KR101462526B1 - Organic semiconductor meterial, field-effect transistor, and manufacturing method thereof - Google Patents

Abstract

(식 (1) 중, R₁ 및 R₂는 각각 독립적으로 무치환 또는 할로겐 치환 C1-C36 지방족 탄화수소기를 나타냄).An organic semiconductor material comprising an electron-accepting compound having the following formula (1) and a cyano group dissolved and / or dispersed in at least one organic solvent:

(In the formula (1), R < 1 _> And R ₂ each independently represent an unsubstituted or halogen-substituted C 1 -C 36 aliphatic hydrocarbon group.

Description

FIELD-EFFECT TRANSISTOR AND MANUFACTURING METHOD THEREOF FIELD OF THE INVENTION [0001] The present invention relates to an organic semiconductor material,

The present invention relates to a field effect transistor including an organic thin film obtained by applying or printing an organic thin film semiconductor material, and drying the organic thin film semiconductor material, a method of manufacturing the same, and an organic semiconductor material used in the field effect transistor. More particularly, the present invention relates to a field effect transistor obtained from a semiconductor material comprising an organic heterocyclic compound and a specific additive, and a method for producing the same.

The field effect transistor generally has a structure in which a source electrode, a drain electrode, a gate electrode, and the like are formed through a semiconductor material on a substrate with an insulating layer interposed therebetween. At present, an inorganic semiconductor material centering on silicon is used for a field effect transistor. In particular, a thin film transistor formed on a substrate such as a glass substrate by using amorphous silicon is used for a display and the like. In addition to being used, it is widely used in switching devices and the like. In recent years, studies using an oxide semiconductor as a semiconductor material have been actively conducted. However, when such an inorganic semiconductor material is used, it is necessary to treat at a high temperature or a vacuum at the time of manufacturing a field effect transistor. As a substrate to be used, Plastic, and the like can not be used. Moreover, since a large amount of equipment investment and a large amount of energy are required for manufacturing, the cost is extremely high and the application range thereof is very limited.

On the other hand, a field effect transistor using an organic semiconductor material which does not require a high-temperature treatment at the time of manufacturing a field effect transistor is actively developed. If it can be applied to an organic semiconductor material, the field effect transistor can be manufactured by a low-temperature process, and the range of the usable substrate material is expanded. As a result, it becomes possible to manufacture a field effect transistor which is more flexible, light in weight, and hard to break. In addition, it is also possible to manufacture a large-area field effect transistor at a low cost by applying a solution containing an organic semiconductor material or by a printing method using an ink jet or the like in a manufacturing process of the field effect transistor.

However, conventionally, since many organic semiconductor materials used for a semiconductor material are hardly soluble in an organic solvent, inexpensive techniques such as coating and printing can not be used, and a semiconductor substrate of a relatively high cost, It is necessary to form a thin film on the substrate. At present, a device having a relatively high carrier mobility has been obtained by dissolving in an organic solvent, forming a film (film forming) and a field effect transistor by a coating method, but a device having a high mobility A field-effect transistor using an organic semiconductor excellent in durability has not been put to practical use, and development has been actively conducted to improve the suitability of each transistor.

A semiconductor device using an inorganic material such as silicon is generally treated with an oxidizing or reducing gas such as oxygen or hydrogen or an oxidizing or reducing liquid or the like to the organic semiconductor layer for the purpose of increasing or decreasing the carrier density in the film, It is necessary to induce the characteristic change by reduction. This is because the carrier density in the semiconductor layer is increased or decreased by adding a small amount of elements, atoms, molecules, and polymers to the semiconductor layer to change electrical conductivity, carrier polarity (p type-n type conversion), Fermi level, For example, by bringing a gas such as oxygen and hydrogen into contact with each other, by immersing it in a solution containing an acid or a Lewis acid, or by adding a halogen atom such as iodine or a metal atom such as sodium or potassium electrochemically A method of treating with an inorganic compound to be treated, and a method of preliminarily treating with an organic compound of an electron-accepting or electron-donating agent are known. These treatments may be performed in a process other than the semiconductor layer formation before or after the semiconductor layer is formed, co-evaporation may be carried out by vacuum evaporation, mixing in an atmosphere during semiconductor layer production, or acceleration of ions in vacuum to collide with the semiconductor layer Is generally used.

Patent Document 1 discloses a field effect transistor using an alkyl derivative of benzoseleno [3,2-b] [1] benzocelenophene and benzothieno [3,2-b] [1] benzothiophene.

Patent Document 2 discloses a field effect transistor using a mixed solution of an alkyl derivative of benzothieno [3,2-b] [1] benzothiophene and a polymer compound having a specific solubility parameter.

Patent Document 3 discloses a field-effect transistor using a material including an alkyl derivative of benzothieno [3,2-b] [1] benzothiophene and a polymer material.

Patent Document 4 discloses a technique of amplifying a current value by contacting iodine or a metal with a pentacene thin film.

Patent Document 5 discloses a technique of improving electrical conductivity by using a thin film formed by applying and drying a solution of a polyacene compound and excess iodine or butyllithium.

Patent Document 6 discloses a technique of previously changing a threshold voltage by laminating a polymer semiconductor after an electron-accepting or electron-donating compound is applied in advance.

Non-Patent Document 1 discloses a field effect transistor using an alkyl derivative of benzothieno [3,2-b] [1] benzothiophene.

Non-Patent Document 2 discloses a field effect transistor formed by surface selective precipitation using an alkyl derivative of benzothieno [3,2-b] [1] benzothiophene.

International Publication No. 2008/047896 International publication pamphlet Japanese Laid-Open Patent Publication No. 2009-267372 Japanese Patent Application Laid-Open No. 2009-283786 Japanese Unexamined Patent Publication No. 5-55568 Japanese Patent No. 4219807 Japanese Laid-Open Patent Publication No. 2009-266865

 J. Am. Chem. Soc. 2007, 129, 15732.  Applied Physics Letters, 94, 93307 (2009).

An object of the present invention is to provide an excellent field effect transistor having a printability capable of forming a thin film having a high uniformity by a small process while improving semiconductor characteristics such as reduction in threshold voltage while maintaining high carrier mobility .

Means for Solving the Problems As a result of intensive investigations to solve the above problems, the present inventors have found that a field effect transistor using an organic semiconductor material obtained by mixing a specific organic heterocyclic compound and an electron-accepting material having a specific substituent in an organic solvent as a semiconductor material is formed There is provided a practical field effect transistor having a printability capable of forming a thin film having high uniformity by a small process as well as improving semiconductor characteristics such as reduction in threshold voltage while maintaining a high carrier mobility The present invention has been completed.

That is,

(1) An organic semiconductor material comprising an electron-accepting compound having a cyano group and a compound represented by the following formula (1) dissolved and / or dispersed in at least one organic solvent:

(In the formula (1), R ₁ and R ₂ each independently represent an unsubstituted or halogen-substituted C 1 -C 36 aliphatic hydrocarbon group)

.

When a field effect transistor is formed using an organic semiconductor material in which the compound represented by the formula (1) and the electron-accepting compound having a cyano group are dissolved and / or dispersed in at least one organic solvent, a high carrier shift It is possible to provide a practical field effect transistor having excellent printability capable of forming a thin film having a high uniformity in a small number of steps as well as improving semiconductor characteristics such as reduction in threshold voltage while maintaining the degree of uniformity.

1A to 1D are schematic views showing an example of the structure of a field effect transistor of the present invention.

(Mode for carrying out the invention)

The present invention will be described in detail. The present invention relates to an organic semiconductor material in which an electron-accepting compound having a specific organic heterocyclic compound and a cyano group is dissolved and / or dispersed in at least one organic solvent, and a field effect transistor using the same and a method for manufacturing the same.

First, the compound represented by the above formula (1) will be described. In the above formula (1), R ₁ and R ₂ each independently represent an unsubstituted or halogen-substituted C 1 -C 36 aliphatic hydrocarbon group. The aliphatic hydrocarbon group is a saturated or unsaturated straight chain, branched chain or cyclic aliphatic hydrocarbon group, preferably a straight chain or branched chain aliphatic hydrocarbon group, more preferably a straight chain aliphatic hydrocarbon group. The carbon number is usually C1-C36, preferably C2-C24, more preferably C4-C20, and still more preferably C6-C12.

Specific examples of the linear or branched saturated aliphatic hydrocarbon group include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, octyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-heptyl, n-hexyl, N-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, docosyl, n-pentacosyl, n-octacosyl, 5- Heptacosyl, nonacosyl, n-triacontyl, dotriacontyl, hexatriacontyl, and the like can be given. Specific examples of the cyclic saturated aliphatic hydrocarbon group include cyclohexyl, cyclopentyl, adamantyl, and norbornyl. Specific examples of the linear or branched unsaturated aliphatic hydrocarbon group include vinyl, allyl, eicosadienyl, 11,14-eicosadienyl, geranyl (trans-3,7-dimethyl-2,6-octadiene- 1-yl), 4-pentenyl, 1-propynyl, 1-hexynyl, 1- Octynyl, 1-decynyl, 1-undecenyl, 1-dodecenyl, 1-tetradecynyl, 1-hexadecynyl, 1-nonadecynyl and the like.

Among straight-chain, branched-chain and cyclic aliphatic hydrocarbon groups, straight-chain or branched-chain aliphatic hydrocarbon groups are preferable, and straight-chain aliphatic hydrocarbon groups are particularly preferable.

The saturated or unsaturated aliphatic hydrocarbon group includes a saturated alkyl group, an alkenyl group having a carbon-carbon double bond, and an alkynyl group having a carbon-carbon triple bond, more preferably an alkyl group or an alkynyl group, Is an alkyl group. Examples of the aliphatic hydrocarbon residue include a combination of these saturated or unsaturated aliphatic hydrocarbon groups, that is, the case where both the carbon-carbon double bond and the carbon-carbon triple bond are contained in the aliphatic hydrocarbon group at the same time.

The halogen-substituted aliphatic hydrocarbon group means that any kind of halogen atom is substituted at any position of the aliphatic hydrocarbon group by an arbitrary number. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, preferably a fluorine atom, a chlorine atom and a bromine atom, more preferably a fluorine atom and a bromine atom. Specific examples of the halogen-substituted aliphatic hydrocarbon group include chloromethyl, bromomethyl, trifluoromethyl, pentafluoroethyl, n-perfluoropropyl, n-perfluorobutyl, n-perfluoropentyl, n- N-pentyldecyl, n-hexyldecyl, n-hexyldecyl, n-hexyldecyl, Fluoropropyl, and the like.

The compound represented by the above formula (1) can be synthesized by a known method described in, for example, Patent Document 1 and Non-Patent Document 1.

The method of purifying the compound represented by the formula (1) is not particularly limited, and known methods such as recrystallization, column chromatography and vacuum sublimation purification can be employed. If necessary, these methods may be used in combination.

Table 1 below shows specific examples of the compound represented by the formula (1).

The electron-accepting compound having a cyano group is an additive to be doped into an organic semiconductor material and is not particularly limited, but tetracyanoquinodimethane (abbreviated as TCNQ hereinafter) or a derivative thereof can be exemplified. Specifically, TCNQ, 2, 3,5,6-tetrafluorotetracyano-1,4-benzoquinodimethane (hereinafter abbreviated as F4-TCNQ), trifluoromethyl tetracyanoquinodimethane (CF3TCNQ), 2,5-difluoro (FTCNQ), fluorotetracyanoquinodimethane (FTCNQ), tetracyanoethylene (TCNE), 11,11,12,12-tetracyanoantho-2,6-quinodi Methane (TNAP) or quinodimethanes having a cyano group described in JP-A-2008-530773 are suitably used. Of these, TCNQ or F4-TCNQ are particularly preferred.

The organic semiconductor material of the present invention is obtained by dissolving or dispersing at least an electron-accepting compound having a cyano group and a compound represented by the formula (1) in an organic solvent. However, the compound represented by the formula (1) Several kinds of derivatives of one or both of the compound represented by the formula (1) and the electron-accepting compound having a cyano group may be mixed and used even if the compound contains one kind of the water-soluble compound. In the organic semiconductor material comprising an electron-accepting compound having a cyano group and a compound represented by the formula (1), the content of the electron-accepting compound having a cyano group to the compound represented by the formula (1) is usually 0.1 to 40 mass %, Preferably 0.1 to 20% by mass, and more preferably 0.1 to 10% by mass. When the content ratio exceeds 40 mass%, the characteristic value decreases due to the increase of the OFF current. When TCNQ or F4-TCNQ is used, the content is particularly preferably 10% by mass or less.

The organic semiconductor material of the present invention may be mixed with other organic semiconductor materials and various additives as necessary in order to improve the properties of the field effect transistor and impart other properties thereto, so long as the effect of the present invention is not impaired. Examples of the additives include viscosity modifiers, surface tension modifiers, leveling agents, penetrants, rheology modifiers, aligning agents, and dispersants.

The content of these additives is 0 to 30 mass%, preferably 0 to 20 mass%, more preferably 0 to 10 mass%, based on the total amount of the organic semiconductor material of the present invention.

The organic semiconductor material of the present invention is one in which the compound represented by the formula (1) and the electron-accepting compound are dissolved or dispersed in a solvent to improve the applicability of the organic semiconductor material to the printing process. The solvent which can be used is not particularly limited as long as the compound can be formed on a substrate, but an organic solvent is preferable, and a single organic solvent or a mixture of plural organic solvents may be used. Specific examples thereof include halogenated hydrocarbon solvents such as chloroform, methylene chloride and dichloroethane; Alcohol solvents such as methanol, ethanol, isopropyl alcohol and butanol; Fluorinated alcohol solvents such as octafluoropentanol and pentafluoropropanol; Ester solvents such as ethyl acetate, butyl acetate, ethyl benzoate and diethyl carbonate; Aromatic hydrocarbon solvents such as toluene, xylene, benzene, chlorobenzene, mesitylene, ethylbenzene, diethylbenzene, triethylbenzene, dichlorobenzene, chloronaphthalene, tetrahydronaphthalene, decalin and cyclohexylbenzene; Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; Amide solvents such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone; Ether solvents such as tetrahydrofuran and diisobutyl ether; Hydrocarbon solvents such as hexane, cyclohexane, octane, decane and tetraene; And nitrile solvents such as acetonitrile, propiononitrile, butyronitrile, and benzonitrile. These solvents may be used alone or in combination. The concentration of the compound represented by the formula (1) and the electron-accepting compound varies depending on the kind of the solvent and the film thickness of the semiconductor layer to be produced, but is 0.001 to 50 mass%, preferably 0.01 to 20 mass% %. The semiconductor material of the present invention may be dissolved or dispersed in the above-mentioned organic solvent, but in forming a more uniform thin film, it is preferable that the semiconductor material is dissolved as a homogeneous solution.

A field effect transistor (hereinafter abbreviated as FET) of the present invention has two electrodes, that is, a source electrode and a drain electrode, in contact with the semiconductor layer, and current flowing between the two electrodes is applied to the gate insulator layer To a voltage to be applied to the other electrode called a gate electrode. The field effect transistor includes the organic thin film.

Fig. 1 shows several aspects of the field effect transistor of the present invention, but the arrangement of each layer and the electrode can be appropriately selected depending on the application of the device. In FIG. 1, the same names are assigned to the same names.

Next, each constituent element of the field-effect transistor of the present invention shown in Fig. 1 will be described, but is not limited thereto.

It is necessary that the substrate 1 can be stored and maintained without peeling off each layer formed thereon. For example, insulating materials such as resin plates, resin films, paper, glass, quartz, and ceramics; A formation in which an insulating layer is coated on a conductive substrate such as a metal or an alloy; A material composed of various combinations of resins and inorganic materials, and the like can be used. Among them, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyamide, polyimide, polycarbonate, cellulose triacetate, polyetherimide and the like can be given as examples of commonly used resin films. When a resin film or paper is used, flexibility can be imparted to the semiconductor element, resulting in a flexible and lightweight, and practicality is improved. The thickness of the substrate is usually 1 m to 10 mm, preferably 5 m to 3 mm.

Materials having conductivity are used for the source electrode 2, the drain electrode 3, and the gate electrode 6. For example, a metal such as platinum, gold, silver, aluminum, chromium, tungsten, tantalum, nickel, cobalt, copper, iron, lead, tin, titanium, indium, palladium, molybdenum, magnesium, calcium, barium, Of metals and alloys comprising them; Conductive oxides such as InO ₂ , ZnO ₂ , SnO ₂ and ITO; Conductive polymer compounds such as polyaniline, polypyrrole, polythiophene (PEDOT 占 P ss), polyacetylene, polyparaphenylene vinylene, and polydiacetylene; Organic charge transfer complexes such as BED-TTF; Semiconductors such as silicon, germanium, and gallium arsenide; Carbon materials such as carbon black, fullerene, carbon nanotubes and graphite can be used. The conductive polymer compound or the semiconductor may be doped. As the dopant, for example, an acid such as hydrochloric acid, sulfuric acid, or sulfonic acid; Lewis acids such as PF ₅ , AsF ₅ and FeCl ₃ ; Halogen atoms such as iodine, and metal atoms such as lithium, sodium, and potassium. In order to lower the contact resistance of the electrode, molybdenum oxide may be doped or metal may be treated with thiol. A conductive composite material in which metal particles such as carbon black, gold, platinum, silver and copper are dispersed in the above material is also used. Wiring is connected to each of the electrodes 2, 3 and 6, but the wiring is made of almost the same material as the electrodes. The film thickness of the source electrode 2, the drain electrode 3 and the gate electrode 6 varies depending on the material, but is usually 0.1 nm to 100 m, preferably 0.5 nm to 10 m, 1 nm to 5 탆.

The gate insulator layer 5 is a material having an insulating property and may be a material such as polyparaxylene, polyacrylate, polymethyl methacrylate, polystyrene, polyvinyl phenol, polyamide, polyimide, polycarbonate, Polymers such as polyvinyl alcohol, polyvinyl acetate, polyurethane, polysulfone, epoxy resin, and phenol resin, and copolymers thereof; Oxides such as silicon dioxide, aluminum oxide, titanium oxide, and tantalum oxide; SrTiO _3, BaTiO ₃ A strong dielectric oxide such as; Nitrides such as silicon nitride and aluminum nitride; sulfide; A fluoride or other dielectric material, or a polymer in which particles of these dielectric materials are dispersed. The film thickness of the gate insulator layer 5 varies depending on the material, but is usually 0.1 nm to 100 탆, preferably 0.5 nm to 50 탆, and more preferably 5 nm to 10 탆.

The organic semiconductor material contained in the semiconductor layer 4 is composed of at least the electron-accepting compound having the formula (1) and the cyano group. However, several kinds of the respective derivatives may be used in combination, By mass, preferably not less than 80% by mass, more preferably not less than 95% by mass. At this time, other organic semiconductor materials and various additives may be mixed as needed in order to improve characteristics of the field effect transistor and other characteristics. The semiconductor layer 4 may be composed of a plurality of layers. The film thickness of the semiconductor layer 4 is preferably as small as possible insofar as necessary functions are not lost. In a field effect transistor, if the thickness of the semiconductor element is greater than a predetermined thickness, the characteristics of the semiconductor element do not depend on the film thickness, but the leak current often increases as the film thickness increases. Conversely, if it is too thin, a charge can not form a channel (channel), so that a suitable film thickness is necessary. The film thickness of the semiconductor layer for exhibiting functions necessary for a semiconductor is usually 0.1 nm to 10 mu m, preferably 0.5 nm to 5 mu m, and more preferably 1 nm to 3 mu m.

The material of the protective layer 7 is not particularly limited. Examples of the material for the protective layer 7 include an epoxy resin, an acrylic resin such as polymethyl methacrylate, and a resin such as polyurethane, polyimide, polyvinyl alcohol, fluororesin, Film, a film made of a dielectric such as an inorganic oxide film or a nitride film, such as silicon oxide, aluminum oxide or silicon nitride is preferably used, and a resin (polymer) having a low oxygen permeability and a low water absorption rate is particularly preferable. In addition, protective materials developed for organic EL displays can be used. The film thickness of the protective layer can be any film thickness depending on the purpose, but is usually 100 nm to 1 mm. When the protective layer is formed, the influence of the outside air such as humidity can be reduced, and the ON / OFF ratio of the device can be increased.

The field effect transistor of the present invention can be used for cleaning the surface of a substrate by acid treatment with hydrochloric acid, sulfuric acid, acetic acid or the like, alkali treatment with sodium hydroxide, potassium hydroxide, calcium hydroxide or ammonia, ozone treatment, fluorination treatment, It is possible to exhibit excellent printability by performing plasma treatment, formation of a Langmuir-Blodgett film, formation of a thin film of another insulator or a semiconductor, electrical treatment such as mechanical treatment, corona discharge and the like. In addition, Other layers may be formed on the outer surface of the semiconductor element as required. In addition, by performing surface treatment in advance on a substrate or an insulator layer on which semiconductor layers are stacked, it is possible to control the molecular orientation and crystallinity of the interface portion between the substrate, the electrode and the semiconductor layer to be formed later, It is possible to further improve the uniformity of the device by improving the characteristics such as the carrier mobility by reducing or adjusting the hydrophilicity / hydrophobicity balance of the substrate surface by improving the film quality of the film to be formed thereon or the coating property to the substrate Do. Examples of the substrate treatment include a silane coupling treatment using phenylethyltrichlorosilane and the like, a rubbing treatment using a thiol treatment or a fiber, and the like.

As the method for forming each layer in the present invention, for example, a vacuum deposition method, a sputtering method, a coating method, a printing method, a sol-gel method and the like can be used suitably. However, The law is preferable.

Next, a method of manufacturing the field-effect transistor of the present invention will be described below based on the embodiment of Fig.

(Substrate and substrate processing)

The field-effect transistor of the present invention is fabricated by forming necessary electrodes and various layers on the substrate 1 (see Fig. 1). The above-described surface treatment or the like can also be performed on the substrate. It is preferable that the thickness of the substrate 1 is thin within a range that does not hinder necessary functions. But it is usually 1 m to 10 mm, preferably 5 m to 3 mm.

(Formation of source electrode and drain electrode)

The source electrode 2 and the drain electrode 3 are formed on the substrate 1 by using the electrode material or the like. The materials of the source electrode 2 and the drain electrode 3 may be the same or different. Examples of the method for forming the electrode include a vacuum evaporation method, a sputtering method, a coating method, a thermal transfer method, a printing method, a sol-gel method and the like. It is preferable to perform patterning as necessary so as to be in a desired shape at the time of film formation or after film formation. As the patterning method, various methods can be used. For example, a photolithography method in which patterning and etching of a photoresist are combined can be used. It is also possible to perform patterning by a printing method such as inkjet printing, screen printing, offset printing, and printing of a relief plate, a soft lithography method such as a micro contact printing method, or a combination of a plurality of these methods. Though the thicknesses of the source electrode 2 and the drain electrode 3 vary depending on the material, they are usually 0.1 nm to 100 탆, preferably 0.5 nm to 10 탆, and more preferably 1 nm to 5 탆 to be. The film thicknesses of the source electrode 2 and the drain electrode 3 may be the same or different.

(Formation of semiconductor layer)

The semiconductor layer is an organic thin film formed by the application printing process using the organic semiconductor material described above. The organic thin film may be referred to as an organic semiconductor thin film. The application printing process is a process in which an organic semiconductor material having solvent solubility, for example, an electron-accepting compound having the formula (1) of the present invention and a cyano group is dissolved or dispersed in an organic solvent in advance, Refers to a method of manufacturing a semiconductor layer that can easily form a semiconductor layer having excellent semiconductor characteristics by applying or printing a solution, and drying the solution. The manufacturing method by application or printing, that is, the application printing process, is advantageous industrially because it is not necessary to set the environment for device manufacturing to a vacuum or a high temperature state, and a large area field effect transistor can be manufactured at low cost, And is particularly preferable among various semiconductor layer production methods.

Specifically, the organic semiconductor material of the present invention is prepared by dissolving or dispersing the compound represented by the above formula (1) and the electron-accepting compound having a cyano group in a solvent. The compound represented by the formula (1) and the electron-accepting compound having a cyano group may be dissolved or dispersed at the same time, or they may be mixed and dissolved after dissolving or dispersing in a solvent. In the organic semiconductor material of the present invention, the concentration of the compound represented by the formula (1) and the electron-accepting compound having a cyano group (when plural kinds of these compounds are respectively used, the total concentration of the plural kinds of compounds) And the film thickness of the semiconductor layer to be produced, it is usually 0.001 to 50 mass%, preferably 0.01 to 20 mass%, based on the total amount of the solution. It is also possible to mix additives and other kinds of semiconductor materials in order to improve the film forming property of the semiconductor layer, improve the characteristics of the field effect transistor, and other characteristics.

In order to prepare an organic semiconductor material, it is necessary to dissolve or disperse the compound represented by the formula (1) and the electron-accepting compound having a cyano group in a solvent, but it may be subjected to a heating and dissolving treatment as occasion demands. The obtained organic semiconductor material may be filtered using a filter to remove impurities and the like. When this is coated on a substrate, the film-forming property of the semiconductor layer can be improved, and thus it can be suitably used.

The organic semiconductor material prepared as described above is applied to the substrate (the exposed portion of the source electrode and the drain electrode). As the coating method, coating methods such as casting, spin coating, dip coating, blade coating, wire bar coating, spray coating and the like; Printing methods such as inkjet printing, screen printing, offset printing, relief printing, and gravure printing; A soft lithography method such as a micro contact printing method, or a combination of a plurality of these methods. As a similar method to the application method, a Langmuir-Blodgett method in which a monomolecular film of a semiconductor layer produced by dropping the organic semiconductor material on a water surface is transferred to a substrate and laminated, a liquid crystal or a molten material is sandwiched between two substrates And a method of introducing it between the substrates by a capillary phenomenon can be employed. It is preferable that the film thickness of the semiconductor layer produced by these methods be thin within a range that does not impair the function. When the film thickness increases, the leakage current may increase. The film thickness of the semiconductor layer is the same as that of the semiconductor layer 4 described above.

The semiconductor layer thus fabricated can improve the semiconductor characteristics by post-processing. For example, after the semiconductor layer is formed, the substrate is heat-treated to alleviate warpage of the film formed during film formation and to control the arrangement and orientation of the film, thereby improving or stabilizing the semiconductor characteristics The pinholes and the like can be reduced. The heat treatment may be performed at any stage as far as the semiconductor layer is formed. The temperature of the heat treatment is not particularly limited, but is usually from room temperature to 150 占 폚, preferably from 40 to 120 占 폚, and more preferably from 45 to 100 占 폚. The heat treatment time is not particularly limited, but is usually 1 second to 24 hours, preferably 1 minute to 1 hour. The atmosphere during the heat treatment may be an atmosphere, but may be an inert atmosphere such as nitrogen or argon.

(Formation of gate insulator layer)

The gate insulator layer 5 is formed on the semiconductor layer 4 using the above-mentioned insulator material or the like (see Fig. 1). Examples of the method of forming the gate insulator layer 5 include coating methods such as spin coating, spray coating, dip coating, casting, bar coating, and blade coating; Screen printing, offset printing, ink jet printing; A vacuum evaporation method, a molecular beam epitaxial growth method, an ion cluster beam method, an ion plating method, a sputtering method, an atmospheric pressure plasma method, and a CVD method. In addition, a method of forming an oxide film on a metal surface such as a sol-gel method or an alumite on an aluminum surface can also be used.

The film thickness of the gate insulator layer 5 is preferably thinner within a range that does not impair its function, and is usually 0.1 nm to 100 탆, preferably 0.5 nm to 50 탆, more preferably 5 nm- 10 mu m.

(Formation of gate electrode)

The gate electrode 6 can be formed by the same method as that for forming the source electrode 2 and the drain electrode 3. The film thickness varies depending on the material, but is usually 1 nm to 100 탆, preferably 0.5 nm to 10 탆, and more preferably 1 nm to 5 탆.

(Protective layer)

When the protective layer 7 is formed using the above-mentioned protective layer material, the influence of the outside air can be minimized, and the electric characteristics of the field effect transistor can be stabilized (see Fig. 1). The film thickness of the protective layer 7 may be any film thickness depending on the purpose, but is usually 100 nm to 1 mm. Various methods can be employed to form the protective layer. When the protective layer is made of resin, for example, there can be used a method in which a solution containing a resin is applied and then dried to form a resin film, a method in which a resin monomer is applied or vapor- Followed by polymerization, and the like. The crosslinking treatment may be carried out after the film formation. When the protective layer is made of an inorganic material, for example, a forming method in a vacuum process such as a sputtering method or a vapor deposition method, or a forming method in a coating printing process such as a sol-gel method can be used. In the field-effect transistor of the present invention, the protective layer can be formed between the layers other than the surface of the semiconductor layer, if necessary. The protective layer provided may help stabilize the electrical characteristics of the field effect transistor.

In general, the operating characteristics of the field effect transistor are determined by the carrier mobility of the semiconductor layer, the conductivity, the capacitance of the insulating layer, the configuration of the element (the distance and width between the source and the drain electrodes, the thickness of the insulating layer, etc.). Although the organic material used for the semiconductor layer of the field effect transistor requires high carrier mobility, the compound represented by the formula (1) of the present invention, which can be produced at low cost, exhibits high carrier mobility as an organic semiconductor material . Further, the field-effect transistor of the present invention can be used in a flexible material such as a plastic plate or a plastic film which can be manufactured in a relatively low-temperature process and can not be used under high-temperature conditions. As a result, it is possible to manufacture a lightweight, highly flexible and brittle element, and can be used as a switching element of an active matrix of a display and the like. Examples of the display include a liquid crystal display, a polymer dispersed liquid crystal display, an electrophoretic display, an EL display, an electrochromic display, a particle rotating display, and the like. In addition, the field-effect transistor of the present invention can be manufactured by a coating-printing process such as coating because of good film-forming property, and can be manufactured at a very low cost in comparison with a conventional vacuum deposition process in the manufacture of a field effect transistor .

The field effect transistor of the present invention can be used as a digital element or an analog element such as a memory circuit element, a signal driver circuit element, and a signal processing circuit element, and by combining these elements, an IC card or an IC tag can be manufactured. Further, since the field effect transistor of the present invention can cause a change in its characteristics due to an external stimulus such as a chemical substance, its use as an FET sensor can also be expected.

Further, the present invention includes the following forms (2) to (7).

(2) The organic semiconductor material according to (1), wherein R ₁ and R ₂ in formula (1) are each independently a linear aliphatic hydrocarbon group of C 12 or less,

(3) The organic semiconductor material according to (1) or (2), wherein the electron-accepting compound having a cyano group is tetracyanoquinodimethane or a derivative thereof,

(4) The organic semiconductor material according to any one of (1) to (3), wherein the content of the electron-accepting compound having a cyano group to the compound represented by the formula (1) is 10 mass%

(5) A field effect transistor comprising an organic thin film obtained from the organic semiconductor material according to any one of (1) to (4)

(6) A method for manufacturing a field effect transistor in which an organic thin film is formed by applying or printing the organic semiconductor material according to any one of (1) to (4)

(7) A method for manufacturing a field effect transistor including a gate electrode, a gate insulator layer, a semiconductor layer, a source electrode and a drain electrode, comprising the steps of: (1) ), And drying the organic semiconductor material to form an organic thin film.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In the examples, parts denote parts by mass unless otherwise specified, and% denotes mass%, respectively. From the preparation of the semiconductor material to the evaluation of the semiconductor characteristics, all were performed in the air.

(Preparation of stock solution)

The compound (11) shown in Table 1 was dissolved in chloroform so as to have a concentration of 2% to prepare a stock solution of the compound (11). TCNQ and F4-TCNQ stock solutions were prepared by dissolving TCNQ (manufactured by Tokyo Kasei) and F4-TCNQ (manufactured by Tokyo Kasei) in acetonitrile to 0.2%, respectively.

[Example 1]

(Preparation of semiconductor material)

100 parts of the stock solution of the compound (11), 20 parts of the stock solution of TCNQ and 80 parts of chloroform were mixed to prepare a chloroform-acetonitrile (9: 1) solution containing 1% of the compound (11) and 0.02% A mixed solution 1 of an organic semiconductor material was prepared.

(Fabrication of transistor element)

The mixed solution 1 containing the previously prepared compound (11) and TCNQ was coated on an n-doped silicon wafer with a 300 nm SiO ₂ thermally oxidized film treated with UV ozone by a spin coating method, Lt; 0 > C for 10 minutes, and then dried at 120 DEG C for 1 minute to form an organic thin film. On this organic thin film, gold was deposited as a source electrode and a drain electrode (channel length: 50 mu m, channel width: 2 mm) by vacuum deposition using a metal mask to produce a bottom gate-top contact element.

(Characteristic evaluation)

Four semiconductor characteristics on one substrate were evaluated using a semiconductor parameter (4155C, manufactured by Agilent Co., Ltd.) as the obtained organic field effect transistor under the condition that the drain voltage was changed to -60 V and the gate voltage (Vg) was changed to +20 to -80 V did. As a result, the average value of the calculated mobility of the four electrodes was 0.31 cm 2 / Vs, and the standard deviation, which is an index showing the unevenness in the substrate, was 0.02 cm 2 / Vs. The threshold voltage was -29 V on average and the standard deviation was 1.3 V. The ON current was 2.3 × 10 ^-4 A and the standard deviation was 2.6 × 10 ^-5 A, indicating high semiconductor characteristics and uniformity in the substrate. The OFF current was on the order of 10 ^-11 A, and no increase in OFF current was observed even when an electron-accepting material was added. In addition, even when exposed for one week in the atmosphere, the mobility was 0.32 cm 2 / Vs, the threshold voltage was -31 V, and the ON current was 2.2 × 10 ^-4 A. The excellent semiconductor characteristics were maintained.

[Example 2]

(Preparation of semiconductor material)

100 parts of the stock solution of the compound (11), 10 parts of the stock solution of TCNQ, 80 parts of chloroform and 10 parts of acetonitrile were mixed to obtain chloroform-acetonitrile containing 1% of the compound (11) 9: 1) was prepared.

(Fabrication of transistor element)

A bottom gate-top contact device was fabricated in the same manner as in Example 1 except that the semiconductor material was changed from the mixed solution 1 to the mixed solution 2.

(Characteristic evaluation)

The semiconductor characteristics were evaluated under the same conditions as in Example 1. The average value of the mobility of the four electrodes was 0.58 cm 2 / Vs, and the standard deviation, which is an index showing the unevenness in the substrate, was 0.038 cm 2 / Vs. The threshold voltage was an average of -26 V and a standard deviation of 0.9 V. The ON current was 4.5 × 10 ^-4 A and the standard deviation was 3.7 × 10 ^-6 A, indicating high semiconductor characteristics and uniformity within the substrate. The OFF current was on the order of 10 ^-11 A, and the OFF current did not rise even when the electron-accepting material was added. In addition, even when exposed for one week in the atmosphere, the mobility was 0.59 cm 2 / Vs, the threshold voltage was -30 V, and the ON current was 4.1 × 10 ^-4 A. The excellent semiconductor characteristics were maintained.

[Example 3]

(Preparation of semiconductor material)

100 parts of the stock solution of the compound (11), 20 parts of the stock solution of F4-TCNQ and 80 parts of chloroform were mixed to obtain chloroform-acetonitrile (9) containing 1% of the compound (11) and 0.02% of F4- : 1) was prepared.

(Fabrication of transistor element)

A bottom gate-top contact device was fabricated in the same manner as in Example 1 except that the semiconductor material was changed from the mixed solution 1 to the mixed solution 3.

(Characteristic evaluation)

The semiconductor characteristics were evaluated under the same conditions as in Example 1. The average value of the mobility of the four electrodes was 0.42 cm 2 / Vs, and the standard deviation, which is an index indicating the unevenness in the substrate, was 0.007 cm 2 / Vs. The threshold voltage was -20 V on average and a standard deviation of 0.3 V. The ON current was 4.0 × 10 ^-4 A and the standard deviation was 9.1 × 10 ^-6 A, indicating high semiconductor characteristics and uniformity in the substrate. The OFF current was on the order of 10 ^-11 A, and the OFF current did not rise even when the electron-accepting material was added. In addition, even when exposed for one week in the atmosphere, the mobility was 0.42 cm 2 / Vs, the threshold voltage was -20 V, and the ON current was 3.9 × 10 ^-4 A. The excellent semiconductor characteristics were maintained.

[Comparative Example 1]

(Preparation of semiconductor material)

Compound 11 was dissolved in 1% chloroform-acetonitrile (9: 1) containing no electron-accepting compound by mixing 100 parts of the stock solution of the compound (11), 80 parts of chloroform and 20 parts of acetonitrile, Of the organic semiconductor material was prepared.

(Fabrication of transistor element)

A bottom gate-top contact device was fabricated in the same manner as in Example 1 except that the semiconductor material was changed from the mixed solution 1 to the mixed solution 4.

(Characteristic evaluation)

The semiconductor characteristics were evaluated under the same conditions as in Example 1. The average value of the mobility of the four electrodes was 0.22 cm 2 / Vs, and the standard deviation, which is an index indicating the unevenness in the substrate, was 0.062 cm 2 / Vs. The threshold voltage was -44 V and the standard deviation was 1.5 V. The ON current was 8.3 10 ^-5 A and the standard deviation was 2.9 10 ^-5 A. The mobility and the ON current were lower than those in Examples 1 and 2 , The threshold voltage is increased. In addition, the standard deviation showing the unevenness of each characteristic was also larger than that in the examples.

From the evaluation results of the above semiconductor characteristics, it has been found that the field-effect transistor made of the organic semiconductor material of the present invention stably operates in the atmosphere and has high semiconductor characteristics and durability. It has also been found that not only can semiconductor properties such as mobility, threshold voltage, and ON current be improved, but also uniformity in the surface can be improved as compared with the comparative example not including the electron-accepting material. Further, when manufacturing a semiconductor layer, it is not necessary to use a vacuum vapor deposition method which requires special equipment, but also a layer forming process for the purpose of complicated operations such as patterning in the surface treatment of a substrate and trap reduction It is possible to fabricate a semiconductor layer easily and inexpensively by a coating method or the like and improve the semiconductor characteristics. Therefore, the field effect transistor using the organic semiconductor material of the present invention can be said to be very useful with excellent transistor performance.

1: substrate
2: source electrode
3: drain electrode
4: semiconductor layer
5: gate insulator layer
6: gate electrode
7: Protective layer

Claims (7)

(TCNQ) or 2,3,5,6-tetrafluorotetracyano (1) to 1 to 10% by mass of a compound represented by the following formula (1) and a compound represented by the following formula -1,4-benzoquinodimethane (F4-TCNQ) is dissolved or dispersed in at least one organic solvent or dissolved and dispersed in an organic solvent:

(In the formula (1), R ₁ and R ₂ each independently represent an unsubstituted or halogen-substituted straight-chain C 1 -C 12 aliphatic hydrocarbon group). delete delete delete A field-effect transistor comprising an organic thin film obtained from the organic semiconductor material according to claim 1. A method for manufacturing a field effect transistor, wherein the organic thin film is formed by applying or printing the organic semiconductor material according to claim 1 and drying the organic thin film. A method of manufacturing a field effect transistor comprising a gate electrode, a gate insulator layer, a semiconductor layer, a source electrode and a drain electrode, comprising the steps of: forming an organic semiconductor material according to claim 1 between a source electrode and a drain electrode on a substrate or gate insulator layer Applying, printing, and drying the organic thin film to form an organic thin film.

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