JP2020088225A - Thin film transistor, image display device, sensor device and manufacturing method of thin film transistor - Google Patents

Abstract

To provide a thin film transistor using an organic semiconductor, in which adhesion of interlayer insulator and a protective layer is good even when fluorine-based resin is used in the protective layer of the organic semiconductor, not exfoliate even when bent, and the characteristics are stable.SOLUTION: In a thin film transistor 100 where a gate electrode 2, a gate insulator 3, a source electrode 4 and a drain electrode 5, an organic semiconductor layer 6 formed across the source electrode and the drain electrode, a protective layer 7 formed to coat the same, and an interlayer insulator 10 are provided, in this order, on the flexible base material 1, a first self integration film 8 composed of a material capable of increasing the work function of the electrode, and reducing contact resistance with the organic semiconductor layer is provided on the lateral faces of the source electrode and the drain electrode, and a second self integration film 9 composed of a material capable of increasing adhesion to the interlayer insulator is provided on the top faces of the source electrode and the drain electrode.SELECTED DRAWING: Figure 1

Description

The present invention relates to a thin film transistor formed on a flexible base material. More specifically, the present invention relates to a thin film transistor that does not malfunction even when a flexible substrate is curved.

At present, the mainstream of semiconductor materials is silicon (Si). As a method for forming a semiconductor layer using a silicon-based material, a silicon thin film or a thin film of a metal and an insulator material is formed by a dry film forming method such as sputtering or CVD, and then patterned by using a photolithography method. A method of forming a thin film transistor is common.

On the other hand, research into transistors (organic transistors) using organic semiconductors has become active from the viewpoints of flexibility, weight reduction, and cost reduction. Generally, when an organic semiconductor is used, a printing process which is a wet method is possible. By using this printing technique, the cost of the apparatus and manufacturing is lower than that of the photolithography method, and since there is no need for vacuum or high temperature, there are advantages such as the use of a plastic substrate.

The field of application thereof is wide and is not limited to flexible displays such as thin and lightweight electronic paper, and is also expected to be applied to RFID (Radio Frequency Identification) tags and sensor devices.

For these reasons, thin film transistors using organic semiconductors are currently receiving attention.

A thin film transistor using an organic semiconductor has the above advantages, but has a problem that the TFT (Thin Film Transistor) characteristic is poor because a large electrical contact resistance is interposed between the organic semiconductor layer and the electrode. There is a point.

In order to solve this problem, attempts have been made to control the wettability and the work function of the metal electrode surface by surface-modifying the metal electrode with, for example, an organic compound having a thiol group at the terminal to form a self-assembled film layer. There is. Patent Document 1 discloses a TFT using an electrode surface treatment agent having a functional group that chemically bonds with a metal.

On the other hand, in order to increase the display contrast, it is necessary to form the pixel electrode in the pixel unit as much as possible and increase the ratio (aperture ratio) of the effective area of the pixel in the pixel unit. In a reflective display device such as an electrophoretic display, a low aperture ratio causes a significant reduction in contrast. This is because the influence of the reflected light from the non-display portion cannot be ignored as compared with the reflected light from the display portion. Therefore, in a thin film transistor for a reflective display device, in order to increase the aperture ratio, an interlayer insulating film having an opening on the pixel electrode of the thin film transistor is provided on a sealing layer (semiconductor protective layer), and the pixel electrode is formed thereon. It has been practiced to provide a connected upper pixel electrode.

Further, in order to reduce the influence of the organic solvent when forming the protective layer, a fluorine resin is generally used for the protective layer. However, the fluorine-based resin has a problem that the surface free energy is small and the adhesion with the upper interlayer insulating film is poor.

Therefore, due to poor adhesion between the protective layer and the interlayer insulating film, when the thin film transistor is bent, peeling occurs from the interface between the protective layer and the interlayer insulating film, and normal transistor characteristics cannot be obtained.

JP, 2008-060117, A

The present invention has been made in view of the above problems, and its problem is that in a thin film transistor using an organic semiconductor, even when a fluorine-based resin is used for a protective layer of the organic semiconductor, an interlayer insulating film and a protective film are protected. An object of the present invention is to provide a thin film transistor whose layer has good adhesion and does not peel off even when curved, and whose characteristics are stable.

As a means for solving the above problems, the invention according to claim 1 of the present invention provides a gate electrode, a gate insulating film, a source electrode and a drain electrode, a source electrode and a drain on an insulating flexible base material. An organic semiconductor layer formed over the electrode, a protective layer formed to cover the organic semiconductor layer, an interlayer insulating film, and an upper pixel electrode, in a thin film transistor provided in this order,
A first self-assembled film is provided on the side surfaces of the source electrode and the drain electrode, and a second self-assembled film is provided on the upper surfaces of the source electrode and the drain electrode.
The first self-assembled film is made of a material that can reduce the contact resistance with the organic semiconductor layer by increasing the work functions of the source electrode and the drain electrode,
The second self-assembled film is a thin film transistor, which is made of a material capable of increasing the adhesion between the source electrode and the drain electrode and the interlayer insulating film by increasing the surface free energy.

The invention according to claim 2 is characterized in that the first self-assembled monolayer is a self-assembled monolayer made of a material containing an organic molecule having a fluorine group. Thin film transistor.

Further, in the invention according to claim 3, the second self-assembled film is a self-assembled film containing at least one of an amino group, an epoxy group, and a mercapto group at the end, or two or more. It is a monomolecular film, It is a thin-film transistor of Claim 1 or 2 characterized by the above-mentioned.

The invention according to claim 4 is the thin film transistor according to any one of claims 1 to 3, wherein the protective layer contains a fluororesin.

Further, the invention according to claim 5 is a step of forming a gate electrode, a step of forming a gate insulating film, a step of forming a source electrode and a drain electrode on an insulating flexible base material, and an organic semiconductor. In the method of manufacturing a thin film transistor, which comprises a step of forming a layer, a step of forming a protective layer, and a step of forming an interlayer insulating film,
In the step of forming the source electrode and the drain electrode, a resist pattern is formed on the metal layer forming the source electrode and the drain electrode, the metal layer at an unnecessary portion is removed by etching through the resist pattern, and then the resist pattern is formed. Before peeling, increasing the work function of the metal layer on the side surface of the exposed metal layer, the step of forming a layer made of a material capable of reducing the contact resistance with the organic semiconductor layer, and after peeling the resist pattern, And a step of forming a layer made of a material capable of improving the adhesiveness with the interlayer insulating film on the upper surface of the metal layer.

In the invention according to claim 6, the step of forming a layer made of a material capable of reducing the contact resistance with the organic semiconductor layer is a self-assembled monomolecule made of a material containing an organic molecule having a fluorine group. Is a process of forming a film,
The step of forming a layer made of a material capable of improving the adhesiveness with the interlayer insulating film on the upper surface of the metal layer includes at least one of an amino group, an epoxy group and a mercapto group, or two. 7. The method of manufacturing a thin film transistor according to claim 6, which is a step of forming a self-assembled monolayer including the above.

The invention described in claim 7 is an image display device comprising an image display medium using the thin film transistor according to any one of claims 1 to 4.

The invention described in claim 8 is a sensor device using the thin film transistor according to any one of claims 1 to 4.

According to the thin film transistor of the present invention, a structure in which a gate electrode/gate insulating film/source/drain electrodes are formed in this order on a flexible substrate is provided, and an organic semiconductor is further formed across the source/drain electrodes. Is becoming A first integrated film that reduces the contact resistance with the organic semiconductor is formed on the side surface of the source/drain electrode that is in contact with the organic semiconductor. Therefore, the ON/OFF characteristics of the thin film transistor can be improved. Further, on the upper surface of the source/drain electrodes, there is formed a second integrated film capable of improving the adhesion with the interlayer insulating film. Therefore, even if the protective layer contains a fluorine-based resin, the adhesion between the interlayer insulating film formed on the protective layer and the source/drain electrodes is good, so that even if the thin film transistor bends, it is protected. The layer and the interlayer insulating layer are not separated from each other, and the transistor characteristics are not adversely affected.

Further, according to the image display device of the present invention, since the thin film transistor array using the thin film transistor of the present invention is used, a good ON/OFF ratio can be obtained even when an organic semiconductor is used. Further, even if the image display device is curved, the thin film transistor characteristics do not deteriorate. Therefore, a good image display can be obtained.

Further, according to the method of manufacturing a thin film transistor of the present invention, the thin film transistor of the present invention can be manufactured.

FIG. 3 is a sectional view of a thin film transistor according to an embodiment of the present invention. 6A and 6B are cross-sectional views illustrating a method for forming a thin film transistor of the invention. FIG. 4 is an image diagram of flexibility evaluation in Example 1. FIG. 4 is a cross-sectional view of a thin film transistor according to Comparative Example 1. FIG. 6 is a cross-sectional view of a thin film transistor according to Comparative Example 2. FIG. 6 is a cross-sectional view of a thin film transistor according to Comparative Example 3.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

<Thin film transistor>
A thin film transistor of the present invention includes a gate electrode, a gate insulating film, a source electrode and a drain electrode, a semiconductor layer formed over the source electrode and the drain electrode, and a semiconductor layer on an insulating flexible base material. A thin film transistor including a protective layer formed so as to cover, an interlayer insulating film, and an upper pixel electrode in this order.

The first self-assembled film is provided on the side surfaces of the source electrode and the drain electrode, and the second self-assembled film is provided on the upper surfaces of the source electrode and the drain electrode.

The first self-integrating film is made of a material capable of increasing the work functions of the source electrode and the drain electrode and reducing the contact resistance with the semiconductor layer, and the second self-integrating film has an adhesion property with the interlayer insulating film. The feature is that it is made of a material that can be raised.

The first self-assembled film may be a self-assembled monomolecular film made of a material containing an organic molecule having a fluorine group.

Further, the second self-assembled monolayer may be a self-assembled monomolecular film containing at least one of the amino group, the epoxy group, and the mercapto group, or two or more at the terminal.

Further, the protective layer may contain a fluororesin.

Further, the semiconductor layer may be an organic semiconductor.

Next, the thin film transistor of the present invention will be described in detail with reference to FIGS.
FIG. 1 shows a sectional view of a thin film transistor according to an embodiment of the present invention. The thin film transistor 100 of the present invention includes a base material 1, a gate electrode 2, a gate insulating film 3, a source electrode 4, a drain electrode 5, and a semiconductor layer 6 laminated between the source electrode 4 and the drain electrode 5. A protective layer 7 stacked on the semiconductor layer 6, an interlayer insulating film 10 formed on the source electrode 4 and the drain electrode 5 and the semiconductor protective layer 6 to insulate the upper pixel electrode 11 from the source electrode 4. And an upper pixel electrode 11 formed on the interlayer insulating film 10 and connected to the drain electrode 5 through the opening of the interlayer insulating film 10.

(Base material)
In the embodiment of the present invention, the material used for the substrate 1 is not particularly limited, and examples thereof include polyethylene terephthalate (PET), polyimide, polyether sulfone (PES), polyethylene naphthalate (PEN), and polycarbonate. Examples include flexible plastic materials.

(Gate electrode)
The material used for the gate electrode 2 is not particularly limited, but a metal such as Al, Cr, Au, Ag, Ni, Cu, Mo, or a transparent conductive film such as ITO can be used. As a forming method, a photolithography method may be used after vapor deposition or sputtering, but a printing method (screen printing, flexographic printing, gravure printing, offset printing, reverse offset printing, etc.) can be used. When printing is used, Ag ink, Ni ink, Cu ink or the like can be used. In particular, flexographic printing and reverse offset printing are suitable as a method for forming the gate electrode 2 because thin film printing is possible and flatness is excellent.

(Gate insulation film)
The material of the gate insulating film 3 is an oxide insulating material such as silicon oxide (SiOx), aluminum oxide (AlOx), tantalum oxide (TaOx), yttrium oxide (YOx), zirconium oxide (ZrOx), and hafnium oxide (HfOx). Silicon nitride (SiNx), silicon oxynitride (SiON), polyacrylate such as polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), resin material such as polyvinylphenol (PVP), polysilsesquioxane (PSQ) Such organic/inorganic hybrid resins can be used, but are not limited thereto. These may be a single layer or a laminate of two or more layers, or may be a functionally gradient material whose composition is graded in the thickness direction of the layers.

The method for forming the gate insulating film 3 includes a vacuum deposition method such as a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD method, a photo CVD method, a hot wire CVD method, a spin coating method, and the like. A wet film-forming method such as a die coating method or a screen printing method can be appropriately used depending on the material.

(Source electrode/drain electrode)
Next, the source electrode 4 and the drain electrode 5 are formed on the gate insulating film 3. As the material of the source electrode 4 and the drain electrode 5, metal materials such as aluminum (Al), molybdenum (Mo) and other molybdenum alloys such as MoNb, indium oxide (In ₂ O ₃ ), tin oxide (SnO), A conductive metal oxide material such as zinc oxide (ZnO), indium tin oxide (ITO), or indium zinc oxide (IZO) can be used. A noble metal-based metal such as silver, gold, platinum, or palladium has a large work function and a hole injection barrier to an organic semiconductor is small, which is preferable.

The source electrode 4 and the drain electrode 5 are preferably formed by a wet film formation method using a precursor of a conductive material, nanoparticles, or the like. For example, a method such as an inkjet method, a letterpress printing method, a lithographic printing method, an intaglio printing method, a screen printing method can be used. The patterning can be performed by, for example, protecting the pattern forming portion with a resist or the like by using a photolithography method, removing unnecessary portions by etching, or directly patterning by a printing method. However, the patterning is not limited to these. Not a thing.

(First self-assembled film)
For forming the first self-assembled film 8, it is possible to use a material that has affinity with a metal or an oxygen atom and can be surface-modified. Among the materials that can be used, a material known as a self-assembled monolayer (SAMs: Self-Assembled Monolayers) agent can be preferably used. Examples thereof include, but are not limited to, a thiol compound having a fluorine atom or a phenyl group, a disulfide compound, a silane coupling agent, or a phosphonic acid compound. By increasing the work functions of the source electrode 4 and the drain electrode 5 and reducing the contact resistance with the semiconductor layer 6, it is effective in improving the device characteristics. Therefore, in particular, an organic molecule having a fluorine group is contained. The material to be used is preferably used.

(Second self-assembled film)
Examples of the material of the second self-assembled film 9 include, but are not limited to, a thiol compound, a disulfide compound, a silane coupling agent, or a phosphonic acid compound.

By replacing the end of the self-assembled film with various functional groups, the surface free energy on the second self-assembled film 9 can be controlled. For example, a monomolecular film modified with an amino group, an epoxy group, a mercapto group, or the like, preferably a self-assembled monomolecular film generally tends to have a large surface free energy. Therefore, by forming a self-assembled film having a large surface free energy, it is possible to improve the adhesiveness with the interlayer insulating film 10 formed in the upper layer.

The formation of these self-assembled films can be carried out by immersing the substrate on which the metal layer is formed in a solution of the above organic thin film layer material. Alternatively, a vapor phase method in which the substrate is exposed to the vapor of the solution can be used. Further, heat treatment may be performed thereafter.

By using the first self-assembled film 8, the work function of the electrode can be increased and the contact resistance between the electrode and the semiconductor can be reduced. Therefore, the current value when the thin film transistor 100 is turned on can be increased. The element characteristics are improved. Further, by using the second self-assembled film, the adhesiveness with the interlayer insulating film 10 formed in the upper layer can be improved, so that the interlayer insulating film 10 and the protective layer 7 are protected against bending of the substrate on which the thin film transistor 100 is formed. Peeling can be suppressed, and a stable thin film transistor 100 can be manufactured.

(Semiconductor layer)
Next, the source electrode 4 and the drain electrode 5 are formed on the gate insulating film 3, and the semiconductor layer 6 is further formed so as to connect these electrodes. Examples of the material of the semiconductor layer 6 include low molecular organic semiconductor materials such as pentacene, tetracene, phthalocyanine, perylene, thiophene, benzodithiophene, anthradithiophene, and derivatives thereof, and carbon compounds such as carbon nanotubes. Polymeric organic semiconductor materials such as polythiophene, polyallylamine, fluorene bithiophene copolymer, and derivatives thereof can be preferably used, but the invention is not limited thereto.

(Protective layer)
Next, the protective layer 7 is formed so as to cover the semiconductor layer 6. The protective layer 7 is formed to protect the semiconductor layer 6 from moisture and oxygen in the surrounding environment and various kinds of pollution. The protective layer 7 needs to be formed so as to cover at least a region of the semiconductor layer 6 that overlaps with the channel portion.

Examples of the material of the protective layer 7 include inorganic materials such as silicon oxide, aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, hafnium aluminate, zirconium oxide, and titanium oxide, and polymethyl methacrylate (PMMA). Examples thereof include insulating materials such as acrylate, PVA (polyvinyl alcohol), PVP (polyvinyl phenol), and fluororesin, but are not limited thereto.

As a method for forming the protective layer 7, known methods such as a relief printing method, a reverse offset printing method, an inkjet printing method, a screen printing method, a spray coating method and a spin coating method can be preferably used, but the process is performed at a low temperature, It is preferable to form by an inexpensive printing method with a small number of steps. In particular, screen printing is preferable because it has a wide range of ink viscosity application, high ink material selectivity, high ink use efficiency, and easy area enlargement. Flexographic printing is also preferable because it is easy to increase the area. The shape of the protective layer 7 is not particularly limited, and may be an island shape such as a dot, or a source wiring (a plurality of source electrodes 4 are connected when the thin film transistors are arranged in a matrix). The stripe shape may be parallel to the wiring (not shown).
That is, the continuous protective layer 7 is formed so as to cover the stripe-shaped semiconductor layer 6 formed between the plurality of source and drain electrodes.

(Interlayer insulation film)
The material used for the interlayer insulating film 10 is not particularly limited, but commonly used materials include organic materials such as polyvinyl phenol, polymethyl methacrylate, polyimide, polyvinyl alcohol, and epoxy resin. In forming the interlayer insulating film 10, known methods such as a letterpress printing method, a reverse offset printing method, an inkjet printing method, a screen printing method, a spray coating method, a spin coating method can be preferably used. The printing method is preferable in view of flexibility and cost reduction. Further, it is preferable to reduce the voltage drop due to the source wiring of the thin film transistor 100 and the influence of the voltage drop from the source electrode 4 to the upper pixel electrode 11. Therefore, in order to reduce the electric resistance as much as possible, it is necessary to form a relatively thick film, and screen printing can be preferably used.

(Upper pixel electrode)
The material used for the upper pixel electrode 11 is not particularly limited, but for example, a metal such as platinum, nickel, indium tin oxide, or a thin film of a metal oxide, or poly(3,4-ethylenedioxythiophene). A conductive polymer such as (PEDOT)/polystyrene sulfonate (PSS) or polyaniline or a solution in which metal colloid particles such as gold, silver and nickel are dispersed, or a thick film paste using metal particles such as silver as a conductive material, In addition, the forming method is not particularly limited, and a dry film forming method such as a vacuum vapor deposition method or a sputtering method can also be used.However, considering flexibility and cost reduction, etc. Then, it is desirable to form by a printing method such as screen printing, reverse offset printing, flexographic printing, and inkjet method.

<Image display device>
A thin film transistor array can be formed by arranging a plurality of thin film transistors on a substrate in a matrix. The thin film transistor array can be used in an image display device in combination with various image display media. As the image display medium, each image display medium such as an electrophoretic reflection display device, a transmission type liquid crystal display device, a reflection type liquid crystal display device, a semi-transmission type liquid crystal display device, an organic EL display device and an inorganic EL display device should be used. You can The image display device can be used in electronic paper, organic EL display device or liquid crystal display device.

Further, the thin film transistor of the present invention can also be used in a sensor device such as a pressure sensor, an optical sensor, a chemical sensor, a biosensor, or the like.

Next, examples of the present invention will be described.

<Example 1>
The thin-film transistor array substrate which concerns on each embodiment of this invention was manufactured, and the result of having evaluated it is shown. A polyimide film (Upilex, a registered trademark of Ube Industries, Ltd.) was used as the material of the substrate 1 of the thin film transistor 100 shown in FIG.
First, aluminum was formed on the base material 1 by a sputtering method so as to have a thickness of 100 nm, and then the gate electrode 2 was formed by a photolithography method using a positive resist.
Next, an acrylic resin was applied on the base material 1 on which the gate electrode 2 was formed by a die coater and dried at 180° C. for 1 hour to form the gate insulating film 3.

A method of forming the source electrode 4 and the drain electrode 5 and thereafter will be described with reference to FIGS.
First, an Ag thin film was formed as a sputtered metal film 30 on the gate insulating film 3 by a sputtering method so as to have a thickness of 100 nm (see FIG. 2A).
Next, as the resist 31, a positive resist was applied by spin coating and dried (see FIG. 2B).
Next, a desired pattern was exposed on the resist 31 and developed to obtain a resist pattern 32 (see FIG. 2C).
Next, the source electrode 4 and the drain electrode 5 made of the Ag thin film were patterned by immersing the Ag thin film in an etching solution (see FIG. 2D).
Next, it was dipped in a pentafluorothiophenol solution (manufactured by Tokyo Chemical Industry Co., Ltd.) to form the first self-assembled film 8 on the side surface of the exposed Ag thin film (FIG. 2(e)).
Next, the resist pattern 32 was removed using a resist remover (FIG. 2(f)).
Next, the second self-assembled film 9 was formed on the upper surface of the Ag thin film exposed by dipping the resist pattern 32 in a 9-amino-1-octanethiol solution (FIG. 2(g)).
).

Next, the forming process from FIG. 2G to FIG. 2H will be described.
First, as a semiconductor material, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) (manufactured by Aldrich) was used. Using a solution of tetralin (manufactured by Kanto Chemical Co., Inc.) dissolved at 2% by weight as an ink, a semiconductor layer 6 was formed by a flexographic printing method so as to extend over the source electrode 4 and the drain electrode 5.

Next, a solvent-soluble fluororesin was applied onto the semiconductor layer 6 by a flexographic printing method so as to cover the semiconductor layer 6, dried at 150° C. and solidified to form a protective layer 7.

As the material of the interlayer insulating film 10 formed on the protective layer 7, a negative photosensitive acrylic resin material was used and was applied by the die coating method. After drying, exposure was performed using a photomask having a desired shape, and unnecessary resin material was removed by development to form an interlayer insulating film 10 having a desired pattern shape. Then, baking was performed at 150° C. to form the interlayer insulating film 10.

Next, after printing a silver paste in a desired shape on the interlayer insulating film 10 by a screen printing method, the silver paste was dried at 120° C. to form the upper pixel electrode 11 to obtain the thin film transistor 100.

The transfer characteristic of the thin film transistor 100 manufactured as described above was measured using a semiconductor parameter analyzer B1500A (manufactured by Agilent).

As a result of the measurement, the _on / _off ratio, which is the ratio of the I _on and the I _off current value of the transistor, was 10 ⁴ , and it was confirmed that favorable transistor characteristics were exhibited.

Then, as an evaluation of flexibility, as shown in FIG. 3, a transfer parameter was measured by a semiconductor parameter analyzer B1500A as a thin film transistor 41 which was bent by winding the manufactured thin film transistor 100 around a test rod 40 having a diameter of 4 mm. As a result, the on/off ratio was 10 ⁴ as in the case before the flexibility test, and excellent transistor characteristics were exhibited.

Further, when the transistor whose flexibility was evaluated was observed with an optical microscope, no particular problem was found.

<Image display device>
When the thin film transistor 100 manufactured in Example 1 is arranged in a matrix to form a thin film transistor array and an electrophoretic image display medium sandwiched between the counter electrodes is driven, display switching can be performed satisfactorily without any problem. It was confirmed that there is.

<Sensor device>
The thin film transistor 100 manufactured in Example 1 is arranged in a matrix to form a thin film transistor array, and a pressure sensor device capable of detecting a pressure distribution made of conductive rubber whose resistance value changes with respect to the thickness sandwiched between the counter electrodes is manufactured. Then driven. As a result, we were able to obtain area distribution data corresponding to the pressure applied to the pressure sensor device.

<Comparative Example 1>
As Comparative Example 1, a thin film transistor described below was manufactured. FIG. 3 shows a cross-sectional view of the thin film transistor 200 according to Comparative Example 1. The thin film transistor 200 according to the comparative example is the same as that of the example 1 except that the first self-integrating film 8 and the second self-integrating film 9 in FIG. 1 are not provided.

In this thin film transistor 200, since the electrical contact resistance between the semiconductor layer 6, the source electrode 21, and the drain electrode 22 is large, and the current value Ion flowing when the thin film transistor 200 is ON is small, the on/off ratio is 102, which is a good transistor. No properties were obtained.

Further, the flexibility was evaluated in the same manner as in Example 1, but the transistor characteristics could not be obtained. Observation with a microscope confirmed that the interlayer insulating film 10 was peeled off.

<Comparative example 2>
As Comparative Example 2, a thin film transistor described below was manufactured. FIG. 4 shows a cross-sectional view of the thin film transistor 201 according to Comparative Example 2. The thin film transistor 201 according to the comparative example does not have the second self-integrating film, and the portion where the second self-integrating film is formed in the first embodiment is also formed except that the first integrated film 8 is formed. This is the same as the first embodiment.

As a result, the on/off ratio was 10 ⁴ , and good transistor characteristics could be confirmed.

After that, the flexibility was evaluated and the measurement was performed, but the transistor characteristics could not be obtained. By microscopic observation as in Comparative Example 1, it was confirmed that the interlayer insulating film 10 was peeled off.

<Comparative example 3>
As Comparative Example 3, a thin film transistor described below was manufactured. FIG. 5 shows a cross-sectional view of the thin film transistor 202 according to Comparative Example 3. The thin film transistor 202 according to Comparative Example 3 is similar to that of Example 1 except that the first self-integrated film 8 and the second self-integrated film 9 are formed in reverse.

When the second self-assembled film 9 is used on the side surfaces of the source electrode 4 and the drain electrode 5, the work function of each electrode does not increase, and the contact resistance between the source electrode 4 and the drain electrode 5 and the semiconductor layer 6 is reduced. Is large, I _on is small, the on/off ratio is 10 ² , and good transistor characteristics cannot be obtained.

After that, the flexibility was evaluated and the measurement was performed, but the transistor characteristics could not be obtained. Similar to Comparative Examples 1 and 2, it was confirmed by microscopic observation that the interlayer insulating film 10 was peeled off.

Table 1 shows a summary of the results of Example 1 and Comparative Examples 1 to 3. When there is no problem in the appearance observation after the test, “◯” is indicated, and when peeling of the interlayer insulating film 10 is observed, it is indicated as “x”.
Further, the transfer characteristics of the thin film transistor can be confirmed after the evaluation of the flexibility, and the characteristics are good, and those having no problem in the appearance observation after the flexibility test were judged as "○", after the flexibility evaluation. When the transfer characteristics of the thin film transistor could not be confirmed and there was a problem in the appearance observation, it was indicated as “x”.

As shown in Table 1, in Example 1, the transistor characteristics could be confirmed even after the evaluation of the flexibility, the on/off ratio of the thin film transistor was good, and the appearance observation had no problem.

INDUSTRIAL APPLICABILITY The present invention is useful for articles using thin film transistors and thin film transistor arrays formed on a flexible substrate, such as image display devices and sensors.

1 Base Material 2 Gate Electrode 3 Gate Insulating Film 4 Source Electrode 5 Drain Electrode 6 Organic Semiconductor Layer 7 Protective Layer 8 First Self-Integrating Film 9 Second Self-Integrating Film 10 Interlayer Insulating Film 11 Upper Pixel Electrode 21 Source Electrode 22 Drain Electrode 30 Sputtered metal film 31 Resist 32 Resist pattern 40 Test rod 41 Thin film transistor 100, 200, 201, 202 Thin film transistor

Claims (8)

A gate electrode, a gate insulating film, a source electrode and a drain electrode, an organic semiconductor layer formed over the source electrode and the drain electrode, and an organic semiconductor layer are coated on an insulating flexible base material. In the thin film transistor in which the formed protective layer, the interlayer insulating film, and the upper pixel electrode are provided in this order,
A first self-assembled film is provided on the side surfaces of the source electrode and the drain electrode, and a second self-assembled film is provided on the upper surfaces of the source electrode and the drain electrode.
The first self-assembled film is made of a material that can reduce the contact resistance with the organic semiconductor layer by increasing the work functions of the source electrode and the drain electrode,
The second self-integrating film is made of a material capable of increasing the adhesion between the source electrode and the drain electrode and the interlayer insulating film by increasing the surface free energy. The thin film transistor according to claim 1, wherein the first self-assembled film is a self-assembled monomolecular film made of a material containing an organic molecule having a fluorine group. The second self-assembled monolayer is a self-assembled monolayer including at least one of an amino group, an epoxy group, and a mercapto group, or two or more at the terminal. Item 3. The thin film transistor according to Item 1 or 2. The thin film transistor according to claim 1, wherein the protective layer contains a fluorine-based resin. A step of forming a gate electrode, a step of forming a gate insulating film, a step of forming a source electrode and a drain electrode, a step of forming a semiconductor layer, and a step of forming a protective layer over an insulating flexible base material. In the method of manufacturing a thin film transistor, which comprises a step and a step of forming an interlayer insulating film in this order,
In the step of forming the source electrode and the drain electrode, a resist pattern is formed on the metal layer forming the source electrode and the drain electrode, the metal layer at an unnecessary portion is removed by etching through the resist pattern, and then the resist pattern is formed. Prior to peeling, the step of increasing the work function of the metal layer on the side surface of the exposed metal layer to form a layer made of a material capable of reducing the contact resistance with the semiconductor layer, and after peeling the resist pattern, the metal And a step of forming a layer made of a material capable of improving the adhesiveness with the interlayer insulating film on the upper surface of the layer. The step of forming a layer made of a material capable of reducing the contact resistance with the semiconductor layer is a step of forming a self-assembled monolayer made of a material containing an organic molecule having a fluorine group,
The step of forming a layer made of a material capable of improving the adhesiveness with the interlayer insulating film on the upper surface of the metal layer includes at least one of an amino group, an epoxy group and a mercapto group, or two. The method for manufacturing a thin film transistor according to claim 6, which is a step of forming a self-assembled monolayer including the above. An image display device comprising an image display medium using the thin film transistor according to claim 1. A sensor device comprising the thin film transistor according to claim 1.

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