Resist underlayer film-forming composition

Abstract

To provide a resist underlay film forming composition for forming a resist underlayer film capable of suitably using as an antireflection film and a fattening film, in a lithography process of manufacturing a semiconductor device.SOLUTION: A resist underlayer film forming composition comprises: a resin having a repeating structural unit containing at least one -C(=O)-O- group in a main chain and a repeating structural unit containing at least one hydroxy group in the side chain, or having at least one -C(=O)-O- group in a main chain and a repeating structural unit containing at least one hydroxy group in a side chain, and these repeating structural units do not have an organic group containing an epoxy ring or an oxetane ring; an acid catalyst which has, when it is a monovalent acid in an amount of 0.1 pt.mass to 10 pts.mass based on 100 pts.mass of the resin, the acid dissociation constant pKa in water at 25°C. is -0.5 or less, or when the acidic catalyst is a multivalent acid, the acid dissociation constant pKa1 is -0.5 or less in water at 25°C. or its salt, and a solvent, and a crosslinking agent that is a monomer is not contained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resist underlayer film-forming composition for forming a resist underlayer film for lithography that can be used not only as an antireflection film during exposure but also as a planarizing film for filling recesses or steps to form a flat surface. [Background technology]

[0002] In the manufacture of semiconductor devices, microfabrication is carried out by lithography using a photoresist composition. In recent years, as the integration density of semiconductor devices has increased, the wavelength of the actinic rays used has been shortened from KrF excimer laser (248 nm) to ArF excimer laser (193 nm). However, when a KrF excimer laser or ArF excimer laser (incident light) is incident on a resist film before a resist pattern is formed, it is reflected by the substrate surface, generating standing waves in the resist film. The standing waves cause the shape of the pattern edge to become distorted, making it impossible to form a resist pattern with the desired shape. In other words, the presence of standing waves is known to cause fluctuations in the dimensions of the resist pattern and even poor resolution.

[0003] Further, for example, a composition for forming an underlayer film for lithography has been disclosed, which comprises a linear polymer having 2,4-dihydrobenzoic acid introduced into the main chain and a solvent (see Patent Document 1), and a composition for forming a resist underlayer film for lithography has been disclosed, which comprises a polymer having a benzaldehyde structure or a naphthaldehyde structure introduced into the main chain via an ester structure or an ether structure, a sulfonic acid compound, and a solvent (see Patent Document 2). It has been shown that resist underlayer films obtained from these compositions have anti-reflection properties and can produce rectangular resist patterns even when an ArF excimer laser is used as the light source.

[0004] Furthermore, with the advancement of miniaturization in semiconductor device pattern rules, dual damascene processes are being considered as a method for forming wiring on semiconductor substrates in order to solve the problem of wiring delays in semiconductor devices. Substrates formed using this process typically have recesses or steps, such as holes or trench structures. Therefore, in order to manufacture semiconductor devices with fine design rules, a resist underlayer film is required that can fill recesses or steps on a substrate and form a flat coating film without any steps. However, Patent Documents 1 and 2 do not disclose the planarization properties of the resist underlayer film (anti-reflective film).

[0005] For example, a resist underlayer film-forming composition for lithography has been disclosed that contains an alicyclic epoxy compound having a light-absorbing moiety such as a benzene ring, a thermal acid generator for promoting a crosslinking reaction, and a solvent (see Patent Document 3). It has been shown that the use of this composition makes it possible to obtain a resist underlayer film that can fill in and flatten unevenness on a substrate having holes.

[0006] In addition, a resist underlayer film containing a crosslinkable polymer and an amine salt of α-difluorosulfonic acid as a thermal acid generator has been disclosed (Patent Document 4). It has been shown that the use of this composition can produce a resist pattern with improved footing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2009 / 057458 [Patent Document 2] International Publication No. 2011 / 004721 [Patent Document 3] International Publication No. 2016 / 158509 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-039815 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above problems, an object of the present invention is to provide a resist underlayer film-forming composition that can be used in the manufacture of semiconductor devices, that is, to provide a resist underlayer film-forming composition for forming a solvent-resistant resist underlayer film without causing intermixing with a photoresist layer that is coated and formed on top of the resist underlayer film. In particular, an object of the present invention is to provide a resist underlayer film-forming composition for forming a resist underlayer film that can be suitably used not only as an antireflection film for reducing reflection of exposure light from a substrate onto a resist layer in a lithography process for manufacturing a semiconductor device, but also as a planarizing film for planarizing a semiconductor substrate having a recess or a step. [Means for solving the problem]

[0009] A first aspect of the present invention is a resist underlayer film-forming composition that contains: a resin having a repeating structural unit which contains at least one -C(=O)-O- group in the main chain and a repeating structural unit which contains at least one hydroxy group in the side chain, or a resin having a repeating structural unit which contains at least one -C(=O)-O- group in the main chain and at least one hydroxy group in the side chain, wherein these repeating structural units do not have an organic group which contains an epoxy ring or an oxetane ring; and 0.1 to 10 parts by mass, per 100 parts by mass, of an acid catalyst or a salt thereof, wherein the acid catalyst is a monovalent acid and has an acid dissociation constant pKa of -0.5 or less in water at 25°C, or the acid catalyst is a polyvalent acid and has an acid dissociation constant pKa1 of -0.5 or less in water at 25°C, and a solvent, and the resist underlayer film-forming composition does not contain a crosslinking agent which is a monomer.

[0010] The salt of the acid catalyst is, for example, a trifluoromethanesulfonate salt. The cation component of the trifluoromethanesulfonate salt is, for example, a primary to quaternary ammonium ion, an optionally substituted pyridinium ion, an optionally substituted imidazolium ion, an optionally substituted iodonium ion, an optionally substituted sulfonium ion, or an optionally substituted pyrylium ion.

[0011] The resin is, for example, a copolymer having a repeating structural unit represented by the following formula (1-1) and a repeating structural unit represented by the following formula (1-2). [ka] (In the formula, R 1 and R 2 each independently represents a divalent organic group containing a linear, branched or cyclic functional group having 2 to 20 carbon atoms, the organic group optionally having at least one sulfur atom, nitrogen atom or oxygen atom, i and j each independently represent 0 or 1, and two Qs each represent a single bond, an -O- group or a -C(=O)-O- group, provided that when both i and j are 0, at least one of the two Qs represents a -C(=O)-O- group.

[0012] In the repeating structural unit represented by the formula (1-1), R 1 represents, for example, a linear, branched or cyclic divalent hydrocarbon group having 2 to 20 carbon atoms, a linear, branched or cyclic divalent organic group having 2 to 20 carbon atoms and containing at least one sulfur atom or oxygen atom, or a divalent organic group containing at least one aromatic ring having 6 to 20 carbon atoms or a heterocyclic ring having 3 to 12 carbon atoms, and the heterocyclic ring contains at least one sulfur atom or oxygen atom. At least one. In the repeating structural unit represented by the formula (1-2), R 2 represents, for example, a linear, branched or cyclic divalent hydrocarbon group having 2 to 20 carbon atoms, or a divalent organic group containing at least one aromatic ring having 6 to 20 carbon atoms or a heterocyclic ring having 3 to 12 carbon atoms, and the heterocyclic ring has at least one sulfur atom or oxygen atom.

[0013] The resist underlayer film-forming composition of the present invention may further contain a compound represented by the following formula (2), formula (3), or formula (4). [ka] (In the formula, X represents a carbonyl group or a methylene group, l and m each independently represent an integer of 0 to 5 satisfying the relational formula 3≦l+m≦10, and R 3 and R 4 each independently represents an alkylene or alkenylene group having 1 to 4 carbon atoms or a single bond, n and p each independently represent an integer of 2 to 4, and the substituent in formula (4) can be substituted at any of the 1-8 positions of the naphthalene ring.

[0014] The resist underlayer film forming composition of the present invention may further contain a surfactant. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a resist underlayer film-forming composition for forming a resist underlayer film having solvent resistance without causing intermixing with a photoresist layer to be coated and formed on top of it. The resist underlayer film-forming composition of the present invention does not contain a low-molecular-weight compound such as a crosslinking agent, and therefore reduces the amount of sublimation during baking, and can achieve high filling of recesses without generating voids (gaps). Therefore, the present invention can provide a resist underlayer film-forming composition for forming a resist underlayer film that can planarize a substrate having recesses or steps. Furthermore, according to the present invention, it is possible to provide a resist underlayer film-forming composition for forming a resist underlayer film that can be suitably used as an antireflection film that reduces reflection of exposure light onto a resist layer from a substrate. DETAILED DESCRIPTION OF THE INVENTION

[0016] The resist underlayer film-forming composition of the present invention contains a resin, a specific amount of an acid catalyst or a salt thereof having an acid dissociation constant pKa or pKa1 of −0.5 or less in water at 25° C., and a solvent, and can be cured to form a resist underlayer film without containing a crosslinking agent that is a monomer. Here, the monomer is a monomer that does not have a repeating unit, and polymers and oligomers obtained by polymerization of multiple monomers do not fall under the category of monomer. Furthermore, by using such an acid catalyst, the resist underlayer film-forming composition of the present invention can form a resist underlayer film with excellent planarization properties on a semiconductor substrate having a recess or step. Examples of crosslinking agents that are monomers not contained in the resist underlayer film-forming composition of the present invention include melamine compounds, guanamine compounds, glycoluril compounds, urea compounds, and aromatic compounds each having two or more groups in one molecule, at least one of which is selected from methylol groups, alkoxymethyl groups, and acyloxymethyl groups; and epoxy groups, oxetanyl groups, isocyanate groups, blocked isocyanate groups, azide groups, alkenyl ether groups, acryloyl groups, and the like. Examples of the compound include epoxy compounds, oxetane compounds, isocyanate compounds, blocked isocyanate compounds, azide compounds, alkenyl ether compounds, acrylic compounds, and methacrylic compounds, each of which has two or more groups selected from at least one group selected from the group consisting of an alkyloxy group and a methacryloyloxy group in one molecule. In this specification, when a component is found to be below the detection limit as a result of quantitative analysis of the resist underlayer film-forming composition of the present invention, it is defined that the component is not contained. The components contained in the resist underlayer film-forming composition of the present invention will be described in detail below.

[0017] [Acid catalyst or its salt] The acid catalyst or salt thereof, which is an essential component of the resist underlayer film-forming composition of the present invention, is not particularly limited as long as it is an acid catalyst or a salt thereof that has an acid dissociation constant pKa of −0.5 or less in water at 25° C. when the acid catalyst is a monovalent acid, or an acid dissociation constant pKa1 of −0.5 or less in water at 25° C. when the acid catalyst is a polyvalent acid. The smaller the value of the acid dissociation constant pKa, the stronger the acid, which is preferable in the present invention. Here, the acid dissociation constant pKa is the negative common logarithm of the equilibrium constant Ka of the ionization equilibrium of the acid, i.e., pKa=-log 10 When the acid catalyst is a polyacid, multiple equilibrium constants Ka of the acid are obtained in the order of dissociation (Ka1, Ka2, Ka3, ...), but in the present invention, an acid catalyst is selected whose acid dissociation constant pKa1 is -0.5 or less, which is the negative common logarithm of the equilibrium constant Ka1 of the first-stage acid ionization equilibrium.

[0018] Examples of acid catalysts having an acid dissociation constant pKa or pKa1 of -0.5 or less include p-toluenesulfonic acid (pKa=-2.8), p-phenolsulfonic acid (pKa1=-2.59), 5-sulfosalicylic acid (pKa1=-2.81), and trifluoromethanesulfonic acid (pKa=-14.0) or salts thereof.

[0019] The cation component of these acid salts is not particularly limited, but examples thereof include cations derived from primary to tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having a hydroxyl group, nitrogen-containing compounds having a hydroxyphenyl group, alcoholic nitrogen-containing compounds, quaternary ammonium compounds, iodonium compounds, sulfonium compounds, pyran, etc., and preferred examples include primary to quaternary ammonium ions, optionally substituted pyridinium ions, optionally substituted imidazolium ions, optionally substituted iodonium ions, optionally substituted sulfonium ions, and optionally substituted pyrylium ions. Here, the substituent is not particularly limited, but examples thereof include methyl, ethyl, propyl, butyl, fluoro, phenyl, and benzyl groups.

[0020] The acid catalyst is particularly preferably a salt of trifluoromethanesulfonic acid, and examples thereof include compounds represented by the following formula: [ka]

[0021] The acid catalyst of the present invention has an extremely low volatilization amount even when the resin in the resist underlayer film-forming composition is crosslinked by baking. Therefore, the resist underlayer film-forming composition of the present invention does not contain a low-molecular-weight volatile component such as a crosslinking agent, so that the amount of sublimation produced during baking can be reduced, and a planarized resist underlayer film free of voids or other spaces can be formed.

[0022] The resist underlayer film-forming composition of the present invention contains the acid catalyst or its salt in an amount of, for example, 0.1 to 10 parts by mass relative to 100 parts by mass of the resin. If the content of the acid catalyst or its salt is less than 0.1 part by mass relative to 100 parts by mass of the resin, the effects of the present invention may not be obtained. If the content of the acid catalyst or its salt is more than 10 parts by mass relative to 100 parts by mass of the resin, the amount of sublimation product generated during baking increases, causing voids and other spaces, and the effects of the present invention may not be obtained.

[0023] [resin] The resin, which is an essential component of the resist underlayer film-forming composition of the present invention, is not particularly limited as long as it has a repeating structural unit containing at least one -C(=O)-O- group in the main chain and a repeating structural unit containing at least one hydroxy group in the side chain, or a repeating structural unit containing at least one -C(=O)-O- group in the main chain and at least one hydroxy group in the side chain, and does not contain an organic group containing an epoxy ring or an oxetane ring in these repeating structural units. Examples of organic groups containing an epoxy ring or an oxetane ring include a glycidyl group and an oxetanyl group. The resin without such an organic group is a resin without a glycidyl group, an oxetanyl group, or the like. The weight-average molecular weight of the resin is, for example, 500 to 50,000, preferably 900 to 50,000. Since the resin does not have an organic group containing a highly reactive epoxy ring or oxetane ring, the resist underlayer film-forming composition of the present invention has excellent storage stability.

[0024] The resin, which is an essential component of the resist underlayer film-forming composition of the present invention, is preferably a copolymer having a repeating structural unit represented by the above formula (1-1) and a repeating structural unit represented by the above formula (1-2).

[0025] More preferably, the group R in formula (1-1) 1 represents a linear, branched or cyclic divalent hydrocarbon group having 2 to 20 carbon atoms, a linear, branched or cyclic divalent organic group having 2 to 20 carbon atoms and having at least one sulfur atom or oxygen atom, or a divalent organic group containing at least one aromatic ring having 6 to 20 carbon atoms or a heterocyclic ring having 3 to 12 carbon atoms, wherein the heterocyclic ring has at least one sulfur atom or oxygen atom.

[0026] More preferably, the group R in formula (1-2) 2 represents a linear, branched or cyclic divalent hydrocarbon group having 2 to 20 carbon atoms, or a divalent organic group containing at least one aromatic ring having 6 to 20 carbon atoms or a heterocyclic ring having 3 to 12 carbon atoms, and the heterocyclic ring has at least one sulfur atom or oxygen atom. The aromatic ring and heterocyclic ring have an absorbency for the KrF excimer laser or ArF excimer laser used in the lithography process. Therefore, the resist underlayer film obtained from the resist underlayer film-forming composition of the present invention can be more suitably used as an antireflective film by having at least one aromatic ring or heterocyclic ring in the repeating structural unit represented by formula (1-2). Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a naphthacene ring, a triphenylene ring, a pyrene ring, and a chrysene ring, and preferred are a benzene ring and a naphthalene ring. Examples of the heterocyclic ring include a triazine ring, a cyanuric ring, a pyrimidine ring, an imidazole ring, and a carbazole ring.

[0027] The copolymer may be a commercially available product or a copolymer synthesized from a commercially available product by a known method. For example, the resin of the present invention may be a compound represented by the following formula (A): [ka] (In the formula, R 1 , i and j have the same meanings as above, and at least one compound represented by the following formula (B): [ka] (In the formula, R 2 and Q have the same meanings as above. A copolymer with at least one diepoxy compound represented by the following formula (I) can be used. That is, at least one compound represented by formula (A) and at least one diepoxy compound represented by formula (B) are dissolved in an organic solvent in an appropriate molar ratio, and polymerized, if necessary, in the presence of a catalyst, to obtain a copolymer having a repeating structural unit represented by formula (1-1) and a repeating structural unit represented by formula (1-2).

[0028] The compound represented by the formula (A) is not particularly limited, but examples thereof include compounds represented by the following formulas. [ka]

[0029] The diepoxy compound represented by the formula (B) is not particularly limited, but examples thereof include the following diepoxy compounds. [ka]

[0030] Examples of the copolymer having the repeating structural unit represented by the above formula (1-1) and the repeating structural unit represented by the following formula (1-2) include copolymers having repeating structural units represented by the following formulas (1a) to (1n). [ka] [ka]

[0031] [Compound represented by formula (2), formula (3) or formula (4)] The resist underlayer film-forming composition of the present invention may contain, as an optional component, a compound represented by the above formula (2), formula (3), or formula (4). Examples of the compound represented by the above formula (2) include compounds represented by the following formulas (2-1) to (2-20). [ka]

[0032] Examples of the compound represented by formula (3) include compounds represented by the following formulas (3-1) to (3-22). [ka]

[0033] Examples of the compound represented by formula (4) include compounds represented by the following formulae (4-1) to (4-9). [ka]

[0034] The resist underlayer film forming composition of the present invention contains the compound represented by formula (2), formula (3), or formula (4) in an amount of, for example, 0.01 to 60 parts by mass per 100 parts by mass of the resin. parts by mass, preferably 0.1 to 20 parts by mass. The resist underlayer film formed from the resist underlayer film-forming composition of the present invention can have enhanced resistance to an aqueous hydrogen peroxide solution by containing the compound represented by formula (2), formula (3), or formula (4). As a result, the resist underlayer film formed from the resist underlayer film-forming composition of the present invention can be used as a mask in an etching process and a cleaning process using an aqueous hydrogen peroxide solution.

[0035] The resist underlayer film-forming composition of the present invention may optionally contain a surfactant to improve the coating properties on the substrate. Examples of the surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkyl aryl ethers such as polyoxyethylene octylphenol ether and polyoxyethylene nonylphenol ether; polyoxyethylene-polyoxypropylene block copolymers; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, and sorbitan tristearate; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, and polyoxyethylene sorbitan monostearate; Examples of suitable surfactants include nonionic surfactants such as polyoxyethylene sorbitan fatty acid esters, such as polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, and the like; fluorine-containing surfactants such as F-TOP (registered trademark) EF301, EF303, and EF352 (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.), Megafac (registered trademark) F171, F173, R-30, R-30N, and R-40-LM (manufactured by DIC Corporation), Fluorad FC430 and FC431 (manufactured by 3M Japan Limited), Asahiguard (registered trademark) AG710, and Surflon (registered trademark) S-382, SC101, SC102, SC103, SC104, SC105, and SC106 (manufactured by AGC Corporation); and organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.). These surfactants may be added alone or in combination of two or more.

[0036] When the surfactant is used, the content of the surfactant is, for example, 0.01 to 5 parts by mass, preferably 0.1 to 3 parts by mass, per 100 parts by mass of the resin.

[0037] The resist underlayer film-forming composition of the present invention can be prepared by dissolving the above-mentioned components in an appropriate solvent, and is used in the form of a homogeneous solution. Examples of such solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, and cyclopentanone. Examples of solvents that can be used include cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. These solvents can be used alone or in combination. Furthermore, these solvents can also be mixed with high-boiling point solvents such as propylene glycol monobutyl ether and propylene glycol monobutyl ether acetate.

[0038] The prepared composition is preferably used after filtering using a filter having a pore size of, for example, 0.2 μm, 0.1 μm, or 0.05 μm. The resist underlayer film-forming composition of the present invention also has excellent long-term storage stability at room temperature. [Example]

[0039] Specific examples of the resist underlayer film-forming composition of the present invention will be described below using the following examples, but the present invention is not limited thereto.

[0040] The apparatus used to measure the weight-average molecular weight of the reaction products obtained in the following synthesis examples is shown below. Apparatus: Tosoh Corporation HLC-8320GPC GPC column: TSKgel Super-MultiporeHZ-N (2 columns) Column temperature: 40℃ Flow rate: 0.35ml / min Eluent: tetrahydrofuran Standard sample: polystyrene

[0041] <Synthesis Example 1> To 65.05 g of propylene glycol monomethyl ether (hereinafter abbreviated as PGME), 10.00 g of 1,6-bis(2,3-epoxypropan-1-yloxy)naphthalene (manufactured by DIC Corporation, trade name: HP-4032D), 7.72 g of 1,8-octanedicarboxylic acid, and 0.54 g of ethyltriphenylphosphonium bromide as a catalyst were added, and the mixture was reacted at 140°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 4,400 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1a): [ka]

[0042] <Synthesis Example 2> To 65.57 g of PGME, 8.00 g of a diepoxy compound (trade name: RE303S-L, manufactured by Nippon Kayaku Co., Ltd.), 7.94 g of 1,8-octanedicarboxylic acid, and 0.46 g of ethyltriphenylphosphonium bromide as a catalyst were added, and the mixture was reacted at 140°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed that the weight-average molecular weight, calculated as standard polystyrene, was 4,500. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1b): [ka]

[0043] <Synthesis Example 3> To 65.35 g of PGME, 9.00 g of diepoxy compound (trade name: YX4000, manufactured by Mitsubishi Chemical Corporation), 6.89 g of 1,8-octanedicarboxylic acid, and 0.45 g of ethyltriphenylphosphonium bromide as a catalyst were added, and the mixture was reacted at 140°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed that the weight-average molecular weight, calculated as standard polystyrene, was 5,600. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1c): [ka]

[0044] <Synthesis Example 4> To 123.90 g of PGME, 18.00 g of a diepoxy compound (trade name: RE810-NM, manufactured by Nippon Kayaku Co., Ltd.), 11.96 g of 1,8-octanedicarboxylic acid, 0.78 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.23 g of hydroquinone as a radical trap were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 6,500 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1d): [ka]

[0045] <Synthesis Example 5> To 65.15 g of PGME, 10.00 g of a diepoxy compound (trade name: RE810-NM, manufactured by Nippon Kayaku Co., Ltd.), 5.72 g of 1,6-hexanedicarboxylic acid, 0.44 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.13 g of hydroquinone as a radical trap were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 5,900 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1e): [ka]

[0046] <Synthesis Example 6> To 72.62 g of PGME, 10.00 g of a diepoxy compound (trade name: RE810-NM, manufactured by Nippon Kayaku Co., Ltd.), 7.67 g of 1,10-dodecanedicarboxylic acid, 0.44 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.13 g of hydroquinone as a radical trap were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 5,400 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1f): [ka]

[0047] <Synthesis Example 7> To 64.88 g of PGME, 10.00 g of a diepoxy compound (trade name: RE810-NM (manufactured by Nippon Kayaku Co., Ltd.)), 5.66 g of cis-1,4-cyclohexanedicarboxylic acid, 0.44 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.13 g of hydroquinone as a radical trap were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 5,400 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1g): [ka]

[0048] <Synthesis Example 8> To 40.51 g of PGME, 6.00 g of a diepoxy compound (trade name: RE810-NM (manufactured by Nippon Kayaku Co., Ltd.)), 3.79 g of 1,3-adamantanedicarboxylic acid, 0.26 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.078 g of hydroquinone as a radical trap were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing the reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 2,200 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1h): [ka]

[0049] <Synthesis Example 9> To 36.25 g of PGME, 6.00 g of a diepoxy compound (trade name: RE810-NM, manufactured by Nippon Kayaku Co., Ltd.), 2.72 g of 2,3-norbornanedicarboxylic acid, 0.26 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.078 g of hydroquinone as a radical trap were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 1,600 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1i): [ka]

[0050] <Synthesis Example 10> To 72.88 g of PGME, 10.00 g of monoallyl diglycidyl isocyanurate (manufactured by Shikoku Chemical Industry Co., Ltd., trade name: MA-DGIC), 7.89 g of 3,3'-dithiodipropionic acid (manufactured by SC Organic Chemical Co., Ltd., trade name: DTDPA), and 0.33 g of ethyltriphenylphosphonium bromide as a catalyst were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed that the weight-average molecular weight, calculated as standard polystyrene, was 5,300. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1j): [ka]

[0051] <Synthesis Example 11> To 110.51 g of PGME, 15.00 g of diglycidyl terephthalate (manufactured by Nagase ChemteX Corporation, trade name: EX-711), 11.65 g of 3,3'-dithiodipropionic acid (manufactured by SC Organic Chemical Co., Ltd., trade name: DTDPA), and 0.98 g of ethyltriphenylphosphonium bromide as a catalyst were added, and the mixture was reacted at 105°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the obtained reaction product revealed that the weight average molecular weight, calculated as standard polystyrene, was 4,900. The obtained reaction product was a propylene glycol ester represented by the following formula (1 k) and is presumed to be a copolymer having repeating structural units. [ka]

[0052] <Synthesis Example 12> To 289.49 g of PGME, 15.00 g of 1,6-bis(2,3-epoxypropan-1-yloxy)naphthalene (manufactured by DIC Corporation, product name: HP-4032D), 23.10 g of monoallyl diglycidyl isocyanurate (manufactured by Shikoku Chemical Industry Co., Ltd., product name: MA-DGIC), 31.72 g of 3,3'-dithiodipropionic acid (manufactured by SC Organic Chemical Co., Ltd., product name: DTDPA), and 2.55 g of ethyltriphenylphosphonium bromide as a catalyst were added, and the mixture was reacted at 105 °C for 24 hours to obtain a solution containing the reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 4,500 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1n): [ka]

[0053] <Synthesis Example 13> To 146.03 g of PGME, 40.00 g of a diepoxy compound (trade name: RE810-NM (manufactured by Nippon Kayaku Co., Ltd.)), 18.58 g of cis-1,2-cyclohexyldicarboxylic acid, 3.48 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.52 g of hydroquinone as a radical trap were added, and the mixture was reacted at 140°C for 24 hours to obtain a solution containing the reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 2,200 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (11): [ka]

[0054] <Synthesis Example 14> To 148.30 g of PGME, 40.00 g of diepoxy compound YX4000 (manufactured by Mitsubishi Chemical Corporation), 19.54 g of cis-1,2-cyclohexyldicarboxylic acid, and 4.01 g of ethyltriphenylphosphonium bromide as a catalyst were added, and the mixture was reacted at 140°C for 24 hours to obtain a solution containing a reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 1.900 in terms of standard polystyrene. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1m): [ka]

[0055] <Synthesis Example 15> To 57.97 g of PGME, 20.00 g of a diepoxy compound (trade name: RE810-NM, manufactured by Nippon Kayaku Co., Ltd.), 16.65 g of 2,2-bis(3-allyl-4-hydroxyphenyl)propane (trade name: BPA-CA, manufactured by Konishi Chemical Industry Co., Ltd.), 1.74 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.26 g of hydroquinone as a radical trap were added, and the mixture was reacted at 140°C for 24 hours to obtain a solution containing the reaction product. GPC analysis of the resulting reaction product revealed a weight-average molecular weight of 16,000 in terms of standard polystyrene. The resulting reaction product is presumed to be a polymer having a repeating structural unit represented by the following formula (1p): [ka]

[0056] <Synthesis Example 16> To 215.23 g of PGME, 30.00 g of RE810-NM (trade name, manufactured by Nippon Kayaku Co., Ltd.) as a diepoxy compound, 22.16 g of 1,8-octanedicarboxylic acid, 1.27 g of ethyltriphenylphosphonium bromide as a catalyst, and 0.38 g of hydroquinone as a radical trap were added, and the mixture was reacted at 105°C for 24 hours to obtain a reaction product. A solution was obtained. GPC analysis of the resulting reaction product revealed that the weight average molecular weight, calculated in terms of standard polystyrene, was 5,000. The resulting reaction product is presumed to be a copolymer having a repeating structural unit represented by the following formula (1o): [ka]

[0057] [Preparation of Resist Underlayer Film-Forming Composition] Example 1 3.69 g of a solution containing 0.56 g of the copolymer obtained in Synthesis Example 1 (the solvent was the PGME used in the synthesis) was mixed with 3.46 g of PGME, 2.83 g of propylene glycol monomethyl ether acetate (hereinafter abbreviated as PGMEA in this specification), 0.021 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0006 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 5.8 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0058] <Example 2> 3.37 g of PGME, 2.83 g of PGMEA, 0.021 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0006 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) were mixed with 3.79 g of a solution containing 0.56 g of the copolymer obtained in Synthesis Example 2 above (the solvent was the PGME used during synthesis) to prepare a 5.8 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0059] Example 3 3.52 g of PGME, 2.83 g of PGMEA, 0.021 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0006 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) were mixed with 3.63 g of a solution containing 0.56 g of the copolymer obtained in Synthesis Example 3 above (the solvent was the PGME used during synthesis) to prepare a 5.8 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0060] Example 4 126.18 g of the solution containing 20.66 g of the copolymer obtained in Synthesis Example 4 (the solvent was the PGME used in the synthesis) was mixed with 110.47 g of PGME, 110.47 g of PGMEA, 0.77 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.021 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.5 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0061] <Example 5> 6.33 g of the solution containing 1.08 g of the copolymer obtained in Synthesis Example 5 (the solvent was the PGME used in the synthesis) was mixed with 7.97 g of PGME, 5.66 g of PGMEA, 0.040 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0011 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 5.6 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter having a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0062] Example 6 7.71 g of PGME, 5.66 g of PGMEA, 0.040 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0011 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) were mixed with 6.59 g of a solution containing 1.08 g of the copolymer obtained in Synthesis Example 6 above (the solvent was the PGME used during synthesis) to prepare a 5.6 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0063] Example 7 8.78 g of a solution containing 1.44 g of the copolymer obtained in Synthesis Example 7 (the solvent was the PGME used in the synthesis) was mixed with 9.12 g of PGME, 7.05 g of PGMEA, 0.054 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0014 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.0 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0064] Example 8 8.61 g of a solution containing 1.44 g of the copolymer obtained in Synthesis Example 8 (the solvent was the PGME used in the synthesis) was mixed with 9.28 g of PGME, 7.05 g of PGMEA, 0.054 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0014 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.0 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0065] Example 9 7.84 g of a solution containing 1.44 g of the copolymer obtained in Synthesis Example 9 (the solvent was the PGME used in the synthesis) was mixed with 10.06 g of PGME, 7.05 g of PGMEA, 0.054 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0014 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.0 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0066] Example 10 3.74 g of a solution containing 0.64 g of the copolymer obtained in Synthesis Example 10 (the solvent was the PGME used in the synthesis) was mixed with 3.44 g of PGME, 2.80 g of PGMEA, 0.024 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.00064 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.6 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0067] Example 11 4.06 g of a solution containing 0.64 g of the copolymer obtained in Synthesis Example 11 (the solvent was the PGME used in the synthesis) was mixed with 3.11 g of PGME, 2.80 g of PGMEA, 0.024 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.00064 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.6 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0068] Example 12 6.29 g of PGME, 0.023 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.030 g of gallic acid hydrate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.00061 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) were mixed with 3.66 g of a solution containing 0.61 g of the copolymer obtained in Synthesis Example 12 above (the solvent was the PGME used during synthesis) to prepare a 6.6 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0069] Example 13 7.39 g of PGME, 4.24 g of PGMEA, 0.024 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.00086 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) were mixed with 3.34 g of a solution containing 0.86 g of the copolymer obtained in Synthesis Example 13 above (the solvent was the PGME used during synthesis) to prepare a 5.9 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0070] Example 14 7.48 g of PGME, 4.23 g of PGMEA, 0.024 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.00086 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) were mixed with 3.26 g of a solution containing 0.86 g of the copolymer obtained in Synthesis Example 14 above (the solvent was the PGME used during synthesis) to prepare a 5.9 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0071] Example 15 6.21 g of PGME, 0.022 g of 5-sulfosalicylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.00060 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) were mixed with 3.77 g of a solution containing 0.60 g of the copolymer obtained in Synthesis Example 10 above (the solvent was the PGME used during synthesis) to prepare a 6.2 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0072] Example 16 36.15 g of a solution containing 5.38 g of the copolymer obtained in Synthesis Example 16 (the solvent was the PGME used in the synthesis) was mixed with 35.31 g of PGME, 28.32 g of PGMEA, 0.22 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0054 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 5.6 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition.

[0073] <Comparative Example 1> 2.63 g of a solution containing 0.50 g of the copolymer obtained in Synthesis Example 4 (the solvent was the PGME used in the synthesis) was mixed with 2.50 g of PGME, 2.81 g of PGMEA, 0.13 g of tetramethoxymethylglycoluril (trade name: Powder Link 1174, manufactured by Nippon Cytec Industries Co., Ltd.) as a crosslinking agent (monomer), 0.019 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0005 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.5 mass% solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition. This comparative example is an example in which a crosslinking agent is included as a monomer.

[0074] <Comparative Example 2> 3.19 g of a solution containing 0.54 g of the copolymer obtained in Synthesis Example 10 (the solvent was the PGME used in the synthesis) was mixed with 3.86 g of PGME, 2.79 g of PGMEA, 0.14 g of tetramethoxymethylglycoluril (trade name: Powder Link 1174, manufactured by Nippon Cytec Industries Co., Ltd.) as a crosslinking agent (monomer), 0.020 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0005 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 7.0 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition. This comparative example is an example in which a crosslinking agent is included as a monomer.

[0075] <Comparative Example 3> 2.31 g of a solution containing 0.28 g of the copolymer obtained in Synthesis Example 15 (the solvent was the PGME used in the synthesis) was mixed with 1.27 g of PGME, 1.41 g of PGMEA, 0.011 g of pyridinium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.0003 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 5.8 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition. This comparative example is an example in which the copolymer does not contain a —C(═O)—O— group.

[0076] <Comparative Example 4> 3.65 g of a solution containing 0.58 g of the copolymer obtained in Synthesis Example 10 (the solvent was the PGME used in the synthesis) was mixed with 6.33 g of PGME, 0.022 g of trifluoroacetic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.00058 g of a surfactant (manufactured by DIC Corporation, trade name: R-30N) to prepare a 6.0 mass % solution. The solution was filtered using a polytetrafluoroethylene microfilter with a pore size of 0.2 μm to prepare a resist underlayer film-forming composition. This comparative example is an example in which the pKa of the acid catalyst used was greater than −0.5.

[0077] [Photoresist solvent elution test] Each of the resist underlayer film-forming compositions prepared in Examples 1 to 16 and Comparative Examples 1 to 4 was applied to a silicon wafer using a spinner. The wafer was then baked on a hot plate for 1 minute at the temperature shown in Table 1 below to form a resist underlayer film (film thickness: 0.2 μm). These resist underlayer films were immersed in PGME and PGMEA, which are solvents used in photoresist solutions. Table 1 below shows the evaluation results of solvent resistance, with "○" indicating insoluble in both solvents and "×" indicating soluble in both solvents.

[0078] [Optical parameter testing] The resist underlayer film-forming compositions prepared in Examples 1 to 16 and Comparative Examples 1 to 4 were applied to silicon wafers using a spinner. They were then baked on a hot plate for 1 minute at the temperatures shown in Table 1 below to form resist underlayer films (film thickness: 0.2 μm). The refractive index (n value) and extinction coefficient (k value) of these resist underlayer films were measured at wavelengths of 193 nm and 248 nm using an optical ellipsometer (JA Woollam, VUV-VASE VU-302). The results are shown in Table 1 below. For the resist underlayer film to have sufficient antireflection function, the k value at a wavelength of 193 nm is preferably 0.1 or greater.

[0079] [Table 1]

[0080] [Coating test on uneven substrate] To evaluate planarization, a comparison was made between the coating thickness of a trench area (TRENCH) with a trench width of 200 nm and a pitch of 600 nm and an open area (OPEN) without a pattern formed on a 230-nm-thick SiO2 substrate. The resist underlayer film-forming compositions of Examples 1 to 16 and Comparative Examples 1 and 2 were applied to the substrate in a thickness of 200 nm and then baked on a hot plate for 1 minute at the temperature shown in Table 1 to form a resist underlayer film (thickness: 0.2 μm). The step coverage of the substrate was observed using a scanning electron microscope (S-4800) manufactured by Hitachi High-Technologies Corporation, and the planarization was evaluated by measuring the film thickness difference between the trench area (patterned area) and the open area (non-patterned area) of the stepped substrate (the coating step between the trench area and the open area, referred to as "Bias"). The film thickness and coating step values ​​for the trench area and open area are shown in Table 2. The smaller the coating step value, the higher the planarization. In Table 1 above, the evaluation results of the flattening properties are shown with "◯" when the coating step shown in Table 2 below is less than 40 nm, and "×" when it is 40 nm or more.

[0081] [Table 2] When comparing the planarization properties, the coating step difference between the trench area and the open area in Examples 1 to 16 is smaller than the coating step difference between the trench area and the open area in Comparative Examples 1 and 2. Therefore, it can be said that the resist underlayer films obtained from the resist underlayer film-forming compositions of Examples 1 to 16 have good planarization properties. [Industrial Applicability]

[0082] The resist underlayer film-forming composition of the present invention exhibits high reflowability by a baking step after being applied to a substrate, and can be applied evenly to a substrate having unevenness to form a flat film. In addition, since the composition has an appropriate antireflection effect, it is useful as a resist underlayer film-forming composition.

Claims

1. a resin having a repeating structural unit containing a -C(=O)-O- group in the main chain and a repeating structural unit containing a hydroxy group in the side chain, or a repeating structural unit containing a -C(=O)-O- group in the main chain and a hydroxy group in the side chain, wherein these repeating structural units do not contain an epoxy ring or an oxetane ring; An acid catalyst or a salt thereof, wherein when the acid catalyst is a monobasic acid, the acid dissociation constant pKa in water at 25°C is -0.5 or less, and when the acid catalyst is a polybasic acid, the acid dissociation constant pKa in water at 25°C is -0.5 or less. １ an acid catalyst or a salt thereof having a β- Solvent and and A resist underlayer film-forming composition that does not contain a crosslinking agent that is a monomer, the acid catalyst is p-toluenesulfonic acid, p-phenolsulfonic acid, 5-sulfosalicylic acid, or trifluoromethanesulfonic acid; the salt of the acid catalyst is p-toluenesulfonate, p-phenolsulfonate, 5-sulfosalicylate, or trifluoromethanesulfonate; A resist underlayer film-forming composition.

2. 2. The resist underlayer film-forming composition according to claim 1, wherein the cation component of the trifluoromethanesulfonate is a primary to quaternary ammonium ion, a pyridinium ion which may have a substituent, an imidazolium ion which may have a substituent, an iodonium ion which may have a substituent, a sulfonium ion which may have a substituent, or a pyrylium ion which may have a substituent.

3. The resist underlayer film-forming composition according to claim 1 or 2, further comprising a compound represented by the following formula (2), formula (3), or formula (4): 【Chemical 1】 (wherein X represents a carbonyl group or a methylene group, l and m each independently represent an integer of 0 to 5 satisfying the relational formula 3≦l+m≦10, R ３ and R ４ each independently represents an alkylene or alkenylene group having 1 to 4 carbon atoms or a single bond, n and p each independently represent an integer of 2 to 4, and the substituent in formula (4) can be substituted at any of the 1- to 8-positions of the naphthalene ring.

4. The resist underlayer film forming composition according to claim 1 , further comprising a surfactant.

5. A laminate comprising a resist underlayer film formed from the resist underlayer film forming composition described in any one of claims 1 to 4 on a semiconductor substrate having a step.

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