic ring-containing compound (hereinafter also referred to as “[B1] compound”).

Another invention made in order to solve the above problems includes a method of forming the self-assembled film and a step of removing a part of the phase of the self-assembled film (hereinafter also referred to as “removing step”). It is the pattern formation method provided.

Still another invention made in order to solve the above-mentioned problems contains one or a plurality of [A] polymers capable of forming a phase-separated structure by self-assembly, and [B] a solvent. B] The composition for forming a self-assembled film, wherein the solvent contains a [B1] compound, and the content of the [B1] compound in the [B] solvent is 50% by mass or more.

Here, “Directed Self Assembly” refers to a phenomenon in which an organization or structure is spontaneously constructed without being caused only by control from an external factor.

According to the method for forming a self-assembled film and the composition for forming a self-assembled film of the present invention, a self-assembled film with few defects can be formed. According to the pattern forming method of the present invention, a pattern having a good shape can be formed using such a self-assembled film with few defects. Therefore, they can be suitably used in pattern formation processes in the manufacture of various electronic devices such as semiconductor devices and liquid crystal devices that are required to be further miniaturized.

In the formation method of the self-organization film of the present invention, it is a mimetic diagram showing an example of a state after forming a coating film on a substrate. In the formation method of the self-organization film of the present invention, it is a mimetic diagram showing an example of the state after forming the self-assembly film. In the pattern formation method of this invention, it is a schematic diagram which shows an example of the state after forming a lower layer film | membrane on a board | substrate. In the pattern formation method of this invention, it is a schematic diagram which shows an example of the state after forming a pre pattern on a lower layer film. In the pattern formation method of this invention, it is a schematic diagram which shows an example of the state after forming a coating film in the area | region on the lower layer film pinched | interposed by the pre pattern. In the pattern formation method of this invention, it is a schematic diagram which shows an example of the state after forming a self-organization film | membrane in the area | region on the lower layer film pinched | interposed by the pre pattern. In the pattern formation method of this invention, it is a schematic diagram which shows an example of the state after removing the one part phase and pre pattern of a self-organization film | membrane.

Hereinafter, embodiments of the method for forming a self-assembled film, the pattern forming method, and the composition for forming a self-assembled film of the present invention will be described in detail.

<Method for forming self-assembled film>
The method for forming a self-assembled film includes a coating film forming step, and the coating film in the coating film forming step is formed from the composition (I). According to the method for forming a self-assembled film, it is possible to form a self-assembled film having a regular array structure with few defects. The reason why the method for forming a self-assembled film has the above-described configuration is not necessarily clear, but for example, the [B] solvent contains a [B1] compound having a specific structure, so that phase separation is achieved. Is better performed.

The formation method of the self-assembled film preferably further includes a step of heating the coating film (hereinafter also referred to as “heating step”). Moreover, you may provide the process (henceforth a "stationary process") which leaves the said coating film before the said heating process or simultaneously with the said heating process.

Examples of the phase separation structure formed by the method for forming a self-assembled film include a sea-island structure, a cylinder structure, a co-continuous structure, and a lamella structure. The phase separation structure formed by the method for forming the self-assembled film may be partial. Hereinafter, it demonstrates, referring drawings for the order of each process and composition (I).

[Coating film forming process]
This step is a step of forming a coating film 102 on the substrate 101 as shown in FIG. The coating film 102 is formed from a composition (I) described later. Examples of the substrate 101 include conventionally known ones such as a silicon wafer, silicon dioxide, and a wafer coated with aluminum. Further, as will be described later, a lower layer film and / or a pre-pattern may be formed on the substrate. Examples of the method for forming the coating film 102 include spin coating, cast coating, and roll coating.

The lower limit of the average thickness of the coating film 102 to be formed is not particularly limited, but is preferably 0.2 nm, more preferably 1 nm, still more preferably 2 nm, and particularly preferably 10 nm. The upper limit of the average thickness of the coating film 102 is not particularly limited, but is preferably 1,000 nm, more preferably 200 nm, still more preferably 120 nm, and particularly preferably 70 nm.

[Standing process]
This step is a step of allowing the coating film 102 formed in the coating film forming step to stand still. “Leave the coating film still” means that the state of the coating film is maintained and is not moved. The method for forming the self-assembled film can form a better phase separation structure by including this step. In this step, as long as the coating film maintains the state of the coating film, part or all of the [B] solvent may evaporate from the coating film.

The lower limit of the standing time is preferably 1 minute, more preferably 3 minutes, and even more preferably 5 minutes. By setting the above time to the above lower limit or more, a better phase separation structure can be formed, and as a result, a self-assembled film with fewer defects in the ordered arrangement structure can be formed. The upper limit of the time is preferably 120 minutes, more preferably 60 minutes, further preferably 30 minutes, and particularly preferably 20 minutes from the viewpoint of productivity.

The method for forming the self-assembled film may further include a step of removing the solvent from the coating film (hereinafter also referred to as “solvent removing step”) after the standing step. Examples of the method for performing the solvent removal step include a heating method.

[Heating process]
This step is a step of heating the coating film 102. This step may be performed in any of the coating film forming step, the standing step, and the solvent removing step, but is preferably performed in the standing step. In the method for forming the self-assembled film, a better phase separation structure can be formed by performing this step in the stationary step.

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

The lower limit of the temperature of the heating step is preferably 40 ° C, more preferably 100 ° C, further preferably 150 ° C, and particularly preferably 200 ° C. As an upper limit of the temperature of the said heating process, 300 degreeC is preferable, 280 degreeC is more preferable, 260 degreeC is further more preferable, 240 degreeC is especially preferable. By setting the temperature of the heating step in the above range, a better phase separation structure can be formed.

The lower limit of the heating step time is preferably 1 minute, more preferably 3 minutes, and even more preferably 5 minutes. The upper limit of the time is preferably 120 minutes, more preferably 60 minutes, still more preferably 30 minutes, and particularly preferably 20 minutes. By setting the time in the above range, a better phase separation structure can be formed.

The self-assembled film 103 is formed by forming a phase separation structure from the coating film 102. When the composition (I) contains a [C] polymer, which will be described later, as shown in FIG. 2, for example, the [C] polymer is unevenly distributed above the self-assembled film 103 to form the region 104, A] The polymer is phase-separated in a substantially vertical direction to form a self-assembled film 103.

The lower limit of the average thickness of the self-assembled film 103 is not particularly limited, but is preferably 0.1 nm, more preferably 0.5 nm, still more preferably 1 nm, and particularly preferably 10 nm. The upper limit of the average thickness of the self-assembled film 103 is not particularly limited, but is preferably 500 nm, more preferably 100 nm, still more preferably 60 nm, and particularly preferably 40 nm.

[Annealing process]
The method for forming the self-assembled film may include a step of annealing the formed self-assembled film 103 in order to improve the phase separation structure of the self-assembled film 103. Examples of the annealing method include a method of heating with an oven, a hot plate, or the like. As a minimum of the above-mentioned heating temperature, 80 ° C is preferred, 100 ° C is more preferred, and 150 ° C is still more preferred. As an upper limit of the said heating temperature, 400 degreeC is preferable, 350 degreeC is more preferable, and 300 degreeC is further more preferable. The lower limit of the heating time is usually 30 seconds, preferably 1 minute, more preferably 2 minutes, and even more preferably 3 minutes. The upper limit of the heating time is preferably 120 minutes, more preferably 90 minutes, and even more preferably 60 minutes.

<Composition (I)>
The composition (I) contains a [A] polymer and a [B] solvent. In addition to the [A] polymer and the [B] solvent, the composition (I) is a second polymer having a surface free energy smaller than that of the [A] polymer (hereinafter also referred to as “[C] polymer”). Other components such as a surfactant 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 separation structure by self-assembly. [A] The polymer is preferably composed of only one type of block copolymer (hereinafter also referred to as “[A1] block copolymer”). [A] The polymer is preferably composed of a plurality of types of polymers (hereinafter also referred to as “[A2] polymer”).

([A1] block copolymer)
[A1] The block copolymer is a polymer having a structure in which a plurality of blocks are bonded. Each of the blocks is composed of a chain structure of structural units derived from one type of monomer. In the [A1] block copolymer having such a plurality of blocks, the same type of blocks are aggregated by heating or the like to form a phase composed of the same type of blocks. At this time, since 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.

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

Examples of the block include a polystyrene block, a poly (meth) acrylate block, a polyvinyl acetal block, a polyurethane block, a polyurea block, a polyimide block, a polyamide block, an epoxy block, a novolac type phenol block, and a polyester block.

From the viewpoint of easy formation of the phase separation structure and easy removal of the phase, the [A1] block copolymer is preferably a polymer comprising a polystyrene block and a poly (meth) acrylate block.

[A1] When the block copolymer is a diblock copolymer, the mass ratio ((A) / (B)) of the content ratio of the two types of structural units (A) and (B) constituting the block copolymer is as follows: The line / space width ratio of the desired line space pattern, the size of the contact hole, and the like can be selected as appropriate. From the viewpoint of forming a fine and good phase separation structure, when forming a lamellar structure, the lower limit of the above (A) / (B) is preferably 35/65, more preferably 40/60. In the case of forming a lamella structure, the upper limit of the above (A) / (B) is preferably 65/35, more preferably 60/40. Further, from the viewpoint of forming a fine and good phase separation structure, when the cylinder structure is formed, the lower limit of (A) / (B) is preferably 65/35. When the cylinder structure is formed, the upper limit of the above (A) / (B) is preferably 85/15, more preferably 75/25.

([A1] Method for synthesizing block copolymer)
[A1] The block copolymer can be synthesized by forming the blocks in a desired order by living anion polymerization, living radical polymerization, or the like. For example, a polystyrene block, a poly (meth) acrylic acid ester block, other blocks other than these and the like are connected while being polymerized in a desired order, and then synthesized by adding methanol or the like to stop the polymerization.

For example, when synthesizing a block copolymer [A1] which is a diblock copolymer composed of a polystyrene block and a poly (meth) acrylate block, styrene is first used in an appropriate solvent using an anionic polymerization initiator. A polystyrene block is synthesized by polymerizing. Next, it connects with a polystyrene block, (meth) acrylic acid ester is similarly polymerized, and a poly (meth) acrylic acid ester block is synthesize | combined. Thereafter, 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 cause 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 and methyl propionate;
Ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone;
And ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes and the like. These solvents may be used alone or in combination of two or more.

The reaction temperature in the above polymerization may be appropriately determined according to the type of anionic polymerization initiator. The lower limit of the reaction temperature in the polymerization is usually −150 ° C., preferably −80 ° C. As an upper limit of the reaction temperature in the said superposition | polymerization, it is 50 degreeC normally and 40 degreeC is preferable. The lower limit of the reaction time in the polymerization is usually 5 minutes, preferably 20 minutes, and more preferably 1 hour. The upper limit of the reaction time in the polymerization is usually 24 hours, preferably 12 hours, and more preferably 6 hours.

Examples of the anionic polymerization initiator used for the polymerization include alkyl lithium, alkyl magnesium halide, sodium naphthalene, alkylated lanthanoid compounds, and the like. Among these, when polymerizing using styrene and / or (meth) acrylic acid ester as a monomer, it is preferable to use an alkyl lithium compound.

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

Examples of the terminal treating agent containing a hetero atom 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, pyrazone, imine, azocarboxylic acid ester, aminostyrene, vinyl Nitrogen-containing compounds such as pyridine, aminoacrylate, aminodiphenylethylene, and imide compounds;
Silane compounds such as alkoxy silane, amino silane, ketino silane, isocyanate silane, siloxane, glycidyl silane, mercapto silane, vinyl silane, epoxy silane, pyridyl silane, piperazyl silane, pyrrolidone silane, cyano silane, isocyanate silane;
Examples thereof include tin halide, silicon halide, carbon dioxide and the like.

[A1] The block copolymer synthesized by the above polymerization is preferably recovered by a reprecipitation method. That is, after the polymerization reaction, the target copolymer is recovered as a powder by introducing the reaction solution into a reprecipitation solvent. As the reprecipitation solvent, alcohols or alkanes can be used alone or in admixture 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 lower limit of the weight average molecular weight (Mw) by gel permeation chromatography (GPC) of the block copolymer is preferably 1,000, more preferably 8,000, still more preferably 20,000, 000 is particularly preferred. [A1] The upper limit of the Mw of the block copolymer is preferably 150,000, more preferably 100,000, still more preferably 80,000, and particularly preferably 70,000. [A1] By setting the Mw of the block copolymer within the above range, a more favorable phase separation structure can be formed.

[A1] The lower limit of the ratio (Mw / Mn) between the Mw and the number average molecular weight (Mn) of the block copolymer is usually 1. [A1] The upper limit of Mw / Mn of the block copolymer is usually 5, preferably 3, more preferably 2, more preferably 1.5, and particularly preferably 1.2. [A1] By setting Mw / Mn of the block copolymer in the above range, a better phase separation structure can be formed.

Mw and Mn are Tosoh GPC columns ("G2000HXL", "G3000HXL" and "G4000HXL"), eluent: tetrahydrofuran (Wako Pure Chemical Industries, Ltd.), flow rate: 1.0 mL / Min, sample concentration: 1.0% by mass, sample injection amount: 100 μL, column temperature: measured by GPC using a differential refractometer as a detector and a monodisperse polystyrene as a standard under the analysis conditions of 40 ° C. It is.

([A2] polymer)
[A2] The polymer comprises a plurality of types of polymers. When the [A2] polymer having such a plurality of types of polymers is dissolved in an appropriate solvent, the same types of polymers aggregate to form a phase composed of the same types of polymers. At this time, the layers formed from different types of polymers do not mix with each other, so it is presumed that a phase-separated structure having an ordered pattern in which different phases are periodically repeated alternately can be formed. .

[A2] The polymer can contain two or more kinds of polymers depending on the desired phase separation structure, but two kinds are preferred. [A2] As a polymer constituting the polymer, for example, an acrylic polymer, a styrene polymer, a vinyl acetal polymer, a urethane polymer, a urea polymer, an imide polymer, an amide polymer, Examples thereof include novolak type phenol polymers and ester polymers. The polymer may be a homopolymer synthesized from one type of monomer or a copolymer synthesized from a plurality of types of monomers. [A2] The polymer preferably includes a styrene polymer and an acrylic polymer, and more preferably includes only a styrene polymer and an acrylic polymer.

[A2] When the polymer is composed of two types of polymers, the lower limit of the mass ratio of each polymer in the [A2] polymer is preferably 10/90, more preferably 20/80, and further 30/70 preferable. [A2] The upper limit of the mass ratio of each polymer in the polymer is preferably 90/10, more preferably 80/20, and even more preferably 70/30. [A2] By setting the mass ratio of each polymer in the polymer within the above range, a better phase separation structure can be formed.

([A2] Polymer Synthesis Method)
[A2] Each polymer in the polymer is obtained by polymerizing, for example, a monomer corresponding to each predetermined structural unit in a suitable polymerization reaction solvent using a polymerization initiator such as a radical polymerization initiator. Can be manufactured. Examples of the polymer synthesis method include a method in which a solution containing a monomer and a polymerization initiator is dropped into a polymerization reaction solvent or a solution containing a monomer to cause a polymerization reaction, a solution containing the monomer and a polymerization A method in which a solution containing an initiator is dropped into a polymerization reaction solvent or a solution containing a monomer separately to cause a polymerization reaction, a plurality of types of solutions containing each monomer, and a solution containing a polymerization initiator And a method in which a polymerization reaction is carried out by dropping them into a solution containing a polymerization reaction solvent or a monomer.

Examples of the radical polymerization initiator include azobisisobutyronitrile (AIBN), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2-cyclopropylpropylene). Pionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), azo radical polymerization initiators such as dimethyl 2,2′-azobisisobutyrate; benzoyl peroxide, t-butyl hydroperoxide And peroxide radical polymerization initiators such as cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical polymerization initiators can be used alone or in combination of two or more.

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

The lower limit of the reaction temperature in the polymerization is usually 40 ° C., and preferably 50 ° C. As an upper limit of the reaction temperature in the said superposition | polymerization, it is 150 degreeC normally and 120 degreeC is preferable. The lower limit of the reaction time in the polymerization is usually 1 hour. The upper limit of the reaction time in the polymerization is usually 48 hours, preferably 24 hours.

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

The lower limit of Mw of each polymer in the [A2] polymer is not particularly limited, but is preferably 3,000, more preferably 5,000, still more preferably 7,000, and particularly preferably 8,000. The upper limit of the Mw of the polymer is not particularly limited, but is preferably 50,000, more preferably 30,000, still more preferably 20,000, and particularly preferably 15,000. By making Mw of the said polymer into the said range, a finer pattern can be obtained from composition (I) and the rectangularity of a pattern also improves. There exists a possibility that the heat resistance of a self-organization film | membrane may fall that Mw of the said polymer is less than the said minimum. If the Mw of the polymer exceeds the upper limit, a sufficiently fine pattern may not be obtained.

[A2] The lower limit of Mw / Mn of each polymer in the polymer is usually 1. The upper limit of Mw / Mn of the polymer is usually 5, preferably 3 and more preferably 2.

[A] The lower limit of the content of the polymer is preferably 70% by mass, more preferably 80% by mass, still more preferably 90% by mass, and 95% by mass with respect to the total solid content of the composition (I). Particularly preferred.

[[B] solvent]
[B] The solvent contains a [B1] compound. [B] The solvent may contain a solvent other than the compound [B1] as long as the effects of the present invention are not impaired. As a minimum of content of [B] solvent in composition (I), 50 mass% is preferred, 75 mass% is more preferred, 90 mass% is still more preferred, 95 mass% is especially preferred, and 98 mass% is still more. Particularly preferred.

([B1] compound)
The compound [B1] is a compound having an aromatic ring, and is preferably a solvent having a boiling point at 1 atm of 150 ° C. to 300 ° C. and a surface tension at 25 ° C. of 29 mN / m to 60 mN / m.

The lower limit of the content of the [B1] compound in the [B] solvent is preferably 30% by mass, more preferably 50% by mass, further preferably 55% by mass, and particularly preferably 60% by mass. The upper limit of the content is preferably 99.9% by mass, more preferably 99% by mass, still more preferably 90% by mass, particularly preferably 80% by mass, still more particularly preferably 75% by mass, and most preferably 70% by mass. preferable. According to the method for forming a self-assembled film, when the [B] solvent contains the [B1] compound in a content in the above range, a self-assembled film with fewer defects in the ordered arrangement structure can be formed. .

Examples of the aromatic ring include a benzene ring and a naphthalene ring, and a benzene ring is particularly preferable.

[B1] As the compound, for example, an ether solvent such as anisole, phenylethyl ether, tolylmethyl ether;
Hydrocarbon solvents such as isopropylbenzene, t-butylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene;
Ketone solvents such as phenyl methyl ketone and phenyl ethyl ketone;
Ester solvents such as phenyl formate, phenyl acetate and methyl benzoate;
Amide solvents such as N, N-dimethylbenzoic acid amide and N-methyl-N-phenylformamide;
Aprotic polar solvents such as phenylmethyl sulfoxide, benzonitrile;
Alcohol solvents such as propylene glycol monophenyl ether, benzyl alcohol, phenylethyl alcohol, naphthylmethyl alcohol;
Examples include Ipsol 100 and Ipsol 150 (a mixed solvent containing aromatic hydrocarbon as a main component, Idemitsu Kosan Co., Ltd.).

Among these, [B1] compounds are preferably ether solvents, hydrocarbon solvents and alcohol solvents, such as anisole, isopropylbenzene, t-butylbenzene, trimethylbenzene, propylene glycol monophenyl ether and combinations thereof. More preferred are anisole, 1,3,5-trimethylbenzene and combinations thereof. [B1] A compound can be used individually by 1 type or in combination of 2 or more types.

[B1] The lower limit of the solubility parameter (SP value) of the compound is preferably 8 (cal / cm ³ ) ^1/2, more preferably 8.3 (cal / cm ³ ) ^1/2 , and 8.5 (cal / Cm ³ ) ^1/2 is more preferable. On the other hand, the upper limit of the SP value of the [B1] compound is preferably 15 (cal / cm ³ ) ^1/2, more preferably 13 (cal / cm ³ ) ^1/2 , and 12.5 (cal / cm ³ ). ^1/2 is more preferable. Thus, by setting the SP value of the [B1] compound within the above range, the compatibility between the [B1] compound and the [A] polymer can be improved. B1] Since it can be heated while further suppressing the evaporation of the compound, a better phase separation structure can be formed.

The “SP value” is calculated by the method proposed by Fedors et al. Specifically, it can be calculated by the method described in “POLYMER ENGINEERING AND SCIENCE, FEBRUARY, 1974, Vol. 14, No. 2, ROBERT F. FEDORS. (Pages 147 to 154)”.

The lower limit of the viscosity of the [B1] compound at 25 ° C. is preferably 1 mPa · s, more preferably 1.3 mPa · s, and even more preferably 1.5 mPa · s. The upper limit of the viscosity is preferably 20 mPa · s, more preferably 10 mPa · s, further preferably 5 mPa · s, and particularly preferably 3 mPa · s. Thus, a more favorable phase-separation structure can be formed by making the said viscosity into the said range.

[B] The solvent may contain a solvent other than the [B1] compound.

The other solvent is a compound having no aromatic ring, and examples thereof include ketone solvents, ester solvents, amide solvents, aprotic polar solvents, alcohol solvents and the like.

As other solvents, specifically,
Ketone solvents such as cyclohexanone and cycloheptanone;
lactone solvents such as γ-butyrolactone;
Alkylene glycol diacetate solvents such as propylene glycol diacetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, and 1,6-hexanediol diacetate;
Alkylene glycol monoalkyl ether acetate solvents such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate;
Dialkylene glycol monoalkyl ether acetates such as diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate;
Ester solvents such as cyclohexanol acetate and triacetin;
Amide solvents such as N, N-dimethylformamide;
Sulfoxide solvents such as dimethyl sulfoxide;
Examples include alcohol solvents such as 1,3-butylene glycol, diethylene glycol monoethyl ether, tripropylene glycol methyl ether, and tripropylene glycol n-butyl ether.

Among these, among these, an alkylene glycol monoalkyl ether acetate solvent is preferable, and propylene glycol monomethyl ether acetate is more preferable.

[B] When the solvent contains another solvent, the lower limit of the content of the other solvent in the [B] solvent is preferably 0.1% by mass, more preferably 1% by mass, further preferably 10% by mass, 20% by weight is particularly preferred, 25% by weight is more particularly preferred, and 30% by weight is most preferred. As an upper limit of the said content, 70 mass% is preferable, 50 mass% is more preferable, 45 mass% is further more preferable, 40 mass% is especially preferable. According to the method for forming a self-assembled film, the [B] solvent contains other solvent in a content within the above range, thereby ensuring good filterability of the composition for forming a self-assembled film. A self-assembled film with fewer defects in the arrangement structure can be formed.

[Other ingredients]
[[C] polymer]
The [C] polymer is a polymer having a surface free energy smaller than that of the [A] polymer. As shown in FIG. 1, when the coating film 102 is formed from the composition (I) containing the [C] polymer, the surface free energy of the [C] polymer is smaller than that of the [A] polymer. The [C] polymer is considered to be unevenly distributed in the upper region in the coating film 102 during the self-assembly process. Moreover, it is thought that the [B1] compound in the coating film 102 promotes uneven distribution of the [C] polymer in the upper region. Due to the interaction between the [C] polymer unevenly distributed in the upper region in the coating film 102 and the [A] polymer present in the region other than the upper region, the phase separation of the [A] polymer proceeds better. Thus, a self-assembled film 103 having a better phase separation structure can be formed, and as a result, a self-assembled film with fewer defects in a regular arrangement structure can be obtained. As described above, the reason why the phase separation is improved by the [C] polymer is not necessarily clear. For example, when the [C] polymer is not applied, the difference in surface free energy between the atmosphere and the [A] polymer is Although it tends to promote phase separation in a substantially horizontal direction due to its large size, the difference in surface free energy from the [A] polymer is reduced by applying the [C] polymer, so that the substantially horizontal direction is reduced. Since phase separation is suppressed, it can be considered that phase separation in a substantially vertical direction is effectively performed as a result. Finally, as shown in FIG. 2, the [C] polymer is unevenly distributed in the region 104 above the self-assembled film 103.

The surface free energy of each polymer is determined by, for example, forming a thin film of each polymer by, for example, spin-coating a solution of each polymer and then heating, and the documents “JOURNAL OF APPLIED POLYMER SCIENCE VOL.13, PP.1741- 1747 (1969) ". K. According to the method of OWENS et al., The contact angle of liquid such as pure water and methylene iodide on the thin film is measured, and can be obtained from the measured value using the relationship of the following formula (X) and the following formula (Y). .

(1 + cos θ) × 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 _S ^p : polar component of surface free energy of polymer, γ _L : surface free energy of liquid, γ _L ^d : dispersion component of surface free energy of liquid, γ _L ^p : polar component of surface free energy of liquid, θ: contact angle)

[A] The lower limit of the value obtained by subtracting the surface free energy of the polymer [C] from the surface free energy of the polymer is preferably 1 mN / m, more preferably 3 mN / m, still more preferably 5 mN / m, and 7 mN / m. m is particularly preferable, and 9 mN / m is further particularly preferable. [A] The upper limit of the value obtained by subtracting the surface free energy of the [C] polymer from the surface free energy of the polymer is preferably 20 mN / m, more preferably 18 mN / m, still more preferably 15 mN / m, and 13 mN / m. m is particularly preferable, and 11 mN / m is further particularly preferable. By making the surface free energy difference in 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 increased. It is considered that the self-assembled film can be more effectively improved. As a result, a self-assembled film with fewer defects in the ordered arrangement structure can be obtained.

[C] The 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. As a minimum of the content rate of the said structural unit (I), 10 mol% is preferable with respect to all the structural units which comprise a [C] polymer, 14 mol% is more preferable, 18 mol% is further more preferable, 22 Mole% is particularly preferred. As an upper limit of the content rate of the said structural unit (I), 50 mol% is preferable with respect to all the structural units which comprise a [C] polymer, 45 mol% is more preferable, 40 mol% is further more preferable, 36 Mole% is particularly preferred. By making the content rate of the said structural unit (I) into the said range, uneven distribution of the above-mentioned [C] polymer and interaction with a [C] polymer and a [A] polymer are improved more effectively. be able to.

[C] The 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 acid adamantyl, 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 possessed by the [C] polymer, it is considered that the interaction with the [A] polymer can be moderately increased. From the viewpoint of forming a better phase separation structure, the [A] polymer It is preferable that at least a part of the structural unit included in [A] is included, and it is more preferable that all the structural units included in the [A] polymer are included. For example, when the [A] polymer is a diblock copolymer of polystyrene block-poly (meth) acrylic acid tetrahydrofurfuryl block, the [C] polymer 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 tetrahydrofurfuryl (meth) acrylate and a structural unit derived from styrene and tetrahydrofurfuryl (meth) acrylate. More preferably.

[C] The polymer is preferably a random copolymer from the viewpoint of more effectively exhibiting the interaction with the [A] polymer and forming a better phase separation structure.

[C] For the polymer, for example, a monomer that gives each structural unit such as the structural unit (I) and the structural unit (II) is used to initiate radical polymerization in the same manner as the above-described method for synthesizing the polymer [A]. It can synthesize | combine by superposing | polymerizing in a suitable solvent using an agent.

The lower limit of the Mw of the [C] polymer is preferably 1,000, more preferably 5,000, still more preferably 8,000, and particularly preferably 10,000. [C] The upper limit of the Mw of the polymer is preferably 100,000, more preferably 60,000, still more preferably 40,000, and particularly preferably 30,000. [C] By setting the Mw of the polymer in the above range, a self-assembled film with fewer defects in the ordered arrangement structure can be formed.

[C] The lower limit of Mw / Mn of the polymer is usually 1 and preferably 1.1. [C] The upper limit of Mw / Mn of the polymer is usually 5, preferably 3, more preferably 2.5, still more preferably 1.8, and particularly preferably 1.5. [C] By setting Mw / Mn of the polymer within the above range, a self-assembled film with fewer defects in the ordered structure can be formed.

[Surfactant]
The composition (I) may further contain a surfactant. Application | coating property to a board | substrate etc. can be improved because composition (I) contains surfactant.

[Method for Preparing Composition (I)]
The composition (I) can be prepared, for example, by mixing the [A] polymer, the [B] solvent, and other components as necessary, and preferably filtering through 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 diameter of about 10 nm.

As a minimum of solid content concentration of composition (I), 0.01 mass% is preferred, 0.1 mass% is more preferred, 0.3 mass% is still more preferred, and 0.5 mass% is especially preferred. As an upper limit of solid content concentration of composition (I), 50 mass% is preferable, 20 mass% is more preferable, 10 mass% is further more preferable, 5 mass% is especially preferable.

The hydrodynamic radius (Rh) of the polymer in the composition (I) is not particularly limited, and the type of [A] polymer used for the preparation of the composition (I) and [B1] in the solvent. It can be set as appropriate depending on the type and content of the compound, but from the viewpoint of ease of preparation of the composition (I), it should be smaller than the pore size of the filter used for filtration during preparation of the composition (I). preferable.

The upper limit of Rh is preferably 30 nm, more preferably 10 nm, still more preferably 8 nm, particularly preferably 7 nm, and particularly preferably 6 nm. The lower limit of Rh is, for example, 4 nm, and preferably 5 nm. Rh of the polymer in the composition (I) can be measured by dynamic light scattering measurement (DLS) or the like.

<Pattern formation method>
The pattern forming method includes the method for forming the self-assembled film and the removing step.

The pattern forming method includes a step of forming a lower layer film on the upper surface side of the substrate (hereinafter also referred to as a “lower layer film forming step”) and / or a coating film forming step in the method for forming the self-assembled film described above. Or you may further provide the process (henceforth a "pre-pattern formation process") which forms a pre pattern in the upper surface side of the said board | substrate.

The pattern forming method may further include a step of removing a pre-pattern (hereinafter, also referred to as “pre-pattern removing step”) after the method of forming the self-assembled film. It is preferable to further include a step of etching the substrate using the pattern as a mask (hereinafter also referred to as “substrate pattern forming step”). Hereinafter, each process will be described with reference to the drawings. The case where the [A] polymer in the composition (I) is the [A1] block copolymer will be described as an example.

[Lower layer formation process]
This step is a step of forming the lower layer film 105 on the upper surface side of the substrate 101. Thereby, as shown in FIG. 3, a substrate with a lower layer film in which the lower layer film 105 is formed on the substrate 101 can be obtained. A self-assembled film 103 described later is formed on the lower layer film 105. The phase separation structure of the self-assembled film 103 is changed by the interaction with the lower layer film 105 in addition to the interaction between the blocks of the [A1] block copolymer contained in the composition (I). By having the lower layer film 105, the structure control may be easier. Further, when the self-assembled film 103 is a thin film, the transfer process can be improved by having the lower layer film 105.

As a composition for forming an 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 crosslinking agent, a thermal acid generator, and the like Is mentioned.

The formation method of the lower layer film 105 is not particularly limited. For example, the lower layer film 105 is formed by applying a composition for forming the lower layer film on the substrate 101 by a known method such as a spin coat method, and then curing by exposure and / or heating. Methods and the like. Examples of radiation used for this exposure include visible light, ultraviolet light, far ultraviolet light, X-rays, electron beams, γ-rays, molecular beams, and ion beams. The lower limit of the heating temperature is not particularly limited, but 90 ° C. is preferable. Although it does not specifically limit as an upper limit of the said heating temperature, 550 degreeC is preferable, 450 degreeC is more preferable, and 300 degreeC is further more preferable. As a minimum of the above-mentioned heating time, 5 seconds are preferred, 10 seconds are more preferred, and 20 seconds are still more preferred. The upper limit of the heating time is preferably 1,200 seconds, more preferably 600 seconds, and even more preferably 300 seconds. The lower limit of the average thickness of the lower layer film 105 is not particularly limited, but is preferably 1 nm, more preferably 2 nm, and further preferably 3 nm. The upper limit of the average thickness of the lower layer film 105 is not particularly limited, but is preferably 20,000 nm, more preferably 1,000 nm, and still more preferably 100 nm.

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

As a method for forming the pre-pattern 106, a method similar to a known resist pattern forming method may be used. Moreover, as a composition used for formation of this pre-pattern 106, it is using conventional resist compositions, such as a composition containing the polymer which has an acid dissociable group, a radiation sensitive acid generator, and an organic solvent. it can. Specifically, for example, a commercially available chemically amplified resist composition is applied onto the substrate 101 or the lower layer film 105 to form a resist film. Next, exposure is performed by irradiating a desired region of the resist film with radiation through a mask having a specific pattern. Examples of the radiation include electromagnetic waves such as ultraviolet rays, far ultraviolet rays, and X-rays; and 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, immersion exposure can be performed as an exposure method. Next, post-exposure baking (PEB) is performed, and development is performed using a developer such as an alkali developer or an organic solvent, so that a desired pre-pattern 106 can be formed. It is preferable that the obtained pre-pattern 106 is further accelerated by heat treatment after irradiation with, for example, 254 nm ultraviolet rays. The lower limit of the heating temperature is, for example, 100 ° C. The upper limit of the heating temperature is usually 200 ° C. The lower limit of the heating time is, for example, 1 minute. The upper limit of the heating time is, for example, 30 minutes.

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

Note that the surface of the pre-pattern 106 may be subjected to a hydrophobic treatment or a hydrophilic treatment. As a specific treatment method, a hydrogenation treatment by exposing to hydrogen plasma for a certain period of time can be cited. By increasing the hydrophobicity or hydrophilicity of the surface of the pre-pattern 106, self-assembly can be further promoted.

(Formation of self-assembled film)
The formation of the self-assembled film is as described in the section of the method for forming the self-assembled film. In the case of using the lower layer film and the prepattern, as shown in FIGS. 5 and 6, the composition (I) is applied to a region on the lower layer film 105 sandwiched between the prepatterns 106 to form the coating film 102. Then, for example, a self-assembled film 103 having a phase separation structure having an interface substantially perpendicular to the substrate 101 is formed on the lower layer film 105 formed on the substrate 101.

When the pre-pattern 106 is included, the phase separation structure of the self-assembled film 103 is preferably formed along the pre-pattern 106, and the interface formed by the phase separation is substantially parallel to the side surface of the pre-pattern 106. Is more preferable. For example, when the block copolymer [A1] is composed of a styrene block and a poly (meth) acrylic acid block and the affinity between the prepattern and the styrene block is high, the phase of the styrene block is linear along the prepattern. Next, a lamellar phase separation structure in which a poly (meth) acrylic acid block phase and a styrene block phase are alternately arranged in this order is formed. The phase separation structure to be formed is composed of a plurality of phases, and the interface formed from these phases is usually substantially vertical, but the interface itself is not necessarily clear. In addition, 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 lower layer film, etc. are precisely controlled to obtain the desired fine structure. A pattern can be obtained.

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

Before the etching process, radiation may be applied as necessary. As the radiation, when the phase to be removed by etching is a polymethyl methacrylate block phase, radiation of 254 nm can be used. Since the polymethyl methacrylate block phase is decomposed by the radiation irradiation, etching becomes easier.

Examples of a method for removing a part of the block phase in the phase separation structure of the self-assembled film 103 include reactive ion etching (RIE) such as chemical dry etching and chemical wet etching; sputter etching and ion beam etching. A known method such as physical etching is used. Of these, reactive ion etching (RIE) is preferable. Among them, chemical dry etching using CF ₄ , O ₂ gas or the like, and chemical wet etching (wet development) using a liquid etching solution such as an organic solvent or 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, methyl n-pentyl ketone, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 4-methyl-2-pentanol And the like. In addition, these solvents may be used independently and may use 2 or more types together.

[Pre-pattern removal process]
This step is a step of removing the pre-pattern 106 as shown in FIGS. By removing the pre-pattern 106, a finer and more complicated pattern can be formed. 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. Moreover, this process may be performed simultaneously with the said removal process, and may be performed before or after a removal process.

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

As the etching method, a method similar to the method in the removing step can be used, and the etching gas and the etching solution can be appropriately selected depending on the material of the lower layer film and the substrate. For example, when the substrate is made of a silicon material, a mixed gas of chlorofluorocarbon gas and SF ₄ can be used. When the substrate is a metal film, a mixed gas of BCl ₃ and Cl ₂ or the like can be used. In addition, the pattern obtained by the said pattern formation method is used suitably for a semiconductor element etc. Furthermore, the said semiconductor element is used also for LED, a solar cell, etc.

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

<Composition for forming self-assembled film>
The composition for forming a self-assembled film of the present invention contains one or more kinds of first polymers capable of forming a phase separation structure by self-assembly and a solvent, and the solvent is an aromatic ring-containing compound. And the content of the aromatic ring-containing compound in the solvent is 50% by mass or more. Since the composition for forming a self-assembled film has been described in the section of the composition (I) of the method for forming the self-assembled film, the description thereof is omitted here.

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

[Mw and Mn]
Mw and Mn of the polymer were measured by GPC using Tosoh's GPC columns (two G2000HXL, one G3000HXL and one G4000HXL) under the following conditions.

Eluent: Tetrahydrofuran (Wako Pure Chemical Industries)
Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Detector: Differential refractometer Standard material: Monodisperse polystyrene

[ ¹ H-NMR analysis]
The ¹ H-NMR analysis for determining the content of each structural unit in the polymer was measured using a nuclear magnetic resonance apparatus (“JNM-EX400” manufactured by JEOL Ltd.).

<Synthesis of [A1] block copolymer>
[Synthesis Example 1] (Block Copolymer (A-1))
After drying the 500 mL flask reaction vessel under reduced pressure, 200 g of tetrahydrofuran that had been subjected to distillation dehydration treatment was injected under a nitrogen atmosphere and cooled to −78 ° C. Thereafter, 0.45 mL of a 1N cyclohexane solution of sec-butyllithium (sec-BuLi) was injected, and 17.7 mL (0.153 mol) of styrene that had been subjected to adsorption filtration on silica gel and subjected to distillation dehydration to remove the polymerization inhibitor. Was added dropwise over 30 minutes to confirm that the polymerization system was orange. At this time, care was taken that the internal temperature of the reaction solution did not exceed -60 ° C. After ripening for 30 minutes after completion of the dropwise addition, 0.11 mL (0.0008 mol) of 1,1-diphenylethylene and 1.08 mL (0.0005 mol) of a lithium chloride / 0.5N tetrahydrofuran solution are added to make the polymerization system dark red. It was. Furthermore, when 8.7 mL (0.0819 mol) of methyl methacrylate, which has been subjected to adsorption filtration with silica gel to remove the polymerization inhibitor and distilled and dehydrated, is added dropwise over 30 minutes, the polymerization system becomes light yellow and reacts for 120 minutes. I let you. Thereafter, 1 mL of methanol was injected as a terminal treating agent to stop the reaction. The temperature of the reaction solution was raised to room temperature, and the resulting reaction solution was concentrated and replaced with methyl isobutyl ketone (MIBK). Then, 1,000 g of a 2% by mass aqueous solution of oxalic acid was injected and stirred. The layer was removed. This operation was repeated three times, and after removing the Li salt, 1,000 g of ultrapure water was injected and stirred, and the lower aqueous layer was removed. After this operation was repeated 3 times to remove oxalic acid, the solution was concentrated and added dropwise to 500 g of methanol to precipitate a polymer. The resin filtered under reduced pressure was washed twice with methanol and then dried under reduced pressure at 60 ° C. to obtain 24.0 g of a white block copolymer (A-1).

Mw of the block copolymer (A-1) was 74,000, and Mw / Mn was 1.05. As a result of ¹ H-NMR analysis, the ratio of the content of styrene units to the content of methyl methacrylate units in the block copolymer (A-1) was 65.2 (mol%) / 34.8 (mol%). )Met. The block copolymer (A-1) is a diblock copolymer and corresponds to PS / PMMA = 66.1 (mass%) / 33.9 (mass%).

<Preparation of composition>
It shows below about the [B] solvent used for preparation of a composition. Note that (B-1) to (B-6) are [B1] compounds.

[[B] solvent]
B-1: Isopropylbenzene B-2: t-butylbenzene B-3: 1,2,4-trimethylbenzene B-4: 1,3,5-trimethylbenzene B-5: Propylene glycol monophenyl ether B-6 : Anisole b-1: Propylene glycol monomethyl ether acetate

[Example 1]
[A] (A-1) as a block copolymer was dissolved in isopropylbenzene to obtain a 1.5 mass% solution. This solution was filtered through a membrane filter having a pore size of 200 nm to prepare a composition for forming a self-assembled film (S-1).

[Examples 2 to 12 and Comparative Example 1]
In Example 1, compositions [S-2] to (S-12) are the same as in Example 1 except that the component [A] is the same and the type of the solvent [B] is changed. And (CS-1) were prepared.

 

<Preparation of composition for forming lower layer film>
A flask equipped with a condenser and a stirrer was charged with 100 g of methyl ethyl ketone and purged with nitrogen. Heat to 85 ° C., and at the same temperature, 100 g of methyl ethyl ketone, 51.0 g (0.49 mol) of styrene, 49.0 g (0.49 mol) of methyl methacrylate, 3.00 g of 3-mercapto-1,2-propanediol (0 (0.027 mol) and 2,2′-azobis (2-methylpropionitrile) (1.00 g, 0.0061 mol) were added dropwise over 3 hours, and polymerization was carried out for 3 hours while maintaining this temperature. The obtained resin solution was purified by precipitation with 3 L of methanol to remove residual monomers, initiators and the like. The obtained resin was Mw = 8,285, Mn = 5,355, Mw / Mn = 1.54. Next, the resin was diluted with propylene glycol monomethyl ether acetate to obtain a 10% by mass resin solution. This is designated as composition (U-1) for forming a lower layer film.

(Formation of lower layer film)
The underlayer film forming composition (U-1) prepared above was applied onto the surface of a 12-inch silicon wafer to form a coating film having an average thickness of 5 nm. Next, the lower layer film was formed by baking at 220 ° C. for 120 seconds.

(Formation of self-assembled film)
(Examples 1 to 12 and Comparative Example 1: When using compositions (S-1) to (S-12) and (CS-1) for forming a self-assembled film)
The prepared composition for forming a self-assembled film is applied on the formed lower layer film so that the average thickness of the coating film becomes 35 nm, and is phase-separated by heating at 220 ° C. for 60 seconds in a nitrogen atmosphere. A self-assembled film in which cylindrical microdomains were arranged perpendicular to the substrate was formed.

<Evaluation>
About the formed self-assembled film and the prepared composition for forming a self-assembled film, the following items were evaluated by the following methods.

[defect]
About the formed self-assembled film, defects were measured with KLA2810 (KLA-Tencor) and observed with a scanning electron microscope (“S-9380” of Hitachi High-Technology Corporation). In addition to defects that lead to phase separation failure, defects corresponding to particles were measured. A case where the number of detected defects was less than 50 was evaluated as A (good), a case where the number was 50 or more and less than 200 was evaluated as B (somewhat good), and a case where the number was 200 or more was evaluated as C (defective). The evaluation results are shown in Table 2.

[Hydrodynamic radius (Rh)]
The hydrodynamic radius of the polymer in the composition for forming a self-assembled film prepared above was filtered through a PTFE pore size 0.2 μm syringe filter, and then the detection sensitivity was 60 ° by dynamic light scattering measurement (DLS). Measurement was performed 6 times under the measurement conditions of a temperature of 23 ° C. for 180 seconds, and the average value was obtained. The value (nm) of the hydrodynamic radius (Rh) and the area ratio (%) of 10 nm or more are shown in Table 2 below. The aromatic hydrocarbon solvent dissolves the block copolymer but may swell. That is, it is conceivable that the filterability deteriorates due to clogging or the like during circulation filtration for removing foreign substances in the preparation of the self-assembled film-forming composition. For example, when circulating filtration is performed through an HDPE 10 nm filter (high density polyethylene, PALL), it is considered that filtration failure may occur when the Rh value is 10 nm or more. Hydrodynamic radius is A (good) when the area ratio of 10 nm or more is 0.5% or less, B (slightly good) when it exceeds 0.5% and 98% or less, and exceeds 98% Was evaluated as C (poor).

 

As can be seen from the results in Table 2, according to the method for forming a self-assembled film of the example, a self-assembled film with few defects can be formed, and as a result, a pattern with a good shape can be obtained. .

According to the method for forming a self-assembled film and the composition for forming a self-assembled film of the present invention, a self-assembled film with few defects can be formed. According to the pattern forming method of the present invention, a pattern having a good shape can be formed using the above self-assembled film with few defects. Therefore, they can be suitably used in pattern formation processes in the manufacture of various electronic devices such as semiconductor devices and liquid crystal devices that 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 in which polymer is unevenly distributed 105 Lower layer film 106 Pre-pattern

Claims (7)

1. A step of forming a coating film on a substrate with a composition for forming a self-assembled film containing one or more kinds of first polymers capable of forming a phase separation structure by self-assembly and a solvent;
   A method for forming a self-assembled film, wherein the solvent contains an aromatic ring-containing compound.
2. The method for forming a self-assembled film according to claim 1, further comprising a step of heating the coating film.
3. The method for forming a self-assembled film according to claim 1 or 2, wherein the content of the aromatic ring-containing compound in the solvent is 80% by mass or less.
4. The method for forming a self-assembled film according to claim 1, 2 or 3, wherein the content of the aromatic ring-containing compound in the solvent is 50% by mass or more.
5. The composition for forming a self-assembled film further contains a second polymer having a surface free energy smaller than that of the first polymer,
   The method for forming a self-assembled film according to any one of claims 1 to 4, wherein the second polymer is unevenly distributed above the self-assembled film.
6. A method for forming a self-assembled film according to any one of claims 1 to 5,
   Removing the partial phase of the self-assembled film.
7. Containing one or more kinds of first polymers capable of forming a phase separation structure by self-assembly, and a solvent,
   The solvent contains an aromatic ring-containing compound,
   A composition for forming a self-assembled film, wherein the content of the aromatic ring-containing compound in the solvent is 50% by mass or more.

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