JP2020158575A - Conductive composition - Google Patents

Abstract

To provide a conductive composition that can form a conductive film in which an additive-derived component is prevented from migrating to a resist layer.SOLUTION: A conductive composition contains a conductive polymer having an acidic group, a solvent, and an additive excluding a basic compound, the additive having a melting point of 60°C or higher. The conductive composition is suitable for static elimination when drawing a charged particle beam.SELECTED DRAWING: None

Description

The present invention relates to conductive compositions.

Pattern formation technology using charged particle beams such as electron beams and ion beams is expected as a next-generation technology for optical lithography. When a charged particle beam is used, 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 acid in the exposed part or the part irradiated with charged particle beams and then promotes the cross-linking reaction or decomposition reaction by heat treatment called post-exposure baking (PEB) treatment. Use is the mainstream.
Further, in recent years, with the trend of miniaturization of semiconductor devices, management of resist shapes on the order of several nm has been required.

By the way, in the pattern forming 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 a desired pattern is obtained. There is a problem that it is difficult to be charged.
As a means for solving this problem, it is effective to apply a conductive composition containing a conductive polymer to the surface of the resist layer to form a conductive film, and to coat the surface of the resist layer with the conductive film. Already known.
For example, Patent Document 1 discloses a conductive composition containing an additive such as glycol ether in order to improve the coatability of the conductive composition containing a polythiophene-based water-soluble conductive polymer.

JP-A-2018-184586

However, when the conductive composition described in Patent Document 1 is applied to a chemically amplified resist, an additive-derived component is transferred to the resist layer when exposure, PEB treatment and development are performed with the conductive film formed on the resist layer. It is easy to migrate and has an effect on the resist layer.
An object of the present invention is to provide a conductive composition capable of forming a conductive film in which an additive-derived component does not easily migrate to a resist layer.

As a result of diligent research, the present inventor applied a conductive composition containing an additive such as a surfactant on a resist layer and heat-treated (prebaked) to form a conductive film, or when this conductivity was formed. It was found that the additive melted during the PEB treatment with the film formed on the resist layer, and as a result, the melted additive migrated to the resist layer. When the melted additive is transferred to the resist layer, the resist layer in the unexposed portion is dissolved during development, and the resist layer is thinned. Therefore, by defining the melting point of the additive contained in the conductive composition, it is found that a conductive film in which the additive-derived component does not easily migrate to the resist layer can be formed even if the additive melts, and the present invention is completed. It came to.

That is, the present invention has the following aspects.
[1] A conductive composition containing a conductive polymer having an acidic group, a solvent, and an additive other than a basic compound.
A conductive composition having a melting point of 60 ° C. or higher for the additive.
[2] The conductive composition of [1], which is used for preventing static electricity when drawing a charged particle beam.

According to the present invention, it is possible to provide a conductive composition capable of forming a conductive film in which additive-derived components are less likely to migrate to the resist layer.

Hereinafter, the present invention will be described in detail. The following embodiments are merely exemplary to illustrate the invention and are not intended to limit the invention to this embodiment alone. The present invention can be implemented in various aspects as long as it does not deviate from the gist 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.
Further, in the present specification, "soluble" means simply water, water containing at least one of a base and a basic salt, water containing an acid, and 10 g of a mixture of water and a water-soluble organic solvent (liquid temperature 25). It means that 0.1 g or more is uniformly dissolved in (° C.). 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.
Further, in the present specification, the "mass average molecular weight" is a mass average molecular weight (in terms of sodium polystyrene sulfonate or polyethylene glycol) measured by gel permeation chromatography (GPC).

[Conductive composition]
The conductive composition of the present invention contains the following conductive polymer (A), solvent (B), and additive (C) other than the basic compound (D). The conductive composition may further contain the basic compound (D).

<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 is enhanced. As a result, the coatability of the conductive composition containing the conductive polymer (A) is enhanced, and it becomes easy to obtain a coating film having a uniform thickness.
The conductive polymer (A) is not particularly limited as long as it has at least one group selected from the group consisting of a sulfonic acid group and a carboxy group in the molecule, and is known without particular limitation as long as it has the effect of the present invention. Conductive polymer can be used. For example, Japanese Patent Application Laid-Open No. 61-197633, Japanese Patent Application Laid-Open No. 63-39916, Japanese Patent Application Laid-Open No. 1-301714, Japanese Patent Application Laid-Open No. 5-504153, Japanese Patent Application Laid-Open No. 5-503953, Japanese Patent Application Laid-Open No. 4-32848 Japanese Patent Application Laid-Open No. 4-328181, Japanese Patent Application Laid-Open No. 6-1453886, Japanese Patent Application Laid-Open No. 6-56987, Japanese Patent Application Laid-Open No. 5-226238, Japanese Patent Application Laid-Open No. 5-1788989, Japanese Patent Application Laid-Open No. 6-293828, Japanese Patent Application Laid-Open No. 7-118524, Japanese Patent Application Laid-Open No. 6-32845, Japanese Patent Application Laid-Open No. 6-87949, Japanese Patent Application Laid-Open No. 6-256516, Japanese Patent Application Laid-Open No. 7-41756, Japanese Patent Application Laid-Open No. 7-48436, Japanese Patent Application Laid-Open No. The conductive polymers shown in Japanese Patent Application Laid-Open No. 4-268331, Japanese Patent Application Laid-Open No. 2014-65598 and the like are preferable from the viewpoint of solubility.

Specific examples of the conductive polymer (A) include phenylene vinylene, vinylene, and thienylene in which the α-position or β-position is substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group. Examples thereof include π-conjugated conductive polymers containing at least one selected from the group consisting of pyrrolylene, phenylene, iminophenylene, isothianaften, furylene, and carbazolylen as a repeating unit.
When the π-conjugated conductive polymer contains at least one repeating unit selected from the group consisting of iminophenylene and galvazolylene, the sulfonic acid group and the carboxy group are added to the nitrogen atom of the repeating unit. The nitrogen atom comprises an alkyl group having at least one group selected from the group consisting of, or an alkyl group substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group, or an alkyl group containing an ether bond. Examples include the conductive polymer having above.
Among these, from the viewpoint of conductivity and solubility, thienylene, pyrrolylene, iminophenylene, phenylene vinylene, carbazolylen, and those 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 isothianaften as a monomer unit (unit) is preferably used.

The conductive polymer (A) is composed of 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 containing 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 are independently hydrogen atoms, linear or branched alkyl groups having 1 to 24 carbon atoms, and carbons. Alkoxy group, acidic group, hydroxy group, nitro group, halogen atom (-F, -Cl, -Br or I), -N (R ¹⁶ ) ₂ , -NHCOR ¹⁶ , of the number 1 to 24 linear or branched chain. 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 of the general formula (1), at least one of R ^{3 to} R ⁶ of the general formula (2), and R ^{7 to} R ¹⁰ of the general formula (3). At least one of them, at least one of R ^{11 to} R ¹⁵ of the general formula (4), is an acidic group or a salt thereof, respectively.

Here, the "acidic group" means a sulfonic acid group (sulfo group) or a carboxylic acid group (carboxy group).
The sulfonic acid group may be contained in the acid state (-SO ₃ H) or in the ionic state (-SO ₃ ⁻ ). Further, the sulfonic acid group also includes a substituent having a sulfonic acid group (-R ¹⁷ SO ₃ H).
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). Further, the carboxylic acid group also includes a substituent having a carboxylic acid group (-R ¹⁷ COOH).
The R ¹⁷ contains a linear or branched alkylene group having 1 to 24 carbon atoms, an arylene group having a linear or branched chain having 1 to 24 carbon atoms, or an aralkylene group having a linear or branched chain having 1 to 24 carbon atoms. Represent.

Examples of the salt of the acidic group include an alkali metal salt of a sulfonic acid group or a carboxylic acid group, an alkaline earth metal salt, an ammonium salt, a substituted ammonium salt and the like.
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 a skeleton thereof.
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, and diisopropyl. Ammonium, butylammonium, dibutylammonium, methylpropylammonium, ethylpropylammonium, methylisopropylammonium, ethylisopropylammonium, methylbutylammonium, ethylbutylammonium, tetramethylammonium, tetramethylolammonium, tetraethylammonium, tetran-butylammonium, tetra Examples thereof include sec-butylammonium and tetrat-butylammonium.
Examples of the saturated alicyclic ammonium salt include piperidinium, pyrrolidinium, morpholinium, piperadinium, and derivatives having a skeleton thereof.
Examples of the unsaturated alicyclic ammonium salt include pyridinium, α-picolinium, β-picolinium, γ-picolinium, quinolinium, isoquinolinium, pyrrolinium, and derivatives having a skeleton thereof.

The conductive polymer (A) preferably has a unit represented by the above general formula (4) from the viewpoint of exhibiting high conductivity, and among them, particularly from the viewpoint of excellent solubility, the following general formula It is more preferable to have the 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, or a linear or branched alkoxy group having 1 to 24 carbon atoms. 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 linear or branched alkoxy group having 1 to 4 carbon atoms because it is easy to manufacture. It is preferable that any one of the other is a sulfonic acid group and the rest is hydrogen.

The conductive polymer (A) has the above general formula (5) among all the units (100 mol%) constituting the conductive polymer (A) from the viewpoint of excellent solubility in water and organic solvents regardless of pH. The unit represented by (1) is preferably contained in an amount of 10 to 100 mol%, more preferably 50 to 100 mol%, and particularly preferably 100 mol%.
Further, 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.

Further, in the conductive polymer (A), from the viewpoint of further improving the solubility, the number of aromatic rings to which acidic groups are bonded is preferably 50% or more, preferably 70%, based on the total number of aromatic rings in the polymer. The above is more preferable, 80% or more is further preferable, 90% or more is particularly preferable, and 100% is 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 the 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, and specifically, has 1 to 1 carbon atoms. Twenty-four alkyl groups, alkoxy groups having 1 to 24 carbon atoms, halogen groups (-F, -Cl, -Br or I) and the like are preferable, and among these, an alkoxy group having 1 to 24 carbon atoms is preferable from the viewpoint of electron donating property. Is most preferable.

Further, the conductive polymer (A) is a constituent unit other than the unit represented by the general formula (5), and is a substituted or unsaturated aniline, thiophene, as long as it does not affect the solubility, conductivity and properties. It may contain one or more units selected from the group consisting of pyrroles, phenylenes, vinylenes, divalent unsaturated groups, and divalent saturated groups.

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 such a structure, 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, or a linear or branched alkoxy group having 1 to 4 carbon atoms. 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 ^{22 to} R ³⁷ is an acidic group or a salt thereof. Further, n indicates 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 10 to 1,000,000, more preferably 1,500 to 800,000, and more preferably 2,000, in terms of sodium polystyrene sulfonate of GPC, from the viewpoint of conductivity, solubility and film forming property. ~ 500,000 is more preferable, and 20 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 million, 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 repellency and the like, and can be evaluated by a method such as spin coating on glass.

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

(Manufacturing method of conductive polymer (A))
The method for producing the conductive polymer (A) of the present embodiment includes a step (polymerization step) of polymerizing the raw material monomer of the conductive polymer (A) in the presence of a polymerization solvent and an oxidizing agent. Further, the method for producing the conductive polymer (A) of the present embodiment may include a step (purification step) of purifying the reaction product obtained in the polymerization 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 the polymerizable monomer from which the above-mentioned monomer unit is derived, and specifically, an acidic group-substituted aniline, an alkali metal salt thereof, an alkaline earth metal salt, an ammonium salt and a substituted ammonium salt. At least one selected from the group consisting of salts can be mentioned.
Examples of the acidic group-substituted aniline include a sulfonic acid group-substituted aniline having a sulfonic acid group as an acidic group.
Typical sulfonic acid-substituted anilines are aminobenzene sulfonic acids, specifically o-, m-, p-aminobenzene sulfonic 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 the sulfon group-substituted aniline other than aminobenzene sulfonic acids include methyl aminobenzene sulfonic acid, ethylaminobenzene sulfonic acid, n-propylaminobenzene sulfonic acid, iso-propylaminobenzene sulfonic acid, n-butylaminobenzene sulfonic acid, and the like. Alkyl group-substituted aminobenzene sulfonic acids such as sec-butylaminobenzene sulfonic acid and t-butyl aminobenzene sulfonic acid; alkoxy group-substituted aminobenzene sulfonic acids such as methoxyaminobenzene sulfonic acid, ethoxyaminobenzene sulfonic acid and propoxyaminobenzene sulfonic 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 bromaminobenzene sulfonic acid can be mentioned.
Among these, alkyl group-substituted aminobenzene sulfonic acids, alkoxy group-substituted aminobenzene sulfonic acids, hydroxy group-substituted aminobenzene sulfonic acids, or hydroxy group-substituted aminobenzene sulfonic acids, in that a conductive polymer (A) having particularly excellent conductivity and solubility can be obtained. Halogen-substituted aminobenzene sulfonic acids are preferable, and alkoxy group-substituted aminobenzene sulfonic acids, alkali metal salts, ammonium salts and substituted ammonium salts thereof are particularly preferable in terms of ease of production.
Any one of these sulfonic acid group-substituted anilines may be used alone, or two or more thereof may be mixed and used in an arbitrary ratio.

Examples of the polymerization solvent include water, an organic solvent, and a mixed solvent of water and an organic solvent. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, propyl alcohol and butanol; ketones such as acetone and ethyl isobutyl ketone; ethylene glycols such as ethylene glycol and ethylene glycol methyl ether; propylene glycol and propylene glycol. Propropylene glycols such as methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether and propylene glycol propyl ether; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; N-methylpyrrolidone, N-ethylpyrrolidone and the like. Pyrrolidones and the like.
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, but peroxodisulfates such as peroxodisulfuric acid, 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. Fatty amines such as methylamine; cyclic saturated amines; cyclic unsaturated amines such as pyridine, α-picoline, β-picoline, γ-picoline and quinoline can be mentioned.
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 in an arbitrary ratio.

Examples of the polymerization method include 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 a reaction vessel or the like 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 oxidizing agent 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., and even 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 a decrease in conductivity due to the progress of side reactions and changes in the redox structure of the main chain of the conductive polymer (A) to be 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) which is a reaction product is obtained in a state of being dissolved or precipitated in a 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 by a filter such as a centrifuge to obtain a reaction product.

The reaction product may contain low molecular weight components such as unreacted raw material monomers and oligomers associated with the occurrence of side reactions. These low molecular weight components are impurities and cause a factor of inhibiting conductivity.
Therefore, after the polymerization step, it is preferable to purify the reaction product to remove low molecular weight components.

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 even more preferable.
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 with respect to the total mass of the solid content of the conductive composition. More preferred. 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 balance between the coatability of the conductive composition and the conductivity of the coating film formed from the conductive composition is 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) and the additive (C) and the basic compound (D) described later. Although not, water, an organic solvent, and a mixed solvent of water and an organic solvent can be mentioned.
Examples of water include tap water, ion-exchanged water, pure water, ultrapure 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), the mass ratio (water / organic solvent) of these is preferably 1/100 to 100/1, and 2/100 to 100/2. More preferably.

The content of the solvent (B) is preferably 1 to 99.9% by mass, more preferably 10 to 98% by mass, still more 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.

<Additive (C)>
The additive (C) has a melting point of 60 ° C. or higher, and is a compound other than the conductive polymer (A), the solvent (B), and the basic compound (D) described later.
When the conductive composition is applied onto the resist layer and heat treatment such as prebaking treatment or PEB treatment is performed, the additive (C) melts when the melting point of the additive (C) is lower than the heat treatment temperature. However, when the melting point of the additive (C) is 60 ° C. or higher, even if the additive (C) is melted by the heat treatment, it is difficult to migrate to the resist layer, and the film loss of the resist layer can be suppressed. Although it is not clear why the additive (C) is difficult to transfer to the resist layer even if it melts, the additive (C) having a melting point of 60 ° C. or higher is easily mixed in the conductive polymer (A) and is added. The viscosity of the agent (C) tends to be high. Therefore, even if the additive (C) melts, it remains in the conductive film and is unlikely to migrate to the resist layer.
The melting point of the additive (C) is 60 ° C. or higher, preferably 65 ° C. or higher, more preferably 67 ° C. or higher, further preferably 69 ° C. or higher, further preferably 70 ° C. or higher, particularly preferably 73 ° C. or higher, and particularly preferably 75 ° C. The above is the most preferable. The higher the melting point of the additive (C), the easier it is to suppress the migration to the resist layer. However, if the melting point is too high, the viscosity may increase too much and affect the coatability of the conductive composition. In addition, if the melting point is too high, the solubility in water tends to decrease. The conductive film formed on the resist layer is finally dissolved in water and peeled off from the resist layer, but if the solubility in water is lowered, undissolved residue is generated at the time of peeling. From this point of view, the melting point of the additive (C) is preferably 300 ° C. or lower.
The melting point of the additive (C) is measured according to the method for measuring the melting point and melting range of chemical products in JIS K 0064: 1992. When a commercially available additive (C) is used, the catalog value may be used.

The additive (C) is not particularly limited as long as it has a melting point of 60 ° C. or higher and is a compound other than the conductive polymer (A), the solvent (B) and the basic compound (D), but is not particularly limited. Agents, polymer compounds (excluding conductive polymers (A), surfactants and basic compounds (D)), pigments, defoamers, UV absorbers, antioxidants, heat resistance improvers, leveling agents , Anti-sagging agent, matting agent, preservative and the like. Among these, a surfactant is preferable as the additive (C) from the viewpoint of improving the coatability when the conductive composition is applied to the surface of the base material or the resist layer.

Examples of the surfactant include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants and the like. Any one of these surfactants may be used alone, or two or more of these surfactants may be mixed and used in an arbitrary ratio.

Examples of anionic surfactants include sodium dialkyl sulfosuccinate, sodium octanate, sodium decanoate, sodium laurate, sodium myristate, sodium palmitate, sodium stearate, perfluorononanoic acid, and sodium N-lauroyl sarcosin. Sodium cocoyl glutamate, alpha sulfo fatty acid methyl ester salt, sodium lauryl sulfate, sodium myristyl sulfate, sodium laureth sulfate, sodium polyoxyethylene alkylphenol sulfonate, ammonium lauryl sulfate, lauryl phosphate, sodium lauryl phosphate, potassium lauryl phosphate, etc. Be done.

Examples of cationic surfactants include tetramethylammonium chloride, tetramethylammonium hydroxide, tetrabutylammonium chloride, dodecyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, and dodecyl chloride. Trimethylammonium, tetradecyltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, alkyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, benzalkonium chloride, benzal bromide Luconium, 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, dodecylaminomethyldimethylsulfopropyl betaine, octadecylaminomethyldimethylsulfopropyl betaine, cocamidopropyl betaine, cocamidopropyl hydroxysultaine, 2 Examples thereof include -alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, sodium lauroyl glutamate, potassium lauroyl glutamate, lauroylmethyl-β-alanine, lauryldimethylamine-N-oxide, and oleyldimethylamine N-oxide. ..

Examples of the nonionic surfactant include glycerin laurate, glycerin monostearate, sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkyl ether, pentaethylene glycol monododecyl ether, octaethylene glycol monododecyl ether, and poly. Oxyethylene alkylphenyl ether, octylphenol ethoxylate, nonylphenol ethoxylate, polyoxyethylene polyoxypropylene glycol, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene hexitan fatty acid ester, sorbitan fatty acid ester polyethylene glycol, laurate diethanolamide, oleic acid Examples thereof include diethanolamide, stearic acid diethanolamide, octyl glucoside, decyl glucoside, lauryl glucoside, cetanol, stearyl alcohol and oleyl alcohol.

In addition to the above, a water-soluble polymer having a nitrogen-containing functional group and a terminal hydrophobic group may be used as the nonionic surfactant. Unlike conventional surfactants, this water-soluble polymer has a surface-active ability due to a main chain portion (hydrophilic portion) having a nitrogen-containing functional group and a hydrophobic group portion at the end, and has an effect of improving coatability. Is high. Therefore, excellent coatability can be imparted to the conductive composition without using other surfactants in combination.

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 group and the like. Among these, an alkylthio group, an aralkylthio group and an arylthio group are preferable.
The number of carbon atoms of the terminal hydrophobic group is preferably 3 to 100, more preferably 5 to 50, and particularly preferably 7 to 30.
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 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 monomers). A compound having a chain structure and having a hydrophobic group at a site other than the repeating unit constituting the polymer is preferable.
Examples of the vinyl monomer having a nitrogen-containing functional group include acrylamide and its derivatives, a heterocyclic monomer having a nitrogen-containing functional group, and the like, 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, diacetoneacrylamide, 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-olefins.

The method for introducing the terminal hydrophobic group into the water-soluble polymer is not particularly limited, but it is usually convenient and preferable to introduce it by selecting a chain transfer agent at the time of vinyl polymerization. In this case, as the chain transfer agent, if a group containing a hydrophobic group such as an alkyl group, an aralkyl group, an aryl group, an alkylthio group, an aralkylthio group or an arylthio group is introduced into the terminal of the obtained polymer. There is no particular limitation. For example, when a water-soluble polymer having an alkylthio group, an aralkylthio group, or an arylthio group is obtained as a terminal hydrophobic group, a chain transfer agent having a hydrophobic group corresponding to these terminal hydrophobic groups, specifically, a thiol , Disulfide, thioether and the like are preferably used for vinyl polymerization.

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 2 to 1000, and particularly preferably 2 to 10 in one molecule. If the number of units of the main chain portion having a nitrogen-containing functional group is too large, the surface activity tends to decrease.

The higher the molecular weight of the surfactant, the higher the melting point tends to be.
When the surfactant is a polymer, the residual monomer in the surfactant can be reduced by purifying the surfactant, and the molecular weight of the surfactant tends to be high. As a method for purifying the surfactant, a reprecipitation method, a recrystallization method, and a solvent extraction method are effective.
The molecular weight of the surfactant is a polyethylene glycol-equivalent value measured by GPC.

Examples of the polymer compound include polyvinyl alcohol derivatives such as polyvinyl formal and polyvinyl butyral and modified products thereof, partially saponified or fully saponified polyvinyl alcohol and derivatives thereof, starch and modified products thereof (oxidized starch, phosphate esterified starch). , Cationic starch, etc.), cellulose derivatives (carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose and salts thereof, etc.), polyacrylamide, poly (Nt-butylacrylamide), polyacrylamide, polypropanesulfonic acid, etc. Acrylamides, polyvinylpyrrolidone, polyacrylic acid (salt), polyethylene glycol, 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 resin, water-soluble vinyl acetate acrylic copolymer resin, water-soluble polyester resin, water-soluble styrene maleic acid copolymer resin, water-soluble fluororesin and copolymers thereof Can be mentioned.

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

<Basic compound (D)>
The conductive composition may further contain the basic compound (D).
If the conductive composition contains the basic compound (D), it is considered possible to enhance the stability of the conductive polymer (A).

The basic compound (D) is not particularly limited as long as it is a compound having basicity, and for example, the following quaternary ammonium salt (d-1), basic compound (d-2), and basic compound (d) are used. -3) and the like.
Quadruple ammonium salt (d-1): A quaternary ammonium compound in which at least one of the four substituents bonded to the nitrogen atom is a hydrocarbon group having one or more carbon atoms.
Basic compound (d-2): A basic compound having one or more nitrogen atoms (excluding the quaternary ammonium salt (d-1) and the basic compound (d-3)).
Basic compound (d-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 (d-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 (d-1), examples of the hydrocarbon group bonded to the nitrogen atom of the quaternary ammonium ion include an alkyl group, an aralkyl group, an aryl group and the like.
Examples of the quaternary ammonium compound (d-1) include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, and the like. Examples thereof include benzyltrimethylammonium hydroxide.

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

In the basic compound (d-3), examples of the basic group include basic groups defined by Arrhenius base, Bronsted base, Lewis base and the like. Specific examples include ammonia and the like. The hydroxy group may be in a −OH state 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 and the like. Can be mentioned.
Examples of the basic compound (d-3) include 2-amino-1,3-propanediol, tris (hydroxymethyl) aminomethane, 2-amino-2-methyl-1,3-propanediol, and 2-amino-2. Examples thereof include -ethyl-1,3-propanediol, 3- [N-tris (hydroxymethyl) methylamino] -2-hydroxypropanesulfonic acid, and N-tris (hydroxymethyl) methyl-2-aminoethanesulfonic acid. ..

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

The basic compound (D) efficiently acts on the acidic groups in the conductive polymer (A) to easily form a salt. Therefore, even if the conductive composition is applied onto the resist layer and heat treatment such as prebaking treatment or PEB treatment is performed, it is considered that the basic compound (D) is unlikely to migrate to the resist layer. Therefore, the melting point of the basic compound (D) is not particularly limited, and may be lower than 60 ° C. or higher than 60 ° C.

From the viewpoint of further improving the coatability of the conductive composition, the content of the basic compound (D) is determined to be 0, with respect to 1 mol of the unit having an acidic group among the units constituting the conductive polymer (A). The equivalent of 1 to 1 mol is preferable, and the equivalent of 0.1 to 0.9 mol 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 more stable acidic groups in the conductive polymer (A).

<Manufacturing method of conductive composition>
The conductive composition can be obtained by mixing the above-mentioned conductive polymer (A), solvent (B), additive (C), and if necessary, basic compound (D).
For example, when the washed conductive polymer (A) produced by the above-mentioned method for producing the conductive polymer (A) is used, the washed conductive polymer (A) is in a solid state. Therefore, a solid conductive polymer (A) and a solvent (B) are mixed in advance to prepare a conductive polymer solution, and the obtained conductive polymer solution is added to the additive (C) and, if necessary, basic. Compound (D) can be added to obtain a conductive composition.

<Action effect>
As described above, when an additive such as a surfactant is melted by heat treatment, the melted additive is transferred from the conductive film to the resist layer side, and the resist layer in the unexposed portion is melted during development. The film of the resist layer may be reduced.
However, in the conductive composition of the present invention, since the melting point of the additive (C) is specified to be 60 ° C. or higher, even if the additive (C) melts, it is difficult to transfer to the resist layer. Therefore, particularly in the pattern forming method using a charged particle beam using a chemically amplified resist, the migration of the additive-derived component from the conductive film to the resist layer side is suppressed, and the influence of film reduction of the resist layer can be suppressed.

<Use>
The conductive composition of the present invention is suitable for antistatic use when drawing a charged particle beam. Specifically, the conductive composition of the present invention is applied to the surface of a resist layer of a pattern forming 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, for example, a capacitor, a transparent electrode, a semiconductor, or 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.
Example 1 is an example, and Examples 2 and 3 are comparative examples.

[Measurement / evaluation method]
<Evaluation of conductivity>
2.0 mL of the conductive composition was dropped onto a glass base material as a base material, and the coating film was formed by rotating and coating with a spin coater under the conditions of 2000 rpm × 60 seconds so as to cover the entire surface of the base material. Heat treatment was performed at 80 ° C. for 2 minutes on a hot plate to form a conductive film having a film thickness of about 30 nm on the substrate to obtain a conductor.
The surface resistance value [Ω / □] of the conductive film was measured by the 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)
Using a chemically amplified electron beam resist (hereinafter, abbreviated as "resist"), the amount of film loss 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 with a spin coater under the condition of 2000 rpm × 60 seconds, and then prebaked at 130 ° C. for 90 seconds on a hot plate. , The solvent was removed and a resist layer was formed on the substrate.
(2A) Film thickness measurement of resist layer 1: Part of the resist layer formed on the substrate is peeled off, and the stylus profilometer P-16 +, KLA-Tencor with the substrate surface as the reference position. The film thickness a [nm] of the initial resist layer was measured using (manufactured by Corporation).
(3A) Formation of film thickness: 2 mL of the conductive composition was dropped onto the resist layer, and the mixture was rotationally coated on a hot plate with a spin coater under the conditions of 2000 rpm × 60 seconds so as to cover the entire surface of the resist layer. The mixture was prebaked at 80 ° C. for 2 minutes to remove the solvent, and a conductive film having a film thickness of about 30 nm was formed on the resist layer.
(4A) PEB treatment: A substrate in which a conductive film and a resist layer are laminated is heated on a hot plate at 120 ° C. for 20 minutes in an air atmosphere, and the substrate in this state is heated in air at room temperature (25 ° C.) for 90 seconds. It was left still.
(5A) Washing with water: After rinsing the conductive film with 20 mL of water, the conductive film was rotated at 2000 rpm × 60 seconds with a spin coater to remove water on the surface of the resist layer.
(6A) Development: 20 mL of a developing solution consisting of a 2.38 mass% tetramethylammonium hadrooxide (TMAH) aqueous solution was added dropwise to the surface of the resist layer. After allowing to stand for 60 seconds, the mixture was rotated at 2000 rpm × 60 seconds with a spin coater to remove the developer on the surface of the resist layer, and the rotation was continued for 60 seconds to dry.
(7A) Measurement of resist layer film thickness 2: After peeling a part of the resist layer within 5 mm from the part where the resist layer was partially peeled in the above (2A), the resist after development using a stylus type step meter. The film thickness b [nm] of the layer was measured.
(8A) Calculation of film thickness reduction amount: The film thickness b value was subtracted from the film thickness a value 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 loss amount (hereinafter, referred to as “reference film loss amount”) d [nm] peculiar to each resist depending on the storage period after the resist layer is formed. This reference film loss amount d not caused by 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 film thickness of resist layer 1: The film thickness a [nm] of the initial resist layer was measured in the same manner as in (2A) above.
(3B) PEB treatment: The baking treatment was carried out in the same manner as in (4A) above, except that a base material having a laminated resist layer was used.
(4B) Development: Development was performed in the same manner as in (6A) above.
(5B) Measurement of resist layer film thickness 2: After peeling a part of the resist layer within 5 mm from the part where the resist layer was peeled in the above (2B), the resist layer after development using a stylus type step meter is used. The film thickness e [nm] was measured.
(6B) Calculation of film thickness reduction amount: The reference film thickness reduction amount d (d = a-e) of the resist layer was calculated by subtracting the value of the film thickness e from the value of the film thickness a.
The reference film loss amount d of the resist layer was 3 nm.

(Calculation of the amount of film loss of the resist layer caused by the components in the conductive film)
By subtracting the value of the reference film loss d of the resist layer from the value of the film loss c of the resist layer, the film loss f of the resist layer caused by the molten additive transferred from the conductive film to the resist layer [ nm] (f = cd) was calculated and evaluated according to the following evaluation criteria. The smaller the amount of film loss f, the more preferable.
A: The amount of film loss f is less than 5 nm.
B: The amount of film loss f is 5 nm or more and less than 20 nm.
C: The amount of film loss f is 20 nm or more.

[Conductive polymer (A)]
<Manufacturing of conductive polymer (A1)>
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 (oxidizing agent solution) was added dropwise to the obtained monomer solution at 10 ° C. After completion of the 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 solution in which the reaction product was precipitated (polymerization step).
The obtained reaction solution is filtered through a centrifugal filter, the precipitate (reaction product) is collected, the reaction product is washed with 1 L of methanol, and then dried to obtain a powdery conductive polymer (A1). Was obtained (purification step).

[Additives other than basic compounds (C)]
<Additives (C1) to (C3)>
As the additive (C1), a completely saponified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., "PVA-103", melting point 150 to 230 ° C.) was used.
As the additive (C2), polyoxyethylene lauryl ether (manufactured by Kao Corporation, "Emargen 130K", melting point 37 ° C.) was used.
As the additive (C3), sorbitan laurate (manufactured by Kao Corporation, “Leodor SP-10”), melting point 13 ° C.) was used.
The melting points of the additives (C1) to (C3) are catalog values.

[Example 1]
A mixture of 1.9 parts by mass of the conductive polymer (A1), 94.0 parts by mass of water and 4.0 parts by mass of isopropyl alcohol (IPA) as the solvent (B), and 0.1 parts by mass of the additive (C1). A conductive composition was obtained.
The obtained conductive composition was evaluated for conductivity and subjected to a film loss test. These results are shown in Table 1.

[Example 2]
A mixture of 1.9 parts by mass of the conductive polymer (A1), 94.0 parts by mass of water and 4.0 parts by mass of isopropyl alcohol (IPA) as the solvent (B), and 0.1 parts by mass of the additive (C2). A conductive composition was obtained.
The obtained conductive composition was evaluated for conductivity and subjected to a film loss test. These results are shown in Table 1.

[Example 3]
A mixture of 1.9 parts by mass of the conductive polymer (A1), 94.0 parts by mass of water and 4.0 parts by mass of isopropyl alcohol (IPA) as the solvent (B), and 0.1 parts by mass of the additive (C3). A conductive composition was obtained.
The obtained conductive composition was evaluated for conductivity and subjected to a film loss test. These results are shown in Table 1.

As is clear from Table 1, Example 1 using the additive (C1) having a melting point of 60 ° C. or higher is compared with Examples 2 and 3 using the additives (C2) and (C3) having a melting point of less than 60 ° C. The amount of film loss was small.

The conductive composition of the present invention can form a conductive film having little influence on the resist layer, and is useful as an antistatic material when drawing a charged particle beam.

Claims (2)

A conductive composition containing a conductive polymer having an acidic group, a solvent, and an additive other than a basic compound.
A conductive composition having a melting point of 60 ° C. or higher for the additive. The conductive composition according to claim 1, which is used for preventing static electricity when drawing a charged particle beam.