JP2017195315A - Thin film transistor - Google Patents

Abstract

An object of the present invention is to provide a thin film transistor having high adhesion between a gate insulating layer and a gate electrode and excellent long-term stability. A thin film transistor is a bottom gate type thin film transistor having at least a gate electrode, a gate insulating layer, a source electrode and a drain electrode, and an organic semiconductor layer on an insulating substrate, wherein the gate electrode is made of at least one kind of metal, The gate insulating layer contains a compound that bonds with the metal forming the gate electrode. [Selection drawing] Fig. 1

Description

  The present invention relates to a thin film transistor.

  Currently, a general flat and thin image display device is driven by an active matrix composed of a thin film transistor in which a semiconductor layer is formed using amorphous silicon or polycrystalline silicon.

  On the other hand, in recent years, attempts have been made to use a resin substrate instead of a glass substrate in order to further reduce the thickness, weight, and damage resistance of a flat and thin image display device.

  However, the manufacture of the above-described thin film transistor using silicon requires a relatively high temperature thermal process and is generally difficult to form directly on a resin substrate having low heat resistance.

  Therefore, development of a thin film transistor (organic thin film transistor) using an organic semiconductor that can be formed at a low temperature has been actively conducted.

  Further, the organic semiconductor has an advantage that it can be patterned by a printing method. In the organic thin film transistor, not only a semiconductor layer but also an electrode and a gate insulating layer can be formed by printing by selecting materials that can be formed by a printing method.

  By using the printing method, a significant reduction in manufacturing cost is expected as compared with silicon thin film transistors manufactured by vacuum film formation and photolithography.

  In general, the structure of an organic thin film transistor manufactured by a printing method is not a top gate type but a bottom gate type. In the case of the top gate type, a gate insulating layer is formed on the organic semiconductor. At that time, there is a possibility that the organic semiconductor is damaged by the solvent contained in the material of the gate insulating layer or the heating during firing. This is because it is expensive.

  In addition, Ag is generally used as a gate electrode material when forming a gate electrode by a printing method (Patent Document 1).

  However, when the organic insulating layer is formed on the gate electrode, there is a problem that adhesion between the gate insulating layer and the gate electrode is low. Examples of a method for improving the adhesion between the gate electrode and the gate insulating layer include ozone cleaning and oxygen plasma treatment of the electrode surface (Non-Patent Document 1). In this method, Ag is oxidized, and the gate electrode is used as a gate electrode. Electrical characteristics will deteriorate.

International Publication No. 2010/113931

Satoshi Hamada, “TFT manufacturing technology in liquid crystal displays”, Sharp Technical Report, November 2007, No. 96, p. 30-33

  In the case where the adhesion between the gate insulating layer and the gate electrode is low, peeling between the gate insulating layer and the gate electrode may occur when the thin film transistor is repeatedly driven, and the thin film transistor may not operate. For example, when an organic thin film transistor is formed on a flexible substrate and a flexible device using the organic thin film transistor is manufactured, peeling between the gate insulating layer and the gate electrode may occur due to bending during use, and the thin film transistor may not operate. There is. That is, when the adhesion between the gate insulating layer and the gate electrode is low, it is difficult to ensure long-term stability of the thin film transistor and the application using the thin film transistor.

  In view of the above, an object of the present invention is to provide a thin film transistor having high adhesion between a gate insulating layer and a gate electrode and excellent long-term stability.

  One aspect of the present invention for solving the above problems is a bottom-gate thin film transistor having at least a gate electrode, a gate insulating layer, a source / drain electrode, and an organic semiconductor layer on an insulating substrate, and the gate electrode is at least one or more types. The gate insulating layer contains a compound that binds to the metal constituting the gate electrode.

  Further, the metal constituting the gate electrode may contain silver.

  Further, the compound bonded to the metal constituting the gate electrode contained in the gate insulating layer may be benzotrial, triazine, or benzothiadiazole.

  The insulating substrate may be a resin substrate.

  According to the present invention, it is possible to provide a thin film transistor having high adhesion between a gate insulating layer and a gate electrode and excellent long-term stability.

Sectional drawing of the thin-film transistor which concerns on one Embodiment of this invention Cross-sectional view of a conventional thin film transistor

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, the same or corresponding components are denoted by the same reference numerals, and redundant description among the embodiments is omitted.

  FIG. 1 shows a cross-sectional view of a thin film transistor 100 according to an embodiment of the present invention. The thin film transistor 100 is a bottom gate-bottom contact thin film transistor including a gate electrode 11, a gate insulating layer 12, a source electrode 13 and a drain electrode 14, and a semiconductor layer 15 on an insulating substrate 10. However, the thin film transistor may have another structure such as a bottom gate-top contact structure.

  A glass substrate or a resin substrate can be used as the insulating substrate 10. In particular, when forming a flexible device taking advantage of the organic thin film transistor, it is preferable to use a resin substrate. Examples of the material of the resin substrate include polyimide, polymethyl methacrylate, polyacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone (PES), polyolefin, polyethylene terephthalate, polyethylene naphthalate (PEN), cycloolefin polymer, and polyether. Sulfen, triacetyl cellulose, polyvinyl fluoride film, ethylene-tetrafluoroethylene copolymer resin, glass fiber reinforced acrylic resin film, glass fiber reinforced polycarbonate, fluorine resin, cyclic polyolefin resin, and the like can be used. These substrates can be used alone, or a composite substrate in which two or more kinds are laminated can be used.

  The gate electrode 11 can be formed by applying a low resistance metal material such as Ag, Cu, Au or the like in the form of an ink or paste by screen printing, transfer printing, letterpress printing, an ink jet method, or the like, and baking it. it can. In particular, Ag in the form of ink or paste is preferred from the viewpoint of low resistance and low cost. The gate electrode 11 can also be obtained by patterning a metal material such as Al, Mo, Ag, etc. formed by a vacuum film formation method such as sputtering using a photolithography method or the like, but is not limited thereto. It is not a thing.

  The gate insulating layer 12 is made of, for example, a polymer solution such as polyvinylphenol, polymethyl methacrylate, polyimide, polyvinyl alcohol, parylene, fluororesin, epoxy resin, a solution in which particles such as alumina and silica gel are dispersed, silicon oxide, A precursor solution of an inorganic material such as silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, zirconium oxide, or titanium oxide is applied using a spin coating method, a slit die coating method, or the like, and baked. Can be formed.

  The gate insulating layer 12 contains a compound 16 that binds to a metal. Examples of the compound 16 include benzotrial, triazine, or benzothiadiazole compounds.

  The benzotriazole type is based on benzotrial represented by (Chemical Formula 1), and in addition, 1H-benzotriazole-1-methanol (Chemical Formula 2), which is an adduct of methanol, and an alkyl group added to the triazole side (Chemical formula 3) and those obtained by adding an alkyl group to the benzene side (Chemical formula 4).

  The basic skeleton of triazine is represented by (Chemical Formula 5), and examples thereof include 2,4-diamino-6-vinyl-S-triazine represented by (Chemical Formula 6).

  The basic skeleton of benzothiadiazole is represented by (Chemical Formula 7), and examples thereof include 4-amino-2, 1,3-benzothiadiazole and the like represented by (Chemical Formula 8).

  The source electrode 13 and the drain electrode 14 are obtained by applying a low resistance metal material such as Ag, Cu, Au or the like in an ink form or a paste form by screen printing, transfer printing, letterpress printing, an ink jet method, and the like, followed by firing. Although it can be formed, it is particularly preferable to use Ag in the form of an ink or paste from the viewpoint of low resistance and low cost. The source electrode 13 and the drain electrode 14 can also be obtained by patterning a metal material such as Al, Mo, Ag, etc. formed by a vacuum film formation method such as a sputtering method by a photolithography method, but is not limited thereto. Is not to be done.

  Examples of the material of the organic semiconductor layer 15 include high molecular organic semiconductor materials such as polythiophene, fluorenebithiophene copolymers, and derivatives thereof, and low molecular organic semiconductors such as pentacene, tetracene, copper phthalocyanine, and derivatives thereof. Materials can be used. Carbon compounds such as carbon nanotubes and fullerenes can also be used as the material for the semiconductor layer, but are not limited thereto.

  The organic semiconductor layer 15 is formed by dissolving or dispersing the above-described organic semiconductor material in an aromatic solvent such as toluene to form an ink-like solution or dispersion using gravure printing, offset printing, screen printing, an inkjet method, or the like. can do. You may add additives, such as a suitable dispersing agent and a stabilizer, to a solvent. The organic semiconductor layer 15 can also be formed by using a method in which an organic semiconductor material is formed on the entire surface by a vacuum film formation method such as an evaporation method and then patterned by resist printing or the like, or a vacuum can be formed using a metal mask. A pattern can be formed by forming a film, but is not limited thereto.

  Specific examples and comparative examples of the thin film transistor according to the present invention will be described below. Note that the present invention is not limited to each embodiment.

Example 1
In Example 1, a benzotriazole-based compound was included in the gate insulating layer 12 to produce a thin film transistor 100 element as shown in FIG.

  First, a pattern of nano silver ink [manufactured by Harima Kasei] is formed on a polyethylene naphthalate (PEN) film [manufactured by Teijin DuPont] to be an insulating substrate 10 using a transfer method and baked at 180 ° C. for 1 hour. Thus, a gate electrode 11 having a thickness of 100 nm was produced. Next, a resin containing a benzotrial compound to be the gate insulating layer 12 is formed on the insulating substrate 10 including the gate electrode 11 by spin coating, and baked at 180 ° C. for 1 hour. A gate insulating layer 12 was obtained. Subsequently, a pattern of nano silver ink [manufactured by Harima Chemicals] is formed on the gate insulating layer 12 by using a transfer method, and is baked at 180 ° C. for 1 hour, so that the source electrode 13 and the drain electrode 14 having a film thickness of 100 nm are formed. Got. Next, the source electrode 13 and the drain electrode 14 were immersed in a solution of pentafluorothiophenol diluted to 1 wt% with isopropyl alcohol for 30 minutes to form a self-assembled monolayer. Next, a solution prepared by dissolving 6,13-bis (triisopropylsilylethynyl) pentacene [manufactured by Ardrich], which is an organic semiconductor material, with tetralin so as to be 2 wt% is obtained by using a relief printing method to form the source electrode 13 and the drain. It printed between the source-drain electrodes so that a part on electrode 14 might be covered, and it dried at 100 degreeC for 60 minutes, and formed the organic-semiconductor layer 15 with a film thickness of 50 nm. The manufactured thin film transistor 100 has a channel length of 10 μm and a channel width of 180 μm.

The device characteristics of the thin film transistor 100 manufactured as described above immediately after the manufacture were an on-current of 2.3E-6A and a mobility of 0.3 cm ² / Vs. The device characteristics after the bending test was performed 10,000 times with the curvature radius of 10 mm for the manufactured thin film transistor 100 were 2.3E-6A and the mobility was 0.3 cm ² / Vs, and the device characteristics fluctuated before and after the bending test. Was 10% or less.

(Example 2)
In Example 2, the gate insulating layer 12 was made to contain a triazine compound, and a thin film transistor 100 element as shown in FIG. 1 was produced.

  First, a pattern of nano silver ink [manufactured by Harima Kasei] is formed on a polyethylene naphthalate (PEN) film [manufactured by Teijin DuPont] to be an insulating substrate 10 using a transfer method and baked at 180 ° C. for 1 hour. Thus, a gate electrode 11 having a thickness of 100 nm was produced. Next, a resin containing a triazine compound to be the gate insulating layer 12 is formed on the insulating substrate 10 including the gate electrode 11 by a spin coating method, baked at 200 ° C. for 1 hour, and then a gate having a thickness of 1 μm. An insulating layer 12 was obtained. Subsequently, a pattern of nano silver ink [manufactured by Harima Chemicals] is formed on the gate insulating layer 12 by using a transfer method, and is baked at 180 ° C. for 1 hour, so that the source electrode 13 and the drain electrode 14 having a film thickness of 100 nm are formed. Got. Next, the source electrode 13 and the drain electrode 14 were immersed in a solution of pentafluorothiophenol diluted to 1 wt% with isopropyl alcohol for 30 minutes to form a self-assembled monolayer. Next, a solution prepared by dissolving 6,13-bis (triisopropylsilylethynyl) pentacene [manufactured by Ardrich], which is an organic semiconductor material, with tetralin so as to be 2 wt% is obtained by using a relief printing method to form the source electrode 13 and the drain. It printed between the source-drain electrodes so that a part on electrode 14 might be covered, and it dried at 100 degreeC for 60 minutes, and formed the organic-semiconductor layer 15 with a film thickness of 50 nm. The manufactured thin film transistor 100 has a channel length of 10 μm and a channel width of 180 μm.

The device characteristics of the thin film transistor 100 manufactured as described above immediately after the manufacture were an on-current of 2.2E-6A and a mobility of 0.3 cm ² / Vs. The device characteristics after the bending test was performed 10,000 times with the curvature radius of 10 mm for the manufactured thin film transistor 100 were 2.1E-6A and the mobility was 0.3 cm ² / Vs, and the device characteristics fluctuated before and after the bending test. Was 10% or less.

(Example 3)
In Example 3, the gate insulating layer 12 contained a benzothiadiazole-based compound to produce a thin film transistor element as shown in FIG.

  First, a pattern of nano silver ink [manufactured by Harima Kasei] is formed on a polyethylene naphthalate (PEN) film [manufactured by Teijin DuPont] to be an insulating substrate 10 using a transfer method and baked at 180 ° C. for 1 hour. Thus, a gate electrode 11 having a thickness of 100 nm was produced. Next, a resin containing a benzothiadiazole-based compound to be the gate insulating layer 12 is formed on the insulating substrate 10 including the gate electrode 11 by spin coating, and baked at 180 ° C. for 1 hour. A gate insulating layer 12 was obtained. Subsequently, a pattern of nano silver ink [manufactured by Harima Chemicals] is formed on the gate insulating layer 12 by using a transfer method, and baked at 180 ° C. for 1 hour, so that the source electrode 13 and the drain electrode 14 having a film thickness of 100 nm are formed. Got. Next, the source electrode 13 and the drain electrode 14 were immersed in a solution of pentafluorothiophenol diluted to 1 wt% with isopropyl alcohol for 30 minutes to form a self-assembled monolayer. Next, a solution prepared by dissolving 6,13-bis (triisopropylsilylethynyl) pentacene [manufactured by Ardrich], which is an organic semiconductor material, with tetralin so as to be 2 wt% is obtained by using a relief printing method to form the source electrode 13 and the drain. It printed between the source-drain electrodes so that a part on electrode 14 might be covered, and it dried at 100 degreeC for 60 minutes, and formed the organic-semiconductor layer 15 with a film thickness of 50 nm. The manufactured thin film transistor 100 has a channel length of 10 μm and a channel width of 180 μm.

The device characteristics of the thin film transistor 100 manufactured as described above immediately after the manufacture were an on-current of 2.3E-6A and a mobility of 0.3 cm ² / Vs. The device characteristics after the bending test is 10,000 times with the curvature radius of 10 mm for the manufactured thin film transistor are 2.4E-6A and the mobility is 0.3 cm ² / Vs. It was 10% or less.

(Comparative Example 1)
In the comparative example, the gate insulating layer 12 did not contain a benzotriazole-based compound, a triazine-based compound, or a benzothiadiazole-based compound, and a thin film transistor element according to the prior art as shown in FIG. 2 was produced.

  First, a pattern of nano silver ink [manufactured by Harima Kasei] is formed on a polyethylene naphthalate (PEN) film [manufactured by Teijin DuPont] to be an insulating substrate 10 using a transfer method and baked at 180 ° C. for 1 hour. Thus, a gate electrode 11 having a thickness of 100 nm was produced. Next, a polyimide [manufactured by Mitsubishi Gas Chemical Co., Ltd.] to be the gate insulating layer 12 is formed on the insulating substrate 10 including the gate electrode 11 by spin coating, fired at 200 ° C. for 1 hour, and then gate insulating with a film thickness of 1 μm. Layer 12 was obtained. Subsequently, a pattern of nano silver ink [manufactured by Harima Chemicals] is formed on the gate insulating layer 12 by using a transfer method, and is baked at 180 ° C. for 1 hour, so that the source electrode 13 and the drain electrode 14 having a film thickness of 100 nm are formed. Got. Next, the source electrode 13 and the drain electrode 14 were immersed in a solution of pentafluorothiophenol diluted to 1 wt% with isopropyl alcohol for 30 minutes to form a self-assembled monolayer. Next, a solution prepared by dissolving 6,13-bis (triisopropylsilylethynyl) pentacene [manufactured by Ardrich], which is an organic semiconductor material, with tetralin so as to be 2 wt% is obtained by using a relief printing method to form the source electrode 13 and the drain. It printed between the source-drain electrodes so that a part on electrode 14 might be covered, and it dried at 100 degreeC for 60 minutes, and formed the organic-semiconductor layer 15 with a film thickness of 50 nm. The manufactured thin film transistor has a channel length of 10 μm and a channel width of 180 μm.

The device characteristics immediately after the fabrication of the thin film transistor fabricated as described above were an on-current of 2.1E-6A and a mobility of 0.3 cm ² / Vs. The device characteristics after the bending test was performed 10,000 times with a curvature radius of 10 mm for the manufactured thin film transistor were 2.1E-7A, the mobility was 0.02 cm ² / Vs, and the device characteristics were 10% or more before and after the bending test. (90%) decrease. As a result of microscopic observation of the element, a part of the gate insulating layer was peeled off from the gate electrode.

  From the above evaluation results, it is possible to improve the adhesion between the gate insulating layer and the gate electrode and to improve the long-term stability by configuring the gate insulating layer to contain a compound that binds to the metal constituting the gate electrode. It was confirmed that we could provide.

  As described above, according to the present invention, the adhesion between the gate insulating layer and the gate electrode can be improved by combining the compound contained in the gate insulating layer with the gate electrode.

  In addition, when the main metal of the gate electrode is silver, high conductivity can be obtained. Further, if silver nano ink or the like is used as a raw material, a high-definition gate electrode pattern can be formed at low cost by using a printing method.

  In addition, by containing a benzotriazole-based, triazine-based, or benzothiadiazole-based compound in the gate insulating layer, the bond between the compound and the gate electrode is strengthened, and the adhesion between the gate insulating layer and the gate electrode is increased, so that long-term stability is achieved. A thin film transistor having excellent properties can be formed.

  In addition, when the insulating substrate is a resin substrate, a flexible device with high adhesion between the gate insulating layer and the gate electrode can be manufactured.

  The present invention can be used as a switching element such as a display, flexible electronic paper, and pressure sensor.

DESCRIPTION OF SYMBOLS 10 Insulating substrate 11 Gate electrode 12 Gate insulating layer 13 Source electrode 14 Drain electrode 15 Semiconductor layer 16 Compound couple | bonded with a metal 100 Thin film transistor

Claims (4)

  A bottom-gate thin film transistor having at least a gate electrode, a gate insulating layer, a source electrode and a drain electrode, and an organic semiconductor layer on an insulating substrate, wherein the gate electrode is made of at least one metal, and the gate insulating layer is A thin film transistor containing a compound that binds to a metal constituting a gate electrode.   The thin film transistor according to claim 1, wherein the metal constituting the gate electrode contains silver.   3. The thin film transistor according to claim 1, wherein the compound that binds to the metal constituting the gate electrode contained in the gate insulating layer is a benzotriazole-based, triazine-based, or benzothiadiazole-based compound.   The thin film transistor according to any one of claims 1 to 3, wherein the insulating substrate is a resin substrate.