Method for producing a coating composition and method for producing a photoresist laminate

Abstract

A method for producing a coating composition, which comprises filtering a solution to be treated containing a fluorinated polymer having units represented by the following formula (1) and a solvent, the solution to be treated not containing water, with a filter having a fluorine atom content of at most 70% by mass, so that a coating composition is obtained: -[CX 1 X 2 -Cy 1 (Rf 1 -COOM 1 )]- (1) where X 1 and X 2 are each independently a hydrogen atom, a fluorine atom or a chlorine atom, Y 1 a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a trifluoromethyl group, Rf 1a straight or branched perfluoroalkylene group which may contain an ether oxygen atom between carbon-carbon atoms, or a straight or branched oxyperfluoroalkylene group which may contain an ether oxygen atom between carbon-carbon atoms, wherein the number of carbon atoms in Rf 1 from 1 to 10 in the case where Rf 1 does not contain an ether oxygen atom, and from 2 to 10 in the case where it contains an ether oxygen atom, and -COOM 1 -COOH or -COOZ 1 is (where Z 1 an ammonium ion in which the hydrogen atom may be substituted).

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for producing a coating composition. More particularly, it relates to a method for producing a coating composition suitable for forming an anti-reflection coating layer on a photoresist layer. Furthermore, it relates to a method for producing a photoresist laminate having an anti-reflection coating layer on its surface. STATE OF THE ART

[0002] Photolithography techniques are used in processes for manufacturing semiconductors, etc., and for example, a process for manufacturing semiconductor circuits includes steps of forming patterns or structures from a photoresist (photoresist pattern).

[0003] When the photoresist layer formed on a substrate is irradiated with exposure light, in addition to the light incident on the photoresist layer, the light reflected from the substrate surface interferes with the light generated from the reflected light being re-reflected from the surface of the photoresist layer. As a result, standing waves are generated. Such standing waves can cause dimensional changes and collapse of the shape of the photoresist pattern, among other things.

[0004] Furthermore, there may be cases where fine photoresist patterns are to be formed on the surface with height differences. In such a case, dimensional changes and shape collapse due to standing waves (standing wave effect) tend to be large.

[0005] Hitherto, as methods for suppressing the standing wave effect, a method of incorporating a light absorber into the photoresist material, a method of providing an anti-reflection coating layer on the upper surface of the photoresist layer (TARC method), a method of providing an anti-reflection coating layer on the lower surface of the photoresist layer (BARC method), etc., have been proposed.

[0006] The TARC method and the BARC method are methods of providing an anti-reflection coating layer adjacent to a photoresist layer, wherein the anti-reflection coating layer has a lower refractive index than the photoresist layer, wherein the lower the refractive index of the anti-reflection coating layer, the higher the anti-reflection effect obtainable.

[0007] Patent Document 1 discloses, as a coating composition to be used for the TARC method, a composition comprising a polymer dissolved in a solvent consisting of water and methanol, the polymer obtained by polymerizing CF2=CFOCF2CF2CF2COOCH3 to obtain a polymer precursor having a straight-chain oxyperfluoroalkylene group as its side chains, and converting a methyl ester group at the side chain end of the polymer precursor to -COOH.

[0008] In the TARC method, it is generally known that in order to obtain an excellent anti-reflection effect, the ideal refractive index of the anti-reflection coating layer is the square root (√n) of the refractive index n of the photoresist layer, and the ideal coating layer thickness is an odd multiple of λ / 4m (λ is the wavelength of radial rays and m is the refractive index of the anti-reflection coating layer) (e.g., Patent Document 2, paragraph

[0004] ). PRIOR ART DOCUMENTS PATENT DOCUMENTS Patent document 1: JP 3 965 740 B2 Patent document 2: JP 4 910 829 B2 Patent document 3: US 2010 / 0 286 318 A1 DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM

[0009] In recent years, along with higher integration and operating speed in LSIs, the miniaturization of semiconductor circuits has become increasingly necessary. To meet this demand, efforts have been made to shorten the wavelength of the exposure light source used in the formation of photoresist patterns.

[0010] For example, in mass production processes for a 64 Mbit DRAM (dynamic random access memory), a KrF excimer laser (248 nm) was used as the exposure light source, but a shorter wavelength ArF excimer laser (193 nm) or F2 laser (157 nm) is used to manufacture a 256 Mbit and more than 1 Gbit DRAM.

[0011] With the downsizing of semiconductor circuits, as described above, small defects that are negligible at conventional line widths have significant impacts on semiconductor circuits. Accordingly, a high antireflection effect sufficient to suppress such small defects is required for TARC, and a technique for highly precise adjustment of the thickness of the antireflection coating layer is becoming increasingly important.

[0012] As a method for adjusting the thickness of the anti-reflection coating layer, for example, to make the layer thin, a method of reducing the concentration of film-forming substances in the coating liquid is effective and simple. On the other hand, a method of increasing the concentration of film-forming substances is the simplest for making the layer thick, but the high viscosity of the coating liquid will increase the load on the apparatus, resulting in an increase in the number of steps and consequently a considerable increase in cost. Accordingly, a method of adding thickeners to increase the viscosity is considered, but the addition of thickeners increases the refractive index of the anti-reflection coating layer.

[0013] It is an object of the present invention to provide a method for producing a coating composition which can increase the coating layer thickness without increasing the concentration of film-forming substances and without using an additive such as thickeners, and a method for producing a photoresist laminate using the same. SOLUTION TO THE PROBLEM

[0014] The present invention provides a process for preparing a coating composition and a process for using the same, as well as a process for preparing a photoresist laminate, having the structure as defined in the appended claims. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0015] According to the method for producing a coating composition of the present invention, a coating composition can be obtained which can increase the coating layer thickness without increasing the concentration of film-forming substances and without using additives such as thickeners.

[0016] According to the method for producing a photoresist laminate of the present invention, the thickness of an anti-reflection coating layer formed on the surface of a photoresist layer can be increased without increasing the concentration of film-forming substances in the coating liquid and without using additives such as thickeners. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the results of examples and comparison examples. DESCRIPTION OF EMBODIMENTS [Method for producing a coating composition]

[0017] In the process for producing a coating composition of the present invention, a solution to be treated containing a fluorinated polymer having units represented by the above formula (1) (hereinafter sometimes referred to as "units (1)" (hereinafter sometimes referred to as "fluorinated polymer (A)") and a solvent is filtered, and the obtained filtrate is used for the coating composition.

[0018] The coating composition may contain a polymer other than the fluorinated polymer (A) (hereinafter sometimes referred to as "other polymer") within a range that does not impair the effects of the present invention. The fluorinated polymer and the other polymer may sometimes be generally referred to as "polymer." When the other polymer is included in the coating composition, it may be added before filtration or it may be added after filtration. From the viewpoint of improving the stability of the composition, the other polymer is preferably added before filtration.

[0019] The coating composition may optionally contain components other than the polymer (hereinafter sometimes referred to as "other components"). When other components are included in the coating composition, they may be added before filtration or after filtration. In order to improve the stability of the composition, the other components are preferably added before filtration.

[0020] In the unit (1) X 1 and X 2 each independently represents a hydrogen atom, a fluorine atom, or a chlorine atom. In view of the availability of the starting material, they are preferably a hydrogen atom or a fluorine atom. X 1 and X 2are preferably a fluorine atom in view of the fact that when the fluorinated polymer (A) has a sufficiently high fluorine atom content, the anti-reflection coating layer formed by the use of such a fluorinated polymer (A) tends to have a low refractive index in the short wavelength region.

[0021] Y 1 is a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, or a trifluoromethyl group. In view of the availability of the starting material, it is preferably a fluorine atom.

[0022] RF 1 is a straight-chain or branched-chain perfluoroalkylene group or a straight-chain or branched-chain oxyperfluoroalkylene group. Such a perfluoroalkylene group or oxyperfluoroalkylene group may contain an ether oxygen atom between carbon-carbon atoms.

[0023] The perfluoroalkylene group represents an alkylene group in which all hydrogen atoms bonded to carbon atoms of the group are substituted by fluorine atoms.

[0024] The oxyperfluoroalkylene group means that a perfluoroalkylene group is bonded to the carbon atom which is attached to Y by means of an ether bond (-O-). 1 in formula (1).

[0025] The term “containing an ether oxygen atom between carbon-carbon atoms” means that an oxygen atom of an ether bond is inserted into a carbon chain (between carbon-carbon atoms) forming the perfluoroalkylene group or the oxyperfluoroalkylene group.

[0026] The number of carbon atoms in Rf 1 is in the case that Rf 1has no ether oxygen atom between carbon-carbon atoms, from 1 to 10, preferably from 1 to 6, particularly preferably from 3 to 6. The number of carbon atoms in Rf 1 is in the case that Rf 1 having an ether oxygen atom between carbon-carbon atoms, from 2 to 10, preferably from 2 to 6, particularly preferably from 3 to 6. When the number of carbon atoms is at least the lower limit of the above-mentioned range, the fluorine atom content in the fluorinated polymer (A) tends to be sufficiently high, and the refractive index in the short wavelength region of the antireflection coating layer prepared using the fluorinated polymer (A) tends to be low. When it is at most the upper limit of the above-mentioned range, the fluorinated polymer (A) has excellent solubility in water.

[0027] In the unit (1) -COOM1 -COOH or COOZ 1 (where Z 1 an ammonium ion in which the hydrogen atom may be substituted).

[0028] Z 1 is NH4 + or a group in which at least one hydrogen atom is NH4 + is substituted by an alkyl group or an alkyl group containing a hydroxy group. The alkyl group is preferably a C 1-6 -alkyl group. Z 1 is preferably -NR 1 R 2 R 3 R 4+ (where R 1 to R 4 each independently represents a hydrogen atom or a C 1-3 -alkyl group), and in view of availability and low cost, NH4 is particularly preferred + .

[0029] As preferred examples of the unit (1), the following units (a1) to (a6) can be mentioned.

[0030] The fluorinated polymer (A) may have units that do not contain -COOM 1(hereinafter sometimes referred to as ‘units (2)’).

[0031] For example, the unit (2) may be a unit based on a fluoroethylene such as CF2=CF2, CH2=CF2 or CF2=CFCl, a perfluorovinyl ether or a polymerizable perfluoro compound such as a perfluoroolefin having 3 or more carbon atoms.

[0032] The content of the units (1) in the fluorinated polymer (A) is preferably at least 50 mol%, more preferably at least 70 mol%, particularly preferably 100 mol%, based on all the units constituting the fluorinated polymer (A). When the content of the units (1) is at least the lower limit of the above-mentioned range, the fluorinated polymer (A) has excellent solubility in an alkaline aqueous solution.

[0033] The number average molecular weight of the fluorinated polymer (A) is preferably from 1000 to 30000, more preferably from 1500 to 5000, particularly preferably from 2500 to 3500.

[0034] When the number-average molecular weight is at least the above-mentioned lower limit, the fluorinated polymer (A) will exhibit excellent coating layer-forming properties and excellent coating layer thickness uniformity on the flat surface. When it is at most the above-mentioned upper limit, the fluorinated polymer (A) will exhibit excellent flowability with respect to the height difference in the application process, and the coating amount required to cover the entire surface of the convexities and concavities can be small in the case where the photoresist layer has irregularities on its surface. Furthermore, the fluorinated polymer (A) will exhibit excellent solubility in an alkaline aqueous solution.

[0035] The process for producing the fluorinated polymer (A) in which -COOM 1-COOH is not particularly limited, and it is preferably the following method (1) or (2).

[0036] Process (1): A process in which a monomer having a precursor functional group that can be converted to “-COOH” is polymerized to obtain a polymer precursor, and next, the precursor functional group is converted to “-COOH”.

[0037] Process (2): A process in which a fluorinated monomer having no precursor functional group is polymerized, and next, “-COOH” is introduced into a part of the resulting polymer.

[0038] The method (1) may be a method for polymerizing a fluorinated monomer obtained by CX 1 X 2 =CY 1 (Rf 1 -COOCH3) (where X 1 , X 2 , Y 1 and Rf 1are as defined for the formula (1)) (hereinafter sometimes referred to as “fluorinated monomer (1)”) to obtain a polymer precursor, and hydrolyzing the -COOCH3- residue.

[0039] The method for hydrolyzing the -COOCH3- residue in the polymer precursor to obtain the fluorinated polymer (A) is not specifically limited. For example, the polymer precursor is stirred together with water or a water-containing medium. Stirring is preferably carried out with heating. The temperature of the water or the medium is preferably from 50 to 150°C.

[0040] The above-mentioned medium is preferably a mixed solvent consisting of water and a hydrophilic organic solvent. In view of excellent miscibility with water, the hydrophilic organic solvent is preferably an alcohol. In view of excellent solubility of the polymer precursor, a fluorinated alcohol is particularly preferred. The fluorinated alcohol is preferably a compound having a fluorine atom content of at least 50 wt%, for example, 2-(perfluorobutyl)ethanol, 2-(perfluorohexyl)ethanol, hexafluoroisopropanol, or 2,2,3,3-tetrafluoropropanol. The mass ratio of water to the hydrophilic organic solvent in the mixed solvent is preferably from 3:7 to 9:1, more preferably from 4:6 to 6:4. Within the above-mentioned range, the polymer precursor has very good solubility in the solvent.

[0041] For example, the method (2) may be a method for polymerizing a fluorinated monomer obtained by CX 1 X 2 =CY 1 (Rf 1 -CCl3) and adding sulfuric acid and water to convert -CCl3 to COOH.

[0042] As a process for producing the fluorinated polymer (A) wherein -COOM 1 -COOZ 1 is, there can be mentioned a method in which a polymer having -COOH is obtained by the method (1) or (2), and then ammonia or an organic amine is added to convert -COOH into -COOZ 1 to convert.

[0043] For example, the organic amine may be a monoalkylamine such as ethylamine or propylamine; a dialkylamine such as diethylamine; a trialkylamine such as triethylamine; or an alkanolamine such as ethanolamine or diethanolamine. They may be used alone or in a combination of two or more.

[0044] Another polymer may be polyacrylic acid. The number-average molecular weight of the other polymer is preferably from 1,000 to 30,000, more preferably from 1,500 to 5,000, and particularly preferably from 2,500 to 3,500.

[0045] In the present invention, the total content of the fluorinated polymer (A) and the other polymer is referred to as the polymer content. Regarding the polymer content, the content of the fluorinated polymer (A) is preferably at least 50 mass%, more preferably at least 70 mass%, particularly preferably 100 mass%.

[0046] As other components, a surfactant or additives other than a surfactant may be included within a range that does not impair the effects of the present invention.

[0047] The surfactant contributes to improving the wettability in the application process and the uniformity of the formed coating layer.

[0048] For example, the surfactant may be an amine salt of a fluorinated organic acid. Specifically, it may be a compound containing a polyfluoroalkyl group and a polyoxyethylene group (trade name: Fluorad "FC-430", "FC-4430", etc., manufactured by 3M), acetylene glycol and polyoxyethylene with added acetylene glycol (trade name: "Surfynol 104", "Surfynol 420", manufactured by Air Products and Chemicals Inc.), alkyl sulfonate and alkylbenzenesulfonate (e.g., trade name: Nikkol "SBL-2N-27", etc., manufactured by Nikko Chemicals Co., Ltd.), or a compound containing a hydroxy group and no polyoxyethylene group (such as a polyglycerol fatty acid ester).

[0049] If the surfactant content is too high, the anti-reflection coating layer is likely to whiten, and the surfactant may diffuse into the photoresist layer located beneath the anti-reflection coating layer, causing exposure failure. Furthermore, adding a surfactant other than a perfluoro compound increases the refractive index of the anti-reflection coating layer. Accordingly, the surfactant content is preferably at most 10 mass%, more preferably at most 5 mass%, based on the polymer content.

[0050] As an additive other than the surfactant, additives known for the coating composition for forming an anti-reflection coating layer can be mentioned.

[0051] For example, the additive may specifically be a photoacid generator such as an onium salt, a haloalkyl group-containing compound, an o-quinonediazide compound, a nitrobenzyl compound, a sulfonic acid ester compound, or a sulfone compound.

[0052] The addition of additives other than perfluorocompounds increases the refractive index of the anti-reflection coating layer. Accordingly, the total content of additives other than the surfactant in the coating composition is preferably at most 10% by mass, more preferably at most 5% by mass, based on the polymer content.

[0053] The solution to be treated, which is subjected to filtration with a filter, contains the fluorinated polymer (A) and a solvent. The fluorinated polymer (A) is preferably a polymer prepared by process (1) or (2).

[0054] The solvent in the solution to be treated is preferably a hydrophilic organic solvent. The hydrophilic organic solvent may be an alcohol, such as methanol, ethanol, isopropanol, 2-butanol, or a fluorinated alcohol. For example, the fluorinated alcohol may be the fluorinated alcohol mentioned above for the hydrophilic organic solvent to be used for hydrolysis.

[0055] The solvent in the solution to be treated may be the solvent used for preparing the fluorinated polymer (A), the solvent added after the completion of the preparation of the fluorinated polymer (A), or a mixture thereof, wherein the solution to be treated does not contain water.

[0056] That is, the liquid obtained by producing the fluorinated polymer (A) in the solvent can be subjected to filtration as the solution to be treated. The solvent can be added to the liquid obtained by producing the fluorinated polymer (A) in the solvent to obtain the solution to be treated. The liquid obtained by producing the fluorinated polymer (A) in the solvent is dried, and then the solvent is added to obtain the solution to be treated. Otherwise, the fluorinated polymer (A) can be produced without a solvent, optionally dried, and the solvent is added to obtain the solution to be treated.

[0057] The content of the fluorinated polymer in the solution to be treated is preferably from 1 to 25 mass%, more preferably from 1 to 10 mass%, particularly preferably from 2 to 5 mass%. When the content of the fluorinated polymer is at least the lower limit of the above range, the thickness of the anti-reflection coating layer will be sufficiently large, and when it is at most the upper limit, the viscosity of the solution will be sufficiently low, thereby shortening the filtration time and reducing the likelihood of problems such as clogging.

[0058] In the present invention, the solution to be treated is filtered with a filter having a fluorine atom content of at most 70 mass%. The content of the fluorinated polymer in the filtrate after filtration is largely identical to that before filtration.

[0059] By reducing the fluorine atom content of the filter, the thickness of a coating layer formed using the coating liquid containing the filtrate tends to increase. The fluorine atom content of the filter is preferably at most 70 mass%, more preferably at most 60 mass%. It may be 0%. When the fluorine atom content of the filter is at most 70 mass%, the increase in the thickness of the coating layer by performing filtration becomes sufficiently large. Therefore, the above-mentioned method is effective as a method for adjusting the coating layer thickness.

[0060] For example, the filter material with a fluorine atom content of 70 mass% or less can be an organic material such as polyvinylidene chloride (PVDF), polyamide, or polypropylene (PP), or an inorganic material such as glass. The organic material is preferred in view of the low probability of increasing the concentration of metal impurities in the composition.

[0061] In the case where a filter is made of two or more materials that differ in fluorine atom content, the fluorine atom content of at least one material should be within the above-mentioned range.

[0062] The pore size of the filter is preferably from 0.2 to 5.0 µm, more preferably from 0.2 to 1.0 µm, particularly preferably from 0.2 to 0.5 µm.

[0063] The shape of the filter and the filtration method are not specifically limited. A known filtration device and method can be used. Filtration can be carried out at room temperature.

[0064] For example, the effects of the present invention are achieved by pressure filtration using a capsule filter which is commonly used.

[0065] The filtration speed (linear speed) is not specifically limited and can be, for example, from 0.001 to 1.0 cm / s, preferably from 0.003 to 0.5 cm / s. [Coating liquid]

[0066] The coating liquid in the present invention is obtained by using the coating composition. The coating liquid is a solution to be applied to an object to be coated (such as a photoresist layer).

[0067] As the coating liquid, the coating composition can be used as such, or the coating composition can be mixed with another solvent. The solvent in the coating liquid is identical to the solvent of the solution to be treated, including preferred embodiments.

[0068] Some or all of the other polymer and the other component need not be included in the coating composition and may be added when the coating liquid is prepared.

[0069] Part of the other polymer and component may be incorporated into the coating composition and the rest may be added when the coating liquid is prepared.

[0070] In view of excellent coating properties, the polymer content in the coating liquid is preferably at most 10 mass%, more preferably at most 7 mass%, particularly preferably at most 5 mass%. In view of the likelihood of forming an anti-reflection coating layer with the required thickness, it is preferably at least 1 mass%, more preferably at least 2 mass%, particularly preferably at least 4 mass%.

[0071] The proportion of the content of the fluorinated polymer (A) to the total content of the fluorinated polymer (A) and the other polymer in the coating liquid is preferably at least 50 mass%, more preferably at least 70 mass%, particularly preferably 100 mass%. [Method for producing a photoresist laminate]

[0072] In the present invention, the photoresist laminate is a laminate comprising a photoresist layer and an anti-reflection coating layer formed on the surface of the photoresist layer.

[0073] In the method for producing a photoresist laminate of the present invention, a coating composition is obtained by the production method of the present invention, then a coating liquid containing the coating composition is obtained, and then the coating liquid is applied, so that a photoresist laminate having an anti-reflection coating layer formed on the surface of a photoresist layer is obtained.

[0074] Known methods can be used for applying the coating liquid to the surface of the photoresist layer. A spin coating method is preferred in view of the uniformity of the anti-reflection coating layer and ease of fabrication.

[0075] After the coating liquid has been applied, the solvent is removed as required. As a method for removing the solvent, for example, it is preferable to heat and dry using a hot plate or an oven. For example, when using a hot plate, the drying temperature is preferably 80 to 150°C and the drying time is 5 to 30 minutes.

[0076] The method for producing a photoresist laminate of the present invention is suitable as a method for forming photoresist patterns, which comprises forming a photoresist layer on a substrate, forming an anti-reflection coating layer on the surface of the photoresist layer to obtain a photoresist laminate, exposing the photoresist laminate, and performing development using an aqueous alkaline solution to form photoresist patterns.

[0077] By forming the anti-reflection coating layer using a coating liquid obtained by the manufacturing method of the present invention, the standing wave effect is suppressed, and dimensional change or deformation of the shape of the photoresist pattern can be suppressed. Furthermore, the anti-reflection coating layer has good solubility in the aqueous alkaline solution, and development and removal of the anti-reflection coating layer can be performed simultaneously.

[0078] Furthermore, in the case where the photoresist layer is a layer made of a so-called chemically amplified photoresist that utilizes the catalytic action of protons generated by exposure, the surface of the photoresist layer is likely to deteriorate if the photoresist layer is left in the atmospheric air after exposure. When such a photoresist layer has on its surface the anti-reflection coating layer obtained by the manufacturing method of the present invention, the anti-reflection coating layer also functions as a protective layer, and deterioration of the surface of the photoresist layer can be prevented. [Function and mechanism]

[0079] According to the present invention, as shown in the examples described below, the anti-reflection coating layer can be made thick with a coating composition obtained by filtering a solution to be treated with a filter having a fluorine atom content of at most 70 mass%, compared with the case where the solution to be treated which has not been filtered is used as such as the coating composition, even at the same level of the polymer content.

[0080] The reason why such effects are obtained is not clear, but as a result of detailed studies by the present inventors regarding the change in composition before and after filtration, the following was obtained. That is, it was found that when the fluorine atom content of the filter is at most 70 mass%, the content of the compound having a peak near -119 (minus 119) ppm (hereinafter sometimes referred to as the "-119 ppm compound") based on trifluorochloromethane in a 19 F-NMR spectrum decreases significantly during the filtration process. It is assumed that the reduction in the content of this compound contributes to an increase in the coating layer thickness. Furthermore, it is assumed that the compound is likely to be adsorbed in the filter with a fluorine atom content of 70 mass% or less.

[0081] In particular, the content of the -119 ppm compound in the coating liquid is preferably less than 0.95 mass%. EXAMPLES

[0082] Below, the present invention will be described in more detail with reference to examples. However, it should be noted that the present invention is by no means limited to such specific examples.

[0083] The following methods were used as measurement and evaluation methods. [Number average molecular weight]

[0084] The number average molecular weight value of the polymer is the molecular weight calculated based on the molecular weight of polystyrene (PS) and measured by gel permeation chromatography (GPC). [Polymer content]

[0085] 2 mL of the coating composition was placed in a 20 mL vial and vacuum dried at 80 °C for 3 hours. The masses before and after drying of the vial were measured to calculate the polymer content (unit: mass%) in the solution. [Coating thickness and refractive index]

[0086] The coating liquid was applied to a silicon wafer by spin coating (3000 rpm, 180 seconds) and dried for 5 minutes on a hot plate set at 150 °C to form a coating layer (anti-reflection coating layer). The coating layer thickness and the refractive index at 193 nm were measured using an ellipsometer. The amount of coating liquid used remained constant at 2 mL.

[0087] The thicknesses of the coating layers obtained were compared using a constant amount of coating liquid under constant coating conditions. [Content of the -119 ppm compound]

[0088] The coating composition was mixed with heavy water and 1,1,1,3,3,3-hexafluoro-2-isopropanol (HFIP) so that the polymer content was adjusted to 2 mass%, and then the 19 F-NMR measured.

[0089] From the obtained diagram, using HFIP as a standard substance, the content (unit: mass%) of a compound with a peak near -119 ppm (-119 ppm compound) was calculated on the basis of trifluorochloromethane. [Preparation Example 1: Preparation of a fluorinated polymer (A1) and solution (1)]

[0090] 50 g of CF2=CFOCF2CF2CF2COOCH3 (molecular weight: 306) as a monomer and 0.60 g of a diisopropyl peroxydicarbonate solution (concentration: 50 mass%, solvent: CF3CH2OCF2CF2H) as an initiator solution were charged into a reactor, and the reactor interior was replaced with nitrogen. Next, a polymerization reaction was carried out for 72 hours with stirring and heating, with the internal temperature controlled at 40 °C. After the polymerization reaction, drying was carried out at 80 °C for 3 hours under vacuum to obtain 21.5 g of a polymer precursor. The number-average molecular weight of the polymer precursor was 3300.

[0091] Then, methyl groups at the ends of the side chains in the polymer precursor were hydrolyzed and converted into hydroxy groups. That is, the polymer precursor and water were stirred at 80 °C for 12 hours to conduct hydrolysis, yielding an aqueous solution containing 18 mass% of the fluorinated polymer (A1) (solution (1)) in a separate flask.

[0092] The fluorinated polymer (A1) itself can be obtained by drying the solution (1) at 80 °C for 3 hours under vacuum. [Preparation Example 2: Preparation of the solutions (2) to (4) to be treated and the coating compositions using them]

[0093] Treated solutions (2) to (4) containing the fluorinated polymer (A1) obtained in Preparation Example 1 and different solvents were prepared. The content of the fluorinated polymer in each treated solution was such that a coating layer could be easily formed by a spin-coating method.

[0094] Preparation of the solution to be treated (2): The solution (1) was diluted with water to produce a solution to be treated (2) with a content of the fluorinated polymer (A1) of 5 mass%.

[0095] Preparation of the solution to be treated (3): A sample of the fluorinated polymer (A1) was obtained from the solution (1) and mixed with 2-butanol to prepare a solution to be treated (3) containing 3 mass% of the fluorinated polymer (A1).

[0096] Preparation of the solution to be treated (4): A sample of the fluorinated polymer (A1) was obtained from the solution (1) and mixed with 2,2,3,3-tetrafluoropropanol (TFPO) to prepare a solution to be treated (4) with a content of the fluorinated polymer (A1) of 4 mass%.

[0097] Using the solutions (2) to (4) to be treated, coating compositions (2) to (4) were prepared and used as such as coating liquids (2) to (4).

[0098] Examples 1, 11, and 21 are comparative examples in which no filtration was performed, Examples 2, 12, 17, and 22 are comparative examples in which the fluorine atom content of the filter exceeded 70 mass%, Examples 3 to 5 are reference examples in which the solution to be treated contains water, and Examples 13 to 16 and 23 to 28 are examples of the present invention.

[0099] In the filtration step, the following filters (1) to (5) were used, which differed in the filter material. The fluorine atom contents of the respective filters are shown in Tables 1 to 3. [Filters used] Filter (1): Made of polytetrafluoroethylene, manufactured by Tomsic Ltd., TITAN2-PTFE (trade name). Three types with pore sizes of 1.0 µm, 0.45 µm, and 0.2 µm were produced. Filter (2): Made of polyvinylidene fluoride, manufactured by Tomsic Ltd., TITAN2-PVDF (trade name). Two types with pore sizes of 0.45 µm and 0.2 µm were manufactured. Filter (3): Made of polyamide, manufactured by Tomsic Ltd., TITAN2-NYLON (trade name). Three types with pore sizes of 1.5 µm, 0.45 µm, and 0.2 µm were produced. Filter (4) PP: Made of polypropylene, manufactured by Tomsic Ltd., TITAN2 polypropylene (trade name). Two types with pore sizes of 0.45 µm and 0.2 µm were produced. Filter (5): Made of borosilicate glass, manufactured by Tomsic Ltd., TITAN2-Glass Microfiber (trade name), pore size: 1.0 µm. [Example 1: No filtration]

[0100] The solution to be treated (2) was used as such without filtration as coating liquid (2).

[0101] The polymer content and the content of the -119 ppm compound in the coating liquid (2) were measured. A coating layer was formed by a spin coating method, and the coating layer thickness was measured. The results are shown in Table 1 (the same applies below). [Examples 2 to 5]

[0102] Using each filter as listed in Table 1, the solution to be treated (2) was subjected to syringe filtration at a filtration rate of 0.2 cm / s, and the filtrate was used as the coating liquid (2). The same measurements as in Example 1 were performed. [Example 11: No filtration]

[0103] The solution to be treated (3) was used as such without filtration as coating liquid (3).

[0104] The polymer content and the content of the -119 ppm compound in the coating liquid (3) were measured. A coating layer was formed by a spin coating method, and the coating layer thickness and refractive index were measured. The results are shown in Table 2 (the same applies below). [Example 12 to 16]

[0105] Using each filter as listed in Table 2, the solution to be treated (3) was subjected to syringe filtration at a filtration rate (linear velocity) of 0.2 cm / s, and the filtrate was used as the coating liquid (3). The same measurements as in Example 11 were performed. In the table, "-" indicates that no measurement was performed (the same applies below). [Example 17]

[0106] A liquid with a polyacrylic acid concentration of 0.2 mass%, prepared by adding polyacrylic acid to the solution to be treated (3), was subjected to syringe filtration using a filter specified in Table 2 at a filtration speed (linear velocity) of 0.2 cm / s, and the filtrate was used as the coating liquid (3). The same measurements as in Example 11 were performed. [Example 21: No filtration]

[0107] The solution to be treated (4) was used as such without filtration as coating liquid (4).

[0108] The polymer content in the coating liquid (4) was measured. A coating layer was formed by a spin coating method, and the coating layer thickness was measured. The results are shown in Table 3 (the same applies below). [Examples 22 to 25]

[0109] Using filters as listed in Table 3, the solution to be treated (4) was subjected to syringe filtration at a filtration rate (linear velocity) of 0.2 cm / s, and the filtrate was used as the coating liquid (4). The same measurements as in Example 21 were performed. [Examples 26 to 28]

[0110] Using a capsule filter equipped with the filter (4), the solution to be treated (3) was subjected to pressure filtration at each filtration rate specified in Table 4, and the filtrate was used as the coating liquid (5). The same measurements as in Example 1 were performed. [Table 1] e.g. filter Coating composition (2) type Fluorine atom content [mass%] Pore ​​size [µm] Polymer content [mass%] Coating layer thickness after formation [nm] Content of the -119 ppm compound [mass%] 1 No filtration 5,0 33,5 1,02 2 (1) 76 0,2 5,0 35,0 0,98 3 (2) 59 0,2 5,0 38,7 0,92 4 (3) 0 0,2 5,0 41,8 0,86 5 (4) 0 0,2 5,0 41,3 0,87 [Table 2] e.g. filter Coating composition (3) type Fluorine atom content [mass%] Pore ​​size [µm] Polymer content [mass%] Coating layer thickness after formation[nm] Content of the -119 ppm compound [mass%] refractive index 11 No filtration 3,1 46,9 1,01 1,46 12 (1) 76 1,0 3,0 47,9 - - 0,45 3,1 48,0 - - 0,2 3,1 48,2 0,96 1,46 13 (2) 59 1,0 3,1 50,1 - - 0,45 3,1 51,0 - - 0,2 3,0 53,1 0,87 - 14 (3) 0 1,0 3,0 52,1 0,89 - 0,45 3,1 53,7 0,86 - 0,2 3,1 58,5 0,80 - 15 (4) 0 1,0 3,1 52,0 0,88 - 0,45 3,1 53,7 0,86 - 0,2 3,1 57,9 0,80 1,46 16 (5) 0 1,0 3,1 60,3 0,78 - 17 (1) 76 0,2 3,2 51,0 - 1,48 [Table 3] e.g. filter Coating composition (4) type Fluorine atom content [mass%] Pore ​​size [µm] Polymer content [mass%] Coating layer thickness after formation [nm] 21 No filtration 4,0 118,3 22 (1) 76 0,2 4,0 120,1 23 (2) 59 0,2 4,1 130,2 24 (3) 0 0,2 4,1 130,1 25 (4) 0 0,2 4,0 145,9 [Table 4] e.g. filter Filtration speed [cm / s] Coating composition (5) Fluorine atom content [mass%] Pore ​​size [µm] Polymer content [mass%] Coating layer thickness after formation [nm] 26 0 0,2 0,005 3,0 59,5 27 0,01 3,0 58,2 28 0,04 3,0 58,5

[0111] The Fig. Figure 1 is a graph showing the relationship between the content of the -119 ppm compound in the coating liquid and the coating layer thickness after formation in Examples 1 to 5.

[0112] As shown in Table 1, in Examples 3 to 5, in which the fluorine atom content of the filter was at most 70 mass%, the content of the -119 ppm compound in the coating liquid was less than 0.95 mass% and the coating layer thickness was considerably increased, although the polymer content was identical to that of Example 1.

[0113] In contrast, in Example 2, where the fluorine atom content of the filtrate was 76 mass%, the content of the -119 ppm compound in the coating liquid was at least 0.95 mass%, and the difference in coating layer thickness with respect to Example 1 was small. Specifically, the average coating layer thickness after formation was 33.5 nm (number of samples: 5) and 3σ = 1.5 (σ: standard deviation) in Example 1. Therefore, the coating layer thickness after formation of 35.0 nm in Example 2 was judged to be no significant difference.

[0114] The results in Tables 2 and 3 also show the same tendency regarding the relationship between the fluorine atom content of the filter and the coating layer thickness.

[0115] From the results in the Fig. 1, it can be seen that there is a correlation between the content of the -119 ppm compound in the coating composition and the coating layer thickness after formation, and the lower the content of the -119 ppm compound, the thicker the coating layer.

[0116] As shown in Table 2, the -119 ppm compound was further reduced when filtration was performed through a filter with a low fluorine atom content.

[0117] In the case where the filters are made of the same material, there is a tendency for the -119 ppm compound to be reduced more the smaller the pore size.

[0118] By comparing Examples 11, 12 and 15 in Table 2, it can be seen that the refractive index of the coating layer is not affected even if the content of the -119 ppm compound is reduced by filtration.

[0119] With the coating composition obtained in Example 17 containing polyacrylic acid having a thickening effect, the coating layer thickness increased compared with Example 12, but the refractive index increased.

[0120] Based on the results in Examples 15 and 26 to 28, it was confirmed that the coating layer thickness increases regardless of the filtration rate and filtration method when the same filter with the same pore size is used.

[0121] As described above, by performing filtration using a filter having a fluorine atom content of at most 70 mass%, the coating layer thickness could be increased without increasing the polymer content in the coating composition and without using additives such as thickeners. INDUSTRIAL APPLICABILITY

[0122] The coating composition of the present invention is suitable for forming an anti-reflection coating layer on the surface of a photoresist layer.

Claims

[1] A method for producing a coating composition, which comprises filtering a solution to be treated containing a fluorinated polymer having units represented by the following formula (1) and a solvent, the solution to be treated not containing water, with a filter having a fluorine atom content of at most 70% by mass, so that a coating composition is obtained: -[CX 1 X 2 -Cy 1 (Rf 1 -COOM 1 )]- (1) where X 1 and X 2 are each independently a hydrogen atom, a fluorine atom or a chlorine atom, Y 1 a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a trifluoromethyl group, Rf 1a straight or branched perfluoroalkylene group which may contain an ether oxygen atom between carbon-carbon atoms, or a straight or branched oxyperfluoroalkylene group which may contain an ether oxygen atom between carbon-carbon atoms, wherein the number of carbon atoms in Rf 1 from 1 to 10 in the case where Rf 1 does not contain an ether oxygen atom, and from 2 to 10 in the case where it contains an ether oxygen atom, and -COOM 1 -COOH or -COOZ 1 is (where Z 1 an ammonium ion in which the hydrogen atom may be substituted). [2] A manufacturing process according to claim 1, wherein all of X 1 , X 2 and Y 1 fluorine atoms are. [3] The production process according to claim 1 or 2, wherein the content of the units represented by the formula (1) is from 50 to 100 mol% based on all the units constituting the fluorinated polymer. [4] A manufacturing process according to any one of claims 1 to 3, wherein the fluorinated polymer has a number average molecular weight of 1000 to 30000. [5] A manufacturing process according to any one of claims 1 to 4, wherein the content of the fluorinated polymer in the solution to be treated is from 1 to 25 mass%. [6] A manufacturing method according to any one of claims 1 to 5, wherein the solvent comprises a hydrophilic organic solvent. [7] A manufacturing method according to claim 6, wherein the hydrophilic organic solvent comprises an alcohol. [8] The manufacturing method according to claim 6, wherein the hydrophilic organic solvent comprises at least one selected from the group consisting of methanol, ethanol, isopropanol, 2-butanol and a fluorinated alcohol. [9] A manufacturing process according to claim 6, wherein the hydrophilic organic solvent comprises a fluorinated alcohol. [10] Manufacturing method according to one of claims 1 to 9, wherein the filter is made of polyvinylidene fluoride, polyamide, polypropylene or glass fibers. [11] A manufacturing method according to any one of claims 1 to 10, wherein the filter has a pore size of 0.2 to 5.0 µm. [12] A method of using a coating composition, which comprises using a coating composition obtained by the manufacturing method according to any one of claims 1 to 11 to form an anti-reflection coating layer on the surface of a photoresist layer. [13] A method for producing a photoresist laminate, which comprises obtaining a coating liquid containing a coating composition prepared from a coating composition obtained by the manufacturing method according to any one of claims 1 to 11, and applying the coating liquid to the surface of a photoresist layer to obtain a photoresist laminate having an anti-reflection coating layer formed on the surface of the photoresist layer. [14] The manufacturing method according to claim 13, wherein the polymer content including the fluorinated polymer in the coating liquid is from 1 to 10 mass% and the proportion of the content of the fluorinated polymer to the polymer content is from 50 to 100 mass%. [15] A manufacturing method according to claim 13 or 14, wherein the coating liquid is applied by a spin coating method.

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