JP2016161886A - Composition for forming underlay film, method for forming underlay film and self assemble lithography process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for forming an underlay film enhancing heat resistance while increasing clarity of a phase separation structure by a self assembly and rectangle property of a pattern, a method for forming an underlay film and a self assemble lithography process.SOLUTION: There is provided a composition for forming an underlay film used for forming an underlay film 102 of a self assemble film 105 in a self assemble lithography process and containing a polymer having a structural unit derived from an ethylenic unsaturated compound containing a naphthalene ring and a solvent. The polymer is preferably an acenaphthylene polymer. Absorbance index of the underlay film is preferably 0.15 or more and 0.40% or less. 5% reduction temperature in a thermal mass measurement of the underlay film is preferably 270°C or higher. Weight average molecular weight of the polymer is preferably 1,000 or more and 20,000 or less. It is preferable to contain further a crosslinking agent and the polymer has a crosslinkable group.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a composition for forming an underlayer film, a method for forming an underlayer film, and a self-organized lithography process.

  With the miniaturization of various electronic devices such as semiconductor devices and liquid crystal devices, there is a demand for pattern miniaturization in lithography processes. At present, it is possible to form a fine pattern with a line width of about 90 nm using, for example, an ArF excimer laser, but a finer pattern formation has been required.

  In response to such a demand, a self-organized lithography process using a so-called self-organized phase separation structure that spontaneously forms an ordered pattern has been proposed. As such a self-organized lithography process, a method of forming an ultrafine pattern by self-organization using a block copolymer obtained by copolymerizing monomers having different properties is known (Japanese Patent Application Laid-Open No. 2008-149447). No. publication, Japanese translations of PCT publication No. 2002-519728 publication, and Unexamined-Japanese-Patent No. 2003-218383). According to this method, by annealing the film containing the block copolymer, polymer structures having the same properties tend to gather together, so that a pattern can be formed in a self-aligning manner. 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 official gazette).

  In such a self-assembled lithography process, it is known that the above-described phase separation by self-assembly may occur effectively by forming a film containing a component such as a polymer to be self-assembled on the lower layer film. ing. Various studies have been conducted on this lower layer film, and various phase separation structures can be formed by appropriately controlling the surface free energy of the lower layer film when the block copolymer is self-assembled. (See JP2008-36491 and JP2012-174984). However, these conventional lower layer films have difficulty in heat resistance, and due to the low heat resistance, the lower layer film components sublimate due to heating during formation of the lower layer film or annealing, and the sublimated components are transferred to the substrate. It may reattach and worsen the manufacturing yield of semiconductor devices. In addition, the clarity of the obtained phase separation structure and the rectangularity of the pattern remain insufficient. Under such circumstances, a phase separation structure obtained by self-organization and a pattern formed thereby are desired, and an underlayer film having high heat resistance is desired.

JP 2008-149447 A Japanese translation of PCT publication No. 2002-519728 JP 2003-218383 A US Patent Application Publication No. 2009/0214823 JP 2010-58403 A JP 2008-36491 A JP 2012-174984 A

  The present invention has been made based on the above circumstances, and is a composition for forming an underlayer film that significantly improves heat resistance while improving the clarity of the phase separation structure by self-organization and the rectangularity of the pattern. Another object is to provide a method for forming an underlayer film and a self-organized lithography process.

  The present invention made in order to solve the above-mentioned problems is a composition for forming an underlayer film used for forming an underlayer film of a self-assembled film in a self-assembled lithography process, and an ethylenically unsaturated compound containing a naphthalene ring It is the composition for lower layer film formation containing the polymer and solvent which have the structural unit derived from.

  Another invention made in order to solve the above-mentioned problems comprises a step of forming a coating film on one surface side of a substrate, and a step of forming a lower layer film by heating the coating film and the substrate. Is a method for forming an underlayer film, which is formed by the composition for forming an underlayer film.

  Still another invention made in order to solve the above problems is a process of forming a lower layer film on one surface side of a substrate, a self-organization having a phase separation structure on a surface side of the lower layer film opposite to the substrate A self-assembled lithography process comprising a step of laminating a layered film and a step of removing a part of the phase of the self-assembled film, wherein the lower layer film is formed by a method of forming the lower layer film.

  According to the composition for forming an underlayer film of the present invention, the heat resistance can be remarkably improved while enhancing the clarity of the phase separation structure by self-organization and the rectangularity of the pattern. Therefore, the composition for forming an underlayer film can be suitably used in a lithography process in the production of various electronic devices such as semiconductor devices and liquid crystal devices that are required to be further miniaturized.

In the self-organized lithography process of this invention, it is typical sectional drawing which shows an example after forming a lower layer film. In the self-organized lithography process of this invention, it is typical sectional drawing which shows an example after forming a pre pattern on a lower layer film. In the self-assembled lithography process of the present invention, it is a schematic cross-sectional view showing an example of a state after applying a self-assembled composition to a region on an underlayer film partitioned by a pre-pattern. FIG. 5 is a schematic cross-sectional view showing an example of a state after a self-assembled film is formed in a region on a lower layer film sandwiched between pre-patterns in the self-assembled lithography process of the present invention. FIG. 5 is a schematic cross-sectional view showing an example of a state after removing a part of phases and a pre-pattern of a self-assembled film in the self-assembled lithography process of the present invention.

<Composition for lower layer film formation>
The composition for forming an underlayer film is a composition for forming an underlayer film used for forming an underlayer film of a self-assembled film in a self-assembled lithography process, and has a structure derived from an ethylenically unsaturated compound containing a naphthalene ring A polymer having a unit (hereinafter also referred to as [A] polymer) and a solvent (hereinafter also referred to as [D] solvent) are contained. The underlayer film forming composition preferably contains a crosslinking agent (hereinafter also referred to as [B] crosslinking agent) and an acid generator (hereinafter also referred to as [C] acid generator) as suitable components. Further, other components may be contained. Hereinafter, each component will be described.

<[A] polymer>
[A] The polymer has a structural unit derived from an ethylenically unsaturated compound containing a naphthalene ring. As this structural unit, for example, a structural unit derived from acenaphthylene or a derivative thereof (hereinafter also referred to as “structural unit (I)”), or a naphthyl ester of (meth) acrylic acid such as 1-naphthyl (meth) acrylate. A structural unit derived from allylnaphthalene, a structural unit derived from vinylnaphthalene, and the like. Among these, derived from the naphthyl ester of the structural unit (I) and (meth) acrylic acid from the viewpoint of further improving the heat resistance while further improving the clarity of the phase separation structure by self-organization and the rectangularity of the pattern. And the structural unit (I) is more preferable. In addition, the [A] polymer may have structural units other than the structural unit derived from the ethylenically unsaturated compound containing a naphthalene ring, and may have 2 or more types of each structural unit.

  According to the composition for forming an underlayer film, by containing the [A] polymer, the heat resistance can be remarkably improved while enhancing the clarity of the phase separation structure and the rectangularity of the pattern by self-organization. it can.

  The reason why the composition for forming a lower layer film exhibits the above-described effect by having the above-described configuration is not necessarily clear, but can be inferred as follows, for example. That is, the [A] polymer contained in the composition for forming a lower layer film can have increased stability to heat by having a naphthalene ring, and as a result, the formed lower layer film exhibits high heat resistance. It is considered possible. In addition, when the phase separation structure (microdomain structure) of the self-assembled film is formed, in addition to the interaction between the components constituting the self-assembled film, it is formed from the specific composition for forming a lower layer film. It is considered that the interaction between the lower layer film and the above components works effectively. As a result, the phase separation structure can be controlled, and the phase separation structure by self-organization can be formed easily and satisfactorily. Therefore, it is considered that the clarity of the phase separation structure and the rectangularity of the pattern can be improved.

  Hereinafter, as an example of the [A] polymer, a polymer having the structural unit (I) (hereinafter also referred to as “acenaphthylene polymer”) will be described. In addition to the structural unit (I), the acenaphthylene polymer includes a structural unit (II) having a vinyl naphthalene structure, a structural unit (III) represented by the formula (3) described later, and a structural unit containing a polar group ( IV) and may have other structural units other than the structural units (I) to (IV). In addition, the acenaphthylene polymer may have two or more kinds of each structural unit. Hereinafter, each structural unit will be described in detail.

[Structural unit (I)]
As the structural unit (I), a structural unit represented by the following formula (1) is preferable.

In said formula (1), R ^{< 1 >} , R ^{< 2} > and R ^<x> are respectively independently a hydrogen atom, a halogen atom, or a C1-C20 monovalent organic group. m is an integer of 0-6. When m is 2 or more, the plurality of R ^x may be the same or different.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ¹ and R ² include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a carbon-carbon bond or a bond of the hydrocarbon group. Examples include a hetero atom-containing group containing a group having a hetero atom at the terminal on the side, a group in which part or all of the hydrogen atoms of the hydrocarbon group and the group containing the hetero atom-containing group are substituted with a substituent.

  Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and the number of carbon atoms. Examples thereof include 6-20 monovalent aromatic hydrocarbon groups.

  Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom.

  Examples of the group having a heteroatom include —O—, —CO—, —NH—, —S—, and a combination thereof.

  Examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom, hydroxy group, carboxy group, cyano group, nitro group, alkoxy group, alkoxycarbonyl group and acyl group.

R ¹ and R ² are preferably a hydrogen atom.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ^x include the same groups as those exemplified for R ¹ and R ² . Among these, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 6 carbon atoms, a substituted or unsubstituted alkoxycarbonyl group having 2 to 10 carbon atoms, and substituted or unsubstituted An unsubstituted aryl group having 6 to 14 carbon atoms is preferred.
Examples of the substituent include a halogen atom, a hydroxy group, an alkyl group having 1 to 9 carbon atoms, and an aryl group having 6 to 22 carbon atoms. Among these, a hydroxy group is preferable.

R ^x is preferably a group in which a part of hydrogen atoms of the alkyl group is substituted with a hydroxy group, and more preferably a hydroxymethyl group.

  As m, 0 and 1 are preferable.

  As a minimum of the content rate of structural unit (I), 20 mol% is preferable with respect to all the structural units which comprise an acenaphthylene polymer, 35 mol% is more preferable, and 50 mol% is further more preferable. As an upper limit of the content rate of structural unit (I), 100 mol% is preferable, 98 mol% is more preferable, 96 mol% is further more preferable. By making the content rate of structural unit (I) into the said range, the lower layer film | membrane which improves heat resistance can be formed, improving the clarity of the phase-separation structure by self-organization, and the rectangularity of a pattern more. .

[Structural unit (II)]
The structural unit (II) is a structural unit represented by the following formula (2). When the acenaphthylene polymer has the structural unit (II), it is possible to form a lower layer film that further improves the heat resistance while further improving the clarity of the phase separation structure by self-organization and the rectangularity of the pattern.

In the formula ^{(2), R 3, R} 4, R 4 ' and ^{R y} are each independently a hydrogen atom, a monovalent organic group halogen atoms or 1 to 20 carbon atoms. n is an integer of 0-7. When n is 2 or more, the plurality of R ^y may be the same or different.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the R ³ , R ⁴ and R ⁴ ′ include a monovalent organic group having 1 to 20 carbon atoms exemplified as the R ¹ and R ² above. The same group etc. are mentioned.

R ³ , R ⁴ and R ⁴ ′ are preferably hydrogen atoms.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ^y include the same groups as those exemplified for R ¹ and R ² .

  n is preferably 0.

  As a minimum of the content rate of structural unit (II), 0 mol% is preferable with respect to all the structural units which comprise an acenaphthylene polymer, 2 mol% is more preferable, and 4 mol% is more preferable. As an upper limit of the content rate of structural unit (II), 30 mol% is preferable, 20 mol% is more preferable, and 10 mol% is further more preferable. By setting the content ratio of the structural unit (II) within the above range, it is possible to form an underlayer film that further improves the heat resistance while further improving the clarity of the phase separation structure by self-organization and the rectangularity of the pattern. .

[Structural unit (III)]
The structural unit (III) is a structural unit represented by the following formula (3). When the acenaphthylene polymer has the structural unit (III), it is possible to form an underlayer film that further improves the heat resistance while further improving the clarity of the phase separation structure and the rectangularity of the pattern by self-assembly.

In the formula ^{(3), R 5, R} 6 and ^{R z} are each independently a hydrogen atom, a monovalent organic group halogen atoms or 1 to 20 carbon atoms. k is an integer of 0-4. When k is 2 or more, the plurality of R ^z may be the same or different.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ⁵ and R ⁶ include the same groups as the monovalent organic group having 1 to 20 carbon atoms exemplified as R ¹ and R ² above. Is mentioned.

R ⁵ and R ⁶ are preferably a hydrogen atom.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ^z include the same groups as those exemplified for R ¹ and R ² .

  k is preferably 0.

  As a minimum of the content rate of structural unit (III), 0 mol% is preferable with respect to all the structural units which comprise an acenaphthylene polymer, 2 mol% is more preferable, and 4 mol% is more preferable. As an upper limit of the content rate of structural unit (III), 30 mol% is preferable, 20 mol% is more preferable, and 10 mol% is further more preferable. By setting the content ratio of the structural unit (III) within the above range, it is possible to form an underlayer film that further improves the heat resistance while further improving the clarity of the phase separation structure by self-organization and the rectangularity of the pattern. .

[Structural unit (IV)]
The structural unit (IV) is a structural unit containing a polar group.

  Examples of the polar group include an oxygen atom, a hydroxy group, an oxo group (═O), a carboxy group, a nitro group, a cyano group, and a sulfonamide group. Among these, an oxygen atom is preferable.

  As the structural unit (IV), a structural unit having an ether group is preferable, a structural unit derived from alkoxyalkyl (meth) acrylate is more preferable, and a structural unit derived from methoxyethyl (meth) acrylate is more preferable.

  As a minimum of the content rate of structural unit (IV), 0 mol% is preferable with respect to all the structural units which comprise an acenaphthylene polymer, 2 mol% is more preferable, and 4 mol% is more preferable. As an upper limit of the content rate of structural unit (IV), 30 mol% is preferable, 20 mol% is more preferable, and 10 mol% is further more preferable. By making the content rate of structural unit (IV) into the said range, the lower layer film | membrane which improves heat resistance more can be formed, improving the clarity of the phase-separation structure by self-organization, and the rectangularity of a pattern more. .

[Other structural units]
The acenaphthylene-based polymer may have other structural units other than the structural units (I) to (IV). As a content rate of said other structural unit, 20 mol% or less is preferable with respect to all the structural units which comprise an acenaphthylene polymer, and 10 mol% or less is more preferable.

  [A] Even when the polymer is a polymer other than the acenaphthylene-based polymer, it may have structural units such as the structural units (II) to (IV) described above, and may have the other conceptual units. May be. Moreover, when the said composition for lower layer film formation contains the [B] crosslinking agent mentioned later, it is preferable that a [A] polymer has a crosslinkable group in each structural unit mentioned above.

Examples of the crosslinkable group include groups having reactive unsaturated double bonds such as a vinyl group, a vinyl ether group, and a (meth) acryloyl group;
A ring-opening polymerizable reactive group such as a cyclic ether group such as an oxiranyl group, an oxetanyl group and a tetrahydrofurfuryl group;
Groups having active hydrogen such as hydroxy group, methylol group, carboxy group, amino group, phenolic hydroxyl group, mercapto group, hydrosilyl group, silanol group;
Groups containing groups that can be substituted by nucleophiles such as active halogen atom-containing groups, sulfonate groups, carbamoyl groups;
An acid anhydride group etc. are mentioned.
Among these, a hydroxy group, a group having a reactive unsaturated double bond, and a cyclic ether group are preferable, and a hydroxy group, a vinyl group, a vinyl ether group, an oxiranyl group, an oxetanyl group, and a tetrahydrofurfuryl group are more preferable. And a vinyl group is more preferable.

  The underlayer film forming composition may contain one or more [A] polymers. Content of the [A] polymer in the said composition for lower layer film formation is 0.1 to 10 mass%, for example.

<[A] Polymer Synthesis Method>
[A] The polymer can be produced, for example, by polymerizing a monomer giving each predetermined structural unit in a suitable solvent using a radical polymerization initiator.

  As reaction temperature in the said superposition | polymerization, it is 40 to 150 degreeC normally, and 50 to 150 degreeC is preferable. The reaction time is usually 1 hour to 48 hours, and preferably 1 hour to 24 hours.

  Examples of the radical initiator include dimethyl 2,2'-azobis (2-methylpropionate, 2,2'-azobis (2-methylpropionitrile) and the like.

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;
Halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, chlorobenzene;
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;
Ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes;
Examples include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol. Two or more of these solvents can be used in combination.

  The polymer obtained by the polymerization reaction can be recovered by a reprecipitation method. As the reprecipitation solvent, an alcohol solvent or the like can be used.

  [A] The lower limit of the weight average molecular weight (Mw) in terms of polystyrene by gel permeation chromatography (GPC) of the polymer is preferably 1,000, more preferably 1,200, and still more preferably 1,400. On the other hand, the upper limit of Mw is preferably 20,000, more preferably 15,000, and still more preferably 10,000. [A] When Mw of the polymer is less than the lower limit, the intermixing resistance of the lower layer film may be lowered. On the other hand, when Mw exceeds the upper limit, the in-plane uniformity of the lower layer film may be lowered.

<[B] Crosslinking agent>
It is preferable that the said composition for lower layer film formation further contains a [B] crosslinking agent. When the composition for forming a lower layer film further contains a [B] cross-linking agent, a cross-linking reaction between the [B] cross-linking agent and the [A] polymer occurs, and the heat resistance of the formed lower layer film is further improved. be able to.

  [B] Examples of the crosslinking agent include polyfunctional (meth) acrylate compounds, epoxy compounds, hydroxymethyl group-substituted phenol compounds, and compounds having an alkoxyalkylated amino group.

  Examples of the polyfunctional (meth) acrylate compound include trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta ( (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerin tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butanediol Di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) a Relate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, bis (2-hydroxyethyl) isocyanurate di (meth) acrylate.

  Examples of the epoxy compound include novolac type epoxy resins, bisphenol type epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins.

  Examples of the hydroxymethyl group-substituted phenol compound include 2-hydroxymethyl-4,6-dimethylphenol, 1,3,5-trihydroxymethylbenzene, 3,5-dihydroxymethyl-4-methoxytoluene [2,6-bis). (Hydroxymethyl) -p-cresol] and the like.

  Examples of the compound having an alkoxyalkylated amino group include methoxymethylated melamine and methoxymethylated glycoluril, and hexamethoxymethylated melamine and tetramethoxymethylated glycoluril are preferable.

  These [B] crosslinking agents may be used in combination of two or more.

  When the composition for forming an underlayer film contains a [B] cross-linking agent, the lower limit of the content of the [B] cross-linking agent is preferably 0.1 parts by mass with respect to 100 parts by mass of the [A] polymer. 1 part by mass is more preferable. [B] The upper limit of the content of the crosslinking agent is preferably 50 parts by mass, and more preferably 30 parts by mass. [B] If the content of the crosslinking agent is less than 0.1 parts by mass, the heat resistance of the resulting lower layer film may be insufficient. On the other hand, when the content of the [B] crosslinking agent exceeds 50 parts by mass, a crosslinking reaction may occur between the crosslinking agent in the lower layer film and the self-assembled film.

[[C] acid generator]
The underlayer film forming composition may contain a [C] acid generator. When the composition for forming a lower layer film contains a [C] acid generator, for example, when patterning the upper resist film, the acid generated by exposure in the resist film may diffuse into the lower layer film. An acid is supplied from the lower film side so as to eliminate the acid shortage of the film, and as a result, a good resist pattern shape can be obtained.

  [C] Examples of the acid generator include a photoacid generator and a thermal acid generator.

Examples of the photoacid generator include triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium 2- (adamantan-1-ylcarbonyloxy) -1,1,3,3,3-pentafluoropropane-1-sulfonate, Phenylsulfonium norbornane sultone-2-yloxycarbonyldifluoromethanesulfonate, triphenylsulfonium piperidin-1-ylsulfonyl-1,1,2,2,3,3-hexafluoropropane-1-sulfonate, triphenylsulfonium adamantane-1 -Yloxycarbonyldifluoromethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium camphorsulfonate, 4-methanesulfonylphenyldiphenylsulfonium nonafluo Sulfonium salts such as rho-n-butanesulfonate;
1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (6-n-butoxynaphthalen-1-yl) tetrahydrothiophenium 2-bicyclo [2.2.1] Tetrahydrothiophenium salts such as hept-2-yl-1,1,2,2-tetrafluoroethane-1-sulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium camphorsulfonate;
N- (trifluoromethanesulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide, N- (camphorsulfonyloxy) bicyclo [2.2.1] hept-5-ene And N-sulfonyloxyimide compounds such as -2,3-dicarboximide.

Examples of the thermal acid generator include diphenyliodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate, 4-methoxy Examples include iodonium salts such as phenylphenyliodonium camphorsulfonate.

  [C] The acid generator is preferably a thermal acid generator, and more preferably bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate.

  When the composition for forming a lower layer film contains a [C] acid generator, the lower limit of the content of the [C] acid generator is 0.1 part by mass with respect to 100 parts by mass of the [A] polymer. Is preferable, and 0.5 mass part is more preferable. [C] The upper limit of the content of the acid generator is preferably 30 parts by mass, and more preferably 20 parts by mass. [C] By making content of an acid generator into the said range, the above-mentioned pattern shape can be made more favorable. [C] As an acid generator, 1 type (s) or 2 or more types can be used.

[[D] solvent]
The composition for forming the lower layer film contains a [D] solvent. [D] The solvent is not particularly limited as long as it is a solvent capable of dissolving or dispersing at least the [A] polymer and, if necessary, the [B] cross-linking agent, [C] acid generator and the like.

  [D] Examples of the solvent include alcohol solvents, ether solvents, ketone organic solvents, amide solvents, ester organic solvents, hydrocarbon solvents, and the like. In addition, these [D] solvents can use 2 or more types together.

Examples of the alcohol solvent include aliphatic monoalcohol solvents having 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;
A C2-C18 polyhydric alcohol solvent such as 1,2-propylene glycol;
Examples thereof include C3-C19 polyhydric alcohol partial ether solvents such as propylene glycol monomethyl ether.

Examples of ether solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, and diheptyl ether;
Cyclic ether solvents such as tetrahydrofuran and tetrahydropyran;
Aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether) are exemplified.

Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-iso-butyl ketone, 2-heptanone (methyl-n-pentyl ketone), ethyl-n-butyl ketone. Chain ketone solvents such as methyl-n-hexyl ketone, di-iso-butyl ketone, and trimethylnonanone;
Cyclic ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, methylcyclohexanone;
2,4-pentanedione, acetonylacetone, acetophenone and the like can be mentioned.

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 ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate;
Polyhydric alcohol carboxylate solvents such as propylene glycol acetate;
Polyhydric alcohol partial ether carboxylate solvents such as propylene glycol monomethyl ether acetate;
Polycarboxylic acid diester solvents such as diethyl oxalate;
Examples thereof include carbonate solvents such as dimethyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate.

Examples of the hydrocarbon solvent include aliphatic hydrocarbon solvents 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.

  Of these, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, cyclohexanone, γ-butyrolactone, and propylene carbonate are preferable.

<Other optional components>
The composition for forming the lower layer film may contain other optional components as necessary within the range not impairing the effects of the present invention. Examples of other optional components include surfactants and storage stabilizers.

<Method for Preparing Composition for Forming Lower Layer Film>
The composition for forming the lower layer film includes, for example, a [D] solvent and a [A] polymer, and if necessary, a [B] cross-linking agent, a [C] acid generator, and other optional components in a predetermined ratio. Prepared by mixing. The underlayer film forming composition is preferably prepared and used in a state of being dissolved or dispersed in an appropriate solvent.

<Self-organized lithography process>
Self-organized (Directed Self Assembly) refers to a phenomenon of spontaneously constructing an organization or structure, not only due to control from an external factor. In the present invention, a film having a phase separation structure by self-assembly (self-assembled film) is formed on a lower layer film that is a specific silicon atom-containing film, for example, by applying a self-assembled composition. By removing a part of the phase in the self-assembled film, a pattern (self-assembled pattern) can be formed.

  In the self-assembled lithography process of the present invention, a step of forming a lower layer film on one surface side of the substrate (hereinafter, also referred to as “lower layer film forming step”), on the surface side of the lower layer opposite to the substrate, A step of laminating a self-assembled film having a phase separation structure (hereinafter also referred to as “self-assembled film laminating step”) and a step of removing a part of the phase of the self-assembled film (hereinafter referred to as “removing step”) Say). Hereinafter, an example of each process will be described.

[Lower layer formation process]
This step is a step of forming the lower layer film using the lower layer film forming composition. This underlayer film forming composition is described above as the underlayer film forming composition of the present invention. This lower layer film is formed on one surface side of the substrate, and by this step, a substrate with the lower layer film in which the lower layer film 102 is formed on the substrate 101 is obtained as shown in FIG. The self-assembled film is laminated on the lower layer film 102. In the formation of the phase separation structure (microdomain structure) of the self-assembled film, in addition to the interaction between components constituting the self-assembled film, the interaction between this component and the lower layer film 102 is effective. The phase separation structure can be controlled by this, and a phase separation structure by self-organization can be formed easily and satisfactorily. As a result, an excellent pattern can be formed. When the self-assembled film is a thin film, the transfer process can be improved by having the lower layer film 102.

  As the substrate 101, for example, a conventionally known substrate such as a silicon wafer or a wafer coated with aluminum can be used. The lower layer film 102 is formed by curing a coating film formed by applying the lower layer film forming composition on the substrate 101 by a known method such as a spin coating method by heating and / or exposing to light. Can do. 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.

  As the formation condition of the lower layer film, the temperature at which the coating film is heated is not particularly limited, but the lower limit of the heating temperature is preferably 100 ° C, more preferably 120 ° C, further preferably 150 ° C, and 180 ° C. Is particularly preferred. On the other hand, as an upper limit of heating temperature, 400 degreeC is preferable, 300 degreeC is more preferable, 240 degreeC is further more preferable, and 220 degreeC is especially preferable. The time for heating the coating film is not particularly limited, but the lower limit of the heating time is preferably 10 seconds, more preferably 15 seconds, and further preferably 30 seconds. On the other hand, the upper limit of the heating time is preferably 30 minutes, more preferably 10 minutes, and even more preferably 5 minutes. By setting the heating temperature and time for forming the lower layer film within the above range, the lower layer film can be easily and reliably formed. The atmosphere for heating the coating film is not particularly limited, and may be an air atmosphere or an inert gas atmosphere such as nitrogen gas.

  The extinction coefficient of the lower layer film formed is preferably 0.15 or more and 0.40 or less. By setting the extinction coefficient of the lower layer film within the above range, a phase separation structure by self-organization can be formed better, and a more excellent pattern can be formed. The extinction coefficient is a value measured by irradiating light with a wavelength of 193 nm using a spectroscopic ellipsometer.

  The lower limit of the 5% weight loss temperature in the thermal mass measurement of the underlayer film formed is preferably 270 ° C and more preferably 280 ° C. By setting the 5% weight loss temperature of the formed lower layer film to the above lower limit or more, the heat resistance of the obtained lower layer film can be further improved. The “5% weight loss temperature” is a temperature at which the sample is heated from room temperature at a rate of 10 ° C./min in a nitrogen stream and the mass of the sample reaches 95% at the start of measurement.

  The average thickness of the lower layer film 102 is not particularly limited, but the lower limit is preferably 5 nm, more preferably 10 nm, still more preferably 15 nm, and particularly preferably 20 nm. On the other hand, the upper limit is preferably 20,000 nm, more preferably 1,000 nm, still more preferably 500 nm, and particularly preferably 100 nm.

[Pre-pattern forming process]
The self-assembled lithography process may include a step of forming a pre-pattern on the surface of the lower layer film opposite to the substrate after the lower layer film forming step. In this step, as shown in FIG. 2, a prepattern 103 is formed on the lower layer film 102 using a composition for forming a prepattern. In some cases, the pre-pattern 103 controls phase separation when forming a self-assembled film, and a phase-separated structure by self-assembly can be formed better. That is, among the components that form a self-assembled film, components that have a high affinity with the side surface of the prepattern form a phase along the prepattern, and components that have a low affinity have a position away from the prepattern. Form a phase. Thereby, the phase separation structure by self-organization can be formed more clearly. Further, the phase separation structure to be formed can be finely controlled by the material, length, thickness, shape and the like of the prepattern. The pre-pattern can be appropriately selected according to the pattern to be finally formed. For example, a line and space pattern, a hole pattern, a pillar pattern, or the like can be used.

  As a method for forming the pre-pattern 103, 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. As a specific method for forming the pre-pattern 103, for example, a chemically amplified resist composition such as “ARX2928JN” manufactured by JSR is used and applied onto the lower layer film 102 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. Of these, far ultraviolet rays such as ArF excimer laser light and KrF excimer laser light are preferable, and ArF excimer laser light is more preferable. Next, post-exposure baking (PEB) is performed, and development is performed using a developer such as an alkali developer, so that a desired pre-pattern 103 can be formed.

  The surface of the pre-pattern 103 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 103, the above self-assembly can be promoted.

[Self-assembled film lamination process]
This step is a step of laminating a self-assembled film having a phase separation structure on the lower layer film formed in the lower layer film forming step. This self-assembled film is laminated by, for example, applying a self-assembled composition containing a component capable of forming a phase-separated structure by self-assembly onto the formed underlayer film. And it can carry out by making the said component in this coating film self-assemble. Further, when using the pre-pattern 103, as shown in FIG. 3, the coating film 104 is formed by applying the self-assembling composition to the region on the lower layer film 102 delimited by the pre-pattern 103, A self-assembled film 105 having a phase separation structure is formed.

  In the formation of the self-assembled film 105, the above-mentioned self-assembled composition is applied onto the lower layer film 102 to form the coating film 104, and then annealing or the like is performed, so that parts having the same properties are accumulated. The so-called self-organization that spontaneously forms an ordered pattern can be promoted. As a result, a phase separation structure is formed on the lower layer film 102. This phase separation structure is preferably formed along the pre-pattern, and the interface formed by phase separation is more preferably substantially parallel to the side surface of the pre-pattern. For example, when the pre-pattern 103 is a line pattern, the phase 105b having the higher affinity with the pre-pattern 103 is formed along the pre-pattern 103, and the other phase 105a having the other affinity is the pre-pattern 103. Forming a lamellar phase separation structure in which lamella-like (plate-like) phases are alternately arranged. When the pre-pattern is a hole pattern, a phase such as a component having a higher affinity with the pre-pattern is formed along the side surface of the hole of the pre-pattern, and a phase such as the other component is formed in the central portion of the hole. It is formed. When the pre-pattern is a pillar pattern, a phase such as a component having a higher affinity with the pre-pattern is formed along the side of the pillar of the pre-pattern, and the other part is separated from each pillar. A phase such as a component is formed. A desired phase separation structure can be formed by appropriately adjusting the distance between the pillars of the pre-pattern, the structure of each polymer and the like in the self-assembled composition, the blending ratio, and the like. The phase separation structure formed in this step is composed of a plurality of phases, and the interface formed from these phases is usually substantially vertical, but the interface itself does not require strict clarity. Absent. Thus, in addition to the lower layer film, the phase separation structure to be obtained can be precisely controlled by the structure, compounding ratio, and pre-pattern of each polymer component to obtain a desired fine pattern.

  The component capable of forming a phase separation structure by self-assembly is not particularly limited as long as it has such properties. For example, a block copolymer, a mixture of two or more kinds of polymers incompatible with each other, etc. Is mentioned. Among these, from the viewpoint of forming a clearer phase separation structure, a block copolymer is preferable, a block copolymer composed of a styrene unit-methacrylic ester unit is more preferable, and a styrene unit-methyl methacrylate unit. More preferred is a diblock copolymer.

  A method for forming the coating film 104 by applying the self-assembling composition on a substrate is not particularly limited, and examples thereof include a method of applying the self-assembling composition by a spin coating method or the like. Thereby, the self-assembling composition is applied between the prepatterns 103 on the lower layer film 102 and the like, and the coating film 104 is formed.

  Examples of the annealing method include a method of heating at a temperature of 80 ° C. or higher and 400 ° C. or lower, preferably 80 ° C. or higher and 300 ° C. or lower, using an oven, a hot plate, or the like. The annealing time is usually 10 seconds to 120 minutes, preferably 30 seconds to 60 minutes. The average thickness of the self-assembled film 105 thus obtained is preferably 0.1 nm or more and 500 nm or less, and more preferably 0.5 nm or more and 100 nm or less.

[Removal process]
This process is a process of removing a part of the phase separation structure of the self-assembled film 105 as shown in FIGS. A part of the phase 105a and / or the pre-pattern 103 can be removed by an etching process using a difference in etching rate between phases separated by self-organization. FIG. 5 shows a state after removing a part of the phase 105a and the pre-pattern 103 in the phase separation structure.

Examples of a method for removing a part of the phase separation structure 105a or the pre-pattern 103 in the phase separation structure of the self-assembled film 105 include reactive ion etching (RIE) such as chemical dry etching and chemical wet etching; Known methods such as physical etching such as ion beam etching may be used. Of these, reactive ion etching (RIE) is preferred, chemical dry etching using CF ₄ , O ₂ gas, etc., organic solvents such as methyl isobutyl ketone (MIBK), 2-propanol (IPA), and liquids such as hydrofluoric acid. Chemical wet etching (wet development) using the etching solution is more preferable.

[Substrate pattern formation process]
The self-organized lithography process preferably further includes a substrate pattern forming step after the removing step. This step is a step of patterning by etching the lower layer film and the substrate using a pattern formed of a part of the phase 105b of the remaining phase separation film as a mask. After the patterning on the substrate is completed, the phase used as a mask is removed from the substrate by dissolution treatment or the like, and finally a patterned substrate (pattern) can be obtained. Examples of the obtained pattern include a line and space pattern and a hole pattern. As the etching method, the same method as 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 a silicon material, a mixed gas of chlorofluorocarbon gas and SF ₄ or the like 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. The pattern obtained by the self-organized lithography process is suitably used for semiconductor elements and the like, and the semiconductor elements are widely used for LEDs, solar cells and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. Unless otherwise specified, each compound described in the following examples was commercially available as a reagent. The measuring method of various physical property values is shown below.

[Weight average molecular weight (Mw) and number average molecular weight (Mn)]
Using GPC columns (two Tosoh “G2000HXL”, one “G3000HXL” and one “G4000HXL”), flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, column temperature: 40 ° C. Measured by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard.

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

[Absorption coefficient (k value)]
The composition was spin-coated on an 8-inch silicon wafer, baked on a hot plate at 345 ° C. for 120 seconds to form a film having an average thickness of 0.1 μm, and a spectroscopic ellipsometer “MOSS-ESVG DEEP UV” manufactured by SOPRA Was used to measure the extinction coefficient (k value) at 193 nm.

[5% weight loss temperature]
Using a thermal mass measurement method (TG), the temperature of the sample was raised from room temperature at a rate of 10 ° C./min under a nitrogen stream, and the temperature at which the sample mass reached 95% at the start of measurement was defined as a 5% weight loss temperature. Recorded. It represents that it is excellent in heat resistance, so that this temperature is high.

  The structure of the monomer used in each of the following synthesis examples is shown below.

[Synthesis Example 1] (Synthesis of Polymer A-1)
A separable flask equipped with a thermometer was prepared. The inside of the flask was replaced with nitrogen, and 5 parts by mass of acenaphthylene (M-1), 6 parts by mass of 5-hydroxymethylacenaphthylene (M-2), 50 parts by mass of n-butyl acetate and 4 parts by mass of azobisisobutyronitrile. I put a part. Polymerization was carried out at 80 ° C. for 7 hours with stirring. The reaction solution was diluted by adding 100 parts by mass of n-butyl acetate. After washing with a large amount of water / methanol mixed solvent (mass ratio: 1/2), the solvent was distilled off to obtain a polymer (A-1) having an Mw of 1,500.

[Synthesis Examples 2 to 10] (Synthesis of Polymers A-2 to A-10)
Polymers A-2 to A-10 were obtained in the same manner as in Example 1 except that the types and content ratios of the monomers used were changed as shown in Table 1.

[Synthesis Example 11] (Production of block copolymer (P-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, 0.27 g of a 1N cyclohexane solution of sec-butyllithium (sec-BuLi) was injected, and 10.7 g (0.103 mol) of styrene subjected to a distillation and dehydration treatment was added dropwise over 30 minutes. At this time, care was taken so that the temperature of the reaction solution did not exceed -60 ° C. After ripening for 30 minutes after the completion of dropping, 10.3 g (0.103 mol) of methyl methacrylate subjected to further distillation and dehydration treatment was added dropwise over 30 minutes and reacted for 120 minutes. Thereafter, 1 mL of methanol was injected as a terminal treating agent to react. The temperature of the reaction solution was raised to room temperature, and the resulting reaction solution was concentrated and replaced with propylene glycol methyl ether acetate (PGMEA). 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 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. This operation was repeated three times to remove oxalic acid, and then the solution was concentrated and dropped into 500 g of methanol to precipitate a polymer. The polymer filtered 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 block copolymer (P-1) had Mw of 41,000 and Mw / Mn of 1.13. As a result of ¹³ C-NMR analysis, the content ratio of styrene units and the content ratio of methyl methacrylate units in the block copolymer (P-1) were 50.1 mol% and 49.9 mol%, respectively. The block copolymer (P-1) was a diblock copolymer.

<Preparation of composition for forming lower layer film>
[Examples 1 to 12 and Comparative Examples 1 to 4]
Table 2 shows compositions for lower layer film formation (E-1) to (E-12) and (CE-1) to (CE-4) using the polymers (A-1) to (A-10). Adjusted as described. The [B] cross-linking agent, [C] acid generator and [D] solvent described in Table 2 are as follows.

[[B] Crosslinking agent]
B-1: 1,3,4,6-tetrakis (methoxymethyl) glycoluril B-2: 2,4,6-tris [bis (methoxymethyl) amino] -1,3,5-triazine The structure is shown below.

[[C] acid generator]
C-1: Bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate The structure of the acid generator is shown below.

[[D] solvent]
D-1: Propylene glycol monomethyl ether acetate

<Self-organized lithography process>
A silicon-containing substrate having an underlayer film was formed using the obtained composition for forming an underlayer film, and a pattern was formed using the silicon-containing substrate having the underlayer film.

[Preparation of Self-Assembled Composition]
The obtained block copolymer (P-1) was dissolved in propylene glycol monomethyl ether acetate (PGMEA) to give a 1% by mass solution. This solution was filtered through a membrane filter having a pore size of 200 nm to prepare a self-assembled composition (F-1).

[Formation of lower layer film]
A coating film was formed on the surface of a 12-inch silicon wafer using the underlayer film forming compositions (E-1) to (E-12) and (CE-1) to (CE-4). The substrate was baked at 200 ° C. for 120 seconds to obtain a substrate having a lower layer film having an average thickness of 10 nm.

[Pattern formation]
On the substrate having the lower layer film, the self-assembled composition (F-1) was applied so that the average thickness of the self-assembled film to be formed was 30 nm. Phase separation was carried out by heating at 250 ° C. for 10 minutes to form a phase separation structure having microdomains. Dry etching was performed by plasma treatment to form a substrate pattern having an uneven shape with a pitch of 30 nm.

[Clarity of phase separation structure and rectangularity of pattern shape]
The formed phase separation structure and the cross section of the substrate pattern were observed using a scanning electron microscope (“S-4800” manufactured by Hitachi, Ltd.) to evaluate the clarity of the phase separation structure and the rectangularity of the pattern shape. The phase separation structure was defined as “A” (good) when clear phase separation could be confirmed, and “B” (defective) when phase separation was incomplete or defective. The pattern shape was evaluated as “A” (good) when it was recognized as a rectangle, and “B” (not good) when it was not recognized as a rectangle, for example, undissolved residue was remarkable. The evaluation results are shown in Table 3.

[Number of defects]
The number of defects on the surface of the formed phase separation structure was measured using a defect inspection apparatus (“KLA 2351” manufactured by KLA Tencor). When the number of defects is less than 10, it can be evaluated as good and when it is 10 or more, it can be evaluated as defective.

  As can be seen from the results in Table 3, in all of the examples, the clarity of the phase separation structure and the rectangularity of the pattern shape were evaluated as A, and the 5% weight loss temperature was a high value of 280 ° C. or higher. On the other hand, Comparative Examples 1, 3, and 4 are B evaluations of the clarity of the phase separation structure and the rectangularity of the pattern shape, and Comparative Examples 1, 2, and 4 have low values of 5% weight loss temperature of less than 240 ° C. Indicated. From these results, it can be seen that according to the present invention, the heat resistance can be remarkably improved while enhancing the clarity of the phase separation structure by self-organization and the rectangularity of the pattern.

  According to the composition for forming an underlayer film of the present invention, the heat resistance can be remarkably improved while enhancing the clarity of the phase separation structure by self-organization and the rectangularity of the pattern. Therefore, the composition for forming an underlayer film can be suitably used in a lithography process in the production of various electronic devices such as semiconductor devices and liquid crystal devices that are required to be further miniaturized.

101 Substrate 102 Lower layer film 103 Pre-pattern 104 Coating film 105 Self-assembled film 105a One phase 105b constituting the self-assembled film Other phase constituting the self-assembled film

Claims (12)

A composition for forming an underlayer film used for forming an underlayer film of a self-assembled film in a self-assembled lithography process,
A composition for forming an underlayer film comprising a polymer having a structural unit derived from an ethylenically unsaturated compound containing a naphthalene ring and a solvent. The composition for forming an underlayer film according to claim 1, wherein the polymer is an acenaphthylene-based polymer having a structural unit represented by the following formula (1).

(In the formula (1), R ¹ , R ² and R ^x are each independently a hydrogen atom, a halogen atom or a monovalent organic group having 1 to 20 carbon atoms. M is an integer of 0 to 6. When m is 2 or more, a plurality of R ^x may be the same or different.) The underlayer film forming composition according to claim 2, wherein the acenaphthylene-based polymer further has a structural unit represented by the following formula (2).

(In the formula ^{(2), R 3, R} 4, R 4 ' and ^{R y} are each independently, a is .n is hydrogen atom, a monovalent organic group halogen atoms or 1 to 20 carbon atoms, 0 (It is an integer of ˜7. When n is 2 or more, a plurality of R ^y may be the same or different.)   The composition for forming an underlayer film according to claim 1, wherein the extinction coefficient of the underlayer film is from 0.15 to 0.40.   The composition for forming an underlayer film according to any one of claims 1 to 4, wherein a 5% weight loss temperature in thermal mass measurement of the underlayer film is 270 ° C or higher.   The composition for forming an underlayer according to any one of claims 1 to 5, wherein the formation condition of the underlayer is heating at 100 ° C to 400 ° C for 10 seconds to 30 minutes.   The composition for forming an underlayer film according to any one of claims 1 to 6, wherein the polymer has a weight average molecular weight of 1,000 or more and 20,000 or less.   The composition for forming an underlayer film according to any one of claims 1 to 7, further comprising a crosslinking agent, wherein the polymer has a crosslinkable group. A step of forming a coating film on one surface side of the substrate, and a step of forming a lower layer film by heating the coating film and the substrate,
The formation method of the lower layer film which forms the said coating film with the composition for lower layer film formation of any one of Claim 1-8. Forming a lower layer film on one side of the substrate;
A step of laminating a self-assembled film having a phase separation structure on the surface of the lower layer opposite to the substrate; and a step of removing a part of the phase of the self-assembled film,
A self-assembled lithography process for forming the lower layer film by the method for forming the lower layer film according to claim 9. After the lower layer film forming step,
Further comprising a step of forming a pre-pattern on the surface of the lower layer opposite to the substrate,
The self-assembled lithography process according to claim 10, wherein, in the self-assembled film stacking step, the self-assembled film is stacked in a region delimited by the pre-pattern on the surface of the lower layer opposite to the substrate. .   The self-organized lithography process according to claim 10 or 11, wherein a line and space pattern or a hole pattern is formed.

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