JP2020084004A - Conductive polymer and conductive composition - Google Patents

Abstract

To provide a conductive polymer and a conductive composition, from which a conductive film having little film reduction of a resist layer can be formed.SOLUTION: The conducive polymer has an acidic group, in which the content of an acidic substance having a molecular weight of 100 or less is 10000 ppm by mass or less. The conductive composition comprises the above conductive polymer and a solvent. The conductive polymer is suitable for the purpose of an antistatic effect in charged particle beam drawing.SELECTED DRAWING: None

Description

The present invention relates to conductive polymers and conductive compositions.

A pattern forming technique using a charged particle beam such as an electron beam or an ion beam is expected as a next-generation technique of photolithography. When using a charged particle beam, it is important to improve the sensitivity of the resist layer in order to improve productivity.
Therefore, a highly sensitive chemically-amplified resist that generates an acid in an exposed portion or a portion irradiated with a charged particle beam and then accelerates a crosslinking reaction or a decomposition reaction by a heat treatment called a post-exposure bake (PEB) treatment. Mainly used.
In addition, in recent years, with the trend toward miniaturization of semiconductor devices, management of resist shapes on the order of several nm has been required.

By the way, in a pattern forming method using a charged particle beam, especially when the substrate is insulative, the trajectory of the charged particle beam is bent due to the electric field generated by charging (charge-up) of the substrate, and a desired pattern is obtained. There is a problem that it is hard to be caught.
As a means for solving this problem, a technique of applying a conductive composition containing a conductive polymer to the surface of a resist layer to form a conductive film and coating the surface of the resist layer with the conductive film is effective. Already known.

As a conductive polymer, a conductive polymer having an acidic group is known. The conductive polymer having an acidic group can exhibit conductivity without adding a doping agent.
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.

JP, 2002-226721, A

However, when the conductive composition described in Patent Document 1 is applied to a chemically amplified resist, the resist layer may be thinned.
An object of the present invention is to provide a conductive polymer and a conductive composition capable of forming a conductive film with less reduction of the resist layer.

As a result of earnest studies, the present inventor has paid attention to the fact that the acidic group portion of the conductive polymer having an acidic group is susceptible to hydrolysis and the like and is unstable, and the acidic group may be eliminated. Further, it was found that the conductive polymer having an acidic group contains a decomposed product of an oxidizing agent used during polymerization (for example, sulfate ion), nitric acid, and the like. Then, acidic groups desorbed from these conductive polymers, decomposition products of oxidizing agents, low-molecular-weight acidic substances such as nitric acid migrate to the resist layer, and the resist layer in the unexposed area is dissolved during development. , And found that the film thickness of the resist layer is reduced. Therefore, the inventors have found that reducing the low molecular weight acidic substance in the conductive polymer having an acidic group can suppress the film loss of the resist layer, and completed the present invention.

That is, the present invention has the following aspects.
[1] A conductive polymer having an acidic group,
A conductive polymer in which the content of an acidic substance having a molecular weight of 100 or less is 10000 mass ppm or less.
[2] The conductive polymer according to [1], which is used for preventing electrostatic charge during charged particle beam drawing.
[3] A conductive composition containing the conductive polymer of [1] or [2] and a solvent.

According to the present invention, it is possible to provide a conductive polymer and a conductive composition capable of forming a conductive film with less reduction of the resist layer.

Hereinafter, the present invention will be described in detail. The following embodiments are merely examples for explaining the present invention, and the present invention is not intended to be limited only to the embodiments. The present invention can be implemented in various modes without departing from the spirit thereof.

In the present invention, “conductive” means having a surface resistance value of 1×10 ¹¹ Ω/□ or less. The surface resistance value is obtained from the potential difference between the electrodes when a constant current is applied.
In addition, in the present invention, the "acidic substance having a molecular weight of 100 or less" is a substance having a negative charge and a molecular weight of 100 or less. Specifically, the acidic groups desorbed from the conductive polymer (for example, free acidic groups derived from carboxylic acid, sulfonic acid, sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, etc.) and the oxidizing agent used in the production of the conductive polymer Examples thereof include decomposition products (for example, sulfate ions), components by-produced during the reaction (for example, nitric acid), and the like. In addition, in the following specification, "an acidic substance having a molecular weight of 100 or less" is also referred to as "an acidic substance (a) having a molecular weight of 100 or less" or simply "an acidic substance (a)".
In addition, in the present specification, “solubility” refers to 10 g (liquid temperature: 25) of mere water, water containing at least one of a base and a basic salt, water containing an acid, and a mixture of water and a water-soluble organic solvent. (°C) means that 0.1 g or more is uniformly dissolved. Further, “water-soluble” means the solubility in water with respect to the above-mentioned solubility.
Further, in the present specification, the “terminal” of the “terminal hydrophobic group” means a site other than the repeating unit constituting the polymer.
Moreover, in this specification, a "mass average molecular weight" is a mass average molecular weight (as sodium polystyrene sulfonate conversion) measured by gel permeation chromatography (GPC).

[Conductive polymer]
The conductive polymer (A) of the present invention has an acidic group. If the conductive polymer (A) has an acidic group, the water solubility will increase. As a result, the coating property of the conductive composition containing the conductive polymer (A) is enhanced, and a coating film having a uniform thickness is 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 as long as it has the effects of the present invention, and it is known. The conductive polymer of can be used. For example, JP-A-61-197633, JP-A-63-39916, JP-A-1-301714, JP-A-5-504153, JP-A-5-503953, and JP-A-4-32848. Publications, JP-A-4-328181, JP-A-6-145386, JP-A-6-56987, JP-A-5-226238, JP-A-5-178989, 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, and JP-A-7-48436. The conductive polymers and the like disclosed in JP-A-4-268331 and JP-A-2014-65898 are preferable from the viewpoint of solubility.

Specific examples of the conductive polymer (A) include phenylene vinylene, vinylene, thienylene, in which the α-position or the β-position is substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group, Examples of the π-conjugated conductive polymer include, as a repeating unit, at least one selected from the group consisting of pyrrolylene, phenylene, iminophenylene, isothianaphthene, furylene, and carbazolylene.
Further, when the π-conjugated conductive polymer contains at least one repeating unit selected from the group consisting of iminophenylene and galvazolylene, on the nitrogen atom of the repeating unit, a sulfonic acid group, and a carboxy group The nitrogen atom having an alkyl group having at least one group selected from the group consisting of or 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. The conductive polymer having the above may be mentioned.
Among these, from the viewpoint of conductivity and solubility, thienylene, pyrrolylene, iminophenylene, phenylenevinylene, carbazolylene in which the β-position is substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group, and A conductive polymer having at least one selected from the group consisting of isothianaphthenes as a monomer unit (unit) is preferably used.

The conductive polymer (A) contains one or more monomer units selected from the group consisting of units represented by the following general formulas (1) to (4), from the viewpoint of exhibiting high conductivity and solubility. A conductive polymer contained in 20 to 100 mol% in all units (100 mol%) constituting the conductive polymer is preferable.

In formulas (1) to (4), X represents a sulfur atom or a nitrogen atom, and R ^{1 to} R ¹⁵ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, or a carbon atom. the number 1 to 24 linear or branched alkoxy group having an acidic group, hydroxy group, a nitro group, a halogen atom (-F, -Cl, -Br or _{^{I), - N (R 16}} ) 2, -NHCOR 16, It represents -SR ¹⁶ , -OCOR ¹⁶ , -COOR ¹⁶ , -COR ¹⁶ , -CHO, or -CN. R 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, at least one of R ¹ and R ^{2 in} the general formula (1), at least one of R ^{3 to} R ^{6 in} the general formula (2), and R ^{7 to} R ^{10 in} the general formula (3). At least one of them and at least one of R ^{11 to} R ^{15 in} the general formula (4) is an acidic group or a salt thereof.

Here, the "acidic group" means a sulfonic acid group (sulfo group) or a carboxylic acid group (carboxy group).
Sulfonic acid group may be contained in the form of acid _(-SO 3 H), ion states ^- may be included in (-SO _3). Furthermore, the sulfonic acid group, substituent having a sulfonic acid group ^(-R 17 _SO 3 H) are also included.
On the other hand, carboxylic acid groups, may be included in the form of an acid (-COOH), an ionic state ^- may be included in (-COO). In addition, the carboxylic acid group, a substituent having a carboxylic acid group ^(-R 17 COOH) are also included.
R ¹⁷ is 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. Represent

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

The conductive polymer (A) preferably has a unit represented by the above general formula (4) from the viewpoint of exhibiting high conductivity. Among them, the following general formula is particularly preferable from the viewpoint of excellent solubility. It is more preferable to have a monomer unit represented by (5).

In formula (5), R ^{18 to} R ²¹ are each independently 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, It represents an acidic group, a hydroxy group, a nitro group, or a halogen atom (-F, -Cl, -Br or I). Further, at least one of R ^{18 to} R ²¹ is an acidic group or a salt thereof.

As the unit represented by the general formula (5), any one of R ^{18 to} R ²¹ is a straight-chain or branched-chain alkoxy group having 1 to 4 carbon atoms in terms of easy production, It is preferable that any one of the other is a sulfonic acid group and the rest is hydrogen.

From the viewpoint that the conductive polymer (A) is excellent in solubility in water and an organic solvent regardless of pH, among all units (100 mol%) constituting the conductive polymer (A), the general formula (5) is used. The content of the unit represented by is preferably 10 to 100 mol %, more preferably 50 to 100 mol %, and particularly preferably 100 mol %.
In addition, the conductive polymer (A) preferably contains 10 or more units represented by the general formula (5) in one molecule from the viewpoint of excellent conductivity.

Further, in the conductive polymer (A), the number of aromatic rings to which an acidic group is bonded is preferably 50% or more, and 70% with respect to the total number of aromatic rings in the polymer, from the viewpoint of further improving the solubility. The above is more preferable, 80% or more is further preferable, 90% or more is particularly preferable, and 100% is the most preferable.
The number of aromatic rings to which an acidic group is bonded with respect to the total number of aromatic rings in the polymer refers to a value calculated from the charging ratio of monomers at the time of producing the conductive polymer (A).

Further, in the conductive polymer (A), the substituent other than the acidic group on the aromatic ring of the monomer unit is preferably an electron donating group from the viewpoint of imparting reactivity to the monomer, specifically, having 1 to 1 carbon atoms. An alkyl group having 24, an alkoxy group having 1 to 24 carbon atoms, a halogen group (-F, -Cl, -Br or I) and the like are preferable, and among these, an alkoxy group having 1 to 24 carbon atoms from the viewpoint of electron donating property. Is most preferred.

Furthermore, the conductive polymer (A) is a substituted or unsubstituted aniline, thiophene, or a structural unit other than the unit represented by the general formula (5) as long as it does not affect the solubility, conductivity and properties. It may contain at least one unit selected from the group consisting of pyrrole, phenylene, vinylene, a divalent unsaturated group and a divalent saturated group.

The conductive polymer (A) is preferably a compound having a structure represented by the following general formula (6) from the viewpoint of exhibiting high conductivity and solubility, and is represented by the following general formula (6). Among the compounds having the structure shown below, poly(2-sulfo-5-methoxy-1,4-iminophenylene) is particularly preferable.

In formula (6), R ^{22 to} R ³⁷ are each independently 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, It represents an acidic group, a hydroxy group, a nitro group, or a halogen atom (-F, -Cl, -Br or I). Moreover, at least one of R ^{22 to} R ³⁷ is an acidic group or a salt thereof. Further, n represents the degree of polymerization. In the present invention, n is preferably an integer of 5 to 2500.

It is desirable that at least a part of the acidic group contained in the conductive polymer (A) is a free acid type from the viewpoint of improving conductivity.

The mass average molecular weight of the conductive polymer (A) is preferably 1000 to 1,000,000, more preferably 1500 to 800,000, and more preferably 2000 in terms of conductivity, solubility and film-forming property in terms of sodium polystyrene sulfonate of GPC. ˜500,000 is more preferable, and 2,000 to 100,000 is particularly preferable. When the mass average molecular weight of the conductive polymer (A) is less than 1000, the solubility is excellent, but the conductivity and the film forming property may be insufficient. On the other hand, when the mass average molecular weight exceeds 1,000,000, the conductivity may be excellent, but the solubility may be insufficient.
Here, the "film forming property" refers to the property of forming a uniform film without cissing and the like, and can be evaluated by a method such as spin coating on glass.

The content of the acidic substance (a) having a molecular weight of 100 or less in the conductive polymer (A) is 10,000 mass ppm or less based on the total mass of the conductive polymer (A). When the content of the acidic substance (a) is 10000 ppm by mass or less, when the conductive composition containing the conductive polymer (A) is applied to the surface of the resist layer to form a conductive film, the conductive film is removed from the resist. The migration of the acidic substance (a) to the layer is reduced, and the film loss of the resist layer can be suppressed. The content of the acidic substance (a) is preferably 8000 mass ppm or less, more preferably 5000 mass ppm or less, further preferably 1000 mass ppm or less, and 700 mass ppm or less with respect to the total mass of the conductive polymer (A). Is particularly preferable.
The smaller the content of the acidic substance (a) in the conductive polymer (A), the better, and the lower limit value is preferably 0 mass ppm with respect to the total mass of the conductive polymer (A).

The content of the acidic substance (a) can be measured by ion chromatography. Specifically, it can be measured as follows.
First, sodium carbonate is added to water so that the solid content concentration is 1.8 mmol/L to prepare an aqueous sodium carbonate solution. Similarly, sodium hydrogencarbonate is added to water so that the solid content concentration becomes 1.7 mmol/L to prepare an aqueous sodium hydrogencarbonate solution. The obtained sodium carbonate aqueous solution and the sodium hydrogen carbonate aqueous solution are mixed at a mass ratio of 1:1 to obtain an eluent. A conductive polymer (A) is added to and dissolved in the obtained eluent to prepare a test solution. At this time, it is difficult to obtain an accurate quantitative value when the concentration of the acidic substance (a) in the test solution is too high or too low, so that an appropriate concentration (for example, about 10 to 50000 mass ppm) should be obtained. The conductive polymer (A) is dissolved in water in advance, and this is added to the eluent to prepare a test solution.
With respect to the obtained test solution, the concentration of the acidic substance (a) is measured using an ion chromatograph to obtain a chromatogram. The area or height of the peak corresponding to the acidic substance (a) on this chromatogram is read, and the content of the acidic substance (a) in the conductive polymer (A) is obtained from the calibration curve prepared in advance. ..

In order to make the content of the acidic substance (a) in the conductive polymer (A) 10000 mass ppm or less, for example, the following polymerization step and purification step may be performed to produce the conductive polymer (A). Good.
Below, an example of the manufacturing method of electroconductive polymer (A) is demonstrated.

<Method for producing conductive polymer (A)>
The method for producing the conductive polymer (A) of the present embodiment includes a step of polymerizing a raw material monomer of the conductive polymer (A) in the presence of a polymerization solvent and an oxidizing agent (polymerization step), and a reaction obtained in the polymerization step. And a step of purifying the product (purification step).

(Polymerization process)
The polymerization step is a step of polymerizing the raw material monomer of the conductive polymer (A) in the presence of a polymerization solvent and an oxidizing agent.
Specific examples of the raw material monomer include a polymerizable monomer from which the above-mentioned monomer unit is derived, and specifically, acidic group-substituted aniline, its alkali metal salt, alkaline earth metal salt, ammonium salt and substituted ammonium. At least one selected from the group consisting of salts can be mentioned.
Examples of the acidic group-substituted aniline include sulfonic acid group-substituted aniline having a sulfonic acid group as an acidic group.
Typical examples of the sulfo group-substituted aniline are aminobenzenesulfonic acids, specifically, o-, m-, p-aminobenzenesulfonic acid, aniline-2,6-disulfonic acid, aniline-2,5-. Disulfonic acid, aniline-3,5-disulfonic acid, aniline-2,4-disulfonic acid, aniline-3,4-disulfonic acid and the like are preferably used.

Examples of sulfone group-substituted anilines other than aminobenzenesulfonic acids include methylaminobenzenesulfonic acid, ethylaminobenzenesulfonic acid, n-propylaminobenzenesulfonic acid, iso-propylaminobenzenesulfonic acid, n-butylaminobenzenesulfonic acid, Alkyl group-substituted aminobenzene sulfonic acids such as sec-butylaminobenzenesulfonic acid and t-butylaminobenzenesulfonic acid; Alkoxy group-substituted aminobenzene sulfones such as methoxyaminobenzenesulfonic acid, ethoxyaminobenzenesulfonic acid and propoxyaminobenzenesulfonic acid Acids; hydroxy group-substituted aminobenzene sulfonic acids; nitro group-substituted aminobenzene sulfonic acids; halogen-substituted aminobenzene sulfonic acids such as fluoroaminobenzene sulfonic acid, chloroaminobenzene sulfonic acid and bromoaminobenzene sulfonic acid.
Among these, alkyl group-substituted aminobenzene sulfonic acids, alkoxy group-substituted aminobenzene sulfonic acids, hydroxy group-substituted aminobenzene sulfonic acids, or a conductive polymer (A) having particularly excellent conductivity and solubility is obtained. Halogen-substituted aminobenzene sulfonic acids are preferable, and alkoxy group-substituted aminobenzene sulfonic acids, their alkali metal salts, ammonium salts and substituted ammonium salts are particularly preferable in terms of easy production.
Any one of these sulfonic acid group-substituted anilines may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.

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

The oxidizing agent is not limited as long as it has a standard electrode potential of 0.6 V or more. For example, peroxodisulfates such as peroxodisulfate, ammonium peroxodisulfate, sodium peroxodisulfate, and potassium peroxodisulfate; Examples include hydrogen peroxide.
Any one of these oxidizing agents may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.

In the polymerization step, the raw material monomer may be polymerized in the presence of a basic reaction aid in addition to the polymerization solvent and the oxidizing agent.
Examples of the basic reaction aid include inorganic bases such as sodium hydroxide, potassium hydroxide and lithium hydroxide; ammonia; methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylmethylamine, ethyldimethylamine, diethyl. Aliphatic amines such as methylamine; cyclic saturated amines; 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 preferable, and cyclic unsaturated amines are more preferable.
Any one of these basic reaction aids may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.

Examples of the polymerization method include, for example, a method of dropping the raw material monomer solution into the oxidizing agent solution, a method of dropping the oxidizing agent solution into the raw material monomer solution, and a method of dropping the raw material monomer solution and the oxidizing agent solution into the reaction vessel at the same time. And so on. The raw material monomer solution may contain a basic reaction aid, if necessary.
As the solvent of the oxidant solution and the raw material monomer solution, the above-mentioned polymerization solvent can be used.

The reaction temperature of the polymerization reaction is preferably 50°C or lower, more preferably -15 to 30°C, still more preferably -10 to 20°C. When the reaction temperature of the polymerization reaction is 50° C. or lower, particularly 30° C. or lower, it is possible to suppress the progress of side reactions and the decrease in conductivity due to the change in the redox structure of the main chain of the conductive polymer (A) produced. When the reaction temperature of the polymerization reaction is −15° C. or higher, a sufficient reaction rate can be maintained and the reaction time can be shortened.

By the polymerization step, the conductive polymer (A) as a 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 with a filter such as a centrifugal separator to obtain the reaction product.

The reaction products include unreacted raw material monomers, oligomers accompanying side reactions, acidic substances (a), basic substances (basic reaction aids, ammonium ions which are decomposition products of oxidizing agents, etc.) It may contain low molecular weight components. These low molecular weight components are impurities and become a factor that hinders conductivity. In particular, the acidic substance (a) also causes a reduction in the film thickness of the resist layer.
Therefore, after the polymerization step, the reaction product is purified to obtain the conductive polymer (A).

(Purification process)
The purification step is a step of purifying the reaction product obtained in the polymerization step.
As a method for purifying the reaction product, any method such as a washing method using a washing solvent, a membrane filtration method, an ion exchange method, removal of impurities by heat treatment, and neutralization precipitation can be used. Among these, the washing method and the ion exchange method are effective from the viewpoint that the conductive polymer (A) having high purity can be easily obtained. Among them, the washing method is particularly preferable from the viewpoint of efficiently removing the raw material monomer, oligomer, and acidic substance (a). Further, the cleaning method and the ion exchange method may be used in combination.

The washing solvent used in the washing method is not particularly limited as long as it is a solvent that dissolves the low molecular weight component and hardly dissolves the conductive polymer (A), but from the viewpoint of excellent solubility of the acidic substance (a), the dissolution parameter It is preferable to use the washing solvent (α) having a (SP value) of 20 to 40 MPa ^1/2 .
When the SP value of the washing solvent (α) is 20 MPa ^1/2 or more, the acidic substance (a) can be sufficiently extracted. The effect of extracting the acidic substance (a) cannot be obtained even if the SP value is too high. When the SP value is 40 MPa ^1/2 or less, the acidic substance (a) can be efficiently extracted.
The SP value of the washing solvent (α) can be determined, for example, by the method described in “Polymer Handbook”, 4th edition, VII-675 to VII-711, and specifically, a table 1 (page VII-683) and Tables 7 to 8 (pages VII-688 to VII-711).
Further, the SP value when a mixed solvent is used as the washing solvent can be obtained by a known method. For example, the sum of the products of the SP value and the volume fraction of each solvent can be obtained by the following mathematical formula.

In the formula, SP _n is the SP value of each solvent, V _n is the volume of each solvent, and V _total is the total volume of the solvent after mixing.

As the washing solvent (α), methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol, 3-butanol, t-butanol, 1-pentanol, 3-methyl-1-butanol, Alcohols such as 2-pentanol, n-hexanol, 4-methyl-2-pentanol, 2-ethylbutynol, benzyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether. , Methoxymethoxyethanol, propylene glycol monoethyl ether, glyceryl monoacetate and other polyhydric alcohol derivatives; acetone; acetonitrile; N,N-dimethylformamide; N-methylpyrrolidone; dimethylsulfoxide and the like. Among these, methanol, ethanol, isopropanol, acetone, and acetonitrile are effective.

When a washing method is used in the purification step, the reaction product is washed with a washing solvent until the content of the acidic substance (a) becomes 10,000 mass ppm or less based on the total mass of the conductive polymer (A). . For washing the reaction product, the content of the acidic substance (a) is preferably 8000 mass ppm or less, more preferably 5000 mass ppm or less, and further preferably 1000 mass ppm with respect to the total mass of the conductive polymer (A). Hereafter, it is particularly preferable to carry out until the amount becomes 700 mass ppm or less.

The reaction product after washing, that is, the conductive polymer (A) after washing is dried to obtain a solid conductive polymer (A) in which raw material monomers, oligomers and acidic substances (a) are sufficiently removed. ..
The conductive polymer (A) after washing may be further purified by an ion exchange method, if necessary. By using the ion exchange method, it is possible to effectively remove the basic substance and the like existing in a state of forming a salt with the acidic group of the conductive polymer (A).
Examples of the ion exchange method include column type and batch type treatments using an ion exchange resin such as a cation exchange resin and an anion exchange resin; and an electrodialysis method.
When the reaction product is purified by the ion exchange method, it is preferable that the reaction product is dissolved in an aqueous medium so as to have a desired solid content concentration, and as a polymer solution, contacted with the ion exchange resin.
Examples of the aqueous medium include the same as the solvent (B) described later.
The concentration of the conductive polymer (A) in the polymer solution is preferably 0.1 to 20% by mass, and more preferably 0.1 to 10% by mass from the viewpoint of industrial property and purification efficiency.

In the case of the ion exchange method using the ion exchange resin, the amount of the sample solution with respect to the ion exchange resin is preferably 10 times the volume of the ion exchange resin in the case of a polymer solution having a solid content concentration of 5% by mass. More preferably, the volume is doubled. Examples of the cation exchange resin include "Amberlite IR-120B" manufactured by Organo Corporation. Examples of the anion exchange resin include "Amberlite IRA410" manufactured by Organo Corporation.

The conductive polymer (A) after the ion exchange treatment is in a state of being dissolved in an aqueous medium. Therefore, the solid conductive polymer (A) can be obtained by removing all the aqueous medium with an evaporator or the like, but the conductive polymer (A) is used in the production of the conductive composition in a state of being dissolved in the aqueous medium. Good.

<Effect>
As described above, when a low molecular weight acidic substance migrates from the conductive film to the resist layer side when the conductive film is formed on the resist layer, the resist layer in the unexposed portion is dissolved during development, and the resist A layer loss may occur.
However, with the conductive polymer (A) of the present invention, since the content of the acidic substance having a molecular weight of 100 or less is sufficiently reduced, it is possible to form a conductive film in which the acidic substance does not easily migrate to the resist layer.
Therefore, particularly in the pattern formation method using a charged particle beam using a chemically amplified resist, the migration of an acidic substance or the like from the conductive film to the resist layer side is suppressed, and the influence of the resist layer thickness reduction or the like can be suppressed.

[Conductive composition]
The conductive composition of the present invention contains the above-mentioned conductive polymer (A) of the present invention and a solvent (B). The conductive composition may contain a basic compound (C), a surfactant (D) and the like, if necessary.

<Conductive polymer (A)>
The conductive polymer (A) is the above-mentioned conductive polymer (A) of the present invention, and the description thereof is omitted.
The content of the conductive polymer (A) is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and 0.5 to 2% by mass with respect to the total mass of the conductive composition. Is more preferable.
In addition, the content of the conductive polymer (A) is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and 95 to 100% by mass based on the total mass of the solid content of the conductive composition. More preferable. The solid content of the conductive composition is the residue obtained by removing the solvent (B) from the conductive composition.
When the content of the conductive polymer (A) is within the above range, the coatability of the conductive composition and the conductivity of the coating film formed from the conductive composition are excellent.

<Solvent (B)>
The solvent (B) is not particularly limited as long as it has the effect of the present invention, as long as it is a solvent capable of dissolving the conductive polymer (A), the basic compound (C) and the surfactant (D) described below. Although not removed, water, an organic solvent, or a mixed solvent of water and an organic solvent can be used.
Examples of water include tap water, ion-exchanged water, pure water, distilled water and the like.
Examples of the organic solvent include organic solvents among the polymerization solvents exemplified above in the description of the method for producing the conductive polymer (A).
When a mixed solvent of water and an organic solvent is used as the solvent (B), their mass ratio (water/organic solvent) is preferably 1/100 to 100/1, and is 2/100 to 100/2. More preferably.

It is preferable that the solvent (B) does not substantially contain the acidic substance (a) from the viewpoint of further suppressing the film loss of the resist layer.
Here, “not substantially containing” means that the content of the acidic substance (a) is 100 mass ppb or less with respect to the total mass of the solvent (B).

The content of the solvent (B) is preferably 1 to 99.9% by mass, more preferably 10 to 98% by mass, and further preferably 50 to 98% by mass, based on the total mass of the conductive composition. When the content of the solvent (B) is within the above range, the coatability is further improved.
When the conductive polymer (A) is used in a state of being dissolved in an aqueous medium by purification or the like (hereinafter, the conductive polymer (A) in this state is also referred to as “conductive polymer solution”), the conductive polymer is used. The aqueous medium derived from the solution is also included in the content of the solvent (B) in the conductive composition.

<Basic compound (C)>
The conductive composition may contain a basic compound (C).
It is considered that if the conductive composition contains the basic compound (C), the stability of the conductive polymer (A) can be increased.

The basic compound (C) is not particularly limited as long as it is a basic compound, but for example, the following quaternary ammonium salt (c-1), basic compound (c-2), basic compound (c -3) and the like.
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 3 or more carbon atoms.
Basic compound (c-2): A basic compound having one or more nitrogen atoms (provided that the quaternary ammonium salt (c-1) and the basic compound (c-3) are excluded).
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.

In the quaternary ammonium compound (c-1), the nitrogen atom to which the four substituents are bonded is the nitrogen atom of the 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, benzyltrimethylammonium hydroxide and the like.

Examples of the basic compound (c-2) include ammonia, pyridine, triethylamine, 4-dimethylaminopyridine, 4-dimethylaminomethylpyridine, 3,4-bis(dimethylamino)pyridine and 1,5-diazabicyclo[4]. .3.0]-5-nonene (DBN), 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), and derivatives thereof.

In the basic compound (c-3), examples of the basic group include a basic group defined by Arrhenius base, Bronsted base, Lewis base and the like. Specific examples include ammonia. The hydroxy group may be in the form of -OH or may be protected by a protecting group. Examples of the protecting group include an acetyl group; a silyl group such as a trimethylsilyl group and a t-butyldimethylsilyl group; an acetal-type protecting group such as a methoxymethyl group, an ethoxymethyl group, and a methoxyethoxymethyl group; a benzoyl group; an alkoxide group. Can be mentioned.
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, N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid and the like can be mentioned. ..

Any one of these basic compounds may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.
Among these, at least one selected from the group consisting of a quaternary ammonium salt (c-1) and a basic compound (c-2) from the viewpoint of easily forming a salt with the acidic group of the conductive polymer (A). It is preferable to include.

The content of the basic compound (C) is from 0. 0 to 1 mol of the unit having an acidic group among the units constituting the conductive polymer (A) from the viewpoint of further improving the coating property of the conductive composition. 1-1 mol equivalent is preferable, and 0.1-0.9 mol equivalent is more preferable. Further, 0.25 to 0.85 mol equivalent is particularly preferable, from the viewpoint of excellent retention of performance as a conductive film and making the acidic group in the conductive polymer (A) more stable.

<Surfactant (D)>
The conductive composition may include a surfactant (D).
When the conductive composition contains the surfactant (D), the coatability when the conductive composition is applied to the surface of the substrate or the resist layer is improved.
Examples of the surfactant include anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants. Any one of these surfactants may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.

Examples of the anionic surfactant include sodium octanoate, sodium decanoate, sodium laurate, sodium myristate, sodium palmitate, sodium stearate, perfluorononanoic acid, sodium N-lauroylsarcosine, sodium cocoyl glutamate, and alpha. Examples thereof include sulfo fatty acid methyl ester salt, 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.

Examples of the cationic surfactant include tetramethylammonium chloride, tetramethylammonium hydroxide, tetrabutylammonium chloride, dodecyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyl chloride. Trimethyl ammonium, tetradecyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, alkyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, benzyl trimethyl ammonium chloride, benzyl triethyl ammonium chloride, benzalkonium chloride, benz bromide Ruconium, benzethonium chloride, dialkyldimethylammonium chloride, didecyldimethylammonium chloride, distearyldimethylammonium chloride, monomethylamine hydrochloride, dimethylamine hydrochloride, trimethylamine hydrochloride, butylpyridinium chloride, dodecylpyridinium chloride, cetylpyridinium chloride, etc. Can be mentioned.

Examples of the amphoteric surfactant include lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, dodecylaminomethyldimethylsulfopropylbetaine, octadecylaminomethyldimethylsulfopropylbetaine, cocamidopropylbetaine, cocamidopropylhydroxysultaine, 2 -Alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, sodium lauroylglutamate, potassium lauroylglutamate, lauroylmethyl-β-alanine, lauryldimethylamine-N-oxide, oleyldimethylamine N-oxide and the like can be mentioned. .

As the nonionic surfactant, for example, glycerin laurate, glyceryl monostearate, sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkyl ether, pentaethylene glycol monododecyl ether, octaethylene glycol monododecyl ether, poly Oxyethylene alkyl phenyl ether, octylphenol ethoxylate, nonylphenol ethoxylate, polyoxyethylene polyoxypropylene glycol, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene hexitane fatty acid ester, sorbitan fatty acid ester polyethylene glycol, lauric acid diethanolamide, oleic acid Examples include diethanolamide, stearic acid diethanolamide, octyl glucoside, decyl glucoside, lauryl glucoside, cetanol, stearyl alcohol, and oleyl alcohol.

As the nonionic surfactant, a water-soluble polymer having a nitrogen-containing functional group and a terminal hydrophobic group other than the above may be used. Unlike conventional surfactants, this water-soluble polymer has surface activity due to the main chain portion (hydrophilic portion) that has a nitrogen-containing functional group and the hydrophobic group portion at the end, and it has the effect of improving coatability. Is high. Therefore, excellent coating properties can be imparted to the conductive composition without using any other surfactant. In addition, since this water-soluble polymer does not contain an acid or a base and a by-product hardly occurs due to hydrolysis, the adverse effect on the resist layer and the like is particularly small.

As the nitrogen-containing functional group, an amide group is preferable 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, and an aralkylamino group. , Arylamino groups and the like. Among these, an alkylthio group, an aralkylthio group, and an arylthio group are preferable.
3-100 are preferable, as for carbon number of a terminal hydrophobic group, 5-50 are more preferable, and 7-30 are especially preferable.
The number of terminal hydrophobic groups in the water-soluble polymer is not particularly limited. Further, when two or more terminal hydrophobic groups are contained in the same molecule, the terminal hydrophobic groups may be of the same type or of different types.

The water-soluble polymer is mainly 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 having no nitrogen-containing functional group (other vinyl monomer). A compound having a chain structure and having a hydrophobic group at a site other than the repeating units constituting the polymer is preferable.
Examples of vinyl monomers having a nitrogen-containing functional group include acrylamide and its derivatives, and heterocyclic monomers having a nitrogen-containing functional group, and among them, those having an amide bond are preferable. Specifically, acrylamide, N,N-dimethylacrylamide, N-isopropylacrylamide, N,N-diethylacrylamide, N,N-dimethylaminopropylacrylamide, t-butylacrylamide, diacetone acrylamide, N,N'-methylene. Examples thereof include bisacrylamide, N-vinyl-N-methylacrylamide, N-vinylpyrrolidone and N-vinylcaprolactam. Among these, acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam and the like are particularly preferable from the viewpoint of solubility.
The other vinyl monomer is not particularly limited as long as it can copolymerize a vinyl monomer having a nitrogen-containing functional group, and examples thereof include styrene, acrylic acid, vinyl acetate, and long-chain α-olefin.

The method of introducing the terminal hydrophobic group into the water-soluble polymer is not particularly limited, but it is usually convenient and preferable to select by introducing a chain transfer agent during vinyl polymerization. In this case, as the chain transfer agent, a group containing a hydrophobic group such as an alkyl group, an aralkyl group, an aryl group, an alkylthio group, an aralkylthio group and an arylthio group is introduced as long as it is introduced into the terminal of the obtained polymer. There is no particular limitation. For example, when obtaining a water-soluble polymer having an alkylthio group, an aralkylthio group, or an arylthio group as a terminal hydrophobic group, a chain transfer agent having a hydrophobic group corresponding to these terminal hydrophobic groups, specifically, a thiol It is preferable to carry out vinyl polymerization using disulfide, disulfide or thioether.

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) of the main chain portion is preferably 2 to 1000, more preferably 3 to 1000, and particularly preferably 5 to 10 in one molecule. 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 of the main chain part in the water-soluble polymer to the terminal hydrophobic group part (eg, part such as alkyl group, aralkyl group, aryl group, alkylthio group, aralkylthio group, arylthio group) (mass average of main chain part) The ratio (molecular weight/mass average molecular weight of the terminal hydrophobic group portion) is preferably 0.3 to 170.

As the surfactant (D), among the above, a nonionic surfactant is preferable because it has little influence on the resist layer.

The content of the surfactant (D) is preferably 5 to 80 parts by mass, when the total amount of the conductive polymer (A), the basic compound (C) and the surfactant (D) is 100 parts by mass, 10 to 70 parts by mass is more preferable, and 10 to 60 parts by mass is further preferable. When the content of the surfactant (D) is within the above range, the coating property of the conductive composition on the resist layer is further improved.

<Arbitrary ingredients>
The conductive composition may contain a component (optional component) other than the conductive polymer (A), the solvent (B), the basic compound (C) and the surfactant (D), if necessary.
Examples of the optional component include a high molecular compound (excluding the conductive polymer (A), the basic compound (C) and the surfactant (D)), an additive and the like.

Examples of the polymer compound include polyvinyl alcohol derivatives such as polyvinyl formal and polyvinyl butyral, polyacrylamide, poly(N-t-butylacrylamide), polyacrylamides such as polyacrylamidemethylpropanesulfonic acid, polyvinylpyrrolidone and poly(vinylpyrrolidone). Acrylic acids, water-soluble alkyd resin, water-soluble melamine resin, water-soluble urea resin, water-soluble phenol resin, water-soluble epoxy resin, water-soluble polybutadiene resin, water-soluble acrylic resin, water-soluble urethane resin, water-soluble acrylic styrene copolymer Examples thereof include 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 the additives include pigments, defoaming agents, ultraviolet absorbers, antioxidants, heat resistance improvers, leveling agents, anti-sagging agents, matting agents and preservatives.

<Method for producing conductive composition>
The conductive composition is a mixture of the conductive polymer (A) of the present invention, a solvent (B), and, if necessary, one or more of a basic compound (C), a surfactant (D) and optional components. It is obtained by doing.
Since the conductive polymer (A) after cleaning produced by the above-described method for producing the conductive polymer (A) is in a solid state, the solid state conductive polymer (A) and the solvent (B) are mixed in advance. Then, a conductive polymer solution may be prepared, and the obtained conductive polymer solution may be used as a conductive composition. Further, if necessary, one or more of the basic compound (C), the surfactant (D) and an optional component may be added to the conductive polymer solution to give a conductive composition.
When the conductive polymer (A) further purified by the ion exchange method after washing is used, the conductive polymer (A) after the ion exchange treatment is obtained in the state of the conductive polymer solution as described above. Therefore, this conductive polymer solution may be used as it is as the conductive composition, or may be further diluted with the solvent (B). Further, if necessary, one or more of the basic compound (C), the surfactant (D) and an optional component may be added to the conductive polymer solution to give a conductive composition.

<Effect>
Since the conductive composition of the present invention contains the conductive polymer (A) in which the content of the acidic substance having a molecular weight of 100 or less is sufficiently reduced, it is possible to form a conductive film in which the acidic substance does not easily migrate to the resist layer. ..
Therefore, particularly in the pattern formation method using a charged particle beam using a chemically amplified resist, the migration of an acidic substance or the like from the conductive film to the resist layer side is suppressed, and the influence of the resist layer thickness reduction or the like can be suppressed.

<Use>
The conductive composition of the present invention is suitable for preventing electrostatic charge during charged particle beam drawing. Specifically, the conductive composition of the present invention is applied to the surface of a resist layer by a pattern formation method using a charged particle beam 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 and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples do not limit the scope of the present invention.
Various measuring/evaluating methods in Examples and Comparative Examples are as follows.

[Measurement and evaluation method]
<Measurement of content of acidic substance (a)>
A test solution was prepared by adding the following eluents to the conductive polymer (A). Regarding the obtained test solution, the concentration of the acidic substance (a) was measured under the following ion chromatograph (IC) measurement conditions to obtain a chromatogram. The area or height of the peak corresponding to the acidic substance (a) on the obtained chromatogram is read, and from the calibration curve prepared in advance, the acidic substance (a) of the total mass of the conductive polymer (A) is measured. The content was determined.
<<IC measurement conditions>>
・Device: Ion Chromatograph IC-2010 (manufactured by Tosoh Corporation)
-Column: TSKguard Column Super IC-Anion HS C-No W00052
Eluent: mixed solution of 1.8 mmol/L sodium carbonate aqueous solution and sodium hydrogen carbonate having a solid content concentration of 1.7 mmol/L (mass ratio 1:1)
・Flow rate: 1.5 mL/min ・Measuring temperature: 40°C
・Sample injection volume: 30 μL

<Evaluation of conductivity>
After 2.0 mL of the conductive composition was dropped on a glass substrate as a substrate, and a coating film was formed by spin coating with a spin coater at 2000 rpm×60 seconds so as to cover the entire substrate surface. A heat treatment was performed on a hot plate at 80° C. for 2 minutes to form a conductive film having a film thickness of about 30 nm on the base material to obtain a conductor.
The surface resistance value [Ω/□] of the conductive film was measured by a two-terminal method (distance between electrodes 20 mm) using Hiresta UX-MCP-HT800 (manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

<Evaluation by film reduction test>
(Measurement of film loss)
A chemically amplified electron beam resist (hereinafter, abbreviated as “resist”) was used, and the film reduction amount of the resist layer was measured by the following procedures (1A) to (8A).
(1A) Formation of resist layer: 0.2 μm of resist was spin-coated on a 4-inch silicon wafer as a base material by a spin coater under the conditions of 2000 rpm×60 seconds, and then prebaked at 130° C. for 90 seconds on a hot plate. Then, the solvent was removed and a resist layer was formed on the substrate.
(2A) Measurement of resist layer thickness 1: Part of the resist layer formed on the base material is peeled off, and the surface of the base material is used as a reference position, and a stylus profiler P-16+, KLA-Tencor is used. The film thickness a [nm] of the initial resist layer was measured using Corporation.
(3A) Formation of conductive film: 2 mL of the conductive composition was dropped on the resist layer, spin-coated with a spin coater under the conditions of 2000 rpm×60 seconds so as to cover the entire surface of the resist layer, and then applied to a hot plate. Then, heat treatment was performed at 80° C. for 2 minutes to form a conductive film having a film thickness of about 30 nm on the resist layer.
(4A) Baking treatment: The base material on which the conductive film and the resist layer are laminated is heated at 120° C. for 20 minutes in a hot plate in an air atmosphere, and the base material in this state is kept in air at room temperature (25° C.) for 90 minutes. Let stand for a second.
(5A) Washing with water: After washing the conductive film with 20 mL of water, the spin coater was rotated at 2000 rpm for 60 seconds to remove water on the surface of the resist layer.
(6A) Development: 20 mL of a developing solution composed of a 2.38% by mass tetramethylammonium hydroxide (TMAH) aqueous solution was dropped on the surface of the resist layer. After standing for 60 seconds, the spin coater was rotated at 2000 rpm for 60 seconds to remove the developing solution on the surface of the resist layer, and subsequently the coating was kept rotating for 60 seconds to dry.
(7A) Resist layer thickness measurement 2: After peeling off a part of the resist layer within 5 mm from the part where the resist layer was peeled off in (2A) above, the resist after development using a stylus type step meter The layer thickness b [nm] was measured.
(8A) Calculation of film thickness reduction amount: The value of the film thickness b was subtracted from the value of the film thickness a to calculate the film thickness reduction amount c [nm] (c=ab) of the resist layer.

(Measurement of reference film loss)
The resist layer has a film reduction amount (hereinafter referred to as “reference film reduction amount”) d [nm] peculiar to each resist depending on the storage period after the formation of the resist layer. This reference film reduction amount d not attributable to the conductive film was measured by the following procedures (1B) to (6B).
(1B) Formation of resist layer: A resist layer was formed on the substrate in the same manner as in (1A) above.
(2B) Measurement of resist layer thickness 1: The initial resist layer thickness a [nm] was measured in the same manner as in (2A) above.
(3B) Baking treatment: Baking treatment was carried out in the same manner as (4A) above, except that a substrate having a resist layer laminated thereon was used.
(4B) Development: Development was carried out in the same manner as (6A) above.
(5B) Thickness measurement of resist layer 2: After peeling off a part of the resist layer within 5 mm from the portion where the resist layer was peeled off in (2B) above, the resist layer after development was developed using a stylus type step meter. The film thickness e [nm] was measured.
(6B) Calculation of film thickness reduction amount: The value of the film thickness e was subtracted from the value of the film thickness a to calculate the reference film thickness reduction amount d (d=a−e) of the resist layer.
The reference film reduction amount d of the resist layer was 3 nm.

(Calculation of the amount of resist layer loss due to the components in the conductive film)
The value of the reference film reduction amount d of the resist layer is subtracted from the value of the film reduction amount c of the resist layer to reduce the film thickness of the resist layer caused by an acidic substance having a molecular weight of 100 or less, which is transferred from the conductive film to the resist layer. The amount f [nm] (f=c−d) was calculated and evaluated according to the following evaluation criteria. The smaller the film reduction amount f is, the more preferable, and A and B are passed.
A: The film reduction amount f is less than 5 nm.
B: The film reduction amount f is 5 nm or more and less than 20 nm.
C: The film reduction amount f is 20 nm or more.

[Example 1]
<Production of conductive polymer (A)>
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.
An aqueous solution of 100 mmol of ammonium peroxodisulfate (oxidant solution) was added dropwise to the obtained monomer solution at 10°C. After completion of dropping, 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 liquid in which a reaction product was precipitated (polymerization step).
The obtained reaction liquid is filtered by a centrifugal filter to collect a precipitate (reaction product), wash the reaction product with 1 L of methanol (SP value: 29.7 MPa ^1/2 ) and then dry the product. The powdery conductive polymer (A1) was obtained (purification step).
The amount of methanol used in the purification step corresponds to 5000 parts by mass with respect to 100 parts by mass of the conductive polymer (A1).
The content of the acidic substance (a) in the obtained conductive polymer (A1) was measured. The results are shown in Table 1.

<Preparation of conductive composition>
2 parts by mass of the conductive polymer (A1), 93.1 parts by mass of water, and 4.9 parts by mass of isopropyl alcohol (IPA) were mixed to obtain a conductive composition.
The electroconductivity of the obtained electroconductive composition was evaluated and a film reduction test was conducted. The results are shown in Table 1.

[Example 2]
A conductive polymer (A2) was produced in the same manner as in Example 1 except that the washing solvent used in the purification step was changed to ethanol (SP value: 26.0 MPa ^1/2 ) and the acidic substance (a) was contained. The quantity was measured. The results are shown in Table 1.
Further, a conductive composition was prepared in the same manner as in Example 1 except that the obtained conductive polymer (A2) was used, the conductivity was evaluated, and the film reduction test was performed. The results are shown in Table 1.

[Example 3]
A conductive polymer (A3) was produced in the same manner as in Example 1 except that the amount of methanol used in the purification step was changed to 0.3 L, and the content of the acidic substance (a) was measured. The results are shown in Table 1. The amount of methanol used in the purification step is 1500 parts by mass with respect to 100 parts by mass of the conductive polymer (A3).
Further, a conductive composition was prepared in the same manner as in Example 1 except that the obtained conductive polymer (A3) was used, the conductivity was evaluated, and a film reduction test was performed. The results are shown in Table 1.

[Comparative Example 1]
A conductive polymer (A4) was produced in the same manner as in Example 1 except that the purification step was not performed, and the content of the acidic substance (a) was measured. The results are shown in Table 1.
Further, a conductive composition was prepared in the same manner as in Example 1 except that the obtained conductive polymer (A4) was used, the conductivity was evaluated, and the film reduction test was performed. The results are shown in Table 1.

The abbreviations in Table 1 are as follows.
-MeOH: Methanol-EtOH: Ethanol-IPA: Isopropyl alcohol

As is clear from Table 1, the conductive polymer (A) obtained in each Example has a content of the acidic substance (a) of 10000 mass ppm or less, and a conductive composition containing these conductive polymers (A). From the product, it was possible to form a conductive film with little loss of the resist layer and excellent conductivity.
On the other hand, the conductive polymer (A) obtained in Comparative Example 1 contained a large amount of the acidic substance (a), and the resist layer was easily reduced in film thickness.

INDUSTRIAL APPLICABILITY The conductive polymer and the conductive composition of the present invention can form a conductive film in which the resist layer has little film loss, and are useful as an antistatic agent during charged particle beam drawing.

Claims (3)

A conductive polymer having an acidic group,
A conductive polymer in which the content of an acidic substance having a molecular weight of 100 or less is 10000 mass ppm or less. The conductive polymer according to claim 1, which is used for preventing electrostatic charge when drawing a charged particle beam. A conductive composition comprising the conductive polymer according to claim 1 or 2 and a solvent.