JP2007324385A - Resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resist pattern forming method for enabling a finer pattern with high resolution to be formed. <P>SOLUTION: The resist pattern forming method exposes a photoresist film to form a resist pattern by irradiating the photoresist film with radiation, while a liquid (immersion liquid) is interposed that has higher index of refraction than air. The method comprises a step (d) of separating a protective film from the surface of the photoresist film by use of a protective film separating liquid that satisfies the following condition (1): when a photoresist film with film thickness of 150 nm is formed on the surface of a substrate, and a protective film with film thickness of 90 nm is formed on the surface of the photoresist film; the protective film separating liquid is brought into contact with the protective film for 60 seconds period, the protective film is separated, and the photoresist film is melted to have film thickness of ≥147 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a resist pattern forming method. More specifically, a protective film for protecting the photoresist film from the immersion liquid during the immersion exposure in which the photoresist film is irradiated with radiation while the immersion liquid is interposed, and the photoresist film is exposed. It is related with the resist pattern formation method which can form a finer resist pattern with high resolution by peeling using a protective film peeling liquid which has predetermined solubility.

In recent years, miniaturization of integrated circuits has been progressing. In a projection exposure apparatus used for manufacturing an integrated circuit, the resolution R and the depth of focus δ are expressed by the following formulas (i) and (ii), the wavelength λ of radiation serving as an exposure light source is short, and the aperture of the projection lens The larger the value of the number NA, the smaller the value of the resolution R (minimum resolution dimension), and the resolution can be improved. Accordingly, in the projection exposure apparatus, the shortening of the wavelength of the exposure light source and the increase of the numerical aperture of the projection lens are proceeding at an accelerated speed.
R = k1 · λ / NA: (i)
δ = k ² · λ / NA ² : (ii)
(Where R: resolution, δ: depth of focus, λ: wavelength of exposure light source, NA: numerical aperture of projection lens, k1, k2: process coefficient)

  Apart from this, a technique called immersion exposure is also known as a lithography technique for improving the resolution. Immersion exposure is a technique in which a photoresist film is exposed by irradiating the photoresist film with radiation having a higher refractive index than liquid (immersion liquid). That is, the exposure is performed in a state where the space between the projection lens and the photoresist film, which is normally filled with air or nitrogen, is filled with the immersion liquid.

When the space between the projection lens and the photoresist film is filled with the immersion liquid having the refractive index n, the resolution R and the depth of focus δ are expressed by the following formulas (iii) and (iv). That is, by using an immersion liquid having a refractive index n, the value of resolution R (minimum resolution dimension) becomes 1 / n, and in addition to improving the resolution, the depth of focus δ is expanded and improved n times. Is possible. For example, when an ArF excimer laser (wavelength λ: 193 nm) is used as the light source and water having a refractive index n of 1.44 at the wavelength λ is used as the immersion liquid, non-immersion with air or nitrogen interposed The resolution R (minimum resolution dimension) is improved to 1 / 1.44 (69.4%), and the depth of focus δ is expanded and improved by 1.44 times.
R = k1 · (λ / n) / NA: (iii)
δ = k2 · nλ / NA ² : (iv)
(Where n: refractive index, R, δ, λ, NA, k1, k2 are synonymous with the proviso of formula (i) and formula (ii))

  Such immersion exposure technology is considered to be an indispensable technique as lithography technology for microfabrication, particularly for microfabrication in units of 10 nm, and a projection exposure apparatus for immersion exposure has already been disclosed. (For example, refer to Patent Document 1).

  However, in immersion exposure, since the immersion liquid directly contacts the photoresist film, an unexpected chemical reaction may be caused by the immersion liquid that has penetrated the photoresist film, which may adversely affect the resist performance. It has been pointed out (for example, see Patent Document 2).

Therefore, there is a resist pattern forming method in which immersion exposure is performed in a state where a protective film resistant to immersion liquid is formed on the surface of the photoresist film, and then the protective film is peeled off after performing post-exposure heat treatment. It has been proposed (see, for example, Patent Documents 3 and 4).
Japanese Patent Laid-Open No. 11-176727 JP 2005-268382 A JP-A-2005-250511 JP 2005-264131 A

  However, when exposure is performed by forming the protective film as described above on the surface of the photoresist film, an intermixing layer of the photoresist film and the protective film is formed on the surface of the photoresist film, and this intermixing is performed. There was a problem that the lithography performance was degraded by the layer. Further, the immersion liquid (for example, pure water) remains in the intermixing layer, so that a defect (watermark defect) in which a droplet trace remains on the resist pattern, the width of the resist pattern becomes thicker or vice versa. There has been a problem that a defect (pattern defect defect) may be generated. That is, although the immersion exposure technique can be expected to form a high-resolution resist pattern, it is still not fully satisfactory in that it may cause a watermark defect or a pattern defect defect. Improvements were sought.

  As described above, at present, there has not yet been disclosed a method for enabling the formation of a high-resolution resist pattern while effectively suppressing the occurrence of watermark defects and pattern defect defects. Is anxious.

  The present invention has been made to solve the above-described problems of the prior art, and can form a high-resolution resist pattern while effectively suppressing the occurrence of watermark defects and pattern defect defects. A possible resist pattern forming method is provided.

  As a result of intensive studies to solve the problems of the prior art as described above, the present inventors have used a protective film removing liquid having a predetermined solubility as a protective film for protecting a photoresist film from an immersion liquid. The present invention has been completed by conceiving that the above-mentioned problems can be solved by providing the step of peeling. Specifically, the present invention provides the following resist pattern forming method.

[1] Resist pattern formation in which a photoresist film is exposed to radiation in a state where a liquid (immersion liquid) having a higher refractive index than air is interposed, thereby exposing the photoresist film to form a resist pattern A step of forming the photoresist film on the surface of the substrate (a), a step of forming a protective film resistant to the immersion liquid on the surface of the photoresist film (b), and the liquid (C) irradiating the photoresist film with radiation in a state of immersion liquid, and using the protective film peeling liquid that satisfies the following condition (1) as the protective film, from the surface of the photoresist film A resist pattern forming method comprising a step (d) of peeling and a step (e) of developing the exposed photoresist film.
Condition (1): The photoresist film having a thickness of 150 nm is formed on the surface of the substrate, the protective film having a thickness of 90 nm is further formed on the surface of the photoresist film, and the protective film removing liquid is used as the protective film. When the contact is made for 60 seconds, the protective film is peeled off and the photoresist film is dissolved so as to remain in a thickness of 147 nm or more.

[2] The resist pattern forming method according to [1], wherein an organic solvent is used as the protective film remover.

[3] The resist pattern forming method according to [2], wherein the protective film stripping solution is made of the organic solvent having a boiling point of 100 ° C. or higher.
Protective film remover.

[4] As the protective film remover, monohydric alcohols, esters, ethers, chain or cyclic ketones, alkylene glycol monoalkyl ether acetates, alkylene glycol monoalkyl ethers, alkyl lactates, and γ- The method for forming a resist pattern according to [2] or [3], wherein a resist containing at least one organic solvent selected from the group consisting of butyrolactone is used.

  The resist pattern forming method of the present invention can favorably peel the protective film from the surface of the photoresist film, and can form a finer resist pattern with high resolution. Further, in the resist pattern forming method of the present invention, before the development step, the photoresist film has a predetermined thickness or more (specifically, 98% or more) with respect to the film thickness (initial film thickness) before the protective film is peeled off. Since the intermixing layer formed on the surface of the photoresist film can be peeled off at the same time as the protective film, the occurrence of watermark defects and defective pattern defects can be effectively suppressed. Meanwhile, a high-resolution resist pattern can be formed.

  Hereinafter, the best mode for carrying out the resist pattern forming method of the present invention will be specifically described. However, the present invention includes all embodiments including the invention-specific matters, and is not limited to the embodiments described below. In the present specification, the term “(meth) acrylic ester” means a concept including both an acrylic ester or a methacrylic ester.

In the resist pattern forming method of the present invention, the photoresist film is exposed to radiation in a state where a liquid (immersion liquid) having a higher refractive index than air is interposed, thereby exposing the photoresist film to form a resist pattern. A step of forming the photoresist film on the surface of the substrate (a) and a step of forming a protective film resistant to the immersion liquid on the surface of the photoresist film (B) a step (c) of irradiating the photoresist film with radiation in a state of interposing the immersion liquid, the protective film using a protective film peeling liquid that satisfies the following condition (1), A resist pattern forming method comprising a step (d) of peeling from the surface of a photoresist film and a step (e) of developing the exposed photoresist film.
Condition (1): The photoresist film having a thickness of 150 nm is formed on the surface of the substrate, the protective film having a thickness of 90 nm is further formed on the surface of the photoresist film, and the protective film removing liquid is used as the protective film. When the contact is made for 60 seconds, the protective film is peeled off and the photoresist film is dissolved so as to remain in a thickness of 147 nm or more.

[1] Step (a) (Formation of photoresist film):
In the resist pattern forming method of the present invention, first, as the step (a), a photoresist film is formed on the surface of the substrate.

[1-1] Substrate:
As the substrate, a silicon wafer, a silicon wafer coated with aluminum, or the like is usually used. In order to maximize the characteristics of the photoresist film, an organic or inorganic antireflection film is preferably formed on the surface of the substrate in advance (for example, Japanese Patent Publication No. 6-12252). (See the official gazette).

[1-2] Photoresist film (radiation sensitive resin composition):
The type of the material for forming the photoresist film is not particularly limited, and can be used by appropriately selecting from materials conventionally used for forming a photoresist film according to the purpose of use of the resist. That's fine.

  However, in the resist pattern forming method of the present invention, it is preferable to use a chemically amplified resist material containing an acid generator, particularly a positive resist material. As the chemically amplified positive resist material, for example, a radiation-sensitive resin composition containing an acid-dissociable group-modified alkali-soluble resin (component A) and a radiation-sensitive acid generator (component B) as essential components And the like. In such a resin composition, an acid is generated from an acid generator by irradiation (exposure), and an acid-dissociable group that protected an acidic group (for example, a carboxyl group) of the resin by the action of the generated acid. Dissociates to expose acidic groups. Accordingly, the alkali solubility of the exposed portion of the resist is increased, and the exposed portion is dissolved and removed by the alkali developer, so that a positive resist pattern can be formed.

[1-2A] Acid-dissociable group-modified alkali-soluble resin (component A):
The “acid-dissociable group-modified alkali-soluble resin” is a resin having an acidic group and at least a part of the acidic group being protected by the acid-dissociable group. This resin exhibits alkali insolubility or alkali insolubility in a state where at least part of the acid groups in the resin is protected by the acid dissociable group. However, when the acid dissociable group is dissociated by the action of an acid, the acid group is It is a resin that is exposed and exhibits alkali solubility.

  “Alkali insoluble or alkali poorly soluble” is obtained by a radiation sensitive resin composition containing an acid dissociable group-modified alkali soluble resin (component A) and a radiation sensitive acid generator (component B). When a film obtained only with an acid-dissociable group-modified alkali-soluble resin is developed in place of the photoresist film under the alkali development conditions used when forming a resist pattern from the photoresist film, the initial stage of the film This means that 50% or more of the film thickness remains after development.

  The “acidic group” is not particularly limited as long as it is a functional group exhibiting acidity. For example, a phenolic hydroxyl group, a carboxyl group, a sulfonic acid group, etc. are mentioned. Among these, a phenolic hydroxyl group and a carboxyl group are preferable because the effect of improving the solubility in alkali is high. Of these, the acid-dissociable group-modified alkali-soluble resin may have only one acidic group, or may have two or more acidic groups.

〔前記一般式（１）において、Ｒ^１は各々が同一又は異なった、炭素数４〜２０の一価の脂環式炭化水素基ないしはその誘導体、炭素数１〜４の直鎖状又は分岐状のアルキル基を示し、Ｒ^１同士が相互に結合して、炭素数４〜２０の脂環式炭化水素基ないしその誘導体を形成していてもよい。但し、Ｒ^１として、少なくとも１つの前記脂環式炭化水素基ないしその誘導体を含むか、Ｒ^１同士が相互に結合して、炭素数４〜２０の脂環式炭化水素基ないしその誘導体を形成した構造を含むものとする。〕 Specific examples of the structure of the component A include, for example, a polymer containing a repeating unit containing a skeleton represented by the following general formula (1) (hereinafter referred to as “repeating unit (1)”) as an essential unit. Can do.

[In the general formula (1), each R ¹ is the same or different, a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof, a linear or branched chain having 1 to 4 carbon atoms. R ¹ may be bonded to each other to form an alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof. However, R ¹ includes at least one alicyclic hydrocarbon group or a derivative thereof, or R ¹ is bonded to each other to form a C 4-20 alicyclic hydrocarbon group or a derivative thereof. It is assumed that the structure is included. ]

〔前記一般式（１ａ）〜（１ｄ）において、Ｒ^２は各々が同一又は異なった、炭素数１〜４の直鎖状又は分岐状のアルキル基、ｍは０又は１を示す。〕 Among the skeletons represented by the above general formula (1), the component A preferably includes skeletons represented by the following general formulas (1a) to (1d).

[In the general formulas (1a) to (1d), R ² is the same or different and each represents a linear or branched alkyl group having 1 to 4 carbon atoms, and m represents 0 or 1. ]

  The main chain structure of the repeating unit (1) is not particularly limited, but is preferably a (meth) acrylic acid ester or α-trifluoroacrylic acid ester structure.

  Specific structures of the repeating unit (1) include (meth) acrylic acid 2-methyladamantyl-2-yl ester, (meth) acrylic acid 2-ethyladamantyl-2-yl ester, (meth) acrylic acid- 2-methylbicyclo [2.2.1] hept-2-yl ester, (meth) acrylic acid-2-ethylbicyclo [2.2.1] hept-2-yl ester, (meth) acrylic acid 1- ( Bicyclo [2.2.1] hept-2-yl) -1-methylethyl ester, (meth) acrylic acid 1- (adamantan-1-yl) -1-methylethyl ester, (meth) acrylic acid 1-methyl -1-cyclopentyl ester, (meth) acrylic acid 1-ethyl-1-cyclopentyl ester, (meth) acrylic acid 1-methyl-1-cyclohexyl ester, ( Data) acrylic acid 1-ethyl-1-cyclohexyl ester.

  In the state where at least a part of the acidic group is protected by the acid-dissociable group, it is insoluble in alkali or hardly soluble in alkali. However, when the acid-dissociable group is dissociated by the action of an acid, the acidic group is exposed and alkali-soluble. As long as it has the property, the structure of the component A is not particularly limited. Therefore, the component A is not limited to the polymer containing the repeating unit (1), and may be appropriately selected from resins conventionally used for such applications according to the purpose.

  When the component A contains the repeating unit (1), it may be a homopolymer of one type of repeating unit (1), or may be a copolymer of two or more types of repeating units (1). It may be a polymer containing a repeating unit other than the repeating unit (1) in addition to the repeating unit (1). As a content rate of a repeating unit (1), it is 0-70 mol% normally with respect to all the repeating units, It is preferable that it is 15-60 mol%, It is still more preferable that it is 20-50 mol%. . If the content of the repeating unit (1) exceeds 70 mol%, the exposure margin may be deteriorated.

  In addition, the polymer which comprises A component should just protect at least one part of an acidic group by the acid dissociable group, and all the acidic groups do not need to be protected by the acid dissociable group. The introduction rate of the acid dissociable group (the ratio of the number of acid dissociable groups to the total number of acid groups and acid dissociable groups in the polymer constituting the component A) is based on the type and base of the acid dissociable group. Varies depending on the type of polymer. However, the introduction rate is preferably in the range of 5 to 100%, and more preferably in the range of 10 to 100%.

  There is no particular limitation on the range of the molecular weight of the polymer constituting the A component, and various molecular weight ranges can be used as necessary. The polystyrene-reduced mass average molecular weight (may be referred to as “Mw”) measured by gel permeation chromatography (GPC) is usually 1,000 to 100,000, and 1,000 to 30,000. Is preferable, and it is more preferable to set it as 1,000-20,000. By setting it as such a range, the resist excellent in heat resistance and developability can be obtained. On the other hand, when the Mw of the polymer constituting the component A is less than 1,000, the resulting resist tends to have insufficient heat resistance. On the other hand, if Mw exceeds 100,000, the developability of the resulting resist may be reduced.

  Further, there is no particular limitation on the ratio (Mw / Mn) between the polystyrene-equivalent weight average molecular weight Mw and the polystyrene-equivalent number average molecular weight (may be referred to as “Mn”) measured by GPC, and various molecular weights may be used as necessary. Range. The value of Mw / Mn is usually 1 to 5, preferably 1 to 3. By setting it as such a range, the resist excellent in the resolution can be obtained.

[1-2B] Radiation sensitive acid generator (component B):
A “radiation sensitive acid generator” is an additive that generates an acid in response to radiation. The B component generates an acid by irradiation (exposure), and the acid generated by the action of the generated acid dissociates the acid dissociable group that protected the acidic group (for example, carboxyl group) of the resin, thereby exposing the acidic group. Let Accordingly, it is possible to improve the alkali solubility of the exposed portion of the resist and form a positive resist pattern by alkali development.

  As long as it has the above properties, the structure of the B component is not particularly limited. Therefore, what is necessary is just to select suitably from the substances conventionally used for such a use according to the objective. For example, onium salt compounds such as iodonium salts, sulfonium salts, phosphonium salts, diazonium salts, pyridinium salts; halogen-containing compounds such as haloalkyl group-containing hydrocarbon compounds and haloalkyl group-containing heterocyclic compounds; 1,3-diketo-2- Diazo ketone compounds such as diazo compounds, diazobenzoquinone compounds, diazonaphthoquinone compounds; sulfone compounds such as β-ketosulfone, β-sulfonylsulfone, and α-diazo compounds of these compounds; and sulfonic acid compounds;

〔前記一般式（２）において、Ｒ^３は水素原子、フッ素原子、水酸基、炭素数１〜１０の直鎖状又は分岐状のアルキル基、炭素数１〜１０の直鎖状又は分岐状のアルコキシル基、炭素数２〜１１の直鎖状又は分岐状のアルコキシカルボニル基を示し、Ｒ^４は炭素数１〜１０の直鎖状又は分岐状のアルキル基、アルコキシル基、炭素数１〜１０の直鎖状、分岐状、環状のアルカンスルホニル基を示し、ｒは０〜１０の整数を示す。Ｒ^５は各々が同一又は異なった、炭素数１〜１０の直鎖状又は分岐状のアルキル基、置換されていてもよいフェニル基、置換されていてもよいナフチル基を示し、Ｒ^５同士が相互に結合して、炭素数２〜１０の環構造ないしその誘導体を形成していてもよい。ｋは０〜２の整数、Ｒ^６はフッ素原子又は置換されていてもよい炭素数１〜１２の炭化水素基、ｎは１〜１０の整数を示す。〕 Among these, it is preferable to use a sulfonium salt having a structure represented by the following general formula (2).

[In the general formula (2), R ³ represents a hydrogen atom, a fluorine atom, a hydroxyl group, a linear or branched alkyl group having 1 to 10 carbon atoms, or a linear or branched alkoxyl group having 1 to 10 carbon atoms. A straight chain or branched alkoxycarbonyl group having 2 to 11 carbon atoms, R ⁴ is a linear or branched alkyl group having 1 to 10 carbon atoms, an alkoxyl group, or a straight chain having 1 to 10 carbon atoms. A chain, branched, or cyclic alkanesulfonyl group is shown, and r is an integer of 0 to 10. R ⁵ each have the same or different, linear or branched alkyl group having 1 to 10 carbon atoms, an optionally substituted phenyl group, a naphthyl group which may be substituted, R ⁵ to each other They may be bonded to each other to form a ring structure having 2 to 10 carbon atoms or a derivative thereof. k is an integer of 0 to 2, R ⁶ is a fluorine atom or an optionally substituted hydrocarbon group having 1 to 12 carbon atoms, and n is an integer of 1 to 10. ]

  As the component B, the various acid generators described above may be used alone or in combination of two or more. The blending amount of the B component may be appropriately set according to the characteristics desired to be imparted to the resist, but is usually 0.1 to 20 parts by mass and 0.5 to 10 parts by mass with respect to 100 parts by mass of the A component. It is preferable that By setting it as such a range, the resist excellent in the sensitivity and developability can be obtained. On the other hand, if the blending amount of component B is less than 0.1 parts by mass, the sensitivity and developability tend to decrease. Moreover, when it exceeds 20 mass parts, the transparency with respect to a radiation will fall and it will become difficult to obtain a rectangular resist pattern.

[1-2C] Additive:
In the radiation sensitive resin composition, additives other than the A component and the B component, for example, an acid diffusion control agent, an alicyclic additive having an acid dissociable group, a sensitizer, and a surfactant, as necessary. Etc. may be blended.

  The “acid diffusion inhibitor” is an additive that controls the diffusion phenomenon of an acid generated from an acid generator or the like upon exposure in the photoresist film and suppresses an undesirable chemical reaction in a non-exposed region. By blending an acid diffusion inhibitor, the storage stability of the radiation sensitive resin composition can be improved. In addition, by adding an acid diffusion inhibitor, it is possible to improve the resolution of the resist and to suppress changes in the line width of the resist pattern due to fluctuations in the holding time (PED) from exposure to development processing. As a result, there is an advantage that a radiation sensitive resin composition having extremely excellent process stability can be obtained.

  The acid diffusion inhibitor is preferably a nitrogen-containing organic compound whose basicity does not change by exposure or heat treatment during resist pattern formation. Examples of the nitrogen-containing organic compound include tertiary amine compounds such as alkylamines, cycloalkylamines, aromatic amines, and alkanolamines; amide group-containing compounds such as Nt-butoxycarbonyl group-containing amino compounds; Quaternary ammonium hydroxide compounds such as tetra-n-propylammonium hydroxide and tetra-n-butylammonium hydroxide; nitrogen-containing heterocyclic compounds such as pyridines, piperazines and imidazoles; These acid diffusion inhibitors may be used alone or in combination of two or more.

  The amount of the acid diffusion inhibitor is usually 10 parts by mass or less, preferably 0.001 to 10 parts by mass, and preferably 0.005 to 5 parts by mass with respect to 100 parts by mass of the component A. More preferably. The amount of the acid diffusion inhibitor is preferably 10 parts by mass or less because the sensitivity as a resist and the developability of an exposed part can be improved. Moreover, when the compounding quantity of the said acid diffusion inhibitor shall be 0.001 mass part or more, since it can suppress that the pattern shape and dimensional fidelity as a resist fall with process conditions, it is preferable.

  The “alicyclic additive having an acid-dissociable group” is a component having an action of further improving dry etching resistance, pattern shape, adhesion to a substrate, and the like. Examples of the alicyclic additive include adamantane derivatives such as 1-adamantanecarboxylic acid and 2-adamantanone; and deoxycholic acid esters such as t-butyl deoxycholic acid and t-butoxycarbonylmethyl deoxycholic acid; Lithocholic acid esters such as tert-butyl lithocholic acid and t-butoxycarbonylmethyl lithocholic acid; Alkylcarboxylic acid esters such as dimethyl adipate and diethyl adipate; 3- [2-hydroxy-2,2-bis (trifluoro) Methyl) ethyl] tetracyclo [4.4.0.12,5.17,10] dodecane and the like.

  The said alicyclic additive may be used individually by 1 type, and may use 2 or more types together. From the viewpoint of improving the heat resistance of the resist, the amount of the alicyclic additive is preferably 50 parts by mass or less and more preferably 30 parts by mass or less with respect to 100 parts by mass of the component A. . When the compounding amount of the alicyclic additive exceeds 50 parts by mass, the heat resistance of the resist tends to be insufficient.

  “Sensitizer” absorbs radiation energy, transmits the energy to B component, and increases the amount of acid generated. It improves the apparent sensitivity of the radiation-sensitive resin composition. Has an effect.

  Examples of the sensitizer include carbazoles, acetophenones, benzophenones, naphthalenes, phenols, biacetyl, eosin, rose bengal, pyrenes, anthracenes, phenothiazines and the like. These sensitizers may be used individually by 1 type, and may use 2 or more types together. It is preferable that the compounding quantity of a sensitizer shall be 50 mass parts or less with respect to 100 mass parts of A components.

  “Surfactant” is a component that exhibits an effect of improving coatability, striation, developability, and the like. As the surfactant, any of an anionic, cationic, nonionic or amphoteric surfactant can be used, but a nonionic surfactant is preferably used. Nonionic surfactants include, for example, polyoxyethylene higher alkyl ethers, polyoxyethylene higher alkyl phenyl ethers, polyethylene glycol higher fatty acid diesters, etc., and all of the following trade names: “KP” (Shin-Etsu) “Chemical Industry Co., Ltd.”, “Polyflow” (manufactured by Kyoeisha Yushi Chemical Co., Ltd.), “F Top” (manufactured by Tochem Products Co., Ltd.), “Mega Fuck” (manufactured by Dainippon Ink & Chemicals), “Fluorard” (Sumitomo 3M) Etc.), “Asahi Guard” and “Surflon” (Asahi Glass Co., Ltd.).

  One of these surfactants may be used alone, or two or more thereof may be mixed and used. The compounding amount of the surfactant is usually 2 parts by mass or less, preferably 1.5 parts by mass or less, with respect to 100 parts by mass of the total resin components in the radiation-sensitive resin composition. More preferably, it is as follows.

  The radiation-sensitive resin composition may be blended with a dye or a pigment in order to visualize the latent image of the exposed area and reduce the influence of halation during exposure, or to improve the adhesion to the substrate. An adhesion aid may be blended. In addition to the above-mentioned additives, antihalation agents, storage stabilizers, antifoaming agents and the like can be mentioned.

[1-2D] Solvent:
In addition to the A component, the B component, and various additives, a solvent may be added to the radiation sensitive resin composition. By mix | blending a solvent, the coating property at the time of coating a radiation sensitive resin composition to a board | substrate can be improved.

  The type of the “solvent” is not particularly limited, and examples thereof include linear or branched ketones such as 2-butanone and 3-methyl-2-butanone; cyclic esters such as cyclopentanone and 3-methylcyclopentanone. Ketones; propylene glycol monoalkyl ether acetates such as propylene glycol monomethyl ether acetate; alkyl 2-hydroxypropionates such as methyl 2-hydroxypropionate; alkyl 3-alkoxypropionates such as methyl 3-methoxypropionate Other examples include γ-butyrolactone. These solvents can be used alone or in admixture of two or more.

  The amount of the solvent used is such that when the component A, component B and various additives are dissolved, the total solid content is 5 to 50% by mass, preferably 10 to 50% by mass, more preferably 10 to 40% by mass. %, More preferably 10 to 30% by mass, particularly preferably 10 to 25% by mass. By setting it as this range, since the uniformity in a film surface at the time of application | coating becomes favorable, it is preferable.

[1-3] Formation of photoresist film:
For the photoresist film, for example, a solvent is added to the A component, the B component, and various additives to adjust the total solid content concentration to 5 to 50% by mass, and the solution is filtered with a filter having a pore size of about 0.2 μm. Thus, a coating solution can be prepared, and this coating solution can be formed by coating on a substrate using a conventionally known coating method such as spin coating, cast coating, roll coating or the like. This photoresist film may be pre-baked (hereinafter sometimes referred to as “PB”) in order to volatilize the solvent. In forming the photoresist film, the coating solution may be prepared by itself or a commercially available resist solution may be used as the coating solution. The thickness of the photoresist film formed on the surface of the substrate is not particularly limited, but is preferably 100 to 300 nm.

[2] Step (b) (formation of protective film):
In the resist pattern forming method of the present invention, after forming the photoresist film as described above, as a step (b), a protective film resistant to the immersion liquid is formed on the surface of the photoresist film. By forming the protective film, the immersion liquid is prevented from coming into direct contact with the photoresist film during the immersion exposure, and the lithography performance of the photoresist film is reduced by the penetration of the immersion liquid, or the photoresist It is possible to effectively prevent the lens of the projection exposure apparatus from being contaminated by the components eluted from the film.

  In addition to being able to form a stable film against an immersion liquid (for example, pure water), the protective film is preferably formed of a material that can be easily peeled after immersion exposure. Is formed of resin. In addition, “stable against immersion liquid” means that the change in film thickness is within 3% of the initial film thickness as measured by the stability evaluation method for water described below.

[Stability evaluation test]
(1): Using a coater / developer (1) (trade name: CLEAN TRACK ACT8, manufactured by Tokyo Electron Ltd.), a protective film-forming coating solution (resin for forming a protective film is dissolved in a solvent) on an 8-inch silicon wafer. And a protective film having a film thickness of 90 nm is formed by performing PB under the conditions of 90 ° C. and 60 seconds. The film thickness (initial film thickness) of this protective film is measured using a light interference type film thickness measuring device (trade name: Lambda Ace VM-90, manufactured by Dainippon Screen Mfg. Co., Ltd.).
(2): Next, after the ultrapure water was discharged from the rinse nozzle of the coater / developer (1) for 60 seconds onto the surface of the wafer on which the protective film was formed, it was shaken off at a rotational speed of 4000 rpm for 15 seconds, and spin-dried. To do. At this time, the film thickness of the protective film is measured again, and the film thickness change (decreased film thickness) of the protective film is calculated. If the ratio of the reduced film thickness to the initial film thickness is within 3%, it is evaluated as “stable against immersion liquid”.

  A resin for forming a protective film (resin for forming a protective film) is prepared by adding an appropriate organic solvent to adjust the total solid content concentration to about 0.1 to 20% by mass, and the solution has a pore size of 0.2 μm. A coating solution is prepared by filtering with a filter of a degree, and this coating solution is formed by coating on a photoresist film using a conventionally known coating method such as spin coating, cast coating, roll coating, etc. can do. This protective film may be baked to volatilize the solvent. In the method of the present invention, it is preferable to use a fat-soluble resin as the protective film-forming resin. The fat-soluble resin may be an alkali-soluble resin as long as it has solubility in an organic solvent.

〔但し、一般式（３）又は（４）において、Ｒ^７は水素、メチル基又はトリフルオロメチル基、Ｒ^８は二価の有機基、Ｒ^９は炭素数４〜２０の脂環式炭化水素基又はその誘導体を示す。〕 As the above-mentioned fat-soluble resin, for example, a resin comprising a polymer containing at least one repeating unit selected from the group consisting of the following general formula (3) and the following general formula (4) as a constituent component is preferable. Since these resins have a trifluoromethyl group or an alicyclic hydrocarbon group having 4 to 20 carbon atoms in their structure, they form a protective film resistant to pure water that is widely used as an immersion liquid. In addition to being capable of being lipid-soluble, for example, in the step of peeling the protective film described later (step (d)), monohydric alcohols, esters, ethers, chain or cyclic ketones, alkylene glycols, etc. It can be easily peeled off by a protective film peeling solution containing at least one organic solvent selected from the group consisting of monoalkyl ether acetates, alkylene glycol monoalkyl ethers, alkyl lactates, and γ-butyrolactone.

[In the general formula (3) or (4), R ⁷ is hydrogen, a methyl group or a trifluoromethyl group, R ⁸ is a divalent organic group, and R ⁹ is an alicyclic hydrocarbon having 4 to 20 carbon atoms. Group or derivative thereof is shown. ]

In the general formula (3), examples of the “divalent organic group” represented by R ⁸ include divalent hydrocarbon groups; atoms other than carbon atoms and hydrogen atoms, such as alkylene glycol groups and alkylene ester groups. A divalent organic group containing, and the like. Among these, linear, branched or cyclic divalent hydrocarbon groups are preferable, and linear or branched saturated hydrocarbon groups, monocyclic hydrocarbon ring groups, bridged cyclic hydrocarbon ring groups, and the like Is more preferable.

Examples of the alicyclic hydrocarbon group having 4 to 20 carbon atoms of R ⁹ include, for example, norbornane, tricyclodecane, tetracyclododecane, adamantane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane and the like. Alicyclic hydrocarbon groups derived from alkanes and the like; the hydrogen atoms of these alicyclic hydrocarbon groups are, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, 2 -A group substituted with one or more linear, branched or cyclic alkyl groups having 1 to 4 carbon atoms such as -methylpropyl group, 1-methylpropyl group, t-butyl group, etc. Can do. Among these alicyclic hydrocarbon groups, alicyclic hydrocarbon groups derived from norbornane, tricyclodecane, tetracyclododecane, adamantane, cyclopentane or cyclohexane, and the hydrogen atoms of these alicyclic hydrocarbon groups A group substituted with the alkyl group is preferred.

  The resin for forming the protective film may contain only one type of at least one repeating unit selected from the group consisting of the general formula (3) and the following general formula (4), or two or more types. May be included. Moreover, repeating units other than the above repeating unit may be included. The total content of at least one repeating unit selected from the group consisting of the above general formula (3) and the following general formula (4) is usually 60 mol% or more with respect to all the repeating units, and 65 It is preferably at least mol%, more preferably at least 70 mol%. If the total content of these repeating units is less than 60 mol%, elution of the acid generator and the like from the photoresist film may not be suppressed.

  The organic solvent used in preparing the coating solution may be appropriately selected in consideration of the solubility of the fat-soluble resin, but alcohols are preferably used, and monohydric alcohols are more preferably used. It is particularly preferable to use monohydric alcohols having 1 to 10 carbon atoms. These organic solvents are preferable in that they are excellent in solubility of the fat-soluble resin, are difficult to cause intermixing with the photoresist film to be coated, and have a low possibility of adversely affecting the lithography performance.

  Examples of the “monohydric alcohol having 1 to 10 carbon atoms” include methanol, ethanol, 1-propanol, isopropanol, n-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2- Pentanol, 3-pentanol, n-hexanol, cyclohexanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl -1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol Monohydric alcohols having 1 to 6 carbon atoms such as 4-methyl-1-pentanol and 4-methyl-2-pentanol; 2 2-dimethyl-3-pentanol, 2,3-dimethyl-3-pentanol, 2,4-dimethyl-3-pentanol, 4,4-dimethyl-2-pentanol, 3-ethyl-3-pentanol , 1-heptanol, 2-heptanol, 3-heptanol, 2-methyl-2-hexanol, 2-methyl-3-hexanol, 5-methyl-1-hexanol, 5-methyl-2-hexanol, etc. 2-ethyl-1-hexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, 1-octanol, 2-octanol, 3-octanol, 2-propyl-1-pentanol C8 monohydric alcohols such as 2,4,4-trimethyl-1-pentanol; 2,6-dimethyl-4-heptanol, 3- C9 monohydric alcohols such as til-2,2-dimethyl-1-pentanol, 1-nonanol, 2-nonanol, 3,5,5-trimethyl-1-hexanol; 1-decanol, 2-decanol , 4-decanol, 3,7-dimethyl-1-octanol, 3,7-dimethyl-3-octanol and other monohydric alcohols having 10 carbon atoms. Among these alcohols, 4-methyl-2-pentanol, butanol, hexanol, or a mixed solvent thereof is preferably used because it is difficult to solidify at a low temperature and hardly remains in the photoresist film. Other solvents may be mixed. The “other solvent” makes it possible to uniformly coat the protective film, so that the protective film-forming resin can be sufficiently dissolved and the photoresist film is difficult to dissolve. Just choose.

  Examples of the “other solvent” include polyhydric alcohols such as ethylene glycol and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol Alkyl ethers of polyhydric alcohols such as monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol ethyl ether acetate, diethylene glycol ethyl Alkyl ether acetates of polyhydric alcohols such as ether acetate, propylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate; aromatic hydrocarbons such as toluene, xylene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy- Ketones such as 4-methyl-2-pentanone and diacetone alcohol; ethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate , Ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3-ethoxy Propionic acid ethyl esters such as 3-ethoxy-methylpropionic acid; water, and the like can be listed. Among these, it is preferable to use cyclic ethers, polyhydric alcohol alkyl ethers, polyhydric alcohol alkyl ether acetates, ketones, esters, and water.

  The organic solvent may be used individually by 1 type, may use 2 or more types together, and may contain water as long as the uniformity of a solvent can be maintained. The content of monohydric alcohol having 10 or less carbon atoms in the organic solvent should be 10 to 100% by mass with respect to the total solvent in order to exert the effect that it is difficult to solidify at low temperatures and hardly remain in the photoresist film. Is preferable, and it is still more preferable to set it as 20-100 mass%.

  A surfactant may be added to the coating solution for the purpose of improving coating properties, antifoaming properties, leveling properties and the like. The surfactants are all trade names below, BM-1000, BM-1100 (above, manufactured by BM Chemie), MegaFuck F142D, F172, F173, F173 (above, Dainippon Ink and Chemicals, Inc.). Manufactured), FLORARD FC-135, FC-170C, FC-430, FC-431 (above, manufactured by Sumitomo 3M), Surflon S-112, S-113, S-131, S-141 Fluorine-based surfactants such as S-145 (made by Asahi Glass Co., Ltd.), SH-28PA, -190, -193, SZ-6032, SF-8428 (made by Toray Dow Corning Silicone). Can be used. The blending amount of these surfactants is preferably 5 parts by mass or less with respect to 100 parts by mass of the fat-soluble resin.

  The thickness of the protective film is preferably as close as possible to an odd multiple of λ / 4m (where λ is the wavelength of radiation and m is the refractive index of the protective film). This is because the reflection suppressing effect at the upper interface of the photoresist film is increased. The specific thickness of the protective film is preferably 30 to 300 nm.

[3] Step (c) (immersion exposure):
In the step (c) of the resist pattern forming method of the present invention, the photoresist film is irradiated with radiation in a state where a liquid (immersion liquid) having a refractive index higher than that of air is interposed. It is a step of exposing.

  The immersion liquid may be a liquid having a higher refractive index than air, but usually water is used, and pure water is preferably used. With this immersion liquid interposed (that is, with the immersion liquid filled between the lens of the exposure apparatus and the photoresist film), the photoresist film is irradiated with radiation through a mask having a predetermined pattern. To expose.

  The radiation that can be used in the immersion exposure may be appropriately selected according to the type of the photoresist film or the protective film to be used. For example, visible rays; ultraviolet rays such as g rays and i rays; excimer lasers Various radiations such as deep ultraviolet rays such as X-rays, X-rays such as synchrotron radiation, and charged particle beams such as electron beams can be used. Among them, it is preferable to use an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm). Moreover, what is necessary is just to set suitably exposure conditions, such as a radiation dose, according to the compounding composition of a radiation sensitive resin composition, the kind of additive, etc.

  In the resist pattern forming method of the present invention, post-exposure heat treatment (hereinafter sometimes referred to as “PEB”) may be performed after the immersion exposure described above. Such PEB is preferable because the resolution, pattern shape, developability, and the like of the resist can be improved. The heating conditions for PEB vary depending on the composition of the radiation-sensitive resin composition, the type of additive, etc., but are preferably 30 to 200 ° C, more preferably 50 to 150 ° C. In addition, you may perform this post-exposure heat processing, after performing the process (d) (protective film peeling) mentioned later.

[4] Step (d) (protective film peeling):
In step (d) of the resist pattern forming method of the present invention, the protective film formed on the surface of the photoresist film after the exposure of the photoresist film in the step (c) is a protective film satisfying the following condition (1) This is a step of stripping from the surface of the photoresist film using a stripping solution.
Condition (1): The photoresist film having a thickness of 150 nm is formed on the surface of the substrate, the protective film having a thickness of 90 nm is further formed on the surface of the photoresist film, and the protective film removing liquid is used as the protective film. When the contact is made for 60 seconds, the protective film is peeled off and the photoresist film is dissolved so as to remain in a thickness of 147 nm or more.

  In the above condition (1), the photoresist film is dissolved at least (specifically, with a thickness of less than 3 nm). If the photoresist film is not dissolved at all, It is assumed that the conditions are not met. Although not particularly limited, it is preferable that at least 0.05 nm of the surface of the photoresist film is dissolved under the condition (1).

  The protective film peeling step (d) may be performed at any stage before the development step (step (e)) described later, but is preferably after the post-exposure heat treatment described above. In this way, by removing the protective film before the development step (step (e)), a watermark defect or pattern defect defect of the photoresist film caused by the immersion liquid that has penetrated the protective film. Can be effectively prevented. Furthermore, in the resist pattern forming method of the present invention, in this step (d), the intermixing layer of the photoresist film and the protective film can be peeled off simultaneously. In addition, this process (d) can also be performed simultaneously with the image development process (process (e)).

  The above condition (1) is a condition for showing the solubility of the protective film stripping solution to be used, and the thickness of the photoresist film and the protective film formed on the surface of the substrate when the resist pattern is actually formed. The method for peeling the protective film is not limited to the above condition (1).

[4-1] Protective film remover:
The protective film remover used in the resist pattern forming method of the present invention is a protective film remover that satisfies the above condition (1). For example, when the protective film remover is brought into contact with the protective film for 60 seconds, the photoresist is removed. The film has a solubility that peels off the protective film on the surface of the film, and further dissolves the photoresist film so that 98% or more remains with respect to the film thickness before the protective film is peeled (initial film thickness). The solubility of the photoresist film dissolved in the stripping solution is less than 2% with respect to the initial film thickness of the photoresist film.

  On the surface of the photoresist film, an intermixing layer in which the photoresist film and the protective film are intermixed is formed. By removing the protective film with such a protective film removing liquid, the intermixing layer is formed. The layer can be peeled off at the same time as the protective film, and the deterioration of the lithography performance caused by the intermixing layer can be suppressed. Although the thickness of the intermixing layer as described above varies depending on the material constituting the photoresist film and the protective film, it is usually formed with a thickness of less than 2% with respect to the initial film thickness of the photoresist film. ing.

  As such a protective film remover, a preferable example is one made of an organic solvent. The organic solvent used for removing the protective film varies depending on the composition of the protective film, but monohydric alcohols, esters, ethers, linear or cyclic ketones, alkylene glycol monoalkyl ether acetates, alkylene glycol monoalkyl ethers, It preferably contains at least one organic solvent selected from the group consisting of alkyl lactates and γ-butyrolactone. Such an organic solvent is preferable because the intermixing layer of the photoresist film and the protective film can be peeled off together with the protective film in addition to the excellent solubility of the protective film. In particular, by using such an organic solvent, the protective film can be easily peeled off from the surface of the photoresist film together with the intermixing layer before the development step, so that a watermark defect or a pattern defect defect It is possible to form a high-resolution resist pattern while effectively suppressing the occurrence of.

  As monohydric alcohols, 2-methyl-1-propanol, n-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, n-hexanol, cyclohexanol, 2 -Methyl-2-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2 -Methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2- Pentanol, 2-ethyl-1-butanol, 2,2-dimethyl-3-pentanol, 2,3-dimethyl-3-pentanol, 2,4-dimethyl Lu-3-pentanol, 4,4-dimethyl-2-pentanol, 3-ethyl-3-pentanol, 1-heptanol, 2-heptanol, 3-heptanol, 2-methyl-2-hexanol, 2-methyl -3-hexanol, 5-methyl-1-hexanol, 5-methyl-2-hexanol, 2-ethyl-1-hexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, 1-octanol, 2 -Octanol, 3-octanol, 2-propyl-1-pentanol, 2,4,4-trimethyl-1-pentanol, 2,6-dimethyl-4-heptanol, 3-ethyl-2,2-dimethyl-1 -Pentanol, 1-nonanol, 2-nonanol, 3,5,5-trimethyl-1-hexanol, 1-decanol, 2-decano Le, 4-decanol, 3,7-dimethyl-1-octanol, 3,7-dimethyl-3-octanol can be exemplified.

  Esters include ethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, 2- Examples include methyl hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate and the like.

  Examples of the solvent containing ethers include diethyl ether, dipropyl ether, diisopropyl ether, butyl methyl ether, butyl ethyl ether, butyl propyl ether, dibutyl ether, diisobutyl ether, tert-butyl methyl ether, tert-butyl ethyl ether, tert- Butyl propyl ether, di-tert-butyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, dioctyl ether, cyclopentyl methyl ether, cyclohexyl methyl ether, cyclododecyl methyl ether, cyclopentyl ethyl ether, cyclohexyl ethyl ether, cyclopentyl propyl ether, cyclopentyl- 2-propyl ether, cyclohexylpropyl ether, cycl Hexyl-2-propyl ether, cyclopentyl butyl ether, cyclopentyl-tert-butyl ether, cyclohexyl butyl ether, cyclohexyl-tert-butyl ether, bromomethyl methyl ether, iodomethyl methyl ether, α, α-dichloromethyl methyl ether, chloromethyl ethyl ether, 2 -Chloroethyl methyl ether, 2-bromoethyl methyl ether, 2,2-dichloroethyl methyl ether, 2-chloroethyl ethyl ether, 2-bromoethyl ethyl ether, (±) -1,2-dichloroethyl ethyl ether, di -2-bromoethyl ether, 2,2,2-trifluoroethyl ether, chloromethyl octyl ether, bromomethyl octyl ether, di-2-chloroethyl ether , Ethyl vinyl ether, butyl vinyl ether, allyl ethyl ether, allyl propyl ether, allyl butyl ether, diallyl ether, 2-methoxypropene, ethyl-1-propenyl ether, 1-methoxy-1,3-butadiene, cis-1-bromo-2 -Ethoxyethylene, 2-chloroethyl vinyl ether, allyl-1,1,2,2-tetrafluoroethyl ether and the like can be mentioned.

  Examples of chain and cyclic ketones include 2-butanone, 2-pentanone, 3-methyl-2-butanone, 2-hexanone, 4-methyl-2-pentanone, 3-methyl-2-pentanone, 3,3-dimethyl Examples include 2-butanone, 2-heptanone, 2-octanone, cyclopentanone, 3-methylcyclopentanone, cyclohexanone, 2-methylcyclohexanone, 2,6-dimethylcyclohexanone, and isophorone.

  As propylene glycol monoalkyl ether acetates, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol mono-n-propyl ether acetate, propylene glycol mono-i-propyl ether acetate, propylene glycol mono-n-butyl ether Examples include acetate, propylene glycol mono-i-butyl ether acetate, propylene glycol mono-sec-butyl ether acetate, propylene glycol mono-t-butyl ether acetate, and the like.

  Examples of alkylene glycol monoalkyl ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol And mono-n-propyl ether.

  Moreover, as a protective film peeling liquid, what consists of an organic solvent whose boiling point is 100 degreeC or more can be used suitably, and what consists of an organic solvent whose boiling point is 120 degreeC or more can be used more suitably. When removing the protective film using the protective film removing liquid in the resist pattern forming method of the present invention, the protective film is retained for a predetermined time in a state where the protective film peeling liquid is accumulated on the protective film, and then the protective film is dissolved. The protective film remover is shaken off. For this reason, for example, when the boiling point of the protective film remover is less than 100 ° C., the protective film remover evaporates not a little while the protective film remover is being accumulated and retained, There is a possibility that the concentration of the protective film in the film remover may fluctuate. In such a case, defects due to defective peeling of the protective film may occur.

  As described above, by using an organic solvent having a boiling point of 100 ° C. or higher as the protective film stripping solution, it is easy to keep the amount of the protective film stripping solution constant, and the protective film can be stripped uniformly. Furthermore, since the evaporation amount of the protective film removing liquid is reduced, it is possible to secure a sufficient time for the protective film removing liquid to be accumulated and retained, so that the protective film can be peeled off more satisfactorily.

  Examples of suitable protective film stripping liquids include monohydric alcohols, esters, ethers, chain or cyclic ketones, and alkylene glycol monoalkyl ether acetates.

  The protective film remover used in the resist pattern forming method of the present invention is not limited to the organic solvent described above, and may be any as long as it exhibits solubility satisfying the above condition (1). For example, in addition to the above organic solvent, an alkaline solution satisfying the solubility according to the above condition (1) may be used. Moreover, this protective film peeling liquid can use the solvent demonstrated until now individually or in mixture of 2 or more types.

  Moreover, the organic solvent which comprises a protective film peeling liquid may contain an acid. In this case, it is preferable to use a compound having a dissociation constant (pKa) of 5 or less as the acid. A compound having a dissociation constant (pKa) exceeding 5 may cause problems such as the cross-sectional shape of a resist pattern after development being capped.

The compound having a dissociation constant (pKa) of 5 or less is preferably an organic acid, more preferably a sulfonic acid having a sulfo group (—SO ₂ OH) or a carboxylic acid having a carboxyl group in the molecule, and particularly preferably a sulfonic acid. Sulfonic acids can be suitably used because they have a low dissociation constant (pKa) and high acidity.

  Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, isopropanesulfonic acid, butanesulfonic acid, isobutanesulfonic acid, 1,1-dimethylethanesulfonic acid, pentanesulfonic acid, 1-methylbutanesulfonic acid, Alkylsulfonic acids such as 2-methylbutanesulfonic acid, 3-methylbutanesulfonic acid, neopentanesulfonic acid, hexanesulfonic acid, hebutanesulfonic acid, octanesulfonic acid, nonanesulfonic acid, decanesulfonic acid; benzenesulfonic acid, 2 -Toluenesulfonic acid, 3-toluenesulfonic acid, 4-toluenesulfonic acid, 4-ethylbenzenesulfonic acid, 4-propylbenzenesulfonic acid, 4-butylbenzenesulfonic acid, 4- (t-butyl) benzenesulfonic acid, 2, 5-dimethylbenze Sulfonic acid, 2-mesitylenesulfonic acid, 2,4-dinitrobenzenesulfonic acid, 4-chlorobenzenesulfonic acid, 4-bromobenzenesulfonic acid, 4-fluorobenzenesulfonic acid, 2,3,4,5,6-pentafluoro Arylsulfonic acids such as benzenesulfonic acid, 4-hydroxybenzenesulfonic acid, 4-sulfobenzoic acid and 4-sulfoaniline, aralkylsulfonic acids such as benzylsulfonic acid and phenethylsulfonic acid; cyclic sulfonic acids such as camphorsulfonic acid; Etc. The organic solvent used for peeling off the protective film may contain one acid alone or may contain two or more acids.

[4-2] Method for removing protective film:
When removing the protective film with the protective film removing liquid described above, the protective film removing liquid is protected in a state where a photoresist film is formed on the surface of the substrate and a protective film is further formed on the surface of the photoresist film. The protective film is peeled off in contact with the film.

  The method for removing the protective film is not particularly limited, but a method that does not impair the resist pattern forming ability of the photoresist film is preferable. Specifically, before developing a photoresist film having a protective film formed on its surface, a protective film stripping solution is placed on the protective film with a paddle and allowed to stand for 60 seconds, and the stripping solution is rotated and removed. The protective film is preferably peeled off from the surface of the photoresist film. By constituting in this way, the protective film is completely peeled off, and more than 98% of the photoresist film remains with respect to the initial film thickness, that is, the surface of the photoresist film is 2% of the initial film thickness. It can be dissolved within the range.

  After removing the protective film with the protective film remover of the present invention, after dissolving the intermixing layer formed on the surface side of the photoresist film, the photo film should not be eroded more than necessary. It is preferable to quickly remove the protective film remover from the surface of the resist film.

[5] Step (e) (Development):
In the resist pattern forming method of the present invention, after performing step (d) or simultaneously with step (d), the exposed photoresist film is developed as step (e) to form a resist pattern. . This step (e) (development) is, for example, in the case of a photoresist film obtained from a radiation-sensitive resin composition containing an acid-dissociable group-modified alkali-soluble resin and a radiation-sensitive acid generator. Development can be performed with an alkali developer.

  Examples of the alkali developer include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, dimethyl. Ethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7-undecene, 1,5-diazabicyclo- [4 .3.0] It is preferable to use an alkaline aqueous solution in which at least one alkaline compound such as 5-nonane is dissolved. Especially, the aqueous solution of tetraalkyl ammonium hydroxide can be used suitably.

  The concentration of the alkaline aqueous solution is preferably 10% by mass or less, more preferably 1 to 10% by mass, and particularly preferably 2 to 5% by mass. When the concentration of the alkaline aqueous solution is 10% by mass or less, it is preferable to prevent the non-exposed portion from being dissolved in the alkaline developer.

  An appropriate amount of a surfactant may be added to the alkaline developer. The addition of the surfactant has the advantage that the wettability of the developer with respect to the resist can be enhanced.

  The development is performed, for example, by immersing the exposed photoresist film in an alkaline developer. Usually, after development, the alkaline developer is washed away by washing with water and dried to form a resist pattern.

  Hereinafter, the method for producing a resist pattern formed body of the present invention will be described more specifically with reference to examples. However, these examples merely show some embodiments of the present invention. That is, the present invention should not be interpreted as being limited to these examples.

[Synthesis Example 1]:
First, an acid dissociable group-modified alkali-soluble resin for forming a photoresist film was synthesized by the following method.

The following compound (M-1) 53.93 g (50 mol%), compound (M-2) 35.38 g (40 mol%), compound (M-3) 10.69 g (10 mol%) A monomer solution was prepared by dissolving in 200 g of butanone and further adding 5.58 g of dimethyl 2,2′-azobis (2-methylpropionate). Meanwhile, 100 g of 2-butanone was charged into a 500 ml three-necked flask and purged with nitrogen for 30 minutes. After the nitrogen purge, the inside of the three-necked flask was heated to 80 ° C. while stirring the reaction kettle, and the monomer solution prepared in advance was added dropwise over 3 hours using a dropping funnel. The polymerization start was carried out for 6 hours with the start of dropping as the polymerization start time.

After completion of the polymerization reaction, the polymerization solution was cooled to 30 ° C. or less by water cooling, the cooled polymerization solution was put into 2000 g of methanol, and the precipitated white powder was separated by filtration. After repeating the operation of adding 400 g of methanol to the filtered white powder and washing in a slurry state twice, the white powder was again filtered and dried at 50 ° C. for 17 hours to obtain a white powder polymer. Obtained (74 g, 74% yield). This polymer has Mw of 6900, Mw / Mn = 1.70, and as a result of ¹³ C-NMR analysis, each repeating unit derived from compound (M-1), compound (M-2), and compound (M-3). Was a copolymer (acid dissociable group-modified alkali-soluble resin) having a content ratio of 53.0: 37.2: 9.8 (mol%). In addition, content of the low molecular weight component derived from each monomer in this polymer was 0.03 mass% with respect to 100 mass% of this polymer.

[Synthesis Example 2]:
Next, a fat-soluble resin for forming a protective film was synthesized by the following method.

  A monomer solution in which 93.91 g (85 mol%) of methacrylic acid (1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl) ester was previously dissolved in 50 g of isopropanol (1 And a monomer solution (2) prepared by dissolving 6.09 g (15 mol%) of vinyl sulfonic acid in 50 g of isosopropanol. On the other hand, 6.91 g of 2,2′-azobis- (methyl 2-methylpropionate) (polymerization initiator) and 200 g of isopropanol were charged into a 500 ml three-necked flask equipped with a thermometer and a dropping funnel, and nitrogen was added for 30 minutes. Purged. After the nitrogen purge, the inside of the flask was heated to 80 ° C. while stirring with a magnetic stirrer, and the monomer solution (1) prepared in advance was added dropwise over 20 minutes using a dropping funnel. After completion of the dropwise addition, the reaction is continued for another 20 minutes, the monomer solution (2) prepared in advance is dropped over 20 minutes, the reaction is continued for another 1 hour, and the mixture is cooled to 30 ° C. or less. A polymerization solution was obtained.

  The copolymer solution was reprecipitated in 4800 g of water, stirred for 30 minutes, and then filtered. The obtained white powder was dissolved in 1000 ml of methanol, 1000 ml of n-heptane was added, and liquid separation was repeated 4 times to wash the lower layer (methanol layer). After substituting the solvent of the lower layer thus obtained with 4-methyl-2-pentanol, water was added and the liquid was separated and washed, and the solvent was replaced with 4-methyl-2-pentanol again. . The solid content concentration of the sample after solvent replacement was calculated from the mass of the residue after placing 0.3 g of the resin solution on an aluminum pan and heating on a hot plate heated to 140 ° C. for 2 hours, and then forming a protective film This was used for the preparation and yield calculation of the coating liquid. Mw, Mw / Mn (dispersion of molecular weight), and yield (mass%) of the obtained copolymer were 5830, 1.7, and 72%, respectively, and methacrylic acid (1,1,1-trimethyl) was obtained. A copolymer (lipid-soluble resin) having a content of 95: 5 (mol%) of each repeating unit derived from (fluoro-2-trifluoromethyl-2-hydroxy-4-pentyl) ester and vinylsulfonic acid there were. Let this polymer be a fat-soluble resin (A-1).

[Synthesis Example 3]:
A homopolymer of methacrylic acid-tricyclo [5.2.1.0 ^2,6 ] dec-7-yl ester was synthesized in the same manner as in Synthesis Example 2. Mw, Mw / Mn (dispersion of molecular weight), and yield (mass%) of the obtained copolymer were 6300, 1.6, and 75%, respectively. Let this polymer be a fat-soluble resin (A-2).

[Preparation of radiation-sensitive resin composition]:
For 100 parts by mass of the acid-dissociable group-modified alkali-soluble resin of Synthesis Example 1, 1.5 parts by mass of triphenylsulfonium nonafluoro-n-butanesulfonate as a radiation-sensitive acid generator, 1- (4-n- 6 parts by mass of butoxynaphthyl) tetrahydrothiophenium trifluoromethanesulfonate, 0.65 parts by mass of Nt-butoxycarbonylpyrrolidine as an acid diffusion inhibitor, 30 parts by mass of γ-butyrolactone as an auxiliary solvent, As a solvent, 2030 parts by mass of propylene glycol monomethyl ether acetate was added, and each component was mixed to obtain a uniform solution. Then, the coating liquid which consists of a radiation sensitive resin composition solution was prepared by filtering using a membrane filter with the hole diameter of 0.2 micrometer (total solid content concentration of about 6 mass%).

[Preparation of Coating Liquid A for Protective Film Formation]:
4-methyl-2-pentanol is added to 100 parts by mass of the fat-soluble resin (A-1) synthesized in Synthesis Example 2 to adjust the total solid content concentration to 3.5% by mass, and the pore size is adjusted to 0. A coating solution for forming a protective film was prepared by filtering with a 2 μm filter.

[Preparation of protective film-forming coating solution B]:
Butyl acetate is added to 100 parts by mass of the fat-soluble resin (A-2) synthesized in Synthesis Example 3, the total solid concentration is adjusted to 3.5% by mass, and the mixture is filtered through a filter having a pore size of 0.2 μm. Thus, a coating solution for forming a protective film was prepared.

[Preparation of protective film stripping solution A]:
A protective film remover A was prepared by mixing 50 parts by mass of diisoamyl ether and 50 parts by mass of 4-methyl-2-pentanol and filtering with a filter having a pore size of 0.2 μm.

[Preparation of protective film stripping solution B]:
70 parts by mass of diisoamyl ether and 50 parts by mass of 4-methyl-2-pentanol were mixed and filtered with a filter having a pore size of 0.2 μm to prepare a protective film removing liquid B.

[Preparation of protective film stripping solution C]:
A protective film stripping solution C was prepared by filtering a 2.38 mass% tetramethylammonium hydroxide aqueous solution through a filter having a pore size of 0.2 μm.

[Evaluation methods]:
The following evaluation was performed using the radiation sensitive resin composition prepared as described above, the coating liquids A and B for forming a protective film, and the protective film removing liquids A to C.

(1) Photoresist film reduction test:
Using a coater / developer (1) (trade name: CLEAN TRACK ACT8, manufactured by Tokyo Electron Ltd.), a coating solution comprising a radiation-sensitive resin composition was spin-coated on an 8-inch silicon wafer, and the coating was performed at 115 ° C. for 60 seconds. By performing PB under the conditions, a 150 nm thick photoresist film was formed. Further, the protective film-forming coating liquid A or B was spin-coated on the surface of the photoresist film, and PB was performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 90 nm. In Example 1 and Comparative Example 1, the protective film-forming coating liquid A was used, and in Example 2, the protective film-forming coating liquid B was used.

  Measures the reduction amount (%) of the photoresist film relative to the initial film thickness (150 nm) of the photoresist film when the protective film formed on the surface of the photoresist film is removed using the protective film removing liquids A to C. did. Table 1 shows the composition of the protective film remover used in each example and comparative example. The evaluation results are shown in Table 1. In Example 1, the protective film remover A was used, in Example 2, the protective film remover B was used, and in Comparative Example 1, the protective film remover C was used.

(2) Forced watermark test:
Using an coater / developer (1) (trade name: CLEAN TRACK ACT8, manufactured by Tokyo Electron Ltd.), an antireflection film forming agent (trade name: ARC29A, manufactured by Brewer Science) is spin-coated on an 8-inch silicon wafer. An antireflection film having a thickness of 77 nm was formed by performing PB under the conditions of 205 ° C. and 60 seconds. Next, the surface of the antireflection film is spin-coated with a coating solution comprising the radiation-sensitive resin composition, and PB is performed at 115 ° C. for 60 seconds to form a 150 nm-thick photoresist film. Formed. Further, the surface of the photoresist film is spin-coated with the same kind of protective film-forming coating solution A or B as in the above-described photoresist film reduction test, and PB is performed at 90 ° C. for 60 seconds. As a result, a protective film having a thickness of 90 nm was formed.

  Next, the photoresist film on which the protective film is formed is exposed with an ArF projection exposure apparatus (trade name: S306C, manufactured by Nikon Corporation) under optical conditions of NA: 0.78, Sigma: 0.85, and 2/3 Ann. A test wafer was prepared. Thereafter, using a pipette, four 0.3 μL water droplets are marked on the surface of the wafer and dried for 10 minutes, and then on the hot plate of the coater / developer (1) at 115 ° C. for 60 seconds. PEB is performed, the protective film is peeled off with each of the protective film peeling liquids A to C shown in Table 1, paddle development is performed with the LD nozzle of the coater / developer (1) for 60 seconds, and then with ultrapure water. Rinse and spin-dry for 15 seconds at 4000 rpm. The resist pattern thus formed was visually observed, and a case where no droplet mark (watermark) remained at the position where the waterdrop was marked with a pipette was judged as “good”, and a case where it remained was judged as “bad”. The results are shown in Table 1.

(3) Pattern defect defect inspection:
Using a coater / developer (2) (trade name: CLEAN TRACK ACT12, manufactured by Tokyo Electron Ltd.), an antireflection film forming agent (trade name: ARC29A, manufactured by Brewer Science Co., Ltd.) is spin-coated on a 12-inch silicon wafer. An antireflection film having a thickness of 77 nm was formed by performing PB under the conditions of 205 ° C. and 60 seconds. A resist pattern was formed using this as a substrate, and the presence or absence of defective defects in the pattern was inspected.

  In forming the resist pattern, first, a radiation sensitive resin composition was spin coated on the surface of the substrate, and PB was performed at 115 ° C. for 60 seconds to form a 150 nm thick photoresist film. The surface of the photoresist film is spin-coated with a protective film forming coating solution A or B as shown in Table 1, and PB is performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 90 nm. Formed.

  Using the ArF excimer laser exposure apparatus (trade name: TWIN SCAN XT1250i, manufactured by ASML, certification condition; NA 0.85, sigma 0.93 / 0.69), the photoresist film thus formed with the protective film is used. And exposure through a mask pattern.

  In Examples 1 and 2, PEB is then performed on the hot plate of the same coater / developer (2) at 115 ° C. for 90 seconds, and the protective film is removed with the protective film removing liquid shown in Table 1. Then, paddle development was performed for 30 seconds with the LD nozzle of the same coater / developer (2), rinsed with ultrapure water, and then shaken off at 3000 rpm for 15 seconds and spin-dried.

  Regarding Comparative Example 1, PEB was performed under the same conditions as in Example 1 without peeling off the protective film, and then the protective film was peeled off using a protective film peeling solution C during alkali development of the photoresist film.

  The resist pattern thus formed is subjected to a defect inspection of the wafer using a general name: defect inspection apparatus (trade name: KLA2351, manufactured by KLA-Tencor), and the detected defects are detected by a scanning electron microscope ( The product name: S-9360 (manufactured by Hitachi Keiki Co., Ltd.) was observed to confirm the presence of pattern defect defects (specifically, pattern thinning or thickening defects). Those in which this pattern defect defect was detected were defined as “defective”, and those in which the pattern defect was not detected were defined as “good”. The results are shown in Table 1.

[Evaluation results]:
As is clear from the data in Table 1, in Examples 1 and 2 in which a resist pattern was formed using the protective film stripping solutions A and B exhibiting solubility satisfying the above condition (1), water was measured by a forced watermark test. It was suggested that there were few mark defects and the resist shape was also good.

  In the resist pattern forming method of the present invention, the photoresist film is exposed from the immersion liquid in the immersion exposure in which the photoresist film is irradiated with radiation in the state where the immersion liquid is interposed and the photoresist film is exposed. The protective film for protection can be peeled off favorably to form a finer resist pattern with high resolution. In addition, it is possible to effectively suppress the occurrence of watermark defects and pattern defect defects caused by water droplets remaining on the protective film and the above-described intermixing layer. Therefore, it can be suitably used in the field of microfabrication, particularly in the manufacture of integrated circuit elements such as semiconductor devices in which miniaturization, high definition, and high integration are rapidly progressing.

Claims (4)

In this resist pattern forming method, a photoresist film is exposed to radiation in a state where a liquid (immersion liquid) having a higher refractive index than air is interposed, thereby exposing the photoresist film to form a resist pattern. And
Forming the photoresist film on the surface of the substrate (a),
Forming a protective film resistant to the immersion liquid on the surface of the photoresist film (b),
Irradiating the photoresist film with radiation in the state of interposing the immersion liquid (c),
A step (d) of peeling the protective film from the surface of the photoresist film using a protective film remover that satisfies the following condition (1);
And a step (e) of developing the exposed photoresist film.
Condition (1): The photoresist film having a thickness of 150 nm is formed on the surface of the substrate, the protective film having a thickness of 90 nm is further formed on the surface of the photoresist film, and the protective film removing liquid is used as the protective film. When the contact is made for 60 seconds, the protective film is peeled off and the photoresist film is dissolved so as to remain in a thickness of 147 nm or more.   The resist pattern forming method according to claim 1, wherein an organic solvent is used as the protective film stripping solution.   The resist pattern forming method according to claim 2, wherein the protective film stripping solution is made of the organic solvent having a boiling point of 100 ° C. or higher.   The protective film remover comprises monohydric alcohols, esters, ethers, chain or cyclic ketones, alkylene glycol monoalkyl ether acetates, alkylene glycol monoalkyl ethers, alkyl lactates, and γ-butyrolactone. The method for forming a resist pattern according to claim 2, wherein a resist pattern containing at least one organic solvent selected from the group is used.