JP2008060116A - Organic thin-film transistor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin-film transistor, having high carrier mobility and obtained by improving crystallinity of an organic semiconductor film (layer), and to provide its manufacturing method. <P>SOLUTION: The organic thin-film transistor has a structure in which source and drain electrodes are formed on a substrate, having a gate electrode and an insulating film, and an organic semiconductor layer is formed thereon. In the organic thin-film transistor, a unimolecular film is formed on the surface of each of the substrate and the source and the drain electrodes; the end of the unimolecular film bonded to the surface of the substrate and the ends of the unimolecular films, bonded to the surface of the source and drain electrodes, have the same chemical structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic thin film transistor in which carrier mobility is increased by high crystallization of an organic semiconductor layer and a manufacturing method thereof.

  With the widespread use of information terminals, there is an increasing need for flat panel displays as computer displays. In addition, with the progress of computerization, information that has been provided on paper media in the past has become more and more electronically provided. As a mobile display medium that is thin, light, and easy to carry, electronic paper or There is a growing need for digital paper.

  In recent years, various organic thin film transistors (hereinafter also referred to as “organic TFTs”) using an organic semiconductor as a semiconductor channel have been studied. Organic semiconductors are easier to process than inorganic semiconductors and have high affinity with plastic supports, making them attractive as thin-layer devices.

  Conventionally, in the manufacture of an organic thin film transistor, an organic semiconductor layer (hereinafter also referred to as “organic semiconductor thin film”) is directly formed on a gate insulating layer by a wet process such as a vacuum deposition method, a spin coating method, or a casting method.

  As a method for forming the gate insulating layer, in the case of an inorganic material, an RF (DC) sputtering method, a CVD method, or the like is often used. In addition, in order to uniformly form a high-quality insulating film on the gate electrode, a technique called anodic oxidation may be used by using as the gate electrode a metal from which an oxide having a high dielectric constant such as Al or Ta is obtained. For example, in the manufacture of an organic thin film transistor (hereinafter also referred to as “organic TFT”) using silicon oxide as a gate insulating layer and pentacene as an organic semiconductor, a pentacene thin film is formed directly on the gate insulating layer by a vacuum evaporation method. .

By the way, in order to manufacture a high-quality organic TFT with high mobility, adhesion at the interface between the gate insulating layer and the organic semiconductor layer when forming the organic semiconductor layer on the gate insulating layer is important. However, generally, metal oxide films such as SiO ₂ have high surface free energy, and generally organic semiconductors that are hydrophobic have poor wettability to these metal oxide films. Therefore, an attempt is made to improve the wettability of the organic semiconductor to the gate insulating layer by modifying the surface free energy of the gate insulating layer with a surface treatment agent such as octadecyltrichlorosilane (OTS) or hexamethyldisilazane (HMDS). (For example, refer to Patent Document 1).

  Furthermore, by treating the surface of the gate insulating film with a silane coupling agent having an aromatic group such as a phenyl group in the molecule, characteristics are improved by arranging an aromatic ring at the interface with the organic semiconductor material. And the technique that the fluctuation | variation of a threshold value is improved is disclosed (for example, refer patent documents 2-4).

  However, in these methods, the carrier mobility is still low, and when surface treatment is performed, the organic semiconductor solution is repelled, the applicability is greatly reduced, and a strong organic semiconductor layer cannot be provided. Has occurred.

On the other hand, the carrier mobility of organic FETs greatly depends on the crystallinity of the channel portion of the organic semiconductor layer formed on the surface of the insulating film, but it is difficult to form a smooth and uniform insulating film surface. In addition, particularly in the bottom contact type organic FET described later, since the source electrode and the drain electrode are formed on the substrate in advance when the semiconductor solution is applied, the high crystallinity like the top contact type organic FET. It has been difficult to form a semiconductor film.
JP 2004-327857 A International Publication No. 04/114371 Pamphlet JP 2005-158765 A US Patent Application Publication No. 2005/110006

  An object of the present invention is to provide an organic thin film transistor having high carrier mobility by solving the above problems and increasing the crystallinity of an organic semiconductor film (layer), and to provide a manufacturing method thereof.

  The above-mentioned problem according to the present invention is solved by the following means.

  1. An organic thin film transistor in which a source electrode and a drain electrode are formed on a substrate provided with a gate electrode and an insulating film, and an organic semiconductor layer is formed thereon, and each surface of the substrate, the source electrode and the drain electrode And the end of the monomolecular film bonded on the substrate and the end of the monomolecular film bonded to the surface of the source and drain electrodes have the same chemical structure Organic thin film transistor.

  2. 2. The organic thin film transistor according to 1 above, wherein an end of the monomolecular film bonded on the substrate and an end of the monomolecular film bonded to the surfaces of the source electrode and the drain electrode have an alkyl group.

  3. 3. The organic thin film transistor according to 1 or 2 above, wherein the end of the monomolecular film bonded on the substrate and the end of the monomolecular film bonded to the surfaces of the source electrode and the drain electrode are trialkylsilyl groups.

  4). 4. The organic thin film transistor according to any one of 1 to 3, wherein the organic semiconductor material forming the organic semiconductor layer is a compound having a molecular weight of 5000 or less.

  5. 5. The organic thin film transistor according to any one of 1 to 4, wherein the organic semiconductor material forming the organic semiconductor layer is a condensed polycyclic aromatic compound or a condensed polycyclic aromatic compound containing a hetero atom.

  6). A method for producing an organic thin film transistor having a gate electrode, an insulating film, a source electrode, a drain electrode, and an organic semiconductor layer on a substrate, wherein the organic thin film transistor according to any one of 1 to 5 is produced. A method for producing an organic thin film transistor.

  By the above means of the present invention, an organic thin film transistor with high carrier mobility can be provided by increasing the crystallinity of the organic semiconductor film (layer), and a manufacturing method thereof can be provided.

  In the organic thin film transistor of the present invention, a source electrode and a drain electrode (hereinafter also referred to as “source / drain electrodes”) are formed on a substrate provided with a gate electrode and an insulating film, and an organic semiconductor layer is formed thereon. In the formed organic thin film transistor, a monomolecular film is formed on each surface of the substrate, the source electrode, and the drain electrode, and the end of the monomolecular film bonded on the substrate, and on the surface of the source electrode and the drain electrode The terminal of the bonded monomolecular film is characterized by having the same chemical structure.

  Here, “the end of the monomolecular film” refers to the most distant from the binding surface of the molecule when the portion bonded to the substrate surface or the electrode surface in the chemical structure of the molecule constituting the monomolecular film is the tip. The chemical structure part (atomic group).

  Hereinafter, the present invention and its components will be described in detail.

(Configuration of organic thin film transistor)
First, in order to facilitate understanding of the outline of the present invention, a general configuration of an organic thin film transistor (hereinafter also referred to as “organic TFT”) will be described.

  FIG. 1 is a diagram illustrating a configuration example of an organic TFT. In FIG. 2A, a source electrode 2 and a drain electrode 3 are formed on a support (substrate) 6 with a metal foil or the like, and an organic semiconductor layer (film) 1 made of an organic semiconductor material is formed between both electrodes. An insulating layer 5 is formed thereon, and a gate electrode 4 is further formed thereon to form a field effect transistor. In FIG. 4B, the organic semiconductor layer (film) 1 formed between the electrodes in (a) is formed so as to cover the entire surface of the electrode and the support (substrate) using a coating method or the like. Represents. (C) First, an organic semiconductor layer (film) 1 is formed on a support (substrate) 6 using a coating method or the like, and then a source electrode 2, a drain electrode 3, an insulating layer 5, and a gate electrode 4 are formed. Represents what

  In FIG. 4D, after forming the gate electrode 4 with a metal foil or the like on the support (substrate) 6, the insulating layer 5 is formed, and the source electrode 2 and the drain electrode 3 are formed with the metal foil or the like thereon. The organic semiconductor layer 1 formed by the organic thin film transistor material of the present invention is formed between the electrodes. In addition, the configuration as shown in FIGS.

  As shown in FIG. 1, the organic thin film transistor has a source electrode and a drain electrode connected by an organic semiconductor channel (active layer, organic semiconductor layer) on a substrate, and a gate electrode via a gate insulating layer thereon. And a bottom gate having a source electrode and a drain electrode connected to each other by an organic semiconductor channel through a gate insulating layer. It is roughly divided into molds (FIGS. 1D to 1F). Among these, the organic thin film transistor of the present invention is an organic thin film transistor having a bottom gate type configuration. More specifically, in an organic thin film transistor in which a source electrode and a drain electrode are formed on a substrate provided with a gate electrode and an insulating film and an organic semiconductor layer is formed thereon, each of the substrate, the source electrode, and the drain electrode This is an organic thin film transistor in which a monomolecular film is formed on the surface of the thin film transistor.

(Formation of monomolecular film)
The organic thin film transistor of the present invention includes a source electrode and a drain electrode formed on a substrate provided with a gate electrode and an insulating film, and an organic semiconductor layer formed on the substrate, the source electrode and the drain. A monomolecular film is formed on each surface of the electrode, and the end of the monomolecular film bonded to the substrate and the end of the monomolecular film bonded to the surface of the source electrode and the drain electrode have the same chemical structure. It is characterized by having.

  In addition, it is preferable that a hetero atom exists within 10 cm from the outermost surface including the end of the monomolecular film.

  As the material for forming the monomolecular film according to the present invention, various simple substances, compounds, and the like can be used, but compounds used as surface treatment agents in the technical field according to the present invention should be used. Is preferred.

  In the present invention, it is particularly preferable to use a surface treating agent containing a compound having a terminal structure represented by the following general formula (1).

  As the surface treating agent according to the present invention, various compounds can be used as long as they are compounds having a terminal structure represented by the general formula (1), but they can adhere to the substrate surface or the like by a coupling reaction. A compound having a function is preferred. Details of the chemical structure of the surface treatment agent will be described later. By using the surface treating agent according to the present invention, when the surface of the substrate is surface treated, the contact angle of the surface with water can be increased, and as a result, the carrier mobility can be increased.

  The contact angle with respect to water on the surface after the surface treatment is preferably 50 degrees or more, more preferably 70 to 170 degrees, and further preferably 90 to 130 degrees. When the contact angle is low, the carrier mobility and on / off ratio of the transistor element are remarkably lowered, and when it is too high, the coating property of the organic semiconductor material solution is lowered. Here, the contact angle is a measured value when measured in an environment of 20 ° C. and 50% RH using a contact angle meter (for example, CA-DT • A type: manufactured by Kyowa Interface Science Co., Ltd.).

In the present invention, the surface free energy on the surface of the monomolecular film according to the present invention is preferably 1.0 × 10 ^{−2 to} 7.0 × 10 ⁻² Nm ⁻¹ . It was found that rather than the absolute value, the difference in the percentage ratio of the nonpolar component, polar component, and hydrogen bonding component of the surface free energy is important, and high carrier mobility can be obtained when the ratio is all within 15%.

  The surface free energy as referred to in the present invention can be measured by the following method.

  That is, the contact angles of three kinds of standard liquids with known surface free energies, hexane, methylene iodide, water, and the surface of the solid to be measured were each 5 by Kyowa Interface Science Co., Ltd .: contact angle meter CA-V. Measure once and average the measurements to get the average contact angle for each. The measurement is performed in an environment of 20 ° C. and 50% RH.

  Next, three components of the surface free energy of the solid surface can be calculated based on the following Young-Dupre equation and the extended Fowkes equation.

Young-Dupre equation W _SL = γ _L (1 + cos θ)
W _SL : Adhesion energy between liquid / solid γ _L : Surface free energy of liquid θ: Contact angle of liquid / solid Extended Fowkes' formula W _SL = 2 {(γ _S ^d γ _L ^d ) ^1/2 + (γ _{S ^{p γ L p) 1/2 + (}} γ S h γ L h) 1/2}
γ _L = γ _L ^d + γ _L ^p + γ _L ^h : surface free energy of liquid
γ _S = γ _S ^d + γ _S ^p + γ _S ^h : surface free energy of solid
γ ^d , γ ^p , γ ^h : dispersion of surface free energy, dipole, hydrogen bond component
γ _L (1 + cos θ) = 2 {(γ _S ^d γ _L ^d ) ^1/2 + (γ _S ^p γ _L ^p ) ^1/2 + (γ _S ^h γ _L ^h ) ^1/2 }
The surface free energy of n-hexane is known, and the three components γ _L ^d , γ _L ^p , and γ _L ^h are known (γ _L ^d = 18.4 mN / m, γ _L ^p , γ _L ^h = 0. Therefore, γ _S ^d of the insulator surface is obtained by the contact angle θ.

The contact angle θ of methylene iodide and the surface free energy of methylene iodide are known (γ _L ^d = 46.8 mN / m, γ _L ^p = 4.0 mN / m, γ _L ^h = 0), From this, γ _S ^{p on the} surface of the insulator is obtained.

Further, the contact angle θ of water and the surface free energy of water are known for the above three components (γ _L ^d = 29.1 mN / m, γ _L ^p = 1.3 mN / m, γ _L ^h = 42.4 mN / m. ) And γ _S ^{h on the} surface of the insulator can be obtained from this.

  In this way, the surface free energy of the solid can be determined from the surface free energies of the three solvents and the contact angles thereof. The combination is not necessarily limited to n-hexane, methylene iodide, and water, and other combinations may be selected, but the surface free energy of n-hexane is only a dispersion term and is easy to calculate.

  The surface free energy of these solvents can be referred from literature. For example, the data described in “Painting Technology Handbook-Basic / Measurement Evaluation Data-Ikuo Ishii, Jun Jun Koishi, Mitsuo Tsunoda 33”, “Basic Science of Coatings Yuji Harasaki, pp. 176-177” and the like (for example, , 20 ° C. data).

As for the surface free energy of the solvent, the value can be obtained from the above documents for typical materials, but for the solvents that are difficult to obtain in the literature, the surface free energy can be similarly determined using the above formula. Polyethylene, which is a solid polymer of known energy (see the above document) (surface free energy component is only γ _S ^d = 35.6 mN / m, γ _S ^p , γ _S ^h = 0), polytetrafluoride Ethylene (PTFE) (γ _S ^d = 19.4 mN / m, γ _S ^p = 2.1 mN / m, γ _S ^h = 0), polyvinylidene fluoride (γ _S ^d = 27.6 mN / m, γ 3) ( _S ^p = 9.1 mN / m, γ _S ^h = 3.5 mN / m). That is, it can be similarly obtained by measuring the contact angle of the solvent on these three types of polymer base materials.

<Terminal Structure Represented by General Formula (1)>
In the terminal structure represented by the general formula (1), X represents an atom of silicon (Si), germanium (Ge), tin (Sn), or lead (Pb). R _{1 to} R ₃ each represent a hydrogen atom or a substituent.

In the general formula (1), examples of the substituent represented by R _{1 to} R ₃ include an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group). Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group) , Propargyl group, etc.), aryl group (for example, phenyl group, naphthyl group, etc.), aromatic heterocyclic group (for example, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group) , Pyrazolyl group, thiazolyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group For example, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxyl group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cyclo An alkoxyl group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), an aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), an alkylthio group (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, Octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, , Methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group ( For example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group , 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, Chlohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy) Group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexyl group) Carbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, Phthalylcarbonylamino group, etc.), carbamoyl groups (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexyl) Aminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido) Group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ester Tylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group) Group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group (phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group etc.), amino group (for example, amino group, Ethylamino, dimethylamino, butylamino, cyclopentylamino, 2-ethylhexylamino, dodecylamino, anilino, naphthylamino, 2-pi Zircino group, etc.), halogen atoms (eg fluorine atom, chlorine atom, bromine atom etc.), fluorinated hydrocarbon groups (eg fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group etc.), And cyano group, nitro group, hydroxyl group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.).

  Of the above substituents, an alkyl group is particularly preferable, and specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a tert-butyl group.

In addition, said various substituents may be further substituted by said substituent. R ₁ , R ₂ and R ₃ may be the same or different from each other.

  Of the atoms represented by X, Si is particularly preferable.

<About the compound represented by the general formula (2)>
The surface treatment agent according to the present invention requires the use of a compound having a terminal structure represented by the general formula (1) as at least one surface treatment agent. It is a compound represented by General formula (2).

In the general formula (2), R ₁ to R ₃ and X have the same meanings as R ₁ to R ₃ and X in the general formula (1).

Examples of the linking group represented by Y include an alkylene group (for example, ethylene group, trimethylene group, tetramethylene group, propylene group, ethylethylene group, pentamethylene group, hexamethylene group, 2,2,4-trimethylhexamethylene group). , Heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, cyclohexylene group (for example, 1,6-cyclohexanediyl group, etc.), cyclopentylene group (for example, 1,5 -Cyclopentanediyl group etc.), alkenylene group (eg vinylene group, propenylene group etc.), alkynylene group (eg ethynylene group, 3-pentynylene group etc.), hydrocarbon group such as arylene group, hetero atom (For example, 2 containing a chalcogen atom such as —O— or —S—) Groups, -N (R) - group, where, R represents a hydrogen atom or an alkyl group, the alkyl group in the general formula (1), an alkyl group as defined represented by R ₁ ~ ₃ And the like.

  In each of the alkylene group, alkenylene group, alkynylene group, and arylene group, at least one of carbon atoms constituting the divalent linking group is a chalcogen atom (oxygen, sulfur, etc.) or -N (R). -It may be substituted with a group or the like.

  Furthermore, as the linking group represented by Y, for example, a group having a divalent heterocyclic group is used. For example, an oxazolediyl group, a pyrimidinediyl group, a pyridazinediyl group, a pyrandiyl group, a pyrrolinediyl group, an imidazolinediyl group. Group, imidazolidinediyl group, pyrazolidinediyl group, pyrazolinediyl group, piperidinediyl group, piperazinediyl group, morpholinediyl group, quinuclidinediyl group and the like, and thiophene-2,5-diyl group, It may be a divalent linking group derived from a compound having an aromatic heterocycle (also referred to as a heteroaromatic compound) such as a pyrazine-2,3-diyl group.

  Further, it may be a group that meets and links heteroatoms such as an alkylimino group, a dialkylsilanediyl group, or a diarylgermandiyl group.

  Of the above linking groups, preferred are hydrocarbon linking groups such as alkylene groups, alkenylene groups, alkynylene groups, and arylene groups.

  In the general formula (2), Z represents silicon (Si), titanium (Ti), germanium (Ge), tin (Sn), or lead (Pb), and among these atoms, Si is preferable. It is.

R _{4 to} R ₆ have the same meanings as R _{1 to} R ₃ in formula (1), but preferably have at least one of an alkoxyl group or a halogen atom as a substituent.

  Although the preferable specific example of a compound represented by General formula (2) below is shown, it is not limited to these.

  Each compound mentioned as these specific examples is, for example, Collect. Czech. Chem. Commun. 44, 750-755, J.M. Amer. Chem. Soc. 1990, 112, 2341-2348, Inorg. Chem. 10: 889-892, 1971, U.S. Pat. No. 3,668,233, etc., JP-A 58-122979, JP-A 7-242675, JP-A 9-61605, etc. 11-29585, JP-A No. 2000-64348, JP-A No. 2000-144097 and the like, or a synthesis method based on the synthesis method.

  In the present invention, in addition to the above surface treatment agent, the following silane compound can be used in combination. Specific examples include methyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxyethoxysilane, methyltriacetoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane. , Vinyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxyethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriacetoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, γ- Chloropropyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane Γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, β-cyanoethyltriethoxysilane, methyltriphenoxysilane, chloromethyltrimethylsilane Methoxysilane, chloromethyltriethoxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, α-glycidoxyethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, β-glycidoxy Ethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxyp Propyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, γ-glycid Xylpropyltrimethoxyethoxysilane, γ-glycidoxypropyltriphenoxysilane, α-glycidoxybutyltrimethoxysilane, α-glycidoxybutyltriethoxysilane, β-glycidoxybutyltrimethoxysilane, β-glycidyl Sidoxybutyltriethoxysilane, γ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, δ-glyoxydoxybutyltrimethoxysilane, δ-glyoxydoxybutyltriethoxysilane, (3, 4-epoxycyclohexyl) methyl Rutrimethoxysilane, (3,4-epoxycyclohexyl) methyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, β- ( 3,4-epoxycyclohexyl) ethyltripropoxysilane, β- (3,4-epoxycyclohexyl) ethyltributoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxyethoxysilane, γ- (3,4 Epoxycyclohexyl) propyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriphenoxysilane, γ- (3,4-epoxycyclohexyl) propyltrimethoxysilane, γ- (3,4-epoxycyclohexyl) propyltri Ethoxysila , Δ- (3,4-epoxycyclohexyl) butyltrimethoxysilane and other trialkoxysilanes, triacyloxysilanes, triphenoxysilanes; dimethyldimethoxysilane, phenylmethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldiethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropylmethyldiethoxysilane, dimethyldiacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ -Mercaptopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, methylvinyldimethoxysilane , Methylvinyldiethoxysilane, glycidoxymethylmethyldimethoxysilane, glycidoxymethylmethyldiethoxysilane, α-glycidoxyethylmethyldimethoxysilane, α-glycidoxyethylmethyldiethoxysilane, β-glycid Xylethylmethyldimethoxysilane, β-glycidoxyethylmethyldiethoxysilane, α-glycidoxypropylmethyldimethoxysilane, α-glycidoxypropylmethyldiethoxysilane, β-glycidoxypropylmethyldimethoxysilane, β- Glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldipropoxysilane, γ-glycidoxypropylmethyldibu Toxiethoxysilane, γ-glycidoxypropylmethyldimethoxyethoxysilane, γ-glycidoxypropylmethyldiphenoxysilane, γ-glycidoxypropylmethyldiacetoxysilane, γ-glycidoxypropylethyldimethoxysilane, γ-glycyl Sidoxypropylethyldiethoxysilane, γ-glycidoxypropylvinyldimethoxysilane, γ-glycidoxypropylvinyldiethoxysilane, γ-glycidoxypropylphenyldimethoxysilane, γ-glycidoxypropylphenyldiethoxysilane, etc. Dialkoxysilane, diphenoxysilane, diacyloxysilane, trimethylethoxysilane, trimethylmethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, dimethoxymethyl-3,3,3-tri Examples include, but are not limited to, fluoropropylsilane, fluoroalkylsilane, hexamethyldisilane, hexamethyldisiloxane, and the use of two or more different types at the same time even when used alone. You can also.

  Among the above compounds, methyltriethoxysilane, ethyltriethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, trimethylethoxysilane and the like are preferable.

  In addition, as another organosilicon compound, a compound represented by the following general formula (3) is used.

In general formula (3), n is 0-2000. R _{31 to} R ₃₈ are each a hydrogen atom or a linear, branched or cyclic hydrocarbon group which may be either saturated or unsaturated, and each may be the same or different.

  Specifically, a silicon compound reagent manufactured by Shin-Etsu Chemical Co., Ltd., or Gelest, Inc. of the United States. Among compounds listed in compound catalogs such as Metal-Organics for Material & Polymer Technology, Chisso's SILICON CHEMICALS, etc., compounds that meet general formula (3) can be selected and used. Illustratively, of course, but not limited to these.

  The compound for forming a monomolecular film on the surface of each of the source electrode and the drain electrode according to the present invention is preferably an organic compound having a group chemically bonded to a metal.

  Examples of the organic compound having a group chemically bonded to a metal include organic thiol compounds, organic disulfide compounds, organic sulfur compounds such as thioisocyanide, nitrile compounds such as isocyanide, and monoalkyl silanes.

  The organic compound is preferably a compound represented by the following general formula (M1), and more preferably a compound represented by the general formula (M2).

In General Formula (M1), A represents a functional group having a chemical bonding force with a metal, and is preferably a thiol group. L ₁ represents a divalent linking group selected from a substituted or unsubstituted alkylene group, cycloalkylene group, alkene-1,2-diyl group, alkyne-1,2-diyl group, and arylene group. Q represents a tetravalent atom selected from C, Si, Ge, Sn, and Pb, and is preferably Si. R _{1 to} R ₃ each represents a substituent selected from a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, cycloalkyl group, aryl group, heteroaryl group, and alkylsilyl group, which are linked together to form a ring. May be. R _{1 to} R ₃ are preferably substituted or unsubstituted alkyl groups.

In General Formula (M2), L ₂ represents a divalent linking group selected from a substituted or unsubstituted alkylene group, a cycloalkylene group, and an arylene group, and is preferably a substituted or unsubstituted alkylene group. R ₄ represents a substituent selected from a substituted or unsubstituted alkyl group, a cycloalkyl group, an aryl group, and an alkylsilyl group, and may be linked to each other to form a ring. R ₄ is preferably a substituted or unsubstituted alkyl group.

  Although the specific example of a compound represented by general formula (M1) or general formula (M2) below is shown, this invention is not limited to these.

[Method of forming monomolecular film]
The method for forming the monomolecular film is not particularly limited, but vacuum deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, atmospheric pressure plasma method (large Atmospheric pressure plasma CVD method), dip coating method, casting method, reel coating method, bar coating method, coating method such as die coating method, etc., and wet processes such as printing and ink-jet patterning methods, etc. it can.

  Among them, a method preferably used in the present invention includes a wet method in which a substrate is dipped in a surface treatment agent solution or a solution of a surface treatment agent is applied and dried, a plasma CVD method, preferably an atmospheric pressure plasma CVD method.

<Wet method>
In the wet method, for example, the substrate or the like is dipped in a surface treatment agent solution for an appropriate time and then dried, or the solution is applied onto a substrate or the like and dried.

(Plasma CVD method, atmospheric pressure plasma CVD method)
Thermal CVD that forms a thin film by a thermal reaction by supplying a reaction gas containing a surface treatment agent (in the plasma CVD method, a thin film forming material is also referred to as a raw material) onto a substrate heated in the range of 50 to 500 ° C. The effects of the present invention can also be obtained when using a general plasma CVD method performed under a reduced pressure of 0.01 to 100 Pa using a plasma method, an atmospheric pressure plasma method apparatus, a discharge gas, and a reactive gas. However, the atmospheric pressure plasma method is preferred from the viewpoints of improving mobility, thin film uniformity, thin film formation speed, and efficient production in a non-vacuum system.

  The gas to be used varies depending on the type of monomolecular film to be provided on the substrate, but basically, there is a discharge gas (inert gas) and a reactive gas containing a surface treatment agent for forming the monomolecular film. It is a mixed gas. It is preferable to contain 0.01-10 volume% of reaction gas with respect to mixed gas. Although it is more preferable that it is 0.1-10 volume%, More preferably, it is 0.1-5 volume%.

  Examples of the inert gas include Group 18 elements of the periodic table, specifically, helium, neon, argon, krypton, xenon, radon, nitrogen gas, and the like, in order to obtain the effects described in the present invention. For this, helium, argon, or nitrogen gas is preferably used.

  Moreover, the reaction is controlled by containing 0.01 to 5% by volume of a component selected from oxygen, ozone, hydrogen peroxide, carbon dioxide, carbon monoxide, hydrogen, and nitrogen in the mixed gas, and a high-quality thin film Can be formed.

  Moreover, in order to introduce the surface treatment agent of the reaction gas between the electrodes which are the discharge space, it may be in a state of gas, liquid or solid at normal temperature and pressure. In the case of gas, it can be introduced into the discharge space as it is, but in the case of liquid or solid, it is used after being vaporized by means such as heating, decompression or ultrasonic irradiation.

(Organic semiconductor film (layer))
As the organic semiconductor material constituting the organic semiconductor thin film (also referred to as “organic semiconductor thin layer”), various condensed polycyclic aromatic compounds and conjugated compounds described later can be applied.

  Examples of the condensed polycyclic aromatic compound as the organic semiconductor material include, for example, anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, circumcamanthracene, Examples thereof include bisanthene, zestrene, heptazethrene, pyranthrene, violanthene, isoviolanthene, cacobiphenyl, phthalocyanine, porphyrin, and derivatives thereof.

  Examples of the conjugated compound include polythiophene and its oligomer, polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, tetrathiafulvalene compound, quinone And compounds, cyano compounds such as tetracyanoquinodimethane, fullerenes and derivatives or mixtures thereof.

  In particular, among polythiophene and oligomers thereof, thiophene hexamer, α-seccithiophene α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3- Oligomers such as butoxypropyl) -α-sexithiophene can be suitably used.

Further, metal phthalocyanines such as copper phthalocyanine and fluorine-substituted copper phthalocyanine described in JP-A-11-251601, naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N'-bis (4-trifluoromethyl) Benzyl) naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N'-bis (1H, 1H-perfluorooctyl), N, N'-bis (1H, 1H-perfluorobutyl) and N, N '-Dioctylnaphthalene 1,4,5,8-tetracarboxylic acid diimide derivatives, naphthalene 2,3,6,7 tetracarboxylic acid diimides and other naphthalene tetracarboxylic acid diimides, and anthracene 2,3,6,7-tetra Condensed ring tet such as anthracene tetracarboxylic acid diimides such as carboxylic acid diimide Carboxylic acid diimides, fullerenes such as _{C 60, C 70, C 76} , C 78, C 84, carbon nanotube such as SWNT, merocyanine dyes, etc. dyes such hemicyanine dyes and the like.

  Among these π-conjugated materials, at least one selected from the group consisting of condensed polycyclic aromatic compounds such as pentacene, fullerenes, condensed ring tetracarboxylic acid diimides, and metal phthalocyanines is preferable.

  Other organic semiconductor materials include tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTTF-iodine complex, TCNQ-iodine complex. Organic molecular complexes such as can also be used. Furthermore, (sigma) conjugated polymers, such as polysilane and polygermane, and organic-inorganic hybrid material as described in Unexamined-Japanese-Patent No. 2000-260999 can also be used.

  In the present invention, as the organic semiconductor material, among the above-mentioned various compounds, condensed polycyclic aromatic compounds, particularly acenes, or condensed polycyclic aromatic compounds containing a hetero atom, particularly Si, S, O, N A condensed polycyclic aromatic compound containing a heteroatom such as Ge, that is, a derivative of a heteroacene is preferable. Particularly preferably, the hetero atom is substituted with a substituent outside the condensed ring. In addition, as a molecular weight, it is preferable that a weight average molecular weight is 5000 or less.

  Although the example of a preferable specific compound is given to the following, this invention is not limited to these.

  Exemplary compounds (4) and (6) are described in J. Org. A. C. S 2005, 127, 4986 to 4987, and other compounds can be synthesized with reference to the above-mentioned documents.

  In the present invention, the organic semiconductor film can be formed by various methods. In the formation of the organic semiconductor film by the coating method, the organic semiconductor film in the solution supply region is supplied between the supply of the coating liquid containing the organic semiconductor material and the drying. It is preferable to have a temperature difference of 5 ° C. or more and 100 ° C. or less in a direction parallel to the substrate surface. The temperature difference in the solution supply region may exist in a direction perpendicular to the substrate surface, that is, between the vicinity of the substrate of the wet film and the liquid surface, but more preferably in a direction parallel to the substrate surface. Furthermore, the temperature difference is preferably 5 ° C. or more and 50 ° C. or less.

  As a general coating method, spin coating or simply supplying a solution onto a substrate to form a film progresses in the direction of centrifugal force or radially from the end of the solution supply area. Thin film deposition proceeds isotropically. Therefore, the organic semiconductor crystal to be formed has a problem that a large number of crystal regions are formed and mobility is lowered due to the influence of the grain boundaries. As described above, by providing a temperature difference in the organic semiconductor solution supply region between the supply of the coating liquid containing the organic semiconductor material and the drying, the film is formed in a specific direction in the presence of the solvent in the solution supply region. By proceeding, a thin film having high orientation is formed.

  That is, by making the crystal growth direction constant in the region where the organic semiconductor material solution is supplied onto the substrate, the remaining region follows the stacking state of the molecules of the film formed in the initial stage and the solvent is volatilized. A thin film having the same stacked state is sequentially formed. As a result, a thin film having high crystallinity is formed in a wide range, and a high mobility thin film is formed.

  In addition, it is preferable that the temperature difference in a solution supply area | region is a fixed direction. Further, in order to generate a temperature gradient in the substrate, the substrate located in the layer between the organic semiconductor layer and the heating mechanism preferably contains a substance having low thermal conductivity, such as an inorganic oxide, an inorganic nitride, etc. Organic compounds, for example, organic compounds such as polyimide, and polymer compounds are also preferable.

  The insulator surface on which the organic semiconductor film is to be formed is, for example, the surface of a silicon wafer substrate with an oxide film in the case of a bottom gate type organic thin film transistor. A bottom-gate organic thin film transistor can be formed by forming an electrode and a drain electrode and connecting organic semiconductor layers. The silicon wafer also serves as a gate, and an oxide film (silicon oxide film) formed on the surface forms a gate insulating layer.

  Further, in the case of the top gate type, for example, an organic semiconductor layer is first formed on a support which is an insulator, a source electrode and a drain electrode are formed thereon, and a gate electrode is further formed thereon via a gate insulating layer. To form an organic thin film transistor. In this case, the organic semiconductor material solution is first applied, and the support (insulator) surface on which the organic semiconductor film (layer) is formed constitutes the insulator surface.

  In the present invention, the source / drain electrodes are preferably arranged in parallel to face the organic semiconductor film formed with a temperature gradient. By arranging in this way, high mobility is achieved.

  In any case, it is necessary to form an organic semiconductor film having a high carrier mobility on the substrate, that is, on the surface of the insulator serving as the substrate, and in order to form a TFT sheet having a fine structure, These organic semiconductor material solutions must be fine and can be applied to the substrate with high patterning accuracy.

  When these organic semiconductor films constitute an organic thin film transistor, they are formed on a substrate having a gate insulating film, for example, a highly hydrophobic insulating film such as a thermal oxide film of silicon, so that the organic semiconductor material is dissolved. As the solvent, the solvent having affinity with the surface to be applied preferably has a boiling point of 70 ° C. or higher and 250 ° C. or lower. For example, aromatic hydrocarbon such as toluene, chain aliphatic such as hexane and heptane Hydrocarbons, cycloaliphatic hydrocarbons such as cyclohexane and cyclopentane, aliphatic hydrocarbons, halogenated hydrocarbons such as chloroform and 1,2-dichloroethane, chain ethers such as diethyl ether and diisopropyl ether, tetrahydrofuran And cyclic ethers such as dioxane and ketones such as acetone and methyl ethyl ketone. These solvents may be used as a mixture. Further, in order to promote dissolution of the organic semiconductor material, another solvent having high solubility in the organic semiconductor material may be mixed and used.

  The content of the organic semiconductor material in the solvent varies depending on the type of solvent used and the selection of the organic semiconductor material. However, in order to form a thin film by applying these liquid materials on the substrate by coating, The organic semiconductor material is preferably dissolved in the range of 0.001 to 10.0% by mass, preferably 0.01 to 1.0% by mass. If the concentration is too high, uniform spreading on the substrate cannot be achieved, and if it is too low, pinholes of the coating film are likely to occur due to liquid breakage on the substrate.

  In the present invention, the organic semiconductor film can be formed on the substrate by applying the organic semiconductor material solution to the surface of the insulator (on the substrate) by cast coating, spin coating, printing, ink jetting, or the like, and drying.

  In the present invention, heat treatment may be performed at a predetermined temperature for a predetermined time after the organic semiconductor film (layer) is installed. As a result, it is possible to further strengthen and promote the molecular orientation or arrangement of the organic semiconductor material formed.

The heat treatment is preferably performed at a temperature below the melting point of the organic semiconductor material. In particular, when the organic semiconductor material has an exothermic peak in the differential scanning calorimetry (DSC) measurement, it is preferable to perform the treatment for a certain period of time at a temperature below the melting point and above the exothermic starting temperature. For example, the heat treatment is preferably performed for a certain period of time of 10 seconds to 1 week, preferably 10 seconds to 1 day, more preferably 10 seconds to 1 hour. This is because the heat treatment at a temperature equal to or higher than the melting point melts the organic semiconductor material, so that the formed oriented or crystallized film is melted and destroyed. Moreover, it is not preferable to expose to an excessively high temperature because decomposition and alteration of the organic semiconductor material itself occur. These heat treatments are preferably carried out in an inert gas such as nitrogen or helium or argon. Further, the pressure of these inert gases is preferably in the range of 0.7 × 10 ^{2 to} 1.3 × 10 ² kPa, that is, near atmospheric pressure.

  In the present invention, the substrate having an insulator surface on which the organic semiconductor film is formed varies depending on the manufacturing procedure such as a top gate type and a bottom gate type, which will be described later. Examples thereof include a gate insulating film (thermal oxide film formed on a polysilicon substrate) formed on the gate electrode. A top gate thin film transistor or the like is a substrate having an insulator surface on which an organic semiconductor film (layer) is first formed.

  In addition, when the condensed polycyclic aromatic compound is used as an organic semiconductor material, not only the organic semiconductor material but also, for example, acrylic acid, acetamide, dimethylamino group, cyano group, carboxyl group, nitro group, etc. in the organic semiconductor layer A material having a functional group, a material serving as an acceptor such as a benzoquinone derivative, tetracyanoethylene and tetracyanoquinodimethane or a derivative thereof, for example, an amino group, a triphenyl group, an alkyl group, Materials having functional groups such as hydroxyl group, alkoxy group, phenyl group, substituted amines such as phenylenediamine, anthracene, benzoanthracene, substituted benzoanthracene, pyrene, substituted pyrene, carbazole and derivatives thereof, tetrathiafulvalene and derivatives thereof, etc. It becomes a donor which is an electron donor like UNA is contained material may be subjected to so-called doping treatment. The method of forming an organic semiconductor film according to the present invention is also useful in structuring the organic semiconductor material molecules such as the orientation of the doped organic semiconductor film.

(Organic thin film transistor fabrication)
A method for producing a bottom gate type organic thin film transistor according to the present invention will be described.

  An organic thin film transistor is configured by optimally arranging a gate electrode, a gate insulating film, an active layer, a source electrode, and a drain electrode on a support.

  Therefore, for example, after forming the gate electrode on the support, forming the gate insulating film, and forming the active layer (organic semiconductor film (layer)) on the gate insulating film by the above-described method, the source, By forming the drain electrode, the organic thin film transistor of the present invention is formed. For example, after forming the gate insulating film, a source / drain electrode pattern may be formed on the gate insulating film, and an organic semiconductor layer may be formed by patterning between the source / drain electrodes.

  In this way, the gate electrode, gate insulating film, organic semiconductor film (layer), source electrode, and drain electrode are each appropriately patterned on the support, if necessary, and optimally arranged to provide the organic thin film transistor of the present invention. can get.

  Hereinafter, other components constituting the organic thin film transistor other than the organic semiconductor layer in the present invention will be described.

  In the present invention, the material for forming the source electrode, the drain electrode, and the gate electrode is not particularly limited as long as it is a conductive material, and various metal materials can be used. Platinum, gold, silver, nickel, chromium, Copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), fluorine-doped zinc oxide, zinc , Carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magne Palladium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, lithium / aluminum mixture, etc., especially platinum, gold, silver, copper Aluminum, indium, ITO, carbon and the like are preferable.

  As a method of forming an electrode, a method of forming an electrode using a known photolithographic method or a lift-off method with a conductive thin film formed using a method such as vapor deposition or sputtering using the above as a raw material, on a metal foil such as aluminum or copper In addition, there is a method of etching using a resist by thermal transfer, ink jet or the like.

  As an electrode forming method, there are a method of patterning a conductive fine particle dispersion, or a solution or dispersion of a conductive polymer directly by an ink jet method, and a method of forming a coating film by lithography, laser ablation, or the like. Furthermore, a method of patterning an ink containing a conductive polymer or conductive fine particles, a conductive paste, or the like by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used.

  Alternatively, a known conductive polymer whose conductivity is improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylenedioxythiophene and polystyrenesulfonic acid, or the like is also preferably used. Especially, a thing with little electrical resistance in a contact surface with an organic-semiconductor layer is preferable.

  Examples of conductive fine metal materials (metal fine particles) include platinum, gold, silver, cobalt, nickel, chromium, copper, iron, tin, antimony, lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium. Germanium, molybdenum, tungsten, zinc, and the like can be used, and platinum, gold, silver, copper, cobalt, chromium, iridium, nickel, palladium, molybdenum, and tungsten having a work function of 4.5 eV or more are particularly preferable.

  As a method for producing such a metal fine particle dispersion, metal ions can be reduced by reducing metal ions in a liquid phase such as a gas phase evaporation method, a sputtering method, a metal vapor synthesis method, or a liquid phase such as a colloid method or a coprecipitation method. Examples of the chemical production method for producing fine particles include colloidal methods described in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, JP-A-2000-239853, and the like. Dispersion of fine metal particles produced by a gas evaporation method described in JP-A Nos. 2001-254185, 2001-53028, 2001-35255, 2000-124157, 2000-123634, etc. It is a thing.

  The average particle diameter of the dispersed metal fine particles is preferably 20 nm or less.

  In addition, it is preferable to contain a conductive polymer in the metal fine particle dispersion. If the source electrode and the drain electrode are formed by patterning and pressing, heating, etc., ohmic contact with the organic semiconductor layer is possible with the conductive polymer. And can. That is, the effect of the present invention can be further enhanced by interposing a conductive polymer on the surface of the metal fine particles to reduce the contact resistance to the semiconductor and heat-fusing the metal fine particles.

  As the conductive polymer, a known conductive polymer whose conductivity has been improved by doping or the like is preferably used. For example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, polyethylenedioxythiophene and polystyrenesulfonic acid complex Etc. are preferably used.

  The content of the metal fine particles is preferably 0.00001 to 0.1 in terms of mass ratio with respect to the conductive polymer. If this amount is exceeded, fusion of the metal fine particles may be inhibited.

  When forming electrodes with these metal fine particle dispersions, it is preferable to heat-fuse the metal fine particles by heating after forming the source and drain electrodes. Further, at the time of electrode formation, a pressure of about 1 to 50000 Pa, and further about 1000 to 10000 Pa may be applied to promote fusion.

  In the case of patterning directly by an ink jet method as a method of patterning like an electrode using the fine metal particle dispersion, the ejection method of the ink jet head may be an on-demand type such as a piezo method or a bubble jet (registered trademark) method or an electrostatic method. A known method such as a continuous jet type ink jet method such as a suction method can be used.

  As a method of heating or pressurizing, a known method including a method used for a heating laminator or the like can be used.

  Various insulating films can be used as the gate insulating layer, and an inorganic oxide film having a high relative dielectric constant is particularly preferable.

  Examples of the inorganic oxide include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, strontium titanate, Examples thereof include barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and trioxide yttrium. Of these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide are preferable. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

  The inorganic oxide film can be formed by vacuum deposition, molecular beam epitaxy, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, atmospheric pressure plasma (atmospheric pressure) Plasma CVD method), dip coating method, casting method, reel coating method, bar coating method, method of forming by coating such as die coating method, and wet process such as a method of patterning such as printing or inkjet, etc. Can be used.

  The wet process is a method of applying and drying a liquid in which inorganic oxide fine particles are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as required, or an oxide precursor, for example, A so-called sol-gel method in which a solution of an alkoxide body is applied and dried is used.

  Of these, the atmospheric pressure plasma method and the sol-gel method are preferable.

  The method for forming an insulating film by the atmospheric pressure plasma method is a process in which a thin film is formed on a substrate by discharging at atmospheric pressure or a pressure in the vicinity of atmospheric pressure to excite a reactive gas to form a thin film on a substrate. 11-61406, 11-133205, JP-A 2000-121804, 2000-147209, 2000-185362, and the like. Thereby, a highly functional thin film can be formed with high productivity.

  These insulating films may be subjected to surface treatment in advance, and preferred examples of these treatments include treatment with a silane coupling agent as described above and alignment treatment such as rubbing.

  The organic compound film can be formed by using polyimide, polyamide, polyester, polyacrylate, photo radical polymerization system, photo cation polymerization system photo curable resin, copolymer containing acrylonitrile component, polyvinyl phenol, polyvinyl alcohol. , Novolak resin, cyanoethyl pullulan, and the like can also be used. As a method for forming the organic compound film, a wet process is preferable.

  An inorganic oxide film and an organic oxide film can be laminated and used together. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

  Moreover, a support body is comprised with glass or a flexible resin-made sheet | seat, for example, a plastic film can be used as a sheet | seat. Examples of the plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), Examples thereof include films made of cellulose triacetate (TAC), cellulose acetate propionate (CAP), and the like. By using a plastic film in this manner, the weight can be reduced as compared with the case of using a glass substrate, the portability can be improved and the resistance to impact can be improved.

  FIG. 2 is an example of a schematic equivalent circuit diagram of a TFT sheet configured like an output element such as a liquid crystal or an electrophoretic element using the organic thin film transistor.

  The TFT sheet 10 has a large number of organic TFTs 11 arranged in a matrix. 7 is a gate bus line of each organic TFT 11, and 8 is a source bus line of each organic TFT 11. For example, an output element 12 such as a liquid crystal or an electrophoretic element is connected to the source electrode of each organic TFT 11 to constitute a pixel in the display device. The pixel electrode may be used as an input electrode of the photosensor. In the illustrated example, a liquid crystal as an output element is shown by an equivalent circuit composed of a resistor and a capacitor. 13 is a storage capacitor, 14 is a vertical drive circuit, and 15 is a horizontal drive circuit.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “%” in the examples represents “mass%”.

(Production of organic thin film transistor)
A gate oxide film was formed by forming a thermal oxide film having a thickness of 200 nm on an n-type Si wafer having a specific resistance of 0.02 Ω · cm as a gate electrode. On this substrate, chromium and gold were patterned by photolithography to form a source electrode and a drain electrode having a channel length L = 20 μm and a channel width W = 5000 μm. Next, after cleaning the substrate, the source electrode and the drain electrode with oxygen plasma, a toluene solution (1 mass) in which the silane coupling agent shown in Table 1 is dissolved to form a monomolecular film on the surface of each substrate. %, 55 ° C.) for 10 minutes, washed with toluene and dried. Next, this substrate was immersed in a 1% toluene solution of the thiol compound shown in Table 1 at room temperature for 24 hours, washed with toluene, and dried.

  The percentage ratio of each component of the surface free energy with respect to the surface of the thermal oxide film after the surface treatment and the surface of the source / drain electrode was as shown in Table 1.

  Next, toluene was bubbled with nitrogen gas, the following organic semiconductor material was dissolved to prepare a 0.1% by mass solution, and this solution was dropped on the substrate to form an organic semiconductor layer. At this time, the average film thickness of the organic semiconductor layer was 50 nm.

About the produced organic thin-film transistor, the mobility of the field effect transistor was measured. In the measurement, the carrier mobility (cm ² / V · s) was obtained from the saturation region of the IV characteristic of the produced organic thin film transistor.

  The results are shown in Table 1.

  As is clear from the results shown in Table 1, it can be seen that the organic thin film transistor according to the present invention has a large and excellent carrier mobility.

The figure which shows the structural example of the organic thin-film transistor which concerns on this invention Schematic equivalent circuit diagram of the organic TFT sheet according to the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic-semiconductor layer 2 Source electrode 3 Drain electrode 4 Gate electrode 5 Insulating layer 6 Support body 7 Gate bus line 8 Source bus line 10 Organic TFT sheet 11 Organic TFT
12 Output element 13 Storage capacitor 14 Vertical drive circuit 15 Horizontal drive circuit

Claims (6)

An organic thin film transistor in which a source electrode and a drain electrode are formed on a substrate provided with a gate electrode and an insulating film, and an organic semiconductor layer is formed thereon, and each surface of the substrate, the source electrode and the drain electrode And the end of the monomolecular film bonded on the substrate and the end of the monomolecular film bonded to the surface of the source and drain electrodes have the same chemical structure Organic thin film transistor. The organic thin film transistor according to claim 1, wherein the end of the monomolecular film bonded on the substrate and the end of the monomolecular film bonded to the surface of the source electrode and the drain electrode have an alkyl group. 3. The organic thin film transistor according to claim 1 or 2, wherein the end of the monomolecular film bonded on the substrate and the end of the monomolecular film bonded to the surface of the source electrode and the drain electrode are trialkylsilyl groups. . The organic thin film transistor according to any one of claims 1 to 3, wherein an organic semiconductor material forming the organic semiconductor layer is a compound having a molecular weight of 5000 or less. The organic thin film transistor according to any one of claims 1 to 4, wherein the organic semiconductor material forming the organic semiconductor layer is a condensed polycyclic aromatic compound or a condensed polycyclic aromatic compound containing a hetero atom. . A method for producing an organic thin film transistor having a gate electrode, an insulating film, a source electrode, a drain electrode, and an organic semiconductor layer on a substrate, wherein the organic thin film transistor according to claim 1 is produced. A method for producing an organic thin film transistor characterized by the above.

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