JP4778835B2 - Protective film forming composition and pattern forming method using the same - Google Patents

Description

  The present invention relates to a protective film forming composition used in a semiconductor manufacturing process such as an IC, a circuit board such as a liquid crystal or a thermal head, and a lithography process for other photo applications, and a pattern forming method using the same. It is. In particular, the present invention relates to a protective film forming composition suitable for exposure with an immersion projection exposure apparatus using far ultraviolet light having a wavelength of 300 nm or less as a light source, and a pattern forming method using the same.

Along with the miniaturization of semiconductor elements, the wavelength of the exposure light source has been shortened and the numerical aperture (high NA) of the projection lens has been increased. Currently, an NAF 0.8 light source using an ArF excimer laser having a wavelength of 193 nm is used.
Four exposure machines have been developed. These can be expressed by the following equations as is generally well known.
(Resolving power) = k ₁ · (λ / NA)
(Depth of focus) = ± k ₂ · λ / NA ²
Where λ is the wavelength of the exposure light source, NA is the numerical aperture of the projection lens, and k ₁ and k ₂ are coefficients related to the process.

An exposure machine using a F ₂ excimer laser having a wavelength of 157 nm as a light source has been studied for higher resolution by further shortening the wavelength. Lens materials and resists used in the exposure apparatus for shorter wavelength have been studied. Because the materials used in the process are very limited, it is very difficult to stabilize the manufacturing cost and quality of the apparatus and materials, and the exposure apparatus and resist that have sufficient performance and stability within the required period are not in time. The possibility is coming out.

As a technique for increasing the resolving power in an optical microscope, a so-called immersion method in which a high refractive index liquid (hereinafter also referred to as “immersion liquid”) is filled between a projection lens and a sample is known.
This “immersion effect” means that when λ ₀ is the wavelength of the exposure light in the air, n is the refractive index of the immersion liquid with respect to air, θ is the convergence angle of the light beam, and NA ₀ = sin θ. The above-described resolving power and depth of focus can be expressed by the following equations.
(Resolving power) = k ₁ · (λ ₀ / n) / NA ₀
(Depth of focus) = ± k ₂ · (λ ₀ / n) / NA ₀ ²
That is, the immersion effect is equivalent to using an exposure wavelength having a wavelength of 1 / n. In other words, in the case of a projection optical system with the same NA, the depth of focus can be increased n times by immersion.
This is effective for all pattern shapes, and can be combined with a super-resolution technique such as a phase shift method and a modified illumination method which are currently being studied.

Examples of apparatuses in which this effect is applied to transfer of a fine pattern of a semiconductor element include Patent Document 1 (Japanese Patent Publication No. 57-153433), Patent Document 2 (Japanese Patent Application Laid-Open No. 7-220990), and Patent Document 3 (Japanese Patent Application Laid-Open No. Hei 5-153433). No. 6-124873), but a resist suitable for the immersion exposure technique is not discussed.
Patent Document 4 (Japanese Patent Laid-Open No. 10-303114) points out that the refractive index control of the immersion liquid is important because the change in the refractive index of the immersion liquid causes deterioration of the projected image due to the wavefront aberration of the exposure machine. Disclosed is a water to which the temperature coefficient of the refractive index of the immersion liquid is controlled within a certain range and, as a suitable immersion liquid, an additive that lowers the surface tension or increases the surface activity is added. Has been. However, the disclosure of additives and the resist suitable for the immersion exposure technique are not discussed.

Recent progress in immersion exposure technology is described in Non-Patent Document 1 (SPIE Proc 4688, 11 (2002)), Non-Patent Document 2
(J. Vac. Sci. Tecnol. B, 17 (1999)). In the case of using an ArF excimer laser as a light source, pure water (refractive index at 193 nm: 1.44) is considered to be most promising as an immersion liquid in terms of handling safety, transmittance at 193 nm, and refractive index. .
When an F ₂ excimer laser is used as a light source, a solution containing fluorine has been studied from the balance between transmittance and refractive index at 157 nm. However, a sufficient product has not yet been seen in terms of environmental safety and refractive index. It has not been issued. From the degree of immersion effect and the degree of completeness of the resist, the immersion exposure technique is considered to be installed in the ArF exposure machine earliest.

Since the resist for KrF excimer laser (248 nm), an image forming method called chemical amplification has been used as an image forming method for a resist in order to compensate for sensitivity reduction due to light absorption. Explaining by taking a positive chemical amplification image forming method as an example, the acid generator in the exposed area is decomposed by exposure to generate an acid upon exposure, and the generated acid is reacted as a reaction catalyst by post exposure baking (PEB). Is used to change an alkali-insoluble group to an alkali-soluble group, and an exposed portion is removed by alkali development.
In the immersion exposure, the resist film and the optical lens are filled with an immersion liquid (also referred to as an immersion liquid), and then exposed through a photomask to transfer the photomask pattern to the resist film. At this time, there is a case where the immersion liquid penetrates into the resist film to cause no image formation (Non-patent Document 3). Further, it is expected that the exposure of the resist is expected because organic substances and the like are eluted from the resist film into the immersion liquid, and impurities are mixed in the immersion liquid and contaminate the lens and the exposure apparatus.

As a solution to avoid such problems, a protective film (hereinafter also referred to as “topcoat” or “overcoat”) is provided between the resist film and the lens so that the resist and water do not come into direct contact with each other. A method is known (for example, Non-Patent Document 3).
However, it is not known that sufficient performance is obtained as a material used for the top coat.

Japanese Patent Publication No.57-153433 JP-A-7-220990 JP-A-6-124873 JP-A-10-303114 Proc. SPIE, 2002, Vol. 4688, p. 11 J.Vac.Sci.Tecnol.B, 17 (1999) Nikkei Microdevices, April 2004 issue

  An object of the present invention is to form a protective film soluble in an alkaline developer on a resist film. In pattern formation by immersion exposure, the resist film is protected from the immersion liquid while being immersed in the immersion liquid. Composition for forming a protective film that can be peeled off with an alkaline developer used in the development process without swelling of the protective film, can form a good pattern, and can also form a protective film that has excellent followability to immersion liquid And an immersion exposure pattern forming method using the composition.

The present invention is a protective film forming composition having the following constitution and a pattern forming method using the same, thereby solving the above-mentioned problems of the present invention.
<1> A protective film forming composition for forming a protective film provided on a resist film,
(A) A group that is decomposed by the action of an alkali developer and generates an alkali-soluble group by repeating the unit (x) containing at least one fluorine atom having a group represented by the following general formula (F2) or (F3) A fluorine-containing atom resin having a repeating unit (y) having a group containing a group that decomposes by the action of an alkali developer and generates an alkali-soluble group, and
(S) As a solvent, an alcohol solvent alone, or a nonpolar solvent selected from a hydrocarbon solvent, a halogenated hydrocarbon solvent, and a fluorine-containing solvent, an alcohol solvent, an ether solvent, a nitrogen-containing solvent, and an ester solvent And mixed solvents with polar solvents selected from ketone solvents
A protective film-forming composition comprising:

In general formulas (F2) and (F3),
R _{57 to} R ₆₁ each independently represents a hydrogen atom, a fluorine atom or an alkyl group. However, at least one of R _{57 to} R ₆₁ represents a fluorine atom or an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom.
R ₆₂ to R ₆₄ each independently represent a hydrogen atom, a fluorine atom or an alkyl group. However, at least one of R _{62 to} R ₆₄ represents an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom. R ₆₂ and R ₆₃ may be connected to each other to form a ring.
<2> The protective film-forming composition as described in <1> above, wherein the solvent (S) contains an aliphatic hydrocarbon solvent or a fluorine solvent as the nonpolar solvent.
<3> The protective film-forming composition as described in <1> or <2> above, wherein the group that decomposes by the action of an alkali developer and generates an alkali-soluble group is a group having a lactone structure.
<4> The protective film-forming composition as described in <3> above, wherein the lactone structure is a structure represented by the following general formula LC1-4.

Rb ₂ represents a substituent, n ₂ represents the number of substituents of 0 or more, a plurality of Rb ₂ may be the same or different, and a plurality of Rb ₂ are bonded to form a ring May be.
<5> A resist film is formed, a protective film is formed on the resist film by the protective film-forming composition according to any one of <1> to <4> above, and the laminate is liquid. A pattern forming method comprising performing immersion exposure and developing.
<6> The pattern forming method as described in <5> above, wherein immersion exposure is performed through pure water as the immersion liquid.
Although this invention has the structure of said <1>-<6>, it is described below including other matters.

<1> A protective film forming composition for forming a protective film provided on a resist film,
(A) a fluorine-containing resin containing a group that decomposes by the action of an alkali developer and generates an alkali-soluble group; and
(S) A protective film-forming composition comprising a solvent that does not dissolve the resist film.
<2> The protective film formation according to claim 1, comprising a repeating unit (x) containing at least one fluorine atom and a repeating unit (y) having a group that decomposes by the action of an alkali developer and generates an alkali-soluble group. Composition.
<3> The protective film-forming composition as described in <1> or <2>, wherein the group that decomposes by the action of an alkali developer and generates an alkali-soluble group is a group having a lactone structure.

<4> The repeating unit represented by the following general formula (Ax) and the repeating unit represented by the following general formula (Ay) are contained in any one of <1> to <3> resin.

Rz represents a hydrogen atom, a methyl group, a trifluoromethyl group, or a hydroxymethyl group.
Rax represents an organic group containing at least one fluorine atom.
Ray represents an organic group having a group (Y) that decomposes by the action of an alkali developer to generate an alkali-soluble group.

<5> The protective film-forming composition as described in any one of <1> to <4>, wherein the solvent (S) contains either an aliphatic hydrocarbon solvent or a fluorine solvent.
<6> A resist film is formed, a protective film is formed on the resist film with the protective film-forming composition according to any one of <1> to <5> to form a laminate, and the laminate is subjected to immersion exposure. The pattern formation method characterized by developing.
<7> The pattern forming method according to <6>, wherein immersion exposure is performed through pure water as the immersion liquid.

  The protective film forming composition of the present invention can be peeled off with an alkali developer, can provide a good resist profile in pattern formation by immersion exposure, and is excellent in immersion liquid followability. An object is to provide a suitable protective film forming composition and a pattern forming method using the same.

  Hereinafter, the present invention will be described in detail.

[1] (A) Fluorine-containing resin containing a group (Y) that decomposes by the action of an alkali developer to generate an alkali-soluble group (hereinafter also referred to as resin (A))
The “group that decomposes by the action of an alkali developer and generates an alkali-soluble group” possessed by the resin (A) means that the resin (A) decomposes by the action of the alkali developer, resulting in an alkali-soluble group in the resin (A). It is a group that increases the solubility of A) in an alkaline developer.
Examples of the alkali-soluble group include a carboxyl group, a sulfonamide group, a sulfonylimide group, a bisulsulfonylimide group, and an aliphatic alcohol in which the α-position is substituted with an electron-withdrawing group.

The resin (A) may be any resin as long as it has at least one fluorine atom and a group (Y) that decomposes by the action of an alkali developer and generates an alkali-soluble group, but at least one fluorine atom And a repeating unit (y) having a group (Y) having a group (Y) that decomposes by the action of an alkali developer and generates an alkali-soluble group.
A group having a lactone structure is particularly preferred as the group (Y) that decomposes by the action of an alkali developer to generate an alkali-soluble group.

Examples of the partial structure having a fluorine atom contained in the resin (A) include an alkyl group having 1 to 10 carbon atoms (preferably 1 to 4 carbon atoms) having a fluorine atom, a cycloalkyl group having a fluorine atom, and a fluorine atom. An aryl group having
The alkyl group having a fluorine atom is a linear or branched alkyl group substituted with at least one fluorine atom, and may further have another substituent. The cycloalkyl group having at least one fluorine atom is a monocyclic or polycyclic cycloalkyl group substituted with at least one fluorine atom, and may further have another substituent.
Examples of the aryl group having at least one fluorine atom include those in which at least one fluorine atom is substituted on an aryl group such as a phenyl group or a naphthyl group, and may further have other substituents.

  Specific examples of the alkyl group having a fluorine atom, the cycloalkyl group having a fluorine atom, or the aryl group having a fluorine atom are shown below.

In general formulas (F2) to (F4),
R _{57 to} R ₆₈ each independently represents a hydrogen atom, a fluorine atom or an alkyl group. However, at least one of R _{57 to} R ₆₁ , R _{62 to} R ₆₄ and R _{65 to} R ₆₈ is a fluorine atom or an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom (preferably having a carbon number of 1 ~ 4). R _{57 to} R ₆₁ and R _{65 to} R ₆₇ are preferably all fluorine atoms. R ₆₂ , R ₆₃ and R ₆₈ are preferably an alkyl group (preferably having 1 to 4 carbon atoms) in which at least one hydrogen atom is substituted with a fluorine atom, and preferably a perfluoroalkyl group having 1 to 4 carbon atoms. Further preferred. R ₆₂ and R ₆₃ may be connected to each other to form a ring.

Specific examples of the general formula (F2) include p-fluorobenzene, pentafluorobenzene, 3,5-di (trifluoromethyl) benzene, and the like.
Specific examples of general formula (F3) include trifluoroethyl group, pentafluoropropyl group, pentafluoroethyl group, heptafluorobutyl group, hexafluoroisopropyl group, heptafluoroisopropyl group, hexafluoro (2-methyl) isopropyl group. , Nonafluorobutyl group, octafluoroisobutyl group, nonafluorohexyl group, nonafluoro-t-butyl group, perfluoroisopentyl group, perfluorooctyl group, perfluoro (trimethyl) hexyl group, 2,2,3,3- A tetrafluorocyclobutyl group, a perfluorocyclohexyl group, etc. are mentioned. Hexafluoroisopropyl group, heptafluoroisopropyl group, hexafluoro (2-methyl) isopropyl group, octafluoroisobutyl group, nonafluoro-t-butyl group and perfluoroisopentyl group are preferable, and hexafluoroisopropyl group and heptafluoroisopropyl group are preferable. Further preferred.

Specific examples of the group represented by the general formula (F4) include, for example, —C (CF ₃ ) ₂ OH, —C (C ₂ F ₅ ) ₂ OH, —C (CF ₃ ) (CH ₃ ) OH, -CH (CF ₃₎ OH and the like, -C (CF _{3) 2} OH is preferred.

  The resin (A) is preferably a resin containing at least one selected from the group of repeating units represented by the following general formulas (CI) to (C-III).

In the general formulas (CI) to (C-III),
R _{1 to} R ₃ are each independently a hydrogen atom, a fluorine atom, or an alkyl group (preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and the alkyl group having a substituent is particularly fluorinated. An alkyl group can be mentioned).
W _{1 to} W ₂ each independently represents an organic group containing at least one fluorine atom.
R _{4 to} R ₇ are a hydrogen atom, a fluorine atom, or an alkyl group (preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and examples of the alkyl group having a substituent include a fluorinated alkyl group. Can represent).
However, at least one of R _{4 to} R ₇ represents a fluorine atom. R ₄ and R ₅ or R ₆ and R ₇ may form a ring.
L _{1 and} L ₂ each independently represents a single bond or a linking group. Examples of the linking group include an alkylene group, a phenyl group, an ether group, a thioether group, a carbonyl group, an ester group, an amide group, a urethane group, or a urea group, or a combination of two or more groups. It is done.
Q represents a monocyclic or polycyclic cyclic aliphatic group. That is, it represents an atomic group that contains two bonded carbon atoms (C—C) and forms an alicyclic structure.

  The general formula (CI) is more preferably the following general formulas (C-Ia) to (C-Id).

R _{10 to} R ₁₁ are each independently a hydrogen atom, a fluorine atom, or an alkyl group (preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and the alkyl group having a substituent is particularly a fluorinated alkyl group. Group).
W _{3 to} W ₆ each independently represents an organic group containing at least one fluorine atom.

Examples of the organic group containing at least one fluorine atom of W _{1 to} W ₆ include the groups described above as the partial structure having a fluorine atom.

  Specific examples of the repeating unit represented by the general formula (CI) are shown below. X represents a hydrogen atom, a methyl group, a fluorine atom, or a trifluoromethyl group.

  Specific examples of the repeating unit represented by formula (C-II) are shown below.

  Specific examples of the repeating unit represented by formula (C-III) are shown below.

As the repeating unit having a group (Y) that decomposes by the action of an alkali developer and generates an alkali-soluble group, an alkali is added to the main chain of the resin through a linking group, such as a repeating unit of an acrylate ester or a methacrylate ester. A repeating unit to which a group (Y) that decomposes by the action of a developer and generates an alkali-soluble group is bonded, and a polymerization initiator that has a group (Y) that decomposes and generates an alkali-soluble group by the action of an alkali developer And any repeating unit introduced at the end of the polymer chain using a chain transfer agent during polymerization is preferred.
Examples of the group (Y) that decomposes by the action of an alkali developer to generate an alkali-soluble group include an acid anhydride, a maleimide anhydride, or a group having a lactone structure, and a group having a lactone structure is particularly preferable. The group having an acid anhydride, maleimide anhydride or lactone structure may be an acid anhydride, maleimide anhydride or lactone structure itself.
As the group having a lactone structure, any group can be used as long as it contains a lactone structure, and preferably a group containing a 5- to 7-membered ring lactone structure. A structure in which another ring structure is condensed to form a structure or a spiro structure is preferable.

  It is more preferable to have a repeating unit having a lactone structure represented by any of the following general formulas (LC1-1) to (LC1-16). Further, a group having a lactone structure may be directly bonded to the main chain. Preferable lactone structures include (LC1-1), (LC1-4), (LC1-5), (LC1-6), (LC1-13) and (LC1-14).

  The lactone structure portion may or may not have a substituent (Rb2). As preferred substituents (Rb2), an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 4 to 7 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an alkoxycarbonyl group having 1 to 8 carbon atoms, a carboxyl group, Examples thereof include a halogen atom, a hydroxyl group, a cyano group, and an acid-decomposable group (a group that decomposes by the action of an acid to produce an alkali-soluble group). When n2 is 2 or more, a plurality of Rb2s may be the same or different, and a plurality of Rb2s may be bonded to form a ring.

  Examples of the repeating unit having a group having a lactone structure represented by any one of the general formulas (LC1-1) to (LC1-16) include a repeating unit represented by the following general formula (AI). .

In general formula (AI), R _b0 represents a hydrogen atom, a halogen atom, or an alkyl group (preferably having 1 to 4 carbon atoms). Preferable substituents that the alkyl group for R _b0 may have include a hydroxyl group and a halogen atom.

Examples of the halogen atom for R _b0 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R _b0 is preferably a hydrogen atom or a methyl group.

A _b is an alkylene group, a divalent linking group having a monocyclic or polycyclic alicyclic hydrocarbon structure, a single bond, an ether group, an ester group, a carbonyl group, a carboxyl group, or a divalent group obtained by combining these. Represents. Preferably a single bond, -Ab ₁ -CO ₂ - is a linking group represented by.
Ab ₁ is a linear, branched alkylene group, monocyclic or polycyclic cycloalkylene group, preferably a methylene group, an ethylene group, a cyclohexyl group, an adamantyl group, or a norbornyl group.

  V represents a group represented by any one of the general formulas (LC1-1) to (LC1-16). The bonding position with Ab in the group represented by any one of formulas (LC1-1) to (LC1-16) may be arbitrary.

The repeating unit having a lactone structure usually has an optical isomer, but any optical isomer may be used. One optical isomer may be used alone, or a plurality of optical isomers may be mixed and used. When one kind of optical isomer is mainly used, the optical purity (ee) thereof is preferably 90 or more, more preferably 95 or more.
Specific examples of the repeating unit having a group having a lactone structure are shown below, but are not limited thereto.

  The most preferred repeating unit having a lactone group includes the following repeating units. By selecting an optimal lactone structure, the pattern profile is improved.

  Examples of the repeating unit having a group having an acid anhydride or maleimide structure that is a group (Y) that decomposes by the action of an alkali developer to generate an alkali-soluble group include a repeating unit represented by the following general formula (VIII). It is done.

In the general formula (VIII), Z ₂ represents —O— or —N (R ₄₁ ) —. R ₄₁ represents a hydrogen atom, a hydroxyl group, an alkyl group, or —OSO ₂ —R ₄₂ . R ₄₂ represents an alkyl group, a cycloalkyl group or a camphor residue. The alkyl group of R ₄₁ and R ₄₂ may be substituted with a halogen atom (preferably a fluorine atom) or the like.

Examples of the repeating unit represented by the general formula (VIII) include the following specific examples.
It is not limited to these.

  The content of the repeating unit having a group (Y) that decomposes by the action of an alkali developer and generates an alkali-soluble group is preferably 1 to 50 mol%, more preferably 10 to 10%, based on all repeating units of the resin (A). 50 mol%, more preferably 10 to 30 mol%.

  The resin (A) may further have a repeating unit having an alkali-soluble group. As an alkali-soluble group, a carboxyl group, a sulfonamide group, a sulfonylimide group, a bisulsulfonylimide group, an aliphatic alcohol substituted with an electron-attracting group at the α-position (preferably a structure represented by the following general formula (F1)) It is more preferable to have a repeating unit having a carboxyl group.

In general formula (F1),
R _{50 to} R ₅₅ each independently represents a hydrogen atom, a fluorine atom or an alkyl group. However, at least one of R _{50 to} R ₅₅ represents a fluorine atom or an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and all of R _{50 to} R ₅₅ are preferably fluorine atoms. .
By containing the repeating unit having an alkali-soluble group, the resolution in contact hole applications is increased. The repeating unit having an alkali-soluble group includes a repeating unit in which an alkali-soluble group is directly bonded to the main chain of the resin, such as a repeating unit of acrylic acid or methacrylic acid, or an alkali in the main chain of the resin through a linking group. Either a repeating unit to which a soluble group is bonded, or a polymerization initiator or chain transfer agent having an alkali-soluble group is used at the time of polymerization and introduced at the end of the polymer chain, and the linking group is monocyclic or polycyclic. It may have a cyclic hydrocarbon structure. Most preferred are acrylic acid and methacrylic acid.
As for content of the repeating unit which has an alkali-soluble group, 0-40 mol% is preferable with respect to all the repeating units in resin, More preferably, it is 1-20 mol%, More preferably, it is 5-10 mol%.

  Specific examples of the repeating unit having an alkali-soluble group are shown below.

  In addition to the above repeating structural units, the resin (A) may contain various repeating structural units for the purpose of adjusting solvent solubility, applicability, standard developer suitability, miscibility with resist, resist profile, and the like. it can.

  Such a repeating structural unit has, for example, one addition polymerizable unsaturated bond selected from acrylic acid esters, methacrylic acid esters, acrylamides, methacrylamides, allyl compounds, vinyl ethers, vinyl esters and the like. A compound etc. can be mentioned.

  In addition, any addition-polymerizable unsaturated compound that can be copolymerized with monomers corresponding to the above various repeating structural units may be copolymerized.

  In the alicyclic hydrocarbon-based acid-decomposable resin, the molar ratio of each repeating structural unit is appropriately set in order to adjust the solvent solubility, coatability, standard developer suitability, miscibility with the resist, and the like.

  The resin (A) preferably contains a repeating unit represented by the following general formula (Ax) and a repeating unit represented by the following general formula (Ay).

Rz represents a hydrogen atom, a methyl group, a trifluoromethyl group, or a hydroxymethyl group.
Rax represents an organic group containing at least one fluorine atom.
Ray represents an organic group having a group (Y) that decomposes by the action of an alkali developer to generate an alkali-soluble group.

  Examples of the organic group containing a fluorine atom of Rax are the same as those described above. Examples of the organic group having a group (Y) that decomposes by the action of an alkaline developer of Ray to generate an alkali-soluble group include the same groups as described above.

  Specific examples of the repeating unit represented by the general formula (Ax) include those exemplified as the repeating unit represented by the general formula (C-1), and specific examples of the repeating unit represented by the general formula (Ay). As an example, what was illustrated as a repeating unit which has group which has a lactone structure can be mentioned.

  The content of fluorine atoms in the resin (A) is preferably 5 to 80% by mass and more preferably 10 to 80% by mass with respect to the molecular weight of the resin (A). Moreover, it is preferable that the repeating unit containing a fluorine atom is 50-80 mol% in resin (A), and it is more preferable that it is 50-80 mol%.

  The weight average molecular weight (in terms of standard polystyrene) of the resin (A) is preferably 1000 to 100,000, more preferably 1000 to 50,000, and still more preferably 2000 to 15,000.

  The resin (A) preferably has a residual monomer amount of 0 to 5% by mass, and more preferably 0 to 1% by mass, from the viewpoint of suppressing elution of low molecular components into the immersion liquid. The molecular weight distribution (Mw / Mn, also referred to as dispersity) is preferably 1 to 3, more preferably 1.2 to 2.2.

Resin (A) can be synthesized by a conventional method.
For example, as a general synthesis method, monomer species are charged into a reaction vessel in a batch or in the course of reaction, and if necessary, a reaction solvent such as ethers such as tetrahydrofuran, 1,4-dioxane, diisopropyl ether, methyl ethyl ketone, Dissolve the composition of the present invention such as ketones such as cyclohexanone, ester solvent such as ethyl acetate, and propylene glycol monomethyl ether acetate described later in a solvent for homogenization, and then inert such as nitrogen and argon Polymerization is started using a commercially available radical initiator (azo initiator, peroxide, etc.) as necessary under a gas atmosphere. If desired, an initiator is added or added in portions, and after completion of the reaction, it is put into a solvent and a desired polymer is recovered by a method such as powder or solid recovery. The concentration of the reaction is usually 20% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more. The reaction temperature is usually from 10 ° C to 150 ° C, preferably from 30 ° C to 120 ° C, more preferably from 50 to 100 ° C.
The resin (A) can be synthesized by various methods without being limited to the radical polymerization. In addition to radical polymerization, it can also be synthesized by, for example, cationic polymerization, anionic polymerization, addition polymerization, cyclopolymerization, polyaddition, polycondensation, addition condensation and the like.
One repeating structural unit may be used, or a plurality of repeating structural units may be used in combination. In the present invention, the resins may be used alone or in combination.

  Resin (A), like the resist composition, is naturally low in impurities such as metals, but the residual monomer and oligomer components are below the predetermined values, for example, 0.1 mass by HPLC (High Permeation Liqid Chromatography). %, And the like, so that not only can the sensitivity, resolution, process stability, pattern shape and the like as a resist be further improved, but also a resist having no temporal change such as foreign matter in liquid or sensitivity can be obtained.

[2] Solvent The protective film forming composition for immersion exposure of the present invention is prepared by dissolving in a water-insoluble organic solvent that does not dissolve the resist film.

Here, “does not dissolve the resist film” means that a solution in which a resin contained in the resist film is dissolved in a solvent is applied on a silicon wafer, dried, and then immersed in a solvent (B) for 1 minute at 23 ° C. When the film thickness is measured later, it refers to the property that the film thickness does not decrease, and the rate of change ([change in thickness / film thickness before immersion treatment] × 100%) is preferably 10% or less.
As the water-insoluble organic solvent that does not dissolve the resist film, a solvent whose solubility parameter is about 2 to 5 larger than that of the resist solvent is preferable, the solubility parameter is 2.5 to 5, preferably 3 to 5, and more preferably 3. The thing of 5-5 is good.

Solvents used in the protective film-forming composition of the present invention are preferably used as a mixed solvent by mixing a plurality of solvents in order to further improve the effects of the present invention.
Although it does not specifically limit as a mixed solvent, With respect to nonpolar solvents, such as a hydrocarbon solvent, a halogenated hydrocarbon solvent, and a fluorine-containing nonpolar solvent, alcohol solvent, ether solvent, nitrogen-containing solvent, ester type A mixed solvent to which a polar solvent such as a solvent or a ketone solvent is added is preferable.
The hydrocarbon solvent represents a solvent composed of only carbon atoms and hydrogen atoms. Examples of the hydrocarbon solvent include aromatic hydrocarbon solvents and aliphatic hydrocarbon solvents. Examples of the aromatic hydrocarbon solvent include toluene, ethylbenzene, amylbenzene, isopropylbenzene, xylene, cyclohexylbenzene, naphthalene, dimethylnaphthalene, cymene, tetralin, biphenyl, mesitylene and the like. Aliphatic hydrocarbon solvents include hexane, heptane, octane, nonane, decane, dodecane, cyclohexane, methylcyclohexane, ethylcyclohexane, p-menthane, decalin, isooctane, isododecane, cyclohexene, cyclopentane, dipentene, isopar E, isopar G, Isopar H, Isopar L, Isopar M (manufactured by Kokura Kosan Co., Ltd.), turpentine oil, decahydronaphthalene, limonene, benzine, Kyowasol C-800, shellsol, isosol, ligroin (manufactured by Gordo Kogyo Co., Ltd.) ) And the like. When the exposure light source is ArF exposure, an aliphatic hydrocarbon solvent is preferable from the viewpoint of 193 transparency.
Examples of the halogenated hydrocarbon solvent include methylene chloride, hexyl chloride, chlorobenzene, bromobenzene and the like.

  Fluorine solvents include 1,4-difluorobenzene, 1,1,2,2-tetrachlorodifluoroethane, tetrafluoropropanol, ethyl trifluoroacetoacetate, perfluoroheptane, hexafluoroisopropanol, perfluorobutylethanol, pentafluoro Examples include propanol, hexafluorobenzene, perfluorobutyltetrahydrofuran, perfluoropolyethers, and fluorophenols.

  The solvent is preferably a solvent having a boiling point of 100 ° C to 200 ° C.

Alcohol solvents include amyl alcohol, isoamyl alcohol, hexanol, 3-heptanol, 2-ethylbutanol, 2-ethylhexanol, octanol, nonanol, neopentyl alcohol, cyclohexanol, tetrahydrofurfuryl alcohol, propylene glycol, tetrafluoropropanol , Hexafluoroisopropanol, perfluorobutylethanol, pentafluoropropanol, fluorophenol and the like.
Examples of the ether solvent include anisole, dioxane, dioxolane, dibutyl ether, tetrahydrofuran and the like.
Examples of the nitrogen-containing solvent include acetonitrile, isopropanolamine, ethylhexylamine, N-ethylmorpholine, diisopropylamine, cyclohexylamine, di-n-butylamine, tetramethylethylenediamine, and tripropylamine.
Examples of the ester solvent include ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, and γ-butyrolactone.
Examples of the ketone solvent include ethyl-n-butyl ketone, diisobutyl ketone, methyl isobutyl ketone, methyl-n-butyl ketone, cyclohexanone, 2-heptanone, and methyl ethyl ketone.

The combination of the above-mentioned polar solvent and nonpolar solvent is not particularly limited, but in particular, there is a combination using the above hydrocarbon solvent or fluorine-containing nonpolar solvent as the nonpolar solvent and the above alcohol solvent as the polar solvent. preferable.
The mass ratio of nonpolar solvent / polar solvent is generally 10/90 to 90/10, preferably 30/70 to 90/10.

  In addition, you may use a single solvent, without using a mixed solvent, In this case, a C4-C12 alcohol solvent is preferable, and what was illustrated as said alcohol solvent as a specific example. Can be mentioned.

[3] Surfactant The protective film-forming composition of the present invention can further contain a surfactant. As the surfactant, any one of fluorine-based and / or silicon-based surfactant (fluorine-based surfactant, silicon-based surfactant, surfactant having both fluorine atom and silicon atom), or two or more kinds thereof It is more preferable to contain. By containing the surfactant, the occurrence of striation is suppressed, and the coating uniformity is improved.

  Examples of the fluorine-based and / or silicon-based surfactant include, for example, JP-A No. 62-36663, JP-A No. 61-226746, JP-A No. 61-226745, JP-A No. 62-170950, JP 63-34540 A, JP 7-230165 A, JP 8-62834 A, JP 9-54432 A, JP 9-5988 A, JP 2002-277862 A, US Patent Nos. 5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511, 5,824,451 Surfactant can be mentioned, The following commercially available surfactant can also be used as it is.

Examples of commercially available surfactants that can be used include F-top EF301, EF303 (manufactured by Shin-Akita Kasei Co., Ltd.), Florard FC430, 431 (manufactured by Sumitomo 3M Co., Ltd.), MegaFuck F171, F173, F176, F189, R08 (Dainippon Ink Chemical Co., Ltd.), Surflon S-382, SC101, 102, 103, 104, 105, 106 (Asahi Glass Co., Ltd.), Troisol S-366 (Troy Chemical Co., Ltd.), etc. Fluorine type surfactant or silicon type surfactant can be mentioned. Polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used as a silicon-based surfactant.

In addition to the known surfactants described above, the surfactant is derived from a fluoroaliphatic compound produced by a telomerization method (also called telomer method) or an oligomerization method (also called oligomer method). A surfactant using a polymer having a fluoroaliphatic group can be used. The fluoroaliphatic compound can be synthesized by the method described in JP-A-2002-90991.
As the polymer having a fluoroaliphatic group, a copolymer of a monomer having a fluoroaliphatic group and (poly (oxyalkylene)) acrylate and / or (poly (oxyalkylene)) methacrylate is preferable and distributed irregularly. Or may be block copolymerized. Examples of the poly (oxyalkylene) group include a poly (oxyethylene) group, a poly (oxypropylene) group, a poly (oxybutylene) group, and the like, and a poly (oxyethylene, oxypropylene, and oxyethylene group). A unit having different chain lengths in the same chain length, such as a block link) or poly (block link of oxyethylene and oxypropylene) may be used. Furthermore, a copolymer of a monomer having a fluoroaliphatic group and (poly (oxyalkylene)) acrylate (or methacrylate) is not only a binary copolymer but also a monomer having two or more different fluoroaliphatic groups, Further, it may be a ternary or higher copolymer obtained by simultaneously copolymerizing two or more different (poly (oxyalkylene)) acrylates (or methacrylates).

Examples of commercially available surfactants include Megafac F178, F-470, F-473, F-475, F-476, and F-472 (Dainippon Ink Chemical Co., Ltd.). Further, a copolymer of an acrylate (or methacrylate) having a C ₆ F ₁₃ group and (poly (oxyalkylene)) acrylate (or methacrylate), an acrylate (or methacrylate) having a C ₆ F ₁₃ group and (poly (oxy) (Ethylene)) acrylate (or methacrylate) and (poly (oxypropylene)) acrylate (or methacrylate) copolymer, acrylate (or methacrylate) and (poly (oxyalkylene)) acrylate having C ₈ F ₁₇ groups (or Copolymer of acrylate (or methacrylate), (poly (oxyethylene)) acrylate (or methacrylate), and (poly (oxypropylene)) acrylate (or methacrylate) having a C ₈ F ₁₇ group List union It can be.

  In the present invention, other surfactants other than fluorine-based and / or silicon-based surfactants can also be used. Specifically, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene alkyl ethers such as polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether, etc. Sorbitans such as polyoxyethylene alkyl allyl ethers, polyoxyethylene / polyoxypropylene block copolymers, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, sorbitan tristearate Fatty acid esters, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopal Te - DOO, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, may be mentioned polyoxyethylene sorbitan tristearate nonionic surfactants of polyoxyethylene sorbitan fatty acid esters such as such.

  These surfactants may be used alone or in several combinations.

The amount of the surfactant used is preferably 0.0001 to 2% by mass, more preferably 0.001 to 1% by mass, based on the total amount (excluding the solvent) of the protective film forming composition for immersion exposure. .
In the protective film forming composition for immersion exposure according to the present invention, the concentration of the total solids such as the resin and the surfactant is preferably 1 to 5% by mass.

[4] Protective film The protective film-forming composition for immersion exposure according to the present invention forms a protective film by, for example, being applied onto a resist film, and the immersion liquid penetrates into the resist film. It prevents elution of components into the immersion liquid. The means for coating is appropriately set according to the process to be applied, and is not particularly limited, and means such as spin coating can be used.

The protective film is preferably a thin film from the viewpoint that it is preferably transparent to the exposure light source, and is usually formed with a thickness of 1 nm to 300 nm, preferably 10 nm to 150 nm. It is preferable that the exposure light transmittance of the film is 50% to 80%, more preferably 60% to 70%. The exposure light transmittance can be adjusted by adjusting the polymerization component of the resin. For example, the transmittance of ArF light can be increased by reducing the amount of aromatic rings contained in the resin.
Further, in order to prevent the immersion liquid and the lens from being contaminated by the eluate from the protective film, it is preferable that the elution amount from the protective film is small.

From the viewpoint of affinity with the immersion liquid, the protective film preferably has a contact angle (23 ° C.) of the immersion liquid to the protective film of 50 to 80 degrees, more preferably 60 to 80 degrees. preferable. The contact angle can be adjusted to the above range by adjusting the amount of acid groups or controlling the hydrophilicity / hydrophobicity of the copolymer component.
The refractive index of the protective film is preferably close to the refractive index of the resist film from the viewpoint of resolution. The refractive index can be adjusted by controlling the components of the protective film forming composition, particularly the resin composition and the ratio of repeating units.
The protective film-forming composition is preferably one that can be applied uniformly when forming the protective film. The applicability (coating uniformity) can be improved by appropriately selecting the type of solvent, surfactant, etc. and other additives and adjusting the amount of addition.

  Moreover, it is preferable that the formed resist pattern does not have electroconductivity, but similarly, it is preferable that the protective composition for immersion exposure does not contain a metal. The amount of metal contained in the protective film-forming composition is preferably 100 ppb or less, more preferably 50 ppb or less. The amount of metal can be suppressed by usual purification such as improvement of the purity of the material used or filtration.

  Since the protective film forming composition for immersion exposure is applied onto a resist film to form a film, the composition is preferably not mixed with the resist film at the interface.

  The protective film preferably has a dissolution rate in an alkaline developer of greater than 300 nm / second, more preferably greater than 300 nm / second and 10000 nm / second or less. The dissolution rate was measured using a 2.38 mass% tetramethylammonium aqueous solution as an alkaline developer at 23 ° C. using a resist dissolution rate analyzer (RDA790) manufactured by RISOTEC JAPAN. .

[5] Pattern Forming Method The protective film forming composition for immersion exposure of the present invention is usually used by dissolving the above components in a solvent and applying the solution on a resist film on a substrate.
That is, the resist composition for immersion exposure is applied to an arbitrary thickness (usually 50 to 500 nm) by a suitable application method such as a spinner or a coater on a substrate used for manufacturing a precision integrated circuit element. At this time, it is also preferable to form a resist film after appropriately providing an antireflection film on the substrate. After application, the resist film is formed by drying by spinning or baking.
Further, similarly to the resist composition, a protective film forming composition for immersion exposure is applied onto the resist film using a spinner, a coater or the like, and dried by spinning or baking to form a protective film.
The baking temperature is preferably 60 to 100 ° C.

Next, exposure (immersion exposure) is performed through an immersion liquid through a mask for pattern formation.
Although an exposure amount can be set suitably, it is 1-100 mJ / cm < ² > normally. After exposure, preferably, spinning or / and baking is performed, development and rinsing are performed to obtain a pattern. In the present invention, the protective film dissolves and peels in the developing solution in the developing step, so that it is not necessary to provide a separate peeling step.
Baking is preferably performed after exposure, and the baking temperature is usually 30 to 300 ° C. From the viewpoint of the change in the line width of the resist pattern due to fluctuations in the holding time (PED) from exposure to development processing, the time from exposure to baking is better.
Here, the exposure light is preferably far ultraviolet rays having a wavelength of 250 nm or less, more preferably 220 nm or less. Specific examples include KrF excimer laser (248 nm), ArF excimer laser (193 nm), F ₂ excimer laser (157 nm), X-rays, and the like.

  Examples of the substrate that can be used include a normal BareSi substrate, an SOG substrate, and a substrate having an antireflection film.

As the antireflection film, an inorganic film type such as titanium, titanium dioxide, titanium nitride, chromium oxide, carbon, α-silicon, and an organic film type made of a light absorber and a polymer material can be used. The former requires equipment such as a vacuum deposition apparatus, a CVD apparatus, and a sputtering apparatus for film formation. Examples of the organic antireflection film include a condensate of a diphenylamine derivative and a formaldehyde-modified melamine resin described in JP-B-7-69611, an alkali-soluble resin, a light absorber, and maleic anhydride copolymer described in US Pat. No. 5,294,680. A reaction product of a coalescence and a diamine type light absorbing agent, a resin binder described in JP-A-6-186863 and a methylolmelamine thermal crosslinking agent, a carboxylic acid group, an epoxy group and a light-absorbing group described in JP-A-6-118656. An acrylic resin-type antireflection film in the same molecule, a composition comprising methylol melamine and a benzophenone-based light absorber described in JP-A-8-7115, and a low-molecular light absorber added to a polyvinyl alcohol resin described in JP-A-8-179509 And the like.
Further, as the organic antireflection film, DUV30 series, DUV-40 series, ARC25, AC-2, AC-3, AR19, AR20, etc., manufactured by Brewer Science can be used.

The immersion liquid used for the immersion exposure will be described below.
The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a refractive index temperature coefficient as small as possible so as to minimize distortion of the optical image projected onto the resist. In the case of an ArF excimer laser (wavelength: 193 nm), it is preferable to use water from the viewpoints of availability and ease of handling in addition to the above-described viewpoints.

When water is used as the immersion liquid, the surface tension of the water is decreased and the surface activity is increased, so that the resist layer on the wafer is not dissolved and the influence on the optical coating on the lower surface of the lens element can be ignored. An additive (liquid) may be added in a small proportion. The additive is preferably an aliphatic alcohol having a refractive index substantially equal to that of water, and specifically includes methyl alcohol, ethyl alcohol, isopropyl alcohol and the like. By adding an alcohol having a refractive index substantially equal to that of water, even if the alcohol component in water evaporates and the content concentration changes, an advantage that the change in the refractive index of the entire liquid can be made extremely small can be obtained. On the other hand, when an opaque substance or impurities whose refractive index is significantly different from that of water are mixed with respect to 193 nm light, the optical image projected on the resist is distorted. Therefore, distilled water is preferable as the water to be used. Further, pure water filtered through an ion exchange filter or the like may be used.
The electrical resistance of water is desirably 18.3 M ohm · cm or more, and the TOC (organic concentration) is desirably 20 ppb or less. Moreover, it is desirable to have deaerated.

Examples of the alkaline developer used in the development step include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia and other primary amines, ethylamine, n-propylamine and other primary amines, Secondary amines such as diethylamine and di-n-butylamine, tertiary amines such as triethylamine and methyldiethylamine, alcohol amines such as dimethylethanolamine and triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide and the like Alkaline aqueous solutions such as quaternary ammonium salts, cyclic amines such as pyrrole and pihelidine can be used.
Furthermore, alcohols and surfactants can be added in appropriate amounts to the alkaline aqueous solution.

The alkali concentration of the alkali developer is usually from 0.1 to 20% by mass.
The pH of the alkali developer is usually from 10.0 to 15.0.
As the rinsing liquid, pure water or an appropriate amount of a surfactant added to pure water can be used.

  Further, after the development process or the rinsing process, a process of removing the developer or the rinsing liquid adhering to the pattern with a supercritical fluid can be performed.

  In immersion exposure using the protective film of the present invention, the resist is not particularly limited, and can be arbitrarily selected from those usually used, and may be either positive type or negative type.

  As the resist, positive type and negative type resists having sufficient characteristics that can be applied to recent ultra-fine processing can be suitably used. In the present invention, a chemical amplification type resist, and further a positive type resist are preferably used. Can do.

  Typical examples of the chemically amplified resist include those using a so-called acid generator that generates an acid by active energy rays such as light. For example, as the negative chemically amplified resist, a three-component system of a base polymer, a photoacid generator, and a crosslinking agent is usually used. At the time of resist exposure, the acid generated by light irradiation causes a crosslinking reaction in the exposed portion, and acts to reduce the solubility in the developer. On the other hand, a positive chemically amplified resist is usually a two-component system including a base polymer having a site blocked with a protective group having a dissolution inhibiting function and a photoacid generator, a base polymer, an acid generator, There are some three-component dissolution inhibitors. Then, at the time of resist exposure, in the exposed portion, the acid generated by light irradiation acts to remove the protective group of the polymer and increase the solubility in the developer.

When the exposure light source is an ArF excimer laser (wavelength: 193 nm), a two-component system containing a resin that is solubilized in an alkaline developer by the action of an acid and a photoacid generator is preferred.
In particular, the resin that is solubilized in the alkaline developer by the action of an acid is preferably an acrylic or methacrylic resin having a monocyclic or polycyclic alicyclic hydrocarbon structure, and has a lactone residue or an adamantane residue. Is more preferable.

  In addition, since it is preferable that the formed resist pattern does not have electroconductivity, it is preferable that a resist does not contain a metal. The amount of metal contained is preferably 100 ppb or less, more preferably 50 ppb or less. The amount of metal can be suppressed by usual purification such as improvement of the purity of the material used or filtration.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, the content of this invention is not limited by this.

[Synthesis Example 1: Synthesis of Resin (1)]
120 g of 2,2,2-trifluoroethyl vinyl ether and cyclohexylmaleimide were charged at a ratio of 50/50 (molar ratio), dissolved in tetrahydrofuran, and heated and stirred at 65 ° C. in a nitrogen atmosphere. To this solution was added 3 mol% of a polymerization initiator V-65 (2,2′-azobis (2,4-dimethylvaleronitrile)) manufactured by Wako Pure Chemical Industries, Ltd., and the mixture was further stirred for 12 hours. After completion of the reaction, the reaction solution was cooled to room temperature, crystallized in 500 ml of hexane solvent, and the precipitated white powder was collected by filtration to obtain 75 g of the following resin 1.
The weight average molecular weight (Mw) in terms of standard polystyrene determined by GPC measurement was 4200, and the dispersity (Mw / Mn) was 1.5.

  Resins (2) and (3) were synthesized in the same manner as resin (1).

[Synthesis Example 2: Synthesis of Resin (4)]
Nonafluorohexyl acrylate and norbornane lactone methacrylate were charged at a ratio of 80/20 (molar ratio) and dissolved in propylene glycol monomethyl ether acetate to prepare 130 g of a solution having a solid concentration of 20% by mass.
8 mol% of Wako Pure Chemical Industries, Ltd. polymerization initiator V-601 was added to this solution, and this was dripped at 10 g of propylene glycol monomethyl ether acetate heated at 65 degreeC over 4 hours in nitrogen atmosphere. The reaction liquid was stirred for 4 hours after completion | finish of dripping. After completion of the reaction, the reaction solution was cooled to room temperature, crystallized in 1 L of hexane solvent, and the precipitated white powder was collected by filtration to obtain 40 g of the target product, Resin 5. The weight average molecular weight (Mw) in terms of standard polystyrene determined by GPC measurement was 12000, and the degree of dispersion (Mw / Mn) was 2.0.

Resins (5) to (7) were synthesized by the same method as resin (4) except that the monomer charge ratio was changed.
Comparative resin (8) was synthesized according to WO2005 / 069096A1.

[Examples 1-12 and Comparative Examples 1-3]
<Preparation of protective film forming composition>
The components shown in Table 2 below were dissolved in a solvent to prepare a solution having a solid content concentration of 1.5% by mass, and this was filtered through a polyethylene filter having a pore size of 0.1 μm to prepare a protective film forming composition.

<Image formation evaluation>
An organic antireflection film ARC29A (Nissan Chemical Co., Ltd.) was applied on a silicon wafer and baked at 205 ° C. for 60 seconds to form a 78 nm antireflection film. A resist shown in Table 2 was applied thereon, and baked at 115 ° C. for 60 seconds to form a resist film having a thickness of 200 nm. In Examples 1 to 12 and Comparative Example 3, a protective film-forming composition (solid content concentration of 4% by mass) containing the components shown in Table 2 was further applied, baked at 90 ° C. for 60 seconds, and a film thickness of 20 nm. A protective film was formed. In Comparative Examples 1 and 2, a protective film was not formed.

The wafer thus obtained was subjected to two-beam interference exposure with the apparatus of FIG. 1 using water as the immersion liquid. The laser wavelength was 193 nm. After heating at 130 ° C. for 60 seconds, development was performed with an aqueous tetramethylammonium hydroxide solution (2.38 mass%) for 60 seconds, rinsing with pure water, and spin drying to obtain a resist pattern. A prism forming a 90 nm line and space pattern was used.
The resist pattern was observed with a scanning electron microscope (S-9260 manufactured by Hitachi) to evaluate the profile.

  In the apparatus shown in FIG. 1, 1 is a laser, 2 is an aperture, 3 is a shutter, 4, 5 and 6 are reflection mirrors, 7 is a condenser lens, 8 is a prism, 9 is an immersion liquid, 10 Denotes a wafer provided with an antireflection film, a resist film and a protective film (however, in the comparative example, no protective film is provided), and 11 denotes a wafer stage.

<Water followability evaluation>
The prepared positive resist composition was applied on a silicon wafer and baked at 130 ° C. for 60 seconds to form a 160 nm resist film. Next, as shown in FIG. 1, pure water 2 was filled between the wafer 1 coated with the obtained positive resist composition and the quartz glass substrate 3.
In this state, the quartz glass substrate 3 was moved (scanned) in parallel to the surface of the resist-coated substrate 1, and the state of the pure water 2 following it was visually observed. The scanning speed of the quartz glass substrate 3 is gradually increased, and the pure water 2 cannot follow the scanning speed of the quartz glass substrate 3 to obtain the limit scanning speed (mm / second) at which water droplets start to remain on the retreat side. Follow-up was evaluated. As this limit scan speed is larger, water can follow a higher scan speed, and the water followability on the resist film is better.

The symbols in Table 2 are as follows.
〔solvent〕
SL1: Isopar G (manufactured by Kokura Kosan Co., Ltd.)
SL2: isooctane SL3: cyclohexanone SL4: isopropanol SL5: 2-methyl-1-propanol [surfactant]
W-1: MegaFuck F176 (Dainippon Ink Chemical Co., Ltd.) (Fluorine)
W-2: Megafuck R08 (Dainippon Ink Chemical Co., Ltd.) (fluorine and silicon)

[Resist]
PR1: Resist composition described in Example 1 of JP-A-2000-275845, that is, 10 parts by mass of the following resin P-1 (weight average molecular weight of about 10,000), acid generator (triphenylsulfonium perfluorobutanesulfonate) (TPS-109 manufactured by Midori Chemical Co., Ltd.) 0.2 parts by mass, 0.015 parts by mass of basic compound (2,6-diisopropylaniline), solvent (47.5 parts by mass of propylene glycol monomethyl ether acetate and γ-butyrolactone 2 0.5 parts by mass) of a resist composition.

  PR2: Resist composition described in Example 1 of JP-A No. 2003-167347, that is, 100 parts by mass of the following resin P-2 (weight average molecular weight 10,000), acid generator component (triphenylsulfonimnonafluorobutanesulfonate) ) A resist composition containing 2 parts by mass, 0.2 parts by mass of a basic compound (triethanolamine), and an organic solvent (750 parts by mass of propylene glycol monomethyl ether acetate / 30 parts by mass of γ-butyrolactone).

PR3: Resist composition described in Example 1 of JP-A No. 2002-12622, that is, 80 parts by mass of the following resin P-3 (weight average molecular weight: 12200), 1 part by mass of an acid generator (PAG1), a basic compound (tri A resist composition containing 0.078 parts by mass of butylamine) and 480 parts by mass of a solvent (PGMEA: propylene glycol monomethyl ether acetate).

  PR4: Resist composition described in Example 1 of JP-A-2003-177538, that is, 2 g of the following resin P-4 (weight average molecular weight 10600), 38 mg of acid generator (PAG2), basic compound (1,5 -Diazabicyclo [4.3.0] -5-nonene (DBN)) 4 mg, surfactant (Megafac F176 (manufactured by Dainippon Ink and Chemicals)), solvent (propylene glycol monomethyl ether acetate (PGMEA)) / Ethyl lactate = 70/30, solid content concentration of 14% by mass).

  As shown in Table 2, the protective film-forming composition of the present invention has sufficient water insolubility as a protective film and has sufficient solubility in an alkaline developer. Further, as shown in Table 2, the presence of the protective film protects the resist film during the immersion exposure, thereby obtaining a pattern.

  The protective film forming composition used in Example 9 was evaluated in the same manner as in Example 9 using 1.2 g of resin, 18.8 g of solvent and a solid concentration of 6% by mass, and using PR1 as a resist. Profile is slightly tapered.

  Moreover, in Example 9, when the heating after application | coating of a protective film formation composition was performed at 120 degreeC, and the protective film was formed and evaluated, a part of pattern fell.

  As described above, the protective film forming composition of the present invention allows immersion of the immersion liquid into the resist film and the immersion liquid of the resist film component without complicating the process steps during immersion exposure. It can be seen that the desired fine pattern can be obtained.

It is the schematic of a two-beam interference exposure experiment apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser 2 Aperture 3 Shutter 4, 5, 6 Reflection mirror 7 Condensing lens 8 Prism 9 Immersion liquid 10 Wafer provided with antireflection film, resist film, protective film 11 Wafer stage

Claims (6)

A protective film forming composition for forming a protective film provided on a resist film,
(A) A group that is decomposed by the action of an alkali developer and generates an alkali-soluble group by repeating the unit (x) containing at least one fluorine atom having a group represented by the following general formula (F2) or (F3) A fluorine-containing atom resin having a repeating unit (y) having a group containing a group that decomposes by the action of an alkali developer and generates an alkali-soluble group, and
(S) As a solvent, an alcohol solvent alone, or a nonpolar solvent selected from a hydrocarbon solvent, a halogenated hydrocarbon solvent, and a fluorine-containing solvent, an alcohol solvent, an ether solvent, a nitrogen-containing solvent, and an ester solvent And a mixed solvent with a polar solvent selected from ketone-based solvents .

In general formulas (F2) and (F3),
R _{57 to} R ₆₁ each independently represents a hydrogen atom, a fluorine atom or an alkyl group. However, at least one of R _{57 to} R ₆₁ represents a fluorine atom or an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom.
R ₆₂ to R ₆₄ each independently represent a hydrogen atom, a fluorine atom or an alkyl group. However, at least one of R _{62 to} R ₆₄ represents an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom. R ₆₂ and R ₆₃ may be connected to each other to form a ring. The protective film forming composition according to claim 1 , wherein the solvent (S) contains any one of an aliphatic hydrocarbon solvent and a fluorine solvent as the nonpolar solvent .   The protective film-forming composition according to claim 1 or 2, wherein the group that decomposes by the action of an alkali developer and generates an alkali-soluble group is a group having a lactone structure. The protective film forming composition according to claim 3, wherein the lactone structure is a structure represented by the following general formula LC1-4.

Rb ₂ Represents a substituent and n ₂ Represents the number of substituents equal to or greater than 0, and there are a plurality of Rb ₂ May be the same or different, and a plurality of Rb ₂ They may combine to form a ring. A resist film is formed, a protective film is formed on the resist film with the protective film-forming composition according to any one of claims 1 to 4 to form a laminate, and the laminate is subjected to immersion exposure and developed. The pattern formation method characterized by the above-mentioned.   The pattern forming method according to claim 5, wherein immersion exposure is performed through pure water as the immersion liquid.