JP2009134174A - Protective film forming material and photoresist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective film forming material which has low environmental impact, substantially avoids damage to a photoresist pattern, and enables formation of a photoresist pattern having good rectangular geometry, and a photoresist pattern forming method using the protective film forming material. <P>SOLUTION: The protective film forming material for forming a protective film laid on a photoresist film includes (a) an alkali-soluble polymer and (b) a terpene-based solvent having an ether bond. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a protective film forming material for forming a protective film laminated on a photoresist film, and a photoresist pattern forming method using the protective film forming material.

  In recent years, an immersion exposure process has been reported as a new lithography technique (see Non-Patent Documents 1 to 3). According to this immersion exposure process, a light source having the same exposure wavelength can be used by replacing a conventional exposure optical path space with a so-called immersion exposure liquid (for example, pure water or a fluorine-based inert liquid). It is possible to form a photoresist pattern with higher resolution and excellent depth of focus (see Patent Documents 1 to 3).

  In addition, by using a protective film made of a resin that can only be dissolved in a specific solvent, the purpose is to simultaneously prevent the alteration of the photoresist film by the immersion exposure liquid and the refractive index fluctuation of the immersion exposure liquid. A technique has been proposed (see Patent Document 2).

More recently, from the viewpoint of simplification of the photoresist pattern formation process, improvement of production efficiency, etc., by using a protective film soluble in alkali, the removal of the protective film and the development of the photoresist pattern during alkali development after immersion exposure are performed. A technique for performing the formation simultaneously has been proposed (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

  Here, the protective film forming material disclosed in Patent Document 2 requires a fluorine-based special solvent. This fluorine-based special solvent has a problem that it has a large impact on the environment, such as a high global warming potential.

  The solvent used in the protective film forming material disclosed in Patent Document 3 is mainly an alcohol solvent. However, when an alcohol-based solvent is used, damage to the formed photoresist pattern is significant, and the resulting photoresist pattern may have a T-top shape, or the surface of the photoresist pattern may be roughened or swollen. .

  The present invention has been made in view of the above problems, and has a small impact on the environment, and has little damage to the photoresist pattern, and can form a favorable rectangular photoresist pattern, Another object of the present invention is to provide a photoresist pattern forming method using this protective film forming material.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by using a terpene solvent having an ether bond as a solvent in the protective film forming material. It came to complete. Specifically, the present invention provides the following.

  A first aspect of the present invention is a protective film-forming material for forming a protective film laminated on a photoresist film, wherein (a) an alkali-soluble polymer and (b) a terpene solvent having an ether bond And a protective film-forming material characterized by comprising:

  A second aspect of the present invention is a photoresist pattern forming method using an immersion exposure process, the step of providing a photoresist film on a substrate, and the protective film forming material of the present invention on the photoresist film. A step of forming a protective film, 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 And a developing step of developing the photoresist film after exposure by removing the protective film with a developing solution.

  ADVANTAGE OF THE INVENTION According to this invention, the protective film formation material which has little influence on an environment and has little damage to a photoresist pattern can be provided. By forming a protective film using such a protective film forming material, it becomes possible to form a favorable rectangular photoresist pattern.

[Protective film forming material]
The protective film-forming material of the present invention contains (a) an alkali-soluble polymer and (b) a terpene solvent having an ether bond. Hereinafter, each component contained in the protective film forming material of the present invention will be described.

<(A) Alkali-soluble polymer>
Specific examples of the (a) alkali-soluble polymer include the following embodiments.
First, as a first aspect of the (a) alkali-soluble polymer, a polymer having at least a monomer unit represented by the following general formula (A-1) as a constituent unit can be used.

In the above general formula (A-1), R ₁ is a hydrogen atom, or a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 6 carbon atoms, and R ₂ has 1 to 6 carbon atoms. An alkylene chain or a fluoroalkylene chain, and R ₃ is 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, a hydrogen atom or a part of the fluorine atom of the alkyl group or fluoroalkyl group may be substituted with a hydroxyl group.), Z is an alkylene chain having 1 to 2 carbon atoms or an oxygen atom, and n is 0 Is an integer from 3.

In particular, as R ₁ , in addition to a hydrogen atom, a linear alkyl group such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, or an n-hexyl group, Examples thereof include branched alkyl groups such as isopropyl group, 1-methylpropyl group, 2-methylpropyl group, and tert-butyl group, and cyclic alkyl groups such as cyclopentyl group and cyclohexyl group. Some or all of the hydrogen atoms of these alkyl groups may be substituted with fluorine atoms. Among these, from the viewpoint of improving water repellency, a perfluoroalkyl group in which all hydrogen atoms of these alkyl groups are substituted with fluorine atoms is preferable, and a trifluoromethyl group is particularly preferable.

Specific examples of R ₂ include a methylene chain, an ethylene chain, an n-propylene chain, an n-butylene chain, an n-pentylene chain, and an n-hexylene chain, a linear alkylene chain, a 1-methylpropylene chain, Examples include branched alkylene chains such as 2-methylpropylene chains. Some or all of the hydrogen atoms in these alkylene chains may be substituted with fluorine atoms.

Specific examples of R ₃ include linear alkyl groups such as methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-decyl group, and n-pentadecyl group, isopropyl Groups, branched alkyl groups such as 1-methylpropyl group, 2-methylpropyl group and tert-butyl group, and cyclic alkyl groups such as cyclopentyl group and cyclohexyl group. Some or all of the hydrogen atoms of these alkyl groups may be substituted with fluorine atoms. Further, a part of the alkyl group may be through an ether bond, and further, a part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group may be substituted with a hydroxyl group.

  Further, in the general formula (A-1), Z is preferably a methylene chain, and n is preferably 0.

  The alkali-soluble polymer of the first aspect is represented by the monomer unit represented by the general formula (A-1) and the following general formulas (A-2), (A-3), and (A-4). It may be a copolymer having at least one selected from monomer units as constituent units.

In the general formulas (A-2), (A-3), and (A-4), R ₄ , R _5, and R ₇ are a single bond, an alkylene chain having 1 to 6 carbon atoms, or a fluoroalkylene chain. , 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, and further an alkyl group or A hydrogen atom or a part of the fluorine atom of the fluoroalkyl group may be substituted with a hydroxyl group.), And R ₁ , Z and n have the same meaning as in the general formula (A-1).

  The monomer units represented by the general formulas (A-2), (A-3), and (A-4) are represented by the following general formulas (A-5), (A-6), and (A- It is preferable that it is a monomer unit represented by 7).

In the general formulas (A-5), (A-6), and (A-7), R ₉ is a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 6 carbon atoms, R ₁₀ is a linear or branched alkyl group or fluoroalkyl group having 2 to 10 carbon atoms (provided that part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group may be substituted with a hydroxyl group. R ₁₁ is a linear or branched alkyl group or fluoroalkyl group having 5 to 10 carbon atoms (provided that a part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group is substituted with a hydroxyl group) And R ₁ , Z, and n have the same meaning as in the general formula (A-1).

Among them, R ₉ is preferably a substituent selected from —CF ₃ and —C ₂ F ₅ , and R ₁₀ is —CH ₂ C ₂ F ₅ , —C (CH ₃ ) CH ₂ C ( CF ₃ ) ₂ OH, —CH ₂ C ₃ F ₇ , —CH ₂ C ₄ F ₉ is preferably a substituent selected from R ₉ , R ₁₁ is —C ₇ F ₁₅ , —CF ₂ CF (CF ₃ ) A substituent selected from CF ₂ CF ₂ CF ₂ CF (CF ₃ ) ₂ , —CF ₂ CF (CF ₃ ) CF ₂ C (CF ₃ ) ₃ is preferable.

  By incorporating the monomer unit represented by the above general formula (A-1) into the alkali-soluble polymer, it is possible to form a protective film having the required basic characteristics, particularly when applied to an immersion exposure process. In addition, the solubility in a terpene solvent having an ether bond (b) described later can be enhanced. The basic characteristics required for the protective film include high resistance to liquid for immersion exposure and low compatibility with a photoresist film provided in a lower layer.

  Moreover, by incorporating at least one selected from the monomer units represented by the above general formulas (A-2), (A-3), and (A-4) into the alkali-soluble polymer, It is possible to form a protective film having further improved characteristics.

  When using an alkali-soluble polymer as a copolymer, it is represented by the monomer unit represented by the general formula (A-1) and the general formulas (A-2), (A-3), and (A-4). The constitutional ratio (molar ratio) with at least one selected from monomer units is preferably 10:90 to 90:10, and more preferably 15:85 to 85:15.

  Next, (a) the second embodiment of the alkali-soluble polymer has 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 alkoxy group. Polymers can be used.

  That is, in the structural unit, a fluorine atom or a fluoroalkyl group, and an alcoholic hydroxyl group or an alkoxy group are bonded to the aliphatic cyclic compound, respectively, 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, and a nonafluorobutyl group. A methyl group is preferred. The alkoxy group is specifically a straight-chain, branched-chain, or cyclic alkoxy group or alkoxyalkoxy group having 1 to 15 carbon atoms.

  Specific examples of the alkoxy group having 1 to 15 carbon atoms include a methoxy group, an ethoxy group, a protooxy group, and a butoxy group. Examples of the alkoxyalkoxy group having 1 to 15 carbon atoms include a methoxymethoxy group and an ethoxymethoxy group. Group, protomethoxymethoxy group, butoxymethoxy group and the like.

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 a heptadiene that easily forms a polymer having a 5-membered ring or a 6-membered ring that is excellent in transparency and dry etching resistance, and moreover, 1,1,2,3,3-penta is a polymer formed by cyclic polymerization of fluoro-4-trifluoromethyl-4-hydroxy-1,6-heptadiene _{(CF 2 = CFCF 2 C (} CF 3) (OH) CH 2 CH = CH 2) It is most preferable industrially.

  Below, general formula (A-8) showing the said polymer is shown.

In the general formula (A-8), R ₁₂ is a hydroxyl group, a linear, branched, or cyclic alkoxy group or alkoxyalkoxy group having 1 to 15 carbon atoms, and l and m are each from 10 mol% to 90 mol. Mol%.

  Next, as a third aspect of the alkali-soluble polymer (a), a polymer having structural units represented by the following general formulas (A-9) and (A-10) can be used.

In the above formulas (A-9) and (A-10), R ₁₃ is a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 5 carbon atoms, and R ₁₄ is a hydrogen atom or a fluorine atom. Or a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 5 carbon atoms, and at least one of these R ₁₃ and R ₁₄ is a group having a fluorine atom. R ₁₅ is a hydrogen atom or a methyl group, and p is a repeating unit.

  More specifically, the structural units represented by the general formulas (A-9) and (A-10) are structural units represented by the following general formulas (A-11) and (A-12), respectively. Is preferably used.

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

In the above formula (A-13), R ₁₆ each independently represents a hydrogen atom, or a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 5 carbon atoms, and p is a repeating unit.

  Next, as a fourth aspect of (a) the alkali-soluble polymer, a polymer having a structural unit represented by the following general formula (A-14) can be used.

In the above formula _{(A-14), C} A is an alkylene chain or fluoroalkylene _{chain, R 17} is a straight-chain, branched-chain, or cyclic fluoroalkyl group having 1 to 5 carbon atoms, q is 0 to 3 P is a repeating unit. Note that in the above formula (A-14), part or all of the hydrogen atoms bonded to the carbon atoms constituting the ring skeleton may be substituted with fluorine atoms.

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

  Next, as a fifth aspect of (a) the alkali-soluble polymer, a polymer having a structural unit represented by the following general formula (A-16) can be used.

In the above formula (A-16), R ₁₈ is a hydrogen atom or a methyl group, R ₁₉ is an alkylene chain having 1 to 5 carbon atoms, and R ₂₀ is a hydrogen atom partially or entirely substituted with a fluorine atom. In addition, it is a fluoroalkylene chain having 1 to 10 carbon atoms, and p is a repeating unit.

  As the structural unit represented by the general formula (A-16), specifically, at least one selected from the following general formulas (A-17) and (A-18) is preferably used.

  Next, as a sixth aspect of (a) the alkali-soluble polymer, a polymer having a structural unit represented by the following general formula (A-19) can be used.

In the above formula (A-19), C _A is an alkylene chain or a fluoroalkylene chain, and R ₂₁ is a linear or branched chain having 1 to 5 carbon atoms in which part or all of the hydrogen atoms are substituted with fluorine atoms. Or a cyclic fluoroalkyl group, and R ₂₂ is a hydrogen atom, or a straight, 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. Q is an integer from 0 to 3, and p is a repeating unit. Note that in the general formula (A-19), part or all of the hydrogen atoms bonded to 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 formula (A-20) is preferably used.

  In the present invention, the above-mentioned (a) alkali-soluble polymer may be a copolymer or 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 (a) alkali-soluble polymer 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.

  (A) The blending amount of the alkali-soluble polymer 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 material. Is more preferable.

<(B) Terpene solvent having an ether bond>
(B) Since the terpene solvent having an ether bond has a smaller SP value (solubility parameter) than that of the alcohol solvent, the resin or acid in the photoresist composition having a polar group is used compared to the case of using the alcohol solvent. Compatibility with the generator is reduced. As a result, damage to the formed photoresist pattern can be suppressed, and a good photoresist pattern can be formed. Moreover, since it is a non-fluorine-based solvent, the influence on the environment can be reduced. In addition, the terpene solvent has a lower solubility in a photoresist film than a normal ether solvent, can provide a better photoresist pattern shape, and has an ether bond. Therefore, the general formula (A-1 It is possible to dissolve an alkali-soluble polymer having a monomer unit represented by

  Specific examples of the terpene solvent having an ether bond include 1,4-cineole, 1,8-cineole, and pinene oxide. Among these, 1,4-cineole and 1,8-cineole are preferable from the viewpoint of industrial availability. Further, these two or more kinds of solvents can be mixed and used.

<(C) Crosslinking agent>
The material for forming a protective film of the present invention may further contain (c) a crosslinking agent, if necessary. As the crosslinking agent (c), 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 having a hydroxyalkyl group and At least one nitrogen-containing compound selected from nitrogen-containing compounds having an imino group substituted with at least one substituent selected from alkoxyalkyl groups can be used.

  Examples of these nitrogen-containing compounds include melamine derivatives, urea derivatives, guanamine derivatives, acetoguanamine derivatives, benzoguanamine derivatives, succinyl, in which a hydrogen atom of an amino group is substituted with a methylol group and / or alkoxymethyl group. Examples thereof include amide 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 n-butanol, isobutanol or the like to be alkoxylated. Among them, a preferable crosslinking agent is tetrabutoxymethylated glycoluril.

  Further, (c) 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 alkoxy group and a monohydroxymonocarboxylic acid compound is also preferably used. Can do. 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.

  (C) When mix | blending a crosslinking agent, it is preferable that the compounding quantity shall be about 0.5 mass% to about 10 mass% with respect to the compounding quantity of (a) alkali-soluble polymer.

<(D) acidic compound>
The protective film-forming material of the present invention may further contain (d) an acidic compound as necessary. By adding the acidic compound (d), an effect of improving the shape of the photoresist pattern can be obtained. Further, after the immersion exposure, the photoresist film is exposed to an atmosphere containing a trace amount of amine before development. Even if it is a case (reservation after exposure), the bad influence by an amine can be effectively suppressed by interposition of a 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 an acidic compound (d) include at least one selected from the following general formulas (D-1), (D-2), (D-3), and (D-4). .

In the general formulas (D-1), (D-2), (D-3), and (D-4), s is an integer of 1 to 5, t is an integer of 10 to 15, and u Is an integer of 2 to 3, v is an integer of 2 to 3, and R ₂₃ is an alkyl group or fluoroalkyl group having 1 to 15 carbon atoms (a part of hydrogen atoms or fluorine atoms is a hydroxyl group or an alkoxy group) , Optionally substituted by a carboxyl group or an amino group.

  None of these acidic compounds are subject to the Important New Use Rules (SNUR) and have no adverse effects on the human body.

Specific examples of the acidic compound represented by the general formula (D-1) include (C ₄ F ₉ SO ₂ ) ₂ NH, (C ₃ F ₇ SO ₂ ) ₂ NH, and the like. Specifically, the acidic compound represented by (D-2) is preferably C ₁₀ F ₂₁ COOH or the like.

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

  (D) When mix | blending an acidic compound, it is preferable that the compounding quantity shall be about 0.1 mass% to about 10 mass% with respect to the whole quantity of the protective film formation material.

<(E) Acid generation auxiliary agent that generates acid in the presence of acid>
The material for forming a protective film of 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 photoresist film diffuses into the protective film, the acid generated from the acid generating auxiliary agent in the protective film due to this acid may cause a shortage of acid in the photoresist film. Therefore, it is possible to compensate for the deterioration of the resolution of the photoresist pattern and the reduction of the depth of focus, thereby making it possible to form a finer photoresist pattern.

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

  Specifically, the (e) 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 ₂₄ , R ₂₅ , R ₂₆ , and R ₂₇ are each independently a hydrogen atom, or a linear or branched chain having 1 to 10 carbon atoms. X is an electrophilic group having a sulfonyl group.

  Here, as the “linear or branched alkyl group having 1 to 10 carbon atoms”, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert. -Butyl group, amyl group, isoamyl group, tert-amyl group, hexyl group, heptyl group, octyl group, isooctyl group, 2-ethylhexyl group, tert-octyl group, nonyl group, isononyl group, decyl group, isodecyl group, etc. A linear or branched saturated hydrocarbon group may be mentioned.

X is “electrophilic group having a sulfonyl group”. Here, the “electrophilic group having a sulfonyl group” is preferably —O—SO ₂ —Y. 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 compounds represented by the following formulas (E-3) to (E-10).

  (E) When mix | blending an acid generation adjuvant, it is preferable that the compounding quantity shall be 0.1-50 mass parts with respect to 100 mass parts of (a) alkali-soluble polymer, and 1-20 mass parts. More preferably, it is a part. By setting it within such a range, it is possible to effectively generate an acid with respect to the acid eluted from the photoresist film without causing uneven coating, thereby improving the photoresist pattern shape.

<(F) Other>
The protective film-forming material of the present invention may further contain (f) a surfactant, if necessary. Examples of the surfactant include “XR-104” (trade name: manufactured by Dainippon Ink & Chemicals, Inc.), but are not limited thereto. By blending such a surfactant, it is possible to further improve the coating properties and the ability to suppress the eluate.

  When the 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.

[Photoresist composition]
The photoresist composition is not particularly limited, and any photoresist composition that can be developed with an aqueous alkaline solution, including negative and positive photoresists, 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) an acid generator that generates an acid upon exposure, and a solubility in an alkaline aqueous solution that decomposes with an acid. A positive photoresist composition containing an increasing compound and an alkali-soluble resin, (iii) an acid generator that generates an acid upon exposure, and an alkali-soluble resin having a group that decomposes with an acid and increases the solubility in an aqueous alkali solution And (iv) a negative photoresist composition containing an acid generator that generates an acid upon exposure, a crosslinking agent, and an alkali-soluble resin. However, the present invention is not limited to these. Absent.

[Photoresist pattern forming method]
The method for forming a photoresist pattern of the present invention comprises a step of providing a photoresist film on a substrate, a step of forming a protective film on the photoresist film using the protective film-forming material of the present invention, and at least on the protective film of the substrate. And a step of selectively exposing the photoresist film through the immersion exposure liquid and a protective film, and removing the protective film with a developer to form a photoresist film after exposure. A developing step for developing.

  First, a photoresist film is provided on the substrate. Specifically, a known photoresist composition is applied to a substrate such as a silicon wafer by using a known method such as a spinner, and then prebaked (PAB treatment) to form a photoresist film. A photoresist film may be formed after an organic or inorganic antireflection film (lower antireflection film) is provided on the substrate.

  The photoresist composition is not particularly limited, and any photoresist composition that can be developed with an alkaline aqueous solution can be used, including negative and positive photoresists. As such a photoresist composition, the above-described photoresist composition can be used.

  Next, a protective film is formed on the photoresist film using the protective film forming material of the present invention. Specifically, the protective film forming material according to the present invention is uniformly applied to the surface of the photoresist film by the same method as described above, and baked and cured to form the protective film.

Next, an immersion exposure liquid is disposed on at least the protective film of the substrate. 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. Among these, from the viewpoints of cost, safety, environmental problems, and versatility, it is preferable to use water (pure water, deionized water), but exposure light having a wavelength of 157 nm (eg, F ₂ excimer laser). When using, it is preferable to use a fluorine-based solvent from the viewpoint of low exposure light absorption.

  Next, the photoresist film is selectively exposed through the immersion exposure liquid and the protective film. At this time, since the photoresist film is shielded from the immersion exposure liquid by the protective film, the photoresist film is subjected to an alteration such as swelling under the invasion of the immersion exposure liquid, or conversely in the immersion exposure liquid. It is prevented that the optical characteristics such as the refractive index of the immersion exposure liquid itself are changed by elution of the components.

The wavelength used for exposure is not particularly limited, and is appropriately selected depending on the characteristics of the resist film. For example, it can be performed using radiation such as ArF excimer laser, KrF excimer laser, F ₂ excimer laser, extreme ultraviolet (EUV), vacuum ultraviolet (VUV), electron beam, X-ray, soft X-ray.

  When the exposure in the immersion state is completed, the substrate is taken out from the immersion exposure liquid and the liquid is removed from the substrate. It is preferable to perform post-bake (PEB treatment) on the photoresist film with the protective film being laminated on the exposed photoresist film.

  Next, the protective film is removed with an alkali developer, and the exposed photoresist film is developed. As the alkaline developer, a known developer can be appropriately selected and used. By this alkali development processing, the protective film is dissolved and removed simultaneously with the soluble portion of the photoresist film.

  Finally, rinsing is performed using pure water or the like. In this rinsing, for example, water is dropped or sprayed on the substrate surface while rotating the substrate, and the developer on the substrate, and the protective film component and the photoresist composition dissolved by the developer are washed away. 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, the photoresist pattern obtained by forming the protective film using the protective film forming material of the present invention forms the protective film using the conventional protective film forming material containing an alcohol solvent. Compared to the obtained photoresist pattern, the surface roughness is small and a good rectangular shape is obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples.

<Example 1>
First, TArF-7a128 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a photoresist composition containing an acrylic resin, is applied onto a substrate on which ARC29 (manufactured by Brewer) having a film thickness of 77 nm is formed. The film was heated for 1 second to form a 150 nm thick photoresist film. Then, this photoresist film was immersed in 1,8-cineole for 30 seconds. When the film thickness of the photoresist film before and after the immersion in 1,8-cineole was compared, it was confirmed that the decrease in the film thickness was as small as 1 nm or less and the damage to the photoresist film was small.

  Next, an alkali-soluble polymer (mass average molecular weight 4000) represented by the following formula (X-1) was dissolved in 1,8-cineole to prepare a protective film-forming material having a solid content concentration of 2 mass%. Then, a protective film-forming material was applied on the photoresist film formed in the same manner as described above, and heated at 90 ° C. for 60 seconds to form a protective film having a thickness of 35 nm.

  This substrate was exposed using an exposure machine NSR-S302A (manufactured by Nikon Corporation), and after exposure, pure water was dropped on the protective film for 1 minute and placed in a simulated immersion environment. And it heated at 100 degreeC for 60 second, performed the development process for 30 second using NMD-3 (made by Tokyo Ohka Kogyo Co., Ltd.), and also formed the photoresist pattern by performing the rinse process. When this photoresist pattern was observed with an SEM (scanning electron microscope), the pattern shape was a good rectangular shape, and no surface roughness was observed.

<Comparative Example 1>
First, a photoresist film formed in the same manner as in Example 1 was immersed in isobutanol for 30 seconds. When the film thickness of the photoresist film before and after immersion in isobutanol was compared, the decrease in the film thickness was as large as 10 nm or more, and it was confirmed that the damage to the photoresist film was greater than that using the solvent of Example 1. It was.

  Next, a protective film forming material was formed in the same manner as in Example 1 except that the solvent was isobutanol. In the same manner as in Example 1, a protective film was formed on the photoresist film, and a photoresist pattern was formed by performing exposure, development, and rinsing. When this photoresist pattern was observed with an SEM, the pattern shape was rounder than that in Example 1, and it was confirmed that the film was reduced.

<Comparative example 2>
First, a photoresist film formed in the same manner as in Example 1 was immersed in diisoamyl ether for 30 seconds. When the film thickness of the photoresist film before and after immersion in diisoamyl ether was compared, the decrease in film thickness was about 2 nm, and it was confirmed that the damage to the photoresist film was greater than that using the solvent of Example 1. It was done.

  Next, a protective film-forming material was formed in the same manner as in Example 1 except that the solvent was diisoamyl ether. In the same manner as in Example 1, a protective film was formed on the photoresist film, and a photoresist pattern was formed by performing exposure, development, and rinsing. When this photoresist pattern was observed with an SEM, the pattern shape was slightly rounder than that of Example 1, and it was confirmed that the film was reduced.

Claims (6)

A protective film forming material for forming a protective film laminated on a photoresist film,
A protective film-forming material comprising (a) an alkali-soluble polymer and (b) a terpene solvent having an ether bond.   The material for forming a protective film according to claim 1, which is used in an immersion exposure process.   3. The protective film-forming film according to claim 1, wherein the (b) terpene solvent having an ether bond is at least one selected from 1,4-cineole and 1,8-cineole. material. The protective film according to any one of claims 1 to 3, wherein the alkali-soluble polymer (a) is a polymer having a monomer unit represented by the following general formula (A-1) as a constituent unit. Forming material.

[In General Formula (A-1), R ₁ is a hydrogen atom, or a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 6 carbon atoms, and R ₂ has 1 to 6 carbon atoms. An alkylene chain or a fluoroalkylene chain, and R ₃ is a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 15 carbon atoms (provided that a part of the alkyl group may be bonded via an ether bond). Or a part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group may be substituted with a hydroxyl group.), Z is an alkylene chain having 1 to 2 carbon atoms or an oxygen atom, and n Is an integer from 0 to 3. ] The (a) alkali-soluble polymer further has at least one selected from monomer units represented by the following general formulas (A-2), (A-3), and (A-4) as a constituent unit. The material for forming a protective film according to any one of claims 1 to 4, wherein:

[In General Formulas (A-2), (A-3), and (A-4), R ₄ , R _5, and R ₇ are a single bond, or an alkylene chain or a fluoroalkylene chain having 1 to 6 carbon atoms. , 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, and further alkyl A part of the hydrogen atom or fluorine atom of the group or fluoroalkyl group may be substituted with a hydroxyl group.), And R ₁ , Z and n have the same meaning as in the general formula (A-1). ] A photoresist pattern forming method using an immersion exposure process,
Providing a photoresist film on the substrate;
Forming a protective film on the photoresist film using the protective film-forming material according to any one of claims 1 to 5,
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;
A developing step of removing the protective film with a developer and developing the photoresist film after exposure;
A photoresist pattern forming method comprising: