JP2020161523A - Organic semiconductor thin film transistor element - Google Patents

Abstract

To provide an organic semiconductor thin film transistor element that can prevent step breakage and interfacial peeling by improving the adhesion of at least edge portions of a source electrode and a drain electrode on the channel side to an organic semiconductor layer and a gate insulating layer in a thin film transistor element using an organic semiconductor.SOLUTION: An organic semiconductor thin film transistor element 1 in which a gate electrode 11, a gate insulating layer 12, a source electrode 13, a drain electrode 14, and an organic semiconductor layer 15 are provided on an insulating substrate 10 in this order is equipped with a stepped taper and an uneven structure in which the adhesion to the organic semiconductor layer is enhanced by increasing the surface area of the side surface and at least a part of the upper surface where both the source electrode and the drain electrode are in contact with the organic semiconductor layer at the opposite end.SELECTED DRAWING: Figure 2

Description

The present invention relates to a thin film transistor element having an organic semiconductor as a channel layer.

In recent years, in addition to thin film transistors that use silicon (a-Si, p-Si, etc.) for the semiconductor layer, electronic devices that use thin films made of organic semiconductor materials have been energetically developed. Among them, organic thin film transistors have been energetically developed. Organic electronic devices (hereinafter, may be simply abbreviated as organic devices) are attracting attention. The ultimate goal of these organic devices is low cost, light weight, flexibility and high performance. Compared to inorganic materials centered on silicon, organic semiconductor materials
(1) A large-area organic device can be manufactured at low cost by a simple process at a low temperature.
(2) It is possible to manufacture a flexible organic device.
(3) By modifying the molecules constituting the organic material to a desired form, the performance and physical properties of the organic device can be controlled.
It has various advantages such as.

Generally, an organic thin film transistor element can be divided into two structures. One is a top contact type in which the source electrode and the drain electrode are formed after the organic semiconductor layer is formed, and the other is a bottom contact type in which the organic semiconductor layer is formed after the source electrode and the drain electrode are formed. (See, for example, Non-Patent Document 1).

The top contact type organic thin film transistor element has superior characteristics to the bottom contact type organic thin film transistor element in that the barrier in carrier injection from the electrode to the organic semiconductor layer and the contact resistance between the electrode and the organic semiconductor layer are smaller. have. However, it is vulnerable to solution treatment such as etching treatment used in general electrode formation, it is difficult to use such treatment after forming an organic semiconductor layer, and there is a problem that it cannot cope with a complicated circuit configuration. is there. Further, in order to lower the operating voltage of the transistor element, it is necessary to shorten the channel length determined by the distance between the source electrode and the drain electrode to about 1 μm, but instead of the etching process, another method, for example, a mask deposition method, is used. Even when it is used, the limit is about several tens of μm, and there is a problem that it is difficult to process it below this.
Therefore, the importance of improving the bottom contact type organic thin film transistor is increasing.

In a bottom contact type organic thin film transistor element, an organic semiconductor layer is formed straddling a step at the end of a source electrode and a drain electrode. Therefore, when a flexible substrate is bent, the step causes the source electrode and the drain electrode. So-called "step breakage" (16 in FIG. 4) and interfacial peeling (17 in FIG. 4), in which the organic semiconductor layer is cut at a portion overlapping the step of the drain electrode, are likely to occur. The occurrence of step breakage and interfacial delamination results in an increase in connection resistance between the organic semiconductor material and the source and drain electrodes. When the connection resistance between the organic semiconductor material and the source electrode and the drain electrode increases, the on-current of the thin film transistor element decreases, and the desired characteristics for operating the thin film transistor element cannot be obtained, so that the manufacturing yield of the thin film transistor element increases. It becomes a factor to reduce.

A silver electrode is generally used as a material for forming an electrode (including a gate electrode) of an organic thin film transistor element (see Non-Patent Documents 2 and 3). In order to solve the problem of increased connection resistance due to step breakage and interfacial peeling, it is an effective method to provide tapered portions at the edges of the source electrode and drain electrode formed on the gate insulating layer. For example, a structure having a tapered portion on the channel side of the source electrode and the drain electrode is disclosed (see Patent Document 1). However, even if the edges of the source electrode and the drain electrode are tapered, if the taper is not in an appropriate shape, the contact area between the organic semiconductor layer and the source electrode and the drain electrode does not increase, and the adhesion is improved. Since it does not, the problem of step breaks still remains. When the taper angle θ (see FIG. 1) at the edges of the source electrode and the drain electrode is reduced, the contact area between the organic semiconductor layer and the edges of the source electrode and the drain electrode is increased, and the adhesion is improved, but the source electrode and the drain electrode Since the tip of the drain electrode becomes thin and the adhesion between the gate insulating film and the source electrode and the drain electrode deteriorates, there is a drawback that interface peeling occurs when the substrate is bent and the characteristics deteriorate. ..

Japanese Unexamined Patent Publication No. 2008-66510

C. D. Dimitrakopoulo, P. et al. R. L. Malenfant, Adv. Mater. 2002, 14, 99 Proceedings of the National Academia of Sciences of the United States of America Vol. 15 No. 13, 4976 (2008) Applied Physics Letters 95, 253302 (2009)

INDUSTRIAL APPLICABILITY In a thin film transistor element using an organic semiconductor, the present invention prevents step breakage and interfacial peeling by improving the adhesion of at least the edge portion of the source electrode and drain electrode on the channel side to the organic semiconductor layer and the gate insulating layer. It is an object of the present invention to provide an organic semiconductor thin film transistor element capable of the above.

As a means for solving the above problems, the invention according to claim 1 of the present invention has a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and an organic semiconductor layer in this order on an insulating substrate. In the provided organic semiconductor thin film element, the surface surface of both the source electrode and the drain electrode is increased on the side surface and at least a part of the upper surface where the electrodes are in contact with the organic semiconductor layer at the opposite end. It has a structure that enhances the adhesion with the semiconductor layer.
The organic semiconductor thin film transistor element is characterized in that the structure is a tapered portion formed in a stepped shape on the side surface and has a concave-convex shape formed on the upper surface.

The invention according to claim 2 is the organic semiconductor thin film transistor element according to claim 1, wherein the source electrode and the drain electrode are made of one or more metals.

The invention according to claim 3 is the organic semiconductor thin film transistor element according to claim 1 or 2, wherein the metal constituting the source electrode and the drain electrode is silver.

The invention according to claim 4 is the organic semiconductor thin film transistor element according to any one of claims 1 to 3, wherein the number of steps of the tapered portion formed in a stepped shape is two or more. ..

The organic according to any one of claims 1 to 4, wherein the invention according to claim 5 has a taper angle θ of the tapered portion formed in a stepped shape of 32 ° or more and 57 ° or less. It is a semiconductor thin film transistor element.

The invention according to claim 6 is characterized in that the riser portion, which is the height of one step of the tapered portion formed in the stepped shape, is 0.01 to 0.1 μm. The organic semiconductor thin film transistor element according to any one of 0 to 5.

The invention according to claim 7 is characterized in that the tread portion, which is the depth of one step of the tapered portion formed in the stepped shape, is 0.01 to 0.1 μm. The organic semiconductor thin film transistor element according to any one of 6.

The invention according to claim 8 is characterized in that the mountain step portion, which is the length of the convex portion having a concave-convex shape formed on the upper surface, is 0.05 to 0.2 μm. 7. The organic semiconductor thin film transistor element according to 7.

Further, in the invention according to claim 9, the height step portion, which is the size of the step between the bottom surface of the concave-convex-shaped concave portion formed on the upper surface and the upper surface of the convex portion, is 0.01 to 0.1 μm. The organic semiconductor thin film transistor element according to claim 1 to 8.

The invention according to claim 10 is characterized in that the valley step portion, which is the length of the concave-convex-shaped concave portion formed on the upper surface, is 0.05 to 0.2 μm. The organic semiconductor thin film transistor element according to the above.

The invention according to claim 11 is the organic semiconductor thin film transistor element according to any one of claims 1 to 10, wherein the total film thickness of the structure is 0.1 to 0.5 μm. ..

According to the organic semiconductor thin film element of the present invention, in an organic semiconductor thin film element provided with a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and an organic semiconductor layer in this order on an insulating substrate, the source electrode A structure in which both electrodes of the drain electrode and the drain electrode are in contact with the organic semiconductor layer at the opposite end, and the adhesion to the organic semiconductor layer is enhanced by increasing the surface area of the side surface and at least a part of the upper surface. Is provided. The structure is provided with a stepped structure on the side surface and a concavo-convex structure on the upper surface at the ends of the source electrode and the drain electrode. Therefore, the adhesion between the source electrode and the drain electrode and the organic semiconductor layer becomes strong, and interface peeling or step breakage with the organic semiconductor layer occurs at the end on the side where both the source electrode and the drain electrode face each other. It disappears. As a result, it is possible to avoid the problem that the connection resistance between the organic semiconductor layer and the source electrode and the drain electrode does not increase and the on-current of the organic semiconductor thin film transistor element decreases.

The schematic cross-sectional view which shows the cross-sectional structure of an example of the organic semiconductor thin film transistor element of this invention. In the organic semiconductor thin film device of the present invention, by increasing the surface area of both the source electrode and the drain electrode on the side surface and at least a part of the upper surface where the electrodes are in contact with the organic semiconductor layer at the opposite end. The schematic cross-sectional view which illustrates the shape of the structure which enhances the adhesion with an organic semiconductor layer. The graph which shows an example of the Ids-Vgs characteristic of the organic semiconductor thin film transistor element of this invention. The schematic sectional view which shows an example of the sectional structure of the conventional organic semiconductor thin film transistor element. The graph which shows an example of the Ids-Vgs characteristic of the conventional organic semiconductor thin film transistor element.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, the same components are designated by the same reference numerals, and duplicate description between the embodiments will be omitted.

<Organic thin film transistor element>
FIG. 1 shows an example of the organic thin film transistor element 1 of the present invention. The organic thin film transistor element 1 of the present invention is a thin film transistor element having a bottom gate-bottom contact structure in which a gate electrode 11, a gate insulating layer 12, a source electrode 13, a drain electrode 14, and an organic semiconductor layer 15 are provided in this order on an insulating substrate 10. is there.

The organic thin film transistor element 1 of the present invention increases the surface area of both the source electrode and the drain electrode on the side surface and at least a part of the upper surface where the electrodes are in contact with the organic semiconductor layer at the opposite end. It is provided with a structure that enhances the adhesion with the organic semiconductor layer.

These structures are tapered portions formed in a stepped shape on the side surface, and are characterized in that they have a concave-convex shape formed on the upper surface.

Further, the source electrode and the drain electrode may be made of one or more metals. The metal may be silver.

Further, the number of steps of the tapered portion formed in a stepped shape may be two or more.

Further, the taper angle θ of the tapered portion formed in a stepped shape may be 32 ° or more and 57 ° or less.

Further, the riser portion, which is the height of one step of the tapered portion formed in a stepped shape, may be 0.01 to 0.1 μm.

Further, the tread portion, which is the depth of one step of the tapered portion formed in a step shape, may be 0.01 to 0.1 μm.

Further, the mountain step portion, which is the length of the uneven convex portion formed on the upper surface, may be 0.05 to 0.2 μm.

Further, the valley step portion, which is the length of the concave-convex concave portion formed on the upper surface, may be 0.05 to 0.2 μm.

Further, the total film thickness of the structure may be 0.1 to 0.5 μm.

Next, the components of the organic semiconductor thin film transistor element 1 of the present invention will be described.

(Insulated substrate)
A resin substrate can be used as the insulating substrate 10. In the case of resin substrates, for example, polyimide, polymethylmethacrylate, polyacrylate, polycarbonate, polystyrene, polyethylene sulfate, polyether sulfone (PES), polyolefin, etc.
Polyethylene terephthalate, polyethylene naphthalate (PEN), cycloolefin polymer, polyether sulfene, triacetyl cellulose, polyvinyl fluoride film, ethylene-tetrafluoroethylene copolymer resin, glass fiber reinforced acrylic resin film, glass fiber reinforced polycarbonate, fluorine A system resin, a cyclic polyolefin resin, or the like can be used. These substrates can be used alone, or a composite substrate in which two or more types are laminated can be used.

(Gate electrode)
The gate electrode 11 is not particularly limited as long as it has conductivity that can induce carriers in the organic semiconductor layer 15 by applying a voltage. For example, low resistance metal materials such as Au, Pt, Ag, Al, Cu, Cr, and Mo can be preferably used. The thickness of the gate electrode is not limited, but is preferably in the range of 0.01 μm or more and 1 μm or less, and more preferably in the range of 0.1 μm or more and 0.5 μm or less.

The method for forming the gate electrode 11 is not limited as long as the gate electrode 11 can be formed, but for example, a vacuum vapor deposition method or a sputtering method can be preferably used as a thin film forming means. Further, as a means for obtaining a wiring pattern from the formed thin film, a photolithography method including a resist pattern forming step consisting of coating, exposure and development of a photosensitive resist and subsequent steps such as etching and peeling of the resist pattern is preferably used. can do.

(Gate insulating layer)
Examples of the gate insulating layer 12 include a polymer solution such as polyvinylphenol, polymethylmethacrylate, polyimide, polyvinyl alcohol, parylene, fluororesin, and epoxy resin, a solution in which particles such as alumina and silica gel are dispersed, or silicon oxide. , Silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, zirconium oxide, titanium oxide and other precursor solutions of inorganic materials can be used. By applying these solutions onto the insulating substrate 10 on which the gate electrode 11 is formed by using a spin coating method, a slit die coating method, or the like and firing the solution, the gate insulating layer 12 is placed on the gate electrode 11 on the insulating substrate 10. Can form the formed structure. Further, as a method for forming the gate insulating layer 12, various printing methods can be adopted.

(Source electrode and drain electrode)
The source electrode 13 can apply an electric field between the source electrode 13 and the drain electrode 14 to inject carriers into the organic semiconductor layer 15, and the drain electrode 14 of the present invention has an electric field between the source electrode 13 and the source electrode 13. Can be applied to allow carriers to flow from the organic semiconductor layer 15. The same source electrode 13 and drain electrode 14 can be adopted in the configuration, and are not limited as long as they have conductivity, but are low in Au, Pt, Ag, Al, Cu, Cr, Mo, etc. A material containing any one or more selected from the resistance metals can be preferably used. For example, from the relationship of the work function (the tendency of the contact resistance of the transistor with respect to the electrode firing temperature matches the tendency of the change of the work function, which is the minimum energy required to extract one electron in the substance to the outside). It is desirable that it is Ag. The thickness of the source electrode 13 and the drain electrode 14 is not limited, but is preferably in the range of, for example, 0.01 μm or more and 1 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. Is within the range of. The source electrode 13 and the drain electrode 14 are formed so as to overlap the gate electrode 11 via the gate insulating film 12. By doing so, the gate electrode 11 can be made to correspond to the entire channel region between the source electrode 13 and the drain electrode 14, and the carrier can be reliably induced in the organic semiconductor layer 15.

The method for forming the source electrode 13 and the drain electrode 14 is not limited as much as possible to form these electrodes, but a desirable step shape pattern 19 and an uppermost uneven pattern 20 are obtained at the end on the channel side. For this purpose, for example, the staircase shape pattern 19 at the end on the channel side can be formed by superimposing the staircases one by one by using a lift-off method using a photoresist and a vacuum deposition method or a sputtering method. .. On the other hand, the protrusion shape pattern 20 formed at the uppermost portion having a concave-convex shape can be formed by a lift-off method using a photoresist and a vacuum vapor deposition method.

(Organic semiconductor layer)
Materials for the organic semiconductor layer 15 include high molecular weight organic semiconductor materials such as polythiophene, fluorenbithiophene copolymers, and derivatives thereof, and low molecular weight organic semiconductors such as pentacene, tetracene, copper phthalocyanine, and derivatives thereof. Materials can be used. Further, carbon compounds such as carbon nanotubes and fullerenes, semiconductor nanoparticle dispersion liquids, and the like can also be used as materials for the organic semiconductor layer 15, but are not limited thereto. These organic semiconductor materials can be used as an ink-like solution or dispersion by dissolving or dispersing in an aromatic solvent such as toluene. Additives such as suitable dispersants and stabilizers may be added to the solvent.

The organic semiconductor layer 15 contains a compound that binds to a metal ion. For example, benzotrial-based or triazine-based compounds can be mentioned. The basic form of the benzotriazole system is benzotriazole represented by the chemical formula (1), and 1H-benzotriazole-1-methanol (chemical formula (2)), which is an adduct of methanol, and an alkyl group on the triazole side. Examples thereof include an adduct (chemical formula (3)) and an adduct having an alkyl group on the benzene side (chemical formula (4)).

ただし、化学式（３）〜（５）に於けるＲはアルキル基である。 The basic skeleton of triazine is represented by the chemical formula (5), and examples thereof include 2,4-diamino-6-vinyl-S-triazine represented by the chemical formula (6).

However, R in the chemical formulas (3) to (5) is an alkyl group.

As a method for forming the organic semiconductor layer 15, known printing methods and various coating methods such as gravure printing, offset printing, screen printing and an inkjet method can be used. In general, since the above-mentioned organic semiconductor has low solubility in a solvent, it is desirable to use flexographic printing, transfer printing, an inkjet method, or a dispenser suitable for printing a low-viscosity solution.

The staircase shape pattern 19 and the protrusion shape pattern 20 in FIG. 2 can be formed by using vacuum vapor deposition to form a metal thin film, repeatedly using a lift-off method using a photoresist, and superimposing steps one by one. it can. The number of stairs, the taper angle θ, the height of one step of the stairs (kick top 21), the depth of the steps of the stairs (tread portion 22), the mountain step portion 23 at the top, and the height step portion 24. And the valley step portion 25 can be adjusted by the total film thickness. The protrusion shape pattern 20 is formed over the overlapping portion 26 (see FIG. 1) of the source electrode, the drain electrode, and the gate electrode in order to obtain good Ids-Vgs characteristics.

The film thickness of the kick upper portion 21 is preferably 0.01 μm to 0.1 μm. Within this range, it is suitable as an electrode having a stepped tapered portion (staircase shape pattern 19). If it is thinner than 0.01 μm, it becomes difficult to produce a stepped tapered portion, and if it is thicker than 0.1 μm, the number of stairs is reduced and the possibility of step breakage increases.

The tread portion 22 (depth of the step of the stairs) is preferably 0.01 μm to 0.1 μm. Within this range, it is suitable as an electrode having a stepped tapered portion (staircase shape pattern 19). If it is out of this range, there is a high possibility that the adhesion to the organic semiconductor layer will deteriorate.

Further, the taper angle θ of the stepped tapered portion (staircase shape pattern 19) is preferably 32 ° to 57 °. Within this range, the adhesion to the organic semiconductor layer is good. If it is smaller than 32 °, it becomes difficult to produce a stepped tapered portion, and if it is larger than 57 °, there is a high possibility that the adhesion to the organic semiconductor layer is deteriorated.

The length in the direction in which the source electrode and the drain electrode of the mountain step portion 23 are aligned (hereinafter, also simply referred to as a length) is preferably 0.05 μm to 0.2 μm. Within this range, it is suitable as an electrode having a stepped portion having an uneven shape. If it is out of this range, there is a high possibility that the adhesion to the organic semiconductor layer will deteriorate.

The film thickness of the height step portion 24 is preferably 0.01 μm to 0.1 μm. Within this range, it is suitable as an electrode having a stepped portion having an uneven shape. If it is thinner than 0.01 μm, it becomes difficult to produce a stepped portion having an uneven shape. If it is thicker than 0.1 μm, step breakage and interfacial peeling are likely to occur, which is not preferable.

The length of the valley step portion 25 in the direction in which the source electrode and the drain electrode are aligned (hereinafter, also simply referred to as the length) is preferably 0.05 μm to 0.2 μm. Within this range, it is suitable as an electrode having a stepped portion having an uneven shape. If it is out of this range, there is a high possibility that the adhesion to the organic semiconductor layer will deteriorate.

Hereinafter, specific examples of the organic semiconductor thin film transistor element according to the present invention will be described. The present invention is not limited to each embodiment.
<Example>
In the example, the organic semiconductor thin film transistor element 1 as shown in FIG. 1 was manufactured.

First, a polyethylene naphthalate (PEN) film was prepared as the insulating substrate 10.
Next, a molybdenum thin film was formed on the gate electrode 11 by using a sputtering method.

Next, a pattern of a gate electrode 11 having a width of 100 μm and a length of 300 μm was formed on the molybdenum thin film by a photolithography method to prepare a gate electrode 11 having a film thickness of 100 nm.

Next, a solution containing polyvinylphenol to be the gate insulating layer 12 is applied onto the insulating substrate 10 including the gate electrode 11 by a flexographic printing method, baked at 180 ° C. for 1 hour, and then the gate insulating layer 12 having a thickness of 1 μm is applied. Obtained.

Subsequently, a source in which a stepped pattern portion 19 is provided on the gate insulating layer 12 by a lift-off method using Ag as an electrode material and vacuum vapor deposition so as to have the shape of the schematic cross-sectional view of FIG. The electrode 13 and the drain electrode 14 were formed. The shape of the stepped pattern portion 19 is
The lift-off method using the vacuum vapor deposition method is repeatedly used, and the stairs are superposed one step at a time, and the number of steps, the taper angle θ, the film thickness of one step (kick top 21), and the depth of the stairs (tread portion 22). ), The length of the uppermost mountain portion (mountain step portion 23), the film thickness of the height portion (height step portion 24), the length of the valley portion (valley step portion 25), and the total film thickness. And can be adjusted with. In the case of this embodiment, the number of stairs: 4 steps, the taper angle θ: 57 °, the film thickness of 1 step of the stairs (kick top 21): 20 nm, the step depth of the stairs (tread portion 22): 20 nm, the top Adjust so that the length of the mountain portion (mountain step portion 23): 50 nm, the film thickness of the height portion (height step portion 24): 20 nm, and the length of the valley portion (valley step portion 25): 50 nm. A source electrode 13 and a drain electrode 14 having a total film thickness of 100 nm were obtained.

Next, pentafluorothiophenol was immersed in a solution diluted to 1% by weight with isopropyl alcohol on the source electrode 13 and the drain electrode 14 for 30 minutes to form a self-assembled monolayer.

Finally, the benzotriazole compound is added to the semiconductor material (solid content) by weight in a solution prepared by dissolving 6,13-bis (triisopropylsilylethynyl) pentacene, which is an organic semiconductor material, with tetraline so as to be 2% by weight. The ink added so as to be 1.5: 1 is printed over the source electrode 13 and the drain electrode 14 using the letterpress printing method, dried at 100 ° C. for 60 minutes, and is an organic semiconductor having a film thickness of 30 nm. Layer 15 was formed.

The channel length of the transistor produced as described above was 10 μm, and the channel width was 200 μm.
Current of the organic semiconductor TFT device produced (I _ds) - shows the results of measuring the voltage (V _gs) characteristics in FIG. Here, I _ds is the current between the source electrode and the drain electrode, and V _gs is the voltage applied to the gate electrode with the source electrode as a reference. From this graph, the ON current was about ^10-6 A (ampere) when V _gs, which is the voltage for driving the display, was -20 V.

<Comparison example>
As a comparative example, an organic semiconductor thin film transistor element as shown in FIG. 4 was manufactured.
As a manufacturing method, among the manufacturing methods shown in Examples, except that the formation of the source electrode 13 and the drain electrode 14 to be formed on the gate insulating layer 12 is patterned by a photolithography method after forming Ag. It was prepared under the same manufacturing method and the same conditions. In this case, the cross-sectional shape of the portion of the source electrode 13 and the drain electrode 14 near the insulating substrate 10 at the pattern end is a steep cross-sectional shape substantially orthogonal to the surface, and the cross section of the portion near the surface of the electrode at the pattern end. However, the cross-sectional shape was almost orthogonal to the surface of the electrode. Therefore, as schematically shown in FIG. 4, at the end of the source electrode 13 and the drain electrode 14 on the channel side of the organic semiconductor thin film transistor element 18, a step break 16 or an interface is formed at a portion where the organic semiconductor layer 15 is thinned. Peeling 17 occurred.

Current of the organic semiconductor thin-film transistor element 18 _{(I ds)} - shows the results of measuring the voltage _{(V gs)} characteristics in FIG. From this graph, the on-current was about ^10-7 A (ampere) when V _gs, which is the voltage for driving the display, was -20 V.

From the above results, it was found that the on-current of the organic semiconductor thin film transistor element 1 of the present invention can be obtained to be nearly an order of magnitude larger than that of the organic semiconductor thin film transistor element 18 manufactured by the conventional method. This is because, in the organic semiconductor thin film element 1 of the present invention, the organic semiconductor layer 15 does not cause step breakage or interfacial peeling at the ends of the source electrode 13 and the drain electrode 14, so that the organic semiconductor layer 15, the source electrode 13 and the drain This is considered to be because the connection resistance with the electrode 14 becomes small.

1 Organic semiconductor thin film transistor element 10 Insulated substrate 11 Gate electrode 12 Gate insulating layer 13 Source electrode 14 Drain electrode 15 Organic semiconductor layer 16 Step break 17 Interfacial peeling 18 Organic semiconductor thin film transistor element 19 Step-shaped pattern (stepped taper)
20 Projection shape pattern (unevenly shaped stepped portion)
21 Kicking top 22 Tread 23 Mountain step 24 Height step 25 Valley step 26 Overlapping part with gate electrode θ Taper angle

Claims (11)

In an organic semiconductor thin film element having a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and an organic semiconductor layer in this order on an insulating substrate, the side where both the source electrode and the drain electrode face each other. A structure is provided on the side surface and at least a part of the upper surface, which are in contact with the organic semiconductor layer at the end of the electrode, to increase the adhesion to the organic semiconductor layer by increasing their surface areas.
An organic semiconductor thin film transistor element characterized in that the structure is a tapered portion formed in a stepped shape on the side surface and has a concave-convex shape formed on the upper surface. The organic semiconductor thin film transistor element according to claim 1, wherein the source electrode and the drain electrode are made of one or more metals. The organic semiconductor thin film transistor element according to claim 1 or 2, wherein the metal constituting the source electrode and the drain electrode is silver. The organic semiconductor thin film transistor element according to any one of claims 1 to 3, wherein the number of steps of the tapered portion formed in a stepped shape is two or more. The organic semiconductor thin film transistor element according to any one of claims 1 to 4, wherein the taper angle θ of the tapered portion formed in a stepped shape is 32 ° or more and 57 ° or less. The organic semiconductor thin film transistor according to any one of claims 1 to 5, wherein the riser portion, which is the height of one step of the tapered portion formed in a stepped shape, is 0.01 to 0.1 μm. element. The organic semiconductor thin film transistor element according to any one of claims 1 to 6, wherein the tread portion, which is the depth of one step of the tapered portion formed in the stepped shape, is 0.01 to 0.1 μm. .. The organic semiconductor thin film transistor element according to claim 1, wherein the mountain step portion, which is the length of the concave-convex-shaped convex portion formed on the upper surface, is 0.05 to 0.2 μm. Claims 1 to 8, wherein the height step portion, which is the size of the step between the bottom surface of the concave-convex concave portion formed on the upper surface and the upper surface of the convex portion, is 0.01 to 0.1 μm. The organic semiconductor thin film transistor element described. The organic semiconductor thin film transistor element according to claim 1, wherein the valley step portion, which is the length of the concave-convex-shaped concave portion formed on the upper surface, is 0.05 to 0.2 μm. The organic semiconductor thin film transistor element according to any one of claims 1 to 10, wherein the total film thickness of the structure is 0.1 to 0.5 μm.

Images