JP2010039148A - Production method for composition for forming liquid immersion upper layer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for a composition for forming a liquid immersion upper layer film can reduce an impurity such as metal. <P>SOLUTION: This production method for the composition for forming the liquid immersion upper layer film includes a process for bringing a monomer for a liquid immersion upper layer polymer or a polymerization solution obtained by polymerizing the monomer, into contact with an ion exchange resin having a cation exchange group. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a composition for forming a liquid immersion upper layer film, and particularly relates to a method for producing a composition for forming a liquid immersion upper layer film with less impurities such as metals.

  In the semiconductor manufacturing process, in recent years, a technique called immersion lithography has been proposed. In this technique, exposure is performed by immersing a liquid such as water having a refractive index higher than that of air between the objective lens and the lithography thin film. This technique increases the numerical aperture of the lens even when the wavelength of the light source is the same, as compared with lithography in which an air layer exists between the objective lens and the thin film (hereinafter sometimes referred to as “dry lithography”). In addition, since the depth of focus can be increased even if the numerical aperture is the same, it is possible to form a finer pattern even with a light source having the same wavelength.

  When performing immersion exposure, the photoresist film applied and formed on the wafer and the lens of the projection exposure apparatus are in contact with the medium. For example, when water is used as a medium, water may penetrate into the photoresist film, and the resolution of the photoresist may be reduced. In addition, the lens surface of the projection exposure apparatus may be contaminated by elution of components constituting the photoresist into water.

For this reason, there is a method of forming an upper layer film on the photoresist film for the purpose of blocking the photoresist film from a medium such as water. As the upper layer film, it has sufficient permeability to the wavelength of radiation, can form a protective film on the photoresist film with little intermixing with the photoresist film, and further, water etc. at the time of immersion exposure It is necessary to form an upper layer film that maintains a stable film without eluting into the medium and easily dissolves in an alkaline solution or the like as a developer (Patent Document 1).
JP 2006-47351 A

  The composition for forming an upper layer film comprises a polymer component for a liquid immersion upper layer film and a solvent, and the polymer component is usually isolated by a separation operation after polymerizing monomers. However, the composition for forming a liquid immersion upper layer film thus obtained has a problem that desired performance cannot be obtained because it contains impurities such as metal components. In particular, when sodium, iron, or the like is included, the electrical characteristics of the semiconductor deteriorate.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to provide a method for producing a composition for forming a liquid immersion upper layer film with less impurities such as metals. It is in.

  As a result of intensive investigations for achieving the above object, the present inventors have found a production method capable of reducing the presence of the contained metal in the composition for forming a liquid immersion upper layer film. That is, according to this invention, the manufacturing method shown below is provided.

[1] For forming a liquid immersion upper film comprising a step of contacting a monomer of a polymer for liquid immersion upper film or a polymerization solution obtained by polymerizing the monomer with an ion exchange resin having a cation exchange group A method for producing the composition.

[2] The method for producing a composition for forming a liquid immersion upper film according to [1], wherein the ion exchange resin is an ion exchange membrane.

[3] The method for producing a composition for forming a liquid immersion upper layer according to the above [2], wherein the ion exchange membrane has a cation exchange group on any one of a polyolefin, a polysaccharide, and a fluoropolymer.

[4] The method for producing a composition for forming a liquid immersion upper film according to the above [3], wherein the substrate of the ion exchange membrane is polyolefin.

[5] The polymer monomer for immersion upper layer film or a polymerization solution obtained by polymerizing the monomer is brought into contact with an ion exchange resin having a cation exchange group at 10 to 200 L / hrm ² [1] ] The manufacturing method of the composition for liquid immersion upper film formation in any one of [4].

[6] For forming a liquid immersion upper layer film according to any one of the above [1] to [5], comprising a step of bringing a monomer of the polymer for liquid immersion upper layer film into contact with an ion exchange resin having a cation exchange group A method for producing the composition.

[7] Any one of the above [1] to [6], comprising a step of contacting a polymer solution obtained by polymerizing the monomer of the polymer for immersion upper layer membrane with an ion exchange resin having a cation exchange group The manufacturing method of the composition for liquid immersion upper film formation as described in any one of.

[8] A composition for forming a liquid immersion upper film, wherein the Na content is 50 ppb or less, the Fe content is 50 ppb or less, and the Ni content is 50 ppb or less.

  The composition for forming a liquid immersion upper layer film obtained by the production method of the present invention is a composition from which a metal component has been sufficiently removed, and is a composition for forming an upper film for immersion that does not cause a metal-derived defect or performance deterioration. is there. According to the method for producing a composition for forming a liquid immersion upper film of the present invention, the metal component in the composition for forming a liquid immersion upper film can be sufficiently removed.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

[1. Ion exchange process]
The manufacturing method of the composition for forming a liquid immersion upper layer film of the present invention includes an ion exchange step. This step is a step of bringing a monomer of the polymer for an immersion upper layer film or a polymerization solution obtained by polymerizing the monomer into contact with an ion exchange resin having a cation exchange group.

  Although there is a method of removing by metal washing as a metal removal method, since the polymer monomer obtained by polymerizing the liquid immersion upper layer film polymer or the monomer has an acidic functional group, it is efficient in water washing. Metal removal cannot be performed well, and removal with an ion exchange resin is preferable.

  Various conventionally known methods can be employed as a method for bringing the monomer of the polymer for the liquid immersion upper layer film or the polymerization solution obtained by polymerizing the monomer into contact with the ion exchange resin. Even if the ion exchange resin is in the form of a filter or particles, in the method of filling the column with the ion exchange resin and letting the liquid flow therethrough, the liquid passing method to the ion exchange resin is an inert gas pressurization, Alternatively, liquid feeding by a pump is preferable, and either a dead end system or a circulation system liquid may be used. When the ion exchange resin is in the form of particles, the particulate ion exchange resin is directly charged into the polymer monomer for the liquid immersion upper layer film or the polymerization solution obtained by polymerizing the monomer, and then contacted. Can be adopted.

10-200 L / hrm < ² > is preferable and the liquid flow rate to an ion exchange resin has more preferable 20-150 L / hrm < ² >. Productivity deteriorates at 10 L / hrm ² or less, and when it is 200 L / hrm ² or more, a polymer obtained by polymerizing an ion exchange resin and a monomer for an upper layer film for immersion, or the aforementioned monomer. The contact time with the metal becomes shorter and the metal removal efficiency becomes worse.

  The temperature at the time of contacting with the ion exchange resin is usually 0 to 80 ° C., preferably about 10 to 50 ° C. If the temperature is too high, the ion exchange resin may be deteriorated and the solvent may be decomposed. If the temperature is too low, the solution viscosity becomes high and liquid passing tends to be difficult.

  The ion exchange step can be performed in one or both of a monomer state and a polymerization solution obtained by polymerizing the monomer.

By contacting the monomer of the polymer for the liquid immersion upper layer film or the polymerization solution obtained by polymerizing the monomer with an ion exchange resin, metal ions such as sodium ions and iron ions contained in the solution can be obtained. A polymer solution having a metal content (on a polymer basis) of, for example, 50 ppb or less, preferably 20 ppb or less, can be obtained efficiently. For this reason, when the composition for forming an upper layer film for immersion obtained by this method is used, the electrical characteristics of the semiconductor and the like are not adversely affected.
[1-1. Ion exchange resin]
The ion exchange resin used in the present invention is preferably an ion exchange resin having a cation exchange group. Here, the ion exchange resin is a polymer in which a cation exchange group is introduced into a polymer such as a styrene polymer, an acrylic polymer, a polyester polymer, cellulose, or tetrafluoroethylene. Further, since the monomer for the liquid immersion upper layer polymer or the polymer obtained by polymerizing the monomer has an acidic functional group, the acidic functional group is a simple substance for the polymer for the liquid immersion upper layer film. It is preferable that the acid is stronger or equivalent to the functional group of the polymer obtained by polymerizing the monomer or the monomer.

  The cation exchange groups of the ion exchange resin include strongly acidic cation exchange groups such as sulfonic acid groups and weak acid cation exchange groups such as carboxyl groups. The cation exchange group possessed by the ion exchange resin is preferably a strongly acidic cation exchange group such as a sulfonic acid group. Here, a styrene polymer crosslinked with divinylbenzene as an ion exchange resin having a strongly acidic cation exchange group is sulfonated, and an acrylic acid or methacrylic polymer crosslinked with divinylbenzene as an ion exchange resin having a weak acid cation exchange group. Examples are those obtained by carboxylation.

  Since the substrate of the ion exchange resin may corrode the substrate due to the acidity of the polymer monomer for immersion upper layer polymer or the polymer obtained by polymerizing the monomer, it is resistant to acidity. Certain substrates are preferred. Polyolefins, polysaccharides, and fluorine-based polymers are preferable, and polyolefins and fluorine-based polymers are more preferable. Polyethylene and polypropylene are preferable as the polyolefin substrate, cellulose is preferable as the polysaccharide, and tetrafluoroethylene is preferable as the fluoropolymer substrate.

  The form of the ion exchange resin is not particularly limited, and may be any shape such as a particulate form, a fibrous form, a porous film form, or a porous film form composed of a strong acid cation exchange group, a weak acid cation exchange group. . Examples of the particulate form include forms such as a styrene polymer crosslinked with divinylbenzene, and those having a particle size of about 0.05 mm to 50 mm can be exemplified. Those having a filter configuration are more preferable than particles. This is because particles in the particulate form diffuse into the resin and come into contact with the ion exchange groups, whereas in the membrane type, the ion exchange groups are also present in the pores, while the liquid passes through the pores. This is because ions in the liquid come into contact with the ion exchange group. Since the ions flowing through the pores always come into contact with the ion exchange group, the efficiency is preferable.

  The filter made of an ion exchange resin having a cation exchange group is preferably a hydrophilic filter. For example, trade name “Zeta Plus EC (SH)” manufactured by Cuno Co., Ltd., trade name “Protego” manufactured by Nihon Entegris, Japan The product name “AEON CLEAN” manufactured by Pole Corporation can be suitably used.

[2. Other processes]
Manufacture of polymer for immersion film:
In the manufacturing method of the composition for liquid immersion upper film | membrane formation of this invention, in addition to the above-mentioned ion exchange process, the manufacturing process of the polymer for liquid immersion upper film | membranes is included. In one embodiment of the production process of the polymer for the liquid immersion upper layer film, the monomer (A) represented by the following general formula (1) (hereinafter simply referred to as “single amount”) is added to the solvent heated to a polymerizable temperature. The first monomer solution containing the polymer (A) ”and the radical polymerization initiator are respectively added dropwise to perform a polymerization reaction to obtain a polymer solution (hereinafter referred to as“ the first product ”). And a second monomer solution containing the monomer (B) having an acidic functional group is added dropwise to the obtained polymer solution, A step of obtaining a copolymer solution containing a copolymer used as a material for forming an upper layer film for immersion exposure (hereinafter sometimes referred to as “second polymerization step”). I have it. Such a method for producing a copolymer can provide a copolymer that is a material for forming an upper layer film for immersion exposure in which watermark defects and undissolved defects are unlikely to occur.

(However, in the general formula ^{(1), R 1, R} 2 and ^{R 3} are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a hydroxymethyl group, a trifluoromethyl group or a phenyl group, A represents a single bond, an oxygen atom, a carbonyl group, a carbonyloxy group, or an oxycarbonyl group, B represents a single bond or a divalent organic group having 1 to 20 carbon atoms, and R ⁴ represents Represents a monovalent organic group having 1 to 20 carbon atoms, and R ⁵ represents a perfluoroalkyl group.)

[2-1] First polymerization step:
In the production of the polymer for a liquid immersion upper layer film according to the present embodiment, first, the first solvent containing the monomer (A) represented by the general formula (1) is contained in the solvent heated to a polymerizable temperature. The monomer solution and the radical polymerization initiator are added dropwise to perform a polymerization reaction to obtain a polymer solution. In this step, the first monomer solution and the radical polymerization initiator (radical polymerization initiator solution) are dropped separately, so the monomer (A) and the radical polymerization initiator are mixed solution. After that, compared to the case where it is dropped into the reaction system (in the solvent), for example, there is less generation of organic substances (by-products) that induce defects such as low molecular weight oligomers, residual monomers, and ultrahigh molecular weight polymers. There are advantages.

  That is, when the monomer (A) and the radical polymerization initiator are mixed, the monomer (A) is polymerized by the radical polymerization initiator until the mixed solution is dropped or is dropped. Therefore, there is a problem that organic substances that induce defects are generated. And this organic substance becomes a cause which produces a defect (for example, watermark defect and undissolved defect) in the resist pattern surface formed in the immersion lithography process. The production method of the copolymer of the present embodiment can prevent the formation of such organic substances.

  Examples of the solvent used in this step include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, ethylene glycol, diethylene glycol, and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane. Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol monomethyl ether, propylene glycol Alkyl ethers of polyhydric alcohols such as ethyl ether;

  Alkyl ether acetates of polyhydric alcohols such as ethylene glycol ethyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate; aromatic hydrocarbons such as toluene and xylene; acetone, methyl ethyl ketone, methyl isobutyl Ketones such as ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol; ethyl acetate, butyl acetate, methyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, 2- Ethyl hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, 3-metho Methyl Shipuropion acid, 3-methoxy ethyl propionate, ethyl 3-ethoxypropionate, and the like esters such as 3-ethoxymethyl propionate.

  Among these, cyclic ethers, polyhydric alcohol alkyl ethers, polyhydric alcohol alkyl ether acetates, ketones, and esters are preferable. In addition, these solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

  Although the temperature of a solvent can be set suitably, it is preferable that it is 50-150 degreeC, it is still more preferable that it is 55-140 degreeC, and it is especially preferable that it is 60-120 degreeC.

Examples of the alkyl group having 1 to 10 carbon atoms of R ¹ , R ² , or R ³ in the monomer (A) represented by the general formula (1) include a methyl group, an ethyl group, a propyl group, and butyl. Group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and the like. Among these, R ¹ is preferably a hydrogen atom or a methyl group, and R ² and R ³ are each preferably a hydrogen atom.

  Examples of the divalent organic group having 1 to 20 carbon atoms of B in the monomer (A) represented by the general formula (1) include, for example, a methylene group, an ethylene group, a 1,3-propylene group, or 1, Propylene groups such as 2-propylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, tridecamethylene group, tetra Decamemethylene group, pentadecamethylene group, hexadecamethylene group, heptadecamethylene group, octadecamethylene group, nonadecamethylene group, icosalen 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, 2-methyl-1,4-butyl Ren group, methylidene group, ethylidene group, propylidene group, or 2-propylidene saturated chain hydrocarbon groups such as,

  Cyclobutylene groups such as 1,3-cyclobutylene groups, cyclopentylene groups such as 1,3-cyclopentylene groups, cyclohexylene groups such as 1,4-cyclohexylene groups, 1,5-cyclooctylene groups, etc. A monocyclic hydrocarbon ring group such as a cycloalkylene group having 3 to 10 carbon atoms such as a cyclooctylene group, a norbornylene group such as a 1,4-norbornylene group or a 2,5-norbornylene group, and 1,5-adamantylene And a bridged cyclic hydrocarbon ring group such as a 2-4 cyclic hydrocarbon group having 4 to 20 carbon atoms such as an adamantylene group such as a 2,6-adamantylene group.

  When B is a divalent aliphatic cyclic hydrocarbon group, an alkylene group having 1 to 4 carbon atoms is used as a spacer between the bisperfluoroalkyl-hydroxy-methyl group and the aliphatic cyclic hydrocarbon group. It is preferable to insert.

  In the general formula (1), A is preferably a carbonyloxy group, and B is a 2,5-norbornylene group, a hydrocarbon group containing a 2,6-norbornylene group, or a 1,2-propylene group. Is preferred.

R ⁴ in the general formula (1) represents a monovalent organic group having 1 to 20 carbon atoms. Examples of the monovalent organic group having 1 to 20 carbon atoms include monovalent organic groups having 1 to 20 carbon atoms. A hydrocarbon group, a C1-C20 fluoroalkyl group, etc. can be mentioned.

  Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a propyl group such as a methyl group, an ethyl group, a 1,3-propyl group or a 1,2-propyl group, a butyl group, a pentyl group, a hexyl group, Heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, insal, 1-methyl-1,3- Propyl group, 2-methyl-1,3-propyl group, 2-methyl-1,2-propyl group, 1-methyl-1,4-butyl group, 2-methyl-1,4-butyl group, methylidene group, Saturated chain hydrocarbon groups such as ethylidene group, propylidene group or 2-propylidene group; allyl groups such as phenyl group and tolyl group;

  3 carbon atoms such as cyclobutyl group such as 1,3-cyclobutyl group, cyclopentyl group such as 1,3-cyclopentyl group, cyclohexyl group such as 1,4-cyclohexyl group, cyclooctyl group such as 1,5-cyclooctyl group, etc. Monocyclic hydrocarbon ring groups such as 10 to 10 cycloalkyl groups; norbornyl groups such as 1,4-norbornyl groups or 2,5-norbornyl groups, adamantyl groups such as 1,5-adamantyl groups and 2,6-adamantyl groups A monovalent chain derived from a polyalkylene glycol having 1 to 10 carbon atoms such as polyethylene glycol and polypropylene glycol; a bridged cyclic hydrocarbon ring group such as a hydrocarbon ring group having 2 to 4 cyclic carbon atoms and 4 to 20 carbon atoms such as a group; And the like.

  Examples of the fluoroalkyl group having 1 to 20 carbon atoms include difluoromethyl group, perfluoromethyl group, 1,1-difluoroethyl group, 2,2,2-trifluoroethyl group, perfluoroethyl group, 1,1 , 2,2-tetrafluoropropyl group, perfluoroethylmethyl group, perfluoropropyl group, 1-trifluoromethyl-1,2,2,2-tetrafluoroethyl group, 1,1,2,2,3 3-hexafluorobutyl group, perfluorobutyl group, 1,1-bis (trifluoromethyl) -2,2,2-trifluoroethyl group, 1,1-dimethyl-2,2,3,3-tetrafluoro Propyl group, 1,1-dimethyl-2,2,3,3,3-pentafluoropropyl group, 2- (perfluoropropyl) ethyl group, 1,1,2,2,3,3,4, -Octafluoropentyl group, perfluoropentyl group, 1,1-dimethyl-2,2,3,3,4,4-hexafluorobutyl group, 1,1-dimethyl-2,2,3,3,4, 4,4-heptafluorobutyl group, 2- (perfluorobutyl) ethyl group, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl group, perfluoropentylmethyl group, Perfluorohexyl group,

  1,1-dimethyl-2,2,3,3,4,4,5,5-octafluoropentyl group, 1,1-dimethyl-2,2,3,3,4,4,5,5,5 -Nonafluoropentyl group, 2- (perfluoropentyl) ethyl group, 1,1,2,2,3,3,4,4,5,5,6,6-dodecafluoroheptyl group, perfluorohexylmethyl group Perfluoroheptyl group, 2- (perfluorohexyl) ethyl group, 1,1,2,2,3,3,4,4,5,5,6,6,7,7-tetradecafluorooctyl group, Perfluoroheptylmethyl group, perfluorooctyl group, 2- (perfluoroheptyl) ethyl group, 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8 , 8-Hexadecafluorononyl group, perfluorooctylmethyl group, perful Rononyl group, 2- (perfluorooctyl) ethyl group, 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-octa Decafluorodecyl group, perfluorononylmethyl group, perfluorodecyl group, 2,2,3,3,4,4-hexafluorobutyl group, 2,2,3,3,4,4,4-heptafluorobutyl Group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, 3,3,4,4,5,5,6,6,7,7,8,8,8 -A tridodecafluorooctyl group etc. can be mentioned.

  Among these, since an upper layer film for immersion exposure that hardly causes undissolved defects can be formed well, a methyl group, an ethyl group, an isopropyl group, a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group The group 1,1-difluoroethyl group is preferred.

R ⁵ in the general formula (1) represents a perfluoroalkyl group. Examples of the perfluoroalkyl group include a perfluoromethyl group, a perfluoroethyl group, a perfluoroethylmethyl group, a perfluoropropyl group, 1- Trifluoromethyl-1,2,2,2-tetrafluoroethyl group, perfluorobutyl group, 1,1-bistrifluoromethyl-2,2,2-trifluoroethyl group, perfluoropentyl group, perfluoropentylmethyl Group, perfluorohexyl group, perfluorohexylmethyl group, perfluoroheptyl group, perfluoroheptylmethyl group, perfluorooctyl group, perfluorooctylmethyl group, perfluorononyl group, perfluorodecyl group and the like. .

  Among these, since it is possible to satisfactorily ensure water repellency against an immersion solvent such as water required for the upper layer film for immersion exposure, a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, 1- A trifluoromethyl-1,2,2,2-tetrafluoroethyl group is preferred.

  The content ratio of the repeating unit derived from the monomer (A) is preferably 30 to 99.7 mol%, and preferably 40 to 99.5 mol%, based on all repeating units of the copolymer. Is more preferable. When the content is less than 30 mol%, the water repellency derived from the fluorine group in the side chain is lowered, and a part of the resin composition is eluted into the immersion exposure solvent. May contaminate the surface. On the other hand, if it exceeds 99.7 mol%, the solubility of the resulting copolymer in an alkaline developer may be low, and development may not be possible.

  In addition, the conditions for dropping the monomer (A) can be appropriately set.

  The first monomer solution can contain other monomers in addition to the monomer (A) represented by the general formula (1).

  Other monomers are not particularly limited as long as they are radically polymerizable monomers, and can be appropriately selected and used. Among these, from the viewpoint that it is possible to satisfactorily form an upper layer film for immersion exposure in which watermark defects and undissolved defects are unlikely to occur, that is, it is further difficult to generate organic substances that cause these defects. In view of the above, acrylic acid, methacrylic acid, ester monomers thereof, and general vinyl monomers can be used. The content ratio of the other monomers in the first monomer solution is preferably 0 to 50 parts by mass, and 0 to 40 parts by mass with respect to 100 parts by mass of the monomer (A). It is further more preferable and it is especially preferable that it is 0-30 mass parts.

  Examples of the radical polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), dimethyl 2,2′-azobisisobutyrate, 1,1′- Azo compounds such as azobis (cyclohexane-1-carbonitrile) and 4,4′-azobis (4-cyanovaleric acid); decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, bis (3,5,5-trimethyl) And organic peroxides such as hexanoyl peroxide, succinic acid peroxide, and tert-butylperoxy-2-ethylhexanoate. In addition, these may be used individually by 1 type and may be used in combination of 2 or more type.

  Moreover, in this process, you may use a chain transfer agent suitably. Examples of the chain transfer agent include thiol compounds such as dodecyl mercaptan, mercaptoethanol, mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, and 4,4-bis (trifluoromethyl) -4-hydroxy-1-mercaptobutane. be able to. In addition, these may be used individually by 1 type and may be used in combination of 2 or more type.

  The amount of radical polymerization initiator and chain transfer agent used should be set as appropriate according to the production conditions such as monomers used in the polymerization reaction, polymerization initiator, type of chain transfer agent, polymerization temperature, polymerization reaction solvent, polymerization method, and purification conditions. Can do.

  The conditions for dropping the radical polymerization initiator can be set as appropriate, but it is preferable to drop any amount over 10 minutes to 8 hours.

  The manufacturing process of the polymer for immersion upper layer film of this embodiment performs a polymerization reaction, dripping the 1st monomer solution and the radical polymerization initiator, respectively. Specifically, the first monomer solution and the radical polymerization initiator solution are respectively stored in separate tanks and appropriately dropped from each tank during the polymerization reaction. By storing in a separate tank in this way, that is, by not mixing the first monomer solution and the radical polymerization initiator in advance, by-products are prevented from being generated before the polymerization reaction. can do.

  As an apparatus for performing the polymerization reaction in this step, for example, the first monomer solution is stored and a monomer tank having a discharge port, a radical polymerization initiator is stored, and a start having a discharge port is stored. An agent tank and a polymerization reaction tank that has been previously charged with a solvent and that has a charging port can be exemplified. The apparatus is connected to a discharge port of the monomer tank, and is connected to a first pipe disposed so that a tip thereof is located above the input port of the polymerization reaction tank, and a discharge port of the initiator tank. And a second pipe arranged so that its tip is positioned above the inlet of the polymerization reaction tank, and a liquid feed pump and an opening and closing respectively in the middle of the first pipe and the second pipe A valve is provided. Further, the polymerization reaction tank is provided with a temperature controller having a heater capable of controlling the reaction temperature by raising the temperature of the solvent therein.

  Although conventionally known conditions can be adopted as the conditions for the polymerization reaction in this step, polymerization is preferably performed at 50 to 110 ° C. for 1 to 10 hours, and further preferably at 55 to 110 ° C. for 1 to 8 hours. Preferably, it is 1 to 6 hours at 60 to 110 ° C., particularly preferably.

[2-2] Second polymerization step:
Next, in the production of the polymer for an immersion upper layer film of the present embodiment, a second monomer solution containing the monomer (B) having an acidic functional group is added to the obtained polymer solution. A step of dropping to obtain a copolymer solution containing a copolymer used as a material for forming an upper layer film for immersion exposure is performed. By performing this step after the first polymerization step, the monomer (B) can be added only to the end of the polymer in the polymer solution obtained in the first polymerization step, The number of molecules of the monomer (B) to be added can be adjusted to a certain number.

  When such a second polymerization step is not performed, that is, a monomer (B) such as an acrylic, (meth) acrylic, or vinyl compound monomer having an acidic functional group is converted into a monomer (A ), It is difficult to control the monomer composition ratio in the resulting copolymer. It is also difficult to obtain a copolymer having a desired molecular weight and molecular weight distribution. For these reasons, it is effective to perform the second polymerization step.

  When the first polymerization step and the second polymerization step are performed as described above, it is possible to control the primary structure of the copolymer and the amount of the monomer (B) introduced. In other words, since the amount of the monomer (B) introduced into the copolymer can be adjusted satisfactorily, the repeating unit derived from the monomer (A) and the monomer (B ) Can be appropriately controlled. Accordingly, a copolymer having a narrow molecular weight distribution and a uniform degree of polymerization can be obtained. When this copolymer is used as a material, it is possible to form an upper layer film that is not easily eluted in an immersion medium during immersion exposure, is stable, and can be easily dissolved in an alkaline solution as a developer. Therefore, in combination with the fact that by-product formation can be prevented by the first polymerization step and that the molecular weight distribution of the copolymer is narrow and the degree of polymerization is uniform, watermark defects, etc. Generation of defects derived from the immersion exposure process can be effectively suppressed.

The monomer (B) having an acidic functional group contained in the second monomer solution is not particularly limited as long as radical polymerization is possible, but the following general formula (2) and general formula (3) The compounds represented are preferred. By using these compounds, good solubility with respect to an alkaline developer is expressed, so that there is an advantage that defects are hardly generated on the resist pattern.

(However, in said general formula (2) and (3), R < ⁶ > -R < ¹¹ > represents a hydrogen atom or a methyl group each independently, X is a single bond, a methylene group, or a C2-C6 straight. Represents a chain or branched alkylene group, and Y represents a single bond, a methylene group, a linear, branched or cyclic alkylene group having 2 to 6 carbon atoms, or a straight chain having 2 to 6 carbon atoms having an amide bond. Represents a linear or branched alkylene group or an aromatic hydrocarbon compound.)

  Specifically, the monomer (B) is acrylic acid, (meth) acrylic acid, vinyl sulfonic acid, allyl sulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, 4-vinyl-1- Benzenesulfonic acid is preferred. By using these compounds, it is possible to control the insolubility in the immersion solvent, and there are advantages such that defects are less likely to occur.

  The content of the repeating unit derived from the monomer (B) is preferably 0.1 to 50 mol%, and preferably 0.5 to 40 mol%, based on all repeating units of the copolymer. Is more preferable, and it is especially preferable that it is 1-35 mol%. When the content is less than 0.1 mol%, the solubility in an alkali developer is lowered, and there is a possibility that development cannot be performed. On the other hand, if it exceeds 50 mol%, the solubility in an alkali developer becomes extremely high, and a part of the formed upper layer film may be eluted in the solvent for immersion exposure. May cause problems such as contamination.

  The weight average molecular weight of the copolymer is preferably 2,000 to 100,000, more preferably 3,000 to 80,000, and particularly preferably 4,000 to 7,000. When the weight average molecular weight is less than 2,000, when the upper layer film is formed, the water resistance and mechanical properties of the formed upper layer film may be remarkably lowered. On the other hand, if it exceeds 100,000, the solubility in an alkali developer may be remarkably deteriorated. In the present specification, “weight average molecular weight” is a value in terms of polystyrene measured by gel permeation chromatography (GPC).

  The value of the molecular weight distribution of the copolymer is preferably 1.1 to 2.5, more preferably 1.2 to 2.3, and particularly preferably 1.3 to 2.3. . It is difficult for the present technology to make the value of the molecular weight distribution less than 1.1. On the other hand, if it exceeds 2.5, there is a possibility that a watermark defect is likely to occur. In addition, the presence of unreacted monomer component, oligomer component, ultra-high molecular weight polymer, etc. broadens the molecular weight distribution (the molecular weight distribution value increases), so the molecular weight distribution is narrow (the molecular weight distribution value is close to 1). However, as described above, it is technically difficult to make it smaller than 1.1 in a normal radical polymerization reaction.

Here, the value of the molecular weight distribution is a value calculated by weight average molecular weight (Mw) / number average molecular weight (Mn). In the present specification, the “number average molecular weight” is a value measured using polystyrene as a standard substance by gel permeation chromatography. The polymer for a liquid immersion upper layer film used in the method for producing the composition for forming a liquid immersion upper layer film of the present invention comprises at least a monomer having an acidic functional group and a monomer having a fluorine-containing group in its side chain. Preferably it is. And this polymer for immersion upper layer film is, for example, a mixture of monomers that form each repeating unit using a radical polymerization initiator in an appropriate solvent in the presence of a chain transfer agent if necessary. Can be produced by polymerization.

  The reaction temperature in the above polymerization is usually 40 to 120 ° C., preferably 50 to 100 ° C., and the reaction time is usually 1 to 48 hours, preferably 1 to 24 hours.

  The manufacturing method of the composition for forming an immersion upper layer film of the present invention includes a purification step for removing impurities such as halogen and purification, and a drying step for drying the polymer solution to obtain a dried polymer. Can do.

  Specific examples of the purification step include chemical purification methods such as washing with water and liquid-liquid extraction, and combinations of these chemical purification methods with physical purification methods such as ultrafiltration and centrifugation. it can. By performing the purification step, the content of impurities such as halogen can be reduced. By reducing the impurities, the coatability and the uniform solubility in an alkali developer can be improved.

[3. Immersion upper layer film forming composition]
[3-1. solvent]
The solvent that constitutes the liquid immersion upper layer film-forming composition dissolves the polymer for the liquid immersion upper layer film and, when applied onto the photoresist film, causes intermixing with the photoresist film to improve the lithography performance. A solvent that does not deteriorate can be used.

  Examples of such a solvent include a solvent containing a monohydric alcohol. For example, methanol, ethanol, 1-propanol, isopropanol, n-propanol, n-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, n-hexanol, cyclohexanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2- Methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pen Tanol, 2,2-dimethyl-3-pentanol, 2,3-dimethyl-3-pentanol, 2,4-di Tyl-3-pentanol, 4,4-dimethyl-2-pentanol, 3-ethyl-3-pentanol, 1-heptanol, 2-heptanol, 3-heptanol, 2-methyl-2-hexanol, 2-methyl -3-hexanol, 5-methyl-1-hexanol, 5-methyl-2-hexanol, 2-ethyl-1-hexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, 1-octanol, 2 -Octanol, 3-octanol, 2-propyl-1-pentanol, 2,4,4-trimethyl-1-pentanol, 2,6-dimethyl-4-heptanol, 3-ethyl-2,2-dimethyl-pen Tanol, 1-nonanol, 2-nonanol, 3,5,5-trimethyl-1-hexanol, 1-decanol, 2-decano , 4-decanol, 3,7-dimethyl-1-octanol, 3,7-dimethyl-3-octanol and the like.

  Of these monohydric alcohols, monohydric alcohols having 4 to 8 carbon atoms are preferred, and n-butanol, 2-butanol, and 4-methyl-2-pentanol are more preferred.

  In addition, when the upper layer film is applied on the photoresist film, another solvent can be mixed for the purpose of adjusting the coating property. Other solvents have the effect of uniformly coating the upper layer film without eroding the photoresist film.

  Other solvents include polyhydric alcohols such as ethylene glycol and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether Alkyl ethers of polyhydric alcohols such as diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol ethyl ether acetate, diethylene glycol ethyl Alkyl ether acetates of polyhydric alcohols such as ether acetate, propylene glycol ethyl ether acetate and propylene glycol monomethyl ether acetate; aromatic hydrocarbons such as toluene and xylene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy- Ketones such as 4-methyl-2-pentanone and diacetone alcohol; ethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate , Ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3- Kishipuropion acid ethyl esters such as methyl 3-ethoxypropionate, and water. Among these, cyclic ethers, polyhydric alcohol alkyl ethers, polyhydric alcohol alkyl ether acetates, ketones, esters, and water are preferable.

  The blending ratio of the other solvent is 30% by mass or less, preferably 20% by mass or less in the solvent component. If it exceeds 30% by mass, the photoresist film is eroded, causing problems such as intermixing with the upper film, and the resolution performance of the photoresist is significantly deteriorated.

[3-2. Other ingredients]
In the composition for forming a liquid immersion upper layer film, a surfactant may be blended for the purpose of improving applicability, antifoaming property, leveling property and the like.

  Examples of the surfactant include BM-1000, BM-1100 (manufactured by BM Chemie), MegaFuck F142D, F172, F173, F183 (manufactured by Dainippon Ink & Chemicals, Inc.), Florard FC- 135, FC-170C, FC-430, FC-431 (supplied by Sumitomo 3M), Surflon S-112, S-113, S-131, S-141, S-145 ( Fluorosurfactants marketed under trade names such as Asahi Glass Co., Ltd., SH-28PA, -190, -193, SZ-6032, SF-8428 (above, Toray Dow Corning Silicone). Can be used.

  The blending amount of these surfactants is preferably 5 parts by mass or less with respect to 100 parts by mass of the alkali-soluble resin.

[4. Photoresist pattern forming method]
The composition for forming a liquid immersion upper film obtained by the method for producing a composition for forming a liquid immersion upper film of the present invention is used as a material for forming an upper film for liquid immersion exposure. The upper layer film for immersion exposure is used in the manufacture of semiconductor elements and the like, and is disposed on the photoresist film on which the photoresist pattern is formed, and is used for protecting the photoresist film from the immersion medium. It is a membrane.

  The method for forming a photoresist pattern using the above-mentioned composition for forming an immersion upper layer film is not particularly limited, and a conventionally known method can be adopted, but the above copolymer is contained. In order to maximize the effects of the composition for forming an upper layer film, it is preferable to employ the following method.

  As a method for forming a photoresist pattern for maximizing the effect of the composition for forming a liquid immersion upper layer film described above, (1) a step of forming a photoresist film by applying a photoresist composition on a substrate (Hereinafter, it may be referred to as “Step (1).”) And (2) The liquid immersion upper layer film-forming composition obtained by the production method of the present invention is applied onto the surface of the photoresist film. A step of forming an upper layer film (hereinafter sometimes referred to as “step (2)”), and (3) an immersion medium is disposed between the upper layer film and the lens of the projection exposure apparatus, A process of forming a photoresist pattern on the photoresist film by irradiating the upper layer film and the photoresist film with exposure light through an immersion medium and a mask having a predetermined pattern, followed by development (hereinafter referred to as “process (3)”. ) " . A), a method with is preferred.

  According to such a method, an upper film having sufficient transparency for a short exposure wavelength, particularly 248 nm (KrF) and 193 nm (ArF) and hardly causing intermixing with the photoresist film is formed on the photoresist film. In addition, it is possible to form a high-resolution resist pattern because it is difficult to dissolve in an immersion medium such as water and a stable film can be maintained during immersion exposure.

[4-1. Step (1)]
First, step (1) is a step of forming a photoresist film by applying a photoresist composition on a substrate. As the substrate, a silicon wafer, a silicon wafer coated with aluminum, or the like is usually used. In order to maximize the characteristics of the photoresist film, an organic or inorganic antireflection film may be formed on the surface of the substrate in advance (for example, see Japanese Patent Publication No. 6-12458). .

  Conventionally known photoresist compositions can be appropriately selected as the photoresist composition. For example, it is preferable to use a chemically amplified resist material containing an acid generator, particularly a positive resist material.

  Examples of the chemically amplified positive resist material include a radiation sensitive resin composition containing an acid dissociable group-modified alkali-soluble resin and a radiation sensitive acid generator as essential components. In such a resin composition, an acid is generated from an acid generator upon irradiation (that is, exposure), and the acid dissociation in which the acid group (for example, carboxyl group) of the resin is protected by the action of the generated acid. The acidic group is dissociated and the acidic group is exposed. When the acidic group is exposed, the alkali solubility of the exposed portion of the resist is increased. When the exposed portion is dissolved and removed by an alkali developer, a positive resist pattern can be obtained.

  In the case where the photoresist composition contains a resin containing an acid dissociable group and an acid generator, the resin contains a repeating unit containing an acid dissociable group, and this repeating unit is the total amount of the resin. It is preferable that 40-60 mol% is contained with respect to a repeating unit. If this repeating unit is less than 40 mol%, the resolution as a resist may deteriorate. On the other hand, if this repeating unit is more than 60 mol%, the resist film thickness after peeling off the upper layer film may be extremely reduced.

  Examples of the resin include a repeating unit (M-1) represented by the following general formula (M-1), a repeating unit (M-2) represented by the following general formula (M-2), and the following general formula. Resin containing a repeating unit (M-3) represented by (M-3), a repeating unit (M-1) represented by the following general formula (M-1), and the following general formula (M-2) Resin containing the repeating unit (M-2) represented by the following, and the repeating unit (M-4) represented by the following general formula (M-4), The repeating unit represented by the following general formula (M-1) A resin containing (M-1), a repeating unit (M-3) represented by the following general formula (M-3), and a repeating unit (M-5) represented by the following general formula (M-5) Etc.

  The acid generator generates an acid from the acid generator by irradiation (exposure), and the acid-dissociable group protecting the acidic group (for example, carboxyl group) of the resin is dissociated by the action of the generated acid. Thus, acidic groups are exposed.

Examples of such an acid generator include triphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyl diphenylsulfonium nonafluoro-n-butanesulfonate, and 1- (4-n-butoxynaphthalen-1-yl). ) Tetrahydrothiophenium nonafluoro-n-butanesulfonate, triphenylsulfonium 2- (bicyclo [2.2.1] hepta-2'-yl) -1,1,2,2-tetrafluoroethanesulfonate, 1- (4-n-Butoxynaphthyl) tetrahydrothiophenium 2- (bicyclo [2.2.1] hepta-2'-yl) -1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 2- ( Bicyclo [2.2.1] hepta-2'-yl) -1,1-diflu B ethanesulfonate and the like. In addition, these acid generators may be used individually by 1 type, and may be used in combination of 2 or more type.

  After adding a solvent, the photoresist composition is adjusted so that the total solid content concentration is 0.2 to 20% by mass and filtered with a filter having a pore diameter of about 30 nm to obtain a coating solution. . This coating solution may be prepared by itself, or a commercially available resist solution may be used as the coating solution.

  The photoresist film can be formed by applying a coating solution on a substrate using a conventionally known coating method such as spin coating, cast coating, roll coating or the like. Note that when the photoresist film is formed, preliminary baking (hereinafter also referred to as “PB”) may be performed in order to volatilize the solvent.

[4-2. Step (2)]
Next, in the step (2), the upper film is formed by applying the immersion film forming composition obtained by the production method of the present invention on the surface of the photoresist film formed in the step (1). It is a process to do. By forming the upper layer film in this way, it is possible to prevent the immersion medium from coming into direct contact with the photoresist film during the immersion exposure. Therefore, it is possible to effectively prevent a situation in which the lithography performance of the photoresist film is deteriorated due to the penetration of the immersion medium or the lens of the projection exposure apparatus is contaminated by a component eluted from the photoresist film. Can do.

  The thickness of the upper layer film should be as close as possible to an odd multiple of λ / 4m (where λ is the wavelength of radiation and m is the refractive index of the protective film) because the reflection suppressing effect at the upper interface of the photoresist film is increased. Is preferred.

[4-3. Step (3)]
Next, in step (3), an immersion medium is disposed between the upper layer film formed in step (2) and the lens of the projection exposure apparatus, and the upper layer is interposed via the immersion medium and a mask having a predetermined pattern. This is a step of forming a photoresist pattern on the photoresist film by irradiating the film and the photoresist film with exposure light and then developing.

  As the immersion medium, a liquid having a higher refractive index than air is usually used. Specifically, water is preferably used, and pure water is more preferably used. Note that the pH of the immersion medium may be adjusted as necessary.

  In immersion exposure, radiation is passed through a mask having a predetermined pattern in a state where the immersion medium is interposed (that is, in a state where the immersion medium is filled between the lens of the exposure apparatus and the photoresist film). To expose the photoresist film.

  The radiation that can be used in the immersion exposure may be appropriately selected according to the type of the photoresist film and the upper layer film used, and examples thereof include visible light; ultraviolet light such as g-line and i-line; excimer laser. Various radiations such as deep ultraviolet rays such as X-rays, X-rays such as synchrotron radiation, and charged particle beams such as electron beams can be used. Among these, it is preferable to use an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm). What is necessary is just to set exposure conditions, such as a radiation dose, suitably according to the compounding composition of a photoresist composition, the kind of additive, etc.

  In order to improve the resolution, pattern shape, developability, and the like of the photoresist film, baking (PEB) is preferably performed after exposure. The firing temperature is appropriately adjusted depending on the type of the radiation-sensitive resin composition used, and is usually 30 to 200 ° C, preferably 50 to 150 ° C.

  Then, after development or after PEB, development is performed, and if necessary, a desired photoresist pattern can be formed.

  Examples of the developer include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, dimethylethanol. Amines, triethanolamine; tetraalkylammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7-undecene, 1 It is preferable to use an alkaline aqueous solution in which at least one alkaline compound such as 1,5-diazabicyclo- [4.3.0] -5-nonane is dissolved. Among these, an aqueous solution of tetraalkylammonium hydroxides is preferable.

  For example, an appropriate amount of a water-soluble organic solvent including alcohols such as methanol and ethanol, and a surfactant can be added to the developer. In addition, when developing using alkaline aqueous solution, it wash | cleans with water after image development normally. Moreover, if it dries suitably after image development or the water washing as needed, the target photoresist pattern can be formed.

  Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to this embodiment. In the description of Examples, “part” and “%” are based on mass unless otherwise specified.

[Example 1]
The repeating unit having a fluorine-containing group represented by the general formula (1) in the side chain is represented by [methacrylic acid (1,1,1- 1) as the monomer (A) represented by the following formula (1). Trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl) ester] a monomer (A) solution in which 46.95 g (85 mol%) is dissolved in 85 g of isopropanol, and a radical initiator (2,2 An initiator solution in which 6.91 g of '-azobis- (methyl methyl 2-methylpropionate)) was dissolved in 15 g of isopropanol was prepared.

  Meanwhile, 50 g of isopropanol was charged 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.

  And the monomer (A) solution and initiator solution which were prepared beforehand were dripped over 2 hours using the dropping funnel. After completion of the dropwise addition, the reaction was further continued for 1 hour.

  Subsequently, 10 g of an isopropanol solution of 3.05 g (15 mol%) of [vinyl sulfonic acid] was added dropwise over 30 minutes as the monomer (B) having the acidic functional group described above. Thereafter, the reaction was further performed for 1 hour, and then cooled to 30 ° C. or lower to obtain a copolymer solution.

  Subsequently, after concentrating the obtained copolymer 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 added to the separatory funnel, separation and purification were performed, and the lower layer liquid was recovered after separation. The recovered lower layer solution was replaced with 4-methyl-2-pentanol, and the total amount was adjusted to 250 g. After the adjustment, 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 resin solution.

  The solid concentration of the sample (resin solution) after the substitution with 4-methyl-2-pentanol was measured by weighing 0.3 g of the resin solution in an aluminum dish and heating on a hot plate at 140 ° C. for 1 hour. Then, it was calculated from the mass of the resin solution before heating and the mass of the residue (after heating). This solid content concentration was used for the preparation of the upper layer film-forming composition solution and the yield calculation.

Mw of the copolymer contained in the obtained resin solution was 9760, Mw / Mn was 1.51, and the yield was 65%. When this resin solution was passed through an ion exchange resin filter (Nippon Pole Co., Ltd .: Ion Clean SL) 30 L / hrm ² and the amount of contained metal was measured by ICP-MS, Na: 24 ppb, Fe: 15 ppb, Ni : 20 ppb.

[Example 2]
The repeating unit having a fluorine-containing group represented by the general formula (1) in the side chain is represented by [methacrylic acid (1,1,1- 1) as the monomer (A) represented by the following formula (1). Trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl) ester] a monomer (A) solution in which 46.95 g (85 mol%) is dissolved in 85 g of isopropanol, and a radical initiator (2,2 An initiator solution in which 6.91 g of '-azobis- (methyl methyl 2-methylpropionate)) was dissolved in 15 g of isopropanol was prepared. Further, 10 g of an isopropanol solution (C) of 3.05 g (15 mol%) of [vinyl sulfonic acid] for addition was prepared.

  The monomer (B) solution and the vinyl sulfonic acid isopropanol solution (C) were each passed through the same ion exchange resin filter as in Example 1.

  Using these, the liquid immersion upper layer film composition was polymerized in the same manner as in Example 1. Mw of the copolymer contained in the obtained resin solution was 9770, Mw / Mn was 1.5, and the yield was 64%. The obtained resin solution was measured for the amount of metal contained by ICP-MS. As a result, Na: 45 ppb, Fe: 43 ppb, and Ni: 27 ppb were obtained.

[Comparative Example 1]
A liquid immersion upper layer film composition was synthesized in the same manner as in Example 1 except that the resin solution was not passed through an ion exchange resin filter, and the amount of contained metal was measured.
Na: 520 ppb, Fe: 288 ppb, Ni: 380 ppb.

  The composition for forming an immersion upper layer film obtained by the production method of the present invention can be used for immersion lithography in semiconductor production.

Claims (8)

  A composition for forming a liquid immersion upper film comprising a step of contacting a monomer of a polymer for liquid immersion upper film or a polymer solution obtained by polymerizing the monomer with an ion exchange resin having a cation exchange group Production method.   The method for producing a composition for forming a liquid immersion upper layer film according to claim 1, wherein the ion exchange resin is an ion exchange membrane.   The manufacturing method of the composition for liquid immersion upper film | membrane formation of Claim 2 in which the said ion exchange membrane has a cation exchange group in any one substrate of polyolefin, a polysaccharide, and a fluorine-type polymer.   The method for producing a composition for forming a liquid immersion upper layer film according to claim 3, wherein the substrate of the ion exchange membrane is polyolefin. The monomer of the polymer for liquid immersion upper layer film or the polymerization solution obtained by polymerizing the monomer is brought into contact with an ion exchange resin having a cation exchange group at 10 to 200 L / hrm ² . The manufacturing method of the composition for liquid immersion upper film formation as described in any one of Claims.   The production of the composition for forming a liquid immersion upper film according to any one of claims 1 to 5, comprising a step of bringing the monomer of the polymer for liquid immersion upper film into contact with an ion exchange resin having a cation exchange group. Method.   The liquid as described in any one of Claims 1-6 including the process which the polymerization solution obtained by superposing | polymerizing the monomer of the polymer for liquid immersion upper film | membranes is made to contact the ion exchange resin which has a cation exchange group. A method for producing a composition for forming a submerged layer film.   A composition for forming a liquid immersion upper layer film, wherein the Na content is 50 ppb or less, the Fe content is 50 ppb or less, and the Ni content is 50 ppb or less.