JPWO2012081619A1 - Resist underlayer film forming composition and resist pattern forming method using the same - Google Patents

Abstract

An object of the present invention is to obtain a composition for forming a resist underlayer film useful for reducing LER. Another object of the present invention is to obtain a composition for forming a resist underlayer film in which a resist pattern on the resist underlayer film has a desired shape. A resist underlayer film forming composition for lithography comprising a polymer having a structural unit represented by the following formulas (1) and (2), a crosslinking agent and a solvent. Wherein R 1 and R 2 each independently represent a hydrogen atom or a methyl group, and L 1 is a single bond or a divalent having a linear or branched alkylene group having 1 to 13 carbon atoms. A represents an aromatic ring group having at least one substituent containing a hydroxy group, and D represents a linear or branched hydroxyalkyl group having 1 to 13 carbon atoms.) Selection diagram] None

Description

  The present invention relates to a resist underlayer film forming composition for lithography useful for forming a resist pattern having a desired shape, and a resist pattern forming method using the resist underlayer film forming composition. More specifically, the present invention relates to a resist underlayer film forming composition that reduces the roughness of the pattern sidewall of a resist pattern in a lithography process for manufacturing a semiconductor device.

  Conventionally, in the manufacture of semiconductor devices, fine processing by lithography using a resist composition has been performed. The microfabrication forms a thin film of a photoresist composition on a semiconductor substrate such as a silicon wafer, and irradiates with an actinic ray such as ultraviolet rays through a mask pattern on which a device pattern is drawn, and develops it. This is a processing method for forming fine irregularities corresponding to the pattern on the substrate surface by etching the substrate using the obtained photoresist pattern as a protective film. In recent years, semiconductor devices have been highly integrated, and actinic rays used have been shortened from i-line (wavelength 365 nm) and KrF excimer laser (wavelength 248 nm) to ArF excimer laser (wavelength 193 nm). Along with this, the influence of diffuse reflection of active rays from the semiconductor substrate and standing waves has become a major problem. In order to solve this problem, a method of providing an antireflection film (Bottom Anti-Reflective Coating: BARC) between a resist and a semiconductor substrate has been widely studied. The antireflection film is also referred to as a resist underlayer film. As such an antireflection film, many studies have been made on an organic antireflection film made of a polymer having a light-absorbing group or the like because of its ease of use (for example, Patent Document 1).

  On the other hand, lithography using EUV (extreme ultraviolet abbreviation, wavelength: 13.5 nm) exposure, which is a further fine processing technique, does not reflect exposure light from the substrate, but there is a problem with the roughness of the resist pattern side wall as the pattern becomes finer. Therefore, many studies have been made on a resist underlayer film for forming a highly rectangular resist pattern shape. As a material for forming a resist underlayer film for exposure to high energy rays such as EUV and electron beam, a resist underlayer film forming composition with reduced outgas generation is disclosed (Patent Document 2). However, the patent document 2 neither describes nor suggests the problem of the roughness of the pattern side wall. Similarly, the above-mentioned Patent Document 1 has neither description nor suggestion.

JP 2000-187331 A International Publication No. 2010/061774

  The above-mentioned characteristics required for the resist underlayer film include, for example, that no intermixing with the resist occurs (insoluble in the resist solvent), and the upper layer from the resist underlayer film at the time of coating or subsequent baking. For example, the diffusion of a low-molecular substance into the resist does not occur, a resist pattern having a shape without tailing can be formed, the adhesiveness with the resist is excellent, and the dry etching rate is higher than that of the resist. Further, there is an increasing demand for characteristics that a wide focus depth margin can be obtained and characteristics that a high resolution can be achieved. The focus depth margin is the width of the entire depth region that can maintain the resist pattern in a practical state when the focus is shifted upward or downward with respect to the optimum focus position during exposure. That is, the extension of the focus depth margin contributes to increasing the margin in the manufacturing process.

  In the case of lithography with EUV exposure, the pattern line width to be formed is 32 nm or less, and the demand for line edge roughness (hereinafter abbreviated as LER in this specification) of the pattern sidewall becomes severe. When the formed resist pattern shape is a skirt shape or a shape in which adjacent patterns are connected without being separated, the value of LER when observed from above the pattern becomes large, which adversely affects dimensional control. For this reason, it is strongly required to make the resist pattern shape a rectangular shape having a small LER value. Further, in the case of a resist underlayer film for EUV exposure, a thin film having a film thickness of 20 nm or less is often used.

  The present invention provides a resist underlayer film that has high adhesiveness to a resist film, can form a good (rectangular shape) resist pattern even when the resist underlayer film is thin, and is useful for reducing LER. The object is to obtain a composition for forming. Another object of the present invention is to obtain a composition for forming a resist underlayer film in which a resist pattern on the resist underlayer film has a desired shape. In the composition of the present invention, the resist underlayer film to be formed is insoluble in the solvent of the resist applied thereon, and no intermixing occurs between the resist underlayer film to be formed and the resist film. It is a condition.

（式中、Ｒ₁及びＲ₂はそれぞれ独立に水素原子又はメチル基を表し、Ｌ₁は単結合、又は直鎖状若しくは分岐鎖状の炭素原子数１乃至１３のアルキレン基を有する２価の連結基を表し、Ａはヒドロキシ基を含む少なくとも一つの置換基を有する芳香環基を表し、Ｄは直鎖状又は分岐鎖状の炭素原子数１乃至１３のヒドロキシアルキル基を表す。）The first aspect of the present invention is:
The present invention relates to a resist underlayer film forming composition for lithography comprising a polymer having a structural unit represented by the following formulas (1) and (2), a crosslinking agent and a solvent.

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a methyl group, and L ₁ is a divalent divalent alkylene group having a single bond or a linear or branched alkylene group having 1 to 13 carbon atoms. Represents a linking group, A represents an aromatic ring group having at least one substituent containing a hydroxy group, and D represents a linear or branched hydroxyalkyl group having 1 to 13 carbon atoms.

  The repeating number of the structural unit represented by the formula (1) and the formula (2) in the polymer is, for example, in the range of 10 to 10,000.

（式中、Ｒ₃は水素原子又はメチル基を表し、Ｌ₂は単結合又は直鎖状若しくは分岐鎖状の炭素原子数１乃至１３のアルキレン基を表し、Ｅはラクトン環を含む基又はアダマンタン環を含む基を表す。）In addition to the structural units represented by the above formulas (1) and (2), the polymer may be a copolymer further having a structural unit represented by the following formula (3).

Wherein R ₃ represents a hydrogen atom or a methyl group, L ₂ represents a single bond or a linear or branched alkylene group having 1 to 13 carbon atoms, and E represents a group containing a lactone ring or adamantane Represents a group containing a ring.)

When L _{1 in} formula (1) represents a single bond, this means that the aromatic ring group represented by A directly binds to an oxygen atom, and when L _{2 in} formula (3) represents a single bond, It means that a group containing a lactone ring or a group containing an adamantane ring is directly bonded to an oxygen atom. The lactone ring and adamantane ring may have a substituent or may be unsubstituted. The lactone ring may constitute a part of a bicyclo ring or a polycycle (for example, a tricyclo ring) or may be bonded to another ring. Further, the divalent linking group is not limited to a linear or branched alkylene group having 1 to 13 carbon atoms, and for example, the alkylene group and a —C (═O) —O— group, —O. It may be a combination with a —C (═O) — group or —O— group, and the alkylene group may have a hydroxy group as a substituent.

  The second aspect of the present invention is a step of applying a resist underlayer film forming composition for lithography of the present invention on a semiconductor substrate and baking to form a resist underlayer film, and a step of forming a resist film on the resist underlayer film The present invention relates to a method for forming a resist pattern, comprising: exposing a semiconductor substrate coated with the resist underlayer film and the resist film; and developing the resist film with a developer after the exposure. The exposure is performed using, for example, extreme ultraviolet (EUV), but is not limited to EUV, and a KrF excimer laser, an ArF excimer laser, or an electron beam can also be used.

  The resist underlayer film forming composition for lithography of the present invention incorporates an aromatic ring group having a hydroxy group as a substituent (for example, a hydroxyphenyl group) at the side chain end of the polymer contained in the resist underlayer film forming composition. It is a composition containing such a polymer, a crosslinking agent and a solvent. With such a configuration, the resist underlayer film has excellent adhesion with the resist film provided on the upper layer, and a good resist pattern without pattern peeling or pattern disappearance can be formed.

  Moreover, the resist underlayer film forming composition for lithography of the present invention provides a resist underlayer film that has a good shape with almost no bottoming shape at the bottom and can form a resist pattern with excellent dimensional controllability on the upper layer. be able to.

  Furthermore, the resist underlayer film formed from the composition for forming a resist underlayer film for lithography of the present invention can produce a resist pattern having high sensitivity, high resolution and low LER with respect to high energy rays, particularly EUV.

[polymer]
The polymer contained in the resist underlayer film forming composition for lithography of the present invention contains the structural units represented by the above formulas (1) and (2) as essential structural units.

  The structural unit represented by the formula (1) is a light absorption site for adjusting optical parameters (n value (refractive index) and k value (attenuation coefficient or extinction coefficient)) of the resist underlayer film to be formed, Resist pattern shape without tailing by the hydroxy group which is a part of the aromatic ring group represented by A in the formula, which acts as an acidic unit. It is also a part that produces the effect of obtaining. The structural unit represented by the formula (2) is a site that reacts with a crosslinking agent to form a resist underlayer film having solvent resistance.

  Examples of the aromatic ring in the aromatic ring group include a benzene ring, a naphthalene ring, and an anthracene ring.

  Examples of the monomer forming the structural unit represented by the formula (1) include p-hydroxyphenyl (meth) acrylate and p-hydroxybenzyl (meth) acrylate.

  Examples of the monomer that forms the structural unit represented by the formula (2) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, which are monomers having at least one hydroxy group, 4 -Hydroxybutyl (meth) acrylate and 2,3-dihydroxypropyl (meth) acrylate can be mentioned.

上記式中、Ｒ^aは水素原子又はメチル基を表し、Ｒ^bはそれぞれ独立して水素原子又は直鎖状又は分岐鎖状の炭素原子数１乃至５のアルキル基を表し、Ｒ^cは直鎖状又は分岐鎖状の炭素原子数１乃至５のアルキル基を表し、Ｒ^dはそれぞれ独立して直鎖状又は分岐鎖状の炭素原子数１乃至５のアルキル基を表す。Of the monomers forming the structural unit represented by the formula (3), preferred examples include compounds represented by the following structural formula.

In the above formula, R ^a represents a hydrogen atom or a methyl group, R ^b each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms, and R ^c represents a straight chain. Represents a linear or branched alkyl group having 1 to 5 carbon atoms, and each R ^d independently represents a linear or branched alkyl group having 1 to 5 carbon atoms.

More specifically, for example, monomers having a group containing a lactone ring or a group containing an adamantane ring shown below can be exemplified.

The polymer used in the resist underlayer film forming composition of the present invention is particularly preferably a copolymer containing structural units represented by the following formula (1-1), formula (2-1) and formula (3-1). is there.

  When the total of the structural units represented by the formula (1), the formula (2), and the formula (3) as necessary in the polymer used in the resist underlayer film forming composition for lithography of the present invention is 100% by mass. The proportion of the structural unit represented by the formula (1) is 1% by mass to 80% by mass (in terms of monomer charge ratio), preferably 5% by mass to 50% by mass, and more preferably 20% by mass to 40% by mass. %. Further, the proportion of the structural unit represented by the formula (2) is 1% by mass to 80% by mass (in terms of monomer charge ratio), preferably 5% by mass to 50% by mass, more preferably 20% by mass to 40%. % By mass. The proportion of the structural unit represented by the formula (3) is 1% by mass to 60% by mass (in terms of monomer charge ratio), preferably 5% by mass to 50% by mass, more preferably 20% by mass to 40% by mass. It is.

  The polymer used for the resist underlayer film forming composition for lithography of the present invention may be any of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer. The resin forming the resist underlayer film of the present invention can be synthesized by a method such as radical polymerization, anionic polymerization, or cationic polymerization. As the polymerization method, various methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization are possible, and a polymerization catalyst or the like may be appropriately used.

  As an example of the polymerization method, in an organic solvent, a polymerization initiator is added to the monomer that forms the structural unit represented by the above formula (1), formula (2), and formula (3) as necessary. It can be synthesized by heat polymerization. The organic solvent used here can be suitably selected from preferable examples as a solvent contained in the resist underlayer film forming composition for lithography of the present invention described later. 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 the heating temperature is usually 50 ° C to 80 ° C. The reaction time is usually 2 hours to 100 hours, or 5 hours to 30 hours.

  The ratio of the polymer in the resist underlayer film forming composition for lithography of the present invention can be, for example, 0.5 to 30% by mass with respect to the resist underlayer film forming composition. Moreover, when the component remove | excluding the solvent mentioned later from the said resist underlayer film forming composition is defined as solid content, the solid content contains the polymer and a crosslinking agent and the additive mentioned later added as needed. The ratio of the polymer in solid content is 70 mass%-98 mass%, for example.

[Crosslinking agent]
The resist underlayer film forming composition for lithography of the present invention further contains a crosslinking agent. Although there is no restriction | limiting in particular as the crosslinking agent, The crosslinkable compound which has at least 2 crosslink formation substituent is used preferably. Examples of the cross-linking agent include melamine compounds having a cross-linking substituent such as a methylol group and a methoxymethyl group, substituted urea compounds, and polymer compounds containing an epoxy group. Preferably, it is a nitrogen-containing compound having 2 to 4 nitrogen atoms substituted with a methylol group or an alkoxymethyl group.

  The content of the cross-linking agent in the resist underlayer film forming composition for lithography of the present invention defines a component obtained by removing the solvent described later from the resist underlayer film forming composition as a solid content (that is, the solid content is a polymer and a crosslinkage). Based on the solid content of the resist underlayer film forming composition, or 8% by weight based on the solid content of the resist underlayer film forming composition. % To 40% by mass, or 15% to 30% by mass.

  Although the crosslinking agent may cause a crosslinking reaction by self-condensation, the polymer, particularly a structural unit derived from a (meth) acrylate compound having a hydroxy group, which is a structural unit that reacts with the crosslinking agent to form a crosslinking. It is possible to cause a crosslinking reaction with a crosslinking functional group (hydroxy group) therein.

  In order to promote the crosslinking reaction, the resist underlayer film forming composition for lithography of the present invention can further contain a crosslinking catalyst. Examples of such a crosslinking catalyst include p-toluenesulfonic acid, trifluoromethanesulfonic acid, pyridinium-p-toluenesulfonate, salicylic acid, camphorsulfonic acid, 5-sulfosalicylic acid, 4-chlorobenzenesulfonic acid, 4-hydroxybenzene. Examples thereof include sulfonic acid compounds such as sulfonic acid, benzenedisulfonic acid, 1-naphthalenesulfonic acid, citric acid, benzoic acid, and hydroxybenzoic acid, and carboxylic acid compounds. These crosslinking catalysts can be used alone or in combination of two or more. When a crosslinking catalyst is used, the content of the crosslinking catalyst in the resist underlayer film forming composition for lithography of the present invention is 0.01% by mass based on the solid content of the resist underlayer film forming composition. It is 10 mass%, or 0.1 mass%-8 mass%, or 0.5 mass%-5 mass%.

[solvent]
The resist underlayer film forming composition for lithography of the present invention further contains a solvent. The solvent used in the present invention is not particularly limited as long as it can dissolve the aforementioned polymer. 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 monopropyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, γ-butyrolactone, N-methyl- 2-pyrrolidone, 2-hydroxypropionic acid ester , Ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid Ethyl, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate can be used. These organic solvents are used alone or in combination of two or more.

  Furthermore, high boiling point solvents such as propylene glycol monobutyl ether and propylene glycol monobutyl ether acetate can be mixed and used.

  Of the above solvents, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl lactate, butyl lactate, and cyclohexanone are preferred. And the ratio of the said solvent contained in the resist underlayer film forming composition for lithography of this invention is 50 mass%-99.5 mass% of the said resist underlayer film forming composition, for example.

[Other additives]
The composition for forming a resist underlayer film for lithography of the present invention may further contain various additives such as a surfactant, an adhesion aid, and a rheology adjuster as necessary as long as the effects of the present invention are not impaired.

  The surfactant is an additive for improving the applicability of the resist underlayer film forming composition to the substrate. Known surfactants such as nonionic surfactants and fluorine-based surfactants can be used.

  Specific examples of the surfactant include, for example, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene alkyl ethers such as polyoxyethylene oleyl ether, and polyoxyethylene octylphenyl ether. , Polyoxyethylene alkylaryl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene / polyoxypropylene block copolymers, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate Sorbitan fatty acid esters such as sorbitan tristearate, polyoxyethylene sorbitan monolaurate, polyoxy Nonionic surfactants such as polyoxyethylene sorbitan fatty acid esters such as tylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, Ftop [registered trademark] EF301, EF303, EF352 (Mitsubishi Materials Electronics Kasei Co., Ltd. (formerly Gemco)), MegaFuck [registered trademark] F171, F173, R30 (DIC Corporation), Florard FC430, FC431 (manufactured by Sumitomo 3M), Asahi Guard (registered trademark) AG710, Surflon (registered trademark) S-382, SC101, SC102, SC103, SC104, SC105, SC106 (Asahi Glass Co., Ltd.) Made) Fluorosurfactants, may be mentioned organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co.). These surfactants may be added alone or in combination of two or more.

  When the surfactant is used, the content of the surfactant in the resist underlayer film forming composition for lithography of the present invention is, for example, 3% by mass or less of the solid content of the resist underlayer film forming composition. Preferably it is 1 mass% or less, More preferably, it is 0.5 mass% or less.

  Next, the resist pattern forming method of the present invention will be described. First, a substrate used for manufacturing a precision integrated circuit element (for example, a semiconductor substrate such as a silicon wafer coated with a silicon oxide film, a silicon nitride film or a silicon oxynitride film, a silicon nitride substrate, a quartz substrate, a glass substrate (no (Including alkali glass, low alkali glass, crystallized glass), glass substrate on which an ITO film is formed) by applying a resist underlayer film forming composition for lithography of the present invention on a glass substrate on which an ITO film is formed by an appropriate coating method such as a spinner or coater, Thereafter, the resist underlayer film is produced by baking and curing using a heating means such as a hot plate.

  The conditions for baking after coating are appropriately selected from the range of, for example, a baking temperature of 80 ° C. to 250 ° C. and a baking time of 0.3 minutes to 60 minutes, preferably 150 ° C. to 250 ° C., 0.5 minutes to 5 minutes, for example. For minutes. By baking under such conditions, a crosslinking structure such as a hydroxyl group in the structural unit of the polymer reacts with a crosslinking agent to form a crosslinked structure. In particular, the crosslinking density of the crosslinked polymer can be increased by crosslinking the polymer contained in the resist underlayer film forming composition for lithography of the present invention. Moreover, as a film thickness of a resist underlayer film, it is 0.001 micrometer-3.0 micrometers, for example, Preferably it is 0.002 micrometer-1.0 micrometer, More preferably, it is 0.003 micrometer-0.5 micrometer.

  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.

  As the resist applied to the upper layer of the resist underlayer film obtained from the resist underlayer film forming composition for lithography of the present invention, for example, as long as it is sensitive to KrF excimer laser, ArF excimer laser, EUV, electron beam, etc. There is no particular limitation, and either a negative type or a positive type can be used. Examples of the resist include a positive resist containing a novolak resin and 1,2-naphthoquinonediazide sulfonic acid ester, a binder having a group that decomposes with an acid to increase the alkali dissolution rate, and a photoacid generator Chemically amplified resist that decomposes with acid to increase the alkali dissolution rate of the resist Chemically amplified resist that contains a low molecular weight compound, an alkali-soluble binder, and a photoacid generator, decomposes with acid to increase the alkali dissolution rate A chemically amplified resist containing a low-molecular compound and a photoacid generator that decomposes with a binder having an acid group and an acid to increase the alkali dissolution rate of the resist, and a group that decomposes with an electron beam to change the alkali dissolution rate. Non-chemically amplified resist containing a binder having a binder cut by an electron beam There are non-chemically amplified resist containing a binder having a site changing the potassium dissolution rate.

  Specifically, Sumitomo Chemical Co., Ltd., trade name PAR710, PAR855; JSR Corporation, trade name AR2772JN; Shin-Etsu Chemical Co., Ltd., trade name SEPR430; Dow Chemical Company (formerly Rohm and Product name APEX-X, manufactured by Hearth Electronic Materials). In addition, Proc. SPIE, Vol. 3999, 330-334 (2000), Proc. SPIE, Vol. 3999, 357-364 (2000), and Proc. SPIE, Vol. 3999, 365-374 (2000) can also be mentioned.

  Subsequently, the resist film formed on the upper layer of the resist lower layer film is exposed through a predetermined mask (reticle). For the exposure, for example, a KrF excimer laser, an ArF excimer laser, or EUV can be used. However, in the case of electron beam exposure, a mask (reticle) is not required. Moreover, after exposure, post-exposure heating (PEB: Post Exposure Bake) can be performed as necessary. The conditions for the post-exposure heating are appropriately selected from the range of a heating temperature of 80 ° C. to 150 ° C. and a heating time of 0.3 minutes to 60 minutes.

  After the exposure, the resist film is developed, rinsed and dried to obtain a good resist pattern.

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

  The development conditions are appropriately selected from a development temperature range of 5 ° C. to 50 ° C. and a development time of 10 seconds to 300 seconds.

  Then, a portion of the resist underlayer film exposed by developing and removing the resist film by the above process is removed by dry etching, and a desired pattern can be formed on the substrate.

  EXAMPLES Hereinafter, although a synthesis example and an Example are given and explained in full detail about this invention, this invention is not limited to the following description at all.

The weight average molecular weights shown in the following Synthesis Examples 1 to 4 are based on measurement results by gel permeation chromatography (hereinafter abbreviated as GPC in this specification). For measurement, a GPC device manufactured by Tosoh Corporation was used, and the measurement conditions were as follows.
GPC column: Shodex (registered trademark) and Asahipak (registered trademark) (Showa Denko KK)
Column temperature: 40 ° C
Solvent: N, N-dimethylformamide (DMF)
Flow rate: 0.6 ml / min Standard sample: Polystyrene (Tosoh Corporation)
Detector: RI

<Synthesis Example 1: PQMA / HPMA / GBLMA = 34/33/33 (mass%)>
2.72 g of p-hydroxyphenyl methacrylate (abbreviated as PQMA, manufactured by Showa Polymer Co., Ltd.), 2.64 g of 2-hydroxypropyl methacrylate (abbreviated as HPMA, manufactured by Tokyo Chemical Industry Co., Ltd.) and γ-butyrolactone methacrylate (abbreviated as GBLMA) 2.64 g of Osaka Organic Chemical Industry Co., Ltd.) was dissolved in 22.64 g of ethyl lactate and polymerized by radical polymerization. After the reaction, it was cooled to obtain a polymer solution having a solid content of 20% by mass. When the GPC analysis of the polymer in the obtained solution was performed, it was weight average molecular weight 14,400 in standard polystyrene conversion.

<Synthesis Example 2: PQMA / HPMA / GBLMA = 20/47/33 (mass%)>
1.60 g of p-hydroxyphenyl methacrylate (abbreviated as PQMA, Showa Polymer Co., Ltd.), 3.76 g of 2-hydroxypropyl methacrylate (abbreviated as HPMA, manufactured by Tokyo Chemical Industry Co., Ltd.) and γ-butyrolactone methacrylate (abbreviated as GBLMA) 2.64 g of Osaka Organic Chemical Industry Co., Ltd.) was dissolved in 22.64 g of ethyl lactate and polymerized by radical polymerization. After the reaction, it was cooled to obtain a polymer solution having a solid content of 20% by mass. When the GPC analysis of the polymer in the obtained solution was performed, it was the weight average molecular weight 14,700 in standard polystyrene conversion.

<Synthesis Example 3: PQMA / HPMA / GBLMA = 50/17/33 (mass%)>
p-Hydroxyphenyl methacrylate (abbreviated as PQMA, manufactured by Showa Polymer Co., Ltd.) 4.00 g, 2-hydroxypropyl methacrylate (abbreviated as HPMA, manufactured by Tokyo Chemical Industry Co., Ltd.) 1.36 g and γ-butyrolactone methacrylate (abbreviated as GBLMA) 2.64 g of Osaka Organic Chemical Industry Co., Ltd.) was dissolved in 22.64 g of ethyl lactate and polymerized by radical polymerization. After the reaction, it was cooled to obtain a polymer solution having a solid content of 20% by mass. When the GPC analysis of the polymer in the obtained solution was performed, it was the weight average molecular weight 15,100 in standard polystyrene conversion.

<Synthesis Example 4: PQMA / HPMA / OTDMA = 34/33/33 (mass%)>
2.72 g of p-hydroxyphenyl methacrylate (abbreviated as PQMA, manufactured by Showa Polymer Co., Ltd.), 2.64 g of 2-hydroxypropyl methacrylate (abbreviated as HPMA, manufactured by Tokyo Chemical Industry Co., Ltd.) and 8- or 9-methacryloyloxy 2.64 g of -4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one (abbreviated as OTDMA, manufactured by Mitsubishi Rayon Co., Ltd.) was dissolved in 22.64 g of ethyl lactate and subjected to radical polymerization. Polymerized. After the reaction, it was cooled to obtain a polymer solution having a solid content of 20% by mass. When the GPC analysis of the polymer in the obtained solution was performed, it was weight average molecular weight 14,800 in standard polystyrene conversion.

<Example 1>
To 5 g of the solution containing 1 g of the polymer obtained in Synthesis Example 1, 0.25 g of tetramethoxymethyl glycoluril (Nippon Cytec Industries, Ltd., trade name: POWDERLINK [registered trademark] 1174) and pyridinium-p-toluenesulfonate 0 0.0156 g was mixed, and this mixture was dissolved in 20.43 g of ethyl lactate and 10.47 g of propylene glycol monomethyl ether acetate to obtain a solution. Then, it filtered using the polyethylene micro filter with the hole diameter of 0.10 micrometer, and also filtered using the polyethylene micro filter with the hole diameter of 0.05 micrometer, and prepared the resist underlayer film forming composition.

<Example 2>
To 5 g of the solution containing 1 g of the polymer obtained in Synthesis Example 2, 0.25 g of tetramethoxymethyl glycoluril (Nippon Cytec Industries, Ltd., trade name: POWDERLINK [registered trademark] 1174) and pyridinium-p-toluenesulfonate 0 0.0156 g was mixed, and this mixture was dissolved in 20.43 g of ethyl lactate and 10.47 g of propylene glycol monomethyl ether acetate to obtain a solution. Then, it filtered using the polyethylene micro filter with the hole diameter of 0.10 micrometer, and also filtered using the polyethylene micro filter with the hole diameter of 0.05 micrometer, and prepared the resist underlayer film forming composition.

<Example 3>
To 5 g of the solution containing 1 g of the polymer obtained in Synthesis Example 3, 0.25 g of tetramethoxymethyl glycoluril (Nippon Cytec Industries, Ltd., trade name: POWDERLINK [registered trademark] 1174) and pyridinium-p-toluenesulfonate 0 0.0156 g was mixed, and this mixture was dissolved in 20.43 g of ethyl lactate and 10.47 g of propylene glycol monomethyl ether acetate to obtain a solution. Then, it filtered using the polyethylene micro filter with the hole diameter of 0.10 micrometer, and also filtered using the polyethylene micro filter with the hole diameter of 0.05 micrometer, and prepared the resist underlayer film forming composition.

<Example 4>
To 5 g of a solution containing 1 g of the polymer obtained in Synthesis Example 4, 0.25 g of tetramethoxymethyl glycoluril (Nippon Cytec Industries, Ltd., trade name: POWDERLINK [registered trademark] 1174) and pyridinium-p-toluenesulfonate 0 0.0156 g was mixed, and this mixture was dissolved in 20.43 g of ethyl lactate and 10.47 g of propylene glycol monomethyl ether acetate to obtain a solution. Then, it filtered using the polyethylene micro filter with the hole diameter of 0.10 micrometer, and also filtered using the polyethylene micro filter with the hole diameter of 0.05 micrometer, and prepared the resist underlayer film forming composition.

<Comparative Example 1>
A resist underlayer film forming composition comprising a copolymer represented by the following formula (4) as a polymer, and further comprising a crosslinking agent represented by the following formula (5) as an additive and pyridinium-p-toluenesulfonate. Prepared.

[Intermixing test with resist]
The resist underlayer film forming composition prepared in Examples 1 to 4 of the present invention and the resist underlayer film forming composition shown in Comparative Example 1 were each applied on a silicon wafer using a spinner. Baking was performed at 205 ° C. for 1 minute on a hot plate to form a resist underlayer film (film thickness: 0.10 μm).

  On top of this resist underlayer film, a commercially available resist solution (manufactured by Sumitomo Chemical Co., Ltd., trade name: PAR855) is applied using a spinner and baked on a hot plate at 100 ° C. for 1 minute to form a resist film ( 120 nm). After exposure using an exposure apparatus, post-exposure heating (PEB: Post Exposure Bake) was performed at 105 ° C. for 1 minute. After developing and rinsing the resist film, the thickness of the resist underlayer film is measured, and the resist underlayer film obtained from the resist underlayer film forming composition prepared in Example 1 to Example 4 is subjected to an interface between the resist film and the resist film. It was confirmed that mixing did not occur.

[Measurement of dry etching rate]
The resist underlayer film forming composition prepared in Examples 1 to 4 of the present invention and the resist underlayer film forming composition shown in Comparative Example 1 were each applied on a silicon wafer using a spinner. On the hot plate, it heated at 205 degreeC for 1 minute, and formed the resist underlayer film. Then, Japan Scientific Inc., using RIE system ES401, was measured dry etching rate under a condition of using CF ₄ as a dry etching gas.

A resist solution (trade name: PAR710, manufactured by Sumitomo Chemical Co., Ltd.) was applied onto a silicon wafer using a spinner, and a resist film was formed by the same method as described above. The dry etching rate was measured using RIE system ES401 manufactured by Nippon Scientific Co., Ltd. under the condition using CF ₄ as the dry etching gas.

  Five types of resist underlayer films obtained from the resist underlayer film forming compositions of Examples 1 to 4 and Comparative Example 1, and the dry etching rate of the resist film obtained from the resist solution manufactured by Sumitomo Chemical Co., Ltd. A comparison was made. Table 1 shows the ratio of the dry etching rate of the resist underlayer film to the dry etching rate of the resist film (selection ratio of the dry etching rate). The resist underlayer film obtained from the resist underlayer film forming composition of each example has a higher selectivity ratio of the dry etching rate than the resist underlayer film obtained from the resist underlayer film forming composition of Comparative Example 1. It was.

[Formation of resist pattern]
The resist underlayer film forming composition prepared in Example 1 of the present invention was spin-coated on a silicon wafer, and heated at 205 ° C. for 1 minute to form a resist underlayer film. On the resist underlayer film, an EUV resist solution (methacrylate resin resist) was spin-coated and heated to form a resist film. Using an EUV exposure apparatus (SMV EUV-ADT), exposure was performed under the conditions of NA = 0.25 and σ = 0.5. After the exposure, PEB was performed, cooled to room temperature on a cooling plate, developed and rinsed, and a resist pattern was formed. The evaluation was performed based on whether or not a 30 nm line and space can be formed and the line edge roughness (LER) of the pattern by observation from the upper surface of the pattern.

  As Comparative Example 2, the same test as described above was performed using a substrate in which a silicon wafer was subjected to HMDS (hexamethyldisilazane) treatment instead of forming a resist underlayer film.

  In this specification, in a line-and-space line pattern, the case where the cross section in the direction perpendicular to the substrate is rectangular is “good”, and the case where the cross section is tapered (trapezoidal) or skirted is “possible”. On the other hand, a case where it cannot be said that a line and space is formed due to pattern collapse or resolution failure is evaluated as “impossible”.

  The LER is measured by using a critical dimension scanning electron microscope (CD-SEM) to detect a pattern edge position two-dimensionally from the top and quantify the variation in the position as LER. Smaller LER is preferable because of less variation. Specifically, using the white band width detected by the CD-SEM, measure the line width of the portion of 70% of the height from the bottom of the pattern to the top surface by 400 points, and 3σ of those values is the LER value. It was. Here, σ represents a standard deviation.

  The focus depth (DOF) was measured using a line and space in which a resist position was formed by developing and rinsing after performing exposure while shifting the focus position up and down in steps of 20 nm on the basis of the optimum focus position. The allowable range of the line pattern width is set to ± 10% of the target pattern width, and the focus range without pattern collapse or pattern deformation is set as the DOF margin.

  As shown in Table 2, when the resist underlayer film forming composition prepared in Example 1 of the present invention is used, the LER value is small compared to Comparative Example 2, and the pattern dimensional accuracy in the manufacturing process is high. Was confirmed. In general, the LER value is desirably 4.0 nm or less. In Table 2, “> 4.5” means that the LER value is greater than 4.5 nm. Furthermore, as shown in Table 3, when the resist underlayer film forming composition obtained in Example 1 of the present invention was used, it was confirmed that a sufficient DOF margin was obtained even with fine line pattern widths of 30 nm and 28 nm.

Claims (5)

A resist underlayer film forming composition for lithography comprising a polymer having a structural unit represented by the following formulas (1) and (2), a crosslinking agent and a solvent.

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a methyl group, and L ₁ is a divalent divalent alkylene group having a single bond or a linear or branched alkylene group having 1 to 13 carbon atoms. Represents a linking group, A represents an aromatic ring group having at least one substituent containing a hydroxy group, and D represents a linear or branched hydroxyalkyl group having 1 to 13 carbon atoms. The resist underlayer film forming composition for lithography according to claim 1, wherein the polymer is a copolymer further having a structural unit represented by the following formula (3).

Wherein R ₃ represents a hydrogen atom or a methyl group, L ₂ represents a single bond or a linear or branched alkylene group having 1 to 13 carbon atoms, and E represents a group containing a lactone ring or adamantane Represents a group containing a ring.)   The resist underlayer film forming composition for lithography according to claim 1 or 2, further comprising a crosslinking catalyst.   A step of applying a resist underlayer film forming composition for lithography according to any one of claims 1 to 3 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, comprising: a step of forming; a step of exposing the resist underlayer film and a semiconductor substrate coated with the resist film; and a step of developing the resist film with a developer after the exposure.   The resist pattern forming method according to claim 4, wherein the exposure is performed using extreme ultraviolet rays.