JP2012013872A - Resist underlayer film forming composition comprising ionic liquid and method for forming resist pattern using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for forming a resist underlayer film comprising an ionic liquid which can form a resist underlayer film having an antistatic function and solvent resistance, and to provide a method for forming a resist pattern using the resist underlayer film formed from the composition.SOLUTION: A composition for forming a resist underlayer film comprises at least one kind of an ionic liquid having an anion structure represented by the following formula (1): (in the formula, R represents an alkyl group having 1 to 10 carbon atoms), a polymer having a crosslinking moiety, a crosslinking agent, a compound for facilitating crosslinking reaction and an organic solvent.

Description

  The present invention relates to a resist underlayer film forming composition and a method for forming a resist pattern using a resist underlayer film formed from the composition, and more specifically, a resist underlayer film forming composition containing an ionic liquid, The present invention relates to a composition capable of forming a resist underlayer film having an antistatic function and solvent resistance and a method for forming a resist pattern using a resist underlayer film formed from the composition.

Conventionally, in the manufacture of semiconductor devices, fine processing by lithography using a photoresist composition has been performed. The fine processing was obtained by forming a thin film of a photoresist composition on a silicon wafer, irradiating it with an actinic ray such as ultraviolet rays through a mask pattern on which a semiconductor device pattern was drawn, and developing it. This is a processing method of etching a silicon wafer using a resist pattern as a protective film.
Therefore, conventionally various resist underlayer film forming compositions have been reported.

Incidentally, electron beam (EB) lithography is one of candidates for manufacturing a photolithographic mask in a semiconductor process and next-generation advanced microfabrication technology. Electron beam lithography has advantages over optical lithography, such as the formation of fine patterns and no influence of standing waves from the substrate under the resist.
However, the electron beam lithography technique has a problem that electrons are easily charged up on the resist surface during exposure of the electron beam.

  Thus, as an antistatic measure, for example, an antistatic film-forming composition for forming an antistatic film on an upper layer of an electron beam resist that includes a water-soluble resin and an ionic liquid has been proposed (Patent Document 1). However, this composition merely prevents the charge-up of the electron beam resist surface by forming an antistatic film on the upper layer of the electron beam resist. The composition does not contain a crosslinking agent, and is not crosslinked at the time of film formation, and the formed antistatic film is removed by a developer. In addition, an ionizing radiation curable composition for forming an antistatic film using a polymer in which a constituent unit of an ionic monomer is polymerized to occupy 20 to 100 mol% has been proposed (Patent Document 2). However, the composition is cured by using ionizing radiation (for example, ultraviolet rays) to form an antistatic film, and Patent Document 2 does not give any suggestion on the application of such a composition to electron beam lithography.

JP 2010-020046 A JP 2006-045425 A

  In the electron beam lithography technology, in addition to the above problems, the backscattering of the electron beam from the substrate during electron beam exposure causes a reduction in lithography accuracy, and the resist pattern collapses as the electron beam exposure is miniaturized. There is also a problem.

Here, as one proposal for solving this problem, it is conceivable to impart an antistatic function to the resist underlayer film. However, various resist underlayer film forming compositions have been reported so far, but no resist underlayer film forming composition capable of forming a resist underlayer film imparted with an antistatic function has been proposed. In addition, it is not sufficient to simply provide an antistatic function to the resist underlayer film, and it has an antistatic function and has resistance to solvents, suppression of sublimates generated from the resist underlayer film, and a highly accurate good resist pattern. It is also necessary to satisfy general characteristics required for a resist underlayer film for electron beam lithography or the like that enables formation.

  Therefore, the present invention has been made based on the above circumstances, and the problem to be solved is to form a resist underlayer film having an antistatic function and satisfying the characteristics required for the resist underlayer film. It is to provide a resist underlayer film forming composition capable of forming a resist pattern and a method for forming a resist pattern using a resist underlayer film formed from the composition.

As a result of intensive studies to achieve the above object, the inventors of the present invention have included an ionic liquid having an anion structure represented by the following formula (1) in the resist underlayer film forming composition. The present inventors have found that an antistatic function is imparted to the resist underlayer film to be formed, thereby completing the present invention.
That is, the present invention provides a resist underlayer film formation comprising at least one ionic liquid having an anion structure represented by the following formula (1), a polymer having a crosslinking site, a crosslinking agent, a compound for promoting a crosslinking reaction, and an organic solvent. It is a composition.
(In the formula, R represents an alkyl group having 1 to 10 carbon atoms.)

The present invention includes an antistatic function capable of preventing scattering of electron beams by including an ionic liquid having an anion structure represented by the above formula (1) in the resist underlayer film forming composition. It is possible to provide a resist underlayer film having excellent solvent resistance equivalent to the case where no ionic liquid is contained.
Further, the resist underlayer film forming composition of the present invention is equivalent to or less than the case where the amount of sublimate generated when forming the resist underlayer film does not include the ionic liquid having the anion structure represented by the above formula (1). The effect of being able to be suppressed is obtained.
Furthermore, the present invention can form a good resist pattern with high accuracy by forming a resist underlayer film having the above-mentioned effects and performance.

FIG. 1 is a photograph taken immediately after reducing the magnification from 1000 times to 400 times in a cross-sectional SEM image of a resist underlayer film formed using the resist underlayer film forming composition prepared in Example 1. FIG. 2 is a photograph taken immediately after reducing the magnification from 1000 times to 400 times in the cross-sectional SEM image of the resist underlayer film formed using the resist underlayer film forming composition prepared in Example 2. FIG. 3 is a photograph taken immediately after reducing the magnification from 1000 times to 400 times in the cross-sectional SEM image of the resist underlayer film formed using the resist underlayer film forming composition prepared in Example 5. FIG. 4 is a photograph taken immediately after reducing the magnification from 1000 times to 400 times in the cross-sectional SEM image of the resist underlayer film formed using the resist underlayer film forming composition prepared in Example 6. FIG. 5 is a photograph taken immediately after reducing the magnification from 1000 times to 400 times in the cross-sectional SEM image of the resist underlayer film formed using the resist underlayer film forming composition prepared in Example 7. 6 is a photograph taken immediately after the magnification was reduced from 1000 times to 400 times in the cross-sectional SEM image of the resist underlayer film formed using the resist underlayer film forming composition prepared in Example 8. FIG. FIG. 7 is a photograph taken immediately after reducing the magnification from 1000 times to 400 times in the cross-sectional SEM image of the resist underlayer film formed using the resist underlayer film forming composition prepared in Comparative Example 1. FIG. 8 is a cross-sectional SEM image of the resist pattern on the resist underlayer film formed using the resist underlayer film forming composition prepared in Example 1. FIG. 9 is a cross-sectional SEM image of a resist pattern on a resist underlayer film formed using the resist underlayer film forming composition prepared in Example 2. FIG. 10 is a cross-sectional SEM image of a resist pattern on a resist underlayer film formed using the resist underlayer film forming composition prepared in Example 5.

  The resist underlayer film forming composition of the present invention comprises at least one ionic liquid having an anionic structural unit represented by the above formula (1), a polymer having a crosslinking site, a crosslinking agent, a compound for promoting a crosslinking reaction, and an organic solvent. Including. Further, the resist underlayer film forming composition of the present invention can further contain a surfactant or the like.

  The ratio of the components excluding the organic solvent in the resist underlayer film forming composition of the present invention is, for example, 0.1 to 15% by mass, or 1.0 to 10.0% by mass.

Hereinafter, the resist underlayer film forming composition of the present invention will be described in detail.
<Ionic liquid>
The ionic liquid contained in the resist underlayer film forming composition of the present invention has an anion structure represented by the following formula (1). By including such an ionic liquid, it becomes possible to impart an antistatic function to the resist underlayer film formed from the resist underlayer film forming composition of the present invention.
(In the formula, R represents an alkyl group having 1 to 10 carbon atoms.)

  Preferably R is from 1 to 6 carbon atoms. Two or more ionic liquids having an anion structure represented by the formula (1) may be mixed and used.

  The cation of the ionic liquid is not particularly limited, and examples thereof include an imidazolium cation, a pyridinium cation, a pyrrolidinium cation, a phosphonium cation, an ammonium cation, and a sulfonium cation.

Examples of the imidazolium cation include the following formulas (2-1) to (2-17).

Examples of the pyridinium cation include the following formulas (3-1) to (3-4).

Examples of the pyrrolidinium cation include the following formulas (4-1) to (4-8).

Examples of the phosphonium cation include the following formulas (5-1) to (5-4).

Examples of the ammonium cation include the following formulas (6-1) to (6-9).

Examples of the sulfonium cation include the following formulas (7-1) to (7-4).

  The blending amount of the ionic liquid is 1.0 to 90% by mass, preferably 5.0 to 70% by mass, more preferably based on the mass of the polymer having a crosslinking site contained in the resist underlayer film forming composition of the present invention. Is 5.0 to 50 mass%. If the blending amount of the ionic liquid is less than 5.0% by mass, the resist underlayer film cannot be provided with a sufficient antistatic function, while if it exceeds 90% by mass, the composition is cured to form a resist underlayer film. This is because it takes time to form.

<Polymer having cross-linked site>
The polymer having a crosslinking site refers to a polymer having a functional group capable of undergoing a crosslinking reaction. For example, a resin having a crosslinking site such as a hydroxy group, a carboxyl group, or an amino group. Examples of the resin include acrylic resins, methacrylic resins, novolac resins, phenol resins, polyesters, natural polymers, melamine resins, and Examples thereof include siloxane resins. The polymer needs to be soluble in any of the organic solvents described below.

The weight average molecular weight of the polymer having the crosslinking site is usually 2,000 to 50,000. This is because if the weight average molecular weight of the polymer having a cross-linked site is less than 2,000, the solvent resistance may be insufficient, while if the weight average molecular weight is too large, there may be a problem in resolution. The weight average molecular weight is a value obtained by using gel as a standard sample by gel permeation chromatography (GPC).
The polymer having the crosslinking site is, for example, 0.5 to 95% by mass, or 1.0 to 90% by mass based on the content in the component excluding the organic solvent of the resist underlayer film forming composition of the present invention. . This is because when this ratio is too small or too large, solvent resistance may be difficult to obtain.

<Crosslinking agent>
The crosslinking agent is, for example, a nitrogen-containing compound having 2 to 4 nitrogen atoms substituted with a methylol group or an alkoxymethyl group in the molecule. By adding a crosslinking agent, the crosslinking agent reacts with a hydroxyl group or the like in the polymer having the crosslinking site, and the resist underlayer film formed by crosslinking is strengthened. And it becomes a resist underlayer film with low solubility with respect to an organic solvent. A crosslinking agent may use only 1 type and can be used in combination of 2 or more type.
Specific examples of the crosslinking agent include hexamethoxymethyl melamine, tetramethoxymethyl benzoguanamine, 1,3,4,6-tetrakis (methoxymethyl) glycoluril, 1,3,4,6-tetrakis (butoxymethyl) glycoluril, 1 , 3,4,6-tetrakis (hydroxymethyl) glycoluril, 1,3-bis (hydroxymethyl) urea, 1,1,3,3-tetrakis (butoxymethyl) urea, and 1,1,3,3- Examples include tetrakis (methoxymethyl) urea.

The amount of the crosslinking agent can be added to the polymer having a crosslinking site contained in the resist underlayer film forming composition of the present invention, for example, at a ratio of 1% by mass to 30% by mass. This is because when this ratio is too small or too large, it is difficult to obtain the solvent resistance of the resist underlayer film.

<Compound that promotes crosslinking reaction>
The compound that promotes the crosslinking reaction refers to a compound that promotes the crosslinking reaction between the polymer having a crosslinking site and the crosslinking agent, and examples thereof include sulfonic acid compounds.
Examples of the sulfonic acid compound include p-toluenesulfonic acid, trifluoromethanesulfonic acid, pyridinium-p-toluenesulfonate, camphorsulfonic acid, 5-sulfosalicylic acid, 4-chlorobenzenesulfonic acid, 4-hydroxybenzenesulfonic acid, Examples thereof include benzenedisulfonic acid and 1-naphthalenesulfonic acid.
The compounding amount of the compound for promoting the crosslinking reaction may be added, for example, at a ratio of 0.1% by mass or more and 10% by mass or less with respect to the polymer having a crosslinking site contained in the resist underlayer film forming composition of the present invention. it can. When this ratio is too small, the crosslinking reaction cannot be promoted sufficiently.

<Organic solvent>
The organic solvent is not particularly limited as long as each of the above components can be dissolved. For example, 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, methoxybutanols, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, 2-hydroxy Ethyl-2-methylpropionate, eth Ethyl ethyl acetate, hydroxy hydroxyethyl, 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, N-methylpyrrolidone and the like can be used. Further, a high boiling point solvent such as propylene glycol monobutyl ether and propylene glycol monobutyl ether acetate can be used by mixing with the organic solvent. These organic solvents can be used individually or in combination of 2 or more types.

  Furthermore, the resist underlayer film forming composition of the present invention may contain a rheology adjuster, an adhesion aid, a surfactant, and the like as necessary.

  The rheology modifier can be added mainly for the purpose of improving the fluidity of the resist underlayer film forming composition. Examples of the rheology modifier include phthalic acid derivatives such as dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dihexyl phthalate, and butyl isodecyl phthalate; , Maleic acid derivatives such as dinormal butyl maleate, diethyl maleate and dinonyl maleate, oleic acid derivatives such as methyl oleate, butyl oleate and tetrahydrofurfuryl oleate, or stearic acid derivatives such as normal butyl stearate and glyceryl stearate be able to. These rheology modifiers are usually blended at a ratio of less than 30% by mass with respect to 100% by mass of the total composition of the resist underlayer film forming composition.

The adhesion auxiliary agent can be added mainly for the purpose of improving the adhesion between the substrate or the resist film and the resist underlayer film and preventing the resist film from being peeled off particularly during development. Examples of the adhesion assistant include chlorosilanes such as trimethylchlorosilane, dimethylvinylchlorosilane, methyldiphenylchlorosilane, chloromethyldimethylchlorosilane, trimethylmethoxysilane, dimethyldiethoxysilane, methyldimethoxysilane, dimethylvinylethoxysilane, diphenyldimethoxysilane, Alkoxysilanes such as phenyltriethoxysilane, hexamethyldisilazane, N, N′-bis (trimethylsilyl) urea, silazanes such as dimethyltrimethylsilylamine, trimethylsilylimidazole, vinyltrichlorosilane, γ-chloropropyltrimethoxysilane, γ -Silanes such as aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, benzotriazole, benz Heterocyclic compounds such as imidazole, indazole, imidazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, urazole, thiouracil, mercaptoimidazole, mercaptopyrimidine, 1,1-dimethylurea, 1,3 -Urea or thiourea compounds such as dimethylurea can be mentioned. The adhesion assistant is usually blended at a ratio of less than 5% by mass, preferably less than 2% by mass with respect to 100% by mass of the total composition of the resist underlayer film forming composition.

  In the resist underlayer film forming composition of the present invention, a surfactant can be blended in order to eliminate the occurrence of pinholes and installations and to further improve the coating property against surface unevenness. Examples of the surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene alkyl ethers such as polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether. Polyoxyethylene alkyl allyl ethers, polyoxyethylene / polyoxypropylene block copolymers, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, sorbitan tristearate, etc. Sorbitan fatty acid esters, polyoxyethylene sorbitan monolaurate, polyoxyethylene sol Nonionic surfactants such as tan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, and other polyoxyethylene sorbitan fatty acid esters, Ftop [registered trademark] EF301, EF303, EF352 (Mitsubishi Materials Electronics Kasei Co., Ltd.), MegaFuck [registered trademark] F171, F173, R30 (DIC Corporation), Florard FC430, FC431 (Sumitomo 3M) Manufactured by Asahi Guard [registered trademark] AG710, Surflon [registered trademark] S-382, SC101, SC102, SC103, SC104, SC105, SC106 (manufactured by Asahi Glass Co., Ltd.), organosiloxane polymer KP341 Shin-Etsu Chemical Co., Ltd.), can be mentioned Surfynol [registered trademark] (manufactured by Air Products Japan Co., Ltd.), and the like. These surfactants may be added alone or in combination of two or more. The surfactant is usually 3% by mass or less, preferably 1% by mass, more preferably 0.5% by mass or less based on the content of the resist underlayer film forming composition of the present invention in the components excluding the organic solvent. Blended in proportions.

  The resist underlayer film forming composition (solution) thus prepared is preferably used after being filtered using a filter or the like having a pore size of usually about 0.2 μm or about 0.1 μm. The resist underlayer film forming composition thus prepared is also excellent in long-term storage stability at room temperature.

  Hereinafter, the use of the resist underlayer film forming composition of the present invention will be described.

Substrate {for example, a semiconductor substrate such as silicon coated with a silicon oxide film, a semiconductor substrate such as silicon coated with a silicon nitride film or a silicon oxynitride film, a silicon nitride substrate, a quartz substrate, a glass substrate (non-alkali glass, low (Including alkali glass, crystallized glass), glass substrate on which an ITO film is formed, etc.}, the resist underlayer film forming composition of the present invention is applied by an appropriate application method such as a spinner or coater, and then hot plate A resist underlayer film is formed by baking using a heating means such as the above.

  The baking conditions are appropriately selected from a baking temperature of 80 to 250 ° C. and a baking time of 0.3 to 60 minutes, preferably a baking temperature of 130 to 250 ° C. and a baking time of 0.5 to 5 minutes. When the baking temperature is lower than the above range, the crosslinked structure in the resist underlayer film becomes insufficient, and the resist underlayer film may cause intermixing with the resist. On the other hand, when the baking temperature is too high, the cross-linked structure in the resist underlayer film may be cut, and the resist underlayer film may cause intermixing with the resist.

  The film thickness of the resist underlayer film formed from the resist underlayer film forming composition of the present invention is usually 0.01 to 3.0 μm, more preferably 0.01 to 1.0 μm.

  The resist underlayer film formed from the resist underlayer film forming composition of the present invention has a cross-linked structure by reacting with a hydroxy group in a polymer having a cross-linked site and a cross-linking agent according to the baking conditions at the time of formation and cross-linking. It becomes a strong film. For this reason, the resist underlayer film formed from the resist underlayer film forming composition of the present invention does not cause intermixing with the resist. The resist underlayer film is a resist solution to be coated thereon, and generally used organic solvents such as ethylene glycol monomethyl ether, ethylene cellosolve acetate, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether , Propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, toluene, methyl ethyl ketone, cyclohexanone, γ-butyrolactone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, methyl pyruvate, lactic acid The solubility in ethyl and butyl lactate is low.

  Next, a resist film is formed on the resist underlayer film. The resist film can be formed by a general method, that is, application and baking of a resist solution on the resist underlayer film.

  The resist formed on the resist underlayer film obtained by the resist underlayer film forming composition of the present invention may be any resist that is sensitive to light or an electron beam. Either a negative type or a positive type can be used as the resist sensitive to the electron beam. Chemically amplified resist containing a binder having a group that changes the alkali dissolution rate by being decomposed by an acid and an acid generator, a low molecular weight compound that is decomposed by an acid to change the alkali dissolution rate of the resist, an alkali-soluble binder, and an acid A chemically amplified resist containing a generator, a binder having a group that decomposes with an acid to change the alkali dissolution rate, a low-molecular compound that decomposes with an acid to change the alkali dissolution rate of the resist, and an acid generator A chemically amplified resist, a non-chemically amplified resist containing a binder having a group that changes the alkali dissolution rate by being decomposed by an electron beam, and a binder containing a binder having a site that is cut by an electron beam to change the alkali dissolution rate There are chemical amplification resists.

Further, in a method for forming a resist pattern used for manufacturing a semiconductor manufacturing apparatus, exposure is performed through a mask (reticle) for forming a predetermined pattern. However, in the case of electron beam exposure, a mask (reticle) is not required. An electron beam can be used for exposure, and a KrF excimer laser, an ArF excimer laser, or extreme ultraviolet (EUV) can also be used. After exposure, if necessary, post-exposure heating (Post Exposure B
ake) is performed. The conditions for the post-exposure heating are appropriately selected from heating temperatures of 80 to 150 ° C. and heating times of 0.3 to 60 minutes. A semiconductor device is manufactured by a process in which a semiconductor substrate covered with a resist underlayer film and a resist film is exposed and then developed. The resist underlayer film formed from the resist underlayer film forming composition of the present invention becomes soluble in an alkaline developer by the action of an acid which is a compound that promotes a crosslinking reaction contained in the resist film during exposure. After the exposure, when the resist film and the resist underlayer film are collectively developed with an alkaline developer, the exposed portions of the resist film and the resist underlayer film are removed because they exhibit alkali solubility.

  As a developer used for developing the resist film, inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, and aqueous ammonia, and primary amines such as ethylamine and n-propylamine are used. , Secondary amines such as diethylamine and di-n-butylamine, tertiary amines such as triethylamine and methyldiethylamine, alcohol amines such as dimethylethanolamine and triethanolamine, tetramethylammonium hydroxide, tetraethylammonium An aqueous solution of an alkali such as a quaternary ammonium salt such as hydroxide or choline, or a cyclic amine such as pyrrole or piperidine can be used. Furthermore, an appropriate amount of an alcohol such as isopropyl alcohol or a nonionic surfactant may be added to the alkaline aqueous solution. Of these, preferred developers are quaternary ammonium salts, more preferably tetramethylammonium hydroxide and choline.

  The development conditions are appropriately selected from a development temperature of 5 to 50 ° C. and a development time of 10 to 300 seconds. The resist underlayer film formed from the resist underlayer film forming composition of the present invention is easily developed at room temperature using a 2.38 mass% tetramethylammonium hydroxide aqueous solution that is widely used for developing photoresists. be able to.

  The resist underlayer film formed from the resist underlayer film forming composition of the present invention includes a layer for preventing the interaction between the substrate and the resist film, a material used for the resist film, or a semiconductor of a substance generated upon exposure to the resist. Used as a layer that prevents adverse effects on the substrate, a layer that has the function of preventing diffusion of substances generated from the semiconductor substrate during baking into the upper resist film, and a barrier layer that reduces the poisoning effect of the resist by the dielectric layer It is also possible.

  Hereinafter, the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited to these examples.

[Measurement of weight average molecular weight of polymer]
The weight average molecular weight shown in the following synthesis examples of the present specification is a measurement result by gel permeation chromatography (hereinafter abbreviated as GPC). The measurement conditions etc. are as follows using the Tosoh Co., Ltd. product GPC apparatus for a measurement. Moreover, the dispersity shown in the following synthesis examples of the present specification was calculated from the measured weight average molecular weight and number average molecular weight.
GPC column: Shodex [registered trademark] Asahipak [registered trademark] (manufactured by Showa Denko KK)
Column temperature: 40 ° C
Solvent: N, N-dimethylformamide (DMF)
Flow rate: 0.6 ml / min Standard sample: Standard polystyrene sample (manufactured by Tosoh Corporation)
Detector: RI detector (manufactured by Tosoh Corporation, RI-8020)
[Measurement of resist underlayer thickness]
The film thickness described in Table 1 of the present specification is a film thickness measuring device NanoSpec / AFT5100 (N
Anometrics).

<Synthesis Example 1>
Monoallyl diglycidyl isocyanuric acid (manufactured by Shikoku Chemicals Co., Ltd.) 10.0 g, 5-hydroxyisophthalic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) 6.6 g, and ethyltriphenylphosphonium bromide (manufactured by Kanto Chemical Co., Ltd.) ) 0.67 g was added and dissolved in 68.9 g of propylene glycol monomethyl ether. The reaction vessel was purged with nitrogen and reacted at 135 ° C. for 4 hours to obtain a polymer solution. When GPC analysis was performed, the obtained polymer having a structural unit represented by the following formula (8) had a weight average molecular weight of 23,200 in terms of standard polystyrene and a dispersity of 6.5. It is presumed that the obtained polymer has an OH group at the terminal.

<Synthesis Example 2>
Epoxy resin (HP-4032D, manufactured by DIC Corporation) 7.0 g, 5-hydroxyisophthalic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) 4.65 g and ethyltriphenylphosphonium bromide (manufactured by Kanto Chemical Industry Co., Ltd.) 0 .47 g was added to 48.5 g of propylene glycol monomethyl ether and dissolved. The reaction vessel was purged with nitrogen and reacted at 135 ° C. for 4 hours to obtain a polymer solution. When GPC analysis was performed, the obtained polymer having a structural unit represented by the following formula (9) had a weight average molecular weight of 23,600 in terms of standard polystyrene and a dispersity of 3.8. It is presumed that the obtained polymer has an OH group at the terminal.

<Synthesis Example 3>
Monoallyl diglycidyl isocyanuric acid (manufactured by Shikoku Kasei Kogyo Co., Ltd.) 10.0 g, isophthalic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) 5.98 g, and ethyltriphenylphosphonium bromide (manufactured by Kanto Chemical Co., Ltd.) 0. 67 g was added to 66.6 g of propylene glycol monomethyl ether and dissolved. The reaction vessel was purged with nitrogen and reacted at 135 ° C. for 4 hours to obtain a polymer solution. When GPC analysis was performed, the obtained polymer having a structural unit represented by the following formula (10) had a weight average molecular weight of 23,700 in terms of standard polystyrene and a dispersity of 8.2. It is presumed that the obtained polymer has an OH group at the terminal.

<Synthesis Example 4>
7.0 g of cyclohexyl diglycidyl (Sakamoto Yakuhin Kogyo Co., Ltd.), 4.19 g of 5-hydroxyisophthalic acid (Tokyo Kasei Kogyo Co., Ltd.) and ethyl triphenylphosphonium bromide (Kanto Chemical Co., Ltd.) 43 g was added to 17.42 g of propylene glycol monomethyl ether and dissolved. The reaction vessel was purged with nitrogen and reacted at 135 ° C. for 4 hours to obtain a polymer solution. When GPC analysis was performed, the obtained polymer having a structural unit represented by the following formula (11) had a weight average molecular weight of 8,600 and a dispersity of 2.41 in terms of standard polystyrene. The resulting polymer is presumed to have an OH group at the end.

The ionic liquids used in Examples 1 to 8 and Comparative Examples 5 to 9 of the present specification are shown as A to I below.

<Example 1>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of the ionic liquid A, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174 0.09 g, manufactured by Nippon Cytec Industries, Ltd.), 11.90 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Example 2>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 2 above, 0.0092 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid A, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g of Nippon Cytec Industries Co., Ltd.) was mixed, and 12.01 g of propylene glycol monomethyl ether and 1.52 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Example 3>
To 2.00 g of a solution containing 0.36 g of the polymer obtained in Synthesis Example 3 above, 0.0090 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid A, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g (manufactured by Nippon Cytec Industries, Ltd.) was mixed, and 11.65 g of propylene glycol monomethyl ether and 1.48 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Example 4>
To 2.00 g of a solution containing 0.35 g of the polymer obtained in Synthesis Example 4 above, 0.0088 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid A, tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g of Nippon Cytec Industries Co., Ltd.) was mixed, and 11.37 g of propylene glycol monomethyl ether and 1.45 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Example 5>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid G, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g (manufactured by Nippon Cytec Industries Co., Ltd.) was mixed, and 11.90 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Example 6>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid H, tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g (manufactured by Nippon Cytec Industries Co., Ltd.) was mixed, and 11.90 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Example 7>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid I, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g (manufactured by Nippon Cytec Industries Co., Ltd.) was mixed, and 11.90 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Example 8>
Tetramethoxymethylglycoluril (trade name: POWDERLINK [registered] is added to 2.00 g (polymer concentration: 21% by mass) of a solution containing a polymer having a structure represented by the following formula (12) (weight average molecular weight 10,000 in terms of polystyrene). Trademark] 1174, manufactured by Nippon Cytec Industries, Ltd.) 0.10 g, pyridinium-p-toluenesulfonate 0.012 g (manufactured by Tokyo Chemical Industry Co., Ltd.), and ionic liquid G 0.13 g were mixed, and propylene glycol monomethyl ether 13.98 g and propylene glycol monomethyl ether acetate 1.73 g were added to make a solution. Thereafter, the mixture was filtered using a polyethylene microfilter having a diameter of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 1>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1 above, 0.0091 g of 5-sulfosalicylic acid, tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, manufactured by Nippon Cytec Industries Co., Ltd.) ) 0.09 g was mixed, and 11.00 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative example 2>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 2 above, 0.0092 g of 5-sulfosalicylic acid, tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, manufactured by Nippon Cytec Industries Co., Ltd.) ) 0.09 g was mixed and 11.1 g of propylene glycol monomethyl ether and 1.52 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 3>
To 2.00 g of a solution containing 0.36 g of the polymer obtained in Synthesis Example 3 above, 0.0090 g of 5-sulfosalicylic acid, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, manufactured by Nippon Cytec Industries, Ltd. ) 0.09 g was mixed, and 10.76 g of propylene glycol monomethyl ether and 1.48 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative example 4>
To 2.00 g of a solution containing 0.35 g of the polymer obtained in Synthesis Example 4 above, 0.0088 g of 5-sulfosalicylic acid, tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, manufactured by Nippon Cytec Industries Co., Ltd.) ) 0.09 g was mixed, and 10.5 g of propylene glycol monomethyl ether and 1.45 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 5>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid B, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g of Nippon Cytec Industries Co., Ltd.) was mixed, and 11.00 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 6>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid C, tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g of Nippon Cytec Industries Co., Ltd.) was mixed, and 11.00 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 7>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid D, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g of Nippon Cytec Industries Co., Ltd.) was mixed, and 11.00 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 8>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid E, tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g of Nippon Cytec Industries Co., Ltd.) was mixed, and 11.00 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 9>
To 2.00 g of a solution containing 0.37 g of the polymer obtained in Synthesis Example 1, 0.0091 g of 5-sulfosalicylic acid, 0.11 g of ionic liquid F, tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, 0.09 g of Nippon Cytec Industries Co., Ltd.) was mixed, and 11.00 g of propylene glycol monomethyl ether and 1.50 g of propylene glycol monomethyl ether acetate were added and dissolved. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

<Comparative Example 10>
To a solution containing a polymer having a structure represented by the following formula (12 ′) (weight average molecular weight 60000 in terms of polystyrene) (polymer name: 15% by mass), tetramethoxymethylglycoluril (trade name: POWDERLINK [ Registered trademark] 1174, manufactured by Nippon Cytec Industries Co., Ltd.) 0.19 g, pyridinium-p-toluenesulfonate 0.012 g (manufactured by Tokyo Chemical Industry Co., Ltd.), bisphenol S (manufactured by Tokyo Chemical Industry Co., Ltd.) 0. 024 g, 12.67 g of propylene glycol monomethyl ether and 7.17 g of propylene glycol monomethyl ether acetate were added to make a solution. Thereafter, the mixture was filtered using a polyethylene microfilter having a pore size of 0.02 μm to obtain a resist underlayer film forming composition (solution) for lithography.

[Elution test in resist solvent]
The resist underlayer film forming compositions prepared in Examples 1 to 8 and Comparative Examples 1 to 9 were each applied onto a silicon wafer as a semiconductor substrate by a spinner. The silicon wafer was placed on a hot plate and baked at 205 ° C. for 1 minute to form a resist underlayer film. These resist underlayer films were immersed in propylene glycol monomethyl ether (PGME) / propylene glycol monomethyl ether acetate (PGMEA) = 7/3 (mass ratio), and an experiment for confirming whether or not they were insoluble in the solvent was conducted.

From the results of Table 1, the resist underlayer films formed using the resist underlayer film forming compositions of Examples 1 to 8 of the present invention all have a film thickness change of 1 nm or less (1% or less of the initial film thickness). It is clear from some that it has solvent resistance. On the other hand, the resist underlayer films formed using the resist underlayer film forming compositions of Comparative Examples 6 to 9 all did not have solvent resistance.

[Measurement of sublimation amount]
The resist underlayer film forming composition prepared in Examples 1, 2, 5 to 8 and the resist underlayer film forming composition prepared in Comparative Examples 5 and 10 as comparative objects were applied to a silicon wafer having a diameter of 4 inches on a spin coater. Each was applied at 1,500 rpm for 60 seconds. The wafer coated with the resist underlayer film forming composition is set in a sublimation amount measuring device (see International Publication No. 2007/111147 pamphlet) integrated with a hot plate, baked for 120 seconds, and the sublimate is QCM (Quartz). The crystals were collected on a crystal microbalance sensor, that is, a crystal resonator on which an electrode was formed. The QCM sensor can measure a small amount of mass change by utilizing the property that when a sublimate adheres to the surface (electrode) of the crystal unit, the frequency of the crystal unit changes (decreases) according to the mass. .

The detailed measurement procedure is as follows.
The hot plate of the sublimation amount measuring device was heated to 205 ° C., the pump flow rate was set to 1 m ³ / s, and the first 60 seconds were left to stabilize the device. Immediately thereafter, the wafer coated with the resist underlayer film forming composition was quickly put on the hot plate from the slide port, and the sublimate was collected from the time point of 60 seconds to the time point of 180 seconds (120 seconds). The initial film thickness of the resist underlayer film formed on the wafer was 80 nm.

  In addition, the flow attachment (detection part) that connects the QCM sensor and the collection funnel part of the sublimation amount measuring device is used without a nozzle, so that the chamber with a distance of 30 mm from the sensor (quartz crystal unit) is used. The airflow flows from the unit flow path (caliber: 32 mm) without being restricted. The QCM sensor uses a material mainly composed of silicon and aluminum (AlSi) as an electrode, the diameter of the crystal unit (sensor diameter) is 14 mm, the electrode diameter on the surface of the crystal unit is 5 mm, and the resonance frequency is 9 MHz. The thing of was used.

  The obtained frequency change was converted to gram from the eigenvalue of the quartz crystal used for the measurement, and the relationship between the amount of sublimation and the time course of one wafer coated with the resist underlayer film forming composition was clarified. In Table 2, the amount of sublimation (unit: ng: nanogram) indicated by the measuring apparatus from 0 to 180 seconds in Examples 1, 2, 5 to 8 and Comparative Examples 5 and 10 to be compared is shown. Note that the first 60 seconds is a time zone in which the apparatus is left to stabilize the apparatus (no wafer is set), and the amount of sublimation indicated by the measuring apparatus is a negative value to indicate the stable state of the measuring instrument. I read it as it was. Therefore, the measurement value from the time point of 60 seconds to the time point of 180 seconds when the wafer is placed on the hot plate is a measurement value relating to the amount of sublimation of the wafer.

  From the results in Table 2, the resist underlayer film forming compositions of Examples 1, 2, 5 to 8 of the present invention are more suppressed from generating sublimates than the resist underlayer film forming composition of Comparative Example 5. Is clear. Furthermore, the resist underlayer film forming compositions of Examples 1, 2, 5 to 8 of the present invention generate less sublimates than the resist underlayer film forming composition of Comparative Example 10.

[Surface resistance measurement]
The antistatic performance is closely related to the surface resistance value of the film, and it is generally known that the lower the surface resistance value, the better the antistatic performance. Therefore, by measuring the surface resistance value, it is possible to evaluate the antistatic ability although indirectly. The resist underlayer film forming compositions obtained in Examples 1, 2, 5 to 8 and Comparative Examples 1 and 2 were spin-coated on a wafer at 1500 rpm for 60 seconds, and baked at 205 ° C. for 60 seconds to form a resist underlayer film. .
The surface resistance value was measured using a DSM-8103 digital insulation meter (manufactured by Toa DK Corporation). As shown in Table 3, the resist underlayer film formed from the resist underlayer film forming composition containing the ionic liquid obtained in the example has a resistance value one order or more lower than that of the comparative example not containing the ionic liquid. It was confirmed.

[Antistatic performance test]
Each of the resist underlayer film forming compositions obtained in Examples 1 to 8 and Comparative Example 1 was spin-coated on a silicon wafer. A resist underlayer film was formed by baking at 205 ° C. for 60 seconds. The wafer was cut into 1 cm square, and an antistatic property test was performed with a cross-sectional SEM (S-4800, manufactured by Hitachi, Ltd.). The antistatic performance was determined by irradiating the sample with an electron beam under a constant accelerating voltage and extraction current, and determining the size of the antistatic property based on the magnitude of image burn-in obtained by SEM (scanning electron microscope). The test was performed at an acceleration voltage of 1.5 kV and an extraction current of 10 μA. In the test, the magnification was maintained at 1000 times for 5 seconds, and then the magnification was returned to 400 times to immediately take a photograph, and the contrast of images charged when enlarged to 1000 times was compared. In the resist underlayer film formed from the resist underlayer film forming composition containing the ionic liquid obtained in the examples, the image contrast after enlargement and reduction is sufficiently smaller than that of the comparative example not containing the ionic liquid. The antistatic performance was confirmed. If the sample is charged up (charged), the image at 1000 times remains as a black image even if the image at 1000 times magnification is reduced to 400 times, but if the sample is not charged up, 1000 times remains. When the double-time video is changed to the 400-time video, a video (afterimage is difficult to attach) of the 1000x video is displayed. 1 to 7 show cross-sectional SEM images when the resist underlayer film forming compositions obtained in Examples 1, 2, 5 to 8 and Comparative Example 1 were used.

[Formation of resist pattern]
The resist underlayer film forming compositions prepared in Examples 1 to 8 were applied onto a silicon wafer using a spinner. Heating was performed at 205 ° C. for 1 minute on a hot plate to form a resist underlayer film having a thickness of 20 to 80 nm. On this resist underlayer film, a commercially available resist solution (manufactured by Sumitomo Chemical Co., Ltd., trade name: PAR855) is applied by a spinner and heated on a hot plate at 105 ° C. for 60 seconds to form a resist film (film thickness 0). .10 μm) was formed.

Next, exposure was performed through a photomask using a scanner made by Nikon Corporation, NSR-S307E (wavelength 193 nm, NA: 0.85, σ: 0.65 / 0.93 (ANNNULAR)). The photomask was selected according to the resist pattern to be formed. After exposure, on the hot plate, post exposure bake (PEB) is performed at 105 ° C. for 60 seconds, and after cooling, 0.26N tetramethylammonium hydroxide aqueous solution as a developer in an industrial standard 60 second single paddle process. Developed using When the cross-sectional shape of the resist pattern in the direction perpendicular to the substrate (silicon wafer) was observed with a cross-sectional SEM, it was confirmed that the target resist pattern was formed. The cross-sectional SEM images of the resist pattern on the resist underlayer film formed using the resist underlayer film forming composition prepared in Examples 1, 2, and 5 are shown in FIGS.

Claims (6)

Following formula (1):
(In the formula, R represents an alkyl group having 1 to 10 carbon atoms.)
A resist underlayer film-forming composition comprising at least one ionic liquid having an anion structure represented by formula (1), a polymer having a crosslinking site, a crosslinking agent, a compound for promoting a crosslinking reaction, and an organic solvent.   2. The resist underlayer film forming composition according to claim 1, wherein the ionic liquid is contained in an amount of 5 to 50% by mass with respect to the mass of the polymer having the crosslinking site.   The resist underlayer film forming composition according to claim 1 or 2, wherein the polymer having a crosslinking site is an acrylic resin, a methacrylic resin, or a polyester.   The resist underlayer film forming composition according to any one of claims 1 to 3, wherein the crosslinking site is a hydroxy group, a carboxyl group, or an amino group.   The resist underlayer film forming composition according to any one of claims 1 to 4, further comprising a surfactant.   A step of applying the resist underlayer film forming composition according to any one of claims 1 to 5 on a semiconductor substrate and baking to form a resist underlayer film, and forming a resist film on the resist underlayer film A method for forming a resist pattern used for manufacturing a semiconductor device, comprising: a step of forming, a step of exposing a semiconductor substrate covered with the resist underlayer film and the resist film, and a step of developing after the exposure.