JP2011171484A - Thin film transistor, and electronic apparatus and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film transistor capable of stabilizing performance thereof. <P>SOLUTION: An organic TFT (Thin Film Transistor) includes a gate electrode 1, an active layer 3 disposed opposite the gate electrode 1 across the gate insulating layer 2, and a source electrode 4 and a drain electrode 5, spaced apart from each other and connected to the active layer 3. The active layer 3 includes a soluble organic semiconductor material and a soluble polymer material, and a glass transition temperature of the soluble polymer material is higher than a maximum temperature of a packaging process. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thin film transistor including an active layer containing an organic semiconductor material, an electronic device using the same, and a method for manufacturing the same.

  In recent years, field effect transistors (FETs) have been used in various technical fields, and among these, thin film transistors (TFTs) have become widespread. This TFT is mounted on many electronic devices, and is used as a pixel selection device in, for example, an active matrix display.

  A TFT has a source electrode and a drain electrode connected to an active layer (so-called channel layer) spaced from a gate electrode through a gate insulating layer. In this TFT, the current flowing between the source electrode and the drain electrode is controlled according to the voltage applied to the gate electrode, and the current flows while accumulating or consuming charge carriers in the active layer.

  As a material for forming the active layer, an inorganic semiconductor material such as silicon (Si) or gallium arsenide (GaAs) is used, and a TFT having such an active layer is called an inorganic TFT. However, in large applications such as large screen displays, inorganic semiconductor materials are expensive, and severe manufacturing conditions (such as high temperature or vacuum) are required to make the performance of multiple inorganic TFTs uniform across the entire screen. Manufacturing difficulty and cost increase.

  Therefore, recently, it has been studied to use an inexpensive organic semiconductor material instead of an inorganic semiconductor material, and a TFT having such an active layer is called an organic TFT. As this organic semiconductor material, a conjugated material having π electrons is mainly used (for example, see Non-Patent Documents 1 to 4). However, there is a concern that the above conjugated materials cannot obtain sufficient electrical performance and are difficult to process in a large-scale manufacturing process. In addition, it has been regarded as a problem that sufficient fastness cannot be obtained because it easily reacts with oxygen and moisture in the atmosphere. Such a problem relating to robustness may shorten the life of an electronic device equipped with an organic TFT. Therefore, it cannot be said that conventional organic semiconductor materials are still at a satisfactory level in actual use.

  Specifically, when pentacene is used, extremely high mobility can be obtained, but it is limited to the case where vapor deposition is performed under high vacuum conditions (see, for example, Non-Patent Document 5). For pentacene, the use of a soluble precursor to enable liquid processing has been studied, but in this case, in order to form an active layer, a high temperature (140 ° C. to 180 ° C.) is used in a vacuum. ) (See Non-Patent Document 6, for example). This manufacturing process by liquid processing is limited in terms of usefulness in practical use because the performance of the organic TFT finally manufactured is very susceptible to the substrate and conversion conditions. Absent.

  When a conjugated oligomer such as α-sexithiophene is used, high mobility can be obtained, but it is also limited to the case where vapor deposition is performed under high vacuum conditions (see, for example, Non-Patent Documents 7 and 8). In contrast, some semiconducting polymers such as poly (3-hexylthiophene) can be deposited from the solution phase, but have been found to be insufficient in practical use (eg, non-patented). Reference 9).

  A high mobility doped polymer in which bis (di-tolylaminophenyl) cyclohexane is doped in a thermoplastic polymer has been reported by Borsenberger et al. (For example, see Non-Patent Document 10). This high mobility doped polymer can be used as a transport layer in xerographic photoreceptors.

  In addition, in order to manufacture an electronic device, it is examined to use a mixture of organic materials (for example, refer to Patent Document 1). This mixture is a composition for conductive coating containing a polymer material (polymer binder), a charge transport molecule and an oxidizing agent, and the oxidizing agent is used to increase the carrier concentration.

  As a material for forming the active layer, a mixture of at least two types of organic semiconductor materials is used (see, for example, Patent Document 2). In this case, one organic semiconductor material has higher conductivity than the other organic semiconductor material, and the highly conductive organic semiconductor material serves to supply carriers in the active layer. Is well controlled. It should be noted that an electrical insulating material may be further mixed into the mixture of organic semiconductor materials.

An active layer containing a polymer material (organic binder) together with an organic semiconductor material is used (for example, see Patent Document 3). This polymeric material has an intrinsic conductivity of less than 10 ⁻⁶ Scm ⁻¹ and a dielectric constant ε of less than 3.3 at 1000 Hz. This dielectric constant ε is preferably less than 3.0, more preferably less than 2.8, and particularly 2.0 to 2.8.

Jay. Mate. Chem. 7 (3), pages 369-376, 1997 (J. Mater. Chem., 7 (3), p369-p376, 1997). Jay. Mate. Chem. , 9, 1895-1904, 1999 (J. Mater. Chem,, 9, p1895-p1904, 1999). Current Opinion in Solid State & Materials Science, 2, 455-561, 1997 (Current Opinion in Solid State & Materials Science, 2, p455-p561, 1997) Current Opinion in Solid State & Materials Science, 227, 253-262, 1998 (Current Opinion in Solid State & Materials Science, 227, p253-p262, 1998) Sins. metal. 1127, 41-43, 1991 (Synth. Metals, 1127, p41-p43, 1991). Sins. metal. 88, 37-55, 1997 (Synth. Metals, 88, p37-p55, 1997). Sins. metal. 435, 54, 1993 (Synth. Metals, 435, p54, 1993). Sins. metal. 265, 1684, 1994 (Synth. Metals, 265, p1684, 1994) Upride Physics Letters, 53, 195, 1988 (Applied Physics Letters, 53, p195, 1988) Jay. Apple. Fizz, 34, Pt2, No12A, pages L1597-L1598, 1995 (J. Appl. Phys., 34, Pt2, No12A, L1597-L1598, 1995)

European Patent No. 0910100A2 specification US Pat. No. 5,500,557 Special table 2004-525501 gazette

  In the manufacturing process of an electronic device, after an organic TFT is formed, the organic TFT is packaged with various packaging members typified by a protective (or planarizing) insulating layer. In this case, if the organic TFT is excessively heated in the packaging process, the characteristics of the active layer are likely to be deteriorated. Therefore, there is a high possibility that the performance of the organic TFT such as mobility and on / off ratio varies.

  The present invention has been made in view of such problems, and an object thereof is to provide a thin film transistor capable of stabilizing performance, an electronic device using the thin film transistor, and a method for manufacturing the same.

  The electronic device of the present invention includes a thin film transistor and a packaging member. The thin film transistor includes a gate electrode, an active layer disposed opposite to the gate electrode through a gate insulating layer and including a soluble organic semiconductor material and a soluble polymer material, a source electrode separated from each other and connected to the active layer, and And a drain electrode. The packaging member is packaged with the thin film transistor. The glass transition temperature of the soluble polymer material is higher than the maximum temperature in the process in which the thin film transistor is packaged with the packaging member.

  The electronic device manufacturing method of the present invention includes a step of forming the above-described thin film transistor and a step of packaging the thin film transistor with a packaging member. The glass transition temperature of the soluble polymer material is set higher than the maximum temperature in the process of packaging the thin film transistor with the packaging member.

  The thin film transistor of the present invention includes a gate electrode, an active layer disposed opposite to the gate electrode through a gate insulating layer, and a source electrode and a drain electrode which are spaced apart from each other and connected to the active layer. The active layer includes a soluble organic semiconductor material and a soluble polymer material, and the glass transition temperature of the soluble polymer material is 150 ° C. or higher.

  According to the thin film transistor of the present invention, the active layer contains the soluble organic semiconductor material and the soluble polymer material, and the glass transition temperature of the soluble polymer material is higher than 150 ° C. In this case, in the manufacturing process of an electronic device using a thin film transistor, even if the thin film transistor is put into a packaging process including a process involving heating (maximum temperature = 150 ° C.), the characteristics of the active layer are hardly deteriorated. Therefore, performance such as mobility and on / off ratio is unlikely to vary among a plurality of thin film transistors. Therefore, the performance can be stabilized and the performance of the electronic device can be improved.

  According to the electronic device or the manufacturing method thereof of the present invention, the active layer of the thin film transistor to be packaged with the packaging member includes the soluble organic semiconductor material and the soluble polymer material. Further, the glass transition temperature of the soluble polymer material is set higher than the maximum temperature during processing of the packaging member. Therefore, even when a thin film transistor is put into a packaging process including a process involving heating (maximum temperature = 150 ° C.), the characteristics of the active layer are not easily deteriorated, so that the performance hardly varies among a plurality of thin film transistors. Therefore, the performance of the electronic device can be improved.

It is sectional drawing showing the structure of the thin-film transistor in one Embodiment of this invention. It is sectional drawing showing the other structure of the thin-film transistor in one Embodiment of this invention. It is sectional drawing showing the modification regarding the structure of a thin-film transistor. It is sectional drawing showing the structure of the principal part of the liquid crystal display device which is an application example of a thin-film transistor. It is a figure showing the circuit structure of the liquid crystal display device shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The order of explanation is as follows.

1. Thin film transistor Application example of thin film transistor (electronic equipment)

<1. Thin film transistor>
[Overall structure of thin film transistor]
1 and 2 respectively show a cross-sectional configuration and a planar configuration of an organic TFT that is a thin film transistor according to an embodiment of the present invention. FIG. 1 shows a cross-section along the line I-I shown in FIG. ing.

  The organic TFT described here is a device that constitutes a part of an electronic device such as a liquid crystal display device, as will be described in detail later, and is packaged with a packaging member in the manufacturing process of the electronic device. It is. The packaging member is a plurality of members (components other than the organic TFT) constituting the electronic device, such as an insulating layer covering the organic TFT or an electrode connected to the organic TFT. Note that packaging means that an organic TFT is combined with a packaging member through various processes such as a film formation process, a connection process, or a bonding process in order to complete an electronic device. Hereinafter, the process in which the organic TFT is combined with the packaging member is referred to as a packaging process.

  In this organic TFT, an active layer 3 is disposed so as to face the gate electrode 1 through the gate insulating layer 2, and a source electrode 4 and a drain electrode 5 are connected to the active layer 3.

  The organic TFT shown in FIGS. 1 and 2 includes, for example, a bottom gate in which the gate electrode 1 is located below the active layer 3 and the source electrode 4 and the drain electrode 5 overlap the upper side of the active layer 3. -Top contact type.

  The gate electrode 1 is, for example, tungsten (W), tantalum (Ta), molybdenum (Mo), aluminum (Al), chromium (Cr), titanium (Ti), copper (Cu), nickel (Ni), or an alloy thereof. It is formed with metal materials.

The gate insulating layer 2 is made of, for example, an inorganic material or an organic polymer material. Examples of the inorganic material include silicon oxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ). The organic polymer material is, for example, polyvinylphenol (PVP), polymethyl methacrylate (PMMA), polyimide, or fluororesin.

  The active layer 3 includes a soluble organic semiconductor material and a soluble polymer material. The active layer 3 includes a polymer material together with an organic semiconductor material, and the performance (mobility, on / off ratio, etc.) varies among a plurality of organic TFTs as compared to the case where the active layer 3 does not include the polymer material. This is because it becomes difficult. In addition, the organic semiconductor material and the polymer material are both soluble, because the active layer can be formed by a coating method, so that the performance is less likely to vary among a plurality of organic TFTs than when an evaporation method is used. This is because the formation process is simplified.

  In the active layer 3, the soluble organic semiconductor material and the soluble polymer material may be phase-separated. In this case, in order to obtain sufficient electrical conductivity between the source electrode 4 and the drain electrode 5 and the active layer 3, more soluble organic semiconductor material is distributed on the side closer to the side farther from the source electrode 4 and the like. It is preferable that the phases are separated. Furthermore, the soluble organic semiconductor material and the soluble polymer material may be completely separated into two layers.

  Here, the term “soluble” refers to a property in which organic semiconductor materials and polymer materials are dispersed (dissolved and compatible) at a molecular level with respect to a solvent. Processing may be involved. In this case, it is preferable that the organic semiconductor material and the polymer material can be dissolved in a common solvent. Further, the solubility of both is preferably 0.5% by weight or more, more preferably 1% by weight or more, and further preferably 5% by weight or more with respect to the solvent.

  The type of the soluble organic semiconductor material is not particularly limited as long as it is one or more of the organic characteristics having semiconductor characteristics and the above-described solubility.

  Among these, as the soluble organic semiconductor material, a conjugated aromatic material having at least three aromatic rings is preferable. The kind of aromatic ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. These aromatic rings include selenium (Se), tellurium (Te), phosphorus (P), silicon (Si), boron (B), arsenic (As), nitrogen (N), oxygen (O) and sulfur (S ) May be included as a constituent element. Among these, at least one of nitrogen, oxygen, and sulfur is more preferable. In addition, at least a part of the aromatic ring may be substituted with any one or two or more of the substituents listed below. This substituent is, for example, an alkyl group, alkoxy group, polyalkoxy group, thioalkyl group, acyl group, aryl group, halogen group, cyano group, nitro group, alkylamino group (secondary or tertiary) or arylamino. Group (secondary or tertiary) and the like. The type of the halogen group is not particularly limited, and examples thereof include a fluorine group. The substituent may be a derivative of the above-described series of groups.

  Specific examples of the soluble organic semiconductor material include the following materials. Polythiophene, poly-3-hexylthiophene, pentacene [2,3,6,7-dibenzoanthracene], polyanthracene, polypyrrole, polyaniline, polyacetylene or polyphenylene. Polyfuran, polyselenophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene vinylene, polythienylene vinylene, polynaphthalene or polypyrene. Polyazulene, phthalocyanine, merocyanine or polyethylenedioxythiophene, poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid or dioxaneanthanthrene. A derivative of the above material may be used.

  The glass transition temperature of the soluble polymer material is higher than the maximum temperature in the manufacturing process (packaging process) of the electronic device using the organic TFT. This is to prevent the characteristics of the active layer 3 from deteriorating due to the organic TFT being heated at a temperature higher than the glass transition temperature when the organic TFT is put into the packaging process.

  More specifically, the glass transition temperature of the soluble polymer material is preferably higher than 150 ° C. This is because when a liquid crystal display device or the like is assumed as an electronic device, the maximum temperature in the manufacturing process (packaging process) is approximately 150 ° C. However, in consideration of variations in the maximum temperature in the packaging process, the glass transition temperature is preferably 30 ° C. higher than the maximum temperature in the packaging process in order to effectively prevent deterioration of the characteristics of the active layer 3. More preferably, it is 50 ° C. higher. That is, the glass transition temperature is preferably higher than 180 ° C, and more preferably higher than 200 ° C.

  In addition, the molecular weight of the soluble polymer material is not particularly limited as long as the above-described solubility is ensured, but among these, 10,000 or more is preferable, 15000 or more is more preferable, and 20000 or more is more preferable. This depends on the type of polymer material, but its solubility generally increases with increasing molecular weight.

  The type of the soluble polymer material is not particularly limited as long as it is any one or two or more of soluble polymer materials having a glass transition temperature higher than the maximum temperature in the packaging process. Specific examples of the soluble polymer material include the following materials. It is a cyclic olefin copolymer having a glass transition temperature of 180 ° C. or higher. Polyphenyl ether, polyether sulfone or polysulfone having a glass transition temperature of 200 ° C. or higher.

  The mixing ratio of the soluble organic semiconductor material and the soluble polymer material is not particularly limited, but among them, soluble organic semiconductor material: soluble polymer material = 10: 1 to 1:10 is preferable, and 5: 1 to 1: 5 is preferable. More preferably, 3: 1 to 1: 3 is more preferable, and 1: 1 is particularly preferable.

  Here, the active layer 3 is formed using a solution prepared by dissolving a soluble organic semiconductor material and a soluble polymer material in a solvent. The method for forming the active layer 3 is not particularly limited as long as it is a method using a solution, and examples thereof include a dipping method, a spraying method, a coating method, and a printing method. In these formation methods, the active layer 3 containing a solute (a soluble organic semiconductor material and a soluble polymer material) is formed by applying a solution and then drying (volatilizing a solvent) to form a film. . In this case, a heating (firing) treatment may be further performed as necessary. The viscosity of the solution can be adjusted according to the types of the soluble organic semiconductor material and the soluble polymer material, the solid content concentration, and the like.

  Note that the soluble polymer material may already be in a polymer state (polymer) at the time of preparation of the above-described solution, or is still in a low molecular state (monomer) at the time of preparation of the solution, and the solution is applied. After being equalized, it may react to become a polymer state. This reaction is, for example, a polymerization reaction by heat treatment or light irradiation treatment.

  The type of the solvent is not particularly limited as long as it is any one kind or two or more kinds of liquids capable of dissolving the soluble organic semiconductor material and the soluble polymer material. In this case, a material having excellent volatility that does not cause defects in the film (active layer 3) during drying (when the solvent is volatilized) is preferable. Specific examples of the solvent include chlorine-based, aromatic-based materials, ketones, nitrogen-containing materials, sulfur-containing materials, and aliphatic organic-based materials. Chlorine is, for example, dichloromethane, trichloromethane, monochlorobenzene, o-dichlorobenzene, 1,2-dichloroethane, 1,1,1-trichloroethane or 1,1,2,2-tetrachloroethane. The aromatic system is, for example, anisole, toluene, o-xylene, m-xylene, p-xylene or tetralin. Ketones are, for example, 1,4-dioxane, acetone, methyl ethyl ketone, ethyl acetate or n-butyl acetate. Nitrogen-containing compounds are, for example, dimethylformamide, dimethylacetamide, 2-methylpyrrolidone or dimethylimidazolidinone. The sulfur-containing compound is, for example, dimethyl sulfoxide. Aliphatic organic systems are, for example, cyclopentane, cyclohexane or decalin. Among these, in view of ease of handling and stability during preparation of the solution, a solvent having a boiling point higher than 100 ° C. (high boiling solvent) is preferable.

  The source electrode 4 and the drain electrode 5 are made of, for example, a metal material such as gold (Au), platinum (Pt), silver (Ag), copper, aluminum, molybdenum, or an alloy thereof. It may be formed. In particular, the source electrode 4 and the drain electrode 5 are preferably in ohmic contact with the active layer 3.

  Note that the organic TFT may include other components other than those described above. Examples of such other components include a substrate that supports an organic TFT. The substrate may be, for example, a substrate (wafer) made of a metal material such as aluminum, nickel, or stainless steel, or a film made of a plastic material such as polycarbonate (PC) or polyethylene terephthalate (PET).

[Thin Film Transistor Manufacturing Method]
This organic TFT is manufactured by the following procedures, for example. In addition, below, since the formation material of the series of component of organic TFT was already demonstrated, the description is abbreviate | omitted as needed. Moreover, the manufacturing method of the organic TFT demonstrated here is an example to the last, and the formation material, formation method, etc. of each component can be changed suitably.

  First, the gate electrode 1 is formed. In this case, for example, a metal layer is formed, a mask such as a resist pattern is formed on the metal layer by photolithography, and then the metal layer is etched using the mask. Thereafter, the used resist pattern is removed by an ashing method or the like. Examples of the method for forming the metal layer include a sputtering method, a vacuum deposition method, and an electrolytic plating method. Examples of the etching method for the metal layer include ion milling, reactive ion etching (RIE), and wet etching. However, the gate electrode 1 may be formed by other methods such as a printing method. Further, a metal pattern may be used as a mask instead of the resist pattern.

  Subsequently, a gate insulating layer 2 is formed so as to cover the gate electrode 1. The formation method of the gate insulating layer 2 differs depending on, for example, the formation material. When an inorganic material is used, a sputtering method or a chemical vapor deposition (CVD) method is used. When an organic polymer material is used, a coating method or a printing method is used.

  Subsequently, the active layer 3 is formed on the gate insulating layer 2 by the following procedure. First, a solution is prepared by dissolving a soluble organic semiconductor material and a soluble polymer material in a solvent. In this case, as described above, a material having a glass transition temperature higher than the maximum temperature in the manufacturing process (packaging process) of the electronic device is used as the soluble polymer material. Subsequently, the active layer 3 is formed on the surface of the gate insulating layer 2 using a solution by a dipping method, a spraying method, a coating method, a printing method, or the like. Examples of the coating method or the printing method include a cast coating method, a spray coating method, an ink jet printing method, a relief printing method, a flexographic printing method, a screen printing method, a gravure printing method, and a gravure offset printing method. Subsequently, the active layer 3 is etched using the resist pattern as a mask. In this case, for example, a photolithography method or an electron beam lithography method is used as the patterning method, and a wet etching or the like is used as the etching method.

  Finally, the source electrode 4 and the drain electrode 5 are formed on the gate insulating layer 2 so as to be connected to the active layer 3. In this case, first, a metal layer (not shown) is formed so as to cover the gate insulating layer 2 and the active layer 3 using the same material as that for the source electrode 4 and the drain electrode 5. The metal layer is preferably formed by a method that does not damage the active layer 3 during film formation. Subsequently, a mask such as a resist pattern is formed on the metal layer. Finally, the metal layer is selectively etched using a mask to form the source electrode 4 and the drain electrode 5. The method for etching the metal layer is the same as, for example, when the gate electrode 1 is formed, and among them, a method that does not damage the active layer 3 during etching is preferable. Thereby, the organic TFT is completed.

[Operations and effects concerning thin film transistors]
According to this organic TFT, the active layer 3 contains a soluble organic semiconductor material and a soluble polymer material, and the glass transition temperature of the soluble polymer material is higher than the maximum temperature in the packaging process. The glass transition temperature of this soluble polymer material is specifically 150 ° C. or higher. In this case, even if the organic TFT is put into a packaging process including a process involving heating (maximum temperature = 150 ° C.) in the manufacturing process of the electronic device, the characteristics of the active layer 3 are unlikely to deteriorate. For this reason, performance such as mobility and on / off ratio is unlikely to vary among a plurality of organic TFTs. Therefore, the performance can be stabilized and the performance of the electronic device can be improved.

  Further, since the active layer 3 is formed by a coating method using a solution or the like, the active layer 3 can be easily and efficiently compared with a case where the active layer 3 is formed by a vapor deposition method or the like that requires severe manufacturing conditions (high temperature or vacuum). Can be formed. Thereby, manufacturing cost can also be reduced.

[Modification]
The organic TFT is not limited to the bottom gate / top contact type, and may be a bottom gate / bottom contact type as shown in FIG. In this case, the active layer 3 overlaps the upper side of the source electrode 4 and the drain electrode 5. In addition, although not specifically illustrated here, a top gate / top contact type or a top gate / top contact type in which the gate electrode 1 is located above the active layer 3 may be used. In these cases, similar effects can be obtained.

<2. Application example of thin film transistor (electronic equipment)>
Next, application examples of the above-described thin film transistor (organic TFT) will be described. This organic TFT can be applied to various electronic devices.

  For example, the organic TFT is applied to a liquid crystal display device as an electronic device. 4 and 5 show a cross-sectional configuration and a circuit configuration of the main part of the liquid crystal display device, respectively. Note that the device configuration (FIG. 4) and circuit configuration (FIG. 5) described below are merely examples, and the configurations can be changed as appropriate.

[Configuration of electronic equipment]
The liquid crystal display device described here is, for example, an active matrix driving type transmissive liquid crystal display using organic TFTs, and the organic TFTs are used as elements for switching (pixel selection). In this liquid crystal display device, as shown in FIG. 4, a liquid crystal layer 31 is sealed between a driving substrate 10 and a counter substrate 20.

  For example, the driving substrate 10 includes an organic TFT 12, a planarization insulating layer 13, and a pixel electrode 14 formed in this order on one surface of a support substrate 11, and a plurality of organic TFTs 12 and pixel electrodes 14 arranged in a matrix. is there. However, the number of organic TFTs 12 included in one pixel may be one or two or more. 4 and 5 show a case where one organic TFT 12 is included in one pixel, for example. The support substrate 11 is formed of, for example, a transmissive material such as glass or plastic material, and the organic TFT 12 has the same configuration as the organic TFT described above. The kind of plastic material is the same as that described for the organic TFT, for example. The planarization insulating layer 13 is made of an insulating resin material such as polyimide, and the pixel electrode 14 is made of a transparent conductive material such as indium tin oxide (ITO). The pixel electrode 14 is connected to the organic TFT 12 through, for example, a contact hole (not shown) provided in the planarization insulating layer 13.

  The counter substrate 20 is, for example, one in which the counter electrode 22 is formed on the entire surface of the support substrate 21. The support substrate 21 is formed of a transmissive material such as glass or plastic material, and the counter electrode 22 is formed of a conductive material such as ITO. The kind of plastic material is the same as that described for the organic TFT, for example.

  The drive substrate 10 and the counter substrate 20 are bonded to each other with a sealing material 30 so that the pixel electrode 14 and the counter electrode 22 are arranged to face each other with the liquid crystal layer 31 interposed therebetween. The type of liquid crystal molecules contained in the liquid crystal layer 31 can be arbitrarily selected.

  In addition, the liquid crystal display device may include other components (all not shown) such as a retardation plate, a polarizing plate, an alignment film, and a backlight unit.

  A circuit for driving the liquid crystal display device includes a capacitor 15 together with the organic TFT 12, the pixel electrode 14, the counter electrode 22, and the liquid crystal layer 31, for example, as shown in FIG. In this circuit, a plurality of signal lines 32 are arranged in the row direction and a plurality of scanning lines 33 are arranged in the column direction, and the organic TFT 12, the pixel electrode 14, and the capacitor 15 are arranged at positions where they intersect. ing. However, the connection destination of the source electrode, the gate electrode, and the drain electrode in the organic TFT 12 is not limited to the case shown in FIG. The signal line 32 and the scanning line 33 are connected to a signal line driving circuit (data driver) and a scanning line driving circuit (scanning driver) (not shown), respectively.

[Operation of electronic equipment]
In this liquid crystal display device, when the pixel electrode 14 is selected by the organic TFT 12 and an electric field is applied between the pixel electrode 14 and the counter electrode 22, the alignment state of the liquid crystal molecules in the liquid crystal layer 31 according to the electric field strength. Changes. Thereby, the light transmission amount (transmittance) is controlled in accordance with the alignment state of the liquid crystal molecules, so that a gradation image is displayed.

[Manufacturing method of electronic equipment]
This liquid crystal display device is manufactured, for example, by the following procedure.

  First, the drive substrate 10 is manufactured. In this case, a plurality of organic TFTs 12 are formed on one surface of the support substrate 11 so as to be arranged in a matrix by the same procedure as that of the organic TFT described above. As described above, the organic TFT 12 includes an active layer including a soluble organic semiconductor material and a soluble polymer material. In particular, the glass transition temperature of the soluble polymer material is higher than the maximum temperature in the manufacturing process (packaging process) using the organic TFT described below, specifically, higher than 150 ° C. .

  Subsequently, a planarization insulating layer 13 is formed so as to cover the organic TFT 12 and the supporting substrate 11 around it. In this case, for example, a polyimide precursor solution (polyamic acid) is applied by spin coating or the like, and then heated (baked) at 100 ° C. to 150 ° C. for several minutes to form the planarization insulating layer 13. Subsequently, the planarization insulating layer 13 is patterned (exposure and development) by photolithography. Finally, the planarization insulating layer 13 is heated (hard baked) at 150 ° C. for several minutes.

  Subsequently, a plurality of pixel electrodes 14 are formed on the planarization insulating layer 13 so as to be arranged in a matrix. In this case, first, an ITO layer (not shown) is formed so as to cover the surface of the planarization insulating layer 13 by, for example, vapor deposition. Subsequently, a photoresist is applied to the surface of the ITO layer by spin coating or the like, and then heated (baked) for several minutes at 100 ° C. or less to form a photoresist film (not shown). Subsequently, the photoresist film is patterned (exposure, development and overall exposure) by a photolithography method to form a photoresist pattern. Finally, the ITO layer is wet etched using the photoresist pattern as a mask, and then developed and heated at 100 ° C. for 2 minutes.

  Next, the counter electrode 22 is formed so as to cover one surface of the support substrate 21, and the counter substrate 20 is manufactured.

  Finally, after the drive substrate 10 and the counter substrate 20 are bonded to each other through the sealing material 30 so that the pixel electrode 14 and the counter electrode 22 face each other, liquid crystal is injected into a space provided between the two substrates. Thus, the liquid crystal layer 31 is formed. Thereby, a liquid crystal display device is completed.

[Operations and effects relating to electronic devices and manufacturing methods thereof]
According to this liquid crystal display device and its manufacturing method, after forming an organic TFT 12 having an active layer containing a soluble organic semiconductor material and a soluble polymer material, the organic TFT 12 is put into a packaging process. In this case, since the glass transition temperature of the soluble polymer material is set higher than the maximum temperature in the packaging process, the characteristics of the active layer are hardly deteriorated in the packaging process, and between the plurality of organic TFTs 12. Performance is less likely to vary. Therefore, the performance of the electronic device can be improved. Other effects are the same as those of the organic TFT described above. The liquid crystal display device is not limited to the transmissive type, but may be a reflective type.

  Next, examples of the present invention will be described in detail.

(Experimental Examples 1-4)
A bottom-gate / bottom-contact type organic TFT for testing was fabricated and its performance was examined. In the case of manufacturing an organic TFT, first, a silicon wafer doped with boron (B), phosphorus (P), antimony (Sb), or arsenic (As) was prepared as a substrate that functions as a gate electrode. Subsequently, a gate insulating layer (thickness = 150 nm) made of silicon dioxide (SiO ₂ ) was formed on one surface of the silicon wafer. Subsequently, a source electrode and a drain electrode made of gold were formed on the gate insulating layer. In this case, the dimensions (L, W) shown in FIG. 2 were set to L = 50 μm and W = 30 mm. Subsequently, the soluble organic semiconductor material and the soluble polymer material (glass transition temperature Tg: ° C) shown in Table 1 were dissolved in toluene to prepare a solution. In this case, the mixing ratio (weight ratio) of the soluble organic semiconductor material and the soluble polymer material was 1: 1, and the total solid content was 1 wt%. As the soluble organic semiconductor material, a dioxaneanthanthrene compound (derivative of peri-xanthenoxanthene) represented by the formula (1) was used. As the soluble polymer material, polystyrene, cyclic polyolefin (cycloolefin copolymer: TOPAS6015, TOPAS6017: trade names) or polyphenylether (PPE: polyphenylether) manufactured by Polyplastics Co., Ltd. having different molecular weights were used. Subsequently, the solution was applied by spin coating, and then dried at 100 ° C. in an oven to form an active layer (thickness = 50 nm to 100 nm).

  After examining the performance (mobility and on / off ratio) of the organic TFT in a normal temperature environment (23 ° C.), after heating it in an oven at 150 ° C., the performance was examined again. Obtained. In this case, the voltage Vd = −30V, and the on / off ratio indicates the order (only the power of 10).

  Regardless of the Tg of the soluble polymer material, the mobility and on / off ratio were lower after heating than before heating. However, when Tg is higher than the heating temperature (= 150 ° C.), the rate of decrease in mobility and on / off ratio (= [value after heating / value before heating]) compared to the case where the temperature is lower than the heating temperature. × 100:%) was significantly reduced. For this reason, when Tg was made higher than heating temperature, it was confirmed that the fall and dispersion | variation in the performance of organic TFT can be suppressed.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the aspect described in the embodiment, and various modifications can be made. For example, the electronic device to which the thin film transistor of the present invention is applied may be a display device other than the liquid crystal display device. Examples of such other display devices include organic electroluminescence (EL) display devices and electronic paper display devices. Even in this case, the display performance can be improved. In addition, the thin film transistor of the present invention may be applied to electronic devices other than display devices.

  DESCRIPTION OF SYMBOLS 1 ... Gate electrode, 2 ... Gate insulating layer, 3 ... Active layer, 4 ... Source electrode, 5 ... Drain electrode, 10 ... Drive board | substrate, 11, 21 ... Support substrate, 12 ... Organic TFT, 13 ... Planarization insulating layer, DESCRIPTION OF SYMBOLS 14 ... Pixel electrode, 15 ... Capacitor, 20 ... Counter substrate, 22 ... Counter electrode, 30 ... Sealing material, 31 ... Liquid crystal layer, 32 ... Signal line, 33 ... Scanning line

Claims (8)

A gate electrode; and an active layer disposed opposite to the gate electrode through a gate insulating layer and including a soluble organic semiconductor material and a soluble polymer material; and a source electrode and a drain spaced apart from each other and connected to the active layer A thin film transistor including an electrode;
A packaging member to be packaged with the thin film transistor,
The glass transition temperature of the soluble polymer material is higher than the highest temperature in the process of packaging the thin film transistor with the packaging member.   The electronic device according to claim 1, wherein the soluble polymer material has a glass transition temperature of 150 ° C. or higher.   The electronic device according to claim 1, wherein the soluble polymer material includes polyphenyl ether.   The electronic device according to claim 1, wherein the solubility of the soluble organic semiconductor material and the soluble polymer material is 0.5% by weight or more with respect to a common solvent.   The electronic device according to claim 1, wherein the packaging member includes an insulating layer covering the thin film transistor or an electrode connected to the thin film transistor. A gate electrode; and an active layer disposed opposite to the gate electrode through a gate insulating layer and including a soluble organic semiconductor material and a soluble polymer material; and a source electrode and a drain spaced apart from each other and connected to the active layer Forming a thin film transistor including an electrode;
Packaging the thin film transistor with a packaging member,
The manufacturing method of the electronic device which makes the glass transition temperature of the said soluble polymeric material higher than the highest temperature in the process in which the said thin-film transistor is packaged with the said packaging member.   The method of manufacturing an electronic device according to claim 6, wherein the packaging process includes a photolithography process and a wet etching process. A gate electrode; and an active layer disposed opposite to the gate electrode through a gate insulating layer and including a soluble organic semiconductor material and a soluble polymer material; and a source electrode and a drain spaced apart from each other and connected to the active layer An electrode, and
The glass transition temperature of the soluble polymer material is 150 ° C. or higher.
Thin film transistor.

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