JP2008078308A - Method for forming photoresist pattern, material for forming protective film used therefor, and liquid for cleaning and removing protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a high-resolution photoresist pattern, wherein mixing thereof with the photoresist film is less apt to occur, using a protective film giving less influence on the environment and having high water repellency. <P>SOLUTION: This method for forming a photoresist pattern that uses an oil immersion exposure process comprises a step of (1) providing a photoresist film on a substrate, (2) forming a protective film on the photoresist film by using a protective film forming material, (3) selectively exposing the photoresist film via a liquid for oil immersion exposure and the protective film, by arranging the liquid for the oil immersion exposure on at least the protective film on the substrate, (4) removing the protective film by using a protective film cleaning and a removal liquid containing a polar organic solvent, and (5) developing the photoresist film by using alkali developer. The material for forming the protective film and the protective film cleaning and removal liquid to be used in this method for forming the photoresist pattern are also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a photoresist pattern, a material for forming a protective film used for forming the photoresist pattern, and a protective film cleaning and removing liquid used for the method for forming the photoresist pattern.

  In recent years, an immersion exposure process has been reported as a new lithography technique (see Non-Patent Documents 1 to 3). This immersion exposure process replaces the conventional exposure optical path space with an immersion exposure liquid (for example, pure water or a fluorine-based inert liquid), so that even if a light source with the same exposure wavelength is used, the exposure light path is higher. It is possible to realize formation of a photoresist pattern that is excellent in resolution and depth of focus (see Patent Documents 1 to 3).

  In addition, by using a photoresist protective film that uses a resin that can only be dissolved in a specific solvent, a technique aimed at simultaneously preventing deterioration of the photoresist film due to immersion exposure liquid and refractive index fluctuation has been proposed. (See Patent Document 2).

More recently, from the viewpoints of simplifying the resist pattern formation process and improving production efficiency, the use of an alkali-soluble protective film removes the resist protective film and resist pattern during alkali development after immersion exposure. There has been proposed a technique for simultaneously forming (see Patent Document 3).
"Journal of Vacuum Science & Technology B", (USA), 1999, Vol. 17, No. 6, pp. 3306-3309 "Journal of Vacuum Science & Technology B", (USA), 2001, Vol. 19, No. 6, pp. 2353-2356 “Proceedings of SPIE” (USA), 2002, 4691, pages 459-465. International Publication No. 2004/068242 Pamphlet International Publication No. 2004/074937 Pamphlet JP 2005-264131 A

  However, the protective film described in Patent Document 2 requires a fluorine-based special solvent. This fluorine-based special solvent has a problem that it has a large influence on the environment, such as a high global warming potential.

  Further, the protective film described in Patent Document 3 may cause mixing with the underlying photoresist film, and there is a problem in forming a photoresist pattern having a desired resolution.

  In view of the above problems, in the present invention, there is provided a photoresist pattern that can form a high-resolution photoresist pattern that has little influence on the environment and is less likely to be mixed with a photoresist film using a protective film having high water repellency. An object is to provide a method of forming. Another object of the present invention is to provide a protective film forming material for forming the protective film, and a protective film cleaning and removing liquid.

  By removing the protective film using a polar organic solvent, the present inventors can prevent mixing of the protective film and the photoresist film, so that a photoresist pattern having higher resolution than before can be obtained. It has been found that it can be formed, and the present invention has been completed.

The present invention is a method of forming a photoresist pattern using an immersion exposure process,
(1) providing a photoresist film on the substrate;
(2) forming a protective film on the photoresist film using a protective film forming material;
(3) disposing an immersion exposure liquid on at least the protective film of the substrate, and selectively exposing the photoresist film through the immersion exposure liquid and the protective film;
(4) removing the protective film using a protective film cleaning solution containing a polar organic solvent;
(5) a step of developing the photoresist film using an alkali developer;
A method of forming a photoresist pattern having

  The present invention also provides a protective film forming material and a protective film cleaning and removing liquid used in the above method for forming a photoresist pattern.

  According to the present invention, it is possible to form a photoresist pattern capable of forming a high-resolution photoresist pattern by using a protective film having a small impact on the environment and having a high water repellency, which hardly causes mixing with a photoresist film. It becomes possible.

[Method for forming photoresist pattern]
The method for forming a photoresist pattern according to the present invention includes:
(1) a step of providing a photoresist film on a substrate (hereinafter also referred to as step (1));
(2) forming a protective film on the photoresist film using the protective film forming material (hereinafter also referred to as process (2));
(3) A step of disposing an immersion exposure liquid on at least the protective film of the substrate, and selectively exposing the photoresist film through the immersion exposure liquid and the protective film (hereinafter referred to as a step 3))
(4) a step of removing the protective film using a protective film cleaning solution containing a polar organic solvent (hereinafter also referred to as step (4));
(5) A step of developing the photoresist film using an alkali developer (hereinafter also referred to as step (5)).

  Step (1) is a step of providing a photoresist film on the substrate. Specifically, a known photoresist composition is applied to a substrate such as a silicon wafer using a known method such as a spinner, and then pre-baked (PAB treatment) to form a photoresist film. Note that a photoresist film may be formed after providing one layer of an organic or inorganic antireflection film (lower antireflection film) on the substrate.

  Step (2) is a step of forming a protective film on the photoresist film. Specifically, the protective film-forming material prepared at a predetermined concentration is uniformly applied to the surface of the photoresist film formed in the step (1) by the same method as in the step (1), and baked. Then, a protective film is formed by curing.

  In the step (3), an immersion exposure medium is disposed on the protective film, and in this state, the photoresist film and the protective film on the substrate are selectively exposed through a mask pattern. The exposure light passes through the immersion exposure liquid and the protective film and reaches the photoresist film.

  At this time, since the photoresist film is shielded from the immersion exposure liquid by the protective film, the photoresist film is affected by the invasion of the immersion exposure liquid and is subject to alteration such as swelling, or conversely in the immersion exposure liquid. It is prevented that the optical properties such as the refractive index of the immersion exposure liquid itself are altered by elution of the components.

  The exposure light is not particularly limited as in the dry exposure process, and can be performed using radiation such as an ArF excimer laser, a KrF excimer laser, or VUV (vacuum ultraviolet).

The immersion exposure liquid is not particularly limited as long as it has a refractive index larger than that of air and smaller than that of the photoresist film used. Examples of such immersion exposure liquids include water (pure water, deionized water), fluorine-based inert liquids, etc., but immersion exposure liquids having high refractive index characteristics that are expected to be developed in the near future. Can also be used. Specific examples of the fluorine-based inert liquid include a fluorine-based compound such as C ₃ HCl ₂ F ₅ , C ₄ F ₉ OCH ₃ , C ₄ F ₉ OC ₂ H ₅ , and C ₅ H ₃ F ₇ as a main component. Liquid. Of these, water (pure water, deionized water) is preferably used from the viewpoints of cost, safety, environmental problems, and versatility.
When the exposure process in the immersion state is completed, the substrate is taken out from the immersion exposure liquid and the liquid is removed from the substrate.

  In step (4), heat treatment is performed as necessary with the protective film laminated on the photoresist film after the exposure through step (3) above, and the protective film is removed using a protective film washing and removing solution. It is a process to do.

  Since the material for forming a protective film according to the present invention contains an alkali-soluble polymer, the formed protective film is soluble in an alkali developer. However, by separately providing a step of removing the protective film using a polar organic solvent, it is possible to prevent the residue on the photoresist film, which has been a problem with the conventional protective film. Moreover, even when a mixing layer is formed between the protective film and the photoresist film, it is possible to eliminate the adverse effect of the mixing layer on the resist pattern by using the protective film cleaning solution. Become.

  Step (5) is a step of developing the photoresist film using an alkali developer. As the alkaline developer, a known developer can be appropriately selected and used. Since the protective film has been removed in the above step (4), it is the photoresist film that is removed by this developer. Further, post-baking may be performed following the development processing.

  Subsequently, rinsing is performed using pure water or the like. In this water rinse, for example, water is dropped or sprayed on the surface of the substrate while rotating the substrate to wash away the developer on the substrate and the protective film component and the photoresist composition dissolved by the developer. Then, by drying, a photoresist pattern in which the photoresist film is patterned into a shape corresponding to the mask pattern is obtained.

  As described above, in the present invention, the protective film can be completely removed by providing the step of removing the protective film (step (4)) separately from the developing step (step (5)). Further, the mixing layer formed between the protective film and the photoresist film can be completely removed by the step (4). In addition, since the protective film formed of the protective film forming material of the present invention has high water repellency, the liquid for immersion exposure after the completion of exposure is well separated, and the amount of adhesion of the liquid for immersion exposure is small. Liquid leakage for so-called immersion exposure is also reduced.

[Material for protective film formation]
The protective film-forming material according to the present invention contains (a) an alkali-soluble polymer (hereinafter also referred to as component (a)) and (b) a polar organic solvent (hereinafter also referred to as component (b)).

上記一般式（Ａ−１）中、Ｒ_１は、炭素数１から６のアルキレン鎖（以下、アルキレン基ともいう）又はフルオロアルキレン鎖（以下、フルオロアルキレン基ともいう）であり、Ｒ_２はそれぞれ独立して水素原子、炭素数１から６の直鎖状、分岐状、又は環状のアルキル基又はフルオロアルキル基であり、Ｚは炭素数１から２のアルキレン基又は酸素原子であり、ｎは０から３である。 [(A) Alkali-soluble polymer]
Specific examples of the alkali-soluble polymer (a) include the following embodiments. First, as a 1st aspect, it is preferable that it is a polymer which has a monomer unit represented by the following general formula (A-1) as a structural unit at least.

In the general formula (A-1), R ₁ is an alkylene chain having 1 to 6 carbon atoms (hereinafter also referred to as an alkylene group) or a fluoroalkylene chain (hereinafter also referred to as a fluoroalkylene group), and R ₂ is respectively Independently a hydrogen atom, a linear, branched or cyclic alkyl group or fluoroalkyl group having 1 to 6 carbon atoms, Z is an alkylene group having 1 to 2 carbon atoms or an oxygen atom, and n is 0 To 3.

In particular, R ₁ is specifically a linear alkylene group such as a methylene group, n-ethylene group, n-propylene group, n-butylene group, n-pentylene group, 1-methylethylene group, 1-methyl group. Examples include branched alkylene groups such as a propylene group and a 2-methylpropylene group. Some or all of the hydrogen atoms of these alkylene groups may be substituted with fluorine atoms. Of these, a methylene group is more preferred.

Specific examples of R ₂ include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, an undecafluoropropyl group, and a heptadecafluorooctyl group. Some or all of the hydrogen atoms of these substituents may be substituted with fluorine atoms. Among these, from the viewpoint of improving hydrophobicity, a perfluoroalkyl group in which all of the hydrogen atoms of the substituent are substituted with fluorine atoms is preferable, and a trifluoromethyl group is particularly preferable.
Further, in the general formula (A-1), Z is preferably a methylene group, and n is preferably 0.

Moreover, at least selected from the structural unit represented by the general formula (A-1) and the monomer units represented by the following general formulas (A-2), (A-3), and (A-4) The copolymer which has 1 type and a structural unit may be sufficient.

In the general formulas (A-2), (A-3), and (A-4), R ₃ , R ₅ , and R ₇ are each an alkylene group or fluoroalkylene group having 0 to 6 carbon atoms, R ₄ , R ₆ , and R ₈ are each a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 15 carbon atoms (provided that part of the alkyl group may be via an ether bond, Furthermore, part of the hydrogen atom or fluorine atom of the alkyl group may be substituted with a hydroxyl group), and R ₂ , Z, and n have the same meanings as in the general formula (A-1).

The monomer units represented by the general formulas (A-2), (A-3), and (A-4) are further represented by the following general formulas (A-5), (A-6), and ( A monomer unit represented by A-7) is preferred.

In the general formulas (A-5), (A-6), and (A-7), R ₉ is not present or is a methylene group, and R ₁₀ is independently a methyl group or trifluoro A methyl group, R ₁₁ is a linear or branched alkyl group or fluoroalkyl group having 2 to 10 carbon atoms, and R ₁₂ is a linear or branched alkyl group having 5 to 10 carbon atoms or A fluoroalkyl group (provided that a part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group may be substituted with a hydroxyl group), and R ₂ , Z and n are the above general formula (A-1) It is synonymous with.
Among them, R ₁₁ is preferably —CH ₂ C ₂ F ₅ or —C (CH ₃ ) CH ₂ C (CF ₃ ) ₂ OH, and R ₁₂ is —C ₇ F ₁₅ , —CF ₂ CF ( _{CF 3) CF 2 CF 2 CF} 2 CF (CF 3) 2, or _{-CF 2 CF (CF 3) CF} 2 C (CF 3) is preferably _3.

A protective film having basic characteristics required for a protective film, particularly when applied to an immersion exposure process, by incorporating a monomer unit having a sulfonamide group represented by the general formula (A-1) in the side chain. Can be formed.
Here, the basic characteristics required for the protective film are high resistance to the immersion medium, low compatibility with the resist film provided in the lower layer, and elution of components from the immersion medium to the resist film. In addition, it is possible to prevent elution of components from the resist film to the immersion exposure liquid, and to suppress gas permeation of the protective film. Furthermore, water repellency is further improved by incorporating at least one structural unit selected from the monomer units represented by the general formulas (A-2), (A-3), and (A-4). It can be set as the made protective film.

  Moreover, when using these as a copolymer, it represents with the monomer unit represented by the said general formula (A-1), and the said general formula (A-2), (A-3), and (A-4). The constitutional ratio (molar ratio) with at least one selected from monomer units is preferably 60:40 to 99: 1.

  (A) As a second aspect of the alkali-soluble polymer, a polymer having an alkali-soluble constituent unit composed of an aliphatic cyclic compound having both a fluorine atom or a fluoroalkyl group and an alcoholic hydroxyl group or an oxyalkyl group. Can be used.

  That is, the fluorine atom or fluoroalkyl group and the alcoholic hydroxyl group or alkyloxy group of the structural unit are each bonded to an aliphatic cyclic compound, and the aliphatic ring constitutes the main chain.

  Specific examples of the fluorine atom or fluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, and the like. A methyl group is preferred. Specific examples of the alcoholic hydroxyl group or alkyloxy group include an alcoholic hydroxyl group, a linear, branched, or cyclic alkyloxyalkyl group having 1 to 15 carbon atoms, or an alkyloxy group.

  Specific examples of the alkyloxy group having 1 to 15 carbon atoms include a methyloxy group, an ethyloxy group, a propyloxy group, and a butyloxy group. Examples of the alkyloxyalkyl group having 1 to 15 carbon atoms include methyloxy group Examples thereof include a methyl group, an ethyloxymethyl group, a propyloxymethyl group, and a butyloxymethyl group.

The polymer having such a structural unit is formed by cyclopolymerization of a diene compound having a hydroxyl group and a fluorine atom. The diene compound is preferably heptadiene, which is excellent in transparency and dry etching resistance and easily forms a polymer having a 5-membered ring or a 6-membered ring. In particular, 1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-heptadiene _{(CF 2 = CFCF 2 C (} CF 3) (OH) CH 2 CH = CH 2 It is most preferable in the industry to be a polymer formed by cyclopolymerization of

Below, the structure of the said polymer is shown concretely.

In general formula (A-8), each R ₁₃ independently represents a hydrogen atom, a linear, branched, or cyclic alkyloxy group having 1 to 15 carbon atoms or an alkyloxyalkyl group, and l, m Are from 10 mol% to 90 mol%, respectively.

  (A) As a 3rd aspect of an alkali-soluble polymer, the polymer which has a structural unit represented by general formula (A-9) and (A-10) can be used.

In the above general formulas (A-9) and (A-10), R ₁₄ is each independently a linear, branched or cyclic alkyl group having 1 to 5 carbon atoms or a fluoroalkyl group, and R ₁₅ is Each independently a hydrogen atom, a fluorine atom, or a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms or a fluoroalkyl group, and at least one of these R ₁₄ and R ₁₅ is a fluorine atom. R ₁₆ is a hydrogen atom or a methyl group, and p is a repeating unit.

Furthermore, as the structural units represented by the general formulas (A-9) and (A-10), more specifically, the structures represented by the following structural formulas (A-11) and (A-12), respectively. Units can be preferably used.

  Furthermore, each structural unit represented by the above (A-9) and (A-10) may be a copolymer and / or a mixed polymer with a structural unit represented by the following general formula (A-13). . By using such a copolymer and / or mixed polymer, alkali solubility can be further improved.

In the general formula (A-13), R ₁₇ is a hydrogen atom, or a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms or a fluoroalkyl group, and p is a general formula (A- It is a repeating unit as in 9) and (A-10).

  (A) As a 4th aspect of an alkali-soluble polymer, the polymer which has a structural unit represented by general formula (A-14) can be used.

In the formula _{(A-14), C} A is a methylene group or a fluoroalkyl methylene _{group, R 18} represents a linear, fluoroalkyl group having 1 to 5 carbon atoms, branched or cyclic, q is 0 And p is a repeating unit as in the general formulas (A-9) and (A-10).
Note that in the general formula (A-14), part or all of the hydrogen atoms substituting for the carbon atoms constituting the ring skeleton may be substituted with fluorine atoms.

As the structural unit represented by the general formula (A-14), specifically, a structural unit represented by the following structural formula (A-15) is particularly preferably used.

  (A) As a 5th aspect of an alkali-soluble polymer, the polymer which has a structural unit represented by general formula (A-16) can be used.

上記一般式（Ａ−１６）中、Ｒ_１９は水素原子又はメチル基を示し、Ｒ_２０は炭素数１から５のアルキレン基を示し、Ｒ_２１は水素原子の一部又は全部がフッ素原子に置換された炭素数１から１０のフルオロアルキレン基であり、ｐは一般式（Ａ−９）及び（Ａ−１０）と同様に繰り返し単位である。

In the general formula (A-16), R ₁₉ represents a hydrogen atom or a methyl group, R ₂₀ represents an alkylene group having 1 to 5 carbon atoms, and R ₂₁ represents a part or all of the hydrogen atoms substituted by fluorine atoms. And is a repeating unit as in the general formulas (A-9) and (A-10).

  Specifically, as the structural unit represented by the general formula (A-16), one having a structure represented by the following structural formulas (A-17) and (A-18) is preferably used.

  Furthermore, as a sixth aspect of (a) the alkali-soluble polymer, a polymer having a structural unit represented by General Formula (A-19) can be used.

In the above general formula (A-19), C _A is a methylene group or a fluoromethylene group, and R ₂₂ is a linear, branched or cyclic carbon in which part or all of the hydrogen atoms are substituted with fluorine atoms. A fluoroalkyl group having 1 to 5 carbon atoms, wherein R ₂₃ is a hydrogen atom, or a linear, branched, or cyclic fluoroalkyl group having 1 to 5 carbon atoms in which part or all of the hydrogen atoms are substituted with fluorine atoms Is a group, q is 0 to 3, and p is a repeating unit as in the general formulas (A-9) and (A-10).
Note that in the general formula (A-19), part or all of the hydrogen atoms substituting for the carbon atoms constituting the ring skeleton may be substituted with fluorine atoms.

As the structural unit represented by the general formula (A-19), specifically, a structural unit represented by the following structural formula (A-20) is preferably used.

  In the present invention, the component (a) described above may be a copolymer or a mixed polymer obtained by copolymerization or mixing with any other monomer unit as long as the effects of the present invention are not impaired.

  Such component (a) can be synthesized by a known method. The polystyrene-reduced mass average molecular weight (Mw) by GPC of this polymer is not particularly limited, but is 2000 to 80000, and more preferably 3000 to 50000.

  Furthermore, the blending amount of the component (a) is preferably about 0.1% by mass to 20% by mass, and preferably 0.3% by mass to 10% by mass with respect to the total amount of the protective film forming composition. It is more preferable.

[(B) Polar organic solvent]
The (b) polar organic solvent is not particularly limited as long as it is an organic solvent capable of dissolving the component (a).

  Examples of such polar organic solvents include (b-1) alkyl alcohols, (b-2) fluoroalkyl alcohols in which some or all of the hydrogen atoms are substituted with fluorine atoms, and (b-3) alkyl ethers. (B-4) Fluoroalkyl ethers and fluoroalkyl esters in which part or all of the hydrogen atoms are substituted with fluorine atoms.

  The (b-1) alkyl alcohols preferably have 1 to 10 carbon atoms. Specifically, at least one selected from ethanol, propanol, n-butanol, isobutanol, n-pentanol, 4-methyl-2-pentanol, and 2-octanol can be used. Among these, it is preferable to use at least one selected from isobutanol and 4-methyl-2-pentanol.

The (b-2) fluoroalkyl alcohols in which some or all of the hydrogen atoms are substituted with fluorine atoms preferably have 4 to 12 carbon atoms. Specifically, at least one of C ₄ F ₉ CH ₂ CH ₂ OH and C ₃ F ₇ CH ₂ OH can be used.

  The (b-3) alkyl ethers preferably have 2 to 10 carbon atoms, and more preferably 3 to 8. As such alkyl ethers, specifically, at least one selected from dimethyl ether, diethyl ether, methyl ethyl ether, dipropyl ether, diisopropyl ether, and dibutyl ether can be used. Among these, it is preferable to use at least one of diisopropyl ether and dibutyl ether.

  As the (b-4) fluoroalkyl ethers and fluoroalkyl esters in which part or all of the hydrogen atoms are substituted with fluorine atoms, those having 3 to 15 carbon atoms are preferably used.

In the fluoroalkyl ethers, R _A OR _B (R _A and R _B are each independently an alkyl group, the total number of carbon atoms of both alkyl groups is 3 to 15, and at least a part of the hydrogen atoms or It is possible to use at least one selected from fluoroalkyl ethers represented by the formula (all of which are substituted with fluorine atoms).

In the fluoroalkyl esters, R _D COOR _E (R _D and R _E are each independently an alkyl group, the total number of carbon atoms of both alkyl groups is 3 to 15, and at least a part of the hydrogen atoms or It is possible to use at least one selected from fluoroalkyl esters represented by the formula (all of which are substituted with fluorine atoms).

Preferable examples of the fluoroalkyl ether include compounds represented by the following structural formula (B-1). In addition, preferred examples of the fluoroalkyl ester include compounds represented by the following structural formulas (B-2) and (B-3). However, it is not limited to these.

  These polar organic solvents can be used alone or in combination of two or more as required. Furthermore, it can be used in combination with a paraffinic solvent such as n-heptane and a fluorine solvent such as fluoro-2-butyltetrahydrofuran as long as the effects of the present invention are not impaired.

  The blending amount of the component (b) is preferably adjusted so that the protective film forming material becomes a solution having a concentration of 0.1% by mass to 20% by mass, particularly 0.3% by mass to 5% by mass. It is preferable to adjust so.

[(C) Crosslinking agent]
The composition for forming a resist protective film according to the present invention may contain (c) a crosslinking agent, if necessary, in addition to the components (a) and (b). The crosslinking agent includes a nitrogen-containing compound having an amino group in which a hydrogen atom is substituted with at least one substituent selected from a hydroxyalkyl group and an alkoxyalkyl group, and a hydrogen atom in a hydroxyalkyl group and an alkoxyalkyl group. It is possible to use at least one nitrogen-containing compound selected from nitrogen-containing compounds having an imino group substituted with at least one substituent selected from:
Examples of these nitrogen-containing compounds include melamine derivatives, urea derivatives, guanamine derivatives, acetoguanamine derivatives, benzoguanamine derivatives, wherein a hydrogen atom of an amino group is substituted with a methylol group or an alkoxymethyl group or both. Examples include succinylamide derivatives, glycoluril derivatives in which a hydrogen atom of an imino group is substituted, and ethylene urea derivatives.

  These nitrogen-containing compounds are obtained by, for example, reacting the above-mentioned nitrogen-containing compounds with formalin in boiling water to form methylol, or further to this, lower alcohols, specifically methanol, ethanol, n-propanol, isopropanol, It can be obtained by reacting with n-butanol, isobutanol or the like to be alkoxylated. Among them, a preferred cross-linking agent is tetrabutoxymethylated glycoluril.

  Furthermore, as a crosslinking agent, a condensation reaction product of a hydrocarbon compound substituted with at least one substituent selected from a hydroxyl group and an alkyloxy group and a monohydroxymonocarboxylic acid compound can also be suitably used. As the monohydroxymonocarboxylic acid, those in which a hydroxyl group and a carboxyl group are bonded to the same carbon atom or two adjacent carbon atoms are preferable.

  When such a crosslinking agent is blended, the blending amount is preferably about 0.5 to 10% by weight with respect to the blending amount of the alkali-soluble polymer of component (a).

[(D) acidic compound]
The material for forming a resist protective film according to the present invention may further contain (d) an acidic compound as necessary. By adding this acidic compound, the effect of improving the shape of the resist pattern was obtained. Furthermore, after immersion exposure, the resist film was exposed to an atmosphere containing a small amount of amine before development. Even (reservation after exposure), the adverse effect of the amine can be effectively suppressed by the intervention of the protective film. As a result, it is possible to prevent a large deviation in the dimensions of the photoresist pattern obtained by subsequent development.

  Examples of such acidic compounds include at least one selected from the following general formulas (D-1), (D-2), (D-3), and (D-4).

上記式（Ｄ−１）〜（Ｄ−４）中、ｓは１から５の整数であり、ｔは１０から１５の整数であり、ｕは２から３の整数であり、ｖはそれぞれ２から３の整数であり、Ｒ_２３及びＲ_２４は炭素原子数１から１５のアルキル基又はフルオロアルキル基（水素原子又はフッ素原子の一部は、水酸基、アルコキシ基、カルボキシル基、アミノ基により置換されていてもよい）である。

In the above formulas (D-1) to (D-4), s is an integer from 1 to 5, t is an integer from 10 to 15, u is an integer from 2 to 3, and v is from 2 respectively. R ₂₃ and R ₂₄ are each an alkyl group or a fluoroalkyl group having 1 to 15 carbon atoms (a part of a hydrogen atom or a fluorine atom is substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or an amino group). May be).

  None of these acidic compounds are subject to the Important New Use Rules (SNUR) and can be used without any adverse effects on the human body.

Specifically, the acidic compound represented by the general formula (D-1) is preferably a compound such as (C ₄ F ₉ SO ₂ ) ₂ NH, (C ₃ F ₇ SO ₂ ) ₂ NH, Specifically, the acidic compound represented by the formula (D-2) is preferably a compound such as C ₁₀ F ₂₁ COOH.

  Specific examples of the acidic compounds represented by the general formulas (D-3) and (D-4) include compounds represented by the following structural formulas (D-5) and (D-6), respectively. preferable.

  When an acidic compound is blended, the blending amount is preferably about 0.1% by mass to 10% by mass in the protective film forming material.

[(E) Acid generating aid that generates acid in the presence of acid]
The material for forming a resist protective film according to the present invention may further contain (e) an acid generation auxiliary as required. The (e) acid generation auxiliary agent refers to an acid generation auxiliary agent that does not have a function of generating an acid alone but generates an acid in the presence of an acid. As a result, even if the acid generated from the acid generator in the resist film diffuses into the resist protective film, the acid generated from the acid generating auxiliary agent in the resist protective film by this acid is By compensating for the shortage of acid, it is possible to suppress the deterioration of the resolution of the resist composition and the reduction of the depth of focus, and a finer resist pattern can be formed.

  Such an acid generation aid is preferably an alicyclic hydrocarbon compound having both a carbonyl group and a sulfonyl group in the molecule.

Specifically, such an acid generation auxiliary agent is preferably at least one selected from the compounds represented by the following general formulas (E-1) and (E-2).

In the general formulas (E-1) and (E-2), R ₂₅ to R ₂₈ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, and X Is an electrophilic group having a sulfonyl group.

  Here, “a linear or branched alkyl group having 1 to 10 carbon atoms” means a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, secondary butyl group, Tributyl group, amyl group, isoamyl group, tertiary amyl group, hexyl group, heptyl group, octyl group, isooctyl group, 2-ethylhexyl group, tertiary octyl group, nonyl group, isononyl group, decyl group, isodecyl group, etc. A linear or branched saturated hydrocarbon group is exemplified.

X is “electrophilic group having a sulfonyl group”. Here, the “electrophilic group having a sulfonyl group” is preferably —O—SO ₂ —Y. Here, Y is an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 10 carbon atoms. Of these, Y is preferably a fluoroalkyl group.

Specific examples of the compounds represented by the general formulas (E-1) and (E-2) include the following structural formulas (E-3) to (E-10).

  (E) It is preferable that the compounding quantity of an acid generation adjuvant is 0.1 to 50 mass parts with respect to 100 mass parts of said (a) alkali-soluble polymer, and it is 1 to 20 mass parts. Is more preferable. By setting it as such a range, it becomes possible to generate | occur | produce an acid effectively with respect to the acid eluted from the resist film, and to improve a pattern shape, without generate | occur | producing unevenness of application | coating.

[(F) Others]
The protective film-forming composition according to the present invention may further contain an optional (f) surfactant as desired. Examples of this surfactant include “XR-104” (trade name: manufactured by Dainippon Ink & Chemicals, Inc.), but are not limited thereto. By blending such a surfactant, the coating properties and the ability to suppress the eluate can be further improved.

  When such a surfactant is blended, the blending amount is preferably 0.001 to 10 parts by mass with respect to 100 parts by mass of the (a) alkali-soluble polymer.

[Protective film cleaning solution]
The protective film cleaning and removing liquid according to the present invention is not particularly limited as long as it contains a polar organic solvent and can dissolve the protective film formed of the protective film forming material. Specifically, it is preferable to use the polar organic solvent of the component (b) described above. Among these, it is preferable to use alkyl alcohols as the component (b-1), and it is more preferable to use at least one selected from isobutanol and 4-methyl-2-pentanol.

  Furthermore, you may mix | blend surfactant etc. to such an extent that the characteristic of the protective film washing | cleaning removal liquid concerning this invention is not impaired.

[Photoresist composition]
The photoresist composition is not particularly limited, and any photoresist composition that can be developed with an alkaline aqueous solution, including negative and positive photoresist compositions, can be used. Examples of such a photoresist composition include (i) a positive photoresist composition containing a naphthoquinone diazide compound and a novolak resin, (ii) a compound that generates an acid upon exposure, and an acid that decomposes when exposed to an acid to increase the solubility in an alkaline aqueous solution. A positive photoresist composition containing a compound and an alkali-soluble resin, (iii) a compound that generates an acid upon exposure, a positive photoresist containing an alkali-soluble resin having a group that decomposes with an acid and increases the solubility in an aqueous alkali solution Examples thereof include (iv) a negative photoresist composition containing a compound that generates an acid by light, a crosslinking agent, and an alkali-soluble resin, but is not limited thereto.

[Example 1]
An alkali-soluble polymer (mass average molecular weight: 5000) represented by the following general formula (X-1) was dissolved in isobutanol to prepare a resist protective film-forming composition having a solid content concentration of 1.5% by mass.

  Next, TArF-6a239 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a resist material containing an acrylic resin, is applied onto a substrate on which ARC29 (manufactured by Brewer) having a film thickness of 77 nm is formed. A photoresist film having a film thickness of 150 nm was formed by heating for 2 seconds, and the protective film-forming material 1 was further applied thereon, and heated at 90 ° C. for 60 seconds to form a protective film having a film thickness of 35 nm.

  The substrate was subjected to pattern exposure using NSR-S302A (manufactured by Nikon Corporation), and post-exposure heating was performed at 110 ° C. for 60 seconds. Subsequently, the protective film was removed using isobutanol as a protective film washing removal solution. Subsequently, a 160 nm line and space photoresist pattern was formed by developing with a 2.38 mass% tetramethylammonium hydroxide aqueous solution for 30 seconds and rinsing. As a result of observing the photoresist pattern with an SEM (scanning electron microscope), the pattern shape was a good rectangular shape.

  A 160 nm line-and-space photoresist pattern was formed in exactly the same manner as in Example 1 except that the protective film washing and removing solution used in Example 1 was replaced with 4-methyl-2-heptanol. Similarly, as a result of observing this photoresist pattern with an SEM (scanning electron microscope), the pattern shape was a good rectangular shape.

[Comparative Example 1]
The protective film cleaning removal solution used in Example 1 was not used, but the protective film was washed and removed at the same time as the development in the 30-second development process using a 2.38 mass% tetramethylammonium hydroxide aqueous solution that is an alkaline developer. Formed a 160 nm line and space photoresist pattern in exactly the same manner as in Example 1. Similarly, as a result of observing this photoresist pattern with an SEM (scanning electron microscope), the pattern top portion was a T-top shape.

Claims (7)

A method of forming a photoresist pattern using an immersion exposure process,
(1) providing a photoresist film on the substrate;
(2) forming a protective film on the photoresist film using a protective film forming material;
(3) disposing an immersion exposure liquid on at least the protective film of the substrate, and selectively exposing the photoresist film through the immersion exposure liquid and the protective film;
(4) removing the protective film using a protective film cleaning solution containing a polar organic solvent;
(5) a step of developing the photoresist film using an alkali developer;
A method for forming a photoresist pattern.   2. The method for forming a photoresist pattern according to claim 1, wherein the protective film-forming material contains (a) an alkali-soluble polymer and (b) a polar organic solvent. 3. The method for forming a photoresist pattern according to claim 1, wherein the alkali-soluble polymer (a) is a polymer having a structural unit represented by the following general formula (A-1).

[In the above formula (A-1), R ₁ is an alkylene chain or fluoroalkylene chain having 1 to 6 carbon atoms, and R ₂ is independently a hydrogen atom or a straight chain having 1 to 6 carbon atoms, It is a branched or cyclic alkyl group or fluoroalkyl group, Z is an alkylene chain having 1 to 2 carbon atoms or an oxygen atom, and n is 0 to 3. ]   4. The method for forming a photoresist pattern according to claim 1, wherein the protective film cleaning and removing liquid containing the polar organic solvent is an alcohol solvent having 1 to 6 carbon atoms.   5. The method for forming a photoresist pattern according to claim 4, wherein the alcohol having 1 to 6 carbon atoms is at least one selected from isobutanol and 4-methyl-2-heptanol.   A material for forming a protective film used in the method for forming a photoresist pattern according to claim 1.   A protective film cleaning solution for use in the method of forming a photoresist pattern according to claim 1.