Conductive composition

Abstract

To provide a conductive composition that can form a conductive film that prevents a patterning failure when formed on a resist layer for patterning with a charged particle beam.SOLUTION: A conductive composition has a conductive polymer having an acidic group, and a solvent. Relative to the total mass of the conductive composition, each content of nylon, polyethylene and polytetrafluoroethylene is 10 mass ppm or less. The conductive composition is suitable for an antistatic use in charged particle beam drawing.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrically conductive composition. [Background technology]

[0002] Pattern formation technology using charged particle beams such as electron beams and ion beams is expected to be the next generation technology of optical lithography. When using charged particle beams, improving the sensitivity of the resist layer is important for improving productivity. Therefore, the mainstream is to use highly sensitive chemically amplified resists, which generate acid in the exposed areas or areas irradiated with charged particle beams, followed by a heating process called post-exposure bake (PEB) to promote crosslinking or decomposition reactions. Furthermore, in recent years, with the trend toward miniaturization of semiconductor devices, there has been a growing demand for control of resist shapes on the order of several nanometers.

[0003] However, in pattern formation methods using charged particle beams, there is a problem that, particularly when the substrate is insulating, the trajectory of the charged particle beam is bent due to an electric field generated by charging up the substrate, making it difficult to obtain the desired pattern. As a means for solving this problem, it is already known that a technique is effective in which a conductive composition containing a conductive polymer is applied to the surface of a resist layer to form a conductive film, and the surface of the resist layer is covered with the conductive film.

[0004] Conductive polymers having acidic groups are known as conductive polymers, and these polymers can exhibit conductivity without the addition of a dopant. For example, Patent Document 1 discloses a conductive composition containing a conductive polymer having an acidic group, a water-soluble polymer having a nitrogen-containing functional group and a terminal hydrophobic group, and a solvent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-226721 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the conductive composition described in Patent Document 1 is applied to the surface of a resist layer to form a conductive film, and then a pattern is formed using a charged particle beam, patterning defects may occur. An object of the present invention is to provide a conductive composition that can form a conductive film that is less likely to cause patterning defects when formed on a resist layer and patterned using a charged particle beam. [Means for solving the problem]

[0007] One of the causes of poor patterning is thought to be foreign matter in the conductive composition, so it is common to filter the conductive composition to remove foreign matter before applying it to the surface of the resist layer. However, since poor patterning occurs even when using a filtered conductive composition, the inventors conducted extensive research and discovered that filter-derived substances attached to the secondary side of the filter used for filtration, i.e., the surface through which the filtrate exits the filter, are mixed into the filtrate as the conductive composition passes through the filter, and appear as foreign matter in the conductive film during film formation, causing poor patterning. In particular, the inventors discovered that nylon, a substance derived from nylon filters, polyethylene, a substance derived from polyethylene filters, and polytetrafluoroethylene, a substance derived from polytetrafluoroethylene filters, affect poor patterning. Therefore, the inventors discovered that poor patterning can be suppressed by reducing the amount of these filter-derived substances in the conductive composition, leading to the completion of the present invention.

[0008] That is, the present invention has the following aspects. [1] A conductive composition comprising a conductive polymer having an acidic group and a solvent, A conductive composition, wherein the content of nylon, polyethylene, and polytetrafluoroethylene is each 10 ppm by mass or less relative to the total mass of the conductive composition. [2] The conductive composition according to [1], wherein the conductive polymer has a unit represented by the following general formula (5):

[0009] [ka]

[0010] In formula (5), R 18 ~R 21 each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, a linear or branched alkoxy group having 1 to 24 carbon atoms, an acidic group, a hydroxy group, a nitro group, or a halogen atom; R 18 ~R 21 At least one of the groups is an acidic group or a salt thereof.

[0011] [3] The conductive composition according to [1] or [2], which is used for preventing static electricity during charged particle beam writing. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a conductive composition that can form a conductive film that is less likely to cause patterning defects when formed on a resist layer and patterned using a charged particle beam. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from the spirit of the present invention.

[0014] In the present invention, "conductivity" means a value of 1×10 11 The surface resistance is determined by the potential difference between electrodes when a constant current is passed through them. In addition, in this specification, "solubility" means that 0.1 g or more of a substance dissolves uniformly in 10 g (at a liquid temperature of 25° C.) of water alone, water containing at least one of a base and a basic salt, water containing an acid, or a mixture of water and a water-soluble organic solvent. Furthermore, "water-soluble" refers to solubility in water in relation to the above solubility. In this specification, the term "terminal" in "terminal hydrophobic group" refers to a site other than the repeating units that constitute the polymer. In addition, in this specification, the "mass average molecular weight" refers to the mass average molecular weight (in terms of sodium polystyrene sulfonate) measured by gel permeation chromatography (GPC). In this specification, the surface where the filtered sample first contacts the filter is referred to as the "primary side of the filter," and the surface where the filtrate leaves the filter is referred to as the "secondary side of the filter."

[0015] [Conductive composition] The conductive composition of the present invention contains a conductive polymer (A) and a solvent (B) shown below. The conductive composition may also contain a basic compound (C), a surfactant (D), and the like, as necessary.

[0016] <Conductive polymer> The conductive polymer (A) of the present invention has an acidic group. When the conductive polymer (A) has an acidic group, its water solubility is increased. As a result, the coatability of the conductive composition containing the conductive polymer (A) is improved, and a coating film of uniform thickness can be easily obtained. The conductive polymer (A) is not particularly limited as long as it has at least one group selected from the group consisting of a sulfonic acid group and a carboxy group in the molecule, and known conductive polymers can be used as long as they have the effects of the present invention. For example, JP-A-61-197633, JP-A-63-39916, JP-A-1-301714, JP-A-5-504153, JP-A-5-503953, JP-A-4-32848, JP-A-4-328181, JP-A-6-145386, JP-A-6-56987, JP-A-5-226238, JP-A-5-178989, etc. Conductive polymers such as those disclosed in JP-A-6-293828, JP-A-7-118524, JP-A-6-32845, JP-A-6-87949, JP-A-6-256516, JP-A-7-41756, JP-A-7-48436, JP-A-4-268331, and JP-A-2014-65898 are preferred from the viewpoint of solubility.

[0017] Specific examples of the conductive polymer (A) include π-conjugated conductive polymers containing, as a repeating unit, at least one selected from the group consisting of phenylenevinylene, vinylene, thienylene, pyrrolylene, phenylene, iminophenylene, isothianaphthene, furylene, and carbazolylene, substituted at the α-position or β-position with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group. Furthermore, when the π-conjugated conductive polymer contains at least one repeating unit selected from the group consisting of iminophenylene and galvasolylene, examples of the conductive polymer include a conductive polymer having, on a nitrogen atom of the repeating unit, at least one group selected from the group consisting of a sulfonic acid group and a carboxy group, or an alkyl group substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group, or an alkyl group containing an ether bond, on the nitrogen atom. Among these, from the viewpoint of conductivity and solubility, a conductive polymer having, as a monomer unit, at least one selected from the group consisting of thienylene, pyrrolylene, iminophenylene, phenylenevinylene, carbazolylene, and isothianaphthene, substituted at the β-position with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group, is preferably used.

[0018] From the viewpoint of achieving high conductivity and solubility, the conductive polymer (A) is preferably a conductive polymer containing 20 to 100 mol % of one or more monomer units selected from the group consisting of units represented by the following general formulas (1) to (4) based on all units (100 mol %) constituting the conductive polymer.

[0019] [ka]

[0020] [ka]

[0021] [ka]

[0022] [ka]

[0023] In formulas (1) to (4), X represents a sulfur atom or a nitrogen atom, and R 1 ~R 15 each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, a linear or branched alkoxy group having 1 to 24 carbon atoms, an acidic group, a hydroxy group, a nitro group, a halogen atom (-F, -Cl, -Br or -I), -N(R 16 )2, -NHCOR 16 , -SR 16 , -OCOR 16 , -COOR 16, -COR 16 , -CHO, or -CN. 16 represents an alkyl group having 1 to 24 carbon atoms, an aryl group having 1 to 24 carbon atoms, or an aralkyl group having 1 to 24 carbon atoms. However, R in general formula (1) 1 , R 2 At least one of R in general formula (2) 3 ~R 6 At least one of R in general formula (3) 7 ~R 10 At least one of R in general formula (4) 11 ~R 15 At least one of each is an acidic group or a salt thereof.

[0024] Here, the term "acidic group" refers to a sulfonic acid group (sulfo group) or a carboxylic acid group (carboxy group). The sulfonic acid group may be contained in the acid state (-SO3H) or in the ionic state (-SO3 - Furthermore, the sulfonic acid group may be contained in a substituent (-R 17 SO3H) is also included. On the other hand, the carboxylic acid group may be contained in the acid state (-COOH) or in the ionic state (-COO - Furthermore, the carboxylic acid group may be contained in a substituent (-R 17 COOH) are also included. R 17 represents a linear or branched alkylene group having 1 to 24 carbon atoms, a linear or branched arylene group having 1 to 24 carbon atoms, or a linear or branched aralkylene group having 1 to 24 carbon atoms.

[0025] Salts of acidic groups include alkali metal salts, alkaline earth metal salts, ammonium salts, and substituted ammonium salts of sulfonic acid or carboxylic acid groups. Examples of alkali metal salts include lithium sulfate, lithium carbonate, lithium hydroxide, sodium sulfate, sodium carbonate, sodium hydroxide, potassium sulfate, potassium carbonate, potassium hydroxide, and derivatives having a skeleton of these. Examples of alkaline earth metal salts include magnesium salts and calcium salts. Examples of the substituted ammonium salt include aliphatic ammonium salts, saturated alicyclic ammonium salts, and unsaturated alicyclic ammonium salts. Examples of aliphatic ammonium salts include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methylethylammonium, diethylmethylammonium, dimethylethylammonium, propylammonium, dipropylammonium, isopropylammonium, diisopropylammonium, butylammonium, dibutylammonium, methylpropylammonium, ethylpropylammonium, methylisopropylammonium, ethylisopropylammonium, methylbutylammonium, ethylbutylammonium, tetramethylammonium, tetramethylolammonium, tetraethylammonium, tetra-n-butylammonium, tetra-sec-butylammonium, and tetra-t-butylammonium. Examples of saturated alicyclic ammonium salts include piperidinium, pyrrolidinium, morpholinium, piperazinium, and derivatives having these skeletons. Examples of unsaturated alicyclic ammonium salts include pyridinium, α-picolinium, β-picolinium, γ-picolinium, quinolinium, isoquinolinium, pyrrolinium, and derivatives having these skeletons.

[0026] The conductive polymer (A) preferably has a unit represented by the above general formula (4) from the viewpoint of being able to exhibit high conductivity, and more preferably has a monomer unit represented by the following general formula (5) from the viewpoint of being particularly excellent in solubility.

[0027] [ka]

[0028] In formula (5), R 18 ~R 21 each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, a linear or branched alkoxy group having 1 to 24 carbon atoms, an acidic group, a hydroxy group, a nitro group, or a halogen atom (-F, -Cl, -Br, or I). 18 ~R 21 At least one of the groups is an acidic group or a salt thereof.

[0029] As the unit represented by the general formula (5), R 18 ~R 21 Among these, it is preferable that one of them is a linear or branched alkoxy group having 1 to 4 carbon atoms, the other one is a sulfonic acid group, and the remaining are hydrogen.

[0030] From the viewpoint of excellent solubility in water and organic solvents regardless of pH, the conductive polymer (A) preferably contains 10 to 100 mol %, more preferably 50 to 100 mol %, and particularly preferably 100 mol % of units represented by the general formula (5) among all units (100 mol %) constituting the conductive polymer (A). In order to achieve excellent conductivity, the conductive polymer (A) preferably contains 10 or more units represented by the general formula (5) in one molecule.

[0031] Furthermore, in the conductive polymer (A), from the viewpoint of further improving solubility, the number of aromatic rings to which acidic groups are bonded relative to the total number of aromatic rings in the polymer is preferably 50% or more, more preferably 70% or more, even more preferably 80% or more, particularly preferably 90% or more, and most preferably 100%. The number of aromatic rings to which acidic groups are bonded relative to the total number of aromatic rings in the polymer refers to a value calculated from the monomer charging ratio when producing the conductive polymer (A).

[0032] In the conductive polymer (A), the substituents other than the acidic groups on the aromatic rings of the monomer units are preferably electron-donating groups from the viewpoint of imparting reactivity to the monomers. Specifically, alkyl groups having 1 to 24 carbon atoms, alkoxy groups having 1 to 24 carbon atoms, halogen groups (-F, -Cl, -Br, or -I), etc. are preferred, and among these, alkoxy groups having 1 to 24 carbon atoms are most preferred from the viewpoint of electron-donating properties.

[0033] Furthermore, the conductive polymer (A) may contain, as a structural unit other than the unit represented by the general formula (5), one or more units selected from the group consisting of substituted or unsubstituted aniline, thiophene, pyrrole, phenylene, vinylene, divalent unsaturated groups, and divalent saturated groups, as long as the solubility, conductivity, and properties are not affected.

[0034] As the conductive polymer (A), from the viewpoint of exhibiting high conductivity and solubility, a compound having a structure represented by the following general formula (6) is preferred, and among the compounds having a structure represented by the following general formula (6), poly(2-sulfo-5-methoxy-1,4-iminophenylene) is particularly preferred.

[0035] [ka]

[0036] In formula (6), R 22 ~R 37 each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched alkoxy group having 1 to 4 carbon atoms, an acidic group, a hydroxy group, a nitro group, or a halogen atom (-F, -Cl, -Br, or I). 22 ~R 37At least one of the groups is an acidic group or a salt thereof. Furthermore, n represents the degree of polymerization. In the present invention, n is preferably an integer of 5 to 2,500.

[0037] From the viewpoint of improving the conductivity, it is desirable that at least a part of the acidic groups contained in the conductive polymer (A) is in the free acid form.

[0038] The weight average molecular weight of the conductive polymer (A), calculated as sodium polystyrene sulfonate by GPC, is preferably 1,000 to 1,000,000, more preferably 1,500 to 800,000, even more preferably 2,000 to 500,000, and particularly preferably 2,000 to 100,000, from the viewpoints of conductivity, solubility, and film-forming ability. When the weight average molecular weight of the conductive polymer (A) is less than 1,000, the solubility is excellent but the conductivity and film-forming ability may be insufficient. On the other hand, when the weight average molecular weight is more than 1,000,000, the conductivity is excellent but the solubility may be insufficient. Here, "film-forming properties" refers to the property of forming a uniform film without repelling or the like, and can be evaluated by a method such as spin coating on glass.

[0039] The conductive polymer (A) can be obtained, for example, by polymerizing raw material monomers for the conductive polymer (A) in the presence of a polymerization solvent and an oxidizing agent. An example of a method for producing the conductive polymer (A) will be described below.

[0040] (Method for producing conductive polymer (A)) The method for producing the conductive polymer (A) of this embodiment includes a step of polymerizing raw material monomers for the conductive polymer (A) in the presence of a polymerization solvent and an oxidizing agent (polymerization step). The method for producing the conductive polymer (A) of this embodiment may also include a step of purifying the reaction product obtained in the polymerization step (purification step).

[0041] <<Polymerization process>> The polymerization step is a step in which raw material monomers for the conductive polymer (A) are polymerized in the presence of a polymerization solvent and an oxidizing agent. Specific examples of the raw material monomer include polymerizable monomers from which the above-mentioned monomer units are derived, and specifically include at least one selected from the group consisting of acidic group-substituted aniline, its alkali metal salt, alkaline earth metal salt, ammonium salt, and substituted ammonium salt. Examples of the acidic group-substituted aniline include sulfonic acid group-substituted anilines having a sulfonic acid group as the acidic group. Representative examples of sulfone group-substituted anilines are aminobenzenesulfonic acids, and specifically, o-, m-, and p-aminobenzenesulfonic acid, aniline-2,6-disulfonic acid, aniline-2,5-disulfonic acid, aniline-3,5-disulfonic acid, aniline-2,4-disulfonic acid, and aniline-3,4-disulfonic acid are preferably used.

[0042] Examples of sulfonic acid-substituted anilines other than aminobenzenesulfonic acids include alkyl group-substituted aminobenzenesulfonic acids such as methylaminobenzenesulfonic acid, ethylaminobenzenesulfonic acid, n-propylaminobenzenesulfonic acid, isopropylaminobenzenesulfonic acid, n-butylaminobenzenesulfonic acid, sec-butylaminobenzenesulfonic acid, and t-butylaminobenzenesulfonic acid; alkoxy group-substituted aminobenzenesulfonic acids such as methoxyaminobenzenesulfonic acid, ethoxyaminobenzenesulfonic acid, and propoxyaminobenzenesulfonic acid; hydroxy group-substituted aminobenzenesulfonic acids; nitro group-substituted aminobenzenesulfonic acids; and halogen-substituted aminobenzenesulfonic acids such as fluoroaminobenzenesulfonic acid, chloroaminobenzenesulfonic acid, and bromoaminobenzenesulfonic acid. Among these, alkyl group-substituted aminobenzenesulfonic acids, alkoxy group-substituted aminobenzenesulfonic acids, hydroxy group-substituted aminobenzenesulfonic acids, and halogen-substituted aminobenzenesulfonic acids are preferred in that they can give a conductive polymer (A) that is particularly excellent in conductivity and solubility, and alkoxy group-substituted aminobenzenesulfonic acids, their alkali metal salts, ammonium salts, and substituted ammonium salts are particularly preferred in that they are easy to produce. These sulfonate group-substituted anilines may be used alone or in combination of two or more in any desired ratio.

[0043] Examples of the polymerization solvent include water, an organic solvent, a mixed solvent of water and an organic solvent, etc. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, propyl alcohol, and butanol; ketones such as acetone and ethyl isobutyl ketone; ethylene glycols such as ethylene glycol and ethylene glycol methyl ether; propylene glycols such as propylene glycol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether, and propylene glycol propyl ether; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; and pyrrolidones such as N-methylpyrrolidone and N-ethylpyrrolidone. The polymerization solvent is preferably water or a mixed solvent of water and an organic solvent.

[0044] The oxidizing agent is not limited as long as it has a standard electrode potential of 0.6 V or higher, and examples thereof include peroxodisulfuric acid compounds such as peroxodisulfuric acid, ammonium peroxodisulfate, sodium peroxodisulfate, and potassium peroxodisulfate; hydrogen peroxide; and the like. These oxidizing agents may be used either alone or as a mixture of two or more kinds in any ratio.

[0045] In the polymerization step, raw material monomers may be polymerized in the presence of a basic reaction aid in addition to a polymerization solvent and an oxidizing agent. Examples of the basic reaction aid include inorganic bases such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; ammonia; aliphatic amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylmethylamine, ethyldimethylamine, and diethylmethylamine; cyclic saturated amines; and cyclic unsaturated amines such as pyridine, α-picoline, β-picoline, γ-picoline, and quinoline. Among these, inorganic bases, aliphatic amines, and cyclic unsaturated amines are preferred, with cyclic unsaturated amines being more preferred. These basic reaction auxiliaries may be used either alone or as a mixture of two or more kinds in any ratio.

[0046] Examples of the polymerization method include a method of adding a raw material monomer solution dropwise into an oxidizing agent solution, a method of adding an oxidizing agent solution dropwise into a raw material monomer solution, a method of adding a raw material monomer solution and an oxidizing agent solution dropwise simultaneously into a reaction vessel, etc. The raw material monomer solution may contain a basic reaction aid, if necessary. The above-mentioned polymerization solvents can be used as the solvents for the oxidizing agent solution and the raw material monomer solution.

[0047] The reaction temperature of the polymerization reaction is preferably 50°C or lower, more preferably -15 to 30°C, and even more preferably -10 to 20°C. If the reaction temperature of the polymerization reaction is 50°C or lower, particularly 30°C or lower, it is possible to prevent the progression of side reactions and a decrease in conductivity due to changes in the redox structure of the main chain of the resulting conductive polymer (A). If the reaction temperature of the polymerization reaction is -15°C or higher, it is possible to maintain a sufficient reaction rate and shorten the reaction time.

[0048] By the polymerization step, the conductive polymer (A) which is the reaction product is obtained in a state of being dissolved or precipitated in the polymerization solvent. When the reaction product is dissolved in the polymerization solvent, the polymerization solvent is distilled off to obtain the reaction product. When the reaction product is precipitated in the polymerization solvent, the polymerization solvent is filtered off using a filter such as a centrifugal separator to obtain the reaction product.

[0049] The reaction products may contain low-molecular-weight components such as unreacted raw material monomers, oligomers resulting from side reactions, acidic substances (free acidic groups released from the conductive polymer (A) and sulfate ions that are decomposition products of the oxidizing agent), and basic substances (basic reaction aids and ammonium ions that are decomposition products of the oxidizing agent). These low-molecular-weight components are impurities that inhibit conductivity. Therefore, it is preferable to purify the reaction product to remove low molecular weight components.

[0050] <<Purification process>> The purification step is a step of purifying the reaction product obtained in the polymerization step. The reaction product can be purified by any method, including washing using a washing solvent, membrane filtration, ion exchange, removal of impurities by heat treatment, and neutralization precipitation. Among these, washing and ion exchange are effective in terms of easily obtaining a highly pure conductive polymer (A). In particular, washing is preferred in terms of efficiently removing raw material monomers, oligomers, acidic substances, etc. Ion exchange is preferred in terms of efficiently removing basic substances that exist in the form of salts with the acidic groups of the conductive polymer (A). In the purification step, washing and ion exchange may be used in combination.

[0051] Examples of cleaning solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol, 3-butanol, t-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, n-hexanol, 4-methyl-2-pentanol, 2-ethylbutynol, benzyl alcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol; polyhydric alcohol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methoxymethoxyethanol, propylene glycol monoethyl ether, and glyceryl monoacetate; acetone; acetonitrile; N,N-dimethylformamide; N-methylpyrrolidone; and dimethyl sulfoxide. Among these, methanol, ethanol, isopropanol, acetone, and acetonitrile are effective.

[0052] The reaction product after washing, that is, the conductive polymer (A) after washing, is dried to obtain a solid conductive polymer (A).

[0053] Examples of the ion exchange method include column-type and batch-type treatments using ion exchange resins such as cation exchange resins and anion exchange resins; and electrodialysis. If the reaction product is dissolved in the polymerization solvent, it may be brought into contact with the ion exchange resin in the dissolved state. If the reaction product is highly concentrated, it may be diluted with an aqueous medium. When the reaction product is precipitated in the polymerization solvent, it is preferable to filter off the polymerization solvent, then dissolve the reaction product in an aqueous medium to a desired solid content concentration, prepare a polymer solution, and then contact the solution with the ion exchange resin. When the washed reaction product is subjected to ion exchange treatment, it is preferable to dissolve the washed reaction product in an aqueous medium to a desired solid content concentration, prepare a polymer solution, and then contact the solution with an ion exchange resin. Examples of the aqueous medium include the same as the solvent (B) described below. The concentration of the conductive polymer (A) in the polymer solution is preferably from 0.1 to 20% by mass, more preferably from 0.1 to 10% by mass, from the viewpoints of industrial feasibility and purification efficiency.

[0054] In the case of an ion exchange method using an ion exchange resin, the amount of sample solution relative to the ion exchange resin is preferably up to 10 times the volume of the ion exchange resin, and more preferably up to 5 times the volume, for example, in the case of a polymer solution with a solids concentration of 5% by mass. Examples of cation exchange resins include "Amberlite IR-120B" manufactured by Organo Corporation. Examples of anion exchange resins include "Amberlite IRA410" manufactured by Organo Corporation.

[0055] After the ion exchange treatment, the conductive polymer (A) is in a state of being dissolved in the polymerization solvent or aqueous medium. Therefore, if the polymerization solvent or aqueous medium is completely removed using an evaporator or the like, a solid conductive polymer (A) can be obtained, but the conductive polymer (A) may be used in the state of being dissolved in the polymerization solvent or aqueous medium for producing a conductive composition.

[0056] The content of the conductive polymer (A) is preferably from 0.1 to 5 mass %, more preferably from 0.2 to 3 mass %, and even more preferably from 0.5 to 2 mass %, based on the total mass of the conductive composition. The content of the conductive polymer (A) is preferably 50 to 100 mass %, more preferably 80 to 100 mass %, and even more preferably 95 to 100 mass %, based on the total mass of the solid content of the conductive composition. The solid content of the conductive composition is the residue after removing the solvent (B) from the conductive composition. When the content of the conductive polymer (A) is within the above range, the balance between the coatability of the conductive composition and the conductivity of the coating film formed from the conductive composition is excellent.

[0057] <Solvent (B)> The solvent (B) is not particularly limited as long as it is a solvent that can dissolve the conductive polymer (A), the basic compound (C) and the surfactant (D) described below, and has the effects of the present invention. Examples of the solvent include water, an organic solvent, and a mixed solvent of water and an organic solvent. Examples of water include tap water, ion-exchanged water, pure water, ultrapure water, and distilled water. Examples of the organic solvent include the organic solvents among the polymerization solvents exemplified above in the description of the production method for the conductive polymer (A). When a mixed solvent of water and an organic solvent is used as the solvent (B), the mass ratio thereof (water / organic solvent) is preferably 1 / 100 to 100 / 1, and more preferably 2 / 100 to 100 / 2.

[0058] The content of the solvent (B) is preferably 1 to 99.9 mass %, more preferably 10 to 98 mass %, and even more preferably 50 to 98 mass %, relative to the total mass of the conductive composition. When the content of the solvent (B) is within the above range, the coating property is further improved. In addition, when the conductive polymer (A) is used in a state in which it is purified by an ion exchange method and dissolved in a polymerization solvent or an aqueous medium (hereinafter, the conductive polymer (A) in this state is also referred to as a "conductive polymer solution"), the polymerization solvent or aqueous medium derived from the conductive polymer solution is also included in the content of the solvent (B) in the conductive composition.

[0059] <Basic Compound (C)> The conductive composition may contain a basic compound (C). It is believed that if the conductive composition contains the basic compound (C), it will be possible to increase the stability of the conductive polymer (A).

[0060] The basic compound (C) is not particularly limited as long as it is a compound having basicity, and examples thereof include the following quaternary ammonium salt (c-1), basic compound (c-2), and basic compound (c-3). Quaternary ammonium salt (c-1): A quaternary ammonium compound in which at least one of the four substituents bonded to the nitrogen atom is a hydrocarbon group having three or more carbon atoms. Basic compound (c-2): A basic compound having one or more nitrogen atoms (excluding quaternary ammonium salts (c-1) and basic compounds (c-3)). Basic compound (c-3): A basic compound having a basic group and two or more hydroxy groups in the same molecule and having a melting point of 30°C or higher.

[0061] In the quaternary ammonium compound (c-1), the nitrogen atom to which the four substituents are bonded is the nitrogen atom of a quaternary ammonium ion. In the quaternary ammonium compound (c-1), examples of the hydrocarbon group bonded to the nitrogen atom of the quaternary ammonium ion include an alkyl group, an aralkyl group, and an aryl group. Examples of the quaternary ammonium compound (c-1) include tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, and benzyltrimethylammonium hydroxide.

[0062] Examples of the basic compound (c-2) include ammonia, pyridine, triethylamine, 4-dimethylaminopyridine, 4-dimethylaminomethylpyridine, 3,4-bis(dimethylamino)pyridine, 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), and derivatives thereof.

[0063] In the basic compound (c-3), examples of the basic group include basic groups defined as Arrhenius bases, Bronsted bases, Lewis bases, etc. Specific examples include ammonia, etc. The hydroxy group may be in the -OH state or may be protected by a protecting group. Examples of the protecting group include an acetyl group; silyl groups such as trimethylsilyl and t-butyldimethylsilyl; acetal-type protecting groups such as methoxymethyl, ethoxymethyl, and methoxyethoxymethyl; benzoyl; and alkoxide groups. Examples of the basic compound (c-3) include 2-amino-1,3-propanediol, tris(hydroxymethyl)aminomethane, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid, and N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid.

[0064] These basic compounds may be used either alone or as a mixture of two or more kinds in any ratio. Among these, it is preferable to contain at least one selected from the group consisting of quaternary ammonium salts (c-1) and basic compounds (c-2) because they easily form salts with the acidic groups of the conductive polymer (A).

[0065] The content of the basic compound (C) is preferably 0.1 to 1 mol equivalent, more preferably 0.1 to 0.9 mol equivalent, per mol of units having an acidic group among the units constituting the conductive polymer (A) from the viewpoint of further improving the coatability of the conductive composition, and particularly preferably 0.25 to 0.85 mol equivalent, from the viewpoint of excellent performance retention as a conductive film and further stabilizing the acidic groups in the conductive polymer (A).

[0066] <Surfactant (D)> The conductive composition may contain a surfactant (D). If the conductive composition contains a surfactant (D), the coating properties of the conductive composition when applied to the surface of a substrate or a resist layer are improved. Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. These surfactants may be used alone or in combination of two or more in any proportion.

[0067] Examples of anionic surfactants include sodium octanoate, sodium decanoate, sodium laurate, sodium myristate, sodium palmitate, sodium stearate, perfluorononanoic acid, sodium N-lauroyl sarcosinate, sodium cocoyl glutamate, alpha sulfo fatty acid methyl ester salts, sodium lauryl sulfate, sodium myristyl sulfate, sodium laureth sulfate, sodium polyoxyethylene alkylphenol sulfonate, ammonium lauryl sulfate, lauryl phosphoric acid, sodium lauryl phosphate, and potassium lauryl phosphate.

[0068] Examples of cationic surfactants include tetramethylammonium chloride, tetramethylammonium hydroxide, tetrabutylammonium chloride, dodecyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, alkyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, benzalkonium chloride, benzalkonium bromide, benzethonium chloride, dialkyldimethylammonium chloride, didecyldimethylammonium chloride, distearyldimethylammonium chloride, monomethylamine hydrochloride, dimethylamine hydrochloride, trimethylamine hydrochloride, butylpyridinium chloride, dodecylpyridinium chloride, and cetylpyridinium chloride.

[0069] Examples of amphoteric surfactants include lauryl dimethylaminoacetic acid betaine, stearyl dimethylaminoacetic acid betaine, dodecylaminomethyl dimethyl sulfopropyl betaine, octadecylaminomethyl dimethyl sulfopropyl betaine, cocamidopropyl betaine, cocamidopropyl hydroxysultaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, sodium lauroyl glutamate, potassium lauroyl glutamate, lauroyl methyl-β-alanine, lauryl dimethylamine-N-oxide, and oleyl dimethylamine N-oxide.

[0070] Examples of nonionic surfactants include glyceryl laurate, glyceryl monostearate, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkyl ethers, pentaethylene glycol monododecyl ether, octaethylene glycol monododecyl ether, polyoxyethylene alkylphenyl ethers, octylphenol ethoxylate, nonylphenol ethoxylate, polyoxyethylene polyoxypropylene glycol, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene hexitane fatty acid esters, sorbitan fatty acid ester polyethylene glycol, lauric acid diethanolamide, oleic acid diethanolamide, stearic acid diethanolamide, octyl glucoside, decyl glucoside, lauryl glucoside, cetanol, stearyl alcohol, and oleyl alcohol.

[0071] In addition to the above, water-soluble polymers having nitrogen-containing functional groups and terminal hydrophobic groups may also be used as nonionic surfactants. Unlike conventional surfactants, these water-soluble polymers possess surface activity due to the main chain portion (hydrophilic portion) having nitrogen-containing functional groups and the terminal hydrophobic groups, resulting in a high effect of improving coatability. Therefore, excellent coatability can be imparted to the conductive composition without the need for the use of other surfactants. Furthermore, these water-soluble polymers contain no acids or bases and are less likely to produce by-products upon hydrolysis, resulting in minimal adverse effects on resist layers, etc.

[0072] As the nitrogen-containing functional group, an amide group is preferred from the viewpoint of solubility. Examples of the terminal hydrophobic group include an alkyl group, an aralkyl group, an aryl group, an alkoxy group, an aralkyloxy group, an aryloxy group, an alkylthio group, an aralkylthio group, an arylthio group, a primary or secondary alkylamino group, an aralkylamino group, an arylamino group, etc. Among these, an alkylthio group, an aralkylthio group, and an arylthio group are preferred. The terminal hydrophobic group preferably has 3 to 100 carbon atoms, more preferably 5 to 50 carbon atoms, and particularly preferably 7 to 30 carbon atoms. The number of terminal hydrophobic groups in the water-soluble polymer is not particularly limited. When the water-soluble polymer has two or more terminal hydrophobic groups in the same molecule, the terminal hydrophobic groups may be the same or different.

[0073] The water-soluble polymer is preferably a compound having a main chain structure that is a homopolymer of a vinyl monomer having a nitrogen-containing functional group or a copolymer of a vinyl monomer having a nitrogen-containing functional group and a vinyl monomer (other vinyl monomer) that does not have a nitrogen-containing functional group, and that has a hydrophobic group at a site other than the repeating units that constitute the polymer. Examples of vinyl monomers having a nitrogen-containing functional group include acrylamide and its derivatives, heterocyclic monomers having a nitrogen-containing functional group, etc., and among these, those having an amide bond are preferred. Specific examples include acrylamide, N,N-dimethylacrylamide, N-isopropylacrylamide, N,N-diethylacrylamide, N,N-dimethylaminopropylacrylamide, t-butylacrylamide, diacetoneacrylamide, N,N'-methylenebisacrylamide, N-vinyl-N-methylacrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, etc. Among these, acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, etc. are particularly preferred from the viewpoint of solubility. The other vinyl monomer is not particularly limited as long as it is copolymerizable with a vinyl monomer having a nitrogen-containing functional group, and examples thereof include styrene, acrylic acid, vinyl acetate, and long-chain α-olefins.

[0074] The method for introducing a terminal hydrophobic group into a water-soluble polymer is not particularly limited, but it is usually preferable to introduce it by selecting a chain transfer agent during vinyl polymerization, as this is simple and convenient.In this case, the chain transfer agent is not particularly limited as long as it is one that introduces a group containing a hydrophobic group, such as an alkyl group, an aralkyl group, an aryl group, an alkylthio group, an aralkylthio group, or an arylthio group, into the terminal of the resulting polymer.For example, when obtaining a water-soluble polymer having an alkylthio group, an aralkylthio group, or an arylthio group as the terminal hydrophobic group, it is preferable to carry out vinyl polymerization using a chain transfer agent having a hydrophobic group corresponding to these terminal hydrophobic groups, specifically thiol, disulfide, thioether, etc.

[0075] The main chain portion of the water-soluble polymer is water-soluble and has a nitrogen-containing functional group. The number of units (degree of polymerization) in the main chain portion per molecule is preferably 2 to 1000, more preferably 3 to 1000, and particularly preferably 5 to 10. If the number of units in the main chain portion having a nitrogen-containing functional group is too large, the surface activity tends to decrease. The molecular weight ratio (mass average molecular weight of main chain portion / mass average molecular weight of terminal hydrophobic group portion) of the water-soluble polymer to the terminal hydrophobic group portion (e.g., alkyl group, aralkyl group, aryl group, alkylthio group, aralkylthio group, arylthio group, etc.) is preferably 0.3 to 170.

[0076] Of the surfactants mentioned above, nonionic surfactants are preferred as the surfactant (D) because they have little effect on the resist layer.

[0077] The content of the surfactant (D) is preferably 5 to 80 parts by mass, more preferably 10 to 70 parts by mass, and even more preferably 10 to 60 parts by mass, relative to 100 parts by mass of the total of the conductive polymer (A), the basic compound (C), and the surfactant (D). When the content of the surfactant (D) is within the above range, the coatability of the conductive composition onto the resist layer is further improved.

[0078] <Optional ingredients> The conductive composition may contain components (optional components) other than the conductive polymer (A), the solvent (B), the basic compound (C) and the surfactant (D), as needed. Examples of optional components include polymer compounds (excluding the conductive polymer (A), the basic compound (C) and the surfactant (D)), additives, and the like.

[0079] Examples of the polymer compound include polyvinyl alcohol derivatives such as polyvinyl formal and polyvinyl butyral, polyacrylamides such as polyacrylamide, poly(Nt-butylacrylamide), and polyacrylamidomethylpropanesulfonic acid, polyvinylpyrrolidone, polyacrylic acids, water-soluble alkyd resins, water-soluble melamine resins, water-soluble urea resins, water-soluble phenolic resins, water-soluble epoxy resins, water-soluble polybutadiene resins, water-soluble acrylic resins, water-soluble urethane resins, water-soluble acrylic-styrene copolymer resins, water-soluble vinyl acetate acrylic copolymer resins, water-soluble polyester resins, water-soluble styrene-maleic acid copolymer resins, water-soluble fluororesins, and copolymers thereof. Examples of additives include pigments, antifoaming agents, ultraviolet absorbers, antioxidants, heat resistance improvers, leveling agents, anti-sagging agents, matting agents, and preservatives.

[0080] <Method of manufacturing conductive composition> The conductive composition can be obtained by mixing the conductive polymer (A) and solvent (B) described above with one or more of the basic compound (C), surfactant (D), and optional components, as needed. If the conductive composition thus obtained contains foreign matter, this can cause poor patterning after charged particle beam writing, so it is preferable to remove the foreign matter using a filter. That is, the method for producing a conductive composition includes a step (filtration step) of filtering a mixture (M) containing a conductive polymer (A) and a solvent (B). The mixture (M) may contain one or more of a basic compound (C), a surfactant (D), and optional components, as needed. Here, foreign matter contained in the conductive composition before filtration includes, for example, particles floating in the air, particles generated from various frictional materials, and particles contained in the components that make up the conductive composition.

[0081] When using the washed conductive polymer (A), since the washed conductive polymer (A) is in a solid state, a conductive polymer solution may be prepared in advance by mixing the solid conductive polymer (A) with a solvent (B), and the obtained conductive polymer solution may be used as the mixture (M). Furthermore, if necessary, the basic compound (C), the surfactant (D), and one or more optional components may be added to the conductive polymer solution to prepare the mixture (M). When using the conductive polymer (A) after ion exchange treatment, the conductive polymer (A) after ion exchange treatment is obtained in the form of a conductive polymer solution as described above. Therefore, this conductive polymer solution may be used as the mixture (M) as is, or may be further diluted with a solvent (B). Furthermore, if necessary, the basic compound (C), surfactant (D), and one or more optional components may be added to the conductive polymer solution to form the mixture (M).

[0082] Examples of the filtration method include microfiltration, ultrafiltration, circulation filtration, etc. Among these, microfiltration and circulation filtration are preferred from the viewpoints that the composition ratio of the conductive composition is less likely to change before and after filtration and that filtration accuracy is high.

[0083] Examples of materials for the filter used for filtration include organic membranes such as nylon, polyethylene, polypropylene, polytetrafluoroethylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, etc. Among these, nylon, polyethylene, and polytetrafluoroethylene are preferred from the viewpoint of excellent solvent resistance. Examples of nylon include nylon 6, nylon 66, nylon 610, and nylon 612. The pore size of the filter is preferably 5 to 100 nm in the case of microfiltration.

[0084] The pressure during filtration depends on the filter material and the filtering device, but is preferably about 0.005 to 1.0 MPa in consideration of productivity.

[0085] Incidentally, filter-derived substances may adhere to the surface of a new filter. Here, the filter-derived substances are, for example, nylon in the case of a nylon filter, polyethylene in the case of a polyethylene filter, and polytetrafluoroethylene in the case of a polytetrafluoroethylene filter. In particular, if these filter-derived substances adhere to the secondary side of the filter, the filter-derived substances will peel off from the filter and be mixed into the filtrate when the mixture (M) passes through the filter. Since filter-derived substances can cause patterning defects, the mixture (M) is filtered to prevent the filter-derived substances from being mixed into the filtrate.

[0086] The following methods can be used to filter the mixture (M) so that the filtrate is not contaminated with substances derived from the filter. (i) Before filtration, the filter is washed. (ii) The filtrate is separated into a first fraction and a main fraction, and the main fraction is recovered as a conductive composition. (iii) The mixture (M) is circulated and filtered.

[0087] By washing the filter in advance, filter-derived substances adhering to the filter surface are removed. Therefore, if the washed filter is used to filter the mixture (M), the contamination of the filter-derived substances in the filtrate is suppressed. The cleaning liquid used to clean the filter may be, for example, the same solvent as the solvent (B) contained in the conductive composition. The filter is preferably washed until the content of filter-derived substances in the washing liquid after washing the filter is 10 mass ppm or less relative to the total mass of the washing liquid. The mixture (M) is filtered using the washed filter, and the filtrate is recovered as a conductive composition.

[0088] When the mixture (M) is filtered using an unwashed filter, as described above, the filtrate may be contaminated with filter-derived substances. In particular, the filtrate obtained at the beginning of the filtration process contains a large amount of filter-derived substances. Therefore, the filtrate is separated into an initial fraction and a main fraction, and the main fraction is recovered as a conductive composition. Specifically, the content of filter-derived substances in the filtrate is monitored, and the filtrate whose content of filter-derived substances is 10 mass ppm or less relative to the total mass of the filtrate is defined as the main fraction. The initial fraction of the filtrate may be discarded, or may be further filtered. When filtering the initial fraction, it may be mixed with the mixture (M) and filtered, or it may be filtered using the same filter after filtering the mixture (M).

[0089] Furthermore, when filtering the mixture (M) using an unwashed filter, the mixture (M) may be circulated through filtration. As mentioned above, the filtrate may contain filter-derived substances. However, these filter-derived substances are larger than the pore size of the filter and therefore are difficult to pass through the filter. Therefore, by circulating and filtering the mixture (M), i.e., by filtering the filtrate again using the same filter, the filter-derived substances in the filtrate are removed from the filtrate. Note that, since the filter-derived substances adhering to the secondary side of the filter are mostly transferred to the filtrate during the first filtration, contamination of the filtrate with filter-derived substances from the filter used in the first filtration is unlikely during subsequent filtrations. The circulating filtration is carried out until the content of filter-derived substances in the filtrate becomes 10 mass ppm or less with respect to the total mass of the filtrate. The filtrate after the circulating filtration is recovered as a conductive composition.

[0090] The filtered conductive composition thus obtained has a low content of filter-derived substances. Specifically, the content of nylon, polyethylene, and polytetrafluoroethylene in the conductive composition is 10 mass ppm or less, and preferably 7 mass ppm or less, each relative to the total mass of the conductive composition. The smaller the content of nylon, polyethylene and polytetrafluoroethylene in the conductive composition, the more preferable.

[0091] The content of filter-derived substances can be determined by elemental analysis such as inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence spectrometry, and atomic absorption spectrometry. For example, when measuring the nylon content in a measurement sample such as a cleaning solution, filtrate, or conductive composition, the measurement sample is first filtered using a filter other than nylon (e.g., a polyethylene or polytetrafluoroethylene filter).The residue is then subjected to elemental analysis, and the nylon content in the measurement sample is qualitatively analyzed from the nitrogen element content. When measuring the polyethylene content in a measurement sample, the measurement sample is first filtered using a filter other than polyethylene (for example, a nylon or polytetrafluoroethylene filter). Next, the weight of the residue is measured, and the structure is identified by infrared absorption spectroscopy, and the polyethylene content in the measurement sample is quantitatively analyzed from the content. When measuring the polytetrafluoroethylene content in a measurement sample, the measurement sample is first filtered using a filter other than polytetrafluoroethylene (for example, a nylon or polyethylene filter). Next, the weight of the residue is measured, and then elemental analysis is performed to qualitatively analyze the polytetrafluoroethylene content in the measurement sample from the fluorine content.

[0092] Furthermore, since the conductive composition of the present invention is filtered, foreign matter other than filter-derived substances (e.g., particles floating in the air, particles generated from various frictional materials, particles contained in the components that make up the conductive composition, etc.) is also sufficiently removed. Specifically, the content of foreign matter other than filter-derived substances in the conductive composition tends to be 100 particles / mL or less relative to the total volume and mass of the conductive composition. The content of foreign matter other than filter-derived substances is determined using a liquid particle counter.

[0093] <Action and effect> As described above, if the conductive composition after filtration contains filter-derived substances, the filter-derived substances will appear as foreign matter in the conductive film during film formation, and the conductive film containing the foreign matter may experience problems such as line breaks after drawing with a charged particle beam, resulting in poor patterning. However, in the conductive composition of the present invention, the content of filter-derived substances, specifically nylon, polyethylene, and polytetrafluoroethylene, is sufficiently reduced to 10 mass ppm or less, respectively, relative to the total mass of the conductive composition. Moreover, since the conductive composition of the present invention is filtered, foreign matter other than filter-derived substances is also sufficiently removed. Therefore, the conductive composition of the present invention can form a conductive film with little filter-derived substances and other foreign matter. Therefore, when a conductive film is formed on a resist layer using the conductive composition of the present invention and a pattern is formed using a charged particle beam, patterning defects are unlikely to occur. Furthermore, since the conductive composition of the present invention has already been filtered, there is no need to filter it again before use.

[0094] <Application> The conductive composition of the present invention is suitable for use in preventing static electricity during charged particle beam writing. Specifically, the conductive composition of the present invention is applied to the surface of a resist layer used in a charged particle beam patterning method using a chemically amplified resist to form a conductive film. The conductive film thus formed serves as an antistatic film for the resist layer. In addition to the above, the conductive composition of the present invention can also be used as a material for capacitors, transparent electrodes, semiconductors, etc. [Example]

[0095] The present invention will be described in more detail below with reference to examples, but the following examples are not intended to limit the scope of the present invention. The various measurement and evaluation methods used in the examples and comparative examples are as follows.

[0096] [Measurement and evaluation method] <Measurement of nylon content> The conductive composition was filtered using a polyethylene filter, and the residue was then subjected to elemental analysis using an Agilent Technologies 7500cs inductively coupled plasma mass spectrometer (ICP-MS), and the nylon content in the measurement sample was qualitatively analyzed based on the nitrogen content. The detection limit of this analyzer is 0.01 ppm by mass.

[0097] <Measurement of the content of foreign matter other than substances derived from the filter> The content of particles (particle diameter of 5 μm or more) in the solution was measured using a liquid particle counter.

[0098] <Evaluation of conductivity> 2.0 mL of the conductive composition was dropped onto a glass substrate as a substrate, and the composition was spin-coated using a spin coater at 2000 rpm for 60 seconds to form a coating film covering the entire surface of the substrate. The coating film was then heated on a hot plate at 80°C for 2 minutes to form a conductive film with a thickness of approximately 30 nm on the substrate, thereby obtaining a conductor. The surface resistance value [Ω / □] of the conductive film was measured by the two-terminal method (electrode distance 20 mm) using a Hiresta UX-MCP-HT800 (manufactured by Mitsubishi Chemical Analytech Corporation).

[0099] [Example 1] To 100 mmol of 2-aminoanisole-4-sulfonic acid, 100 mmol of pyridine and 100 mL of water were added to obtain a monomer solution. To the resulting monomer solution, an aqueous solution of 100 mmol of ammonium peroxodisulfate (oxidant solution) was added dropwise at 10° C. After the dropwise addition was completed, the mixture was further stirred at 25° C. for 15 hours, then heated to 35° C. and further stirred for 2 hours to obtain a reaction solution in which the reaction product had precipitated. The resulting reaction solution was filtered using a centrifugal filter, and the precipitate (reaction product) was collected. The reaction product was washed with 1 L of methanol and then dried. 20 g of the dried reaction product was dissolved in 980 g of ultrapure water to obtain 1000 g of a conductive polymer solution (A1-1) with a solid content of 2 mass%. The obtained conductive polymer solution (A1-1) was used as a mixture (M1), and 1 L of the mixture (M1) was passed through a filter using a pressure filtration device under a constant pressure of 0.05 MPa, and all of the filtrate was recovered as a conductive composition. The filter used was a nylon filter (Ny-10nm) with a pore size of 10 nm that was washed with ultrapure water until the nylon content in the cleaning solution (ultrapure water) after washing the filter was 10 ppm by mass or less relative to the total mass of the cleaning solution. The resulting conductive composition was measured for the content of nylon, a substance derived from the filter, and foreign matter other than substances derived from the filter. The conductivity was also evaluated. The results are shown in Table 1.

[0100] [Example 2] In the same manner as in Example 1, a mixture (M1) was obtained. 1 L of the obtained mixture (M1) was passed through an unwashed nylon filter (Ny-10 nm). The filtrate after passing 0.5 mL from the start of filtration was taken as the main fraction and recovered as a conductive composition. The resulting conductive composition was measured for the content of nylon, a substance derived from the filter, and for foreign matter other than substances derived from the filter. The conductivity was also evaluated. The results are shown in Table 1.

[0101] [Example 3] In the same manner as in Example 1, a mixture (M1) was obtained. 1 L of the obtained mixture (M1) was passed through an unwashed nylon filter (Ny-10 nm). All of the filtrate was passed through the same filter again to perform circulating filtration. All of the filtrate after the second filtration was collected as a conductive composition. The resulting conductive composition was measured for the content of nylon, a substance derived from the filter, and foreign matter other than substances derived from the filter. The conductivity was also evaluated. The results are shown in Table 1.

[0102] [Comparative Example 1] In the same manner as in Example 1, a mixture (M1) was obtained. 1 L of the obtained mixture (M1) was passed through an unwashed nylon filter (Ny-10 nm), and the entire filtrate was collected as a conductive composition. The resulting conductive composition was measured for the content of nylon, a substance derived from the filter, and foreign matter other than substances derived from the filter. The conductivity was also evaluated. The results are shown in Table 1.

[0103] [Table 1]

[0104] As is clear from Table 1, the content of nylon, a substance derived from the filter, was 10 ppm by mass or less in the conductive compositions obtained in Examples 1 to 3. Therefore, a conductive film with little foreign matter can be formed, and therefore, when a conductive film is formed on a resist layer and a pattern is formed using a charged particle beam, patterning defects are less likely to occur. On the other hand, the conductive composition obtained in Comparative Example 1 contained a large amount of nylon, a substance derived from the filter, which made it prone to patterning defects when a conductive film was formed on a resist layer and then patterned using a charged particle beam. Note that a nylon filter was used in the production of the conductive composition in Examples 1 to 3 and Comparative Example 1. Therefore, the filtrate was not contaminated with filter-derived substances other than nylon, specifically polyethylene and polytetrafluoroethylene, and the content of filter-derived substances other than nylon, specifically polyethylene and polytetrafluoroethylene, in the conductive composition obtained in each example was below the detection limit. [Industrial Applicability]

[0105] The conductive composition of the present invention can form a conductive film that is less likely to cause patterning defects when formed on a resist layer and patterned using a charged particle beam, and is useful for preventing static buildup during charged particle beam drawing.

Claims

1. A conductive composition comprising a conductive polymer having an acidic group and a solvent, The content of nylon, polyethylene, and polytetrafluoroethylene is each 10 ppm by mass or less relative to the total mass of the conductive composition (excluding the case where all of nylon, polyethylene, and polytetrafluoroethylene are 0 ppm by mass), A conductive composition, wherein the content of particles having a particle diameter of 5 μm or more in the conductive composition is less than 80 particles / mL with respect to the total volume mass of the conductive composition.

2. The conductive composition according to claim 1 , wherein the conductive polymer has a unit represented by the following general formula (5): 【Chemistry 1】 In formula (5), R １８ ~R ２１ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, a linear or branched alkoxy group having 1 to 24 carbon atoms, an acidic group, a hydroxy group, a nitro group, or a halogen atom; R １８ ~R ２１ At least one of the groups is an acidic group or a salt thereof.

3. The conductive composition according to claim 1 or 2, which is used for preventing static electricity during charged particle beam drawing.

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