JP2007287961A - Organic thin film transistor, and its method for manufacturing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin film transistor and its method for manufacturing which can manufacture by a simple wet process, excels in the transistor characteristics, and is excellent in time stability even in atmosphere or under high humidity. <P>SOLUTION: The organic thin film transistor having a gate electrode, a gate insulation layer, an organic semiconductor layer, a source electrode, and a drain electrode is characterized in that the organic semiconductor material forming the organic semiconductor layer contains 0.05-1,000 ppm of a compound having a condensed ring which is a condensation of at least two or more rings of either aromatic hydrocarbon ring or aromatic heterocycles, or both in a part of the structure and halogens. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic thin film transistor and a method for manufacturing the same.

  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, the information provided by paper media has increased the opportunity to be provided electronically, and as a mobile display medium that is thin, light and easy to carry, electronic paper or digital The need for paper is also increasing.

  In general, in a flat display device, a display medium is formed using an element utilizing liquid crystal, an organic electroluminescence element (hereinafter also referred to as organic EL), electrophoresis, or the like. In such a display medium, a technique using an active drive element composed of a thin film transistor (TFT) as an image drive element is becoming mainstream in order to ensure uniformity of screen brightness, screen rewrite speed, and the like.

  Here, the TFT element is usually made of a semiconductor thin film such as a-Si (amorphous silicon) or p-Si (polysilicon) or a metal thin film such as a source electrode, a drain electrode, or a gate electrode on a glass substrate. Manufactured by sequentially forming on top. In general, the manufacture of flat panel displays using TFTs requires high-precision photolithographic processes in addition to vacuum systems such as CVD and sputtering and thin film forming processes that require high-temperature processing processes. The load is very large, and furthermore, with the recent needs for a large display screen, their costs are extremely large.

  In recent years, research and development of organic TFT elements using organic semiconductor materials has been actively promoted as a technique for compensating for the disadvantages of conventional TFT elements (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1).

  Since the organic TFT element described in the above document can be manufactured by a low temperature process, it is said that a light and hard-to-break resin substrate can be used, and that a flexible display using a resin film as a support can be realized. (For example, see Non-Patent Document 2).

  By using an organic semiconductor material that can be manufactured by a wet process such as printing or coating under atmospheric pressure, a display with excellent productivity and a very low cost can be realized. In addition, various organic thin film transistors using organic semiconductors have been proposed, and it is described that they can be produced by a simple method by printing or an ink jet method (see, for example, Patent Document 1).

  As characteristics of organic transistors and field effect transistors, a current when a voltage is applied to a gate electrode (hereinafter referred to as an on-current) is large, and an on-current and a current when a voltage is not applied to the gate electrode (hereinafter referred to as an off-current). It is required that the ratio (on / off ratio) is large.

  In Patent Document 3, regarding a part of thiophene oligomer (organic semiconductor material) represented by α-nT and having a limited structure, a halide contained in the organic semiconductor material has an adverse effect on the on / off ratio. Is described.

However, Patent Document 3 only describes an organic semiconductor material having a limited structure, and when an organic semiconductor material that is difficult to form a film by a vapor deposition process is applied to the wet process described above. There is no description about the examination of. Unlike a vapor deposition process that includes a process similar to sublimation purification, the halide is a transistor characteristic in the case of a thin film transistor consisting of an organic semiconductor layer produced by a wet process in which impurities contained in the organic semiconductor material have a direct influence. The details of the impact on the current situation are not clear.
Japanese Patent Laid-Open No. 10-190001 JP 2000-307172 A JP-A-8-228035 Advanced Material 2002 2002 No. 2 page 99 (Review) SID'02 Digest p57

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an organic thin film transistor that can be manufactured by a simple wet process, has excellent transistor characteristics, and has excellent temporal stability even in air or at high humidity. The manufacturing method is provided.

  The above-described problems of the present invention are solved by the following means.

  1. In an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on a substrate, the organic semiconductor material forming the organic semiconductor layer is an aromatic hydrocarbon ring or an aromatic heterocyclic ring. An organic thin film transistor comprising 0.05 to 1000 ppm of a compound having a condensed ring in which one or both of them are condensed at least two or more in a part of the structure and a halogen element.

  2. 2. The organic thin film transistor according to 1 above, wherein the organic semiconductor material contains 0.1 to 100 ppm of a halogen element.

  3. 3. The organic thin film transistor according to 1 or 2 above, wherein the organic semiconductor material contains 0.1 to 10 ppm of a halogen element.

  4). 4. The organic thin film transistor according to any one of 1 to 3, wherein the halogen element is at least one halogen element selected from iodine, bromine, chlorine and fluorine.

  5. The halogen element derived from an organic semiconductor material forming the organic semiconductor layer or a raw material, reagent, or catalyst used when synthesizing the organic semiconductor material, 5. The organic thin film transistor according to any one of 4 above.

  6). 6. The organic thin film transistor as described in 5 above, wherein the halide derived from the organic semiconductor material is a synthetic intermediate or byproduct of the organic semiconductor material.

  7). The organic thin film transistor according to any one of 1 to 6, wherein the organic semiconductor material contains at least a compound represented by the general formula (1).

Wherein R _{1 to} R ₆ represent a hydrogen atom or a substituent, Z ₁ or Z ₂ represents a substituted or unsubstituted aromatic hydrocarbon ring, or a substituted or unsubstituted aromatic heterocyclic ring, and n1 or n2 represents an integer of 0 to 3.)
8). 8. The organic thin film transistor according to any one of 1 to 7, wherein the organic semiconductor material contains at least a compound represented by the general formula (2).

(Wherein R ₇ or R ₈ represents a hydrogen atom or a substituent, Z ₁ or Z ₂ represents a substituted or unsubstituted aromatic hydrocarbon ring, or a substituted or unsubstituted aromatic heterocyclic ring, n1 or n2 represents an integer of 0 to 3.)
9. 9. The organic thin film transistor according to 8 above, wherein the substituents R ₇ — and R ₈ — in the general formula (2) are represented by the general formula (3).

(Wherein R _{9 to} R ₁₁ represent a substituent, and X represents silicon (Si), germanium (Ge), or tin (Sn)).
10. 10. The organic thin film transistor according to any one of 1 to 9, wherein the organic semiconductor layer is a layer formed by a solution process using an organic solvent.

  11. A method for producing an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on a substrate, wherein the organic thin film transistor according to any one of 1 to 10 is produced. A method for producing an organic thin film transistor.

  With the above structure of the present invention, it is possible to provide an organic thin film transistor that can be manufactured by a simple wet process, has excellent transistor characteristics, and has excellent temporal stability even in the air or at high humidity, and a method for manufacturing the same.

  The organic thin film transistor of the present invention is an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on a substrate, wherein the organic semiconductor material forming the organic semiconductor layer is an aromatic hydrocarbon ring and It is characterized by containing 0.05 to 1000 ppm of a halogen element and a compound having a condensed ring in which one or both of aromatic heterocyclic rings are condensed in at least two or more rings.

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

《Organic thin film transistor》
An organic thin film transistor has a source electrode and a drain electrode connected by an organic semiconductor channel (active layer) on a substrate (also referred to as a “support”), and a top having a gate electrode on the gate electrode through the gate insulating layer. A gate type and a bottom gate type having first a gate electrode on a substrate and having a source electrode and a drain electrode connected by an organic semiconductor channel through a gate insulating layer. The organic thin film transistor of the present invention may be either a top gate type or a bottom gate type, and the form thereof is not limited.

(Organic semiconductor materials)
The organic semiconductor material that forms the organic semiconductor layer according to the present invention, that is, the organic semiconductor material that constitutes the organic semiconductor channel includes at least two rings of either an aromatic hydrocarbon ring or an aromatic heterocyclic ring. It contains a compound having a condensed ring condensed as a part of its structure.

Specifically, for example, pyrene, coronene, ovalen etc. and derivatives thereof, anthracene, pentacene etc. and derivatives thereof (acenes), condensed polycyclic hydrocarbons represented by rubrene and derivatives thereof, benzodithiophene, In addition to condensed polycyclic aromatic compounds containing heteroatoms such as anthradithiophene and derivatives thereof, oligomers and polymers composed of thienothiophene units described in JP-A-2005-76030 are also exemplified. be able to.
Among these, when a low molecular weight compound is used as the organic semiconductor material, the effect of the present invention is more exerted. In particular, when a low molecular weight organic semiconductor material having a number average molecular weight of 5000 or less is used, the organic thin film transistor is driven with high mobility. It is more preferable in obtaining.
Examples of pentacenes include pentacene derivatives having substituents described in WO03 / 16599, WO03 / 28125, USP6,690,029, JP-A-2004-107216, and the like described in US2003-136964 Pentacene precursor, JACS. vol127. Examples include acenes and derivatives thereof described in No. 14.4986 and the like.

  The organic semiconductor material is preferably a compound represented by the general formula (1).

In the general formula (1), R _{1 to} R ₆ each represent a hydrogen atom or a substituent, and Z ₁ and Z ₂ each represent a substituted or unsubstituted aromatic hydrocarbon ring, or a substituted or unsubstituted aromatic heterocyclic ring. , N1 and n2 represent an integer of 0 to 3.

Examples of the substituent represented by R _{1 to} R ₆ include an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl 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, triethylsilylethynyl group) , Triisopropylsilylethynyl group, propargyl group, etc.), aryl group (for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl) Group, indenyl group, pyrenyl group, Enrylyl group, etc.), aromatic heterocyclic group (for example, furyl group, thienyl group, pyridyl group, pyridazyl group, pyrimidyl group, pyrazyl group, triazyl group, imidazolyl group, pyrazolyl group, thiazolyl group, benzoimidazolyl group, benzooxazolyl group) Group, quinazolyl group, phthalazyl group, etc.), heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxyl group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyl) Oxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxyl group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group) Group, ethyl O 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.), alkoxy Carbonyl group (for example, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (for example, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.) Sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylamino group) Sulfonyl 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) Cyclohexylcarbonyl 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, ethyl group) Bonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc. ), Carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylamino) Carbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), urea Id 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, ethylsulfinyl 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, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group For example, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group) Group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, penta) Fluoroethyl group, pentafluorophenyl group, etc.), cyano group, silyl group (for example, trimethylsilyl group, triethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.).

  These substituents may be further substituted with the above substituents, or a plurality thereof may be bonded to each other to form a ring.

Examples of the substituted or unsubstituted aromatic hydrocarbon ring represented by Z ₁ and Z ₂ include a phenyl group, a p-chlorophenyl group, a mesityl group, a tolyl group, a xylyl group, a naphthyl group, an anthryl group, an azulenyl group, Examples include acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group and the like.

Examples of the substituted or unsubstituted aromatic heterocycle represented by Z ₁ and Z ₂ include a furyl group, a thienyl group, a pyridyl group, a pyridazyl group, a pyrimidyl group, a pyrazyl group, a triazyl group, an imidazolyl group, a pyrazolyl group, A thiazolyl group, a benzimidazolyl group, a benzoxazolyl group, a quinazolyl group, a phthalazyl group, and the like can be given.

  Moreover, as an organic-semiconductor material, the compound represented by the said General formula (2) is preferable.

In the general formula (2), R ₇ and R ₈ represent a hydrogen atom or a substituent, and Z ₁ and Z ₂ represent a substituted or unsubstituted aromatic hydrocarbon ring, or a substituted or unsubstituted aromatic heterocyclic ring. , N1 and n2 represent an integer of 0 to 3.

As the substituent represented by R _7, R _8, is synonymous with the substituent represented by R ₁ to R ₆ in the general formula (1).

Z _1, the aromatic hydrocarbon ring or a substituted or unsubstituted represented by Z _2, Z _1, aromatic substituted or unsubstituted represented by Z ₂ hydrocarbon ring as defined in the general formula (1) It is.

The Z _1, a substituted or unsubstituted aromatic heterocyclic represented by Z _2, a substituted or unsubstituted aromatic heterocyclic synonymous represented by Z _1, Z ₂ in the general formula (1) .

The substituents R ₇ and R ₈ in the general formula (2) are preferably represented by the general formula (3).

In General formula (3), R < ₉ > -R < ₁₁ > represents a substituent and X represents silicon (Si), germanium (Ge), or tin (Sn).

As a substituent represented by R < ₉ > -R < ₁₁ >, it is synonymous with the substituent represented by R < ₁ > -R < ₆ > of the said General formula (1). X is preferably Si or Ge.

  Examples of these include the following compounds, but the present invention is not limited thereto.

(Measurement method of halogen element content)
The organic semiconductor material forming the organic semiconductor layer according to the present invention contains 0.05 to 1000 ppm of a halogen element, preferably 0.1 to 100 ppm of a halogen element, more preferably 0.1 to 10 ppm of a halogen element. contains.

  The halogen element contained in the organic semiconductor material according to the present invention is specifically at least one halogen element selected from iodine, bromine, chlorine or fluorine.

  The content of the halogen element in the case where two or more kinds of the halogen element are contained in the organic semiconductor material is determined from the total amount of the halogen element concentrations.

  The halogen element contained in the organic semiconductor material is derived from a synthetic intermediate or by-product of the organic semiconductor material, or a raw material, reagent, or catalyst used when synthesizing the organic semiconductor material. Here, the “reagent” refers to a substance that attacks a substrate (substance on the reaction side) in the reaction. In general, in an organic reaction, the reaction point at the carbon atom is called a substrate, and the other atom is called a reagent, but when both reaction points are carbon atoms, the one with the more remarkable reactivity is called. It is called a reagent. Examples of the reagent containing a halogen element include Grignard reagents such as alkylmagnesium chloride. Examples of the catalyst containing a halogen element include tin chloride, but the present invention is not limited thereto. The halogen element may be contained in the organic semiconductor material in various forms as a halogen molecule alone such as an iodine molecule or a bromine molecule, or as a halide such as iodide or bromide. That's fine.

  The halogen element contained in the organic semiconductor material according to the present invention can be detected by an inductively coupled plasma-mass spectrometry (ICP-MS) apparatus. ICP-MS is a device that performs mass analysis of atoms ionized by high-temperature plasma generated by high-frequency power, and enables elemental analysis in the order of ppt.

  Another method includes a coulometric titration method. For example, when detecting the chlorine concentration, the sample is induced into AgCl from HCl gas generated by completely burning the sample in oxygen, and this is titrated as the amount of chlorine. In ICP-MS analysis, if a large amount of chemical species with the same mass is contained in the background, quantitative trace analysis becomes difficult, and therefore, coulometric titration is particularly effective for detection of chlorine and fluorine. Moreover, the method of detecting the chlorine ion density | concentration extracted by trapping the generated HCl gas with an ultrapure water by an ion chromatograph can also be mentioned.

  In the present invention, the method for forming the organic semiconductor layer is typified by an evaporation process formed by vacuum evaporation, a coating method such as cast coating, dip coating, or spin coating, or a printing method such as inkjet printing or screen printing. In the present invention, it is preferable to form the organic semiconductor film on the substrate by a solution process using an organic solvent.

(Type of organic solvent)
The organic solvent according to the present invention is not particularly limited, but is preferably selected from aromatic hydrocarbons, aromatic halogenated hydrocarbons, aliphatic hydrocarbons or aliphatic halogenated hydrocarbons, aromatic hydrocarbons or aromatics More preferred are halogenated hydrocarbons or aliphatic hydrocarbons.
Examples of the organic solvent comprising an aromatic hydrocarbon used in the present invention include toluene, xylene, mesitylene, methylnaphthalene and the like, but the present invention is not limited to these.

  Examples of the organic solvent for the aromatic halogenated hydrocarbon include chlorobenzene, bromobenzene, iodobenzene, o-dichlorobenzene, m-dichlorobenzene, o-dibromobenzene, m-dibromobenzene, o-diiodobenzene, m- Diiodobenzene, chlorotoluene, bromotoluene, iodotoluene, dichlorotoluene, dibromotoluene, difluorotoluene, chloroxylene, bromoxylene, iodoxylene, chloroethylbenzene, bromoethylbenzene, iodoethylbenzene, dichloroethylbenzene, dibromoethylbenzene, chlorocyclopentadiene, Although chlorocyclopentadiene etc. can be mentioned, this invention is not limited to these.

  Examples of the aliphatic hydrocarbon organic solvent include octane, 4-methylheptane, 2-methylheptane, 3-methylheptane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,4-dimethylhexane, 2,5-dimethylhexane, 3,3-dimethylhexane, 3,4-dimethylhexane, 3-ethylhexane, 2,2,3-trimethylpentane, 2,2,4-trimethylpentane, 2,3,3- Trimethylpentane, 2,3,4-trimethylpentane, 2-methyl-3-ethylpentane, 3-methyl-3-ethylpentane, decane, 2,2,3,3-tetramethylhexane, 2,2,5, 5-tetramethylhexane, 3,3,5-trimethylheptane, nonane, 2,2,5-trimethylhexane, 4-ethylheptane, 2,3-di Tilheptane, 2-methyloctane, dodecane, hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, heptane, 2-methylhexane, 3-methylhexane, 2,2 -Chain aliphatic hydrocarbons such as dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, 2,2,3-trimethylbutane, cyclohexane, cyclo Examples include cycloaliphatic hydrocarbons such as pentane, methylcyclohexane, methylcyclopentane, p-menthane, decalin, and cyclohexylbenzene, but the present invention is not limited thereto. As the aliphatic hydrocarbon used in the present invention, a cyclic aliphatic hydrocarbon is preferable.

Examples of the organic solvent for the aliphatic halogenated hydrocarbon include chloroform, bromoform, dichloromethane, dichloroethane, trichloroethane, difluoroethane, fluorochloroethane, chloropropane, dichloropropane, chloropentane, and chlorohexane. It is not limited to these.
These organic solvents used in the present invention may be used alone or in combination of two or more.

  The organic solvent according to the present invention preferably has a boiling point of 50 ° C to 250 ° C. In adjusting the amount of the organic solvent to be contained in the organic semiconductor layer, if the boiling point of the organic solvent is lower than 50 ° C., the volatility becomes too high, so it is difficult to keep a desired amount of the organic solvent in the organic semiconductor layer. When the temperature is higher than 250 ° C., it is necessary to expose the organic semiconductor layer at an unnecessarily high temperature in order to adjust the amount of the organic solvent contained in the organic semiconductor layer to a desired amount. The result is unfavorable.

  The substrate used in the present invention may be subjected to surface treatment in advance. As the surface treatment, it is more preferable to form a self-aligned thin film on the substrate, such as a treatment with a silane coupling agent. Examples of the silane coupling agent include octadecyltrichlorosilane, nonyltrichlorosilane, octyltrichlorosilane, octyltrimethoxysilane, octyltriethoxysilane, n-butyltrichlorosilane, i-butyltrichlorosilane, ethyltrichlorosilane, methyltrichlorosilane, Known trimethylchlorosilane, hexamethyldisilazane, 4-phenylbutyltrichlorosilane, 3-phenoxypropyltrichlorosilane, phenyltrichlorosilane, cyclohexyltrichlorosilane, heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane Although a material is mentioned as a preferable example, this invention is not restricted to these. As a surface treatment method using a silane coupling agent, a known method as disclosed in JP-A Nos. 2004-327857, 2005-32774, 2005-158765, and the like is applied. Can do. For example, a vapor phase method such as a CVD method, a liquid phase method such as a spin coating method or a dip coating method, and a printing method such as a screen printing method, a micromold method, a micro contact method, and an ink jet method can be applied.

  Further, before the treatment with the silane coupling agent, the surface of the substrate (for example, an insulating film such as a thermal oxide film formed on the silicon substrate) is subjected to a hydrophilic treatment (surface such as oxygen plasma treatment or UV ozone treatment). Is generally preferred to form a dense and strong self-assembled monolayer, and is described in the above-mentioned patent documents and the like. ing. Furthermore, generally well-known orientation treatment such as rubbing may be performed.

  The organic thin film transistor according to the present invention is a protective film (sealing) that protects an organic semiconductor film by using a known inorganic material or organic polymer material on the organic semiconductor layer or the organic thin film transistor itself constituted by necessary components. Film) may be formed. As a method for forming the protective film, a known technique as described in JP-T-2003-525521, JP-A-2004-506985, JP-A-2002-314093, JP-A-2003-258164, or the like is applied. be able to. In addition, an insulating film used as a gate insulating layer, which will be described later, can be applied as a protective film, and a support described later can be further attached onto an organic thin film transistor prepared on the support, or laminated with a polymer sheet. Thus, a protective film may be formed.

  Although there is no restriction | limiting in particular as the film thickness of the organic-semiconductor layer formed in this invention, The characteristic of the obtained organic thin-film transistor (TFT) is largely influenced by the film-thickness of a semiconductor layer, The film thickness Although it varies depending on the semiconductor material, it is generally 1 μm or less, particularly preferably 10 to 300 nm.

  The organic semiconductor layer includes, for example, materials having functional groups such as acrylic acid, acetamide, dimethylamino group, cyano group, carboxyl group, nitro group, benzoquinone derivatives, tetracyanoethylene and tetracyanoquinodimethane, and the like. Materials that accept electrons such as derivatives thereof, materials having functional groups such as amino group, triphenyl group, alkyl group, hydroxyl group, alkoxy group, and phenyl group, substituted amines such as phenylenediamine , So-called doping treatment, containing a material that becomes a donor as an electron donor, such as anthracene, benzoanthracene, substituted benzoanthracenes, pyrene, substituted pyrene, carbazole and its derivatives, tetrathiafulvalene and its derivatives, etc. You can give .

  The doping means introducing an electron-donating molecule (acceptor) or an electron-donating molecule (donor) into the thin film as a dopant. Therefore, the doped thin film is a thin film containing the organic semiconductor material and dopant used in the present invention. Any of an acceptor and a donor can be used as the dopant used in the present invention. A known material can be used as the acceptor and donor, and a known process can be used for the introduction thereof.

  Taking the bottom gate type organic thin film transistor as one of the preferred embodiments of the present invention as an example, the organic thin film transistor includes a gate electrode, a gate insulating film, an active layer, a source electrode, and a drain electrode optimally provided on a support. It is constituted by being arranged.

  Therefore, for example, after forming the gate electrode on the support, forming the gate insulating film, and forming the active layer (organic semiconductor layer (thin film)) on the gate insulating film by the above method, respectively, The organic thin film transistor according to the present invention is formed by forming the source and drain electrodes.

  Further, 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 channel may be formed by patterning between the source / drain electrodes.

  As described above, the gate electrode, the gate insulating film, the active layer (organic semiconductor layer), the source electrode, and the drain electrode are appropriately patterned and optimally arranged on the support, respectively, so that the organic layer of the present invention can be obtained. A thin film transistor is obtained.

  Hereinafter, other components constituting the organic thin film transistor other than the active layer (organic semiconductor layer (thin film)) of the organic thin film transistor obtained by the production method of the present invention will be described.

  In the present invention, the material for forming the source electrode, drain electrode and gate electrode is not particularly limited as long as it is a conductive material. 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-potassium alloy, magnesium / copper mixture, magnesium / silver mixture, magnesium Neshiumu / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, lithium / aluminum mixture is used, in particular platinum, gold, silver, copper, aluminum, indium, ITO and carbon are preferable. Alternatively, a known conductive polymer whose conductivity has been 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. Among them, those having low electrical resistance at the contact surface with the semiconductor layer are preferable.

  As a method for forming an electrode, a method for forming an electrode using a known photolithographic method or a lift-off method, using a conductive thin film formed by a method such as vapor deposition or sputtering using the above as a raw material, or a metal foil such as aluminum or copper There is a method of forming an electrode using a resist by thermal transfer, ink jet or the like. Alternatively, a conductive polymer solution or dispersion, or a conductive fine particle dispersion may be directly patterned by inkjet, or may be formed from a coating film by lithography or laser ablation. 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.

  In the present invention, the source and drain electrodes are preferably formed from a fluid electrode material such as a solution or dispersion of the conductive polymer or a conductive fine particle dispersion. For example, conductive fine particles made of metal or the like are used. , Preferably using a dispersion stabilizer made of an organic material, dispersed in a dispersion medium that is water, an organic solvent, or a mixture thereof to form a conductive fine particle dispersion such as paste or ink, which is then coated and patterned. Thus, it is preferable to form an electrode.

  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 are reduced in the liquid phase, such as a physical generation method such as gas evaporation method, sputtering method, metal vapor synthesis method, colloid method, coprecipitation method, etc. Examples of the chemical production method for producing metal fine particles include colloidal methods described in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, JP-A2000-239853, and the like. It is a metal fine particle dispersion produced by a gas evaporation method described in JP-A Nos. 2001-254185, 2001-53028, 2001-35255, 2000-124157, 2000-123634, and the like. .

  The average particle diameter of the dispersed metal fine particles is preferably 20 nm or less from the viewpoint of the effect of the present invention.

  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, reducing the contact resistance to the semiconductor, and thermally fusing the metal fine particles.

  As the conductive polymer, it is preferable to use a known conductive polymer whose conductivity has been improved by doping or the like. For example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, 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.

  After forming an electrode with these metal fine particle dispersions, the metal fine particles are thermally fused to form source and drain electrodes. Further, it is also preferable to promote fusion by applying a pressure of about 1 to 50000 Pa, more preferably about 1000 to 10000 Pa at the time of electrode formation.

  As a method of patterning like an electrode using the metal fine particle dispersion, for example, there is a patterning method by a printing method using the metal fine particle dispersion as an ink. In addition, there is a method of patterning by an ink jet method, which is a method of discharging a metal fine particle dispersion from an ink jet head and patterning the metal fine particle dispersion. As a method of discharging from the ink jet head, a piezo method, a bubble jet, etc. Patterning can be performed by a known method such as an on-demand type such as a (registered trademark) type or a continuous jet type ink jet method such as an electrostatic suction type.

  As a method of heating or pressurizing, known methods such as a method used for a heating laminator 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.

  Inorganic oxides 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, titanium Examples thereof include barium oxide, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. 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 film formation method includes vacuum deposition, molecular beam epitaxial growth, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, atmospheric pressure plasma method (atmospheric pressure plasma CVD method). There are wet processes such as a dip coating method, a casting method, a reel coating method, a bar coating method, a coating method such as a die coating method, and a patterning method such as printing and ink jetting, which can be used depending on the material.

  The wet process is a method of applying and drying a liquid in which fine particles of inorganic oxide 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 is preferred.

  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.

  The organic compound film can be formed by using polyimide, polyamide, polyester, polyacrylate, photo radical polymerization system, photo cation polymerization system photo-curing resin, or copolymer containing acrylonitrile component, polyvinyl phenol, polyvinyl alcohol. , Novolak resin, cyanoethyl pullulan, and the like can also be used.

  The wet process is preferred as the method for forming the organic compound film.

  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), and cellulose. Examples include films made of triacetate (TAC), cellulose acetate propionate (CAP), and the like. Thus, by using a plastic film, it is possible to reduce the weight as compared with the case of using a glass substrate, to improve portability, and to improve resistance to impact.
In particular, when a plastic film is used as a support, for example, in order to protect organic thin film transistor elements from oxygen, liquid (water), light, etc., including a gas barrier layer as disclosed in JP-A-2004-134694. It is preferable to further have a barrier layer having at least one layer or a multilayer structure.

  FIG. 1 shows a configuration example of an organic thin film transistor (TFT) according to the present invention.

  FIG. 4A shows a layer containing metal fine particles formed on a support (substrate) 6 by patterning gold or the like by vapor deposition using a mask, or after forming a pattern of layers containing metal fine particles. The source electrode 2 and the drain electrode 3 are formed by heating and pressurizing and the organic semiconductor material layer 1 is formed between the source and drain electrodes, and the gate insulating layer 5 is formed thereon. A gate electrode 4 is formed thereon to form an organic TFT.

  FIGS. 1B and 1C show other configuration examples of the top gate type organic thin film transistor.

  1D to 1F show configuration examples of bottom-gate organic TFTs. In FIG. 4D, after the gate electrode 4 is formed on the support 6, the gate insulating layer 5 is formed, the source electrode 2 and the drain electrode 3 are formed thereon, and the gate between the source and drain electrodes is formed. A bottom gate type organic TFT is formed by forming an organic semiconductor material layer 1 on an insulating layer. Similarly, other configuration examples are shown in (e) and (f). In particular, FIG. 5F shows that after forming the gate electrode 4 on the support 6, the gate insulating layer 5 is formed, the organic semiconductor material layer 1 is formed thereon, and then the source electrode 2 and the drain electrode 3 are further formed. To form an organic TFT.

  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. 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, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Production of TFT element >>
An organic thin film transistor element (hereinafter referred to as “TFT element”) 1 having the layer structure shown in FIG. 1 (f) was produced by the following method.

  First, a thermal oxide film having a thickness of 2000 mm was formed on a Si wafer having a specific resistance of 0.02 Ω · cm as the gate electrode 4 to form the gate insulating layer 5.

  Next, this was immersed in a 1% toluene solution of octyltrichlorosilane heated to 60 ° C. for 10 minutes, washed with toluene, and dried to perform surface treatment with octyltrichlorosilane.

  A 0.5% cyclohexane solution of Compound 1 (lot 1) was spin-coated (1000 rpm, 30 seconds) on the gate insulating layer 5 subjected to this surface treatment to form a coating film (thickness 25 nm). Further, gold was deposited on the surface of the coating film using a mask to form the source electrode 2 and the drain electrode 3.

  As described above, a TFT element 1 having a source electrode 2 and a drain electrode 3 each having a width of 100 μm and a thickness of 200 nm, a channel width W = 5 mm, and a channel length L = 50 μm was produced.

  Next, in the production of the TFT element 1, instead of the compound 1 (lot. 1), compounds 1 (lot. 2) to 1 (lot. 8) having halogen element contents as shown in Table 1 are used. The TFT elements 2 to 8 were produced in the same manner as the TFT element 1 except for the above.

  In addition, compound 1 is JACS. , 2001, 123, 9482-9443.

  The halogen element content in each lot was adjusted as shown in Table 1 by changing the purification means and the number of purifications (specifically, separation and recrystallization by silica gel column chromatography).

  The concentration of the halogen element in the organic semiconductor material was determined by burning a 500 mg sample using a temperature rising combustion furnace (manufactured by Dia Instruments Co., Ltd.), absorbing the generated hydrogen halide gas in ultrapure water, and then concentrating ion chromatography. It was determined by quantifying with a graph.

<< Evaluation of TFT element >>
(Transistor characteristics)
The TFT elements 1 to 8 fabricated as described above showed the operating characteristics of a p-channel enhancement type FET. For each TFT element, the carrier mobility is obtained from the saturation region of the IV characteristic, and further the ON / OFF ratio (the drain bias value is 40 V, the drain current value ratio when the gate bias is -50 V and 0 V) is obtained. The results are shown in Table 1. In addition, the carrier mobility and the ON / OFF ratio when left for 1 month under conditions of a temperature of 25 ° C. and a humidity of 45% were also evaluated and shown in Table 1.

  From the results shown in Table 1, the organic thin film transistor of the present invention in which the organic semiconductor material contains a halogen element of 0.05 to 1000 ppm clearly has better transistor characteristics (carrier mobility, ON / OFF ratio) than the comparison. It turns out that. Furthermore, it turned out that the organic thin-film transistor of this invention is excellent also in temporal stability compared with the comparison.

(Example 2)
<< Production of TFT element >>
In the same manner as in Example 1, a gate oxide layer 5 was formed by forming a thermal oxide film having a thickness of 2000 mm (200 nm) on a Si wafer having a specific resistance of 0.02 Ω · cm as the gate electrode 4. Next, while heating this on a hot plate in a nitrogen atmosphere, a 0.1% toluene solution of Compound 1 (lot. 1) is developed on the surface of the gate insulating layer, and a coating film (thickness) is formed on the entire surface. 25 nm).

  Further, in the same manner as in Example 1, the source electrode 2 and the drain electrode 3 were formed, and the TFT element 9 was produced.

  The TFT elements 10 to 16 were produced in the same manner as the TFT element 9. Table 2 shows each lot of Compound 1 used in each device fabrication.

<< Evaluation of TFT element >>
(Transistor characteristics)
The results of evaluating the transistor characteristics of the TFT elements 10 to 16 in the same manner as in Example 1 are shown in Table 2.

  From the results shown in Example 2, the organic thin film transistor of the present invention in which the organic semiconductor material contains a halogen element of 0.05 to 1000 ppm clearly shows the transistor characteristics (carrier mobility, ON / OFF ratio) as compared with the comparison. It was found to be good. Furthermore, it turned out that the organic thin-film transistor of this invention is excellent also in temporal stability compared with the comparison.

  From the above results, it was found that the present invention is an organic thin film transistor that can be produced by a simple wet process, has excellent transistor characteristics (carrier mobility, ON / OFF ratio), and has excellent temporal stability in the atmosphere.

The figure which shows the structural example of the organic thin-film transistor of this invention The figure which shows one example of the schematic equivalent circuit of the organic thin-film transistor of this 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 (board | substrate)
7 Gate bus line 8 Source bus line 10 TFT sheet 11 Organic TFT
12 Output element 13 Storage capacitor 14 Vertical drive circuit 15 Horizontal drive circuit

Claims (11)

In an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on a substrate, the organic semiconductor material forming the organic semiconductor layer is an aromatic hydrocarbon ring or an aromatic heterocyclic ring. An organic thin film transistor comprising 0.05 to 1000 ppm of a compound having a condensed ring in which one or both of them are condensed at least two or more in a part of the structure and a halogen element. The organic thin film transistor according to claim 1, wherein the organic semiconductor material contains 0.1 to 100 ppm of a halogen element. The organic thin film transistor according to claim 1 or 2, wherein the organic semiconductor material contains 0.1 to 10 ppm of a halogen element. The organic thin film transistor according to any one of claims 1 to 3, wherein the halogen element is at least one halogen element selected from iodine, bromine, chlorine, and fluorine. 2. The halogen element is derived from a halide derived from an organic semiconductor material forming the organic semiconductor layer, or a raw material, reagent, or catalyst used in synthesizing the organic semiconductor material. The organic thin-film transistor as described in any one of -4. 6. The organic thin film transistor according to claim 5, wherein the halide derived from the organic semiconductor material is a synthetic intermediate or byproduct of the organic semiconductor material. The organic thin film transistor according to any one of claims 1 to 6, wherein the organic semiconductor material contains at least a compound represented by the general formula (1).

Wherein R _{1 to} R ₆ represent a hydrogen atom or a substituent, Z ₁ or Z ₂ represents a substituted or unsubstituted aromatic hydrocarbon ring, or a substituted or unsubstituted aromatic heterocyclic ring, and n1 or n2 represents an integer of 0 to 3.) The organic thin film transistor according to any one of claims 1 to 7, wherein the organic semiconductor material contains at least a compound represented by the general formula (2).

(Wherein R ₇ or R ₈ represents a hydrogen atom or a substituent, Z ₁ or Z ₂ represents a substituted or unsubstituted aromatic hydrocarbon ring, or a substituted or unsubstituted aromatic heterocyclic ring, n1 or n2 represents an integer of 0 to 3.) The organic thin film transistor according to claim 8, wherein the substituents R ₇ — and R ₈ — in the general formula (2) are represented by the general formula (3).

(Wherein R _{9 to} R ₁₁ represent a substituent, and X represents silicon (Si), germanium (Ge), or tin (Sn)). The organic thin film transistor according to claim 1, wherein the organic semiconductor layer is a layer formed by a solution process using an organic solvent. It is a manufacturing method of the organic thin-film transistor which has a gate electrode, a gate insulating layer, an organic-semiconductor layer, a source electrode, and a drain electrode on a board | substrate, Comprising: Manufacturing the organic thin-film transistor as described in any one of Claims 1-10. A method for producing an organic thin film transistor.

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