JP7298291B2 - Conductive composition, coating film, method for forming resist pattern - Google Patents

Description

The present invention relates to a conductive composition, a coating film of the conductive composition, and a method of forming a resist pattern using the conductive composition.

Pattern formation technology using charged particle beams such as electron beams and ion beams is expected to be the next-generation technology of photolithography.
When using a charged particle beam, it is important to improve the sensitivity of the resist to improve productivity. Therefore, a highly sensitive chemically amplified resist is produced by generating acid in exposed areas or areas irradiated with charged particle beams, followed by heat treatment called post-exposure baking (PEB) to promote cross-linking or decomposition reactions. usage is prevalent.

By the way, in the pattern formation method using a charged particle beam, especially when the substrate is insulating, the trajectory of the charged particle beam is bent due to the electric field generated by the charge-up of the substrate, and the desired pattern is obtained. There was a problem that it was difficult to

In order to solve this problem, there is a method in which a conductive composition containing a conductive polymer is applied to the surface of a resist layer to form a conductive film (antistatic film), and the surface of the resist layer is coated with the conductive film. known to be effective.
For example, Patent Document 1 describes an example in which a conductive film is formed by applying a conductive composition containing a conductive polymer having an acidic group and a water-soluble polymer exhibiting surface activity to the surface of a resist layer. ing.

Japanese Patent Application Laid-Open No. 2002-226721

In recent years, along with the trend toward miniaturization of semiconductor devices, there has been a demand for control of resist shapes on the order of several nanometers. Therefore, the antistatic film formed on the resist layer is required to have surface smoothness.
However, the coating film of the conductive composition described in Patent Document 1 does not necessarily have sufficient surface smoothness.
The present invention provides a conductive composition capable of forming a coating film with excellent surface smoothness, and a method of forming a coating film and a resist pattern using the same.

The present invention has the following aspects.
[1] A conductive composition containing a conductive polymer that satisfies Condition 1 below.
Condition 1: The proportion of particles with a particle diameter of 1.8 nm or more is 8.5% or less in the particle diameter distribution (number-based frequency distribution) by the dynamic light scattering method using an aqueous solution of a conductive polymer as a sample. .
[2] The conductive composition of [1], wherein the conductive polymer contains a salt of a conductive polymer (A) having an acidic group and a basic compound (B).
[3] A coating film of the conductive composition of [1] or [2].
[4] A lamination step of forming a coating film of the conductive composition of [1] or [2] on the surface of the resist layer of a substrate having a resist layer made of a chemically amplified resist on one side; and an exposure step of patternwise irradiating electron beams from the coating film side.

The conductive composition of the present invention can form a coating film with excellent surface smoothness.
The coating film of the present invention has conductivity and excellent surface smoothness.
According to the resist pattern forming method of the present invention, an antistatic film having excellent surface smoothness can be formed on a resist layer, and a resist pattern can be formed with high precision.

4 is a graph showing the particle size distribution of the conductive compositions of Examples and Comparative Examples, measured by a dynamic light scattering method.

Embodiments of the present invention will be described.
As used herein, “conductivity” means having a surface resistance value of 1×10 ¹¹ Ω/□ or less. The surface resistance value is obtained from the potential difference between currents when a constant current is applied.
As used herein, the term “solubility” refers to water, water containing at least one of a base and a basic salt, water containing an acid, or a mixed solvent of water and a water-soluble organic solvent, 10 g (liquid temperature 25° C.) It means that 0.1 g or more is uniformly dissolved in . In addition, "water-soluble" means solubility in water in relation to the above-mentioned solubility.
As used herein, the term "mass average molecular weight" refers to a mass average molecular weight (in terms of sodium polystyrenesulfonate or polyethylene glycol) measured by gel permeation chromatography (GPC).

The conductive composition of this embodiment contains a conductive polymer. The conductive polymer present in the conductive composition satisfies Condition 1 below. A conductive composition contains a solvent as needed. Furthermore, optional components other than the conductive polymer and the solvent may be included.
Condition 1: The ratio of particles with a particle diameter of 1.8 nm or more is 8.5% or less in the particle diameter distribution (number-based frequency distribution) obtained by a dynamic light scattering method using an aqueous solution of a conductive polymer as a sample.

<Conductive polymer>
A known conductive polymer can be used. Examples include polypyrrole, polythiophene, polythiophene vinylene, polytelluphene, polyphenylene, polyphenylene vinylene, polyaniline, polyacene, and polyacetylene.
Among these, polypyrrole, polythiophene, and polyaniline are preferable from the viewpoint of excellent conductivity.

The conductive polymer preferably has water solubility or water dispersibility. When the conductive polymer is water-soluble or water-dispersible, the coating property of the conductive composition is enhanced, and a conductor having a uniform thickness can be easily obtained.

The conductive polymer is preferably a conductive polymer having an acidic group (hereinafter also simply referred to as "conductive polymer (A)"). Having an acidic group increases the water solubility. The acidic group is preferably a sulfonic acid group or a carboxy group. You may have two types of acidic groups in one molecule. Some or all of the acidic groups may form a salt.
As the conductive polymer (A), 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, JP-A-H9 6-293828, JP 7-118524, JP 6-32845, JP 6-87949, JP 6-256516, JP 7-41756, JP 7- The conductive polymers disclosed in JP-A-48436, JP-A-4-268331, JP-A-2014-65898, etc. are preferable from the viewpoint of solubility.

As the conductive polymer (A), specifically, phenylene vinylene substituted with at least one group selected from the group consisting of sulfonic acid group and carboxyl group at α-position or β-position, vinylene, thienylene, pyrrolylene , phenylene, iminophenylene, isothianaphthene, furylene, and carbazolylene as repeating units.
Further, when the π-conjugated conductive polymer contains at least one repeating unit selected from the group consisting of iminophenylene and galbazolylene, on the nitrogen atom of the repeating unit, from 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 carboxyl group, or an alkyl group containing an ether bond at the nitrogen atom Conductive polymers having thereon may be mentioned.
Among these, from the viewpoint of conductivity and solubility, thienylene, pyrrolylene, iminophenylene, phenylene vinylene, carbazolylene, and β-position substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group. A conductive polymer having, as a monomer unit (unit), at least one selected from the group consisting of isothianaphthene is preferred.

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 being able to exhibit high conductivity and solubility, A conductive polymer containing 20 to 100 mol % in all units (100 mol %) constituting the conductive polymer is preferred.

In formulas (1) to (4), X represents a sulfur atom or a nitrogen atom, R ¹ to R ¹⁵ each independently represents a hydrogen atom, a straight or branched alkyl group having 1 to 24 carbon atoms, 1 to 24 linear or branched alkoxy groups, acidic groups, hydroxy groups, nitro groups, halogen atoms (-F, -Cl, -Br or I), -N(R ¹⁶ ) ₂ , -NHCOR ¹⁶ , - 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 general formula (1), at least one of R ³ to R ⁶ in general formula (2), and R ⁷ to R ¹⁰ in general formula (3) At least one of them, at least one of R ¹¹ to R ¹⁵ in general formula (4) is an acidic group or a salt thereof.
The acidic group is a sulfonic acid group (sulfo group) or a carboxylic acid group (carboxy group).

In the conductive polymer (A), the sulfonic acid group may exist in an acid state (--SO ₃ H) or in an ionic state (--SO ₃ ⁻ ). The sulfonic acid group also includes a substituent having a sulfonic acid group (--R ¹⁷ SO ₃ H).
Carboxylic acid groups in the conductive polymer (A) may exist in an acid state (--COOH) or in an ionic state ( ^--COO.sup.- ). Carboxylic acid groups also include substituents (-R ¹⁷ COOH) having a carboxylic acid group.
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. show.

Salts of acidic groups include alkali metal salts, alkaline earth metal salts, ammonium salts, or substituted ammonium salts of sulfonic acid groups 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 these skeletons.
Examples of alkaline earth metal salts include magnesium salts and calcium salts.
Examples of substituted ammonium salts 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, diisopropyl ammonium, butylammonium, dibutylammonium, methylpropylammonium, ethylpropylammonium, methylisopropylammonium, ethylisopropylammonium, methylbutylammonium, ethylbutylammonium, tetramethylammonium, tetramethylolammonium, tetraethylammonium, tetra-n-butylammonium, tetra sec-butylammonium, tetra-t-butylammonium and the like.
Saturated alicyclic ammonium salts include, for example, 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.

The conductive polymer (A) preferably has a unit represented by the above general formula (4) from the viewpoint of being able to express high conductivity, and among them, from the viewpoint of excellent solubility, the following general formula 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 straight or branched alkyl group having 1 to 24 carbon atoms, a straight 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). 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 linear or branched alkoxy group having 1 to 4 carbon atoms in terms of ease of production, Preferably any one of the other is a sulfonic acid group and the rest are hydrogen.

The conductive polymer (A), from the viewpoint of excellent solubility in water and organic solvents regardless of pH, among all units (100 mol%) constituting the conductive polymer (A), the general formula (5) It preferably contains 10 to 100 mol %, more preferably 50 to 100 mol %, and particularly preferably 100 mol % of the unit represented by.
Moreover, from the viewpoint of excellent conductivity, the conductive polymer (A) preferably contains 10 or more units represented by the general formula (5) in one molecule.

In the conductive polymer (A), from the viewpoint of further improving the solubility, the number of aromatic rings to which acidic groups are bonded to the total number of aromatic rings in the polymer is preferably 50% or more, and 70% or more. It is more preferably 80% or more, particularly preferably 90% or more, and most preferably 100%.
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 the monomers when the conductive polymer (A) is produced.

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, an alkyl group having 1 to 24 carbon atoms, an alkoxy group having 1 to 24 carbon atoms, a halogen group (-F, -Cl, -Br or I) and the like are preferable. Among these, an alkoxy group having 1 to 24 carbon atoms is most preferable from the viewpoint of electron donating properties.

Further, the conductive polymer (A) may contain substituted or unsubstituted aniline, thiophene, It may contain one or more units selected from the group consisting of pyrrole, phenylene, vinylene, divalent unsaturated groups, and divalent saturated groups.

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

In formula (6), each of R ²² to R ³⁷ is 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). At least one of R ²² to R ³⁷ is an acidic group or a salt thereof. Also, n indicates the degree of polymerization. In the present invention, n is preferably an integer of 5-2500.

At least part of the acidic groups contained in the conductive polymer (A) is desirably in the free acid form from the viewpoint of improving electrical conductivity.

The weight average molecular weight of the conductive polymer (A) is preferably 1,000 to 1,000,000, more preferably 1,500 to 800,000, more preferably 2,000, in terms of conductivity, solubility, and film-forming properties, in terms of sodium polystyrene sulfonate by GPC. ~500,000 is more preferable, and 2,000 to 100,000 is particularly preferable. If the weight average molecular weight of the conductive polymer (A) is less than 1000, the solubility is excellent, but the conductivity and film formability may be insufficient. On the other hand, when the weight average molecular weight exceeds 1,000,000, the solubility may be insufficient although the conductivity is excellent.
Here, "film formability" 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.

A known method can be used as the method for producing the conductive polymer (A), and is not particularly limited as long as the effect of the present invention is achieved.
Specific examples include a method of polymerizing a polymerizable monomer (raw material monomer) having any of the monomer units described above by various synthetic methods such as chemical oxidation and electrolytic oxidation. As such a method, for example, the synthesis methods described in JP-A-7-196791 and JP-A-7-324132 can be applied.
An example of the method for producing the conductive polymer (A) is described below.

The conductive polymer (A) can be obtained, for example, by polymerizing raw material monomers using an oxidizing agent in the presence of a basic reaction aid.
Specific examples of raw material monomers include at least one selected from the group consisting of acidic group-substituted anilines, alkali metal salts, ammonium salts and substituted ammonium salts thereof.
Examples of acidic group-substituted anilines include sulfonic acid group-substituted anilines having a sulfonic acid group as an acidic group.
Typical sulfone-substituted anilines 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 sulfonic group-substituted anilines other than aminobenzenesulfonic acids include methylaminobenzenesulfonic acid, ethylaminobenzenesulfonic acid, n-propylaminobenzenesulfonic acid, iso-propylaminobenzenesulfonic acid, n-butylaminobenzenesulfonic acid, Alkyl-substituted aminobenzenesulfonic acids such as sec-butylaminobenzenesulfonic acid and t-butylaminobenzenesulfonic acid; Alkoxy-substituted aminobenzenesulfones such as methoxyaminobenzenesulfonic acid, ethoxyaminobenzenesulfonic acid and propoxyaminobenzenesulfonic acid Acids; hydroxy group-substituted aminobenzenesulfonic acids; nitro group-substituted aminobenzenesulfonic acids; 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, or Halogen-substituted aminobenzenesulfonic acids are preferred, and alkoxy group-substituted aminobenzenesulfonic acids, alkali metal salts, ammonium salts and substituted ammonium salts thereof are particularly preferred in terms of ease of production.
Any one of these sulfonic acid group-substituted anilines may be used alone, or two or more of them may be mixed and used in an arbitrary ratio.

Examples of basic reaction aids include inorganic bases such as sodium hydroxide, potassium hydroxide and lithium hydroxide; ammonia; methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylmethylamine, ethyldimethylamine, diethyl fatty amines such as methylamine; saturated cyclic amines; and unsaturated cyclic amines such as pyridine, α-picoline, β-picoline, γ-picoline and quinoline.
Among these, inorganic bases, aliphatic amines, and cyclic unsaturated amines are preferred, and inorganic bases are more preferred.
Any one of these basic reaction auxiliaries may be used alone, or two or more thereof may be mixed and used in an arbitrary ratio.

The oxidizing agent is not limited as long as it has a standard electrode potential of 0.6 V or more, but for example, peroxodisulfates such as peroxodisulfuric acid, ammonium peroxodisulfate, sodium peroxodisulfate and potassium peroxodisulfate; Hydrogen peroxide etc. are mentioned.
Any one of these oxidizing agents may be used alone, or two or more of them may be used by mixing them in an arbitrary ratio.

Examples of polymerization methods include a method of dropping a mixed solution of raw material monomers and a basic reaction aid into an oxidizing agent solution, a method of dropping an oxidizing agent solution into a mixed solution of raw material monomers and a basic reaction auxiliary, and a method of For example, a mixed solution of raw material monomers and a basic reaction aid and an oxidizing agent solution are added dropwise to a container or the like at the same time.

After polymerization, the solvent is usually filtered off using a filter such as a centrifugal separator. Furthermore, after washing the filtrate with a washing liquid as necessary, it is dried to obtain the conductive polymer (A).
The acidic groups of the conductive polymer (A) thus obtained are groups selected from the group consisting of free acids, alkali metal salts, alkaline earth metal salts, ammonium salts and substituted ammonium salts. Therefore, it is possible to obtain a polymer in which these groups are mixed rather than single.
For example, when sodium hydroxide is used as a basic reaction aid during polymerization, most of the acidic groups of the conductive polymer (A) are sodium salts. When ammonia is used as a basic reaction aid, most of the acidic groups of the conductive polymer (A) are ammonium salts, and when trimethylamine is used, most of the acidic groups of the conductive polymer (A) is a trimethylammonium salt, and when quinoline is used, most of the acidic groups of the conductive polymer (A) are obtained in the form of quinolinium salt.

The conductive polymer (A) obtained in this way contains oligomers, acidic substances, basic substances (basic reaction aids, ammonium ions that are decomposed products of oxidizing agents, etc.) associated with side reactions. May contain low molecular weight components. These low-molecular-weight components are factors that hinder electrical conductivity.

Therefore, it is preferable to purify the conductive polymer (A) to remove low molecular weight components.
The method for purifying the conductive polymer (A) is not particularly limited, and any method such as an ion exchange method, acid washing in a protonic acid solution, removal by heat treatment, and neutralization precipitation can be used. Among these, the ion exchange method is particularly effective from the viewpoint of easily obtaining a highly pure conductive polymer (A).
By using an ion exchange method, it is possible to effectively remove basic substances present in a state of forming a salt with the acidic groups of the conductive polymer (A), acidic substances, etc., and to obtain a highly pure conductive polymer (A). can be obtained.

Examples of ion exchange methods include column-type and batch-type treatments using ion exchange resins such as cation exchange resins and anion exchange resins; and electrodialysis methods.
In the case of purifying the conductive polymer (A) by an ion exchange method, the reaction mixture obtained by polymerization is dissolved in an aqueous medium so as to have a desired solid content concentration, and the polymer solution is brought into contact with the ion exchange resin. It is preferable to let
Examples of the aqueous medium include those similar to the solvent (D) described below.
The concentration of the conductive polymer (A) in the polymer solution is preferably 0.1 to 20% by mass, more preferably 0.1 to 10% by mass, from the viewpoint of industrial efficiency and purification efficiency.

The electrically conductive polymer (A) purified in this manner is sufficiently free of oligomers, acidic substances, basic substances and the like, and exhibits superior electrical conductivity. The conductive polymer (A) after purification is in a state of being dispersed or dissolved in an aqueous medium. Therefore, if the aqueous medium is completely removed by an evaporator or the like, a solid conductive polymer (A) can be obtained. may be used.

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, relative to the total mass of the conductive composition. is more preferred.
In addition, the content of the conductive polymer (A) is preferably 50 to 99.9% by mass, more preferably 80 to 99.9% by mass, based on the total mass of the solid content of the conductive composition, and 95 to 99.9% by mass is more preferred. The solid content of the conductive composition is the residue after removing the solvent (D) from the conductive composition.
When the content of the conductive polymer (A) is within the above range, the coating property of the conductive composition and the conductivity of the coating film formed from the conductive composition are well balanced.

<Basic compound (B)>
When the conductive polymer is a conductive polymer (A) having an acidic group, when the conductive composition contains a basic compound (B), the basic compound (B) is in the conductive polymer (A) It is thought that it becomes possible to efficiently act on acidic groups and improve the stability of the conductive polymer (A). Here, efficiently acting on the acidic groups in the conductive polymer (A) means that the conductive polymer (A) can be stably neutralized, and the acidic groups of the conductive polymer (A) and the basic compound (B ) to form a stable salt. That is, the conductive polymer (A) is neutralized with the basic compound (B), and the conductive polymer contains a salt of the conductive polymer (A) and the basic compound (B).
As a result, destabilization of the acidic groups of the conductive polymer (A) due to hydrolysis in the conductive composition can be suppressed, making it difficult for the acidic groups to leave. In addition, by forming a stable salt with the acidic group of the conductive polymer (A) and the basic compound (B), decomposition of the conductive polymer (A) itself can be suppressed. In addition, the basic compound (B) also forms a stable salt with a decomposition product (such as sulfate ion) of the oxidizing agent used in the production of the conductive polymer (A). Therefore, generation of acidic groups derived from the conductive polymer (A) and sulfate ions derived from the oxidizing agent in the conductive composition can be suppressed. In addition, the content of decomposition products of the conductive polymer (A) in the conductive composition can also be reduced.
Therefore, especially in the pattern formation method using a charged particle beam using a chemically amplified resist, the migration of acidic substances from the conductive film to the resist layer side is suppressed, and the influence of film reduction of the resist layer can be suppressed.

The basic compound (B) is not particularly limited as long as it is a compound having basicity. For example, the following quaternary ammonium salt (b-1), basic compound (b-2), basic compound (b -3).
Quaternary ammonium salt (b-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 (b-2): Basic compound having one or more nitrogen atoms (excluding quaternary ammonium salt (b-1) and basic compound (b-3)).
Basic compound (b-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 salt (b-1), the nitrogen atom to which the four substituents are attached is the nitrogen atom of the quaternary ammonium ion.
In the quaternary ammonium salt (b-1), the hydrocarbon group bonded to the nitrogen atom of the quaternary ammonium ion includes an alkyl group, an aralkyl group, an aryl group and the like.
Examples of the quaternary ammonium salt (b-1) include tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, and benzyltrimethylammonium hydroxide.

Basic compounds (b-2) include, for example, 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.

In the basic compound (b-3), basic groups include, for example, basic groups defined as Arrhenius bases, Bronsted bases, Lewis bases and the like. Specifically, ammonia etc. are mentioned. A hydroxy group may be in the state of —OH or in the state of being protected by a protecting group. Examples of protective groups include acetyl group; silyl groups such as trimethylsilyl group and t-butyldimethylsilyl group; acetal type protective groups such as methoxymethyl group, ethoxymethyl group and methoxyethoxymethyl group; benzoyl group; mentioned.
Basic compounds (b-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. .

Any one of these basic compounds (B) may be used alone, or two or more thereof may be used by mixing at any ratio.
Among these, the quaternary polymer easily forms a salt with the acidic group of the conductive polymer (A) and is excellent in the effect of stabilizing the acidic group and suppressing the influence of the acidic substance from the coating film on the resist pattern. It preferably contains at least one selected from the group consisting of an ammonium salt (b-1) and a basic compound (b-2).

As shown in the examples below, when the conductive polymer contains a salt of a conductive polymer (A) having an acidic group and a basic compound (B), the content ratio of these conductive polymer particles The size distribution can be adjusted.
Regarding the content ratio of the conductive polymer (A) and the basic compound (B), the content of the basic compound (B) with respect to all units (100 mol%) having an acidic group among the units constituting the conductive polymer (A). The degree of neutralization (unit: mol %) represented by the base equivalent is preferably set so that the particle size distribution of the conductive polymer satisfies Condition 1 above.
For example, in terms of excellent surface smoothness of the coating film, the amount of the basic compound (B) added is such that when the solid content concentration of the conductive composition is about 1 to 2% by mass, the degree of neutralization is 45 mol% or less. Or 55 mol% or more is preferable, 40 mol% or less or 60 mol% or more is more preferable, and 40 mol% or less or 70 mol% or more is even more preferable.

<Solvent (D)>
The solvent (D) is not particularly limited as long as it is a solvent capable of dissolving the conductive polymer (A) and the basic compound (B) as long as it has the effect of the present invention. and an organic solvent.
Examples of water include tap water, ion-exchanged water, pure water, and distilled water.
Examples of organic solvents 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 glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether and propylene glycol propyl ether; amides such as dimethylformamide and dimethylacetamide; and pyrrolidones such as N-methylpyrrolidone and N-ethylpyrrolidone. . Any one of these organic solvents may be used alone, or two or more of them may be used by mixing them in an arbitrary ratio.
When a mixed solvent of water and an organic solvent is used as the solvent (D), their mass ratio (water/organic solvent) is preferably 1/100 to 100/1, preferably 2/100 to 100/2. It is more preferable to have

The content of the solvent (D) is preferably 1 to 99% by mass, more preferably 10 to 98% by mass, even more preferably 50 to 98% by mass, relative to the total mass of the conductive composition. If the content of the solvent (D) is within the above range, the coatability is further improved.
Incidentally, the conductive polymer (A) is purified and dispersed or dissolved in an aqueous medium (hereinafter, the conductive polymer (A) in this state is also referred to as a "conductive polymer solution"). The content of the solvent (D) in the conductive composition also includes the aqueous medium derived from the conductive polymer solution.

<Optional component>
The conductive composition may contain components (optional components) other than the conductive polymer (A), basic compound (B) and water (D), if necessary.
Examples of optional components include surfactants, pigments, antifoaming agents, ultraviolet absorbers, antioxidants, heat resistance improvers, leveling agents, anti-sagging agents, matting agents, preservatives and the like.

<Method for producing conductive composition>
A conductive composition is obtained by mixing a conductive polymer, a solvent as necessary, and an optional component.

When the conductive polymer (A) is used as the conductive polymer, the conductive polymer (A), the basic compound (B), a solvent as necessary, and optional components are mixed to form a conductive composition. manufacture. Water is preferred as the solvent.
A neutralization reaction proceeds when the conductive polymer (A) and the basic compound (B) come into contact with each other. Heat may be applied to accelerate the neutralization reaction. The heating temperature in the neutralization step is preferably less than 80°C, more preferably 40°C or more and less than 80°C, and even more preferably 60°C or more and less than 80°C. If the heating temperature is less than 80°C, it is possible to suppress the elimination of acidic groups from the conductive polymer (A).
When the conductive composition contains optional components, it is preferable to add the optional components to the aqueous solution after the neutralization step. If necessary, the solution after the neutralization step may be further diluted with a solvent.

<Coating film>
The coating film of the conductive composition of the present embodiment is a film (conductive film) containing a conductive polymer and having conductivity.
As shown in Examples below, when the conductive polymer in the conductive composition satisfies Condition 1, the surface smoothness of the coating film is excellent.
The arithmetic mean roughness (Ra) of the coating film (conductive film) is preferably 0.7 nm or less, more preferably 0.6 nm or less. If the arithmetic mean roughness (Ra) of the conductive film is 0.7 nm or less, the conductivity will be more uniform. Moreover, the arithmetic mean roughness (Ra) of the conductive film is preferably 0.1 nm or more from the viewpoint of the reliability of the measured value.
The arithmetic average roughness (Ra) of the conductive film is a value measured using a stylus profilometer (step/surface roughness/fine shape measuring device).

The film thickness of the coating film (conductive film) is preferably 30 nm or less, more preferably 20 nm or less, and particularly preferably 15 nm or less, from the viewpoint of uniformity of the coating film. From the viewpoint of the smoothness of the conductive film, the thickness is preferably 5 nm or more.
The film thickness of the conductive film is a value measured using a contact profilometer.

A coating film (conductive film) can be formed by applying a conductive composition onto a substrate and drying it. Heat treatment may be performed after drying, if necessary.
The substrate is not particularly limited as long as it has the effect of the present invention, but polyester resins such as PET and PBT, polyethylene, polyolefin resins typified by polypropylene, vinyl chloride, nylon, polystyrene, polycarbonate, epoxy resin, fluororesin, Polysulfone, polyimide, polyurethane, phenolic resin, silicone resin, synthetic paper, and other high-molecular compound moldings, films, paper, iron, glass, quartz glass, various wafers, aluminum, copper, zinc, nickel, stainless steel, etc. , and those coated with various paints, photosensitive resins, resists, etc. on the surface of these substrates.
The shape of the substrate is not particularly limited, and may be a plate shape or a shape other than the plate shape.

The method of applying the conductive composition to the substrate is not particularly limited as long as the effect of the present invention is achieved, and may be spin coating, spray coating, dip coating, roll coating, gravure coating, or reverse coating. , a roll brush method, an air knife coating method, a curtain coating method, and the like.

The heat treatment temperature is preferably in the range of 40° C. to 250° C., more preferably in the range of 60° C. to 200° C., from the viewpoint of conductivity. From the viewpoint of stability, the treatment time is preferably within 1 hour, more preferably within 30 minutes.
Instead of the heat treatment, the coating film may be left at normal temperature (25° C.) for 1 to 60 minutes.

<Method of forming resist pattern>
The conductive composition of the present embodiment is suitable for antistatic resist. Specifically, the conductive composition of the present embodiment is applied to the surface of a resist layer formed 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 becomes the antistatic film of the resist layer.

The method for forming a resist pattern of the present embodiment is a lamination step of forming a coating film of the conductive composition of the present embodiment on the surface of a substrate having a resist layer made of a chemically amplified resist on one side thereof. and an exposure step of patternwise irradiating the substrate with an electron beam from the coating film side.
A resist layer made of a chemically amplified resist may be of a positive type or a negative type as long as it has sensitivity to an electron beam. It can be formed using a known chemically amplified resist composition.

After the exposure step, if necessary, a post-exposure bake (hereinafter also referred to as PEB) step is performed to heat the substrate, the conductive film is removed by washing with water, and the resist layer is developed to form a resist pattern. A water washing/developing process is performed to form a
In the water washing/developing step, for example, an alkaline developer may be used for washing, and the resist layer may be developed at the same time as the conductive film is removed. can be a method.
After the water washing/developing process, the substrate may be rinsed with pure water or the like, if necessary.
After the water washing/development step or after the rinse treatment, the substrate having the resist pattern formed thereon may be heated (post-baked), if necessary.

A step of storing the substrate (storage step) may be provided between the lamination step and the exposure step. Storage conditions such as storage period, temperature, and humidity in the storage step are not particularly limited as long as the effect of the present invention is achieved, but preferably within 2 months, 5° C. to 30° C., and 70% or less.

Alternatively, the removal of the conductive film by washing with water may be performed after the exposure step and before the PEB step. A step of storing the substrate (storage step) may be provided between the lamination step and the exposure step.

In the method of forming a resist pattern according to the present embodiment, a substrate having a resist pattern on one side is obtained, and a step of etching using the resist pattern as a mask (etching step) is performed to form a pattern. A substrate is obtained.
If the resist pattern remains on the substrate after the etching step, the method may further include a step of removing the resist pattern on the substrate with a remover.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the following examples are not intended to limit the scope of the present invention.

Various measurement and evaluation methods in Examples and Comparative Examples are as follows.
<Measurement/evaluation method>
(Measurement of particle size distribution)
Using an aqueous solution of a conductive polymer (solid content concentration 1 to 2% by mass, 25 ° C.) as a sample, a dynamic light scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., "Nanotrac Wave II) was used to measure the particle size distribution ( number-based frequency distribution) was measured.
(Measurement of film thickness)
The thickness of the coating film (conductive film) was measured using a contact-type profilometer (manufactured by KLA-Tencor, "Stylus profiler P-16+").
(Evaluation of surface smoothness)
Using a scanning probe microscope (manufactured by Seiko Instruments Inc., "SPI4000/SPA400"), the arithmetic average roughness (Ra) of the coating film (conductive film) was measured under the following measurement conditions.
<<Measurement conditions>>
・Cantilever: SI-DF20
・Measurement mode: Tapping mode ・Scan range: 1 μm×1 μm
・Scanning speed: 0.6Hz

<Production Example 1: Production of conductive polymer (A-1) having acidic group>
10 mol of 3-aminoanisole-4-sulfonic acid was dissolved in 5820 mL of a 4 mol/L pyridine solution (solvent: water/acetonitrile=3/7 (mass ratio)) at 40° C. to obtain a monomer solution.
Separately, 10 mol of ammonium peroxodisulfate was dissolved in 8560 mL of a solution of water/acetonitrile=3/7 (mass ratio) to obtain an oxidant solution.
Then, while cooling the oxidant solution to 5° C., the monomer solution was added dropwise. 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 conductive polymer. Thereafter, the resulting reaction mixture containing the conductive polymer was filtered using a centrifugal filter. Furthermore, it was washed with methanol and then dried to obtain 433 g of powdery conductive polymer (A-1).

<Production Example 2: Production of conductive polymer solution (A1-1)>
20 g of the conductive polymer (A-1) obtained in Production Example 1 was dissolved in 980 g of pure water to obtain 1000 g of a conductive polymer solution (A-1-1) having a solid concentration of 2% by mass.
A column was packed with 500 mL of a cation exchange resin (“Amberlite IR-120B” manufactured by Organo Co., Ltd.) washed with ultrapure water.
1000 g of the conductive polymer solution (A-1-1) is passed through this column at a rate of 50 mL/min (SV=6) to remove basic substances and the like from the conductive polymer solution (A1-1- 1) was obtained in an amount of 900 g.
Furthermore, 900 g of the conductive polymer solution (A1-1-1) is passed through the column at a rate of 50 mL / min (SV = 6) to remove basic substances etc. The conductive polymer solution (A1-1 ) was obtained.
Composition analysis of this conductive polymer solution (A1-1) by ion chromatography revealed that 99% by mass or more of the basic substance (pyridine) had been removed. In addition, as a result of measuring the heating residue, it was 2.0% by mass. That is, the conductive polymer solution (A1-1) had a solid content concentration of 2.0% by mass.
Note that one sveldlap (SV) is defined as 1×106 m ³ /s (1 GL/s).

[Example 1]
100 parts by mass of the conductive polymer solution (A1-1) (2 parts by mass in terms of solid content (equivalent to 3.1×10 ⁻³ mol)) is heated and stirred while adding 5% by mass of the basic compound (B). 20.45 parts by mass of a tetrabutylammonium hydroxide aqueous solution (TBAH) was added to obtain a mixed liquid (conductive polymer-containing liquid). The temperature of the resulting mixed solution was maintained and stirred for 2 hours from the start of addition of the basic compound (B). After cooling the resulting mixture to room temperature, 79.55 parts by mass of pure water was mixed with it to obtain 200 parts by mass of a conductive composition.
Table 1 shows the solid concentration, the content of the conductive polymer (A-1), and the content of the basic compound (B) of the obtained conductive composition. The amount of the basic compound (B) added corresponds to 0.40 mol equivalent (neutralization degree of 40 mol%) per 1 mol of the unit having an acidic group among the units constituting the conductive polymer (A). .
Using the obtained conductive composition as a sample, the particle size distribution was measured by the method described above. The results are shown in FIG. In the obtained particle size distribution, the ratio of particles with a particle size of 1.8 nm or more was determined. Table 1 shows the results.

On a 2-inch silicon wafer, the resulting conductive composition was spin-coated (2000 rpm × 60 seconds), and then heat-treated at 80 ° C. for 2 minutes on a hot plate to form a coating film with a thickness of 10 nm (conductive film ) was formed. The surface roughness (arithmetic mean roughness Ra) of the obtained coating film was measured. Table 1 shows the results.

[Examples 2-4]
Example 3 is a reference example.
The amount of the basic compound (B) added was changed so that the content of the basic compound (B) was the value shown in Table 1, and the solid content concentration of the conductive composition was adjusted to the value shown in Table 1. A conductive composition was prepared and evaluated in the same manner as in Example 1, except that the amount of pure water was changed. The results are shown in FIG. 1 and Table 1.
Example 3 is an example in which no basic compound (B) was added.
The degree of neutralization in Example 2 is 70 mol % and the degree of neutralization in Example 4 is 50 mol %.

As shown in the results of Table 1, in the particle size distribution of the conductive polymer in the conductive composition, Example 4, in which the proportion of particles with a particle size of 1.8 nm or more exceeded 8.5%, was similar to Example 1. The surface smoothness of the coating film was significantly inferior to that of 1 to 3.

Claims (4)

A conductive composition containing a conductive polymer that satisfies the following condition 1,
The conductive polymer contains a salt formed by neutralization of a conductive polymer (A) having an acidic group and a basic compound (B),
Among the units constituting the conductive polymer (A), the degree of neutralization represented by the base equivalent of the basic compound (B) with respect to all units having an acidic group is 45 mol% or less or 55 mol% or more. Conductive composition.
Condition 1: The proportion of particles with a particle diameter of 1.8 nm or more is 8.5% or less in the particle diameter distribution (number-based frequency distribution) by the dynamic light scattering method using an aqueous solution of a conductive polymer as a sample. . The conductive composition according to claim 1, wherein said basic compound (B) comprises a quaternary ammonium salt. A coating film of the conductive composition according to claim 1 or 2. A lamination step of forming a coating film of the conductive composition according to claim 1 or 2 on the surface of the resist layer of a substrate having a resist layer made of a chemically amplified resist on one side; A method of forming a resist pattern, comprising an exposure step of patternwise irradiating an electron beam from the coating film side.

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