JP2012022191A - Composition for forming resist underlayer film including ionic polymer 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 including an ionic polymer in which the composition is capable of forming the resist underlayer having 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 includes an ionic polymer having structural units [a] and [b] expressed by the following formula (1), a crosslinking agent, a compound for promoting crosslinking reaction and an organic solvent.

Description

  The present invention relates to a resist underlayer film forming composition and a method of 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 polymer. 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, various resist underlayer film forming compositions have been reported conventionally.

As one of candidates for manufacturing a photolithography mask in a semiconductor process and next-generation advanced microfabrication technology, there is electron beam (EB) lithography. 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.

By the way, ionic liquid has properties such as flame retardancy, non-volatility, high polarity, high ionic conductivity, and high heat resistance, and is expected to be applied to various electrochemical devices. .
Therefore, an antistatic film forming composition for forming an antistatic film on the upper layer of the electron beam resist containing the ionic liquid has been proposed in order to use the ionic conductivity of this ionic liquid as an antistatic measure. (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. As another method of using the ion conductivity, an ionizing radiation curable composition for forming an antistatic film using a polymer in which a constituent unit of an ionic monomer is 20 to 100 mol% is also 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 an object of the present invention to provide a resist underlayer film forming composition capable of forming a resist pattern and a resist pattern forming method using a resist underlayer film formed from the composition.

As a result of intensive studies to achieve the above object, the present inventors have obtained an ionic polymer having structural units [a] and [b] represented by the following formula (1) as a resist underlayer film forming composition. It was found that the inclusion of the antistatic function was imparted to the resist underlayer film formed from the composition, and the present invention was completed.
That is, the present invention provides a resist underlayer film formation comprising an ionic polymer having structural units [a] and [b] represented by the following formula (1), a crosslinking agent, a compound for promoting a crosslinking reaction, and an organic solvent. It is a composition.
(Wherein R ₁ independently represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 3 to 12 carbon atoms, or — (CH ₂ CH ₂ O) _m (CH ₂ ) _n — (m is 1 To an integer of 1 to 7, n is an integer of 1 to 3, R ₃ represents a methyl group or an ethyl group, X ⁻ represents imide, halogen, carboxylate, sulfate, sulfonate, This represents an anion selected from the group consisting of thiocyanate, aluminate, borate, phosphate, phosphinate, amide, antimonate and methide, and A represents a group having a crosslinking site.

The present invention provides a resist underlayer film having an antistatic function capable of preventing electron beam scattering by including an ionic polymer represented by the above formula (1) in a resist underlayer film forming composition. can do.
In addition, the resist underlayer film forming composition of the present invention can form a resist underlayer film having excellent solvent resistance, and the amount of sublimate generated when the resist underlayer film is formed is represented by the above formula (1). The effect of being able to be suppressed to the same or less than the case where the ionic polymer represented is not included is acquired.
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.
In addition, the resist underlayer film forming composition of the present invention includes the ionic polymer represented by the above formula (1) and a polymer different from the ionic polymer, thereby preventing the antistatic function of the resist underlayer film. It is possible to improve solvent resistance and sublimation suppression.

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 3. 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 4. 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 Comparative Example 1. 6 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 1. FIG. FIG. 7 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 2. 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 3. FIG. 9 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 4.

  The resist underlayer film forming composition of the present invention includes an ionic polymer having the structural units [a] and [b] represented by the above formula (1), a crosslinking agent, a compound for promoting a crosslinking reaction, and an organic solvent. . 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 polymer>
The ionic polymer contained in the resist underlayer film forming composition of the present invention has structural units [a] and [b] represented by the following formula (1). By containing this ionic polymer, 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.
(Wherein R ₁ independently represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 3 to 12 carbon atoms, or — (CH ₂ CH ₂ O) _m (CH ₂ ) _n — (m is 1 To an integer of 1 to 7, n is an integer of 1 to 3, R ₃ represents a methyl group or an ethyl group, X ⁻ represents imide, halogen, carboxylate, sulfate, sulfonate, This represents an anion selected from the group consisting of thiocyanate, aluminate, borate, phosphate, phosphinate, amide, antimonate and methide, and A represents a group having a crosslinking site.

  The proportion of the structural units [a] and [b] in the ionic polymer is usually 10:90 to 80: 20% by mass, preferably 20:80 to 70: 30% by mass. This is because if the proportion of the structural unit having an ionic site represented by [a] is small, the resist underlayer film cannot be sufficiently provided with an antistatic function.

In the structural unit [a], R ² is an alkylene group having 3 to 12 carbon atoms or — (CH ₂ CH ₂ O) _m (CH ₂ ) _n — (m is an integer of 1 to 7, n is 1 to 3 The resist underlayer film formed from the resist underlayer film forming composition of the present invention can exhibit an antistatic function. From the viewpoint of antistatic properties, R ² is preferably an alkylene group having 6 to 8 carbon atoms.

Examples of X ⁻ which is an anion include (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ , Cl ⁻ , Br ⁻ , CH ₃ COO ⁻ , CF ₃ COO ⁻ , ^{_{CF 3 CF 2 CF 2 COO -}} , CF 3
_{^{SO 3 -, CF 3 CF 2}} CF 2 CF 2 SO 3 -, SbF 6 - and the like. Among them, (CF ₃ SO ₂ ) ₂ N ⁻ [bis (trifluoromethanesulfonyl) imide anion] is preferable because it has a low melting point and high heat resistance.

  The group having a crosslinking site refers to a group having a functional group capable of undergoing a crosslinking reaction. Examples of such functional groups include a hydroxy group, a carboxyl group, an amino group, an ester group, and a chlorosulfone group. , Epoxy group, isocyanate group, methylol group, sulfone group, or mercapto group. Preferably, they are a hydroxyl group, a carboxyl group, or an amino group.

The structural unit [b] is, for example, the following formula:
(Wherein R ¹ represents a hydrogen atom or a methyl group, and A ′ represents a linear or branched hydroxyalkyl group having 1 to 4 carbon atoms) [b-1] It can be.

In the ionic polymer, the structural unit [a] has an ionic site, and the structural unit [b] has a crosslinking site.
Examples of the monomer having an ionic site and the monomer having a crosslinking site necessary for obtaining the ionic polymer contained in the resist underlayer film forming composition of the present invention as described above include, for example, the following general formula (I) and (II) is mentioned.
(R ₁ , R ₂ , R ₃ , and A are each synonymous with the definition described in the above formula (1).)

  A method for synthesizing a monomer having an ionic moiety represented by the above general formula (I) is known, for example, as described in Hong Chen and Yosef A. Elabd, Macromolecules 2009, 42, 3368-3373.

  The method for synthesizing the ionic polymer contained in the resist underlayer film forming composition of the present invention is not particularly limited. For example, in an organic solvent, a monomer having an ionic moiety represented by the above formula (I) and It can be synthesized by adding a polymerization initiator to the monomer having a crosslinking site represented by the above formula (II) and performing heat polymerization.

  Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2′-azobis (2-methylpropio). Nate), benzoyl peroxide, and lauroyl peroxide, and can be polymerized by heating to 50 to 80 ° C. The reaction time is usually 2 to 100 hours, or 5 to 30 hours.

  Moreover, when synthesizing the ionic polymer, the charging ratio of the monomer having the ionic moiety represented by the formula (I) and the monomer having the crosslinking moiety represented by the formula (II) is usually 20 : 80-80: 20% by mass, preferably 30: 70-70: 30% by mass.

  Further, the resist underlayer film forming composition of the present invention includes, in addition to the ionic polymer, an acrylic resin, methacrylic resin, polyester, novolac resin, phenol resin, natural polymer, melamine resin different from the ionic polymer. Or a silicon resin or the like. From the viewpoint of solvent resistance and antistatic function of the resist underlayer film, acrylic resin, methacrylic resin, and polyester are preferable.

When the resist underlayer film forming composition of the present invention contains a polymer different from the ionic polymer, the content ratio of the ionic polymer to the polymer is usually 20:80 to 99: 1 mass%. This is because if the proportion of the ionic polymer is too small, the antistatic function cannot be sufficiently imparted to the resist underlayer film. On the other hand, the ratio of the ionic polymer may be 100% by mass, that is, the polymer different from the ionic polymer may not be included.

  The said ionic polymer is 1.0-90 mass% or 10-85 mass%, for example based on content in the component except the organic solvent of the resist underlayer film forming composition of this invention. This is because if this ratio is too small or too large, it may be difficult to obtain an antistatic function and solvent resistance.

<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 cross-linking agent, the cross-linking agent reacts with the ionic polymer or the ionic polymer and a polymer different from the ionic polymer, and the resist underlayer film formed by cross-linking becomes strong. 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.
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 -Tetrakis (methoxymethyl) urea.

  The amount of the crosslinking agent can be added to the ionic polymer contained in the resist underlayer film forming composition of the present invention, for example, at a ratio of 1% by mass to 35% 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 of an ionic polymer and a crosslinking agent or a polymer different from the ionic polymer and the ionic polymer and a crosslinking agent, such as a sulfonic acid compound. It is done.
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 that promotes the crosslinking reaction can be added to the ionic polymer contained in the resist underlayer film forming composition of the present invention at a ratio of, for example, 0.1% by mass or more and 10% by mass or less. . This is because when this ratio is too small, the crosslinking reaction cannot be sufficiently promoted.

<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, and N-methylpyrrolidone 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, 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 covered with a silicon oxide film, a semiconductor substrate such as silicon covered 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, post-exposure bake is performed as necessary. 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 was measured using a film thickness measuring device NanoSpec / AFT5100 (manufactured by Nanometrics).

<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 (2) 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 (3) 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>
[Synthesis of ionic monomers]
19.66 g of 6-bromo-1-hexanol (manufactured by Tokyo Chemical Industry Co., Ltd.) and 10.09 g of triethylamine (manufactured by Kanto Chemical Co., Ltd.) are added to 66.33 g of dichloromethane (dehydrated) (manufactured by Kanto Chemical Co., Ltd.). A solution prepared by dissolving 10.45 g of methacryloyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) in 13.27 g of dichloromethane (dehydrated) was added dropwise to the solution while cooling and allowed to react overnight. Wash the reaction solution several times with pure water, evaporate the solvent, magnesium sulfate (anhydrous)
5 g was added to dehydrate the reaction product represented by Formula A above.
Next, 0.1 g of 2,6-di-tert-butyl-p-cresol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as a polymerization inhibitor to 18.69 g of the reaction product represented by the above formula A. -While reacting 7.21 g of ethylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) dropwise, the reaction was carried out for 24 hours using an oil bath at 40C. The obtained reaction solution was washed several times with diethyl ether, and the solvent was evaporated to obtain the desired monomer represented by the above formula B. The yield was about 62%.
Next, 21.33 g of the monomer represented by the above formula B was dissolved in 50 g of pure water, and 17.73 g of bis (trifluoromethanesulfonylimide) lithium (manufactured by Tokyo Chemical Industry Co., Ltd.) was added while cooling and reacted for 24 hours. I let you. The obtained reaction product was washed several times with pure water, dissolved in dichloromethane (dehydration), and the solvent was evaporated to obtain 28.92 g of the compound represented by the above formula C as the final target product. The yield was about 85%.

[Synthesis of ionic polymer]
After adding 6.00 g of the compound represented by Formula C above, 14.00 g of 2-hydroxypropyl methacrylate (Tokyo Chemical Industry Co., Ltd.) and 10 g of ethyl lactate (EL) represented by Formula D above. The inside of the flask was replaced with nitrogen, and the temperature was raised to 70 ° C. As a polymerization initiator, 0.20 g of azobisisobutyronitrile (AIBN) dissolved in 19.8 g of ethyl lactate is added under nitrogen pressure and reacted for 24 hours to contain the ionic polymer represented by the above formula E The product was obtained (X = 30% by weight). In order to remove unreacted substances from the resulting product, reprecipitation was performed using diethyl ether, and the solvent was dried to obtain 20.07 g of an ionic polymer represented by the above formula E. The obtained ionic polymer represented by the above formula E was dissolved again in ethyl lactate to obtain a solution of the ionic polymer. The viscosity of the obtained solution was 5.54 mPa · s (manufactured by Toki Sangyo Co., Ltd., VISCOMETER TV20).

<Example 1>
To 0.91 g of a solution containing 0.17 g of the polymer obtained in Synthesis Example 1 and 3.00 g of a solution containing 0.51 g of the ionic polymer obtained in Synthesis Example 3, pyridinium-p-toluenesulfonate ( 0.0053 g of Tokyo Chemical Industry Co., Ltd.) and 0.1696 g of tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, manufactured by Nihon Cytec Industries Co., Ltd.) are mixed and 8.11 g of propylene glycol monomethyl ether And 16.99 g of ethyl lactate 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 0.92 g of a solution containing 0.17 g of the polymer obtained in Synthesis Example 2 and 3.00 g of a solution containing 0.51 g of the ionic polymer obtained in Synthesis Example 3, pyridinium-p-toluenesulfonate ( 0.0053 g of Tokyo Chemical Industry Co., Ltd.) and 0.17 g of tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, manufactured by Nihon Cytec Industries Co., Ltd.) are mixed and 8.11 g of propylene glycol monomethyl ether And 16.99 g of ethyl lactate 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>
0.54 g (polymer concentration 21 mass%) containing a polymer having a structure represented by the following formula (4) (weight average molecular weight 10,000 in terms of polystyrene) and the ionic weight obtained in Synthesis Example 3 To 2.00 g of a solution containing 0.34 g of a compound, 0.0035 g of pyridinium-p-toluenesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.) and tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, Nippon Cytec 0.11 g of Industries, Ltd.) was mixed, and 5.40 g of propylene glycol monomethyl ether and 11.33 g of ethyl lactate were added to obtain 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.

<Example 4>
To 2.00 g of a solution containing 0.34 g of the ionic polymer obtained in Synthesis Example 3, 0.017 g of 5-sulfosalicylic acid and tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, Nippon Cytec Industries, Ltd. 0.08 g) was mixed, and 15.55 g of ethyl lactate was 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 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 and tetramethoxymethyl glycoluril (trade name: POWDERLINK [registered trademark] 1174, 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 and tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, 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 a solution containing a polymer having a structure represented by the following formula (4 ′) (weight average molecular weight of 60,000 in terms of polystyrene) (polymer concentration 15 mass%), pyridinium-
0.012 g of p-toluenesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.024 g of bisphenol S (manufactured by Tokyo Chemical Industry Co., Ltd.) and tetramethoxymethylglycoluril (trade name: POWDERLINK [registered trademark] 1174, Japan Cytec Industries Co., Ltd.) 0.19 g, propylene glycol monomethyl ether 12.67 g, and propylene glycol monomethyl ether acetate 7.17 g were added to obtain 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 for lithography prepared in Examples 1 to 4 and Comparative Examples 1 and 2 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 4 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.

[Measurement of sublimation amount]
To a silicon wafer having a diameter of 4 inches, the resist underlayer film forming composition prepared in Examples 1 to 4 and the resist underlayer film forming composition prepared in Comparative Example 3 as a comparative object were applied at 1,500 rpm using a spin coater. Each was applied for 60 seconds. The silicon wafer coated with the resist underlayer film forming composition is set in a sublimation amount measuring apparatus (see International Publication No. 2007/111147 pamphlet) in which a hot plate is integrated, and baked for 120 seconds. The quartz crystal was collected on a quartz crystal microbalance sensor. 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 silicon wafer coated with the resist underlayer film forming composition was quickly placed on the hot plate from the slide port, and the sublimate was collected from 60 seconds to 180 seconds (120 seconds). The initial film thickness of the resist underlayer film formed on the silicon 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 grams from the eigenvalue of the quartz crystal used for the measurement, and the relationship between the amount of sublimation of one silicon wafer coated with the resist underlayer film forming composition and the passage of time was clarified. Table 2 shows the amount of sublimation (unit: ng: nanogram) indicated by the measuring apparatus from 0 to 180 seconds in Examples 1 to 4 and Comparative Example 3 to be compared. Note that the first 60 seconds is a time zone in which the device is left to stabilize (the silicon wafer is not set), and the amount of sublimation indicated by the measuring device is a negative value in order to indicate the stable state of the measuring device. I read it as it was. Therefore, the measurement value from the time point of 60 seconds when the silicon wafer is placed on the hot plate to the time point of 180 seconds is a measurement value related to the amount of sublimation of the silicon wafer.

  From the results of Table 2, the resist underlayer film formed from the resist underlayer film forming composition of Examples 1 to 4 of the present invention is more than the resist underlayer film formed from the resist underlayer film forming composition of Comparative Example 3. It is clear that the generation of sublimates is suppressed.

[Surface resistance measurement]
Antistatic performance is closely related to the surface resistance value of the film. Generally, the lower the surface resistance value,
It is known that it has excellent 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 to 4 and Comparative Examples 1 and 2 were spin-coated on a silicon 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 DKK Corporation). As shown in Table 3, the resist underlayer film formed from the resist underlayer film forming composition containing the ionic polymer obtained in the Examples has a resistance value as compared with that of the comparative example not containing the ionic polymer. It was confirmed that it was 1 order or more lower.

[Antistatic performance test]
The resist underlayer film forming compositions obtained in Examples 1 to 4 and Comparative Example 1 were each spin-coated on a silicon wafer. A resist underlayer film was formed by baking at 205 ° C. for 60 seconds. A silicon wafer was cut into a 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 containing the ionic polymer obtained in the examples, the image contrast after enlargement and reduction is sufficiently smaller than that of the comparative example not containing the ionic polymer, and the antistatic performance is low. 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. Cross-sectional SEM images when the resist underlayer film forming compositions obtained in Examples 1 to 4 and Comparative Example 1 are used are shown in FIGS.

[Formation of resist pattern]
The resist underlayer film forming compositions prepared in Examples 1 to 4 and Comparative Example 1 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 photoresist 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 photoresist film (film). A thickness of 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, a 0.26N tetramethylammonium hydroxide aqueous solution is used as a developer in an industrial standard 60 second single paddle process. Developed. 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. Cross-sectional SEM images of resist patterns formed using the resist underlayer film forming compositions prepared in Examples 1 to 4 are shown in FIGS.

Claims (8)

Following formula (1):
(Wherein R ₁ independently represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 3 to 12 carbon atoms, or — (CH ₂ CH ₂ O) _m (CH ₂ ) _n — (m is 1 To an integer of 1 to 7, n is an integer of 1 to 3, R ₃ represents a methyl group or an ethyl group, X ⁻ represents imide, halogen, carboxylate, sulfate, sulfonate, This represents an anion selected from the group consisting of thiocyanate, aluminate, borate, phosphate, phosphinate, amide, antimonate and methide, and A represents a group having a crosslinking site.
A resist underlayer film-forming composition comprising: an ionic polymer having structural units [a] and [b] represented by formula:   The resist underlayer film forming composition according to claim 1, wherein a ratio of the structural units [a] and [b] in the ionic polymer is 10:90 to 80: 20% by mass.   The resist underlayer film forming composition according to claim 1, wherein the crosslinking site is a hydroxy group, a carboxyl group, or an amino group. The structural unit [b] is represented by the following formula:
(Wherein R ₁ has the same meaning as in claim 1, and A ′ represents a linear or branched hydroxyalkyl group having 1 to 4 carbon atoms) [b-1] The resist underlayer film forming composition according to any one of claims 1 to 3, wherein The resist underlayer film forming composition according to claim 1, wherein the X ⁻ is a bis (trifluoromethanesulfonyl) imide anion.   Furthermore, the resist underlayer film forming composition as described in any one of Claims 1 thru | or 5 containing the acrylic resin, methacrylic resin, or polyester different from the said ionic polymer.   Furthermore, the resist underlayer film forming composition as described in any one of Claims 1 thru | or 6 containing surfactant.   A step of applying the resist underlayer film forming composition according to any one of claims 1 to 7 on a semiconductor substrate and baking to form a resist underlayer film, and forming a resist film on the resist underlayer film A method of forming a resist pattern used for manufacturing a semiconductor device, comprising: 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.