JP2004146430A - Organic thin film transistor, organic thin film transistor device, and their manufacturing methods - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin film transistor with which organic thin film semiconductor devices can be formed continuously on a flexible base, such as the polymer supporting body etc., and, accordingly, can significantly reduce the manufacturing costs of the transistor devices and, in addition, which is excellent in performance, and to provide an organic thin film transistor device and methods of manufacturing the transistor and device. <P>SOLUTION: The organic thin film transistor has a gate electrode, a gate insulating layer, and an organic semiconductor layer adjoining the insulating layer. The transistor also has a source electrode and a drain electrode both of which are brought into contact with the semiconductor layer. The source and the drain electrodes are respectively constituted of two layers containing different conductive materials. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic thin film transistor, an organic TFT device, and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, various organic thin film transistors using an organic semiconductor have been proposed. 2. Description of the Related Art Organic thin film transistors (TFTs) are expected to be used as key devices for display circuits for plastic circuits, especially portable computers and mobile phones, and memories such as cash cards. As an organic thin film transistor, an all-polymer type organic TFT technology has been disclosed (for example, see Patent Document 1). Although a simple process using ink jet or coating has been proposed, there are problems such as a high gate voltage, a low current value in the switching ON state, and a low ON / OFF value of the current.
[0003]
In addition, conventional organic thin film transistors need to keep the contact resistance between the source electrode, the drain electrode and the organic semiconductor layer low, and may be made of gold, platinum, or a heavily doped conductive polymer, such as polyethylene dioxythiophene and polystyrene. It is common to use a sulfonic acid complex (see, for example, Patent Document 2). However, when these electrodes are used, the adhesion to the support and the mechanical strength are low, and there is a problem in durability as an element. Therefore, it has been difficult to realize an organic TFT device that operates stably on a flexible substrate. Further, when a conductive polymer is used, although the contact resistance can be kept low, the resistivity of the conductive polymer itself is high and there is a problem in practical use.
[0004]
[Patent Document 1]
International Publication No. 01/47043 pamphlet
[0005]
[Patent Document 2]
JP 2000-307172 A
[0006]
[Problems to be solved by the invention]
The above problems are greatly improved, and an organic TFT device can be continuously formed on a flexible base such as a polymer support. Therefore, the production cost can be greatly reduced, and an organic thin film transistor having excellent performance can be obtained. An object of the present invention is to provide a TFT device and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following means.
[0008]
(1) In an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer adjacent to the gate insulating layer, and a source electrode and a drain electrode in contact with the organic semiconductor layer, the source electrode and the drain electrode are: An organic thin-film transistor comprising two layers each containing a different conductive material.
[0009]
(2) The organic thin-film transistor according to (1), wherein the different conductive materials are materials having different work functions and at least one layer containing a material having a higher work function is joined to the organic semiconductor layer. .
[0010]
(3) The organic semiconductor device according to (1) or (2), wherein the organic semiconductor layer is electrically connected to at least one of the source electrode and the drain electrode and is in contact with a gate insulating layer. Thin film transistor.
[0011]
(4) The organic thin film transistor according to (3), wherein the at least one layer has a smaller contact resistance with the organic semiconductor layer than the other layer.
[0012]
(5) The organic thin film transistor according to (3) or (4), wherein the at least one layer is provided on a gate electrode side.
[0013]
(6) The organic thin-film transistors according to any one of (1) to (5) are arranged in a matrix including signal lines and scanning lines, and a part of the signal lines is used as a source electrode. Organic TFT device.
[0014]
(7) The organic TFT device according to (6), wherein a part of the scanning line is used as a gate electrode.
[0015]
(8) The organic TFT device according to (6) or (7), further comprising a display electrode, wherein a part of the display electrode is a drain electrode.
[0016]
(9) The organic TFT device according to any one of (6) to (8), which is formed on a polymer support.
[0017]
(10) The organic thin-film transistor according to any one of (1) to (5), including a step of forming a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on the support. A method of sequentially or simultaneously applying two layers of a source electrode layer and a photoresist layer each containing different metal fine particles to be a source of a source electrode and a drain electrode, and a photolithographic method. A method for manufacturing an organic thin film transistor, comprising a step of forming a source electrode and a drain electrode by etching a layer.
[0018]
(11) The method for producing an organic thin film transistor according to (10), further comprising a step of fusing the source electrode and the drain electrode by heat treatment.
[0019]
(12) The organic method according to (6), including the step of forming, on the support, a gate electrode also serving as a scanning line, a gate insulating layer, an organic semiconductor layer, a source electrode also serving as a signal line, and a drain electrode also serving as a display electrode. A method for manufacturing a TFT device, comprising sequentially or simultaneously applying two original electrode layers and a photoresist layer each containing different metal fine particles to be a source of a source electrode and a drain electrode, wherein the two layers are formed by a photolithographic method. Forming a source electrode and a drain electrode by etching the original electrode layer.
[0020]
(13) The method of manufacturing an organic TFT device according to (12), further comprising a step of fusing the source electrode and the drain electrode by heat treatment.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an organic thin film transistor, an organic TFT device, and a method of manufacturing the same according to the present invention will be described with reference to the drawings.
[0022]
1A, 1B, and 1C show examples of the configuration of the organic thin film transistor of the present invention. A gate electrode G, a gate insulating layer In, an organic semiconductor layer C adjacent to the gate insulating layer In, and a source electrode S and a drain electrode D in contact with the organic semiconductor layer C are provided over the support. . The organic thin-film transistor of the present invention is characterized in that the source electrode S and the drain electrode D are formed of two layers each containing a different conductive material. That is, the source electrode S is S₁And S₂Therefore, the drain electrode D is D₁And D₂, Respectively. In the present invention, the different conductive materials are preferably materials having different work functions. Further, it is preferable that the layer on the side in contact with the organic semiconductor layer C has a small contact resistance. As shown in FIG. 1, S of the source electrode S₁Is the D of the drain electrode D₁Are in contact with the organic semiconductor layer C, respectively, and S₁Is S₂Than D₁Is D₂The contact resistance is smaller.
[0023]
Hereinafter, each of the organic semiconductor, the source electrode and the drain electrode, the gate electrode, and the gate insulating layer will be described, but the present invention is not limited thereto.
[0024]
<Organic semiconductor>
A π-conjugated material is used. For example, polypyrroles such as polypyrrole, poly (N-substituted pyrrole), poly (3-substituted pyrrole), poly (3,4-disubstituted pyrrole), polythiophene, poly (3-substituted thiophene), poly (3,4- Poly (diphenylthiophene), polythiophenes such as polybenzothiophene, polyisothianaphthenes such as polyisothianaphthene, polyphenylenevinylenes such as polyphenylenevinylene, poly (p-phenylenevinylene) such as poly (p-phenylenevinylene) (Phenylenevinylenes), polyaniline, poly (N-substituted aniline), poly (3-substituted aniline), polyaniline such as poly (2,3-substituted aniline), polyacetylene such as polyacetylene, polydiacetylene such as polydiacetylene , Polyazulene such as polyazulene, polypyrene etc. Polypyrenes, polycarbazoles, polycarbazoles such as poly (N-substituted carbazole), polyselenophenes such as polyselenophene, polyfurans such as polyfuran and polybenzofuran, and poly (p-) such as poly (p-phenylene) Phenylenes), polyindoles such as polyindole, polypyridazines such as polypyridazine, naphthacene, pentacene, hexacene, heptacene, dibenzopentacene, tetrabenzopentacene, pyrene, dibenzopyrene, chrysene, perylene, coronene, terylene, ovalene, Polyacenes such as quaterylene and circum anthracene, and derivatives in which some of the carbons of the polyacenes are substituted with a functional group such as an atom such as N, S or O, or a carbonyl group (triphenodioxazine, triphenodithiazine Hexacene-6,15-quinone, etc.), polyvinylcarbazole, polyphenylene sulfide, vinyl sulfide, etc. of the polymer and is described in JP-A-11-195790 a polycyclic condensation or the like can be used. Further, for example, thiophene hexamer α-sexithiophene, α, ω-dihexyl-α-sexithiophene, α, ω-dihexyl-α-quinkethiophene, α, ω-bis having the same repeating unit as these polymers Oligomers such as (3-butoxypropyl) -α-sexithiophene and styrylbenzene derivatives can also 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 diimide, N, N'-bis (4-trifluoromethylbenzyl) ) N, N'-bis (1H, 1H-perfluorooctyl), N, N'-bis (1H, 1H-perfluorobutyl) and N, N 'together with naphthalene 1,4,5,8-tetracarboxylic diimide Naphthalenetetracarboxylic diimides such as dioctylnaphthalene-1,4,5,8-tetracarboxylic diimide derivative, naphthalene-2,3,6,7-tetracarboxylic diimide and anthracene-2,3,6 Condensed rings such as anthracenetetracarboxylic diimides such as 7-tetracarboxylic diimide Tetracarboxylic acid diimides, C60, C70, C76, C78, C84 etc. fullerenes, carbon nanotubes such as SWNT, merocyanine dyes, etc. dyes such hemicyanine dyes and the like.
[0025]
Among these π-conjugated materials, thiophene, vinylene, chenylene vinylene, phenylene vinylene, p-phenylene, a substituted product thereof, or two or more of these are used as a repeating unit, and the number n of the repeating unit is 4 to 4. At least one selected from the group consisting of oligomers having 10 or a polymer in which the number n of the repeating units is 20 or more, condensed polycyclic aromatic compounds such as pentacene, fullerenes, condensed ring tetracarboxylic diimides, and metal phthalocyanines Species are preferred.
[0026]
Other organic semiconductor materials include tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTF-iodine complex, and TCNQ-iodine complex. , Etc. can also be used. Further, σ-conjugated polymers such as polysilane and polygermane, and organic / inorganic hybrid materials described in JP-A-2000-260999 can also be used.
[0027]
In the present invention, for example, a material having a functional group such as acrylic acid, acetamido, dimethylamino group, cyano group, carboxyl group, or nitro group in the organic semiconductor layer, a benzoquinone derivative, tetracyanoethylene, and tetracyanoquinodimethane And materials that have an electron acceptor such as derivatives thereof and materials having functional groups such as amino group, triphenyl group, alkyl group, hydroxyl group, alkoxy group and phenyl group, and substituted amines such as phenylenediamine , Anthracene, benzoanthracene, substituted benzoanthracenes, pyrene, substituted pyrene, carbazole and its derivatives, tetrathiafulvalene and its derivatives, etc. Process Good.
[0028]
The doping means that an electron donating molecule (acsector) or an electron donating molecule (donor) is introduced as a dopant into the thin film. Therefore, the doped thin film is a thin film containing the condensed polycyclic aromatic compound and the dopant. Either an acceptor or a donor can be used as the dopant used in the present invention. Cl as the acceptor₂, Br₂, I₂, ICl, ICl₃, IBr, IF and other halogens, PF₅, AsF₅, SbF₅, BF₃, BC1₃, BBr₃, SO₃Lewis acids such as HF, HC1, HNO₃, H₂SO₄, HClO₄, FSO₃H, ClSO₃H, CF₃SO₃H or other protonic acids, acetic acid, formic acid, organic acids such as amino acids, FeCl₃, FeOCl, TiCl₄, ZrCl₄, HfCl₄, NbF₅, NbCl₅, TaCl₅, MoCl₅, WF₅, WCl₆, UF₆, LnCl₃(Ln = La, Ce, Nd, Pr, etc. lanthanoid and Y) and transition metal compound such as Cl⁻, Br⁻, I⁻, ClO₄ ⁻, PF₆ ⁻, AsF₅ ⁻, SbF₆ ⁻, BF₄ ⁻And electrolyte anions such as sulfonic acid anions. Examples of the donor include alkali metals such as Li, Na, K, Rb, and Cs; alkaline earth metals such as Ca, Sr, and Ba; Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy. , Ho, Er, Yb and other rare earth metals, ammonium ions, R₄P⁺, R₄As⁺, R₃S⁺(Each R represents an alkyl group, an aryl group, etc.), acetylcholine and the like. As a method of doping these dopants, any of a method of preparing a thin film of an organic semiconductor in advance and introducing the dopant later, and a method of introducing a dopant at the time of forming the thin film of the organic semiconductor can be used. As the doping of the former method, gas-phase doping using a dopant in a gas state, liquid-phase doping in which a solution or liquid dopant is brought into contact with the thin film, and diffusion doping by bringing a solid-state dopant into contact with the thin film Solid doping method. In liquid phase doping, the efficiency of doping can be adjusted by performing electrolysis. In the latter method, a mixed solution or dispersion of an organic semiconductor compound and a dopant may be simultaneously applied and dried. For example, when a vacuum evaporation method is used, the dopant can be introduced by co-evaporating the dopant together with the organic semiconductor compound. When a thin film is formed by a sputtering method, a dopant can be introduced into the thin film by sputtering using a binary target of an organic semiconductor compound and a dopant. Still other methods include chemical doping such as electrochemical doping and photo-initiated doping and physical doping such as ion implantation described in a publication (Industrial Materials, Vol. 34, No. 4, p. 55, 1986). Any of the conventional dopings can be used.
[0029]
These organic thin films can be formed by vacuum deposition, molecular beam epitaxy, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, plasma polymerization, electrolytic polymerization, chemical polymerization, etc. Examples include a synthesizing method, a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, a roll coating method, a bar coating method, a die coating method, and an LB method, which can be used depending on the material. However, in terms of productivity, spin coating, blade coating, dip coating, roll coating, bar coating, die coating, etc., which can easily and accurately form a thin film using an organic semiconductor solution, are used. Preferred. Alternatively, the organic semiconductor layer may be formed by discharging a solution or dispersion of the organic semiconductor by inkjet, and drying and removing the solvent.
[0030]
The thickness of the organic semiconductor thin film is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the thickness of the active layer made of the organic semiconductor. Although it differs depending on the semiconductor, it is generally preferably 1 μm or less, particularly preferably 10 to 300 nm.
[0031]
<Source electrode, drain electrode>
In the present invention, the metal material is platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, zinc. A known conductive polymer or the like can be used. In particular, the electrode D at least partially in contact with the organic semiconductor layer₁Is preferably platinum, gold, silver, copper, cobalt, chromium, iridium, nickel, palladium, molybdenum, tungsten, or a heavily doped conductive polymer having a work function of 4.5 eV or more. Also, D₂Is preferably a metal such as copper or aluminum having a resistivity of 20 μΩ · cm or less.
[0032]
S₁, D₁That is, the thickness of the layer in contact with the organic semiconductor layer is about 10 to 50 nm. Also, S₂, D₂That is, the thickness of the layer on the side opposite to the organic semiconductor layer is approximately 100 to 300 nm.
[0033]
As the source electrode S and the drain electrode D, an electrode formed by using a dispersion containing metal fine particles having a particle diameter of 1 to 50 nm, more preferably 1 to 10 nm, and heat-fusing the metal fine particles by heating. It is preferable to use
[0034]
Fine particles composed of these metals are patterned by using a dispersion stabilizer mainly composed of an organic material, applying a liquid, paste or ink dispersed in water or a dispersion medium that is any organic solvent.
[0035]
As a method for producing such a metal fine particle dispersion, a metal ion is reduced in a liquid phase, such as a physical generation method such as a gas evaporation method, a sputtering method, a metal vapor synthesis method, a colloid method, and a coprecipitation method. A chemical production method for producing metal fine particles may be mentioned, and preferably, a colloid method described in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, JP-A-2000-239853, etc. It is a metal fine particle dispersion produced by the in-gas evaporation method described in JP 2001-254185, JP 2001-53028, JP 2001-35255, JP 2000-124157, JP 2000-123634 and the like. These metal fine particle dispersions are formed into a layer by the method described below, then the solvent is dried, and further heat-treated at 100 to 300 ° C., preferably 150 to 200 ° C., to thereby thermally fuse the metal fine particles. Then, an electrode is formed.
[0036]
In the present invention, when the metal fine particle dispersion is heated and the metal fine particles are thermally fused, it is preferable that the organic semiconductor layer to be bonded to those electrodes is already formed. That is, by heating the organic semiconductor material and the metal fine particles at the same time, the physical junction between the two is strengthened, the contact resistance is further reduced, and the current when the transistor is switched can be increased. The order of formation of the metal fine particle dispersion layer and formation of the organic semiconductor layer is not particularly limited.
[0037]
Various methods such as a method of patterning before the heat treatment using the metal fine particle dispersion, or a method of forming a metal fine particle dispersion layer and then heat-fusing the metal fine particles by heating to an electrode shape may be used. I can do it.
[0038]
First, there is a method of forming a pattern of the metal fine particle dispersion by a printing method. The metal fine particle dispersion is patterned using ink as an ink, and as a printing method, the metal fine particle dispersion can be patterned by any printing method such as letterpress printing, screen printing, lithographic printing, intaglio printing, stencil printing and the like. .
[0039]
In addition, there is a method of patterning a metal fine particle dispersion by an inkjet method.
[0040]
This is a method of discharging a metal fine particle dispersion from an ink jet head and patterning the metal fine particle dispersion. The discharge method from the ink jet head is an on-demand type such as a piezo method or a bubble jet (R) method, or electrostatic suction. Patterning can be performed by a known method such as a continuous jet type ink jet method such as a method. Thereafter, the obtained metal fine particle dispersion pattern is subjected to a heat treatment, whereby the metal fine particles are thermally fused to form a patterned source electrode or drain electrode.
[0041]
Hereinafter, a method of patterning the metal fine particle dispersion layer using a resist image will be described. According to the lift-off method, a resist image is formed on a support, two layers of the fine metal particle dispersion are applied thereon, and then the resist image is removed, thereby simultaneously removing the fine metal particle dispersion in the resist image portion. As a result, two patterned fine metal particle dispersion layers remain.
[0042]
According to the squeegee method, a resist image 13 is formed on a support, and a metal fine particle dispersion 4 is applied thereon. Then, an excess metal fine particle dispersion in the resist image portion is removed by a squeezer (such as a blade or a squeegee roll). After removal, a patterned metal fine particle dispersion layer is formed on the exposed portion of the substrate, and after drying, the resist image is removed, so that two patterned metal fine particle layers remain.
[0043]
Thereafter, by performing a heat treatment, the metal fine particles in the two metal fine particle layers are thermally fused to form a patterned electrode. Before removing the resist image, heat treatment may be performed to thermally fuse the metal fine particles.
[0044]
A method in which the metal fine particle dispersion layer is patterned by a photolithographic method may be used. After forming two metal fine particle dispersion layers on the support, a photoresist layer is applied, and pattern exposure and development are performed to form a resist image, and the metal fine particle dispersion layer where the photoresist layer is removed is formed. Is removed with a solvent or the like to obtain a patterned two-layered metal fine particle dispersion layer, the resist image is removed with a removing solution, and heated to form a source electrode and a drain electrode. Before removing the resist image, the metal fine particles may be thermally fused by heating.
[0045]
As the photoresist layer, known positive and negative materials can be used, but it is preferable to use a material that is sensitive to laser light. Examples of such a photoresist material include: (1) a dye-sensitized photopolymerizable photosensitive material as disclosed in JP-A-11-271969, JP-A-2001-117219, JP-A-11-311859 and JP-A-11-352691; (2) Negative-type photosensitive photosensitive to infrared laser as disclosed in JP-A-9-179292, U.S. Pat. No. 5,340,699, JP-A-10-90885, JP-A-2000-321780 and JP-A-2001-154374. Materials, (3) JP-A-9-171254, JP-A-5-115144, JP-A-10-87733, JP-A-9-43847, JP-A-10-268512, JP-A-11-194504, JP-A-11-223936, JP-A-11 -84657, 11-174681, 7-285275, JP-A-2000-56452, WO97 / 39894, Positive photosensitive material having photosensitivity to infrared lasers such as 98/42507 and the like. Since the process is not limited to a dark place, (2) and (3) are preferable, and when the photoresist layer is removed, the positive type (3) is most preferable.
[0046]
In order to remove the resist image, an appropriate solvent is selected from a wide range of organic solvents used as a photoresist coating solvent such as an alcohol, an ether, an ester, a ketone, and a glycol ether.
[0047]
By patterning using the metal fine particle dispersion of the present invention and performing heat fusion, a source electrode or a drain electrode can be easily manufactured with high precision, and patterning can be easily performed in various forms. A thin film transistor can be easily manufactured.
[0048]
For details, reference can be made to Japanese Patent Application No. 2002-134056 filed on May 9, 2002 by the present inventors.
[0049]
Further, an electrode D at least partially in contact with the organic semiconductor layer₁Is preferably a heavily doped conductive polymer having a work function of 4.5 eV or more. As a specific example, a material doped with the above organic semiconductor material is used. Particularly preferably, a complex of poly (ethylenedioxythiophene) and polystyrenesulfonic acid (for example, Baytron @ P manufactured by Bayer AG) is preferably used. Can be. D₁Can be based on the above-described metal fine particle dispersion.
[0050]
<Gate electrode>
The gate electrode is not particularly limited as long as it is a conductive material, and any material can be used. As a method of forming a gate electrode, a method of forming a conductive thin film using a known photolithographic method or a lift-off method on a conductive thin film formed using a method such as vapor deposition or sputtering, or thermal transfer onto a metal foil such as aluminum or copper And a method of etching using a resist by an ink jet or the like. Further, a solution or dispersion of a conductive polymer or a dispersion of conductive fine particles may be directly patterned by ink jet, or may be formed from a coating film by lithography or laser ablation. Further, 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 letterpress, intaglio, lithographic, or screen printing can also be used. Alternatively, the above-described method for forming the source electrode and the drain electrode may be used.
[0051]
<Gate insulating layer>
Although various insulating materials can be used, an inorganic oxide film having a high relative dielectric constant is particularly preferable. As the inorganic oxide, 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 include barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate bismuth, and yttrium trioxide. Among them, preferred are silicon oxide, aluminum oxide, tantalum oxide and titanium oxide. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.
[0052]
Examples of the method for forming the inorganic oxide film include dry processes such as a vacuum deposition method, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method, an ion plating method, a CVD method, a sputtering method, and an atmospheric pressure plasma method. Wet processes such as spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, and other coating methods, and printing and inkjet patterning methods. , Can be used depending on the material. The wet process is a method in which fine particles of an inorganic oxide are dispersed in an optional organic solvent or water using a dispersing aid such as a surfactant, if necessary, and a method of drying, or a method of drying an oxide precursor, for example, A so-called sol-gel method of applying and drying a solution of the alkoxide compound is used. Of these, the atmospheric pressure plasma method and the sol-gel method are preferred.
[0053]
Plasma deposition under atmospheric pressure refers to a process of discharging under atmospheric pressure or a pressure close to atmospheric pressure, exciting a reactive gas into plasma, and forming a thin film on a base material. These are described in Kaihei 11-133205, JP-A-2000-185362, JP-A-11-61406, JP-A-2000-147209, and 2000-121804 (hereinafter also referred to as atmospheric pressure plasma method). Thereby, a highly functional thin film can be formed with high productivity.
[0054]
As the organic compound film, polyimide, polyamide, polyester, polyacrylate, photo-radical polymerization type, photo-cationic polymerization type photo-curable resin, or copolymer containing acrylonitrile component, polyvinyl phenol, polyvinyl alcohol, novolak resin, And phosphazene compounds including cyanoethyl pullulan, polymers and elastomers, and the like.
[0055]
As the method for forming the organic compound film, the wet process is preferable. The inorganic oxide film and the 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.
[0056]
<Support>
The support is made of glass or a flexible polymer sheet. In the present invention, it is preferable to use a polymer as a support, because it is possible to reduce the weight, to improve portability, and to improve impact resistance, as compared with the case of using a glass substrate. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), Examples of the film include cellulose acetate propionate (CAP).
[0057]
The method for manufacturing an organic thin film transistor according to the present invention basically includes the following steps S1 to S7.
[0058]
S1 ... Step of forming scanning line and gate electrode on support
S2: Step of forming gate insulating layer covering gate electrode
S3: Step of forming organic semiconductor layer on gate insulating layer
S4: Step of forming original electrode layer on organic semiconductor layer that can be removed with a photoresist developer
S5: Step of forming a photoresist layer on original electrode layer
S6: Step of exposing photoresist layer
S7: Step of removing a part of the original electrode layer by developing the exposed photoresist layer to form a source electrode, a drain electrode, a signal line, and a display electrode. The manufacturing process of the organic thin film transistor shown in FIG. 1C will be described below with reference to FIG. 2 to 8, (a) is a schematic cross-sectional view, and (b) is a schematic plan view.
[0059]
S1 ... Step of forming scanning line and gate electrode on support
As shown in FIG. 2, a gate electrode G is formed on a support. As a method for forming an electrode, for example, a conductive thin film (aluminum, silver, copper, ITO, or the like) formed on a 150-μm polyimide film by a method such as vapor deposition, sputtering, or a CVD method is known by a known photolithography method or lift-off method. There is a method of forming an electrode using a method, and a method of forming a resist on a metal foil such as aluminum or copper by thermal transfer, inkjet, or the like and etching the resist. A conductive polymer solution or dispersion, a conductive fine particle dispersion, or the like may be directly patterned by an inkjet method, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning an ink, a conductive paste, or the like containing a conductive polymer or conductive fine particles by a printing method such as letterpress, intaglio, lithographic, or screen printing can also be used.
[0060]
S2: Step of forming gate insulating layer In covering gate electrode G
As shown in FIG. 3, a gate insulating layer In is formed on the entire surface of the support on which the gate electrode G is formed. For example, an inorganic oxide or an inorganic nitride can be formed by a dry process such as evaporation, sputtering, a CVD method, or an atmospheric pressure plasma method, preferably by an atmospheric pressure glow discharge plasma treatment. Alternatively, an organic insulating material such as polyvinyl alcohol, a phenol resin, an epoxy resin, or an acrylic resin can be applied.
[0061]
S3: Step of forming organic semiconductor layer on gate insulating layer
As shown in FIG. 4, an organic semiconductor layer C covering the entire surface of the gate insulating layer In is formed. Any organic semiconductor can be formed by a known method. Preferably, a well-purified chloroform solution of a poly- (3-hexylthiophene) in the form of a ligand is applied, for example, so as to have a dry film thickness of 20 nm.
[0062]
S4: Step of forming original electrode layer on organic semiconductor layer
As shown in FIG. 5, multi-layer coating was performed using an aqueous dispersion of metal fine particles, and preliminarily dried at 100 ° C. for 3 minutes.₁, O₂) Is formed on the organic semiconductor layer C. Original electrode layer O (O₁, O₂As a method for forming (2), a coating method such as spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, and die coating is used. Specifically, two layers are simultaneously coated using an aqueous dispersion of the fine metal particles or the conductive polymer described in the section of the source electrode and the drain electrode, and preliminarily dried at about 100 ° C. for 3 minutes to form the source electrode and the drain electrode. It is possible to form two layers of original electrode layers each containing different metal fine particles as the origin of the above.
[0063]
S5: Step of forming a photoresist layer on original electrode layer
As shown in FIG. 6, the original electrode layer O (O₁, O₂A solution of a photosensitive resin (generally referred to as a photoresist, hereinafter referred to as a photoresist) is applied to the entire upper surface to form a photoresist layer R. As the photoresist layer, known positive-type and negative-type materials can be used, but it is preferable to use a laser-sensitive material. In order to enable a process in a bright room, a photosensitive material having an output of 50 mW or more and being sensitive to an infrared laser having a wavelength of 700 nm or more is preferably used. Further, when the resist of the photosensitive layer is finally removed, a positive photosensitive material is preferably used.
[0064]
S6: Step of exposing photoresist layer
As shown in FIG. 7, the photoresist layer R is subjected to patterning exposure. Exposure is preferably performed in-line. As a light source for the exposure, an Ar laser, a semiconductor laser, a He-Ne laser, a YAG laser, a carbon dioxide laser, and the like can be given, and a semiconductor laser having an oscillation wavelength in the infrared is preferable. The output is suitably 50 mW or more, preferably 100 mW or more.
[0065]
S7: Step of forming source and drain electrodes by development
As shown in FIG. 8, the photoresist layer R is exposed and then alkali-developed, and the photoresist layer R and the original electrode layer O (O₁, O₂) At the same time, the source electrode S (S₁, S₂) And the drain electrode D (D₁, D₂) Is formed. Original electrode layer O (O₁, O₂) Can be removed because they are redispersed in water. When an organic solvent dispersion is used for the metal fine particles, a redispersible etching solution may be used. Original electrode layer O (O₁, O₂In the case of comprising metal fine particles, the photoresist layer R is dried after exposure and development, and further heat-treated at 100 to 300 ° C., preferably 150 to 200 ° C. to fuse the metal fine particles. , A source electrode, a drain electrode, a signal line, and a display electrode can be formed at one time. As an example here, preferably, a layer of the source electrode and the drain electrode in contact with the organic semiconductor layer is 30 nm of gold or a complex of poly (ethylenedioxythiophene) and polystyrenesulfonic acid (for example, Baytron manufactured by Bayer AG). P) and the other side was 200 nm copper.
[0066]
If necessary, a step S8 for removing the photoresist layer R shown in FIG. 9 can be added. When performing the step of removing the photoresist layer R, the step of fusing the metal fine particles by heating is performed after the removing step S8.
[0067]
By appropriately selecting the materials for the gate insulating layer, the organic semiconductor layer, the original electrode layer, and the photoresist layer, and the solvent, the steps S2 to S5 can be performed simultaneously, that is, by simultaneous multi-layer coating. . Alternatively, a thin film of silicon oxide, silicon nitride, or titanium oxide may be formed by an atmospheric pressure plasma method to seal the organic thin film transistor.
[0068]
The organic thin film transistor shown in FIGS. 1A and 1B can be easily manufactured by applying the above method.
[0069]
FIG. 10 shows three pattern examples (per pixel) of the traffic light and the display electrode formed as described above.
[0070]
The characteristics of the manufactured organic thin film transistor can be evaluated by a circuit configuration as shown in FIG.
[0071]
FIG. 12 is a diagram showing a display device using the organic TFT device of the present invention. Each of the cells arranged in a matrix has an organic thin film transistor 10, a display electrode 11, a storage capacitor 12, and a display element 17. The signal line 13 is connected to the source electrode of the organic thin film transistor 10, the scanning line 14 is connected to the gate electrode of the organic thin film transistor 10, and the display electrode 11 is connected to the drain electrode of the organic thin film transistor 10. Reference numeral 15 denotes a vertical drive circuit, 16 denotes a horizontal drive circuit, and 17 denotes a display element such as a liquid crystal or an electrophoretic element. Note that the display element 17 is shown by an equivalent circuit.
[0072]
The scanning lines 14 are sequentially turned on by the horizontal driving circuit 16 and data signals are supplied from the vertical driving circuit 15 to inject electric charges into the storage capacitor 12 through the organic thin film transistor 10 to generate a driving voltage on the display electrode 11. Then, the display element 17 is driven. The charge stored in the storage capacitor 12 is held by the switching function of the organic thin film transistor 10 until the next frame is selected.
[0073]
Next, the manufacture of the organic TFT device will be described. The organic TFT device according to the embodiment of the present invention is suitable for manufacturing by a roll-to-roll (ROLL-to-ROLL) process, and enables low-cost mass production.
[0074]
【The invention's effect】
Provided are an organic thin-film transistor, an organic TFT device, and a method for manufacturing the same, which can continuously form an organic TFT device on a flexible base such as a polymer support, thereby greatly reducing the manufacturing cost and having excellent performance. I was able to.
[Brief description of the drawings]
FIG. 1 is a configuration example of an organic thin film transistor of the present invention.
FIG. 2 is a diagram illustrating a manufacturing process of an organic thin film transistor according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a manufacturing process of an organic thin film transistor according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating a manufacturing process of an organic thin film transistor according to an embodiment of the present invention.
FIG. 5 is a diagram showing a manufacturing process of the organic thin film transistor according to one embodiment of the present invention.
FIG. 6 is a diagram showing a manufacturing process of the organic thin film transistor according to one embodiment of the present invention.
FIG. 7 is a view illustrating a process of manufacturing an organic thin film transistor according to an embodiment of the present invention.
FIG. 8 is a diagram showing a manufacturing process of the organic thin film transistor according to one embodiment of the present invention.
FIG. 9 is a diagram showing a manufacturing process of the organic thin film transistor according to one embodiment of the present invention.
FIG. 10 is a diagram showing a pattern example of a display electrode and a signal line of an organic thin film transistor according to an embodiment of the present invention.
FIG. 11 is a circuit configuration diagram for evaluating characteristics of an organic thin film transistor.
FIG. 12 is a diagram showing a display device using an organic TFT device according to one embodiment of the present invention.
[Explanation of symbols]
G gate electrode
In gate insulating layer
C Organic semiconductor layer
S source electrode
D Drain electrode
R @ photoresist layer
11 display electrode
13 signal line
14 scanning line

Claims (13)

A gate electrode, a gate insulating layer, an organic semiconductor layer adjacent to the gate insulating layer, and an organic thin film transistor having a source electrode and a drain electrode in contact with the organic semiconductor layer;
An organic thin film transistor, wherein the source electrode and the drain electrode are formed of two layers each containing a different conductive material. 2. The organic thin film transistor according to claim 1, wherein the different conductive materials are materials having different work functions, and at least one layer containing a material having a higher work function is joined to the organic semiconductor layer. 3. The organic thin film transistor according to claim 1, wherein the organic semiconductor layer is electrically connected to at least one of the source electrode and the drain electrode, and is in contact with a gate insulating layer. 4. The organic thin film transistor according to claim 3, wherein the at least one layer has a smaller contact resistance with the organic semiconductor layer than the other layer. The organic thin film transistor according to claim 3, wherein the at least one layer is provided on a gate electrode side. 6. An organic TFT device, wherein the organic thin film transistors according to claim 1 are arranged in a matrix composed of signal lines and scanning lines, and a part of the signal lines is used as a source electrode. 7. The organic TFT device according to claim 6, wherein a part of the scanning line is a gate electrode. 8. The organic TFT device according to claim 6, further comprising a display electrode, wherein a part of the display electrode is a drain electrode. 9. The organic TFT device according to claim 6, wherein the organic TFT device is formed on a polymer support. The method for manufacturing an organic thin film transistor according to claim 1, further comprising a step of forming a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on a support,
A step of sequentially or simultaneously applying two layers of a source electrode layer and a photoresist layer each containing different metal fine particles that are the source of the source electrode and the drain electrode, and etching the two source electrode layers by a photolithographic method to form a source. A method for manufacturing an organic thin film transistor, comprising a step of forming an electrode and a drain electrode. The method according to claim 10, further comprising a step of fusing the source electrode and the drain electrode by heat treatment. 7. The organic TFT device according to claim 6, further comprising a step of forming a gate electrode also serving as a scanning line, a gate insulating layer, an organic semiconductor layer, a source electrode also serving as a signal line, and a drain electrode also serving as a display electrode on the support. A manufacturing method,
A step of sequentially or simultaneously applying two layers of a source electrode layer and a photoresist layer each containing different metal fine particles that are the source of the source electrode and the drain electrode, and etching the two source electrode layers by a photolithographic method to form a source. A method for manufacturing an organic TFT device, comprising a step of forming an electrode and a drain electrode. 13. The method according to claim 12, further comprising a step of fusing the source electrode and the drain electrode by heat treatment.

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