JP2018142598A - Organic insulation thin film, organic transistor, capacitor, and manufacturing method of organic insulation thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic insulation thin film having an nm-order film thickness and an excellent insulation property, an organic transistor and a thin film capacitor using the thin film, and a manufacturing method of the organic insulation thin film.SOLUTION: An organic insulation thin film is made of a bride body of an ion resin, and has a thickness of 5nm or more and less than 1 μm and a leak current density at an electric field intensity of 2.5MV/cm of 10A/cmor less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic insulating thin film, an organic transistor, a capacitor, and a method for manufacturing an organic insulating thin film.

  Since organic transistors have unique features such as light weight and flexibility, they are expected as key devices for realizing next-generation flexible electronics. For example, pixel switching elements constituting displays such as liquid crystal displays It can also be used for signal driver circuit elements, memory circuit elements, and the like. However, in practical use, it is necessary to manufacture a transistor that can be manufactured by a low-cost process and can be driven with low power consumption and low voltage with a high yield. In order to realize such an element, there is a need for a technique capable of forming a gate insulating film that is thin but excellent in insulation properties and has a large gate capacity by a simple wet process using an organic material.

  Known wet processes include spin coating, spray coating, dip coating, casting, bar coating, and other printing methods such as screen printing and ink jet. For example, it has been proposed to use a fluorine-based polymer insulating layer formed by spin coating as a gate insulating film of an organic field effect transistor (Non-patent Document 1).

Xiaoyang Cheng et al., Chem. Mater., 2010, 22, 1559-1566

  However, it is difficult to produce a thin film on the order of nm with no pinholes by a conventional coating method or printing method. In addition, the conventional coating method and printing method have poor throwing power, and it is difficult to form a thin film having a uniform thickness according to the shape of the object to be coated. For example, the film thickness tends to be thin at the edge portion. . There is a problem that these pinholes and edge portions cause insulation failure.

  Accordingly, the present invention solves the above-mentioned problems, and provides an organic insulating thin film having a film thickness on the order of nm and excellent in insulating properties, an organic transistor and a capacitor using the same, and a method for manufacturing the organic insulating thin film The purpose was to provide.

In the course of studying the characteristics of an organic resin film formed by electrodeposition, the present inventors have found that an organic resin film having a thickness on the order of nm has excellent insulating properties, and completed the present invention. Is.
That is, the organic insulating thin film of the present invention is made of a crosslinked ionic resin, has a thickness of 5 nm or more and less than 1 μm, and has a leak current density of 10 ⁻⁸ A / cm ² or less at an electric field strength of 2.5 MV / cm. It is characterized by being.

The organic transistor of the present invention is an organic transistor having a gate electrode, a gate insulating layer, a source electrode and a drain electrode, and an organic semiconductor layer on an insulating substrate, wherein the gate insulating layer is made of an ionic resin. It consists of an organic insulating thin film made of a crosslinked body, the thickness of the organic insulating thin film is 5 nm or more and less than 1 μm, and the leakage current density at an electric field strength of 2.5 MV / cm is 10 ⁻⁸ A / cm ² or less. It is characterized by that.

The capacitor of the present invention is a capacitor having a first electrode, a second electrode, and an insulating layer formed between the first electrode and the second electrode, wherein the insulating layer is ionic. It consists of an organic insulating thin film made of a crosslinked resin, the thickness of the organic insulating thin film is 5 nm or more and less than 1 μm, and the leakage current density at an electric field strength of 2.5 MV / cm is 10 ⁻⁸ A / cm ² or less. It is characterized by that.

  Moreover, the organic insulating thin film of this invention can be manufactured using the following manufacturing methods. That is, in the method for producing an organic insulating thin film of the present invention, the precursor of the organic insulating thin film containing the ionic resin and the cross-linking agent by an electrodeposition method on an electrodeposit having at least a surface conductive. And a step of heat-treating the precursor.

  ADVANTAGE OF THE INVENTION According to this invention, the organic insulating thin film which has the film thickness of nm order and was excellent in insulation, the organic transistor and capacitor using the same, and the manufacturing method of an organic insulating thin film can be provided.

It is a schematic cross section which shows an example of the structure of the capacitor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the structure of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is a schematic cross section which shows an example of the manufacturing process of the organic transistor using the organic insulating thin film of this invention. It is one Example of this invention, and is a graph which shows the relationship between an applied voltage and the film thickness of the organic insulating thin film of this invention. It is one Example of this invention, and is a graph which shows the relationship between the dielectric constant and frequency of the organic insulating thin film of this invention. It is one Example of this invention and is a graph which shows the relationship between an applied voltage and leakage current density. It is an Example of this invention and is a figure which shows the cross-sectional profile of the organic insulating thin film of this invention. It is the elements on larger scale of FIG. It is an Example of this invention, and is a photograph which shows the structure of the organic transistor array using the organic insulating thin film of this invention. It is an Example of this invention, and is a graph which shows the transfer characteristic of the organic transistor using the organic insulating thin film of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The organic insulating thin film of the present invention comprises a crosslinked ionic resin, has a thickness of 5 nm or more and less than 1 μm, and has a leak current density of 10 ⁻⁸ A / cm ² or less at an electric field strength of 2.5 MV / cm. It is characterized by that.

  The ionic resin used in the present invention is a resin having a positively or negatively charged ionic group that is at least partially dissociated in an aqueous solution, and includes a positively charged cationic group (hereinafter referred to as a cation). A resin having a negatively charged anionic group (hereinafter referred to as an anionic resin).

  Moreover, the crosslinked body of an ionic resin is a structure crosslinked through a chemical bond generated by a reaction between a reactive group of an anionic resin or a cationic resin and a crosslinking agent.

  An anionic resin is resin which contains the carboxyl group as an anionic group at least, and also contains the hydroxyl group as a reactive group which reacts with a crosslinking agent. Specific examples include carboxyl group-containing vinyl resins such as (meth) acrylic acid resins and maleic acid resins, polyester resins, polybutadiene resins, urethane resins, polyamide resins, polyimide resins, or a plurality thereof. Can be mentioned. Preferably, it is a carboxyl group-containing vinyl resin.

  As the carboxyl group-containing vinyl resin, a copolymer of a carboxyl group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer is preferable. As the carboxyl group-containing vinyl monomer, one or more of acrylic acid, α-chloroacrylic acid, methacrylic acid, itaconic acid, maleic anhydride, maleic acid, fumaric acid, crotonic acid, citraconic acid, mesaconic acid, etc. They can be used in combination. Acrylic acid or methacrylic acid is preferred. Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxy Butyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate and the like can be used singly or in combination. 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate is preferred. The carboxyl group-containing vinyl resin is a copolymer of the carboxyl group-containing vinyl monomer and the hydroxyl group-containing vinyl monomer so that the acid value is in the range of 15 to 160 and the hydroxyl value is in the range of 20 to 250. A polymerized product can be used. In addition to the carboxyl group-containing vinyl monomer and the hydroxyl group-containing vinyl monomer, the carboxyl group-containing vinyl resin may be methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n -Propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, hexyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, heptyl acrylate, heptyl methacrylate, styrene, α -Alkyl styrene, α-chlorostyrene, vinyl toluene, acrylonitrile, vinegar One or more monomers such as vinyl acid may be included.

  On the other hand, the cationic resin contains at least an amino group such as a primary amino group, a secondary amino group, and a tertiary amino group as a cationic group, or a quaternary ammonium base, and further includes a crosslinking agent component. It is a resin containing a hydroxyl group as a reactive group to react. Specific examples include amino group-containing vinyl resins such as cationic (meth) acrylic resins, amine-added epoxy resins, and the like. Preferably, it is a cationic (meth) acrylic resin.

  As the amino group-containing vinyl resin, a copolymer of an amino group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer is preferable. Examples of amino group-containing vinyl monomers include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, Nt-butylaminoethyl (meth) acrylate, and N, N-dimethyl. Aminopropyl (meth) acrylate or the like can be used alone or in combination. N, N-dimethylaminoethyl (meth) acrylate or N, N-diethylaminoethyl (meth) acrylate is preferable. Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxy Butyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate and the like can be used singly or in combination. 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate is preferred. In addition to the amino group-containing vinyl monomer and the hydroxyl group-containing vinyl monomer, the amino group-containing vinyl resin may be methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n -Propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, hexyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, heptyl acrylate, heptyl methacrylate, styrene, α -Alkyl styrene, α-chlorostyrene, vinyl toluene, acrylonitrile, vinyl acetate, etc. One or more monomers may be included.

  The amine-added epoxy resin is obtained by reacting an amine compound such as a primary amine, secondary amine, tertiary amine, or polyamine with an epoxy resin to introduce a cationic group into the epoxy resin. Examples of the primary amine include methylamine, ethylamine, n-propylamine, isopropylamine, monoethanolamine, n-propanolamine, and isopropanolamine. Examples of secondary amines include diethylamine, diethanolamine, di-n-propanolamine, diisopropanolamine, N-methylethanolamine, N-ethylethanolamine and the like. Examples of the tertiary amine include triethylamine, triethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, N, N-diethylethanolamine, N-ethyldiethanolamine and the like. Examples of the polyamine include ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminoethylamine, dimethylaminopropylamine and the like. Preferred amine compounds are secondary amines or tertiary amines.

  As a crosslinking agent used for an anionic resin or a cationic resin, a compound containing a plurality of reactive groups capable of reacting with a hydroxyl group contained in an anionic resin or a cationic resin can be used. Specific examples include amino resins and blocked isocyanate compounds.

  As the amino resin, at least one selected from the group consisting of melamine resin, benzoguanamine resin, and urea resin can be used. This is because the crosslinking reaction proceeds by a condensation reaction between the amino group of the amino resin and the hydroxyl group contained in the anionic resin. As the amino resin, a melamine resin is preferable. Examples of the melamine resin include a methylol melamine resin obtained by methylolating melamine with formaldehyde, an alkoxy methylol melamine resin obtained by alkoxylating the methylol group with a monoalcohol, the above methylol melamine resin having an imino group, or the above alkoxy methylol melamine resin. Can be mentioned. Examples of the monoalcohol used in the alkoxylation include one or more of methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol and the like. Preferred melamine resins include at least one selected from the group consisting of methoxymethylol melamine resins, butoxymethylol melamine resins, methoxybutoxy mixed methylol melamine resins, imino group-containing methoxymethylol melamine resins, and imino group-containing butoxymethylol melamine resins. Can be mentioned.

  The blocked isocyanate compound is an isocyanate compound in which free isocyanate groups are blocked with a blocking agent. In the blocked isocyanate compound, when the blocking agent is dissociated by heating, the isocyanate group reacts with the hydroxyl group of the anionic resin, so that a crosslinking reaction proceeds. At this time, a urethane bond is formed by the reaction between the isocyanate group and the hydroxyl group. Isocyanate compounds are compounds having two or more isocyanate groups in one molecule, such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate. Aromatic, aliphatic or alicyclic isocyanate compounds such as bis (isocyanatomethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, biurets, these isocyanurates, trimethylolpropane and the above An adduct that is a reaction product with the isocyanate compound may be used. Preferred isocyanate compounds are aliphatic or alicyclic isocyanate compounds, biurets, these isocyanurates, and adducts that are a reaction product of trimethylolpropane and these isocyanate compounds. A preferred aliphatic or alicyclic isocyanate compound is tetramethylene diisocyanate, hexamethylene diisocyanate, or isophorone diisocyanate.

  Examples of the blocking agent used for the blocked isocyanate compound include lactam compounds such as ε-caprolactam and γ-butyrolactam, oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime, phenol, para-t-butylphenol, cresol and the like. Phenol compounds, pyrazole compounds such as 3,5-dimethylpyrazole and 3,5-diisopropylpyrazole, active methylene compounds such as diethyl malonate, ethyl acetoacetate and acetylacetone, aliphatics such as n-butanol and 2-ethylhexanol Ethers such as alcohols, aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, etc. Specific examples include alcoholic compounds. Preferred blocking agents are lactam compounds, oxime compounds, or pyrazole compounds, more preferably ε-caprolactam, γ-butyrolactam, methyl ethyl ketoxime, cyclohexanone oxime, or 3,5-dimethylpyrazole.

  In the present invention, from the viewpoint of securing higher insulation, as a preferred combination of an ionic resin and a crosslinking agent, in the case of anion electrodeposition, from the viewpoint of securing better insulation, a (meth) acrylic acid resin And melamine resin. The (meth) acrylic acid resin contains acrylic acid or methacrylic acid as the carboxyl group-containing vinyl monomer, and 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate is preferred as the hydroxyl group-containing vinyl monomer. . The melamine resin includes methoxymethylol melamine resin, butoxymethylol melamine resin, methoxybutoxy mixed methylol melamine resin, imino group-containing methoxymethylol melamine resin, imino group-containing butoxymethylol melamine resin, and imino group-containing methoxybutoxy mixed methylol melamine resin. At least one selected from the group, more preferably a methoxybutoxy mixed methylolmelamine resin. In the case of cationic electrodeposition, from the viewpoint of ensuring better insulation, a cationic (meth) acrylic resin and a melamine resin. The cationic (meth) acrylic resin preferably contains N, N-dimethylaminoethyl (meth) acrylate or N, N-diethylaminoethyl (meth) acrylate as the amino group-containing vinyl monomer. The monomer preferably contains 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate. The melamine resin includes methoxymethylol melamine resin, butoxymethylol melamine resin, methoxybutoxy mixed methylol melamine resin, imino group-containing methoxymethylol melamine resin, imino group-containing butoxymethylol melamine resin, and imino group-containing methoxybutoxy mixed methylol melamine resin. At least one selected from the group, more preferably an imino group-containing methoxybutoxy mixed methylolmelamine resin.

(Production method)
Next, the manufacturing method of the organic insulating thin film of this invention is demonstrated. The method for producing an organic insulating thin film of the present invention is a production method using an electrodeposition method, and includes the ionic resin and a cross-linking agent by an electrodeposition method on an electrodeposit having at least a surface having conductivity. The method includes a step of depositing a precursor of the organic insulating thin film (hereinafter referred to as an electrodeposition step) and a step of heat treating the precursor (hereinafter referred to as a heat treatment step).

  In the electrodeposition process, the working electrode and the counter electrode, which are electrodeposition bodies, are immersed in the electrodeposition liquid in the electrodeposition tank, and a voltage is applied for a predetermined time to crosslink the ionic resin in the electrodeposition liquid. An agent is deposited on the surface of the working electrode. In the case of anion electrodeposition, the working electrode is an anode, and in the case of cationic electrodeposition, the working electrode is a cathode.

  The electrodeposition liquid is obtained by dissolving or colloidally dispersing an ionic resin and a crosslinking agent in an aqueous solvent. Aqueous solvents include water as the main solvent, alcohols such as isopropyl alcohol, normal butanol, isobutanol, 2-ethylhexyl alcohol, benzyl alcohol, ethylene glycol isopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monotertiary butyl ether 0.1 to 10 parts by weight of propylene glycol ethers such as ethylene glycol ethers, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol monophenyl ether, or mixtures thereof Can do.

  When anion electrodeposition is performed, the above anionic resin is used. Moreover, when performing cationic electrodeposition, said cationic resin is used. Moreover, said amino resin and block isocyanate compound can be used for a crosslinking agent. The mixing ratio of the ionic resin and the crosslinking agent in the electrodeposition liquid is 40 to 90% by weight, preferably 50 to 80% by weight, based on the total solid content of the ionic resin and the crosslinking agent. . Moreover, a crosslinking agent is 60 to 10 weight%, Preferably it is 50 to 20 weight%.

  In order to dissolve or disperse the anionic resin in an aqueous solvent, it is necessary to neutralize at least a part of the carboxyl group that is an anionic group of the anionic resin with a base. The bases include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, tributylamine and other alkylamines, monoethanolamine, diethanolamine , Alkanolamines such as triethanolamine, mono (2-hydroxypropyl) amine, di (2-hydroxypropyl) amine, tri (2-hydroxypropyl) amine, dimethylaminoethanol, diethylaminoethanol, ethylenediamine, propylenediamine, Alkylene polyamines such as diethylenetriamine and triethylenetetramine, ethyleneimine, propyleneimine, etc. Alkylene imines, piperazine, morpholine, pyrazine, organic amine and sodium hydroxide such as pyridine, or an inorganic base such as potassium hydroxide. These bases may be added so that the neutralization rate is 30 to 90% with respect to the carboxyl group.

  In the case of a cationic resin, for neutralization of the cationic group, organic acids such as formic acid, acetic acid, propionic acid, lactic acid, butyric acid, 2-ethylbutanoic acid and octylic acid, and inorganic acids such as sulfuric acid and phosphoric acid are used. Can be used. Preferably, it is acetic acid or lactic acid. These acids may be added so that the neutralization rate is 30 to 90% with respect to the cationic group.

  The molecular weights of the anionic resin and the cationic resin are 10,000 to 100,000, preferably 15,000 to prevent the flow of the resin component after the precipitation and improve the dispersion stability of the electrodeposition liquid. Preferably it has a weight average molecular weight of 60,000. Here, the weight average molecular weight is a molecular weight in terms of polystyrene obtained from measurement by gel permeation (GPC) method.

  In addition, a viscosity modifier, a dispersant, an additive such as a surface modifier for maintaining the surface smoothness of the precipitate, a curing catalyst for accelerating the crosslinking reaction, etc. are added to the electrodeposition liquid as necessary. May be.

  As described above, the electrodeposition liquid for anion electrodeposition preferably includes a (meth) acrylic acid resin as an ionic resin and a melamine resin as a crosslinking agent. Examples of such electrodeposition liquids include electrodeposition liquids SR-A-303, SR-A-304, SR-A-309 and the like available from Honey Kasei. The electrodeposition liquid SR-A-303 is a (meth) acrylic acid resin in which the anionic resin is a copolymer of a carboxyl group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer, and the melamine resin is It is a methoxybutoxy mixed methylol melamine resin. The concentrations of the anionic resin and melamine resin are 70% by weight and 30% by weight, respectively, with respect to the total solid content in the electrodeposition solution. SR-A-304 is different in that an imino group-containing methoxybutoxy mixed methylol melamine resin is used as a melamine resin, and SR-A-309 has a neutralization rate of SR-A-303 with a base of 80%. In contrast, the neutralization rate is 30%.

  Moreover, as an electrodeposition liquid for cationic electrodeposition, as described above, a liquid containing a cationic acrylic resin as an ionic resin and a melamine resin as a crosslinking agent is preferable. As an example of such an electrodeposition liquid, there can be mentioned an electrodeposition liquid SR-C-200 available from Honey Chemicals. The electrodeposition liquid SR-C-200 is a cationic acrylic resin in which the cationic resin is a copolymer of an amino group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer, and the melamine resin contains an imino group. It is a methoxybutoxy mixed methylol melamine resin. The concentrations of the cationic resin and melamine resin are 70% by weight and 30% by weight, respectively, with respect to the total solid content in the electrodeposition solution.

  The temperature of the electrodeposition liquid during electrodeposition is 0 ° C to 28 ° C, preferably 5 ° C to 28 ° C, more preferably 10 ° C to 26 ° C. By maintaining the temperature within the range of 0 ° C. to 28 ° C., the viscosity of the organic insulating thin film precursor is prevented from decreasing, and the organic insulating thin film precursor is redissolved or redispersed in the electrodeposition liquid. Can be suppressed.

  The applied voltage and application time during electrodeposition can be appropriately set according to the size and shape of the adherend, the distance between the counter electrodes (distance between electrodes), the type of electrodeposition liquid, etc. In the case of anion electrodeposition, from the viewpoint of obtaining an organic insulating thin film having a thickness of 1 to 100 V, more preferably 1 to 50 V, more preferably 1 to 10 V, and more preferably 1 to 10 V, and the application time is 1 to 900 seconds, preferably 1 to 200 seconds. In the case of cationic electrodeposition, the applied voltage during electrodeposition is 1 to 50 V, preferably 1 to 10 V, and the application time is 1 to 900 seconds, preferably 1 to 200 seconds.

  After the electrodeposition, the electrodeposit including the organic insulating thin film precursor is washed with water and subjected to a heat treatment step. In the heat treatment step, heating is performed at 100 ° C. to 200 ° C., preferably 120 ° C. to 190 ° C. for 1 to 60 minutes in an air atmosphere. By this heat treatment, the crosslinking reaction proceeds and an organic insulating thin film is formed. The thickness of the organic insulating thin film is 5 nm or more and less than 1 μm.

The organic insulating thin film of the present invention can be made thinner by using an electrodeposition method, compared to the case where other wet processes such as a spin coating method are used, and the surface smoothness and adhesion can be reduced. It becomes possible to produce a thin film having excellent turning ability. Furthermore, the organic insulating thin film of the present invention has excellent insulating properties, and the leakage current density at an electric field strength of 2.5 MV / cm is 1 × 10 ⁻⁸ A / cm at room temperature (20 ± 5 ° C.). ² or less, preferably 3 × 10 ⁻⁹ A / cm ² or less. Note that “the throwing power is excellent” means that the difference in film thickness at each part of the electrodeposit is small and the film thickness is uniform.

  As described above, since the organic insulating thin film of the present invention has high insulating properties, it can be used as an insulating film in an electronic device. For example, as described below, it can be used for capacitor insulating films, organic transistor gate insulating films, LSI interlayer insulating films, and the like.

(Capacitor)
The organic insulating thin film of the present invention can be used as an insulating film of a capacitor. FIG. 1 is a schematic cross-sectional view showing an example of the structure of the capacitor. The capacitor 1 includes an insulating substrate 2, a lower electrode 3 formed on the insulating substrate 2, an insulating film 4 formed on the lower electrode 3, and a pair of upper electrodes 5 formed on the insulating film 4. , 6. Metals such as gold, silver, copper, and aluminum can be used for the upper electrode and the lower electrode.

The organic insulating thin film of the present invention has a leak current density of 10 ⁻⁸ A / cm ² or less at an electric field strength of 2.5 MV / cm, and can be thinned to the order of nm. Since the capacitance is inversely proportional to the film thickness, a high capacitance can be obtained while ensuring sufficient insulation even when used for an insulating film of a capacitor.

  The capacitor of the present invention can be used, for example, as an insulating film of an on-chip capacitor manufactured in the same manner as a transistor in an electronic circuit, and can be used for a memory circuit, a display matrix, a capacitive sensor array, and the like. . In particular, it is suitable as a capacitive element for display because of the high transmittance of the material.

(Organic transistor)
The organic insulating thin film of the present invention can be used as a gate insulating film of an organic transistor. The structure of the organic transistor is not particularly limited as long as it is a thin film transistor in which at least three electrodes of a gate electrode, a source electrode, and a drain electrode, a gate insulating layer, and an organic semiconductor layer are formed on a substrate. FIG. 2 is a schematic cross-sectional view showing an example of the structure of an organic transistor using the organic insulating thin film of the present invention as a gate insulating film. The organic transistor 10 includes a substrate 11, a gate electrode 12 formed on the substrate 11, a gate insulating film 13 formed on the gate electrode 12, an organic semiconductor layer 14 formed on the gate insulating film 13, A source electrode 15 and a drain electrode 16 are formed separately on the organic semiconductor layer 14. The organic semiconductor layer 14 forms a channel region, and the current flowing between the source electrode 15 and the drain electrode 16 can be controlled by the voltage applied to the gate electrode 12. The organic insulating thin film of the present invention has a leak current density of 10 ⁻⁸ A / cm ² or less at an electric field strength of 2.5 MV / cm. Therefore, when used as a gate insulating film, it is possible to ensure sufficient insulation even if it is thin. Furthermore, since the film thickness can be made thinner than when formed by a coating method such as a spin coating method, the gate capacitance can be increased.

  Hereinafter, the manufacturing method of the organic transistor of this invention is demonstrated with reference to FIG. 3A-FIG. 3L.

(Gate electrode formation process)
Using a photolithography method and a lift-off process, a metal film is formed on the substrate 11, and further patterned to form the gate electrode 12 (FIG. 3A). Glass, plastic film, or the like can be used for the substrate. As the conductive material used for the gate electrode, a metal material such as gold, silver, platinum, nickel, chromium, or aluminum, or a conductive paste such as a silver paste can be used. For the gate electrode, not only a method of depositing and patterning a metal film, but also a method of forming by a printing method can be used. Note that the same conductive material as that of the gate electrode can be used for a source electrode and a drain electrode described later.

(Gate insulation film formation process)
Electrodeposition and heat treatment are performed using the gate electrode as an electrodeposit, and a gate insulating film 13 made of an electrodeposition film is formed (FIG. 3B). Electrodeposition can be performed using the above-described electrodeposition liquid and electrodeposition method.

(Organic semiconductor layer formation process)
An organic semiconductor layer 14 is formed so as to cover the entire surface of the gate insulating film 13 (FIG. 3C). A known material can be used as the organic semiconductor. For example, acene derivatives such as naphthalene, anthracene, tetracene, pentacene, hexacene, heptacene, rubrene, and thienoacene derivatives such as dinaphtho [2,3-b: 2 ′, 3′-f] thieno [3,2-b] thiophene , Polythiophene derivatives, polyphenylene vinylene derivatives, polychenylene derivatives and the like. The organic semiconductor layer can be formed using a vapor phase method such as a vacuum evaporation method or a liquid phase method such as a spin coating method.

(Source electrode and drain electrode formation process)
Although the organic semiconductor layer is formed on the entire surface of the substrate, it is necessary to perform patterning that leaves the organic semiconductor layer only on the gate insulating film in order to perform element isolation of the transistor. The patterning is performed to form a source electrode and a drain electrode (FIGS. 3D to 3L). Specifically, first, an Au film 17 serving as a protective film for the organic semiconductor layer 14 is formed by vacuum deposition (FIG. 3D). Next, a photoresist 18 is applied and photolithography is performed (FIG. 3E). Next, wet etching of the Au film 17 and oxygen ashing of the organic semiconductor layer 14 are performed (FIGS. 3F and 3G). Next, the photoresist 18 is removed (FIG. 3H). Next, the Au film 19 for the source electrode and the drain electrode is formed by vacuum deposition (FIG. 3I). Next, a photoresist 20 is applied and photolithography is performed (FIG. 3J). Next, wet etching of the Au film 19 is performed (FIG. 3K). Next, the photoresist 20 is removed to obtain the organic transistor 10 (FIG. 3L).

  In addition, said manufacturing method is an example, The well-known various method used for manufacture of an organic transistor can be used except forming a gate insulating film using an electrodeposition method and heat processing.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

(Preparation of electrodeposition film I)
An Al film having a thickness of 100 nm was formed by electron beam evaporation on a sufficiently cleaned glass substrate (17 mm × 14 mm), and this was used as an anode. Next, the counter electrode composed of the anode and Pt was immersed in an electrodeposition solution (SR-A-303 manufactured by Honey Chemical Industries) in an electrodeposition bath. An anion electrodeposition was performed by applying a voltage in the range of 5 to 40 V between the anode and the counter electrode, and an electrodeposition film was formed on the surface of the Al film of the anode. The temperature of the electrodeposition solution was 23 ° C., the energization time was 100 seconds, and a 2450 source meter manufactured by Keithley was used as the power source. The electrodeposition film was washed with running water with pure water and then subjected to heat treatment (180 ° C., 30 minutes) to crosslink to obtain an organic insulating film. Electrodeposition and heat treatment were performed under the same conditions except that only the applied voltage was changed to obtain a plurality of organic insulating films having different film thicknesses.

  The film thickness of the obtained organic insulating film was measured using a stylus type step gauge (P-15 manufactured by KLA-Tencor Corporation). FIG. 4 is a graph showing the relationship between the applied voltage and the film thickness of the organic insulating film. It was confirmed that an organic insulating film having a submicron thickness can be produced with an applied voltage of 10 V or less.

(Capacitor production)
An Al film having a thickness of 100 nm is formed as an upper electrode by electron beam evaporation using a metal mask on the organic insulating film having a thickness of 73 nm prepared in the above-described electrodeposition film preparation I. A capacitor having a structure was produced. The shape of the upper electrode is a circle having a diameter of 1 mm and a diameter of 2 mm in plan view.

(Electric characteristics of capacitors)
1. Dielectric constant The impedance between the electrodes of the produced capacitor was measured in a frequency range of 100 Hz to 1 MHz at room temperature (23 ° C.) using a chemical impedance meter 3532-80 manufactured by Hioki Electric Co., Ltd. FIG. 5 shows the frequency dependence (dielectric dispersion) of the dielectric constant of the organic insulating film. It was confirmed that the dielectric constant was in the range of 3.2 to 3.5 in the frequency range of 100 Hz to 1 MHz, the dielectric dispersion was relatively small, and the insulation was excellent in a wide frequency range.

2. Insulation Next, a voltage of 0 to 200 V was applied between the upper electrode and the lower electrode, and the leakage current density was measured. The results are shown in FIG. The electric field strength did not cause breakdown until about 2.5 MV / cm, and had high breakdown electric field strength. Further, the leakage current density was as small as 10 ⁻⁹ A / cm ² or less, and excellent characteristics as an insulating film were exhibited.

For comparison, a capacitor using a resin film formed by spin coating as an insulating layer was manufactured. As the resin film, polymethyl methacrylate (PMMA) manufactured by Sigma-Aldrich Japan was used. The film thickness is 56 μm. When the leakage current density at an electric field strength of 2.5 MV / cm was measured, it was 1 μA / cm ² or more.

(Preparation of electrodeposition film II)
An Al film having a thickness of 60 nm and a width of 30 μm was formed on a glass substrate by electron beam evaporation using a photolithography method and a lift-off process. Using this as an anode, electrodeposition and heat treatment were carried out under the same conditions as in the case of electrodeposition film preparation I to obtain an organic insulating thin film.

  The film thickness of the obtained organic insulating film was measured using the stylus type step meter. FIG. 7 shows a cross-sectional profile of the obtained organic insulating film. Further, a partially enlarged view of the step portion of the Al film in FIG. 7 is shown in FIG. The thickness of the organic insulating film on the side wall portion of the Al film was almost uniform and had excellent throwing power. In the figure, “Polymer” indicates a deposited electrodeposition film, and “Al” indicates an Al film.

(Production of organic transistors)
A gate electrode was produced by patterning an Al film formed by vacuum deposition on a glass substrate having a size of 30 mm × 25 mm using a photolithography method and a lift-off process. Using this gate electrode as an electrodeposition body, anion electrodeposition and heat treatment were performed under the same conditions as in the case of electrodeposition film preparation I to obtain a gate insulating film (film thickness: 40 nm) made of an organic insulating thin film. . Next, dinaphtho [2,3-b: 2 ′, 3′-f] thieno [3,2-b] thiophene (DNTT) was formed as an organic semiconductor layer by vacuum deposition. Here, the organic semiconductor layer is formed over the entire surface of the substrate. However, in order to perform element isolation of the transistor, it is necessary to perform patterning that leaves the organic semiconductor layer only on the gate insulating film. Therefore, after forming Au as a protective film for the organic semiconductor layer by vacuum deposition, photolithography using a fluorine-based photoresist, followed by wet etching of Au and oxygen ashing of the organic semiconductor layer were performed. OScOR2312 manufactured by Orthogonal was used for the fluorine-based photoresist, and AURUM S-50790 manufactured by Kanto Chemical Co. was used for the wet etching of Au. Thereafter, similarly, by using a photolithography method using a fluorine-based photoresist and a wet etching process, an Au film formed on the organic semiconductor layer by a vacuum deposition method is patterned, so that the channel length is 10 μm and the channel width is A source electrode and a drain electrode were prepared so as to be 200 μm. Thereby, an organic transistor array (50 × 18) was produced.

FIG. 9 shows a photograph of the produced organic transistor array, and the graph of FIG. 10 shows the transfer characteristics of the obtained organic transistor. Measurements of the transmission characteristic, the drain voltage _{V D} and -2V, the gate voltage _{V G} was scanned from -2V to 1V, the gate voltage _{V G} - was carried out by measuring the drain current _{I D. Further,} in the graph between the ^{(I D) 1/2} and the gate voltage _{V G,} was determined threshold voltage from the intersection of the extension line and the _{V G} axis of the straight section. In Figure 10, ● mark indicates the drain current _{I D,} ■ mark denotes the gate current _{I G,} ▲ mark indicates the _(I ^{D) 1/2.}

Gate current I _G is about several pA, while extremely thin insulating film with a thickness sufficiently insulation was found to be secured. Further, the threshold voltage is −1V, and driving with a low voltage is possible. Although it produced a total of 886 pieces of similar organic transistor, both the gate current I _G is not more than several hundred pA, showed high yield.

  In the conventional electronic device manufacturing process, a large-scale facility for processing inorganic materials such as silicon at a high temperature or in vacuum is required. On the other hand, since the organic insulating thin film of the present invention can be produced by using an electrodeposition method which is one of wet processes, it is not necessary to use a large facility for processing at high temperature or in vacuum, and heat resistance Since it can be applied to a poor plastic material, it has an advantage that the degree of freedom of selection of the substrate material is large and the throwing power is also good. Therefore, it is useful as a technique capable of forming a uniform insulating thin film on a large-area substrate in a manufacturing process of an electronic device.

DESCRIPTION OF SYMBOLS 1 Capacitor 2 Insulating substrate 3 Lower electrode 4 Insulating film 5, 6 Upper electrode 10 Organic transistor 11 Substrate 12 Gate electrode 13 Gate insulating film 14 Organic semiconductor layer 15 Source electrode 16 Drain electrode 17 Au film 18 Photoresist 19 Au film 20 Photo Resist

Claims (6)

An organic insulating thin film comprising a cross-linked ionic resin, having a thickness of 5 nm or more and less than 1 μm, and a leakage current density of 10 ⁻⁸ A / cm ² or less at an electric field strength of 2.5 MV / cm.   The organic insulating thin film according to claim 1, wherein the ionic resin is a copolymer of a carboxyl group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer.   The organic insulating thin film according to claim 1 or 2, wherein the crosslinked body contains a crosslinking agent, and the crosslinking agent is a melamine resin or a blocked isocyanate compound. An organic transistor having a gate electrode, a gate insulating layer, a source electrode and a drain electrode, and an organic semiconductor layer on an insulating substrate,
The gate insulating layer is made of an organic insulating thin film made of a crosslinked ionic resin, the thickness of the organic insulating thin film is 5 nm or more and less than 1 μm, and the leakage current density at an electric field strength of 2.5 MV / cm is 10 ^{−. The} organic transistor which is ⁸ A / cm ² or less. A capacitor having a first electrode, a second electrode, and an insulating layer formed between the first electrode and the second electrode;
The insulating layer is made of an organic insulating thin film made of a cross-linked ionic resin, the thickness of the organic insulating thin film is 5 nm or more and less than 1 μm, and the leakage current density at an electric field strength of 2.5 MV / cm is 10 ^−8. A capacitor that is A / cm ² or less.   The method for producing an organic insulating thin film according to claim 1, wherein the precursor of the organic insulating thin film contains the ionic resin and a crosslinking agent by an electrodeposition method on an electrodeposited surface having conductivity at least on the surface. The manufacturing method of an organic insulating thin film including the process of depositing a body, and the process of heat-processing the said precursor.

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