JP5682363B2 - Topcoat composition and pattern forming method using the same - Google Patents

Description

The present invention relates to a topcoat composition that coats a resist film during pattern formation by photolithography and a pattern formation method using the same. In particular, the topcoat composition of the present invention is suitable for immersion lithography using an ultraviolet light having a wavelength of 300 nm or less, that is, an immersion exposure process.

In recent years, with the development of digital devices such as computers, it has become possible to perform calculation processing of enormous amounts of data such as two-dimensional and three-dimensional image data. In order to realize this, it is indispensable to increase the processing amount per unit time, and a memory capable of high-capacity and high-speed transfer suitable for high-speed processing and a higher-speed microprocessor are required. It is becoming a thing. In addition, it is expected that the processing capacity required for digital devices will increase more and more as the broadband of networks such as the Internet accelerates.

In order to satisfy these requirements, semiconductor elements and various device devices are required to have higher density and higher integration of elements and circuits. With high density and high integration, photolithography technology that enables fine and high-precision pattern processing has become more and more advanced, and an exposure apparatus that gives a higher-precision pattern has been studied. Photolithography refers to exposing a substrate surface coated with a photosensitive substance (photoresist) to a desired pattern. The photolithography technique is a technique for forming a resist pattern on a substrate based on a difference in solubility between the exposed portion of the photoresist and the unexposed portion due to the developer.

In such a photolithography technique, a finer and more accurate pattern can be obtained by using short-wavelength ultraviolet light. For example, a krypton fluoride excimer laser (hereinafter referred to as KrF) having a wavelength of 248 nm. An argon fluoride excimer laser (hereinafter referred to as ArF laser) having a wavelength of 193 nm is used for photolithography.

Further, in a reduction projection lens used in a stepper type exposure apparatus (reduction projection type exposure apparatus) which is a semiconductor element manufacturing apparatus, the resolution is greatly improved by the advancement of the optical design technique of the lens, and the high performance of the semiconductor element by the photolithography technique. Contributes greatly to density and high integration. The stepper type exposure apparatus reduces a reticle pattern, which is an ultrafine photomask, with a reduction projection lens, and exposes a photoresist on a wafer.

The resolution of a lens used in a stepper type exposure apparatus is represented by NA (numerical aperture), and in air, NA is about 0.9, which has already been achieved.

For example, in photolithography using an ArF laser (wavelength: 193 nm), an attempt has been made to raise NA to 1.0 or more by filling the space between the lens and the wafer with a medium having a higher refractive index than air. In particular, exposure by an immersion method using pure water (hereinafter sometimes simply referred to as water) as a medium, that is, immersion lithography is attracting attention.

However, in the immersion lithography, various problems have been pointed out because the resist film comes into contact with a medium (for example, water).

For example, the acid pattern generated by exposure and the amine compound added as a quencher are dissolved in water, so that the solubility of the resist changes and the pattern processing accuracy is reduced. And the exposed resist pattern collapse (pattern collapse) due to the swelling of the resist.

As a solution, it is effective to provide a topcoat layer on the resist film in order to completely separate the resist film and water.

Accordingly, the topcoat composition is required to have transparency, good developer solubility, solvent solubility, and resistance to pure water (water repellency). In the present invention, the solvent solubility means the solubility of the topcoat composition in the solvent when the topcoat composition is dissolved in the solvent to prepare the topcoat solution. The top coat solution is applied onto the resist to form a top coat film, and after exposure, the top coat film and the resist film in the exposed portion are dissolved. The solubility of the top coat film in the developer at that time is referred to.

As a composition for a top coat satisfying such requirements, for example, Patent Document 1 discloses a top coat composition containing a compound having a repeating unit containing a unit (structural unit) containing two or more hexafluoroisopropanol groups. Yes. The composition for top coat is excellent in developer solubility and can suppress swelling of the resist.

In addition, lactone units are used in resists to ensure adhesion to the substrate, and it is known that alicyclic lactones having excellent transparency and dry etching resistance are particularly excellent. be written.

JP 2005-316352 A

Ikuo Hasegawa and Katsumi Maeda, “Research and Development Trends of Polymers Having Lactone Skeleton”, “Polymer” October 2008 edition edited by the Society of Polymer Science, vol. 57 P850-855

In immersion lithography, if the medium (water) remains after exposure, it causes defects, and the topcoat composition is required to have water repellency. The topcoat composition preferably has both water repellency and developer solubility, which are contradictory properties.

However, the topcoat composition described in Patent Document 1 containing a compound having two or more hexafluoroisopropanol groups in its repeating unit has a plurality of OH groups and is hardly said to have excellent water repellency. .

As described above, alicyclic lactones are known to have excellent transparency and dry etching resistance, but their solvent solubility and developer solubility were not suitable for top coat applications.

Therefore, when the topcoat composition described in Patent Document 1 and the resist described in Non-Patent Document 1 are subjected to pattern formation by photolithography, particularly immersion lithography, using ultraviolet rays having a length of 300 nm or less. When used for the topcoat composition to be applied, there was concern about either water repellency or developer solubility.

The present invention solves such a problem, and a composition for top coat which is applied to a resist film when patterning is performed by photolithography, particularly immersion lithography, using a high energy beam or electron beam which is an electromagnetic wave having a wavelength of 300 nm or less. An object of the present invention is to provide a useful topcoat composition that provides a very fine and highly accurate pattern by providing suitable water repellency and developer solubility.

In the present invention, a fluorine-containing lactone monomer compound is introduced for the repeating unit in the chemical structure of the fluorine-containing polymer compound used in the topcoat composition. Thus, a top coat composition having both water repellency and developer solubility, which are contradictory properties, was obtained.

That is, in the present invention, when a topcoat composition is prepared using a fluorine-containing lactone polymer compound obtained by polymerizing a fluorine-containing lactone monomer compound as a material for application to photolithography, the composition is used for immersion lithography. A top coat composition having a developer solubility and water repellency useful for obtaining a fine, high-precision pattern was obtained.

Specifically, since a lactone compound is excellent in transparency, a fine and highly accurate pattern may be obtained by using it as a composition for a top coat for application to a resist film. Furthermore, by adding a specific fluorine-containing alkyl group to the lactone compound, a composition for a top coat having suitable water repellency and developer solubility when performing pattern formation by photolithography, particularly immersion lithography. Things were obtained.

That is, this invention is comprised from the following invention.

[Invention 1]
A topcoat composition comprising a fluorine-containing lactone polymer compound having a repeating unit represented by the following general formula (1) in a chemical structure .

(In the formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or A cyclic alkyl group having 3 to 6 carbon atoms, and each R ⁵ independently represents a hydrogen atom, a fluorine atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or a carbon number. (It is a 3-6 cyclic alkyl group, may have fluorine, and ^Rf is a C1-C4 linear perfluoroalkyl group each independently.)
That is, the repeating unit having a top fluorinated lactone polymer compound coating composition contains the present invention, hereinafter, combines the features of three points.

1. The point 1 carbon of the alcohol part of the ester bond is tertiary. That is, it has the feature of a repeating unit having acid decomposability.

No.2. The point that the alcohol site has a lactone structure. That is, it has the feature of a repeating unit having adhesiveness.

3 ^Rf which is a perfluoroalkyl group is added to the lactone structure. That is, the water repellency and solvent solubility are improved as compared with the prior art due to the introduction effect of the perfluoroalkyl group.

[Invention 2]
A topcoat composition comprising a fluorine-containing lactone polymer compound obtained by polymerizing a fluorine-containing lactone monomer compound represented by the following general formula (2) and another polymerizable monomer.

(In the formula (2), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or A cyclic alkyl group having 3 to 6 carbon atoms, and R ⁵ is a hydrogen atom, a fluorine atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or 3 to 6 carbon atoms. The cyclic alkyl group may have fluorine, and R ^f is a linear perfluoroalkyl group having 1 to 4 carbon atoms.)
That is, the fluorine-containing lactone monomer compound represented by the general formula (2) is polymerized with another polymerizable monomer other than the fluorine-containing lactone monomer compound represented by the general formula (2). It is the composition for topcoats of the invention 1.

[Invention 3]
R ⁵ is hydrogen atom, fluorine atom, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl. The topcoat composition of invention 1 or invention 2, wherein the composition is a group, a perfluoroethyl group or a cyclohexyl group.

[Invention 4]
The topcoat composition according to any one of Inventions 1 to ³ , wherein R ¹ , R ² and R ⁵ are methyl groups, and R ³ and R ⁴ are hydrogen atoms.

[Invention 5]
^Rf is a trifluoromethyl group, The composition for topcoats in any one of invention 1 thru ^| or invention 4 characterized by the above-mentioned.

In addition, the fluorinated lactone monomer compound represented by the general formula (2) can be polymerized with various polymerizable monomers, and a wide range of compounds are used. Among them, (meth) acrylic acid ester has high polymerizability, In particular, those having a hexafluoroisopropyl group are preferably used.

[Invention 6]
The top coat composition according to any one of inventions 2 to 5, wherein the other polymerizable monomer contains at least a (meth) acrylic acid ester.

Preferably, in the topcoat composition according to any one of inventions 1 to 5, wherein the other polymerizable monomer contains at least a (meth) acrylic acid ester having a hexafluoroisopropyl group.

The (meth) acrylic acid ester having a hexafluoroisopropyl group contributes to improving the polarity of the topcoat composition and improves the solvent solubility when preparing the topcoat solution.

In addition, the acid-decomposable ability to be decomposed by an acid is included in the fluorine-containing lactone monomer compound, but an acid-decomposable polymerizable monomer may be added separately, and the solubility of the topcoat film in the developer Will improve.

From the above, the top in which three or more components having a fluorine-containing lactone monomer compound represented by the general formula (2), a (meth) acrylic acid ester having a hexafluoroisopropyl group and an acid-decomposable polymerizable monomer are polymerized A coating composition is particularly preferred. That is, the polymerizable monomer is preferably a (meth) acrylic acid ester having a hexafluoroisopropyl group or an acid-decomposable polymerizable monomer.

[Invention 7]
The topcoat composition according to any one of inventions 2 to 6, wherein the polymerizable monomer is a (meth) acrylic acid ester having a hexafluoroisopropyl group or an acid-decomposable polymerizable compound.

[Invention 8]
The topcoat composition according to any one of Inventions 1 to 7, wherein the fluorine-containing lactone polymer compound has a mass average molecular weight of 1,000 or more and 1,000,000 or less.

When the mass average molecular weight is 1000 or more, the strength as a resist film is obtained, and when it is 1,000,000 or less, solvent solubility in a suitable solvent is obtained when a topcoat solution is obtained. It is easy to obtain a flat resist film.

[Invention 9]
A topcoat solution comprising the topcoat solution according to any one of Inventions 1 to 8 and a solvent.

[Invention 10]
A first step of applying the topcoat liquid of the invention 9 to a resist-coated substrate, a second step of heating the substrate, and a photomask using a high energy beam or an electron beam that is an electromagnetic wave having a wavelength of 300 nm or less A pattern forming method comprising: a third step of exposing the resist via the step; and a fourth step of dissolving the resist at the exposed portion using a developer to form a pattern.

According to the present invention, a composition for a topcoat containing a fluorine-containing lactone compound obtained by polymerizing a specific fluorine-containing lactone monomer compound, and a fluorine-containing lactone polymer compound obtained by polymerizing a fluorine-containing lactone monomer and another polymerizable monomer are included. Topcoat compositions and topcoat liquids of the present invention obtained by adding a solvent to these topcoat compositions were obtained. When the top coat solution is used, the water repellency and developer solubility are increased, so that the pattern after being applied on the resist film by photolithography, particularly immersion lithography, using ultraviolet light having a wavelength of 300 nm or less. When formed, an extremely fine and highly accurate pattern shape can be obtained.

Hereinafter, the present invention will be described in detail. The scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention can be appropriately changed and implemented without departing from the spirit of the present invention. In addition, this specification includes the whole of Japanese Patent Application No. 2010-39242 specification used as the basis of this application priority claim. In addition, all publications cited in the present specification, for example, prior art documents, and publications, patent publications and other patent documents are incorporated herein by reference.

Hereafter, each element which comprises this invention is demonstrated.

[Fluorine-containing lactone monomer compound]
The fluorine-containing lactone monomer compound represented by the general formula (2) used in the topcoat composition of the present invention is an ester-bonded carboxylic acid moiety of a polymerizable acrylic and an alcohol moiety of a fluorine-containing lactone having an alcohol moiety. It is. The topcoat composition prepared using the fluorine-containing lactone monomer compound has improved water repellency and developer solubility compared to a conventional topcoat composition prepared using a lactone monomer having no fluorine. Can be fulfilled.

That is, as shown in the general formula (2), the introduction of a fluorine-containing group further improves water repellency and developer solubility in a topcoat composition prepared using the fluorine-containing lactone monomer compound. be able to.

In the fluorine-containing lactone monomer compound represented by the general formula (2), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or 3 to 3 carbon atoms. A branched alkyl group having 6 or a cyclic alkyl group having 3 to 6 carbon atoms, and R ⁵ is a hydrogen atom, a fluorine atom, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkyl group having 3 to 6 carbon atoms. Or a cyclic alkyl group having 3 to 6 carbon atoms, which may have a fluorine atom, and R ^f is a linear perfluoroalkyl group having 1 to 4 carbon atoms.

In order to improve water repellency and developer solubility when the fluorine-containing lactone monomer compound is polymerized into a fluorine-containing lactone polymer compound , in the fluorine-containing lactone monomer compound represented by the general formula (2), R ⁵ is a hydrogen atom, fluorine atom, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl group , A perfluoroethyl group or a cyclohexyl group, R ¹ , R ² and R ⁵ are preferably methyl groups, R ³ and R ⁴ are preferably hydrogen atoms, and R ^f is a trimethyl group. A fluoromethyl group is preferred.

These fluorine-containing lactone monomer compounds can be synthesized by a general method. For example, a compound in which R ¹ , R ² and R ⁵ are methyl groups, R ³ and R ⁴ are hydrogen atoms, and R ^f is a trifluoromethyl group is a dehydration condensation reaction between a commercially available fluorine-containing lactonyl alcohol and methacrylic acid. Alternatively, it can be synthesized by a coupling reaction between a fluorine-containing lactonyl alcohol and methacrylic anhydride or methacrylic acid chloride, or a transesterification reaction between a fluorine-containing lactonyl alcohol and methyl methacrylate.

The fluorine-containing lactone monomer compound obtained by the reaction can be purified by a method such as recrystallization, chromatography, distillation or the like, if necessary.

[Fluorine-containing lactone polymer compound]
The fluorine-containing lactone polymer compound containing the repeating unit represented by the general formula (1) used in the composition for a top coat of the present invention is a polymerizable double having the fluorine-containing lactone monomer compound represented by the general formula (2). A bond is cleaved to form a polymer skeleton alone or copolymerized with a monomer compound having other polymerizable double bond described later.

In the fluorine-containing lactone polymer compound having a repeating unit represented by the general formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, A branched alkyl group having 3 to 6 carbon atoms or a cyclic alkyl group having 3 to 6 carbon atoms, and each R ⁵ is independently a hydrogen atom, a fluorine atom, a linear alkyl group having 1 to 6 carbon atoms, carbon A branched alkyl group having 3 to 6 carbon atoms or a cyclic alkyl group having 3 to 6 carbon atoms, which may have fluorine, and R ^f is each independently a linear perfluoroalkyl having 1 to 4 carbon atoms. It is a group.

Using a topcoat composition containing a fluorine-containing lactone polymer compound obtained by polymerizing the fluorine-containing lactone monomer compound represented by the general formula (2), water repellency and dissolution of a developer solution when a topcoat film is formed on a resist Among these fluorine-containing lactone monomer compounds, R ⁵ is a hydrogen atom, fluorine atom, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group. , Tert-butyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl group, perfluoroethyl group or cyclohexyl group, and R ¹ , R ² and R ⁵ are each a methyl group, and R ³ And R ⁴ is preferably a hydrogen atom, and R ^f is preferably a trifluoromethyl group.

[Production of fluorinated lactone polymer compound]
The polymerization method of the fluorine-containing lactone monomer compound for producing the fluorine-containing lactone polymer compound used in the topcoat composition of the present invention is not particularly limited as long as it is a generally used method, but radical polymerization, ion Polymerization or the like is preferable, and in some cases, coordination anion polymerization, living anion polymerization, cationic polymerization, ring-opening metathesis polymerization, vinylene polymerization, or vinyl addition is also possible.

The radical polymerization is carried out in the presence of a radical polymerization initiator or a radical initiator by a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization or emulsion polymerization, and is either batch-wise, semi-continuous or continuous. This can be done by operation.

The radical polymerization initiator is not particularly limited, and examples thereof include azo compounds, peroxide compounds, and redox compounds. Particularly, azobisisobutyronitrile, tert-butyl peroxypivalate, Di-tert-butyl peroxide, i-butyryl peroxide, lauroyl peroxide, succinic acid peroxide, dicinnamyl peroxide, di-n-propyl peroxydicarbonate, tert-butyl peroxyallyl monocarbonate, benzoyl peroxide, It is preferable to use hydrogen peroxide or ammonium persulfate.

The reaction vessel used for the polymerization reaction is not particularly limited. In the polymerization reaction, a polymerization solvent may be used. As the polymerization solvent, those that do not inhibit radical polymerization are preferable. For ester solvents, ethyl acetate, n-butyl acetate, ketone solvents, acetone, methyl isobutyl ketone, hydrocarbon solvents, cyclohexane, alcohol solvents. In the case of methanol, isopropyl alcohol or ethylene glycol monomethyl ether, and aromatic solvents, toluene, other than water, ether solvents, cyclic ether solvents, and chlorofluorocarbon solvents can be used. These solvents can be used alone or in admixture of two or more. Moreover, you may use together molecular weight regulators, such as a mercaptan. The reaction temperature of the copolymerization reaction is appropriately changed depending on the radical polymerization initiator or radical polymerization initiator, and is usually preferably 20 ° C. or higher and 200 ° C. or lower, particularly preferably 30 ° C. or higher and 140 ° C. or lower.

As a method for removing the organic solvent or water from the resulting solution or dispersion of the fluorine-containing lactone polymer compound, methods such as reprecipitation, filtration, and heating distillation under reduced pressure are possible.

[Polymerizable monomer]
The fluorine-containing lactone monomer compound forms a fluorine-containing lactone polymer compound as a copolymer polymer well with other polymerizable monomers, and such a fluorine-containing lactone polymer compound is a composition for top coat. Can be used for things. In the following, the polymerizable monomer is another monomer excluding the fluorine-containing lactone monomer compound.

The fluorine-containing lactone polymer compound used in the topcoat composition of the present invention is obtained by homopolymerizing the fluorine-containing lactone monomer compound represented by the general formula (2) or copolymerizing with other polymerizable monomers described below. Is. This fluorine-containing lactone polymer compound is fluorine-containing based on a carbon-carbon double bond having a double bond-containing group to which a substituent of R ⁵ of the fluorine-containing lactone monomer compound represented by the general formula (2) is bonded. It forms the skeleton of the lactone polymer compound, but other structures are not changed in the polymerization reaction.

In addition to the repeating unit represented by the general formula (1), the fluorine-containing lactone polymer compound has solvent solubility, developer solubility, and film formability, which are general necessary characteristics of a top coat for immersion lithography ( Various repeating units can be contained for the purpose of adjusting glass transition point), water repellency, resolving power, heat resistance, adhesion to a resist film or film slippage (hydrophobicity, alkali-soluble group selection) and the like.

Examples of the polymerizable monomer copolymerizable with the fluorine-containing lactone monomer compound of the present invention include maleic anhydride, acrylic acid esters, fluorine-containing acrylic acid esters, methacrylic acid esters, and fluorine-containing methacrylic acid. Esters, styrene compounds, fluorine-containing styrene compounds, vinyl ethers, fluorine-containing vinyl ethers, allyl ethers, fluorine-containing allyl ethers, olefins, fluorine-containing olefins, norbornene compounds, fluorine-containing norbornene compounds, sulfur dioxide, vinyl silane, vinyl sulfonic acid and vinyl Examples thereof include at least one polymerizable monomer selected from sulfonic acid esters.

Hereinafter, the polymerizable monomer will be described.

<(Meth) acrylic acid ester polymerizable monomer>
The fluorine-containing lactone monomer compound represented by the general formula (2) can be polymerized with the above-mentioned various polymerizable monomers, and a wide variety thereof is used. Among them, (meth) acrylic acid ester has a high polymerization property, Those having a hexafluoroisopropyl group are preferably used.

The (meth) acrylic acid ester having a hexafluoroisopropyl group contributes to improving the polarity of the fluorine-containing lactone polymer compound and improves the solvent solubility when preparing the topcoat solution.

In addition, the acid-decomposable ability to be decomposed by an acid is included in the fluorine-containing lactone monomer compound, but an acid-decomposable polymerizable monomer may be added separately, and the solubility of the topcoat film in the developer Will improve.

From the above, the fluorine-containing lactone monomer compound represented by the general formula (2), the (meth) acrylic acid ester having a hexafluoroisopropyl group and the three or more components having an acid-decomposable polymerizable monomer are polymerized. A fluorine lactone polymer compound is particularly preferred as the topcoat composition. That is, the polymerizable monomer is preferably a (meth) acrylic acid ester having a hexafluoroisopropyl group or an acid-decomposable polymerizable monomer.

In the present invention, the polymerizable monomer can easily be copolymerized with the fluorine-containing lactone monomer compound represented by the general formula (2). A polymerizable monomer selected from the group consisting of an acid ester and a fluorine-containing methacrylic acid ester is particularly preferable, and is suitably used for the topcoat composition of the present invention.

The acrylic acid ester as the polymerizable monomer includes methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, n-octyl acrylate, 21-ethylhexyl acrylate Lauryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tert-butyl acrylate, 3-oxocyclohexyl acrylate, adamantyl acrylate, alkyladamantyl acrylate, cyclohexyl acrylate or tricyclodecanyl acrylate, or ethylene glycol, propylene glycol or Acrylates containing tetramethylene glycol groups are listed. It is. In addition, acrylates containing ethylene glycol, propylene glycol or tetramethylene glycol groups, acrylates containing acrylonitrile, methacrylonitrile or alkoxysilane, tert-butyl acrylate 3-oxocyclohexyl acrylate, adamantyl acrylate, methyl adamantyl acrylate, ethyl Examples thereof include adamantyl acrylate, droxyadamantyl acrylate, cyclohexyl acrylate, tricyclodecanyl acrylate, and acrylate or acrylic acid having a lactone ring or norbornene ring ring structure.

Examples of the methacrylic acid ester as the polymerizable monomer include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2- Mention may be made of ethylhexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate, or methacrylates containing ethylene glycol, propylene glycol or tetramethylene glycol groups. In addition, methacrylates containing ethylene glycol, propylene glycol or tetramethylene glycol groups, or methacrylates containing acrylonitrile, methacrylonitrile or alkoxysilane, tert-butyl methacrylate, 3-oxocyclohexyl methacrylate, adamantyl methacrylate, methyladamantyl methacrylate , Ethyladamantyl methacrylate, hydroxyadamantyl methacrylate, cyclohexyl methacrylate, tricyclodecanyl methacrylate, or methacrylate having a ring structure of a lactone ring or a norbornene ring, or methacrylic acid.

In addition, the fluorine-containing acrylic ester and the fluorine-containing methacrylate ester as the polymerizable monomer include a polymerizable monomer in which a fluorine atom or a group having a fluorine atom is contained at the α-position of the acrylic, or an ester site. A fluorine-containing compound which is an acrylic ester or methacrylic ester comprising a substituent containing a fluorine atom, and which contains fluorine at both the α-position and the ester portion, can be used in the present invention.

Further, the polymerizable monomer may have a cyano group introduced at the α-position, and the trifluoromethyl group or trifluoroethyl group at the α-position of the non-fluorinated acrylic acid ester or methacrylic acid ester described above. Alternatively, a polymerizable monomer provided with a nonafluoro-n-butyl group is preferably used.

On the other hand, the polymerizable monomer containing fluorine at the ester site is a perfluoroalkyl group, a fluoroalkyl group that is a fluoroalkyl group as the ester site, or a unit that has a cyclic structure and a fluorine atom at the ester site. Acrylic acid ester or methacrylic acid having a fluorinated benzene ring, a fluorinated cyclopentane ring, a fluorinated cyclohexane ring or a fluorinated cycloheptane ring whose cyclic structure is substituted with a fluorine atom, a trifluoromethyl group or a hexafluoroisopropyl hydroxyl group Examples include acid esters.

As the polymerizable monomer, an acrylic acid or methacrylic acid ester whose ester moiety is a fluorine-containing t-butyl ester group can be used.

As the fluorine-containing functional group, a polymerizable monomer used in combination with the α-position fluorine-containing alkyl group can be used.

Therefore, polymerizable monomers include 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate , Heptafluoroisopropyl acrylate, 1,1-dihydroheptafluoro-n-butyl acrylate, 1,1,5-trihydrooctafluoro-n-pentyl acrylate, 1,1,2,2-tetrahydrotridecafluoro-n- Octyl acrylate, 1,1,2,2-tetrahydroheptadecafluoro-n-decyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1,1,1 , 3,3,3-hexafluoroisopropyl methacrylate, heptaful Roisopropyl methacrylate, 1,1-dihydroheptafluoro-n-butyl methacrylate, 1,1,5-trihydrooctafluoro-n-pentyl methacrylate, 1,1,2,2-tetrahydrotridecafluoro-n-octyl methacrylate 1,1,2,2-tetrahydroheptadecafluoro-n-decyl methacrylate, perfluorocyclohexyl methyl acrylate, perfluorocyclohexyl methyl methacrylate, 6- [3,3,3-trifluoro-2-hydroxy-2- ( Trifluoromethyl) propyl] bicyclo [2.2.1] heptyl-2-yl acrylate, 6- [3,3,3-trifluoro-2-hydroxy-2- (trifluoromethyl) propyl] bicyclo [2. 2.1] heptyl-2-yl 2- ( Trifluoromethyl) acrylate, 6- [3,3,3-trifluoro-2-hydroxy-2- (trifluoromethyl) propyl] bicyclo [2.2.1] heptyl-2-yl methacrylate, 1,4- Bis (1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl) cyclohexyl acrylate, 1,4-bis (1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl ) Cyclohexyl methacrylate, or 1,4-bis (1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl) cyclohexyl 2-trifluoromethyl acrylate.

Examples of the polymerizable monomer include unsaturated amides represented by acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, and diacetone acrylamide.

Other examples of the polymerizable monomer include acrylonitrile and methacrylonitrile-containing vinyl silane.

<Other polymerizable monomers>
Examples of other polymerizable monomers other than acrylic acid esters and methacrylic acid esters include maleic acid, fumaric acid or maleic anhydride, and examples include alkoxysilane-containing vinylsilanes.

Further, the styrene compound or fluorine-containing styrene compound as the polymerizable monomer has one or more functional groups modified with a hexafluorocarbinol group or a hydroxyl group in addition to styrene, fluorinated styrene, or hydroxystyrene. A compound in which individual bonds are formed. More specifically, styrene substituted with an aromatic ring hydrogen with a fluorine atom or trifluoromethyl group, such as pentafluorostyrene, trifluoromethyl styrene, or bistrifluoromethyl styrene, a hexafluoroisopropyl hydroxyl group, or a functional group in which the hydroxyl group is protected. Styrene in which the aromatic ring hydrogen is replaced with a group. Further, the above styrene and perfluorovinyl group-containing styrene in which a halogen, an alkyl group or a fluorine-containing alkyl group is bonded to the α-position can be mentioned. Styrene or hydroxystyrene substituted with hydrogen by fluorine atom or trifluoromethyl group, styrene having halogen, alkyl group or fluorine-containing alkyl group bonded to α-position, and styrene containing perfluorovinyl group are preferable and can be used in the present invention. It is.

As the polymerizable monomer, vinyl ether, fluorine-containing vinyl ether, allyl ether or fluorine-containing allyl ether can be used, and an alkyl containing a methyl group, an ethyl group, a propyl group, a butyl group, a hydroxyethyl group or a hydroxybutyl group. Vinyl ether or alkyl allyl ether is preferable and can be used.

In addition, the polymerizable monomer includes a cyclohexyl group, a norbornyl group or an aromatic ring and a cyclic vinyl or allyl ether having a hydrogen or carbonyl bond in the cyclic structure, or a part or all of hydrogen of the above functional group. Fluorine-containing vinyl ether or fluorine-containing allyl ether in which is substituted with a fluorine atom can be used.

In the present invention, a polymerizable monomer containing a vinyl ester, vinyl silane, olefin, fluorine-containing olefin, norbornene compound, fluorine-containing norbornene compound, or other polymerizable unsaturated bond can also be used in the present invention.

In addition, ethylene, propylene, isobutene, cyclopentene or cyclohexene is used as the polymerizable monomer, and vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene is used as the fluorinated olefin. Hexafluoropropylene or hexafluoroisobutene.

Examples of the norbornene compound as the polymerizable monomer include a fluorine-containing norbornene compound or a norbornene compound having a plurality of core structures.

As described above, the polymerizable compound includes fluorine-containing olefin, allyl alcohol, fluorine-containing allyl alcohol, homoallyl alcohol, fluorine-containing homoallyl alcohol, acrylic acid, α-fluoroacrylic acid, α-trifluoromethylacrylic acid, methacrylic acid. And all acrylic esters, methacrylic esters, fluorine-containing acrylic esters or fluorine-containing methacrylates, 2- (benzoyloxy) pentafluoropropane, 2- (methoxyethoxymethyloxy) pentafluoropropene described in the present specification 2- (tetrahydroxypyranyloxy) pentafluoropropene, 2- (benzoyloxy) trifluoroethylene, or an unsaturated compound of 2- (methoxymethyloxy) trifluoroethylene, cyclopentadiene, A norbornene compound produced by Diels-Alder addition reaction with clohexadiene, which is 3- (5-bicyclo [2.2.1] hepten-2-yl) -1,1,1-trifluoro-2- ( Trifluoromethyl) -2-propanol. The polymerizable monomer copolymerizable with the fluorine-containing lactone monomer compound used in the above-described topcoat composition of the present invention may be used alone or in combination of two or more.

[Introduction of acid labile groups]
The fluorine-containing lactone polymer compound used in the topcoat composition of the present invention is a fluorine-containing lactone polymer compound copolymerized with a fluorine-containing lactone monomer compound and a polymerizable monomer having an acid labile group. May be.

The purpose of introducing an acid labile group into the fluorine-containing lactone polymer compound used in the composition for topcoat of the present invention is by exposure to high energy rays such as ultraviolet rays, excimer lasers, X-rays or electron beams having a wavelength of 300 nm or less, or electron beams. It is to improve the solubility of the developer in the alkaline developer of the topcoat film in the vicinity of the exposed portion while capturing the acid generated in the resist film and diffusing into the topcoat film.

The polymerizable monomer having an acid labile group for introducing an acid labile group into the fluorine-containing lactone polymer compound used in the composition for a topcoat of the present invention has an acid labile group derived from a photoacid generator. What is necessary is just to hydrolyze and remove | eliminate by the generated acid, and a polymerizable group should just be an alkenyl group or a cycloalkenyl group, and is vinyl group, 1-methylvinyl group, or 1-trifluoromethylvinyl group. Some are preferred. In addition, if an acid labile group is exemplified, a polymerizable monomer having at least one acid labile group selected from an ester site of a tertiary alcohol, a carbonate ester site of a tertiary alcohol, and an alkoxymethylene ether site is preferable. Can be used.

[Fluorine-containing lactone polymer compound]
In the fluorine-containing lactone polymer compound having the repeating unit represented by the general formula (1), the repeating unit (a) represented by the general formula (1) and the repeating unit (b) based on the polymerizable monomer described above The molar ratio (copolymerization ratio) is the solvent performance, film formability (glass transition point), water repellency, resolving power, heat resistance, adhesion to the resist film, or film, which is a general required performance of the topcoat. It is appropriately set to adjust slip (hydrophobicity, alkali-soluble group selection) and the like.

The fluorine-containing lactone polymer compound according to the present invention may be (a) a single polymer compound, and the repeating unit (a) represented by the general formula (1) and the repeating unit (b) based on the polymerizable monomer described above. The mass ratio is expressed as (a) :( b) by mass%, and is 0.1% -99.9%: 99.9% -0.1%, respectively, or 1% -99%: 99% to 1%. Further, it can be 10% to 90%: 90% to 10%, and preferably 30% to 70%: 70% to 30%. When the content of the repeating unit (a) is less than 0.1%, the solubility during development is inferior, and when it exceeds 99.9%, it is difficult to adjust the solubility, which is not preferable.

The above repeating unit is preferably a repeating unit (a) based on acrylic acid or methacrylic acid ester having a lactone group and a repeating unit (b) based on acrylic acid or methacrylic acid ester having a polar group. In that case, what contains 10 mass% or more and 60 mass% or less of repeating units based on a lactone group containing monomer compound is preferable, and what contains 20 mass% or more and 50 mass% or less is still more preferable.

The molecular weight of the fluorine-containing lactone polymer compound used in the topcoat composition of the present invention is 1,000 to 1,000,000 as a mass average molecular weight measured by gel permeation chromatography (GPC), and 2,000. ~ 500,000 is preferred. If the weight average molecular weight is less than 1,000, the strength of the coating film is insufficient, and if it exceeds 1,000,000, the solubility in a solvent is lowered, and it becomes difficult to obtain a smooth coating film, which is not preferable. The dispersity (Mw / Mn) is preferably 1.01 to 5.00, more preferably 1.01 to 4.00, particularly preferably 1.01 to 3.00, and most preferably 1.10 to 2.50. preferable.

Moreover, since the fluorine-containing lactone polymer compound used in the composition for topcoat of the present invention contains a 5-membered ring lactone structure and a trifluoromethyl group bonded to the ring, the light absorbency at a wavelength of 300 nm or less is very low. Have Therefore, in the exposure, it is possible to use a high energy ray of 300 nm or less.

Moreover, since the fluorine-containing lactone polymer compound used for the composition for topcoats of this invention has a cyclic structure, it gives a comparatively high glass transition temperature (Tg). When the glass transition temperature (Tg) is low, the resist constituent components are diffused into the topcoat layer, which is not preferable. Although the fluorine-containing lactone polymer according to the present invention depends on the components to be copolymerized, it has a Tg of about 120 ° C. or higher, and is higher than the baking temperature (100 ° C.), so that such diffusion can be suppressed.

[Topcoat solution]
In the present invention, the fluorine-containing lactone polymer compound produced above is dissolved in an organic solvent or a mixed solution of water and an organic solvent to form a topcoat solution. The topcoat liquid of the present invention is applied to a resist formed on a substrate and then dried to form a topcoat film.

In the topcoat solution, solubility and casting characteristics can vary depending on the molecular weight. Polymers with a high molecular weight have a slower dissolution rate in the developer, and dissolution rates can be faster with a low molecular weight. However, the molecular weight can be controlled by adjusting the polymerization conditions as appropriate based on common knowledge in this technical field. Is possible.

[solvent]
In addition, as an organic solvent used for dissolving the fluorine-containing lactone polymer compound, it is an essential requirement that the solvent is difficult to erode the resist film in the lower layer and that it is difficult to extract additives from the resist film. Become.

The organic solvent that hardly erodes the resist film and hardly extracts additives from the resist film includes hydrocarbon solvents, alcohols, ethers, esters, and fluorine-based solvents, although depending on the composition of the underlying resist film.

In particular, alkanes represented by pentane, hexane, heptane, octane, nonane or decane, alicyclic hydrocarbon solvents, butanol (normal, iso, tertiary), methyl ethyl carbinol, pentanol, amyl alcohol, hexyl Alcohols, heptyl alcohols and alcohols represented by 4-methyl-2-pentanol, preferably hydrocarbon solvents partially substituted with fluorine are preferably used. Further, the hydrocarbon solvent partially substituted with fluorine is an alkane or alicyclic hydrocarbon solvent or alcohol, in which a part of the hydrogen is substituted with a fluorine atom. . By introducing fluorine atoms, it is possible to effectively dissolve the polymer compound of the present invention and to perform coating without damaging the underlying resist film.

Other solvents include acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone or 2-heptanone as ketones, polyhydric alcohols and derivatives thereof such as ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, Propylene glycol monoacetate, dipropylene glycol, dipropylene glycol monoacetate, monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether, dioxane as cyclic ethers, methyl lactate, lactic acid as esters Ethyl, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy Methyl pionate or ethyl ethoxypropionate, xylene as an aromatic solvent, toluene, chlorofluorocarbon as a fluorinated solvent, alternative chlorofluorocarbon, perfluoro compound, hexafluoroisopropyl alcohol, and other high-boiling weak solvents for the purpose of improving coatability A terpene-based petroleum naphtha solvent or a paraffin solvent can be used, and these may be used alone or in combination of two or more.

The amount of the solvent to be blended in the topcoat liquid is not particularly limited, but preferably the solid content concentration of the topcoat composition is 1% by mass or more and 25% by mass or less, more preferably 2% by mass or more and 15% by mass or less. Use as follows. It is possible to adjust the film thickness of the resin film to be formed by adjusting the solid content concentration of the top coat composition.

In the topcoat composition of the present invention, a hydrophobic additive for suppressing the influence on swelling and penetration of water and an acidic additive for promoting solubility in a developer can also be used. Used for.

[Pattern formation]
The topcoat composition according to the present invention can be used as a topcoat film without any limitation on the type of the resist film in the lower layer. That is, even if the lower layer resist is an arbitrary resist system such as a negative type, a positive type, and a composite type, it can be suitably used.

Although the wavelength used for exposure is not limited, as described above, high-energy rays of 300 nm or less can be used, and KrF excimer laser (248 nm), ArF excimer laser (193 nm), F ₂ laser (157 nm), extreme single ultraviolet (Extreme) Ultra Violet (EUV), electron beam (EB) or X-ray can be suitably used, and ArF excimer laser is particularly preferably employed.

In particular, the topcoat composition of the present invention is suitably applied in immersion lithography.

Hereinafter, a case where the present invention is used in manufacturing a device (semiconductor device) using immersion lithography will be described. Although it does not specifically limit as a device, Central processing unit (Central Processing Unit, CPU), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM) formed in a silicon wafer, a compound semiconductor substrate, an insulating substrate, etc. Semiconductor devices manufactured by microfabrication such as

First, a resist composition solution is applied onto a support such as a silicon wafer or a semiconductor manufacturing substrate with a spinner or the like, and then pre-baked to form a resist layer. Conditions for this step can be appropriately set according to the composition of the resist composition to be used.

Next, the top coat liquid of the present invention is uniformly applied with a spinner or the like to the surface of the resist film formed as described above, and then subjected to heat treatment, thereby forming a top coat film on the resist film. A resin film is formed.

The substrate on which this resin layer is formed is immersed in a medium such as water, and then irradiated with ultraviolet rays of 300 nm or less through a desired mask pattern. At this time, the exposure light reaches the resist layer through the medium (for example, water) and the top coat layer. Further, since the resist layer is separated from the medium (for example, water) by the top coat layer, the medium (for example, water) is immersed in the resist layer to swell, or conversely, the resist is eluted into the medium (for example, water). There is nothing.

After the exposed substrate is baked, it is developed using a developer, for example, an alkaline aqueous solution such as an aqueous tetramethylammonium hydroxide solution having a concentration of 0.1% by mass to 10% by mass. In the development processing, the top coat film is first completely dissolved, and then the resist film in the exposed portion is dissolved. That is, it is possible to dissolve and remove a part of the topcoat layer and the resist layer by one development process, and it is possible to obtain a resist pattern corresponding to a desired mask pattern.

Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to these examples.

(Synthesis example)
[Synthesis of fluorine-containing lactone monomer compound]
As a synthesis example of the fluorine-containing lactone monomer compound used in the topcoat composition of the present invention, the following synthesis method of 5,5-dimethyl-2-oxo-3- (trifluoromethyl) tetrahydrofuran-3-yl methacrylate Will be described.

A 200 mL three-necked flask equipped with a thermometer and a stirrer coated with tetrafluoroethylene and 3-hydroxy-5,5-dimethyl-3- (trifluoromethyl) dihydrofuran-2 represented by the structural formula (3) 3H) -one 30.0 g (0.15 mol), methacrylic anhydride 24.5 g (0.16 mol), methanesulfonic acid 0.3 g (0.003 mol), and 2,2 ′ as a polymerization inhibitor -Methylene-bis (4-methyl-6-tert-butylphenol), manufactured by Seiko Chemical Co., Ltd., trade name: 0.15 g (0.5% by mass) of non-flex MBP was added and stirred at 50 ° C. or higher with a stirrer, 55 It was made to stir for 1.5 hours within the range below ℃. The reaction solution was measured by gas chromatography. As a result, 5,5-dimethyl-2-oxo-3- (trifluoromethyl) tetrahydrofuran-3-yl methacrylate (hereinafter referred to as compound (5)) represented by the target structural formula (4) was obtained. 44.1) was obtained by 94.1 mass%. Others were 1% by mass of the raw material 3-hydroxy-5,5-dimethyl-3- (trifluoromethyl) dihydrofuran-2 (3H) -one, and the others were 4.8% by mass. After adding 60 g of diisopropyl ether, it was added with an aqueous sodium hydroxide solution, followed by washing with water to adjust the pH to 7. Thereafter, the organic layer was cooled to −20 ° C. and stirred for 1 hour. The precipitated crystals were filtered and dried to obtain 31.1 g of compound (4). When the composition was examined by gas chromatography, the target compound (4) was 99.8% by mass, and the others were 0.2% by mass. The yield was 77%.

<Physical Properties of 5,5-Dimethyl-2-oxo-3- (trifluoromethyl) tetrahydrofuran-3-yl methacrylate (Compound (4))>
¹ H NMR (solvent: CDCl ₃ , reference material: TMS); δ 6.25 (d, J = 1.0 Hz, 1H), 5.75 (d, J = 1.4 Hz, 1H), 2.64 (d , J = 14.8 Hz, 1H), 2.53 (d, J = 14.8 Hz, 1H), 1.97 (s, 3H), 1.68 (s, 3H), 1.51 (s, 3H 19F NMR (solvent: CDCl ₃ , reference material: CCl ₃ F); δ-78.94 (s, 3F)
Next, synthesis of a fluorine-containing polymer compound using the fluorine-containing lactone monomer compound is shown in Example 1 and Example 2.

[Example 1]
(Synthesis of fluorinated lactone polymer compound 1)
Copolymerization of the compound (4) and the methacrylic acid ester represented by the structural formula (5) (hereinafter, compound (5)) was carried out by the following method.

In a flask equipped with a stirrer, the compound (4) (2.0 g), the following compound (5) (4.0 g), t-buty peroxypivalate (manufactured by NOF Corporation, trade name: Perbutyl) as a polymerization initiator PV) was added in order so that methyl ethyl ketone would be 400 wt% as a polymerization solvent so as to be 4 mol%. The flask was heated in a 75 ° C. oil bath and allowed to react for 16 hours. After the reaction, the reaction solution was added to n-hexane and stirred, and the produced precipitate was filtered off and dried in vacuo at 50 ° C. for 10 hours. The molecular weight was determined from gel permeation chromatography (GPC, standard substance: polystyrene), and the composition molar ratio was determined from NMR. The composition, molecular weight and yield are shown in Table 1.

[Example 2]
(Synthesis 2 of fluorinated lactone polymer compound)
Copolymerization of the compound (4) and the methacrylic acid ester represented by the structural formula (6) (hereinafter, compound (6)) was carried out by the following method.

In a flask equipped with a stirrer, the above compound (4) (2.0 g), the following compound (6) (4.0 g), and t-buty peroxypivalate (manufactured by NOF Corporation, trade name: Perbutyl) as a polymerization initiator PV) was added in order so that methyl ethyl ketone would be 400 wt% as a polymerization solvent so as to be 4 mol%. The flask was heated in a 75 ° C. oil bath and allowed to react for 16 hours. After the reaction, the reaction solution was poured into n-hexane and stirred, and the produced precipitate was filtered off and dried in vacuo at 50 ° C. for 10 hours. The molecular weight was determined from gel permeation chromatography (GPC, standard substance: polystyrene), and the composition molar ratio was determined from NMR. The composition, molecular weight and yield are shown in Table 1.

[Comparative Example 1]
Copolymerization of a lactone compound not containing fluorine represented by the structural formula (7) (hereinafter, compound (7)) and compound (5) was carried out by the following method. In Comparative Example 1, no fluorine-containing lactone compound is used.

In a flask equipped with a stirrer, the following compound (7) (2.0 g), compound (5) (4.0 g), t-buty peroxypivalate (manufactured by NOF Corporation, trade name: Perbutyl PV) as a polymerization initiator ) Was added in order so that methyl ethyl ketone would be 400 wt% as a polymerization solvent so as to be 4 mol%. The flask was heated in a 75 ° C. oil bath and allowed to react for 16 hours. After the reaction, the reaction solution was added to n-hexane and stirred, and the produced precipitate was filtered off and dried in vacuo at 50 ° C. for 10 hours. The molecular weight was determined from gel permeation chromatography (GPC, standard substance: polystyrene), and the composition molar ratio was determined from NMR. The composition, molecular weight and yield are shown in Table 1.

[Preparation of composition for top coat]
Using the fluorine-containing lactone polymer compounds obtained in Example 1, Example 2 and Comparative Example 1, a topcoat solution was prepared as shown in Table 2. The values in parentheses in Table 2 are composition ratios and are expressed as mass ratios.

When dissolved in the solvent 1 (4-methyl-2-pentanol: MIBC) or the solvent 2 (n-decane / 2-octanol = 90/10 mass ratio) shown in Table 2 at the composition ratio shown in Table 2, respectively. All were obtained six uniform and transparent topcoat solutions (topcoat solution 1, topcoat solution 2, topcoat solution 3, topcoat solution 4, topcoat solution 5, and topcoat solution 6). In adjusting the composition of the top coat solution, all showed good solubility. The results are shown in Table 2.

[Formation of top coat film]
Each top coat solution was applied to a membrane filter on a silicon wafer that had been previously coated with a 78 nm antireflection film (trade name: ARC29A, manufactured by Nissan Chemical Industries, Ltd., and then baked at 200 ° C. for 60 seconds). After filtering at (0.2 μm), spin coating was performed using a spinner at 1,500 rpm, and drying was performed on a hot plate at 100 ° C. for 90 seconds. As a result, uniform top coat films were obtained. In Table 2, the top coat films 1 to 6 are shown. Topcoat films 1-6 correspond to topcoat solutions 1-6)
[Evaluation of top coat film]
With respect to the obtained top coat films 1 to 6, the receding contact angle was evaluated.

Specifically, the receding contact angle of water droplets was measured by the expansion / contraction method of a dynamic contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.) An initial droplet size of 7 μL was sucked at a speed of 6 μL / second for 8 seconds, and a value with a stable dynamic contact angle during suction was defined as a receding contact angle. The results are shown in Table 2. All showed good receding contact angles.

Next, developer solubility was evaluated for the obtained top coat films 1 to 4. When the topcoat films 1 to 4 were immersed in a 2.38 mass% tetramethylammonium hydroxide aqueous solution (developer) at room temperature for 60 seconds, the films dissolved and disappeared quickly. The results are shown in Table 2.

[Evaluation of top coat film coated on resist film]
Subsequently, the top coat films 1 to 6 shown in Table 2 were used to evaluate the top coat film from the two-layer film of the resist layer and the top coat layer on the silicon wafer by the process shown below.

First, the synthesis of the resist polymer compound will be described. Methacrylic acid ester (hereinafter referred to as compound (8)) represented by the following structural formula (8) and methacrylic acid ester (hereinafter referred to as compound (9)) represented by structural formula (9) and structural formula (10) A methacrylic acid ester (hereinafter, compound (10)) represented was copolymerized to obtain a resist polymer compound.

In a flask equipped with a stirrer, compound (8) (12.0 g), compound (9) (10.1 g), compound (10) (10.8 g), AIBN (product name 2, 2 ′) as a polymerization initiator. -1.35 g of azobis (isobutyronitrile), Wako Pure Chemical Industries, Ltd.) and 2-butanone (65.8 g) as a polymerization solvent were sequentially added. The flask was heated in a 75 ° C. oil bath and allowed to react for 16 hours. The solution after completion of the reaction was added dropwise to 500 g of n-hexane to obtain a white precipitate. This precipitate was separated by filtration and dried under reduced pressure at 60 ° C. to obtain 29.6 g of a white solid (resist polymer compound) (yield 90% by mass). From the gel permeation chromatography (GPC, standard substance: polystyrene), the molecular weight was 11500, and the molecular weight dispersion MW / MN was 2.1.

The resist polymer compound was dissolved in propylene glycol monomethyl ether acetate (PGMEA), and the solid content was adjusted to 12%. Furthermore, 5 parts by weight of triphenylsulfonium nonafluorobutanesulfonate as an acid photogenerator was dissolved in 100 parts by weight of the polymer and 2 parts by weight of isopropanolamine as a base to prepare a resist solution. The obtained resist solution was spin-coated on a silicon wafer using a spinner on a silicon wafer treated with an antireflection film, and then dried on a hot plate at 100 ° C. for 90 seconds to obtain a resist film having a thickness of 150 nm. . The top coat liquid 1 filtered through a membrane filter (0.2 μm) on this resist film is spin-coated using a spinner, and then dried on a hot plate at 100 ° C. for 90 seconds to form a resist layer and a top coat layer. A two-layer film composed of a resin film having a total film thickness of 200 nm was formed on a silicon wafer.

Similarly, a top coat solution 2, a top coat solution 3, a top coat solution 4, a top coat solution 5, and a top coat solution 6 are respectively applied on a silicon wafer on which a resist film is formed, and the resist layer and the top coat layer are separated. A silicon wafer formed by forming a two-layer film and a resin film having a total film thickness of 200 nm was formed.

Subsequently, the following pure water immersion treatment, an alkali developer solubility test of the top coat film, and an exposure resolution test were performed. The results of these tests are shown in Table 3.

In addition, the pure water immersion test was performed as follows.

Each silicon wafer on which the resin film is formed by the above method is immersed in 20 ml of pure water for 10 minutes to extract the eluate, and then the extract is measured by ion chromatography to determine the presence or absence of the eluate. As a result of confirmation, no peak attributed to a component of the resist film was observed. This indicates that by providing the topcoat film, elution of the resist component from the resist film into water was suppressed.

Next, an alkali developer solubility test of the topcoat film was performed as follows.

Each silicon wafer on which the resin film is formed is immersed in an alkaline developer (2.38 mass% tetramethylammonium hydroxide aqueous solution) at room temperature using a resist development analyzer RDA-790 (manufactured by RISOTEC JAPAN). The dissolution rate was measured. The results are shown in Table 3. The top coat films 1 to 4 showed a good dissolution rate, but the top coat film 5 and the top coat film 6 did not show a good dissolution rate.

Next, an exposure resolution test was performed as follows.

A silicon wafer on which a topcoat solution 1 to 6 was applied on the resist film to form a resin film was pre-baked at 100 ° C. for 90 seconds, and then exposed at 193 nm through a photomask. Pure water was added dropwise for 2 minutes while rotating the exposed wafer. Thereafter, post-exposure baking was performed at 120 ° C. for 60 seconds, and development was performed with an alkaline developer. As the alkaline developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used. The obtained pattern was observed with a scanning electron microscope (SEM), and the resolution was evaluated. The results are shown in Table 3. In the resists in the top coat films 1 to 4, formation of a rectangular pattern was observed. Although formation of a rectangular pattern was observed in the resist in the top coat film 5, many defects were observed. In the top coat film 6, a pattern with a residue in the shape of a head beam that was considered to have poor solubility was obtained.

This is because in Comparative Example 1, an appropriate developer solubility was not obtained because the fluorine-containing lactone monomer compound was not used as a raw material for the fluorine- containing lactone polymer compound contained in the topcoat composition. is there.

The top coat liquid of the present invention, which is obtained by combining a specific fluorine-containing lactone monomer compound with another polymerizable monomer and further adding a solvent, is applied onto a resist film by providing suitable water repellency and solvent solubility. When a pattern is formed by photolithography using an exposure apparatus that uses an electromagnetic wave having a wavelength of 300 nm or less as a light source, particularly by immersion lithography, an extremely fine pattern shape can be obtained. it can.

The topcoat composition of the present invention uses an exposure apparatus that uses ultrashort wavelength ultraviolet light as a light source, such as a KrF laser (wavelength, 248 nm), an ArF laser (wavelength, 193 nm), and the like. It is useful as a composition for top coat applied on a resist film when forming a pattern with extremely fine and high precision.

Moreover, the composition for topcoats of this invention may be applicable also to the lithography technique using high energy rays, such as X-rays and a gamma ray, and an electron beam.

Claims (10)

The following general formula (1):

(In the formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or A cyclic alkyl group having 3 to 6 carbon atoms, and each R ⁵ independently represents a hydrogen atom, a fluorine atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or a carbon number. (It is a 3-6 cyclic alkyl group, may have fluorine, and ^Rf is a C1-C4 linear perfluoroalkyl group each independently.)
A topcoat composition comprising a fluorine-containing lactone polymer compound having a repeating unit represented by: The following general formula (2):

(In the formula (2), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or A cyclic alkyl group having 3 to 6 carbon atoms, and R ⁵ is a hydrogen atom, a fluorine atom, a linear alkyl group having 1 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or 3 to 6 carbon atoms. The cyclic alkyl group may have fluorine, and R ^f is a linear perfluoroalkyl group having 1 to 4 carbon atoms.)
A topcoat composition comprising a fluorine-containing lactone polymer compound obtained by polymerizing a fluorine-containing lactone monomer compound represented by formula (2) and another polymerizable monomer. R ⁵ is hydrogen atom, fluorine atom, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl. The topcoat composition according to claim 1, wherein the composition is a group, a perfluoroethyl group, or a cyclohexyl group. ^{4. The} topcoat composition according to claim ¹ , wherein R ¹ , R ^2, and R ⁵ are methyl groups, and R ³ and R ⁴ are hydrogen atoms. 5. ^Rf is a trifluoromethyl group, The topcoat composition of any one of Claims 1 thru ^| or 4 characterized by the above-mentioned. 6. The topcoat composition according to any one of claims 2 to 5, wherein the other polymerizable monomer contains at least a (meth) acrylic acid ester. The other polymerizable monomer is a (meth) acrylic acid ester having a hexafluoroisopropyl group or an acid-decomposable polymerizable compound, according to any one of claims 2 to 6. Composition for top coat. The composition for topcoat according to any one of claims 1 to 7, wherein the fluorine-containing lactone polymer compound has a mass average molecular weight of 1,000 or more and 1,000,000 or less. A topcoat solution comprising the topcoat composition according to any one of claims 1 to 8 and a solvent. A first step of applying the topcoat liquid according to claim 9 to a resist-coated substrate, a second step of heating the substrate, and a high energy beam or electron beam that is an electromagnetic wave having a wavelength of 300 nm or less A pattern forming method comprising: a third step of exposing the resist through a photomask; and a fourth step of dissolving the resist at the exposed portion using a developer to form a pattern.