JP2017207745A - Resist pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resist pattern forming method by which generation of a watermark defect and a residue defect can be suppressed.SOLUTION: The resist pattern forming method includes steps of: applying a photoresist composition directly or indirectly on a substrate surface; laminating a topcoat layer directly or indirectly on a surface of a photoresist film obtained in the above application step; subjecting the photoresist film to liquid immersion exposure in the presence of an immersion liquid on the surface of the topcoat layer; and developing the photoresist film. The method includes a step of partially removing the topcoat layer between the liquid immersion exposure step and the development step. The removal step is preferably performed by use of a stripping solution.SELECTED DRAWING: None

Description

  The present invention relates to a resist pattern forming method.

  Along with miniaturization of various electronic device structures such as semiconductor devices and liquid crystal devices, miniaturization of resist patterns in lithography processes is required. In response to such a demand, an immersion exposure method is used in which exposure is performed by filling a space between a lens and a photoresist film with an immersion medium such as pure water or a fluorine-based inert liquid. This immersion exposure method has the advantage that the numerical aperture (NA) of the lens can be increased and a high resolution can be obtained.

  In the pattern formation method by this immersion exposure method, elution of the photoresist film component into the immersion liquid and suppression of pattern defects due to the immersion liquid droplets remaining on the photoresist film surface are required. . As a technique for satisfying these requirements, a top coat layer is provided between a photoresist film and an immersion liquid (International Publication No. 2004/74937, Japanese Patent Application Laid-Open No. 2007-324385, and a special technique). (See Kaikai 2008-42019).

International Publication No. 2004/74937 JP 2007-324385 A Japanese Patent Laid-Open No. 2008-42019

  When such a topcoat layer is provided, the water repellency on the surface of the topcoat layer is increased in order to improve scanning performance. However, when the fluorine content in the topcoat layer is increased in order to increase the water repellency on the surface of the topcoat layer, there is a disadvantage that watermark defects and residue defects are generated in the formed resist pattern.

  The present invention has been made based on the above circumstances, and an object thereof is to provide a resist pattern forming method capable of suppressing the generation of watermark defects and residue defects.

  The invention made in order to solve the above problems includes a step of coating a photoresist composition directly or indirectly on a substrate surface (hereinafter also referred to as “coating step”) and a photo obtained by this coating step. A step of laminating the topcoat layer directly or indirectly on the resist film surface (hereinafter also referred to as “lamination step”), and immersion exposure of the photoresist film with an immersion liquid interposed on the topcoat layer surface And a step of developing the photoresist film (hereinafter also referred to as “development process”), and a step between the immersion exposure process and the development process. The resist pattern forming method includes a step of removing a part of the topcoat layer (hereinafter also referred to as “removing step”).

  According to the resist pattern forming method of the present invention, a resist pattern with few watermark defects and residue defects can be formed. Therefore, the resist pattern forming method can be suitably used for a semiconductor device processing process and the like that are expected to be further miniaturized in the future.

<Resist pattern formation method>
The resist pattern forming method includes a coating process, a laminating process, an immersion exposure process, and a development process, and includes a removal process between the immersion exposure process and the development process.

  According to the resist pattern forming method, a resist pattern with few watermark defects and residue defects can be formed. The reason why the resist pattern forming method has the above-described configuration provides the above-mentioned effect is not necessarily clear, but can be inferred as follows, for example. That is, the resist pattern forming method can suppress generation of watermark defects in the immersion exposure process by including a step of laminating a topcoat layer on the surface of the photoresist film. In addition, after the immersion exposure step and before the development step, a step of removing a part of the topcoat layer is provided, and a polymer that does not dissolve in the developer is previously removed from the polymers constituting the topcoat layer. Therefore, it is considered that the generation of residue defects can be suppressed. In addition, the polymer of the top coat layer that has not been removed in the removal process contributes to the suppression of the occurrence of residue defects, and the low dissolution in the photoresist film that can cause residue defects in the development process. This is considered to be due to improving the solubility of the functional polymer in the developer. Hereinafter, each step will be described.

[Coating process]
In this step, a photoresist composition is applied directly or indirectly to the substrate surface. Thereby, a photoresist film is formed on the substrate surface directly or via another layer. As a substrate to be used, a silicon wafer, a silicon wafer coated with aluminum, and the like are usually mentioned. In addition, in order to maximize the characteristics of the photoresist film to be formed, an organic or inorganic antireflection described in, for example, Japanese Patent Publication No. 6-12452, etc. on the substrate surface as the other layer in advance. It is preferable to form a film.

(Photoresist composition)
The type of the photoresist composition is not particularly limited, and it is appropriately selected from the photoresist compositions conventionally used for forming a photoresist film according to the intended use of the resist. be able to. Among them, a polymer containing an acid dissociable group (hereinafter also referred to as “acid dissociable group (a)”) and a radiation sensitive acid generator (hereinafter referred to as “polymer (P)”). A photoresist composition containing an acid generator (Q) ”is preferred.

  In the polymer (P), examples of the structural unit containing the acid dissociable group (a) (hereinafter, also referred to as “structural unit (p)”) include a structural unit represented by the following formula (A). It is done.

In the above formula (A), R ^P represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^p1 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ^p2 and R ^p3 each independently represent a monovalent hydrocarbon group having 1 to 20 carbon atoms, or have 3 to 20 ring members composed of carbon atoms to which these groups are combined and bonded to each other. Represents an alicyclic structure.

The R ^P, from the viewpoint of copolymerizability of the monomer giving the structural units (p), preferably a hydrogen atom or a methyl group, more preferably a methyl group.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ^p1 , R ^p2, and R ^p3 include, for example, a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, and 1 to 3 carbon atoms. Valent alicyclic hydrocarbon group, monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and the like.

  Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-butyl group, and an n-butyl group.

  Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic hydrocarbon groups such as cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclohexenyl group; norbornyl group, adamantyl group, norbornenyl And polycyclic alicyclic hydrocarbon groups such as groups.

  Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl group, tolyl group, xylyl group and naphthyl group; aralkyl groups such as benzyl group, phenethyl group and naphthylmethyl group. It is done.

Examples of the alicyclic structure having 3 to 20 ring members constituted by the carbon atoms to which the groups of R ^p2 and R ^p3 are combined and bonded to each other include monocyclic alicyclic rings such as a cyclopentane structure, a cyclohexane structure, and a cyclohexene structure. Structure: Polycyclic alicyclic structures such as norbornane structure, adamantane structure, norbornene structure and the like can be mentioned.

  As the structural unit (p), for example, a (meth) acrylate having a 1-alkyl-1-monocyclic alicyclic hydrocarbon group such as 1-ethyl-1-cyclopentyl (meth) acrylate; 2-i-propyl- Examples include structural units derived from (meth) acrylates having a 2-alkyl-2-polycyclic alicyclic hydrocarbon group such as 2-adamantyl (meth) acrylate.

  In addition to the structural unit (p), the polymer (P) further has a structural unit containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof (hereinafter also referred to as “structural unit (q)”). Is preferred.

As the structural unit (q), for example,
As lactone structure, norbornane lactone structure, butyrolactone structure, etc .;
As cyclic carbonate structure, ethylene carbonate structure, propylene carbonate structure, etc .;
Examples of the sultone structure include structural units derived from (meth) acrylic acid esters including a norbornane sultone structure and a propane sultone structure.

  Moreover, the polymer (P) may have other structural units other than the structural unit (p) and the structural unit (q). Examples of other structural units include a structural unit containing a hydrocarbon group having 4 to 20 carbon atoms (hereinafter also referred to as “structural unit (r)”), a structural unit containing a polar group such as a hydroxy group, and the like. It is done. Examples of the structural unit (r) include a structural unit derived from tricyclodecanyl (meth) acrylate.

  As a minimum of the content rate of a structural unit (p), 25 mol% is preferable with respect to all the structural units which comprise a polymer (P), and 35 mol% is more preferable. As an upper limit of the said content rate, 60 mol% is preferable and 50 mol% is more preferable. By making the content rate of a structural unit (p) into the said range, the resolution of a photoresist composition can be improved.

  As a minimum of the content rate of a structural unit (q), 20 mol% is preferable with respect to all the structural units which comprise a polymer (P), and 30 mol% is more preferable. As an upper limit of the said content rate, 70 mol% is preferable and 60 mol% is more preferable. By setting the content ratio of the structural unit (q) in the above range, the solubility of the photoresist film formed from the photoresist composition in the developer can be appropriately adjusted, and the photoresist film and the substrate It is possible to improve the adhesion.

  As an upper limit of the content rate of another structural unit, 20 mol% is preferable with respect to all the structural units which comprise a polymer (P), and 15 mol% is more preferable.

  The acid generator (Q) is a substance that generates an acid (hereinafter also referred to as “acid (b)”) upon irradiation (exposure). Due to the action of the generated acid (b), the acid-dissociable group (a) protecting the acidic group such as the carboxy group of the polymer (P) is dissociated in the exposed part to generate an acidic group. As a result, the solubility of the polymer (P) in the developer changes in the exposed portion, and a resist pattern is formed.

  The form of the acid generator (Q) contained in the photoresist composition is a form of a compound as described later (hereinafter also referred to as “acid generator (Q)”), which is incorporated as part of the polymer. However, both forms may be used.

  Examples of the acid (b) generated by exposure include sulfonic acid, carboxylic acid, disulfonylimide acid and the like.

Examples of the sulfonic acid generated by exposure include (1) a compound in which one or more fluorine atoms or fluorinated hydrocarbon groups are bonded to the carbon atom adjacent to the sulfo group,
(2) Examples include compounds in which a fluorine atom or a fluorinated hydrocarbon group is not bonded to a carbon atom adjacent to a sulfo group.

Examples of the carboxylic acid generated by exposure include (3) a compound in which one or more fluorine atoms or fluorinated hydrocarbon groups are bonded to the carbon atom adjacent to the carboxy group,
(4) The compound etc. with which the fluorine atom or the fluorinated hydrocarbon group has not couple | bonded with the carbon atom adjacent to a carboxy group are mentioned.

Examples of the disulfonylimide acid generated by exposure include (5) a compound in which one or more fluorine atoms or fluorinated hydrocarbon groups are bonded to the carbon atom adjacent to the sulfonyl group,
(6) Examples include compounds in which a fluorine atom or a fluorinated hydrocarbon group is not bonded to a carbon atom adjacent to the sulfonyl group.

  As said acid (b), the compound of said (1) or (5) is preferable, and the compound of said (1) is more preferable. Moreover, as acid (b), what has a cyclic structure is especially preferable.

  Examples of the acid generator (Q) include an onium salt compound, an N-sulfonyloxyimide compound, a halogen-containing compound, and a diazoketone compound that generate the acid (b) upon exposure. Examples of the onium salt compounds include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts, and the like. Of these, sulfonium salts and tetrahydrothiophenium salts are preferred.

  Examples of the sulfonium salt include triphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, and triphenylsulfonium 2- (bicyclo [2.2.1] heptane-2. '-Yl) -1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 2- (bicyclo [2.2.1] heptane-2'-yl) -1,1-difluoroethanesulfonate, and the like. .

  Examples of the tetrahydrothiophenium salt include 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (4-n-butoxynaphthyl) tetrahydrothiophene. Examples include nitro 2- (bicyclo [2.2.1] heptane-2′-yl) -1,1,2,2-tetrafluoroethane sulfonate.

  In addition to the polymer (P) and the acid generator (Q), the photoresist composition contains other components such as an acid diffusion controller (R), a water repellent resin (F), and a surfactant. Also good. Examples of the acid diffusion controller (R) include amine compounds such as trioctylamine and triethanolamine; R-(+)-(t-butoxycarbonyl) -2-piperidinemethanol, Nt-butoxycarbonyl-4 Examples include Nt-alkoxycarbonyl-containing amide compounds such as hydroxypiperidine; compounds (G) that generate an acid that does not substantially dissociate the acid dissociable group (a) by exposure. Examples of the compound (G) include triphenylsulfonium salicylate. Examples of the water-repellent resin (F) include a fluorine-based resin, and specifically, a resin having a fluorinated hydrocarbon group, a chain perfluoroalkyl polyether, a cyclic perfluoroalkyl polyether, a polychlorotriol. Examples include fluoroethylene, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

  The photoresist composition is prepared, for example, by dissolving a polymer (P), an acid generator (Q), and, if necessary, an acid diffusion controller (R) in a solvent. The photoresist composition is usually filtered through a filter having a pore diameter of about 30 nm. The lower limit of the solid content concentration of the photoresist composition is preferably 0.2% by mass and more preferably 1% by mass from the viewpoint of easy coating. As an upper limit of the said solid content concentration, 20 mass% is preferable and 10 mass% is more preferable.

  Examples of the coating method of the photoresist composition include conventionally known coating methods such as spin coating, cast coating, and roll coating. After applying the photoresist composition on the substrate, pre-baking (PB) may be performed to volatilize the solvent. As a minimum of the temperature of the above-mentioned PB, 50 ° C is preferred and 70 ° C is more preferred. As an upper limit of the said temperature, 150 degreeC is preferable and 120 degreeC is more preferable. The lower limit of the PB time is preferably 10 seconds, and more preferably 30 seconds. The upper limit of the time is preferably 600 seconds, and more preferably 300 seconds.

[Lamination process]
In this step, the topcoat layer is laminated directly or indirectly, i.e., through another layer, on the surface of the photoresist film obtained by the coating step. The lamination of the top coat layer is usually performed by coating the top coat composition directly or indirectly, preferably directly on the surface of the photoresist film.

(Topcoat composition)
The topcoat composition usually contains a polymer (hereinafter also referred to as “[A] polymer”) and a solvent (hereinafter also referred to as “[B] solvent”). The topcoat composition may contain other components such as a surfactant in addition to the [A] polymer and the [B] solvent.

  [A] Any polymer can be used as long as it can form a topcoat layer and can be subjected to immersion exposure. Moreover, it is preferable that a [A] polymer contains 2 or more types of polymers from which a characteristic differs. Examples of the characteristics of the polymer include a dissolution rate in a stripping solution, an etching rate in dry etching, and a receding contact angle in a film formation state.

  [A] Examples of the polymer include water-repellent resins and acidic resins. “Water-repellent resin” refers to a resin having a receding contact angle with water of 80 ° or more in a film formation state. “Acid resin” refers to a resin having an acidic functional group with a pKa of 10 or less. [A] The polymer may contain a resin other than the water-repellent resin and the acidic resin.

  Examples of the water-repellent resin include a fluorine-based resin. Specifically, a resin having a fluorinated hydrocarbon group, a chain perfluoroalkyl polyether, a cyclic perfluoroalkyl polyether, a polychlorotrifluoroethylene, Examples thereof include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and the like.

  The lower limit of the mass content of fluorine atoms in the fluororesin is preferably 0.1% by mass, more preferably 1% by mass, and even more preferably 5% by mass. As an upper limit of the said mass content rate, 30 mass% is preferable and 25 mass% is more preferable.

  Examples of the acidic resin include a resin having an oxo acid group and a resin having a phenolic hydroxyl group. Examples of the oxo acid group include a sulfo group and a carboxy group.

  When the topcoat composition contains two or more polymers having different properties as the [A] polymer, it is preferable that the two or more polymers have a water-repellent resin and an acidic resin.

  [B] Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and the like.

Examples of alcohol solvents include methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, n-pentanol, iso-pentanol, 2-methylbutanol, sec-pentanol, tert-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, 4-methyl-2-pentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, 3-heptanol , N-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, 2,6-dimethyl-4-heptanol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec- Monoalcohol solvents such as tetradecyl alcohol, sec-heptadecyl alcohol, furfuryl alcohol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol, diacetone alcohol;
Ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2 -Polyhydric alcohol solvents such as ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, polyhydric alcohol partial ether solvents such as dipropylene glycol monopropyl ether.

Examples of ether solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether, and diisoamyl ether;
Aromatic ring-containing ether solvents such as anisole and diphenyl ether;
Examples thereof include cyclic ether solvents such as tetrahydrofuran and dioxane.

Examples of the ketone solvent include acetone, 2-butanone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-iso-butyl ketone, methyl-n-amyl ketone, ethyl-n-butyl ketone, methyl-n. -Chain ketone solvents such as hexyl ketone, di-iso-butyl ketone, trimethylnonanone, 2,4-pentanedione, acetonyl acetone, acetophenone;
Examples thereof include cyclic ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone.

Examples of amide solvents include chain amides such as N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, and N-methylpropionamide. System solvents;
And cyclic amide solvents such as N, N′-dimethylimidazolidinone and N-methylpyrrolidone.

Examples of ester solvents include methyl acetate, ethyl acetate, γ-butyrolactone, γ-valerolactone, n-propyl acetate, iso-propyl acetate, n-butyl acetate, iso-butyl acetate, sec-butyl acetate, and n-acetate. Pentyl, sec-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, n-nonyl acetate, methyl acetoacetate, ethyl acetoacetate, Monocarboxylic acid ester solvents such as ethyl propionate, n-butyl propionate, iso-amyl propionate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate;
Ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl acetate Polyhydric alcohol partial ether carboxylate solvents such as ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monoethyl ether;
Carbonate solvents such as dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate;
lactone solvents such as γ-butyrolactone and δ-valerolactone;
Dicarboxylic acid ester solvents such as diethyl oxalate, di-n-butyl oxalate, diethyl malonate, dimethyl phthalate and diethyl phthalate;
Examples thereof include glycol diacetate and methoxytriglycol acetate.

Examples of the hydrocarbon solvent include n-pentane, iso-pentane, n-hexane, iso-hexane, n-heptane, iso-heptane, 2,2,4-trimethylpentane, n-octane, iso-octane, and cyclohexane. , Aliphatic hydrocarbon solvents such as methylcyclohexane;
Fragrances such as benzene, toluene, xylene, mesitylene, ethylbenzene, trimethylbenzene, methylethylbenzene, n-propylbenzene, iso-propylbenzene, diethylbenzene, iso-butylbenzene, triethylbenzene, di-iso-propylbenzene and n-amylnaphthalene Group hydrocarbon solvents and the like.

  [B] As the solvent, ether solvents, alcohol solvents and fluorine solvents are preferable, dialkyl ether solvents, monoalcohol solvents and fluorine-containing amines are more preferable, diisoamyl ether, 4-methyl-2-pentanol. And perfluorotributylamine is more preferred.

  The top coat composition is prepared, for example, by dissolving the [A] polymer and other components as necessary in the [B] solvent. The top coat composition is usually filtered through a filter having a pore size of about 30 nm. From the viewpoint of easy coating, the lower limit of the solid content concentration of the topcoat composition is preferably 0.2% by mass, and more preferably 1% by mass. As an upper limit of the said solid content concentration, 20 mass% is preferable and 10 mass% is more preferable.

  Examples of the method for applying the top coat composition include the same methods as the method for applying the photoresist composition in the application step. It is preferable to perform pre-baking (PB) after the top coat composition is applied. As a minimum of the temperature of the above-mentioned PB, 50 ° C is preferred and 70 ° C is more preferred. As an upper limit of the said temperature, 150 degreeC is preferable and 120 degreeC is more preferable. The lower limit of the PB time is preferably 10 seconds, and more preferably 30 seconds. The upper limit of the time is preferably 600 seconds, and more preferably 300 seconds.

(Topcoat layer)
By removing the [B] solvent from the coated top coat composition, a top coat layer composed of the [A] polymer or the like is formed.

  The lower limit of the average thickness of the formed topcoat layer is preferably 5 nm, more preferably 10 nm, and even more preferably 15 nm. The upper limit of the average thickness is preferably 100 nm, more preferably 70 nm, and even more preferably 50 nm.

  The average thickness of the top coat layer to be formed is preferably as close as possible to an odd multiple of λ / 4m (λ: wavelength of radiation, m: refractive index of the protective film). By doing in this way, the reflection suppression effect in the upper interface of a photoresist film can be enlarged.

  The topcoat layer preferably contains two or more polymers having different characteristics, and more preferably has a water-repellent resin and an acidic resin as the two or more polymers. In this case, the polymer removed in the removing step is preferably a water repellent resin.

[Immersion exposure process]
In this step, the photoresist film is subjected to immersion exposure with an immersion liquid interposed on the topcoat layer surface. This immersion exposure is usually performed by placing an immersion liquid between the surface of the topcoat layer and the objective lens of the exposure apparatus and performing exposure through this immersion liquid.

  As the immersion liquid, a liquid having a refractive index higher than that of air is usually used. As the immersion liquid, water is preferably used, and pure water is more preferably used. Note that the pH of the immersion liquid may be adjusted as necessary. In a state where the immersion liquid is interposed, that is, in a state where the immersion liquid is filled between the lens of the exposure apparatus and the photoresist film, exposure light is irradiated from the exposure apparatus to form a mask having a predetermined pattern. The photoresist film is exposed through the film.

  The exposure light used for this immersion exposure can be appropriately selected according to the type of the photoresist film or the top coat layer. For example, visible light; ultraviolet light such as g-line or i-line; far ultraviolet light such as excimer laser light; X-rays such as synchrotron radiation; charged particle beams such as electron beams. Among these, far ultraviolet rays are preferable, ArF excimer laser light (wavelength 193 nm) and KrF excimer laser light (wavelength 248 nm) are more preferable, and ArF excimer laser light is more preferable. Moreover, the exposure light irradiation conditions, for example, the exposure amount and the like can be appropriately set according to the composition of the photoresist composition and the top coat composition, the kind of additives contained therein, and the like.

  After the immersion exposure, post-exposure baking (PEB) is preferably performed in order to improve the resolution, pattern shape, developability, and the like of the resulting resist pattern. The temperature of PEB can be appropriately set depending on the type of the photoresist composition and topcoat composition used, and the lower limit thereof is preferably 50 ° C, more preferably 80 ° C. As an upper limit of the said temperature, 200 degreeC is preferable and 150 degreeC is more preferable. The lower limit of the PEB time is preferably 5 seconds, and more preferably 10 seconds. The upper limit of the time is preferably 600 seconds, and more preferably 300 seconds.

[Removal process]
In this step, a part of the top coat layer is removed. A part of the top coat layer to be removed is usually a surface layer of the top coat layer.

  When the topcoat layer contains two or more kinds of polymers having different characteristics, it is preferable to remove at least the polymer unevenly distributed on the surface side in the removing step. Moreover, when a topcoat layer has water-repellent resin and acidic resin as said 2 or more types of polymer, it is preferable that the polymer removed at a removal process is at least one part of the said water-repellent resin.

  The method for removing a part of the topcoat layer is not particularly limited. For example, a method for removing the surface layer of the topcoat layer by using a peeling solution, a method for removing the surface layer of the topcoat layer by dry etching, etc. Is mentioned. Among these, the method of using a stripping solution is preferable because it is easier and more easily adjusts the portion to be removed.

(Stripping solution)
As the stripping solution, an organic solvent is usually the main component. As a minimum of the content rate of the organic solvent in stripping solution, 50 mass% is preferred, 80 mass% is more preferred, and 95 mass% is still more preferred. As an upper limit of the said content rate, it is 100 mass%, for example.

  Examples of the organic solvent contained in the stripper include organic solvents similar to those exemplified as the organic solvent contained in the top coat composition. As these stripping solutions, those mainly containing ether solvents, hydrocarbon solvents, alcohol solvents and / or fluorine solvents are preferable.

  As the ether solvent, diisoamyl ether and dibutyl ether are preferable.

  As the hydrocarbon solvent, decane and cyclohexane are preferable.

  As the alcohol solvent, 1-decanol and 4-methyl-2-pentanol are preferable.

  As the fluorine-based solvent, perfluoro (2-butyltetrahydrofuran) is preferable.

  The stripping solution may contain an ester solvent such as propylene glycol monomethyl ether acetate in addition to the solvent mainly contained.

The solubility parameter value of the stripping solution is preferably smaller than the solubility parameter value of the [B] solvent of the topcoat composition. By setting the solubility parameter value of the stripping solution in the above range, a portion of the topcoat layer that is likely to cause defects can be more selectively and efficiently removed. Here, as the “solubility parameter”, for example, a value (unit: (MPa) ^1/2 ) described in Polymer Handbook (4th edition) (Wiley, 1999) can be used. The solubility parameter δm when the solvent is a mixed solvent of two types of solvent 1 and solvent 2 is δm = X ₁ × δ ₁ + (1−X ₁ ) × δ ₂ (where δ ₁ and δ ₂ are .X ₁ is the solubility parameter value of the solvent 1 and solvent 2 can be determined by the mole fraction of the solvent 1 in the solvent.).

  The lower limit of the value obtained by subtracting the solubility parameter value of the stripping solution from the parameter value of the solvent [B] of the top coat composition is preferably 0.1, and more preferably 0.5. The upper limit of the reduced value is preferably 8, and more preferably 5.

  The upper limit of the solubility parameter value of the stripping solution is preferably 21, more preferably 19, more preferably 18, and particularly preferably 17. As a minimum of the above-mentioned solubility parameter value, 11 is preferred and 12 is more preferred.

The stripping solution preferably satisfies the following conditions.
Condition: The photoresist film is formed on the surface of the substrate, the top coat layer having a thickness of 30 nm is further formed on the photoresist film surface, and the top solution is brought into contact with the top coat layer for 60 seconds. The coating layer is dissolved so as to remain in a thickness of 2 nm to 28 nm.

  The lower limit of the ratio of the average thickness of the topcoat layer remaining after the removal step to the average thickness of the topcoat layer formed in the laminating step (topcoat layer residual ratio) is preferably 30%, more preferably 50%, 60 % Is more preferable. The upper limit of the topcoat layer remaining rate is preferably 90%, more preferably 85%, and still more preferably 80%.

  The removal process can be performed at any time between the immersion exposure process and the development process. For example, when PEB is performed after immersion exposure, it may be performed before PEB, at the same time as PEB, or after PEB, but from the viewpoint of making the resist pattern shape better, it is preferable to perform after PEB.

  Examples of a method for removing a part of the topcoat layer using a stripping solution include a method of spin-coating the stripping solution on the topcoat layer, leaving it for a certain time, and then spin drying.

  The lower limit of the value (θ1-θ2) obtained by subtracting the receding contact angle θ2 of the topcoat layer surface after the removing step from the receding contact angle θ1 of the topcoat layer surface formed in the laminating step is preferably 10 °, 15 ° is more preferred, and 20 degrees is even more preferred. The upper limit of the above value is preferably 65 °, more preferably 55 °, and even more preferably 35 °.

[Development process]
In this step, the photoresist film is developed. This development is performed by bringing the above-described immersion-exposed photoresist film into contact with the developer. Thereby, while removing the part of the topcoat layer which was not removed in the removal process, a desired resist pattern can be obtained. If another layer is formed between the photoresist film and the topcoat layer, this other layer is also removed.

  Examples of the developer include an alkali developer and an organic solvent developer.

  Examples of alkali developers include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, dimethylethanolamine. , Triethanolamine, tetraalkylammonium hydroxides (eg, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, etc.), pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7 An alkaline aqueous solution in which at least one alkaline compound such as undecene and 1,5-diazabicyclo- [4.3.0] -5-nonane is dissolved is used. Among these, an aqueous solution of tetraalkylammonium hydroxides is preferable, and an aqueous TMAH solution is more preferable.

  Examples of the organic solvent developer include organic solvents similar to those exemplified as the organic solvent contained in the stripping solution. Among these, ether solvents, ketone solvents and ester solvents are preferable, and n-butyl acetate, isopropyl acetate, amyl acetate, anisole, 2-butanone, methyl-n-butyl ketone and methyl-n-amyl ketone are more preferable. . These organic solvents may be used alone or in combination of two or more.

  The lower limit of the content of the organic solvent in the organic solvent developer is preferably 80% by mass, more preferably 90% by mass, and even more preferably 99% by mass. By setting the content of the organic solvent in the organic solvent developer within the above range, the dissolution contrast between the exposed part and the unexposed part can be further improved, and as a result, a resist pattern having excellent lithography characteristics is formed. be able to. Examples of components other than the organic solvent include water, silicon oil, and the like.

  The developer may contain a nitrogen-containing compound. When the developer contains a nitrogen-containing compound, film loss of the formed resist pattern can be further reduced.

  Examples of nitrogen-containing compounds include (cyclo) alkylamines, nitrogen-containing heterocyclic compounds, amide group-containing compounds, urea compounds and the like.

  An appropriate amount of a surfactant can be added to the developer as necessary. As the surfactant, for example, an ionic or nonionic fluorine-based surfactant and / or a silicon-based surfactant can be used.

  As a developing method, for example, a method in which a substrate is immersed in a tank filled with a developer for a certain period of time (dip method), a method in which the developer is raised on the surface of the substrate by surface tension and is left stationary for a certain time (paddle method) ), A method of spraying the developer on the substrate surface (spray method), a method of continuously applying the developer while scanning the developer coating nozzle on the substrate rotating at a constant speed (dynamic dispensing method) Etc.

  It is preferable to include a rinsing step of washing the photoresist film with a rinsing liquid after the development step. An organic solvent can be used as the rinsing liquid in the rinsing step. By using an organic solvent as the rinsing liquid, the generated scum can be efficiently washed.

  As the organic solvent used as the rinsing liquid, hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents and amide solvents are preferable. Among these, alcohol solvents and ester solvents are more preferable, and alcohol solvents are more preferable. Among the alcohol solvents, monovalent alcohol solvents having 6 to 8 carbon atoms are preferable.

  Examples of the monohydric alcohol solvent having 6 to 8 carbon atoms include a chain monohydric alcohol, a cyclic monohydric alcohol, and the like. Specifically, 1-hexanol, 1-heptanol, 1-octanol, Examples include 4-methyl-2-pentanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, 4-octanol, and benzyl alcohol. Among these, 1-hexanol, 2-hexanol, 2-heptanol and 4-methyl-2-pentanol are preferable.

  Each component in the rinse solution can be used alone or in combination of two or more. The upper limit of the moisture content in the rinse liquid is preferably 10% by mass, more preferably 5% by mass, and still more preferably 3% by mass. By setting the water content in the rinsing liquid to the above upper limit or less, good development characteristics can be obtained. A surfactant can be added to the rinse liquid.

  As a cleaning treatment method using a rinsing liquid, for example, a method of continuously applying the rinsing liquid onto a substrate rotating at a constant speed (rotary coating method), or a method of immersing the substrate in a bath filled with the rinsing liquid for a certain period of time (Dip method), a method (spray method) of spraying a rinsing liquid on the substrate surface, and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The measuring method of various physical property values is shown below.

<Synthesis of polymer>
The monomer used for the synthesis | combination of the polymer for photoresist compositions and the polymer for topcoat compositions is shown below.

[Synthesis of polymer for photoresist composition]
[Synthesis Example 1] (Synthesis of Polymer 1)
The above compound (M-1) 53.93 g (50 mol%), the compound (M-2) 35.38 g (40 mol%) and the compound (M-3) 10.69 g (10 mol%) were mixed with 200 g of 2-butanone. And a monomer solution charged with 5.58 g of dimethyl 2,2′-azobis (2-methylpropionate) as a polymerization initiator was prepared. Next, a 500 mL three-necked flask charged with 100 g of 2-butanone was purged with nitrogen for 30 minutes. After the nitrogen purge, the reaction kettle was heated to 80 ° C. with stirring, and the monomer solution prepared above 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 reaction solution was cooled to 30 ° C. or less by water cooling, and then poured into 2,000 g of methanol, and the precipitated white powder was filtered off. The filtered white powder was washed twice by slurry using 400 g of methanol, filtered, and dried at 50 ° C. for 17 hours to obtain a white powder of polymer 1 (yield 74 g, Yield 74%). The Mw of the polymer 1 was 6,900, and Mw / Mn was 1.70. As a result of ¹³ C-NMR analysis, the content ratio of each structural unit derived from (M-1), (M-2) and (M-3) was 53.0 mol%, 37.2 mol% and 9 respectively. It was 8 mol%. Moreover, content of the low molecular weight component derived from each monomer in the polymer 1 was 0.03 mass%.

[Synthesis Example 2] (Synthesis of Polymer 2)
85 mol% of the compound (M-2) and 15 mol% of the compound (M-4) are dissolved in 200 g of 2-butanone, and azobisisobutyronitrile as a polymerization initiator is added to 7 mol of the above compounds. A monomer solution was prepared by dissolving in mol%. The total mass of the monomers used was 100 g. Next, a 500 mL three-necked flask containing 100 g of 2-butanone was heated to 80 ° C. with stirring in a nitrogen atmosphere, and the prepared monomer solution was added dropwise over 3 hours. After completion of the dropwise addition, the polymerization reaction was carried out by heating at 80 ° C. for 3 hours. After completion of the polymerization reaction, the polymerization reaction solution was cooled to room temperature. After transferring the polymerization reaction liquid to a separatory funnel, the polymerization reaction liquid was uniformly diluted with 300 g of n-hexane, and 1,200 g of methanol was added and mixed. Next, 60 g of distilled water was added, and the mixture was further stirred and allowed to stand for 30 minutes. Next, the lower layer was recovered and the solvent was replaced with propylene glycol monomethyl ether acetate to obtain a propylene glycol monomethyl ether acetate solution of polymer 2 (yield 79%). The Mw of the polymer 2 was 5,200, and Mw / Mn was 1.82. As a result of ¹³ C-NMR analysis, the content ratios of the structural units derived from (M-2) and (M-4) were 85.0 mol% and 15.0 mol%, respectively.

[Synthesis of polymer for topcoat composition]
[Synthesis Example 3] (Synthesis of Polymer 3)
A polymerization initiator solution was prepared by dissolving 25.0 g of 2,2-azobis (methyl 2-methylisopropionate) as a polymerization initiator in 25.0 g of 2-butanone. On the other hand, in a 2,000 mL three-necked flask equipped with a thermometer and a dropping funnel, 133.6 g (50 mol%) of the compound (M-4), 166.4 g (50 mol%) of the compound (M-5) and 2 -Charge 575.0 g butanone and purge with nitrogen for 30 minutes. After purging with nitrogen, the inside of the flask was heated to 80 ° C. while stirring with a magnetic stirrer. Next, using the dropping funnel, the polymerization initiator solution prepared above was dropped over 5 minutes and aged for 6 hours. Then, it cooled to 30 degrees C or less, and obtained the polymerization reaction liquid.

Subsequently, after concentrating the obtained polymerization reaction liquid to 600 g, it moved to the separatory funnel. To this separatory funnel, 193 g of methanol and 1,542 g of n-hexane were added for separation and purification. After separation, the lower layer solution was recovered. 117 g of 2-butanone and 1,870 g of n-hexane were added to the recovered lower layer solution, and separation and purification were performed. After separation, the lower layer solution was recovered. Further, 93 g of methanol, 77 g of 2-butanone and 1,238 g of n-hexane were added to the recovered lower layer solution, and separation and purification were performed. After separation, the lower layer solution was recovered. The recovered lower layer solution is substituted with 4-methyl-2-pentanol, and this solution is washed with distilled water and again substituted with 4-methyl-2-pentanol to obtain a solution containing the polymer 3. (Yield 79%). Polymer 3 had Mw of 7,700 and Mw / Mn of 1.61. As a result of ¹³ C-NMR analysis, the content ratio of each structural unit derived from (M-4) and (M-5) was 49 mol% and 51 mol%, respectively.

[Synthesis Examples 4 and 5] (Synthesis of Polymers 4 and 5)
Polymers 4 and 5 were synthesized in the same manner as in Synthesis Example 3 except that the types and amounts of monomers shown in Table 2 below were used. The yield (%) of synthesized polymers 4 and 5, Mw, Mw / Mn, and the content ratio (mol%) of structural units derived from each monomer are shown in Table 2.

[Synthesis Example 6] (Synthesis of Polymer 6)
A monomer solution prepared by dissolving 46.95 g (85 mol%) of the above compound (M-5) and 6.91 g of 2,2′-azobis (methyl 2-methylpropionate) as a polymerization initiator in 100 g of isopropanol. Prepared. On the other hand, 50 g of isopropanol was put into a 500 mL three-necked flask equipped with a thermometer and a dropping funnel, and purged with nitrogen for 30 minutes. After purging with nitrogen, the inside of the flask was heated to 80 ° C. while stirring with a magnetic stirrer. Subsequently, using the dropping funnel, the monomer solution prepared above was dropped over 2 hours. After completion of the dropwise addition, the reaction was further carried out for 1 hour. Thereafter, 10 g of an isopropanol solution of 3.05 g (15 mol%) of the above compound (M-6) was added dropwise over 30 minutes, and the reaction was further carried out for 1 hour, followed by cooling to 30 ° C. or lower to obtain a polymerization reaction solution. Obtained.

Subsequently, after concentrating the obtained polymerization reaction liquid to 150 g, it moved to the separatory funnel. The separatory funnel was charged with 50 g of methanol and 600 g of n-hexane to carry out separation and purification. After separation, the lower layer solution was recovered. This lower layer solution was diluted with isopropanol to 100 g, and again transferred to a separatory funnel. Thereafter, 50 g of methanol and 600 g of n-hexane were put into the above separatory funnel, separation and purification were performed, and the lower layer liquid was recovered after separation. The recovered lower layer liquid was replaced with 4-methyl-2-pentanol, and the total amount was adjusted to 250 g. Then, 250 g of water was added for separation and purification. After separation, the upper layer liquid was recovered. Next, the recovered upper layer liquid was replaced with 4-methyl-2-pentanol to obtain a solution containing the polymer 6 (yield 79%). The Mw of the polymer 6 was 7,950, and Mw / Mn was 1.50. As a result of ¹³ C-NMR analysis, the content ratio of each structural unit derived from (M-5) and (M-6) was 95 mol% and 5 mol%, respectively.

[Synthesis Example 7] (Synthesis of Polymer 7)
A polymer 7 was synthesized in the same manner as in Synthesis Example 6 except that the types and amounts of monomers shown in Table 2 were used. Table 2 shows the yield (%) of the synthesized polymer 7, Mw, Mw / Mn, and the content ratio (mol%) of the structural unit derived from each monomer.

<Preparation of composition>
[Preparation of photoresist composition]
[Preparation Example 1] (Preparation of photoresist composition 1)
100 parts by weight of polymer 1, 1.5 parts by weight of triphenylsulfonium nonafluoro-n-butanesulfonate as a radiation sensitive acid generator and 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium 6 parts by weight of nonafluoro-n-butanesulfonate and 0.65 parts by weight of R-(+)-(tert-butoxycarbonyl) -2-piperidinemethanol as an acid diffusion controller were mixed, and this mixture was mixed with By adding 2,900 parts by mass of propylene glycol monomethyl ether acetate, 1,250 parts by mass of cyclohexanone and 100 parts by mass of γ-butyrolactone, adjusting the solid content concentration to 5% by mass, and filtering through a filter with a pore size of 30 nm, Resist composition 1 was prepared.

[Preparation Example 2] (Preparation of photoresist composition 2)
97 parts by mass of polymer 1, 3 parts by mass of polymer 2, 1.5 parts by mass of triphenylsulfonium nonafluoro-n-butanesulfonate as a radiation-sensitive acid generator and 1- (4-n-butoxynaphthalene- 1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate 6 parts by mass and R-(+)-(tert-butoxycarbonyl) -2-piperidinemethanol 0.65 part by mass as an acid diffusion controller were mixed. To this mixture, 2,900 parts by mass of propylene glycol monomethyl ether acetate as a solvent, 1,250 parts by mass of cyclohexanone and 100 parts by mass of γ-butyrolactone were added to adjust the solid content concentration to 5% by mass, and the pore diameter was 30 nm. Photoresist composition 2 was prepared by filtering with a filter.

[Preparation of Topcoat Composition]
[Preparation Example 3]
30 parts by mass of polymer 3 and 70 parts by mass of polymer 6 were mixed, and 1,000 parts by mass of 4-methyl-2-pentanol and 4,000 parts by mass of diisoamyl ether as a solvent were added to this mixture. The top coat composition 1 was prepared by filtering with a filter having a pore diameter of 30 nm.

[Preparation Examples 4 to 6]
Topcoat compositions 2 to 4 were prepared in the same manner as Preparation Example 3, except that the components having the types and contents shown in Table 3 below were used. “DEMNUM S-20” (Daikin Industries) used for the preparation of the top coat composition 4 is a chain perfluoroalkyl polyether represented by the following formula (p-1), and “CYTOP” (Asahi Glass Co., Ltd.) is a cyclic perfluoroalkyl polyether represented by the following formula (p-2).

<Formation of resist pattern>
[Examples 1 to 13 and Comparative Examples 1 to 4]
After spin coating with a coating / development device (“Lithius Pro-i” from Tokyo Electron) on the surface of a 12-inch silicon wafer with a composition for an antireflection film (“ARC66” from Nissan Chemical Industries, Ltd.) , PB was performed to form a lower antireflection film having an average thickness of 105 nm. Next, using the coating / developing apparatus, a photoresist composition shown in Table 4 below was spin coated, PB was performed at 90 ° C. for 60 seconds, and then cooled at 23 ° C. for 30 seconds to obtain an average thickness. A 90 nm photoresist film was formed. Next, a top coat composition shown in Table 4 below was applied to the surface of the photoresist film, and a top coat layer having an average thickness of 30 nm was formed by performing PB at 90 ° C. for 60 seconds.

  Next, using an ArF immersion exposure apparatus (“S610C” manufactured by Nikon Corporation), exposure was performed through a 45 nm line / 90 nm pitch pattern formation mask under the optical conditions of NA: 1.30 and Dipole. Next, after rinsing with ultrapure water for 60 seconds in the above-mentioned Lithius Pro-i PIR module, it was allowed to stand for 60 seconds with water droplets attached. Next, PEB was performed on a hot plate at 90 ° C. for 60 seconds and cooled at 23 ° C. for 30 seconds.

  Next, a part of the topcoat layer was peeled off by spin coating a stripping solution shown in Table 4 below (the ratio when the stripping solution is a mixed solvent is a mass ratio). Subsequently, paddle development was performed for 10 seconds using a 2.38 mass% TMAH aqueous solution as a developer. Thereafter, spin drying was performed by swinging off at 2,000 rpm for 15 seconds to obtain a substrate on which a resist pattern was formed. “-” In Comparative Example 1 indicates that peeling with a stripping solution was not performed.

<Evaluation>
In the formation of the resist pattern, according to the following method, the receding contact angle (°), the topcoat layer remaining rate (%), the watermark defect and the residue defect on the surface of the topcoat layer before and after partial peeling are evaluated. did. The evaluation results are shown in Table 4.

[Backward contact angle of the surface of the topcoat layer before and after partial peeling]
The receding contact angle of water on the surface of each topcoat layer was measured before and after partial peeling of the topcoat layer. A topcoat composition is spin-coated on an 8-inch silicon wafer, and PB is performed on a hot plate at 90 ° C. for 60 seconds to obtain a substrate (partially before peeling) on which a 30 nm-thick topcoat layer is formed. It was. Next, after spin-coating the stripping solution shown in Table 4 below on the topcoat layer of this substrate, it was allowed to stand for 60 seconds, and then spin-dried by shaking off at 2,000 rpm for 15 seconds, so that the partially peeled surface was removed. A substrate on which a top coat layer was formed was obtained.

  Using the contact angle meter (“DSA-10” from KRUS) for each of the substrates on which the top coat layer was formed before and after partial peeling was obtained, the room temperature was 23 ° C. and humidity was quickly The receding contact angle was measured by the following procedure under an environment of 45% normal pressure.

  First, the wafer stage position of the contact angle meter was adjusted, and the wafer was set on the adjusted stage. Next, water was injected into the needle, and the position of the needle was finely adjusted to an initial position where water droplets could be formed on the set wafer. Thereafter, water was discharged from the needle to form a 25 μL water droplet on the wafer. The needle was once pulled out from the water droplet, and the needle was pulled down again at the initial position and placed in the water droplet. Subsequently, a water droplet was sucked with a needle at a speed of 10 μL / min for 90 seconds, and at the same time, the contact angle was measured once per second for a total of 90 times. Among these, the average value for the contact angle for 20 seconds from the time when the measured value of the contact angle was stabilized was calculated and used as the receding contact angle (unit: (°)).

[Topcoat layer remaining rate]
The average thickness after partial peeling of the topcoat layer was measured to determine the topcoat layer remaining rate. A photoresist composition having an average thickness of 90 nm is coated on an 8-inch silicon wafer using a spin coater (“CLEAN TRACK ACT8” manufactured by Tokyo Electron Ltd.) and then heated at 90 ° C. for 60 seconds. A film was formed. Next, the top coat composition was applied using the spin coater and heated at 90 ° C. for 60 seconds to form a top coat layer having an average thickness of 30 nm. Next, after the top coat layer formed on the surface of the photoresist film was peeled off using the stripping solution shown in Table 4 below, the average thickness of the remaining top coat layer was measured. The residual ratio (%) of the topcoat layer with respect to the average thickness of 30 nm was determined.

[Watermark defect suppression and residue defect suppression]
About the board | substrate with which the said resist pattern was formed, the defect inspection apparatus ("KLA2810" of KLA-Tencor) and the inspection by a scanning electron microscope ("RS6000" of Hitachi High-Technologies) are performed. Thus, the number of watermark defects and residue defects were respectively measured. The watermark defect inhibiting property was evaluated as “◯” when the number of watermark defects was 0 per wafer, and “X” when the number was 1 or more. “-” In Comparative Example 1 indicates that measurement is not possible because there are many residual defects. Residual defect suppression was evaluated as “◯” when the number of residual defects was 100 or less per wafer, and “X” when it exceeded 100.

  As can be seen from the results in Table 4, according to the resist pattern forming method of the example, both the generation of watermark defects and residue defects can be suppressed. On the other hand, in the resist pattern forming method of the comparative example, the occurrence of residue defects cannot be suppressed.

  According to the resist pattern forming method of the present invention, a resist pattern with few watermark defects and residue defects can be formed. Therefore, the resist pattern forming method can be suitably used for a semiconductor device processing process and the like that are expected to be further miniaturized in the future.

Claims (8)

Applying the photoresist composition directly or indirectly to the substrate surface;
A step of directly or indirectly laminating a top coat layer on the photoresist film surface obtained by this coating step;
A step of immersion exposure of the photoresist film with an immersion liquid interposed on the topcoat layer surface;
A step of developing the photoresist film,
A resist pattern forming method comprising a step of removing a part of the topcoat layer between the immersion exposure step and the development step.   The resist pattern forming method according to claim 1, wherein the removal in the removing step is performed using a stripping solution. The resist pattern forming method according to claim 2, wherein the stripping solution satisfies the following conditions.
Condition: The photoresist film is formed on the surface of the substrate, the top coat layer having a thickness of 30 nm is further formed on the photoresist film surface, and the top solution is brought into contact with the top coat layer for 60 seconds. The coating layer is dissolved so as to remain in a thickness of 2 nm to 28 nm. The top coat layer contains two or more polymers having different characteristics,
The resist pattern forming method according to claim 1, wherein the polymer unevenly distributed at least on the surface side is removed in the removing step. As the two or more kinds of polymers, a water repellent resin and an acidic resin are included,
The resist pattern forming method according to claim 4, wherein the polymer removed in the removing step is at least a part of the water-repellent resin.   The resist pattern forming method according to claim 2, wherein the stripping solution contains an organic solvent as a main component.   The resist pattern forming method according to claim 6, wherein a solubility parameter value of the stripping solution is smaller than a solubility parameter value of a solvent contained in the composition forming the top coat layer.   The method for forming a resist pattern according to claim 6, wherein the organic solvent mainly contains an ether solvent.