WO2007125971A1

WO2007125971A1 - Method of forming resist pattern

Info

Publication number: WO2007125971A1
Application number: PCT/JP2007/058978
Authority: WO
Inventors: Hiroki Nakagawa; Hiromitsu Nakashima; Atsushi Nakamura; Motoyuki Shima
Original assignee: Jsr Corporation
Priority date: 2006-04-27
Filing date: 2007-04-25
Publication date: 2007-11-08
Also published as: TW200804989A; JPWO2007125971A1

Abstract

A method of forming a resist pattern through the liquid immersion exposure step of irradiating a photoresist film in the presence of a liquid with refractive index higher than that of air (immersion liquid) with radiation to thereby attain exposure of the photoresist film, comprising forming the photoresist film on a substratum surface; forming a protective film resistant to the immersion liquid on the surface of the photoresist film; in the presence of the immersion liquid, irradiating the photoresist film with radiation to thereby attain exposure of the photoresist film; detaching the protective film from the surface of the photoresist film; and thereafter carrying out exposure, heating treatment and development, thereby obtaining a resist pattern.

Description

Resist pattern forming method

Technical field

The present invention relates to a method for forming a resist pattern that is suitably used in the field of microfabrication including the manufacture of integrated circuits. Specifically, the present invention relates to a resist pattern forming method using immersion exposure, which is a lithography technique capable of forming a finer resist pattern with higher resolution.

Background art

In recent years, miniaturization of integrated circuits has been progressing steadily. 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 formula (i) and the following formula (ii), and the wavelength of the radiation λ serving as the exposure light source is short. The larger the numerical aperture ΝΑ, the smaller the resolution R (minimum resolution dimension), and the resolution can be improved. Accordingly, in the projection exposure apparatus, the exposure light source has a shorter wavelength and a projection lens has a higher numerical aperture.

R = kl-λ / ΝΑ: (i)

^{δ = k2- λ / ΝΑ 2:} (ii)

(Where R: resolution, δ: depth of focus, λ: wavelength of exposure light source, 光源: numerical aperture of projection lens, kl, k2: process coefficient)

[0003] Apart from this, a technique called immersion exposure is also known as a lithography technique for improving the resolution. Immersion exposure is a technique for exposing a photoresist film by irradiating the photoresist film with a liquid having a refractive index higher than that of air (immersion liquid). That is, 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.

[0004] The resolution R and depth of focus δ when the space between the projection lens and the photoresist film is filled with an immersion liquid having a refractive index n is expressed by the following formula (iii) and the following formula (iv). It is. In other words, by using an immersion liquid with a refractive index n, the value of resolution R (minimum resolution dimension) is lZn. In addition to improving the resolution, the depth of focus δ can be expanded and improved by η times. It becomes possible. For example, when an ArF excimer laser (wavelength λ: 193 nm) is used as the light source and water with a refractive index η at the wavelength λ of 1.44 is used as the immersion liquid, non-immersion with air or nitrogen interposed. Compared to the case, the resolution R (minimum resolution dimension) is improved to 1Z1.44 (69.4%), and the depth of focus δ is expanded by 1.44 times.

R = kl-(λ / η) / ΝΑ: (iii)

δ = k2-n l / NA ² : (iv)

(However, n: Refractive index, R, δ, λ, ΝΑ, kl, k2! / Is synonymous with the proviso of formula (i) and formula (ii))

[0005] Such immersion exposure technology is considered to be an indispensable technique as lithographic technology for microfabrication, in particular, lOnm unit microfabrication, and is already a projection exposure apparatus for immersion exposure. Is also disclosed (see, for example, Patent Document 1).

[0006] However, in immersion exposure, since the immersion liquid directly contacts the photoresist film, an unexpected chemical reaction is caused by the immersion liquid that has penetrated the photoresist film. It has been pointed out that there is a possibility of adversely affecting the performance (for example, see Patent Document 2).

[0007] Therefore, immersion exposure is performed in a state in which a protective film resistant to the immersion liquid is formed on the surface of the photoresist film, and then the post-exposure heat treatment is performed and then the protective film is peeled off. A resist pattern forming method has been proposed (see, for example, Patent Documents 3 and 4).

Patent Document 1: Japanese Patent Application Laid-Open No. 11 176727

Patent Document 2: JP 2005-268382 A

Patent Document 3: Japanese Patent Laid-Open No. 2005-250511

Patent Document 4: Japanese Patent Laid-Open No. 2005-264131

Disclosure of the invention

[0009] However, the resist pattern forming method described in Patent Documents 3 and 4 is a defect that penetrates the protective film and causes droplet marks on the resist pattern due to the remaining immersion liquid. There is a problem that a defect (no turn defect defect) in which the width of the resist pattern or the width of the resist pattern becomes thick or conversely narrow may occur. That is, the resist pattern forming method described in Patent Documents 3 and 4 forms a high-resolution resist pattern. Although it can be expected, there has been a demand for further improvements that are still not fully satisfactory in that watermark defects and pattern defect defects may occur.

[0010] As described above, at present, no measures have yet been disclosed that can form a high-resolution resist pattern while effectively suppressing the occurrence of watermark defects and pattern defect defects. Such a policy is eagerly desired.

[0011] The present invention has been made to solve the above-described problems of the prior art, and effectively suppresses the occurrence of water mark defects and pattern defect defects, while providing a high-resolution resist pattern. The present invention provides a method for forming a resist pattern that can form a film.

[0012] As a result of intensive studies to solve the problems of the prior art as described above, the present inventors

, After the exposure of the photoresist film, after the exposure of the photoresist film, before the post-exposure heat treatment (PEB), the protective film is peeled off in advance, and then the post-exposure heat treatment, The inventors have conceived that the above-mentioned problems can be solved by developing, and have completed the present invention. Specifically, the present invention provides the following resist pattern forming method.

[0013] [1] Immersion exposure process in which a photoresist film is exposed by irradiating the photoresist film with a liquid (immersion liquid) having a refractive index higher than that of air. A method for forming a resist pattern comprising: forming the photoresist film on a surface of a substrate; forming a protective film resistant to the immersion liquid on the surface of the photoresist film; By irradiating the photoresist film with radiation in a state of interposing a liquid, the photoresist film is exposed, and after the protective film is peeled off from the surface of the photoresist film, a post-exposure heat treatment and A resist pattern forming method for developing and obtaining a resist pattern.

[2] The resist pattern forming method according to [1], wherein the protective film is formed of a fat-soluble resin and the protective film is peeled off using an organic solvent.

[0015] [3] The fat-soluble resin forming the protective film is represented by the following general formula (1) and the following general formula (

2) a polymer containing at least one repeating unit selected from the group consisting of The method for forming a resist pattern according to the above [2].

[Chemical 1]

[In the general formula (1) or (2), R ¹ is hydrogen, methyl group or trifluoromethyl group, R ² is a divalent organic group, R ³ is alicyclic carbonization having 4 to 20 carbon atoms. Indicates a hydrogen group or a derivative thereof. ]

The resist pattern forming method of the present invention can form a high-resolution resist pattern while effectively suppressing the occurrence of watermark defects and pattern defect defects.

BEST MODE FOR CARRYING OUT THE INVENTION

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 having the invention-specific matters, and is not limited to the embodiments described below. In this specification, “(meth) acrylic acid ester” means a concept including both acrylic acid ester and methacrylic acid ester.

[0018] The resist pattern forming method of the present invention has a refractive index higher than that of air! An immersion exposure process in which a photoresist film is irradiated with radiation through a liquid (immersion liquid) to expose the photoresist film. A resist pattern forming method comprising: forming a photoresist film on the surface of the substrate; forming a protective film resistant to the immersion liquid on the surface of the photoresist film; By irradiating with radiation, the photoresist film is exposed and the protective film is peeled off from the surface of the photoresist film, followed by post-exposure heat treatment and development to form a resist pattern. [1] Formation of photoresist film:

In the resist pattern forming method of the present invention, first, a photoresist film is formed on the surface of the substrate.

[0020] [1 1] Board:

As the substrate, silicon wafers, silicon wafers coated with aluminum, and the like are usually used. In order to maximize the characteristics of the photoresist film, it is also a preferable form to form an organic or inorganic antireflection film on the surface of the substrate in advance. (See 12452).

[0021] [1 2] Photoresist film (radiation-sensitive resin composition):

There are no particular restrictions on the type of material that forms the photoresist film. Conventionally, the material used to form the photoresist film is appropriately selected according to the intended use of the resist. Bho.

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 composition containing an acid-dissociable group-modified alkali-soluble resin (A component) and a radiation-sensitive acid generator (component B) as essential components is used. Examples thereof include a resin composition. In such a rosin composition, an acid is generated from the acid generator by irradiation (exposure), and the acid group (for example, carboxyl group) of the rosin is protected by the action of the generated acid. The acid dissociable group is dissociated to expose the acidic group. 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.

[0023] [1-2A] Acid-dissociable group-modified alkali-soluble rosin (component A):

The “acid-dissociable group-modified alkali-soluble resin” is an oil having an acidic group and at least a part of the acidic group being protected by the acid-dissociable group. This rosin may be insoluble in alkali or hardly soluble in alkali when at least some of the acidic groups in the rosin are protected by an acid dissociable group, but the acid dissociable group is dissociated by the action of an acid. As a result, the acid group is exposed and the resin is alkali-soluble.

[0024] "Alkali insoluble or hardly alkali-soluble" means acid-dissociable group-modified alkali-soluble Alkali development conditions used when forming a resist pattern from a photoresist film obtained with a radiation-sensitive resin composition containing a resin (component A) and a radiation-sensitive acid generator (component B) In the following, when a film obtained only with an acid-dissociable group-modified alkali-soluble resin is developed instead of the photoresist film, it means that 50% or more of the initial film thickness of the film remains after development. .

[0025] 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 or a sulfonic acid group can be mentioned. Of these, a phenolic hydroxyl group, a carboxyl group, and the like are preferable because they are highly effective in improving the solubility in alkali. The acid-dissociable group-modified alkali-soluble resin may have only one acidic group, or may have two or more acidic groups.

[0026] The specific structure corresponding to the acid dissociable group contained in the component A is, for example, a repeating unit containing a skeleton represented by the following general formula (3) (hereinafter referred to as "repeating unit (1)") )) As essential units.

[Chemical 2]

[In the general formula (3), each R ⁴ is the same or different and is a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof, linear or branched having 1 to 4 carbon atoms. R ⁴ may be bonded to each other to form an alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof. However, R ⁴ includes at least one alicyclic hydrocarbon group or a derivative thereof, or R ⁴ is bonded to each other to form an alicyclic hydrocarbon group having 4 to 20 carbon atoms. It shall include a structure in which a derivative is formed. ]

[0027] Among the skeletons represented by the general formula (3), the component A preferably includes skeletons represented by the following general formulas (3a) to (3d).

[Chemical 3]

(3a) (3b) (3c) (3d)

[In the above general formulas (3a) to (3d), R ⁵ is the same or different and is a linear or branched alkyl group having 1 to 4 carbon atoms, and m is 0 or 1. ]

[0028] The main chain structure of the repeating unit (1) is not particularly limited, but is preferably a (meth) acrylate ester or _a trifluoroacrylate ester structure.

[0029] 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) atallylic acid 1— ( Bicyclo [2. 2. 1] hepto-2-yl) -1-methylethyl ester, (meth) acrylic acid 1- (adamantane-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, (meth) acrylic acid 1-ethyl-1- Shi Hexyl ester, and the like is preferable to Russia! /,.

[0030] In the state where at least a part of the acidic group is protected by the acid-dissociable group, it exhibits alkali insolubility or alkali-solubility, but when the acid-dissociable group is dissociated by the action of an acid, the acid group The structure of the component A is not particularly limited as long as it has a property of being exposed to alkali solubility. 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.

[0031] 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). May be or repeat It may be a polymer containing a repeating unit other than the repeating unit (1) other than the repeating unit (1)! / ヽ. The content of the repeating unit (1) is usually from 0 to 70 mol%, preferably from 15 to 60 mol%, more preferably from 20 to 50 mol%, based on all repeating units. I like it. If the content of the repeating unit (1) exceeds 70 mol%, the exposure margin may be deteriorated.

[0032] It should be noted that the polymer constituting the component A need not have all of the acidic groups protected by the acid-dissociable group, provided that at least a part of the acidic groups is protected by the acid-dissociable group.ヽ. The rate of introduction of acid-dissociable groups (ratio of the number of acid-dissociable groups to the total number of acid groups and acid-dissociable groups in the polymer constituting component A) is the type and base of acid-dissociable groups Varies depending on the type of polymer. However, the introduction rate is preferably in the range of 5 to: LOO%, and more preferably in the range of 10 to 100%.

[0033] The molecular weight range of the polymer constituting the component A is not particularly limited, and may be various molecular weight ranges 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 is 1,000 to 30,000. More preferably, it is more preferably 1,000 to 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 lowered.

[0034] The ratio (MwZMn) between the polystyrene-equivalent mass average molecular weight Mw and the polystyrene-equivalent number average molecular weight (may be referred to as "Mn") measured by GPC is not particularly limited. In various molecular weight ranges. The value of MwZMn is usually 1 to 5, and preferably 1 to 3. By setting this range, it is possible to obtain a resist with excellent resolution.

[0035] [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 upon irradiation (exposure), and by the action of the generated acid, the acid-dissociable group that protected the acidic group (for example, carboxyl group) of the resin is dissociated to form an acidic group. To expose. Therefore, it is possible to improve the alkali solubility of the exposed portion of the resist and form a positive resist pattern by alkali development.

[0036] The structure of the component B is not particularly limited as long as it has the above properties. Therefore, it is only necessary to appropriately select materials that have been used for such purposes according to the purpose. For example, salt salts such as ododonium salt, sulfonium salt, phosphonium salt, diazo-um salt, pyridinium salt; haloalkyl group-containing hydrocarbon compound, haloalkyl group-containing heterocycle Halogen-containing compounds such as formula compounds; 1,3-diketo-2-diazo compounds, diazobenzoquinone compounds, diazoketone compounds such as diazonaphthoquinone compounds; j8-ketosulfone, 13-sulfolsulfone, and these Sulfonic compounds such as a-diazoic compounds of compounds, sulfonic acid compounds; and the like can be used.

[0037] Among them, it is preferable to use a sulfo-um salt having a structure represented by the following general formula (4).

[Chemical 4]

[In the general formula (4), R ⁶ 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 alkoxy group having 1 to 10 carbon atoms. Group, carbon number 2 to: L 1 represents a linear or branched alkoxycarbonyl group of R 1, R ⁷ represents a linear or branched alkyl group having 1 to 10 carbon atoms, an alkoxyl group, a carbon number 1 to 10 linear, branched and cyclic alkanesulfonyl groups are represented, and r represents an integer of 0 to 10. R ⁸ is the same or different and each represents a linear or branched alkyl group having 1 to 10 carbon atoms, an optionally substituted phenyl group, or an optionally substituted naphthyl group; ⁸ 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 ⁹ 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. ]

[0038] As the component B, the various acid generators described above may be used alone or in combination of two or more. Yes. The blending amount of the B component may be appropriately set according to the properties desired to be imparted to the resist. 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, sensitivity and developability tend to decrease. On the other hand, when the amount exceeds 20 parts by mass, the transparency to radiation is lowered, and it tends to be difficult to obtain a rectangular resist pattern.

[0039] [1-2C] Additive:

In the radiation-sensitive oil composition, if necessary, additives other than the component A and component B, such as an acid diffusion controller, an alicyclic additive having an acid-dissociable group, a sensitizer, an interface An activator or the like may be blended.

[0040] The "acid diffusion inhibitor" has an action of controlling an undesired chemical reaction in a non-exposed region by controlling a diffusion phenomenon in the photoresist film of an acid that is generated by an acid generator isotropic force upon exposure. It is an additive. By adding an acid diffusion inhibitor, the storage stability of the radiation-sensitive rosin composition can be improved. Further, by adding an acid diffusion inhibitor, it is possible to improve the resolution of the resist, and it is possible to suppress the change in the line width of the resist pattern due to the fluctuation of the exposure time (PED) until the development process. As a result, there is an advantage that a radiation-sensitive resin composition having extremely excellent process stability can be obtained.

[0041] The acid diffusion inhibitor is preferably a nitrogen-containing organic compound whose basicity does not change by exposure or heat treatment during the resist pattern formation process. Examples of nitrogen-containing organic compounds include tertiary amine compounds such as alkylamines, cycloalkylamines, aromatic amines, alkanolamines, and N-t butoxycarbonyl group-containing amino compounds. Amide group-containing compounds; Tetra-n-propyl ammonium hydroxide, quaternary ammonium hydroxide compounds such as tetra-n-butyl ammonium hydroxide; Nitrogen-containing heterocyclic compounds such as pyridines, piperazines, imidazoles; Can be mentioned. One of these acid diffusion inhibitors may be used alone, or two or more thereof may be used in combination.

[0042] The amount of the acid diffusion inhibitor is usually 10 parts by mass or less with respect to 100 parts by mass of the component A, and is preferably 0.001 to 10 parts by mass, preferably 0.005 to 5 parts by mass. The power of mass S is more preferable. When the amount of the acid diffusion inhibitor is 10 parts by mass or less, This is preferable because the sensitivity and the developability of the exposed area can be improved. Further, it is preferable that the blending amount of the acid diffusion inhibitor is 0.001 part by mass or more because it is possible to suppress a decrease in pattern shape and dimensional fidelity as a resist depending on process conditions.

[0043] The "alicyclic additive having an acid dissociable group" is a component exhibiting an action of further improving dry etching resistance, pattern shape, adhesion to the substrate, and the like. Examples of the alicyclic additives include: adamantane derivatives such as 1-adamantanecarboxylic acid and 2-adamantanone; deoxycholate esters such as t-butyl deoxycholate, deoxycholate t-butoxycarboromethyl; lithocholic acid t Lithocholic acid esters such as butyl and lithocholic acid butoxycarboxyl methyl; alkyl carboxylic acid esters such as dimethyl adipate and ethyl adipate; 3- [2hydroxy-2,2bis (trifluoromethyl) ethyl] tetracyclo [ 4. 4. 0. 12, 5. 17, 10] Dodecane etc. can be mentioned.

[0044] As the alicyclic additive, one kind may be used alone, or two kinds or more may be used in combination. From the viewpoint of improving the heat resistance of the resist, the compounding amount of the alicyclic additive is preferably 50 parts by mass or less, preferably 30 parts by mass or less, relative to 100 parts by mass of component A. Further preferred. When the blending amount of the alicyclic additive exceeds 50 parts by mass, the heat resistance of the resist tends to be insufficient.

[0045] "Sensitizer" is an agent that absorbs radiation energy and transmits the energy to the B component to increase the amount of acid produced. It has the effect of improving sensitivity.

[0046] Examples of the sensitizer include rubazoles, acetophenones, benzophenones, naphthalenes, phenols, biacetyl, eosin, rose bengal, pyrenes, anthracene, phenothiazines and the like. . One of these sensitizers may be used alone, or two or more thereof may be used in combination. The amount of the sensitizer is preferably 50 parts by mass or less with respect to 100 parts by mass of the component A.

[0047] "Surfactant" is a component having an effect of improving coating properties, streaking, developability and the like. As the surfactant, it is preferable to use a force-on surfactant which can use any of a ionic, cationic, non-ionic or amphoteric surfactant. No Examples of ionic surfactants include polyoxyethylene higher alkyl ethers, polyoxyethylene higher alkyl ethers, polyethylene glycol higher fatty acid diesters, etc., and all of the following trade names are “KP” ( (Shin-Etsu Chemical Co., Ltd.)

, "Polyflow" (manufactured by Kyoeisha Yushi Chemical Co., Ltd.), "F Top" (manufactured by Tochem Products), "MegaFuck" (manufactured by Dainippon Ink & Chemicals), "Florard" (manufactured by Sumitomo 3M), " Examples include Asahi Guard and Surflon (Asahi Glass Co., Ltd.).

[0048] 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 and 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 1 part by mass or less.

[0049] The radiation-sensitive resin composition may be blended with a dye or a pigment in order to visualize the latent image in the exposed area and to reduce the influence of halation during exposure! In order to improve the properties, an adhesion aid may be added. In addition to the above-mentioned additives, antihalation agents, storage stabilizers, antifoaming agents and the like can be mentioned.

[0050] [1— 2D] Solvent:

In addition to the soot component, the B component, and various additives, a solvent may be added to the radiation-sensitive resin composition. By blending the solvent, it is possible to improve the coating property when the radiation-sensitive resin composition is applied to the substrate.

[0051] The type of "solvent" is not particularly limited. For example, linear or branched ketones such as 2 butanone and 3-methyl-2-butanone; cyclic such as cyclopentanone and 3-methylcyclopentanone Ketones; propylene glycol monoalkyl ether acetates such as propylene glycol monomethyl ether acetate; 2-hydroxypropionate alkyls such as methyl 2-hydroxypropionate; 3-alkoxypropionate alkyls such as methyl 3-methoxypropionate In addition, _{Ί butyro} rataton can be mentioned

. These solvents can be used alone or in admixture of two or more.

[0052] [1-3] Formation of photoresist film:

For the photoresist film, for example, a solvent is added to the soot component, the B component, and various additives, the total solid content concentration is adjusted to 5 to 50% by mass, and the solution is filtered through a filter having a pore size of about 30 nm. The coating solution can be prepared by applying the coating solution onto the 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.

[0053] [2] Formation of protective film:

In the method of the present invention, after forming a photoresist film as described above, a protective film resistant to the immersion liquid is formed on the surface of the photoresist film. By forming a protective film, it is possible to prevent immersion liquid force S from coming into direct contact with the photoresist film during immersion exposure, and the lithography performance of the photoresist film may deteriorate due to penetration of the immersion liquid. In addition, it is possible to effectively prevent the lens of the projection exposure apparatus from being contaminated by the components eluted from the photoresist film.

[0054] In addition to being able to form a stable film against an immersion liquid (for example, pure water), the protective film may be formed of a material that can be easily peeled off after immersion exposure. Usually preferred, it is formed by coagulation. “Stable to immersion liquid” means that the change in film thickness measured by the water stability evaluation method described below is within 3% of the initial film thickness.

[0055] [Stability evaluation test]:

(1): Coater Z developer (1) (trade name: CLEAN TRACK ACT8, manufactured by Tokyo Electton Co., Ltd.) is used to apply a protective film-forming coating solution (protective film-forming resin) on an 8-inch silicon wafer. A 90 nm thick protective film is formed by spin coating with a solvent dissolved in a solvent and performing PB at 90 ° C for 60 seconds. The film thickness (initial film thickness) of this protective film is measured using an optical interference type film thickness measuring device (trade name: Lambda Ace VM—2010, manufactured by Dainippon Screen Mfg. Co., Ltd.).

(2): Next, rinse nozzle force of the coater Z developer (1) on the surface of the wafer on which the protective film is formed. After ultrapure water is discharged for 60 seconds, it is spun off for 15 seconds at 4000 rpm and spinned. Dry. The thickness of the protective film at this time is measured again, and the change in the thickness of the protective film (reduced film thickness) is calculated. The ratio of the reduced film thickness to the initial film thickness is within 3%. It is evaluated as “stable against immersion liquid”.

[0056] The structure or the like of the resin for forming the protective film (protective film forming resin) is not particularly limited as long as it has the above properties. Therefore, the resin for forming a protective film may be appropriately selected from resins conventionally used for such applications according to the purpose. However, in the method of the present invention, it is preferable to use a fat-soluble resin as the protective film-forming resin. If the protective film is formed of a fat-soluble resin, the protective film can be peeled off using an organic solvent. After immersion exposure, only the protective film can be peeled off prior to alkali development. . In other words, since the protective film can be peeled off after the post-exposure heat treatment and development, it is possible to effectively prevent watermark defects and non-turn defects caused by the immersion liquid that has penetrated the protective film. Become. In addition, as long as this fat-soluble coffin has solubility in an organic solvent, it may be an alkali-soluble coffin.

[0057] As the fat-soluble rosin, for example, a resin comprising a polymer containing at least one repeating unit selected from the group consisting of the following general formula (1) and the following general formula (2) as a constituent component is preferable. That's right. Since these resins have a trifluoromethyl group or an alicyclic hydrocarbon group having 4 to 20 carbon atoms in the structure, a protective film resistant to pure water, which is widely used as an immersion liquid, is used. In addition to being able to be formed, since it has high fat solubility, it can be easily peeled off by organic solvents such as higher alcohols, polyhydric alcohols, alkyl acetates and alkyl ethers.

[Chemical 5]

[In the general formula (1) or (2), R ¹ is hydrogen, methyl group or trifluoromethyl group, R ² is a divalent organic group, R ³ is alicyclic carbonization having 4 to 20 carbon atoms. Indicates a hydrogen group or its derivative The ]

In the general formula (1), examples of the “divalent organic group” represented by R ² include a divalent hydrocarbon group; a carbon atom, a hydrogen atom such as an alkylene glycol group and an alkylene ester group And divalent organic groups containing other atoms. Among these, a linear or branched saturated hydrocarbon group, a monocyclic hydrocarbon ring group, or a bridged cyclic hydrocarbon ring in which a linear, branched, or cyclic divalent hydrocarbon group is preferred. Groups and the like are more preferred.

[0059] Examples of the "linear or branched saturated hydrocarbon group" include a methylene group, an ethylene group, a 1,2 propylene group, a 1,3 propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, Heptamethylene group, otatamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, tridecamethylene group, tetradecamethylene group, pentadecamethylene group, hexadecamethylene group, heptadecamethylene group, octadecamethylene group Linear alkylene group such as methylene group or nonadecamethylene group; 1-methyl-1,3 propylene group, 2-methyl-1,3 propylene group, 2-methyl-1,2 propylene group, 1 methyl 1,4-butylene group or Branched alkylene group such as 2-methyl-1,4-butylene group; ethylidene group, propylidene group or 2-propylidene group Alkylidene groups such as, and the like.

[0060] The "monocyclic hydrocarbon ring group" includes a cycloalkylene group having a carbon number of 3 to: LO, specifically, 1,3 cyclobutylene group, 1,3 cyclopentylene group, 1,4-cyclo A hexylene group, a 1,5-cyclooctylene group, and the like are preferable. “Bridged cyclic hydrocarbon ring group” includes a hydrocarbon ring group having 4 to 30 carbon atoms and 2 to 4 rings, specifically 1, 4 norbornene group, 2, 5 norborn group. A norbornylene group such as a -len group; an adamantylene group such as a 1,5-adamantylene group or a 2,6-adamantylene group is preferred.

[0061] The "divalent organic group" may be a combination of these functional groups. For example, when the “divalent organic group” has a monocyclic hydrocarbon ring group or a bridged cyclic hydrocarbon ring group in its structure, the bistrivalent repeating unit (1) is present at the end of the group. As a spacer between the fluoromethyl monohydroxymethyl group, a structure in which a linear alkylene group having 1 to 4 carbon atoms is bonded is preferable.

[0062] Among the "divalent substituents" described above, a divalent carbon containing a 2,5-norborene group A hydride group, a 1,2-ethylene group or a propylene group is preferred.

[0063] Te you, the general formula (2), examples of the alicyclic hydrocarbon group having 4 to 20 carbon atoms R ^3, for example, Roh Ruborunan, tricyclodecane, tetracyclododecane, or Adamantan, cyclobutane, shea Alicyclic hydrocarbon groups derived from cycloalkanes such as clopentane, cyclohexane, cycloheptane, cyclooctane; the hydrogen atoms of these alicyclic hydrocarbon groups are, for example, methyl, ethyl, n-propyl Group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group, etc. Examples include groups substituted above. Among these alicyclic hydrocarbon groups, alicyclic hydrocarbon groups derived from norbornane, tricyclodecane, tetracyclododecane, adamantane, cyclopentane or cyclohexane, and hydrogen atoms of these alicyclic hydrocarbon groups A group in which is substituted with the alkyl group is preferred.

[0064] The fat-soluble resin for forming the protective film may not contain any repeating unit (1) or repeating unit (2), may contain only one type, or two types. May contain more. Further, a repeating unit other than the repeating unit (1) or the repeating unit (2) may be included. However, the total content of the repeating unit (1) and the repeating unit (2) is preferably 50 to: LOO mol%, based on all repeating units. 60 to: LOO mol%. Is more preferred 70-: LOO mol% is particularly preferred. If the total content of the repeating unit (1) and the repeating unit (2) is 50 mol% or less, the properties as a protective film may not be fully exhibited!

[0065] There is no particular limitation on the range of the molecular weight of the fat-soluble rosin for forming the protective film, and various molecular weight ranges can be used as necessary. The polystyrene-reduced mass average molecular weight measured by gel permeation chromatography (GPC) (“Mw” is force ^s ) is usually 2,000 to 200,000, and 2,500 to 100,000. The power to do S is better, and the power to make 3,000-50,000 is even better! By setting it as such a range, there exists an advantage that the protective film which is excellent in the solubility with respect to an organic solvent, and has high water resistance and mechanical characteristics can be formed. On the other hand, if the Mw of the fat-soluble resin for forming the protective film is less than 2,000, a protective film with high water resistance and mechanical properties is formed. There is a risk that it will not be possible. If Mw exceeds 200,000, the solubility in organic solvents may be reduced.

[0066] It should be noted that the fat-soluble resin for forming the protective film is more preferable as there are less impurities such as halogen and metal, thereby providing a coating property as a protective film and a uniform solubility in an organic solvent. Further improvements can be made. Examples of the purification method of sorghum include chemical purification methods such as washing with water and liquid-liquid extraction, and purification methods combining these chemical purification methods with physical purification methods such as ultrafiltration and centrifugation, etc. Can be mentioned. One type of fat-soluble resin for forming a protective film may be used alone, or two or more types may be used in combination.

[0067] The fat-soluble resin for forming the 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 then adding the solution to a filter having a pore size of about 30 nm. The coating liquid is prepared by filtering with a coating method, and this coating liquid is formed on the photoresist film by using a conventionally known coating method such as spin coating, casting coating or roll coating. Can do. This protective film may be baked to volatilize the solvent.

[0068] The organic solvent used in preparing the above coating solution may be appropriately selected in consideration of the solubility of the fat-soluble resin, but it is preferable to use a monohydric alcohol that is preferably an alcohol. More preferably, it is particularly preferable to use monohydric alcohols having 1 to LO carbon atoms. These organic solvents are excellent in that they are highly soluble in fat-soluble coagulants and cause intermixing with the photoresist film to be coated 1, which is unlikely to adversely affect lithography performance. Masashi.

[0069] Examples of "monohydric alcohols having 1 to 10 carbon atoms" include, for example, 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, 4-methyl-1 pentanol, 4-methyl-2 pentanol, etc. 6 monohydric alcohols; 2, 2 dimethyl-3 pentanol, 2, 3 dimethyl-3 pe Tano one 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 7-carbon monohydric alcohols such as 2-methyl-1-hexanol, 5-methyl-2-hexanol, etc .; 2-ethyl-1-hexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, Monohydric alcohols with 8 carbon atoms such as 1-octanol, 2-octanol, 3-octanol, 2-propyl 1-pentanol, 2, 4, 4 trimethyl-1-pentanol; 2, 6 dimethyl-4 monoheptanol, 3 ethyl Monovalent alcohols with 9 carbon atoms such as 2,2 dimethyl-1 pentanoyl, 1-nonanol, 2 nonanol, 3, 5, 5 trimethyl 1-hexanol S; 1 Dekanoru, 2-decanol, 4 Dekanoru, 3,7-dimethyl-1 Okutanoru include a 3, 7 monohydric alcohol having 10 carbon atoms, such as dimethyl 3- Okutanoru. Among these alcohols, 4-methyl-2 pentanol, butanol, hexanol or a mixed solvent thereof is preferably used because it is difficult to remain in the photoresist film which is difficult to solidify at low temperatures! / ,.

[0070] The organic solvent for preparing the coating liquid may be mixed with another solvent for the purpose of adjusting the coating property (coating property) to the photoresist film. The “other solvent” makes it possible to uniformly coat the protective film, so that the resin for forming the protective film can be sufficiently dissolved, and it is difficult to dissolve the photoresist film. Choose from the appropriate ones.

[0071] Examples of "other solvents" include polyhydric alcohols such as ethylene glycol and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol monomethylenoatenore, ethyleneglycolenomonoethylenotenole, ethylene Glycolic Resin Minoetol, Ethylene Glycolic Resinetinoreetenore, Diethylene Glycolinole Monomethinore Iter, Diethylene Glycol Monoethyl Ether, Diethylene Glycol Dimethyl Diethylenole, Diethylene Glycolic Linoetino Leetenore, Diethylene Glyco Norenoetino Alkyl ethers of polyhydric alcohols such as remetinole etherol, propyleneglycololemonomethinoleethenole, propyleneglycolenomonoethylenole ether; Glycol E chill E one ether acetate, diethylene E chill ether acetate, propylene glycol Honoré ethyl Honoré ether Honoré acetate, propylene glycol Honoré mono-methylol Honoré ether Honoré acetate Alkyl ether acetates of polyhydric alcohols such as: Aromatic hydrocarbons such as toluene and xylene; Acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4 hydroxy mono 4-methyl 2 pentanone, diacetone alcohol Ketones such as: ethyl acetate, butyl acetate, 2-hydroxypropionate, 2-hydroxy-2-methylpropionate, 2-hydroxy-2-methylpropionate, ethoxyethyl acetate, hydroxyethyl acetate, 2-hydroxy- Examples include esters such as methyl 3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate and methyl 3-ethoxypropionate; water and the like. Among these, cyclic ethers, polyhydric alcohol alkyl ethers, polyhydric alcohol alkyl ether acetates, ketones, esters, and water are preferably used.

[0072] As the organic solvent, one kind may be used alone, or two or more kinds may be used in combination, as long as the uniformity of the solvent can be maintained. In order to exert the effect of being hard to solidify at low temperatures and remaining in the photoresist film, the content of monohydric alcohol having 10 or less carbon atoms in the organic solvent is 10 to: L00 is preferably 20% by mass, more preferably 20 to: L00% by mass.

[0073] A surfactant may be added to the coating solution for the purpose of improving coating properties, antifoaming properties, leveling properties, and the like. The following surfactants are all trade names: BM-1000, BM-1100 (above, manufactured by BM Chemi Co., Ltd.), MegaFuck F142D, F172, F173, F183 (above, Dainippon Ink and Chemicals, Inc.) ), FLORAD FC-135, FC-170C, FC-430, FC-431 (above, Sumitomo 3EM), Surflon S-112, S-113, S-131, S- Fluorine-based interfaces such as 141, S-145 (Asahi Glass Co., Ltd.), SH-28PA, D-190, D-193, SZ-6032, SF-8428 (above, manufactured by Toray Dawoku Silicone Co., Ltd.) Activators 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.

[0074] The thickness of the protective film is preferably as close as possible to an odd multiple of Z4m (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. [0075] [3] Immersion exposure:

The method of the present invention is an immersion exposure step in which a photoresist film is exposed by irradiating the photoresist film with radiation having a refractive index higher than air (immersion liquid) interposed therebetween. Is provided.

[0076] 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), radiation is irradiated through a mask having a predetermined pattern, and photo The resist film is exposed.

[0077] The radiation that can be used in the immersion exposure may be appropriately selected depending on the type of the photoresist film and the protective film to be used. For example, visible light; ultraviolet rays such as g-line and i-line Various types of radiation such as deep ultraviolet rays such as excimer lasers, X-rays such as synchrotron radiation, and charged particle beams such as electron beams can be used. Among these, an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm) is preferably used. The exposure conditions such as the radiation dose may be appropriately set according to the composition of the radiation-sensitive resin composition, the type of additive, and the like.

[0078] [4] Protective film peeling:

After the exposure of the photoresist film, the protective film is peeled off from the surface force of the photoresist film. The method of the present invention is characterized in that the protective film is peeled off prior to post-exposure heat treatment or development. Although it is conceivable that the protective film is peeled off during alkaline development of the photoresist film, the protective film is peeled off prior to the heat treatment or development after the exposure, so that the watermark caused by the immersion liquid that has penetrated the protective film. Defects and pattern defects can be effectively prevented.

[0079] The peeling method is not particularly limited, but a method that does not impair the resist pattern system performance of the photoresist film is preferable. For example, as described above, a method of forming a protective film with a fat-soluble resin and peeling off the protective film using an organic solvent is preferable.

[0080] Although the organic solvent used for peeling off the protective film varies depending on the composition of the protective film, monohydric alcohols having 10 or less carbon atoms are particularly preferred among monohydric alcohols. Such organic Solvents are preferred because they have excellent protective film solubility and are unlikely to degrade the performance of lithography due to intermixing with photoresist films.

[0081] Among monohydric alcohols, 4-methyl-2-pentanol, butanol, hexanol, or alcohols thereof are used because they are difficult to remain in the photoresist film even when used for removing a protective film that is difficult to solidify at low temperatures. The mixed solvent is preferable. Incidentally, monohydric alcohols may be used as a mixture with other organic solvents, but the total mass of the mixed solvent, monohydric alcohol can. 10 to:! LOO mass ^_0/0 is contained in, Rukoto It is preferable that 20 to 100% by mass is contained! / ,.

[0082] The organic solvent used for removing the protective film 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 that exceeds the dissociation constant (pKa) force may cause problems such as the cross-sectional shape of the resist pattern after development being capped.

[0083] As a compound having a dissociation constant (pKa) of 5 or less, an organic acid is preferred in a molecule having a sulfo group.

Sulfonic acids having (mono SO OH) or carboxylic acids having a carboxyl group

2

Particularly preferred are sulfonic acids. Sulfonic acids can be suitably used because of their low dissociation constant (pKa) and high acidity.

[0084] 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, heptanesulfonic 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 Dimethylbenzenesulfonic acid, 2—mesitylene sulfonic acid, 2,4 di-orthobenzene senorephonic acid, 4—black benzene senorephonic acid, 4-bromobenzene sulphonic acid, 4 fluorobenzene sulphonic acid, 2, 3, 4, 5 , 6 Pentafluorobenzene sulfonic acid, 4-hydroxybenzene sulfonic acid, 4 sulfobenzoic acid, 4-sulfo-phosphorus And aryl sulfonic acids such as benzyl sulfonic acid and phenethyl sulfonic acid; cyclic sulfonic acids such as camphor sulfonic acid; and the like. The organic solvent used for peeling off the protective film may contain one acid alone, or may contain two or more acids.

[0085] [5] Post-exposure heat treatment:

In the method of the present invention, after the surface strength protective film of the photoresist film is peeled off, a post-exposure heat treatment (Post Exposure Bake, hereinafter may be referred to as “PEB”) is performed. Performing PEB is preferable because the resolution, pattern shape, developability, and the like of the resist can be improved. The heating condition of PEB is preferably a force of 30 to 200 ° C, more preferably 50 to 150 ° C, which varies depending on the composition of the radiation-sensitive resin composition and the type of additive. .

[0086] [6] Development:

In the method of the present invention, after a post-exposure heat treatment, development is performed to obtain a resist pattern formed body. 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, it is developed with an alkali developer. Thus, a resist pattern formed body is obtained.

The [0087] alkali developing solution, for example, sodium hydroxide, potassium Mizusani匕, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, Echiruamin, n- Puropiruamin, Jechiruamin, di _n - Puropiruamin, Toriechiruamin, Methyljetylamine, dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, pyrrole, piperidine, choline, 1,8-diazabicyclo [5.4.0] — It is preferable to use an alkaline aqueous solution in which at least one alkaline compound such as 7-undecene, 1,5-diazabicyclo [4.3.0] —5-nonane is dissolved. Of these, an aqueous solution of tetraalkylammonium hydroxides can be suitably used.

[0088] The concentration of the alkaline aqueous solution is preferably 10% by mass or less, 1 to: L0% by mass, and more preferably 2 to 5% by mass. If the concentration of the alkaline aqueous solution is 10% by mass or less, the non-exposed area will be dissolved in the alkaline developer. Since it can suppress, it is preferable.

[0089] An appropriate amount of a surfactant may be added to the alkaline developer. By adding a surfactant, there is an 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 with water and dried to obtain a resist pattern formed body.

Example

Hereinafter, the method for producing a resist pattern forming 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.

[0092] [Synthesis Example 1] _:

First, an acid-dissociable group-modified alkali-soluble resin for forming a photoresist film was synthesized by the following method.

[0093] in advance, the following compound (M- 1) 53. 93g (50 mole%), Compound (M- 2) 35. 38g (40 molar ^_0/0), Compound (M- 3) 10. 69g (10 mole ^_0/0) was dissolved in 2-butanone 200 g, prepared further dimethyl chill 2, 2'Azobisu (2-methylpropionate) (initiator) 5. single-mer solution添Ka卩a 58g did. On the other hand, 2-butanone lOOg was put into a 500 ml three-necked flask and purged with nitrogen for 30 minutes. After purging with nitrogen, the inside of the three-necked flask was heated to 80 ° C. with stirring, and the monomer solution prepared in advance was added dropwise over 3 hours using a dropping funnel. The dripping start was set as the polymerization start time, and the polymerization reaction was carried out for 6 hours.

[Chemical 6]

(M-1) (M-2) (M-3)

[0094] After the completion of the polymerization reaction, the polymerization solution was cooled to 30 ° C or lower by water cooling, and the cooled polymerization solution was poured into 2000 g of methanol, and the precipitated white powder was separated by filtration. The operation of adding 400 g of methanol to the filtered white powder and washing it in a slurry state was repeated twice, and then the white powder was filtered again and dried at 50 ° C for 17 hours. A powdered polymer was obtained (74 g, 74% yield). This polymer has an Mw of 6900, Mw / Mn = 70, and ¹³ C-NMR analysis. As a result, each repetition derived from the compound (M-1), the compound (M-2), and the compound (M-3) was repeated. content of units 53.0: 37.2: 9 was a copolymer of 8 (mol ^_0/0). This polymer is referred to as an acrylic polymer (A-1). The content of the low molecular weight component derived from each monomer in the polymer was 0.03% by mass with respect to 100% by mass of the polymer.

[0095] [Synthesis Example 2]:

Next, a fat-soluble rosin for forming a protective film was synthesized by the following method.

[0096] In advance, methacrylic acid (1, 1, 1, 1-trifluoromethyl 2-trifluoromethyl-1-hydroxy-4-pentyl) ester 93. 91 ₈ (85 mol%) was dissolved in isopropanol 50 _8. and a monomer solution (1) was prepared Bulle acid 6. 09g (15 mole ^_0/0) a monomer solution prepared by dissolving iso isopropanol 50 g (2). On the other hand, in a 500 ml three-necked flask equipped with a thermometer and dropping funnel was charged 6.91 g of 2, 2, azobis (methyl 2-methylpropionate) (polymerization initiator) and 200 g of isopropanol and purged with nitrogen for 30 minutes. did. After purging with nitrogen, heat the flask to 80 ° C while stirring with a magnetic stirrer, and use a dropping funnel to prepare the monomer solution (1) prepared in advance for 20 minutes. It was dripped. After completion of the dropwise addition, the reaction is continued for another 20 minutes, and the monomer solution (2) prepared in advance is taken over 20 minutes. Then, the reaction was continued for another hour, and the mixture was cooled to 30 ° C or lower to obtain a copolymer liquid.

[0097] 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 to carry out a liquid separation washing for separation, and the solvent was replaced with 4-methyl-2-pentanol again. The solid concentration of the sample after solvent replacement was calculated by calculating the mass force of the residue after 0.3 g of the resin solution was placed on an aluminum pan and heated on a hot plate heated to 140 ° C for 2 hours. This was used for the preparation of the coating liquid for forming the protective film and the yield calculation. Mw, MwZMn (dispersion degree of molecular weight) and yield (mass%) of the obtained copolymer were 5830, 1.7 and 72%, respectively.

[0098] [Preparation of radiation-sensitive rosin 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 triphenylsulfo-munonafluoro-n-butanesulfonate as a radiation-sensitive acid generator, 1 ( 4-N-butoxynaphthyl) tetrahydrothiophene trifluoromethane sulfonate, 6 parts by mass, N-t butoxycarbonylpyrrolidine as an acid diffusion inhibitor, 0.65 parts by mass, and γ-petit-mouth rataton as an auxiliary solvent Further, 20 parts by mass of propylene glycol monomethyl ether acetate as a main solvent was added, and each component was mixed to obtain a uniform solution. Thereafter, the mixture was filtered using a membrane filter having a pore size of 0.2 / z m to prepare a coating liquid composed of a radiation-sensitive resin composition (total solid content concentration: about 6% by mass).

[0099] [Preparation of protective film-forming coating solution]:

Add 4 methyl 2-pentanol to 100 parts by mass of the fat-soluble fat synthesized in Synthesis Example 2, adjust the total solids concentration to 3.5% by mass, and filter through a filter with a pore size of 0.2 m. By doing so, the coating liquid for protective film formation was prepared.

[0100] [Preparation of protective film remover]:

The camphorsulfonic acid 0.075 mass ^_0/0 papermaking 4-methyl 2-pentanol containing tone, to prepare a protective film stripping solution by filtration through a filter having a pore size of 0. 2 m. [0101] [Evaluation method]:

The following evaluation was performed using the radiation-sensitive resin composition prepared as described above, the coating liquid for forming a protective film, and the protective film peeling liquid.

[0102] (1) Forced watermark test:

Using a coater Z developer (1) (trade name: CLEAN TRACK ACT8, manufactured by Tokyo Electron Ltd.), an anti-reflection film forming agent (trade name: ARC29A, manufactured by Bull Soichi. Science) is applied to an 8-inch silicon wafer. A 77 nm-thick antireflection film was formed by spin coating and performing PB at 205 ° C. for 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, whereby a photoresist having a film thickness of 150 nm is obtained. A film was formed. Further, the protective film-forming coating solution 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.

[0103] Next, using a ArF projection exposure system (trade name: S30 6C, manufactured by Nikon Corp.), NA: 0.78, Sigma: 0.85, 2Z3Ann optics Exposure was performed under conditions to create a test wafer. Thereafter, using a pipette, four 0.3 uL water droplets were marked on the surface of the wafer and dried for 10 minutes.

[0104] In Example 1, the protective film was previously removed with the protective film remover, and PEB was performed at 115 ° C for 60 seconds on the hot plate of the coater Z Devellono (1). After paddle development for 60 seconds with the LD nozzle of the same coater Z developer (1), rinsed with ultrapure water, and then spun off at 4000 rpm for 15 seconds and spin-dried.

[0105] On the other hand, for 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 during alkali development of the photoresist film. By visually observing the resist pattern formed in this way, a drop mark (watermark) remains at the position where the water droplet is marked with a pipette. It was judged as “bad”. The results are shown in Table 1.

[0106] [Table 1] Forced war evening Sensitivity Pattern defect Pattern shape Mark test Defect

Example 1 Good 19m J / cm ² Good Good Comparative Example 1 Bad 19m J / cm ² Good Good

[0107] (2) Sensitivity:

Using a coater Z developer (2) (trade name: CLEAN TRACK ACT12, manufactured by Tokyo Electron Co., Ltd.), an anti-reflection film forming agent (trade name: ARC29A, manufactured by Bull Soichi 'Science) is spin-coated on a 12-inch silicon wafer. An antireflection film with a thickness of 77 nm was formed by performing PB under the conditions of 205 ° C and 60 seconds. This was used as a substrate.

[0108] Next, the surface of the antireflection film of the substrate was spin-coated with a coating liquid comprising the radiation-sensitive resin composition, and PB was performed at 115 ° C for 60 seconds. A 150 nm thick photoresist film was formed. Further, the protective film-forming coating solution 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. Next, using a ArF excimer laser single exposure device (trade name: TWIN SCAN XT1250i, manufactured by ASML, certification conditions; NAO. 85, Sigma 0.9.93 / 0. 69) It exposed through the mask pattern.

Thereafter, in Example 1, the protective film was previously stripped with the protective film stripping solution 115. PEB was conducted under conditions of C, 60 seconds, 2. tetramethylammonium of 38 mass ^_0/0 - by Umuhidorokishido solution, developed for 30 seconds at 23 ° C, washed with water and dried to form a positive-tone resist pattern did.

[0110] Regarding Comparative Example 1, PEB was performed under the same conditions as in Example 1 without removing the protective film, and then the protective film was peeled off during alkali development of the photoresist film. For the resist pattern formed in this way, the exposure amount that forms a line 'and' space pattern (1L1S) with a line width of 65 nm in a one-to-one line width is the optimum exposure amount, and this optimum exposure amount is the sensitivity. . For this measurement, a scanning electron microscope (trade name: S-9380, manufactured by Hitachi High-Technologies Corporation) was used. The results are shown in Table 1.

[0111] (3) Pattern defect defect inspection:

Coater Z Developer (2) (Product name: CLEAN TRACK ACT12, Tokyo Electron) Spin coating an anti-reflective film forming agent (trade name: ARC29A, manufactured by Bull Soichi's Science Co., Ltd.) on a 12-inch silicon wafer, and performing PB at 205 ° C for 60 seconds. Thus, an antireflection film having a thickness of 77 nm was formed. This was used as a substrate.

[0112] The surface of the substrate was patterned with a radiation-sensitive resin composition (trade name: ArF AR201 J, manufactured by JSR). The radiation sensitive resin composition in the previous period was spin coated on the surface of the substrate and PB was performed at 115 ° C. for 60 seconds to form a photoresist film having a thickness of 150 nm. The protective film-forming coating solution 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 32 nm.

[0113] Using the ArF excimer laser exposure apparatus (trade name: TWIN SCAN XT1250i ゝ ASML, certification conditions; NAO. 85, Sigma 0.93 / 0.69) Then, it was exposed through a mask pattern.

[0114] After that, in Example 1, the protective film was peeled off with the protective film remover, and PEB was performed on the hot plate of the coater Z de Verono (2) at 115 ° C for 60 seconds. The paddle development was performed for 30 seconds with the LD nozzle of Z de Verono (2), rinsed with ultrapure water, then shaken off at 3000 rpm for 15 seconds and spin-dried.

[0115] Regarding Comparative Example 1, PEB was performed under the same conditions as in Example 1 without removing the protective film, and then the protective film was peeled off during alkali development of the photoresist film.

[0116] The resist pattern thus formed was subjected to wafer defect inspection using a general name: defect inspection system (trade name: KL A2351, KLA—manufactured by Tencor), and the detected defects were detected. Observation with a scanning electron microscope (trade name: S-9360, manufactured by Hitachi Sokki Co., Ltd.) confirmed the presence of pattern defect defects (specifically, pattern thinning or thickening defects). Those in which this pattern defect was detected were defined as “defect”, and those that were not detected were defined as “good”. The results are shown in Table 1.

[0117] (4) Pattern shape:

The cross-sectional shape of the 65nm line and space pattern was observed with a scanning electron microscope (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation). As shown in Fig. 1, the line width in the middle of the resist pattern Lb and the line width La at the top of the film were measured, and the range of 0.665≤ (La-Lb) /Lb≤1.1 was evaluated as "good" and the others were evaluated as "bad". The results are shown in Table 1 [0118] [Evaluation Result]:

As is clear from the data in Table 1, the resist pattern of Example 1 that was subjected to post-exposure heat treatment and development after the protective film was peeled off also from the surface force of the photoresist film was either sensitive or patterned. Good results were also shown in the test. In addition, watermarks such as defective patterns were not recognized.

[0119] On the other hand, the resist pattern of Comparative Example 1 in which the protective film was peeled off from the surface of the photoresist film after the post-exposure heat treatment and before development showed good results in terms of sensitivity and pattern shape. However, defects such as watermarks and pattern defects occurred.

Industrial applicability

[0120] In the resist pattern forming method of the present invention, even if a large number of water droplets remain on the surface of the protective film during immersion exposure, they are removed when the protective film is removed before PEB. The occurrence of mark defects and pattern defect defects can be effectively suppressed. 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

Claims Provided with an immersion exposure process in which the photoresist film is exposed by irradiating the photoresist film with radiation having a refractive index higher than that of air and interposing a liquid (immersion liquid). A resist pattern forming method comprising: forming the photoresist film on a surface of a substrate; forming a protective film resistant to the immersion liquid on the surface of the photoresist film; and interposing the immersion liquid In this state, the photoresist film is exposed to radiation to expose the photoresist film, and after the protective film is peeled off from the surface force of the photoresist film, post-exposure heat treatment and development are performed. A resist pattern forming method for obtaining a resist pattern. 2. The resist pattern forming method according to claim 1, wherein the protective film is formed of a fat-soluble resin and the protective film is peeled off using an organic solvent. The fat-soluble resin forming the protective film is composed of a polymer containing at least one repeating unit selected from the group consisting of the following general formula (1) and the following general formula (2). The method for forming a resist pattern according to claim 2.

[Chemical 1]