KR20120116971A - 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 in which an electron-accepting compound having the following formula (1) and a cyano group is dissolved and / or dispersed in at least one organic solvent:

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

Description

Organic Semiconductor Materials and Field Effect Transistors and Methods for Manufacturing the Same {ORGANIC SEMICONDUCTOR METERIAL, FIELD-EFFECT TRANSISTOR, AND MANUFACTURING METHOD THEREOF}

The present invention relates to a field effect transistor comprising an organic thin film obtained by applying or printing an organic thin film semiconductor material and drying, a method for producing the same, and an organic semiconductor material used for them. In more detail, this invention relates to the field effect transistor obtained from the semiconductor material which consists of an organic heterocyclic compound and a specific additive, and its manufacturing method.

The field effect transistor generally has a structure in which a source electrode, a drain electrode, and a gate electrode or the like are formed on a semiconductor material on a substrate via these electrodes and an insulator layer. At present, an inorganic semiconductor material centered on silicon is used as the field effect transistor, and thin film transistors made on substrates such as glass using amorphous silicon are used in displays and the like. In addition to being used, it is widely used also for switching elements. In recent years, studies have been actively conducted using oxide semiconductors for semiconductor materials. However, when such inorganic semiconductor materials are used, it is necessary to process them at high temperature or in vacuum at the time of manufacturing the field effect transistors, and as the substrate to be used, a film having low heat resistance and Since plastic and the like cannot be used, and a large amount of equipment investment and manufacturing require a lot of energy, the cost is very high and its application range is very limited.

On the other hand, development of the field effect transistor using the organic semiconductor material which does not require high temperature processing at the time of manufacture of a field effect transistor is also actively performed. If applicable to an organic semiconductor material, the field effect transistor can be manufactured by a low temperature process, and the range of the board | substrate material which can be used expands. As a result, a more flexible, lightweight, and brittle field effect transistor can be manufactured. In addition, in the manufacturing process of the field effect transistor, it is also possible to apply a solution containing an organic semiconductor material or to manufacture a large area effect field transistor at low cost by a printing method using an ink jet or the like.

However, conventionally, since many organic semiconductor materials used for semiconductor materials are poorly soluble in organic solvents, inexpensive methods such as coating and printing cannot be used. Thus, substrates of semiconductors are relatively expensive by vacuum deposition. It was necessary to form a thin film on the top. At present, a device having a relatively high carrier mobility has been obtained by dissolving in an organic solvent and forming a film-forming and field effect transistor by a coating method, but using a coating or printing process, the mobility is high. In addition, field effect transistors using organic semiconductors with excellent durability have not been put to practical use, and developments for improving the transistor aptitude have been actively conducted.

BACKGROUND OF THE INVENTION A semiconductor device using an inorganic material such as silicon is generally treated with an oxidizing or reducing gas such as oxygen or hydrogen, an oxidizing or reducing liquid, or the like in an organic semiconductor layer for the purpose of increasing or decreasing the carrier density in a film. Or it is necessary to induce a change in properties by reduction. The reason is that by adding a small amount of elements, atomic groups, molecules, and polymers to the semiconductor layer, the carrier density in the semiconductor layer increases and decreases, thereby changing the electrical conductivity, carrier polarity (p-n-type conversion), Fermi level, etc., which are semiconductor characteristics. It is a technique, for example, by contacting gases, such as oxygen and hydrogen, immersing in the solution containing an acid, Lewis acid, etc., electrochemically by halogen atoms, such as iodine, or metal atoms, such as sodium and potassium, etc. The treatment method by the inorganic compound to process, Furthermore, the method of pretreatment with the organic compound of electron accepting or an electron donor, etc. are known. These treatments are carried out in processes other than the formation of the semiconductor layer before and after fabrication of the semiconductor layer, by co-deposition by a vacuum deposition method, mixing in the atmosphere at the time of fabrication of the semiconductor layer, or by accelerating ions in a vacuum to collide with the semiconductor layer. The technique of is generally used.

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

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

Patent Literature 4 discloses a technique for amplifying a current value by bringing an iodine or a metal into contact with a pentacene thin film.

Patent Literature 5 discloses a technique for improving electrical conductivity by using a thin film obtained by coating and drying a solution containing a polyacene compound and an excess of iodine or butyllithium.

Patent Literature 6 discloses a technique of changing a threshold voltage by laminating a polymer semiconductor after applying an electron accepting or electron donating compound 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 created by a surface selective precipitation method using an alkyl derivative of benzothieno [3,2-b] [1] benzothiophene.

International Publication No. 2008/047896 Japanese Laid-Open Patent Publication No. 2009-267372 Japanese Laid-Open Patent Publication No. 2009-283786 Japanese Patent Laid-Open 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).

The present invention not only improves semiconductor characteristics such as reducing the threshold voltage while maintaining high carrier mobility, but also provides an excellent field effect transistor having a printability capable of forming a thin film with high uniformity in a small process. For the purpose of

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, the present invention,

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

(In Formula (1), R ₁ and R ₂ each independently represent an unsubstituted or halogen-substituted C1-C36 aliphatic hydrocarbon group.)

.

High carrier transfer 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. It is possible to provide a practical field effect transistor having excellent printing aptitude capable of forming a thin film with high uniformity in a small process as well as improving semiconductor characteristics such as reducing a threshold voltage while maintaining the drawing.

1 is a schematic diagram 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 a specific organic heterocyclic compound and an electron-accepting compound having a cyano group are dissolved and / or dispersed in at least one organic solvent, a field effect transistor using the same, and a manufacturing method thereof.

First, the compound represented by said formula (1) is demonstrated. In said formula (1), R <_1> and R <_2> respectively independently represents an unsubstituted or halogen substituted C1-C36 aliphatic hydrocarbon group. The aliphatic hydrocarbon group is a saturated or unsaturated linear, branched or cyclic aliphatic hydrocarbon group, preferably a linear or branched aliphatic hydrocarbon group, and more preferably a linear aliphatic hydrocarbon group. Carbon number is C1-C36 normally, Preferably it is C2-C24, More preferably, it is C4-C20, More preferably, it is C6-C12.

Specific examples of the linear or branched saturated aliphatic hydrocarbon group include methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, t-butyl, n-pentyl, iso-pentyl, t-pentyl, sec-pentyl , n-hexyl, iso-hexyl, n-heptyl, sec-heptyl, n-octyl, n-nonyl, sec-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n- Tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, docosyl, n-pentacosyl, n-octacosyl, n-tricontyl , 5- (n-pentyl) decyl, hencosyl, tricosyl, tetracosyl, hexacosyl, heptacosyl, nonacosyl, n-triacyl, squary, dotriacontyl, hexatriac And the like. Moreover, cyclohexyl, cyclopentyl, adamantyl, norbornyl, etc. are mentioned as a specific example of cyclic saturated aliphatic hydrocarbon group. Specific examples of the linear or branched unsaturated aliphatic hydrocarbon group include vinyl, aryl, eicosadienyl, 11,14-eicosadienyl and geranyl (trans-3,7-dimethyl-2,6-octadiene-1- 1), farnesyl (trans, trans-3,7,11-trimethyl-2,6,10-dodecatrien-1-yl), 4-pentenyl, 1-propynyl, 1-hexynyl, 1- Octynyl, 1-decynyl, 1-undecynyl, 1-dodecynyl, 1-tetradecynyl, 1-hexadecynyl, 1-nonadecinyl and the like.

Among the linear, branched and cyclic aliphatic hydrocarbon groups, linear or branched aliphatic hydrocarbon groups are preferable, and linear aliphatic hydrocarbon groups are particularly preferable.

The saturated or unsaturated aliphatic hydrocarbon group includes a saturated alkyl group, an alkenyl group containing a carbon-carbon double bond, and an alkynyl group containing a carbon-carbon triple bond, and more preferably an alkyl group or an alkynyl group, and more preferably. Preferably 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 atoms are substituted by any number at any position of the aliphatic hydrocarbon group described above. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, Preferably a fluorine atom, a chlorine atom, a bromine atom, More preferably, a fluorine atom and a bromine atom are mentioned. Specific examples of the halogen-substituted aliphatic hydrocarbon group include chloromethyl, bromomethyl, trifluoromethyl, pentafluoroethyl, n-perfluoropropyl, n-perfluorobutyl, n-perfluoropentyl, and n-purple Urooctyl, n-perfluorodecyl, n- (dodecafluoro) -6-iodohexyl, 2,2,3,3,3-pentafluoropropyl, 2,2,3,3-tetra Fluoropropyl, etc. are mentioned.

The compound represented by said formula (1) can be synthesize | combined by the well-known method of patent document 1 and nonpatent literature 1, for example.

The purification method of the compound represented by said Formula (1) is not specifically limited, Well-known methods, such as recrystallization, column chromatography, and a vacuum sublimation purification, can be employ | adopted. Moreover, you may use combining these methods as needed.

Specific examples of the compound represented by Formula (1) are shown in Table 1 below.

The electron-accepting compound having a cyano group is an additive that is doped with an organic semiconductor material, and is not particularly limited. Examples thereof include tetracyanoquinomimethane (hereinafter abbreviated as TCNQ) or a derivative thereof. Specifically, TCNQ, 2, 3,5,6-tetrafluorotetracyano-1,4-benzoquinodimethane (hereinafter abbreviated as F4-TCNQ), trifluoromethyltetracyanoquinodimethane (CF3TCNQ), 2,5-difluoro Lotetracyanoquinomethane (F2TCNQ), Fluorotetracyanoquinomethane (FTCNQ), Tetracyanoethylene (TCNE), 11,11,12,12-tetracyanonaphtho-2,6-quinodi Methane (TNAP) and quinodimethanes having cyano groups described in JP-A-2008-530773 are suitably used. Especially, TCNQ or F4-TCNQ is especially preferable.

The organic semiconductor material of the present invention is formed by dissolving or dispersing at least the compound represented by the formula (1) and the electron-accepting compound having a cyano group in an organic solvent, but the electron having the compound represented by the formula (1) and the cyano group Even if it contains one type of water-soluble compound, you may mix and use the several types of derivatives of one or both of the compound represented by said Formula (1), and the electron-accepting compound which has a cyano group. In the organic-semiconductor material containing the compound represented by said Formula (1), and the electron-accepting compound which has a cyano group, the content rate of the electron-accepting compound which has a cyano group with respect to the compound represented by said Formula (1) is 0.1-40 mass normally. Although it is the range of%, it is preferable that it is 0.1-20 mass%, and it is more preferable that it is 0.1-10 mass%. When content rate exceeds 40 mass%, a characteristic value will fall by increase of OFF current. When using TCNQ or F4-TCNQ, it is especially preferable that content rate is 10 mass% or less.

Other organic semiconductor materials and various additives may be mixed with the organic semiconductor material of the present invention as necessary in order to improve the characteristics of the field effect transistor or to impart other characteristics as long as the effects of the present invention are not impaired. As these additives, a viscosity regulator, a surface tension regulator, a leveling agent, a penetrant, a rheology regulator, an aligning agent, a dispersing agent, etc. are mentioned.

The content rate of these additives is 0-30 mass% with respect to the total amount of the organic-semiconductor material of this invention, 0-20 mass% is preferable, and 0-10 mass% is more preferable.

The organic-semiconductor material of this invention melt | dissolves or disperse | distributes the compound and electron-accepting compound represented by Formula (1) in the solvent, and improved the application | coating printing process adaptability of an organic semiconductor material. As a solvent which can be used, if a compound can be formed into a film on a board | substrate, it will not specifically limit, but an organic solvent is preferable and even a single organic solvent can mix and use a some organic solvent. Specifically, Halogen hydrocarbon solvent, such as chloroform, methylene chloride, 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 tetraine; Nitrile solvents, such as acetonitrile, propiononitrile, butyronitrile, and benzonitrile, etc. can be used, These can also be used individually or in mixture. Although the density | concentration of the compound and electron-accepting compound represented by Formula (1) changes with kinds of solvent and the film thickness of the semiconductor layer to produce, it is 0.001-50 mass% in total amount with respect to the solvent in a liquid mixture, 0.01-20 mass It is preferable that it is%. In addition, although the semiconductor material of this invention should just melt | dissolve or disperse | distribute in said organic solvent, In order to form a more uniform thin film, it is more preferable to melt | dissolve as a uniform 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.

Although some aspects of the field effect transistor of this invention are shown in FIG. 1, the arrangement | positioning of each layer and electrode can be suitably selected by the use of an element. In addition, the same number is attached | subjected to the same name in FIG.

Next, although each component of the field effect transistor of this invention shown in FIG. 1 is demonstrated, it is not limited to this.

The board | substrate 1 needs to be able to hold | maintain without peeling each layer formed on it. For example, insulating materials, such as a resin plate, a resin film, paper, glass, quartz, a ceramic; A formation in which an insulating layer is coated on a conductive substrate such as a metal or an alloy; The material etc. which consist of various combinations of resin, an inorganic material, etc. can be used. Especially, as a resin film generally used, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyamide, polyimide, polycarbonate, cellulose triacetate, polyetherimide, etc. are mentioned, for example. When a resin film or paper is used, the semiconductor element can be made effective, and it becomes flexible and lightweight, and the practicality is improved. The thickness of a board | substrate is 1 micrometer-10 mm normally, Preferably they are 5 micrometers-3 mm.

A conductive material is used for the source electrode 2, the drain electrode 3, and the gate electrode 6. For example, platinum, gold, silver, aluminum, chromium, tungsten, tantalum, nickel, cobalt, copper, iron, lead, tin, titanium, indium, palladium, molybdenum, magnesium, calcium, barium, lithium, potassium, sodium, etc. Metals and alloys containing them; Conductive oxides such as InO ₂ , ZnO ₂ , SnO ₂ , and ITO; Conductive polymer compounds such as polyaniline, polypyrrole, polythiophene (PEDOT, PSS, etc.), polyacetylene, polyparaphenylenevinylene, polydiacetylene and the like; Organic charge transfer complexes such as BED-TTF; Semiconductors such as silicon, germanium and gallium arsenide; Carbon materials, such as carbon black, fullerene, a carbon nanotube, and graphite, can be used. Moreover, you may doping to a conductive high molecular compound and a semiconductor, As a dopant, For example, Acid, such as hydrochloric acid, a sulfuric acid, sulfonic acid; Lewis acids such as PF ₅ , AsF ₅ , FeCl ₃ and the like; Halogen atoms, such as iodine, Metal atoms, such as lithium, sodium, and potassium, etc. are used. In order to reduce the contact resistance of the electrode, a method of doping molybdenum oxide or a metal such as thiol may be applied. Moreover, the electroconductive composite material which disperse | distributed metal particles, such as carbon black, gold, platinum, silver, copper, is also used for the said material. Wiring is connected to each of the electrodes 2, 3, and 6, but the wiring is also made of almost the same material as the electrode. Although the film thickness of the source electrode 2, the drain electrode 3, and the gate electrode 6 differs with a material, it is 0.1 nm-100 micrometers normally, Preferably it is 0.5 nm-10 micrometers, More preferably, 1 nm-5 micrometers.

The gate insulator layer 5 is an insulating material, and for example, polyparaxylene, polyacrylate, polymethylmethacrylate, polystyrene, polyvinylphenol, polyamide, polyimide, polycarbonate, polyester, Polymers such as polyvinyl alcohol, polyvinyl acetate, polyurethane, polysulfone, epoxy resin, phenol resin, and copolymers thereof; Oxides such as silicon dioxide, aluminum oxide, titanium oxide and tantalum oxide; SrTiO ₃ , BaTiO ₃ Ferroelectric oxides such as these; Nitrides such as silicon nitride and aluminum nitride; sulfide; Dielectrics, such as a fluoride, or the polymer which disperse | distributed the particle | grains of these dielectrics, etc. can be used. Although the film thickness of the gate insulator layer 5 changes with materials, it is 0.1 nm-100 micrometers normally, Preferably it is 0.5 nm-50 micrometers, More preferably, it is 5 nm-10 micrometers.

Although the organic-semiconductor material contained in the semiconductor layer 4 consists of an electron-accepting compound which has at least said Formula (1) and a cyano group, you may mix and use several types of each derivative, and the said semiconductor material to a total amount It is necessary to contain 50 mass% or more, Preferably it is 80 mass% or more, More preferably, 95 mass% or more. Under the present circumstances, in order to improve the characteristic of a field effect transistor, or to provide another characteristic, you may mix other organic semiconductor materials and various additives as needed. In addition, the semiconductor layer 4 may consist of several layer. The film thickness of the semiconductor layer 4 is so preferable that it is thin in the range which does not lose a required function. In the field effect transistor, when there is a predetermined thickness or more, the characteristics of the semiconductor element do not depend on the film thickness. However, when the film thickness becomes thick, the leakage current often increases. Conversely, if too thin, electric charges cannot form passages (channels), so an appropriate film thickness is necessary. The film thickness of the semiconductor layer for showing the function which a semiconductor requires is normally 0.1 nm-10 micrometers, Preferably it is 0.5 nm-5 micrometers, More preferably, it is 1 nm-3 micrometers.

Although it does not specifically limit as a material of the protective layer 7, For example, it consists of acrylic resins, such as an epoxy resin and polymethylmethacrylate, various resins, such as a polyurethane, a polyimide, polyvinyl alcohol, a fluororesin, a polyolefin, etc. A film or a film made of a dielectric such as an inorganic oxide film or a nitride film, such as silicon oxide, aluminum oxide, silicon nitride, or the like, is preferably used. Particularly, a resin (polymer) having a low oxygen permeability and low water absorption is preferable. Moreover, the protective material developed for organic electroluminescent display can also be used. Although the film thickness of a protective layer can employ | adopt arbitrary film thickness according to the objective, it is 100 nm-1 mm normally. When the protective layer is formed, the influence of external air such as humidity can be reduced, and the ON / OFF ratio of the device can be increased, and there are also advantages of stabilizing electrical characteristics.

The field effect transistor of the present invention may be treated with an acid treatment with hydrochloric acid, sulfuric acid, acetic acid or the like, alkali treatment with sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, ozone treatment, fluorination treatment, oxygen or argon, etc. Excellent printing titration can be obtained by performing plasma treatment, Langmuir-Blodgett film formation treatment, other insulator or semiconductor thin film formation treatment, mechanical treatment, electrical treatment such as corona discharge, and the like. Other layers may be formed between the layers or on the outer surface of the semiconductor element as necessary. In addition, the surface treatment is performed on a substrate or an insulator layer on which a semiconductor layer is laminated in advance, thereby controlling molecular orientation and crystallinity of an interface portion with a substrate, an electrode, or the like, and then depositing a film. By improving the characteristics such as carrier mobility by reducing or adjusting the hydrophilicity / hydrophobicity of the surface of the substrate, it is possible to further improve the uniformity of the device by improving the film quality of the film formed thereon or the coating property on the substrate. Do. As such a substrate process, the silane coupling process by phenyl ethyl trichlorosilane etc., the rubbing process using a thiol process, a fiber, etc. are mentioned, for example.

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 appropriately used. The law is preferred.

Next, the manufacturing method of the field effect transistor of this invention is demonstrated below based on the example of FIG.

(Substrate and substrate processing)

The field effect transistor of the present invention is produced by forming necessary electrodes and various layers on the substrate 1 (see FIG. 1). It is also possible to perform the above-mentioned surface treatment on this board | substrate. It is preferable that the thickness of the board | substrate 1 is thin in the range which does not prevent a required function. Although it changes also with a material, it is 1 micrometer-10 mm normally, Preferably it is 5 micrometers-3 mm.

(Formation of source electrode and drain electrode)

The source electrode 2 and the drain electrode 3 are formed on the board | substrate 1 using said electrode material etc. The materials of the source electrode 2 and the drain electrode 3 may be the same or different. As a method of forming an electrode, a vacuum vapor deposition method, the sputtering method, the coating method, the thermal transfer method, the printing method, the sol-gel method etc. are mentioned, for example. It is preferable to perform patterning as needed so that it may become a desired shape at the time of film-forming or after film-forming. 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. Moreover, it can also be patterned using the printing method of inkjet printing, screen printing, offset printing, convex printing, etc., the soft lithography method, such as a microcontact printing method, and the method which combined multiple these methods. Although the film thickness of the source electrode 2 and the drain electrode 3 differs also with a material, it is 0.1 nm-100 micrometers normally, Preferably it is 0.5 nm-10 micrometers, More preferably, 1 nm-5 micrometers to be. The film thicknesses of the source electrode 2 and the drain electrode 3 may be the same, or may differ.

(Formation of Semiconductor Layer)

The semiconductor layer is an organic thin film formed by a coating printing process using the organic semiconductor material described above. The organic thin film may be referred to as an organic semiconductor thin film. The coating printing process is an organic semiconductor material obtained by dissolving or dispersing an organic semiconductor material having solvent solubility, for example, the compound represented by the formula (1) of the present invention and an electron-accepting compound having a cyano group in an organic solvent in advance. The manufacturing method of the semiconductor layer which can apply | coat or print a melt, dry, and can easily form the semiconductor layer which has the outstanding semiconductor characteristic. The manufacturing method by coating or printing, i.e., the coating printing process, is industrially advantageous because it is not necessary to make the environment at the time of device manufacture in a vacuum or a high temperature state, and a large-area field effect transistor can be manufactured at low cost. It is especially preferable among the manufacturing methods of various semiconductor layers.

Specifically, the organic semiconductor material of the present invention is prepared by dissolving or dispersing the compound represented by the 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 separately mixed or dissolved in a solvent before being mixed. The concentration of the compound represented by Formula (1) in the organic semiconductor material of the present invention and the electron-accepting compound having a cyano group (when plural kinds of these compounds are used, respectively, the total concentration of plural kinds of compounds) is a kind of solvent. In addition, although it changes with the film thickness of the semiconductor layer to manufacture, it is preferable that it is 0.001-50 mass% normally with respect to a solution total amount, and it is preferable that it is 0.01-20 mass%. In order to improve the film-forming properties of the semiconductor layer, to improve the field effect transistor characteristics, and to impart other properties, it is also possible to mix additives or other semiconductor materials.

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. In addition, the obtained organic semiconductor material may be filtered using a filter to remove impurities and the like. When this is applied onto a substrate, improvement in the film-forming properties of the semiconductor layer can be seen and can be suitably used.

The organic semiconductor material prepared as mentioned above is apply | coated to the board | substrate (exposed part of a source electrode and a drain electrode). Examples of the coating method include coating methods such as casting, spin coating, dip coating, blade coating, wire bar coating, and spray coating; Printing methods such as inkjet printing, screen printing, offset printing, convex printing and gravure printing; Soft lithography such as microcontact printing and the like, and further, a combination of a plurality of these techniques can be employed. In addition, as a method similar to the coating method, the Langmuir-Blodgett method, in which the monolayer film of the semiconductor layer produced by dropping the above organic semiconductor material on the water surface, is laminated on a substrate, and a liquid crystal or a melted material is sandwiched between two substrates. The method which introduce | transduces between board | substrates by a capillary phenomenon etc. can also be employ | adopted. As for the film thickness of the semiconductor layer produced by these methods, the thinner side is preferable in the range which does not impair a function. As the film thickness increases, the leakage current may increase. The film thickness of a semiconductor layer is the same as that of the said semiconductor layer 4.

The semiconductor layer thus produced can improve semiconductor characteristics by post-treatment. For example, by forming a semiconductor layer and then heat-treating the substrate, distortion in the film generated during film formation is alleviated, and the improvement and stabilization of semiconductor characteristics can be achieved for reasons such as control of arrangement and orientation in the film. The pinhole etc. can also be reduced. The heat treatment may be performed at any stage as long as the semiconductor layer is formed. Although the temperature of heat processing does not have a restriction | limiting in particular, Usually, at room temperature-150 degreeC, Preferably it is 40-120 degreeC, More preferably, it is 45-100 degreeC. The time for heat treatment is not particularly limited, but is usually 1 second to 24 hours, preferably 1 minute to 1 hour. Although the atmosphere at the time of heat processing may be in air | atmosphere, it is good also in inert atmosphere, such as nitrogen and argon.

(Formation of Gate Insulator Layer)

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

As for the film thickness of the gate insulator layer 5, the thinner is preferable in the range which does not impair the function, It is 0.1 nm-100 micrometers normally, Preferably it is 0.5 nm-50 micrometers, More preferably, it is 5 nm? 10 micrometers.

(Formation of gate electrode)

The gate electrode 6 can be formed by the same method as the preparation method of the source electrode 2 and the drain electrode 3. Although film thickness changes also with a material, it is 1 nm-100 micrometers normally, Preferably it is 0.5 nm-10 micrometers, More preferably, it is 1 nm-5 micrometers.

(Protective layer)

When the protective layer 7 is formed using the above protective layer material, there is an advantage that the influence of external air can be minimized and the electrical characteristics of the field effect transistor can be stabilized (see FIG. 1). Although the film thickness of the protective layer 7 can employ | adopt an arbitrary film thickness according to the objective, it is 100 nm-1 mm normally. Various methods may be employed to form the protective layer. However, in the case where the protective layer is made of resin, for example, a solution containing a resin may be dried after coating to form a resin film, or a resin monomer may be coated or deposited. The method of superposing | polymerizing after that etc. can be mentioned, You may perform a crosslinking process after film-forming. When a protective layer consists of an inorganic substance, the formation method in vacuum printing processes, such as a sputtering method and a vapor deposition method, and the formation method in coating printing processes, such as a sol-gel method, can be used, for example. The field effect transistor of this invention can form a protective layer between each layer besides the surface of a semiconductor layer as needed. The protective layer provided may help to stabilize the electrical characteristics of the field effect transistor.

In general, the operation 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 element configuration (distance and width between the source and drain electrodes, the film thickness of the insulating layer, and the like). Although high carrier mobility is required for the organic material used for the semiconductor layer of a field effect transistor, the compound represented by said Formula (1) of this invention which can be manufactured at low cost expresses high carrier mobility as an organic semiconductor material. . In addition, the field effect transistor of the present invention can be manufactured in a relatively low temperature process, and flexible materials such as plastic plates and plastic films that cannot be used under high temperature conditions can also be used as substrates. As a result, it is possible to manufacture a lightweight, flexible, and fragile element, which can be used as a switching element of an active matrix of a display. 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 rotation display, and the like. In addition, the field effect transistor of the present invention can be manufactured in a coating printing process such as coating because of good film forming properties, and the field effect transistor of a large area display is manufactured at a very low cost compared to a conventional vacuum deposition process. Applicable to

The field effect transistor of the present invention can also 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, an IC card or an IC tag can be produced. In addition, since the field effect transistor of the present invention can change its characteristics by an external stimulus such as a chemical substance, its use as a FET sensor can also be expected.

In addition, the following aspects (2) to (7) are included in the present invention.

(2) The organic semiconductor material according to (1), wherein R ₁ and R ₂ in Formula (1) are each independently a straight-chain aliphatic hydrocarbon group of C12 or less,

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

(4) The organic-semiconductor material in any one of (1)-(3) whose content of the electron-accepting compound which has a cyano group with respect to the compound represented by Formula (1) is 10 mass% or less,

(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 producing a field effect transistor, in which the organic semiconductor material according to any one of (1) to (4) is applied or printed and dried to form an organic thin film,

(7) 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 (1) to (4) between a source electrode and a drain electrode on a substrate or gate insulator layer. The manufacturing method of the field effect transistor which forms an organic thin film by apply | coating or printing the organic semiconductor material in any one of), and drying.

Example

Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these. In the examples, parts are parts by mass unless otherwise specified, and% each represents mass%. In addition, all were performed in air | atmosphere from preparation of a semiconductor material to evaluation of a semiconductor characteristic.

(Preparation of Stock Solution)

The compound (11) of Table 1 was dissolved in chloroform so that it might become 2%, and the stock solution of the compound (11) was prepared. On the other hand, TCNQ (made by Tokyo Kasei) and F4-TCNQ (made by Tokyo Kasei) were dissolved in acetonitrile so as to be 0.2%, respectively, and the stock solution of TCNQ and F4-TCNQ was prepared, respectively.

[Example 1]

(Preparation of Semiconductor Materials)

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

(Creation of transistor element)

After coating a mixed solution 1 containing a compound (11) and TCNQ prepared in advance on an n-doped silicon wafer with 300 nm SiO ₂ thermal oxide film treated with UV and ozone by spin coating, the substrate was heated on a hot plate. After heating at 10C for 10 minutes, it was dried at 120C for 1 minute to form an organic thin film. Gold was deposited on the organic thin film as a source electrode and a drain electrode (channel length of 50 µm, channel width of 2 mm) by a vacuum deposition method using a metal mask to fabricate a bottom gate-top contact element.

(Characteristic evaluation)

Four semiconductor characteristics on one substrate were evaluated using the semiconductor parameter (4155C manufactured by Agilent) for the obtained organic field effect transistor under conditions in which the drain voltage was changed to -60V and the gate voltage (Vg) was +20 to -80V. 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 indicating nonuniformity in the substrate, was 0.02 cm 2 / Vs. In addition, the threshold voltage was an average of -29V and a standard deviation of 1.3V, and the ON current showed 2.3x10 ^-4 A, standard deviation of 2.6x10 ^-5 A, high semiconductor characteristics, and uniformity in the substrate. In addition, OFF current was a ^10-11 A order, and even if an electron accepting material was added, the increase of OFF current was not seen. In addition, even when exposed to air for one week, the mobility was 0.32 cm 2 / Vs, the threshold voltage was -31 V, and the ON current was 2.2 × 10 ^-4 A, maintaining excellent semiconductor characteristics.

EXAMPLE 2

(Preparation of Semiconductor Materials)

100 parts of the stock solution of compound (11), 10 parts of the stock solution of TCNQ, 80 parts of chloroform, and 10 parts of acetonitrile were respectively mixed to obtain chloroform-acetonitrile containing 1% of compound (11) and 0.01% of TCNQ. The mixed solution 2 of the organic semiconductor material of 9: 1) was prepared.

(Creation of transistor element)

A bottom gate-top contact element was produced 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)

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 indicating nonuniformity in the substrate, was 0.038 cm 2 / Vs. In addition, the threshold voltage was an average of -26V and a standard deviation of 0.9V, and the ON current was 4.5x10 ^-4 A and a standard deviation of 3.7x10 ^-6 A, indicating high semiconductor characteristics and uniformity in the substrate. In addition, OFF current was a ^10-11 A order, and even when an electron accepting material was added, there was no increase of OFF current. In addition, even when exposed to air for one week, the mobility was 0.59 cm 2 / Vs, the threshold voltage -30V, and the ON current of 4.1 x 10 ^-4 A, maintaining excellent semiconductor characteristics.

[Example 3]

(Preparation of Semiconductor Materials)

100 parts of the stock solution of Compound (11), 20 parts of the stock solution of F4-TCNQ, and 80 parts of chloroform were respectively mixed to give chloroform-acetonitrile (9) containing 1% of Compound (11) and 0.02% of F4-TCNQ. The mixed solution 2 of the organic-semiconductor material of (1) was prepared.

(Creation of transistor element)

A bottom gate-top contact element was produced 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)

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 nonuniformity in the substrate, was 0.007 cm 2 / Vs. In addition, the threshold voltage was an average of -20V and a standard deviation of 0.3V, and the ON current was 4.0x10 ^-4 A and a standard deviation of 9.1x10 ^-6 A, indicating high semiconductor characteristics and uniformity in the substrate. In addition, OFF current was a ^10-11 A order, and even when an electron accepting material was added, there was no increase of OFF current. Moreover, even when exposed to air for one week, the mobility was 0.42 cm 2 / Vs, the threshold voltage was -20 V, and the ON current was 3.9 x 10 ^-4 A, maintaining excellent semiconductor characteristics.

[Comparative Example 1]

(Preparation of Semiconductor Materials)

100% of the stock solution of the compound (11), 80 parts of chloroform and 20 parts of acetonitrile were mixed, and the compound (11) containing 1% chloroform-acetonitrile (9: 1) containing no electron-accepting compound was added. Mixed solution 4 of the organic semiconductor material was prepared.

(Creation of transistor element)

A bottom gate-top contact element was produced 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)

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 nonuniformity in the substrate, was 0.062 cm 2 / Vs. In addition, the threshold voltage is an average of -44V, the standard deviation 1.5V, the ON current is 8.3 × 10 ^-5 A, the standard deviation is 2.9 × 10 ^-5 A, the mobility and the ON current is lower than in Examples 1 and 2, , The threshold voltage has increased. Moreover, the standard deviation which shows the nonuniformity of each characteristic was also large compared with an Example.

From the above evaluation results of the semiconductor characteristics, it was found that the field effect transistor made of the organic semiconductor material of the present invention operates stably in the air and has high semiconductor characteristics and durability. In addition, as compared with the comparative example which does not contain an electron accepting material, it has been found that not only can any semiconductor characteristic among mobility, threshold voltage, and ON current be improved, but also in-plane uniformity can be improved. In addition, when fabricating a semiconductor layer, it is not necessary to use a vacuum deposition method that requires special equipment or the like, and a layer forming process for the purpose of complicated operations such as patterning in substrate surface treatment and trap reduction. It was confirmed that the semiconductor layer can be produced easily and inexpensively by the coating method or the like, without requiring any of them, and the semiconductor characteristics can be improved. Therefore, the field effect transistor using the organic semiconductor material of the present invention can be said to be very useful having 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)

The organic-semiconductor material which dissolves and / or disperse | distributes the compound represented by following formula (1) and the electron accepting compound which has a cyano group in at least 1 type of organic solvent:

(In formula (1), R <_1> and R <_2> respectively independently represents an unsubstituted or halogen substituted C1-C36 aliphatic hydrocarbon group.). The method of claim 1,
The organic semiconductor material wherein R ₁ and R ₂ in Formula (1) are each independently a straight-chain aliphatic hydrocarbon group of C12 or less. The method according to claim 1 or 2,
The organic-semiconductor material whose electron-accepting compound which has a cyano group is tetracyano quinodimethane or its derivative (s). 4. The method according to any one of claims 1 to 3,
The organic-semiconductor material whose content of the electron-accepting compound which has a cyano group with respect to the compound represented by Formula (1) is 10 mass% or less. A field effect transistor comprising an organic thin film obtained from the organic semiconductor material according to any one of claims 1 to 4. The manufacturing method of the field effect transistor which forms an organic thin film by apply | coating or printing the organic semiconductor material of any one of Claims 1-4, and drying. A method for manufacturing a field effect transistor comprising a gate electrode, a gate insulator layer, a semiconductor layer, a source electrode, and a drain electrode, comprising: any one of claims 1 to 4 between a source electrode and a drain electrode on a substrate or a gate insulator layer; The manufacturing method of the field effect transistor which forms an organic thin film by apply | coating or printing the organic semiconductor material of Claim 1, and drying.

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