JP2003347552A - Organic transistor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic transistor whose leak current is reduced and which is superior in an ON/OFF ratio and to provide a manufacturing method of the transistor. <P>SOLUTION: The organic transistor uses an organic semiconductor in which a low molecular weight component whose molecular weight is 2,000 or below is not more than 0.5 mass %. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic transistor containing an organic semiconductor and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the spread of information terminals, there is an increasing need for flat panel displays as displays for computers. In addition, with the progress of computerization, information provided in the form of paper has been increasingly digitized, and the number of opportunities to provide the information has increased, and electronic paper or digital media has become a thin, light, and portable mobile display medium. The need for paper is also growing.

In general, in a flat panel display device, a display medium is formed by using elements utilizing liquid crystal, organic electroluminescence, electrophoresis and the like. Further, in such display media, in order to ensure uniformity of screen luminance and screen rewriting speed, a technique using an active driving element (TFT element) as an image driving element has become mainstream. For example, in a general computer display, these TFT elements are formed on a glass substrate, and a liquid crystal, an organic electroluminescence element, and the like are sealed.

Here, semiconductors such as a-Si (amorphous silicon) and p-Si (polysilicon) can be mainly used for the TFT element, and these Si semiconductors (and a metal film if necessary) are multi-layered. Then, a TFT element is manufactured by sequentially forming a source, a drain, and a gate electrode on a substrate. The production of such a TFT element usually requires sputtering and other vacuum-based production processes.

However, in the manufacture of such a TFT element, each layer has to be formed by repeating the manufacturing process of a vacuum system including a vacuum chamber many times, which leads to an increase in equipment cost and cost.
The running cost was very enormous. For example, in the case of a TFT device, it is usually necessary to repeat processes such as vacuum deposition, doping, photolithography, and development many times to form each layer, and the device is formed on a substrate through dozens of processes. ing. A plurality of semiconductor layers such as a p-type semiconductor layer and an n-type semiconductor layer are stacked on a semiconductor portion which is essential for a switching operation. In such a conventional manufacturing method based on a vacuum-based manufacturing process using a Si semiconductor, it is easy to change equipment, such as a need for a large design change of a manufacturing apparatus such as a vacuum chamber in response to a need for a large display screen. is not.

[0006] Further, since formation of such a conventional TFT element using a Si material involves a high-temperature process, there is an additional restriction that the substrate material is a material that can withstand the process temperature. For this reason, glass must be used in practice, and when a thin display such as the electronic paper or digital paper described above is constructed using such a conventionally known TFT element, the display is heavy and flexible. Chipped, resulting in a product that may be broken by the impact of falling. These characteristics resulting from forming TFT elements on a glass substrate are undesirable in satisfying the need for a portable, thin display with the progress of computerization.

On the other hand, in recent years, with the research on organic semiconductors, it has been considered to incorporate organic materials into such circuits instead of Si materials. Organic semiconductors are considered to be capable of vacuum or low pressure deposition at relatively low temperatures,
It is considered that there is a possibility that a semiconductor that can be made into a solution can be obtained by appropriately improving the molecular structure, and production by a printing method including an inkjet method by making an organic semiconductor solution into an ink can also be considered. It has been considered impossible to manufacture these low-temperature processes using conventional Si-based semiconductor materials. However, there is a possibility that TFT devices using organic semiconductors can do so, and the above-mentioned restrictions on substrate heat resistance are relaxed. Thus, there is a possibility that a TFT element can be formed on a transparent resin substrate. TFT on transparent resin substrate
If an element can be formed and a display material can be driven by the TFT element, the display can be made lighter, more flexible, and not broken (or very hard to break) even when dropped. Will.

However, many organic semiconductors do not have sufficient charge carrier mobilities and exhibit anisotropy in conductivity, so that it is necessary to orient organic molecules on a substrate. If the alignment continuity is not ensured, a large barrier is generated in the charge transport in the discontinuous portion, so that the charge transport property is greatly impaired. Therefore, problems in the production process such as a special orientation technology for maintaining the orientation and the uniformity as a material, and the repetition of a vacuum production process have not been solved. In recent years, organic transistor devices using a polymer material such as polythiophene or poly-p-thienylenevinylene for the active layer have been studied to solve the problems in the manufacturing process, but the charge mobility is low. However, there is a problem that the leakage current is large, the ON / OFF ratio of the switching current is low, and the like.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic transistor having a reduced leakage current and an excellent ON / OFF ratio, and a method for manufacturing the same.

[0010]

The above object of the present invention is achieved by the following means.

1. An organic transistor comprising an organic semiconductor having a low molecular weight component having a molecular weight of 2000 or less and 0.5 mass% or less.

2. It comprises a source and drain electrodes provided on a support, an organic semiconductor layer formed in contact with the electrodes, a gate insulating layer formed in contact with the organic semiconductor layers, and a gate electrode formed on the gate insulating layer. In an organic transistor, a gate insulating layer is made of a metal oxide or a nitride formed by an atmospheric pressure plasma method, and an organic semiconductor layer between a source and a drain electrode has a molecular weight of 2,000.
An organic transistor comprising an organic semiconductor having the following low molecular weight component of 0.5% by mass or less.

3. It comprises a source and drain electrodes provided on a support, an organic semiconductor layer formed in contact with the electrodes, a gate insulating layer formed in contact with the organic semiconductor layers, and a gate electrode formed on the gate insulating layer. In an organic transistor, the gate insulating layer is selected from at least one of silicon oxide, silicon nitride, aluminum oxide, tantalum oxide, and titanium oxide, and the organic semiconductor layer between the source and drain electrodes has a low molecular weight of 2000 or less. An organic transistor comprising an organic semiconductor containing 0.5% by mass or less of a component.

4. It comprises a source and drain electrodes provided on a support, an organic semiconductor layer formed in contact with the electrodes, a gate insulating layer formed in contact with the organic semiconductor layers, and a gate electrode formed on the gate insulating layer. In an organic transistor, an organic semiconductor layer is formed in contact with a layer made of any one of polyimide, polyamide, polyester, and polyacrylate, and an organic semiconductor layer between a source and a drain electrode has a low molecular weight component having a molecular weight of 2000 or less of 0.2. An organic transistor comprising an organic semiconductor in an amount of 5% by mass or less.

[0015] 5. A method for producing an organic transistor, comprising using an organic semiconductor purified by ultrafiltration to have a low molecular weight component having a molecular weight of 2000 or less to 0.5 mass% or less.

6. A method for producing an organic transistor, comprising using an organic semiconductor purified by microfiltration so that a low molecular weight component having a molecular weight of 2,000 or less is reduced to 0.5% by mass or less.

Hereinafter, the present invention will be described in detail. Heretofore, the adverse effects of low molecular weight components in organic semiconductors have not been sufficiently recognized, and thus no method for removing them has been disclosed.
The present inventors have conducted intensive studies and found that the main cause of the above problem is a low molecular weight component in an organic semiconductor,
This has led to the present invention. In addition, the removal method was examined and a useful method was found.

As a result of the study by the present inventors, if the low molecular weight component having a molecular weight of 2000 or less exceeds 0.5% by mass among the low molecular weight components remaining in the organic semiconductor, the above problem is likely to occur. It is necessary to remove low molecular weight components having a molecular weight of 2000 or less to 0.5% by mass or less. More preferably, the content is 0.4% by mass or less.

In the present invention, a π-conjugated polymer is preferably used as the organic semiconductor. For example, polypyrroles such as polypyrrole, poly (N-substituted pyrrole), poly (3-substituted pyrrole), poly (3,4-disubstituted pyrrole), polythiophene, poly (3-substituted thiophene), poly (3,4 -Disubstituted thiophene), polythiophenes such as polybenzothiophene, polyisothianaphthenes such as polyisothianaphthene, polyphenylenevinylenes such as polyphenylenevinylene, poly (p-phenylenevinylene) such as poly (p-phenylenevinylene) -Phenylene vinylenes),
Polyaniline, poly (N-substituted aniline), poly (3-
Substituted anilines), polyanilines such as poly (2,3-substituted anilines), polyacetylenes such as polyacetylene,
Polydiacetylenes such as polydiacetylene, polyazulene such as polyazulene, polypyrenes such as polypyrene,
Polycarbazoles such as polycarbazole and poly (N-substituted carbazole); polyselenophenes such as polyselenophene; polyfurans such as polyfuran and polybenzofuran; poly (p-phenylene) s such as poly (p-phenylene) And polyindoles such as polyindole, polypyridazines such as polypyridazine, and polymers such as polyvinylcarbazole, polyphenylene sulfide, and polyvinylene sulfide.

Among these organic π-conjugated materials, thiophene, vinylene, chenylene vinylene, phenylene vinylene, p-phenylene, a polymer having a substituted unit thereof as a repeating unit and the number n of the repeating unit is 10 or more At least one selected from the group consisting of

As other organic semiconductors, σ-conjugated polymers such as polysilane and polygermane can be used.

These compounds are commercially available. However, these compounds usually have a low molecular weight component such as a catalyst at the time of synthesis and monomers and oligomers. For example, an anion of a supporting electrolyte remains in a polymer synthesized by electrolytic polymerization, and a metal component derived from the catalyst remains when synthesized by continuous coupling polymerization using a metal complex catalyst. These residual components act as dopants and increase bulk conductivity. Further, it is considered that the monomer or the oligomer inhibits the orientation continuity of the organic molecule when forming the organic semiconductor layer.

The present invention is characterized in that an organic semiconductor having a low molecular weight component having a molecular weight of 2000 or less and 0.5% by mass or less is used. Most of the commercially available products have a low molecular weight component having a molecular weight of 2,000 or less, which is larger than this specification.
It is necessary to reduce it to 5% by mass or less. Examples of the method include adsorbent treatment using activated carbon, ion exchange treatment, ultrafiltration, and microfiltration, but most organic semiconductors are insoluble in aqueous solvents. Is preferred. Further, these methods may be combined.

In the ultrafiltration, filtration is performed under pressure using a separation membrane. As the material of the ultrafiltration membrane, polyimide, polysulfone, polyvinylidene fluoride, polytetrafluoroethylene,
Polymer materials such as polyethersulfone and inorganic materials such as ceramics are used. For example, FUS-3081 manufactured by Daicel Chemical Industries, Ltd., Grace Japan Co., Ltd.
H15P30-43 manufactured by Nitto Denko Corporation, NTU-
4206, 4220, AIV-3 manufactured by Asahi Kasei Corporation
010, 5010, ACV-3010, 3050, 50
10, 5050, Cefilt manufactured by NGK Insulators, Ltd.
UF and the like. Among them, a resin and a ceramic film having resistance to an organic solvent are useful, and specifically, NTU series manufactured by Nippon Denko KK and Cefilt UF manufactured by NGK Insulators, Ltd. are preferable. The type of the membrane module used in the present invention is not particularly limited, but a tube type, a spiral type, a hollow type, and a monolith type are preferably used. The molecular weight cut-off of the ultrafiltration membrane used is generally 2,000 to 1
00,000, preferably 3,000 to 15,000.

There are several numerical values for filtration accuracy, such as absolute filtration accuracy, quasi-absolute filtration accuracy, or nominal filtration accuracy. For example, the absolute filtration accuracy is usually represented by a particle size capable of capturing 99.99% of particles. The quasi-absolute filtration accuracy is 99.9
% Of the particles can be expressed as a particle size capable of narrowing the particles, and the nominal filtration accuracy is expressed by a particle size capable of capturing 95% of the particles. In the present invention, microfiltration refers to a nominal filtration accuracy of 100 nm or less.

The material of the microfiltration membrane is, for example, Teflon (R), polysulfone, polyvinyl chloride, polyimide,
Inorganic materials such as polyamide, polycarbonate and ceramic films are preferred. For example, H made by Grace Japan Co., Ltd.
15MP01-43, PSP-0 manufactured by Asahi Kasei Corporation
13. Epocell, Paulcell, Rigimesh, Profile, manufactured by Nippon Pall Co., Ltd., Micropure, Suspure, manufactured by Loki Techno Co., Ltd., Cefi, manufactured by NGK Insulators, Ltd.
lt MF and the like.

[0027]

Embodiments of the present invention will be described below in detail.

FIG. 1 is a schematic diagram showing an example of the structure of an organic transistor. In FIG. 1, 7 indicates a support, 2 and 3 indicate source and drain electrodes, respectively, and 4 indicates an organic semiconductor layer formed between the source and drain electrodes. Reference numeral 6 denotes a gate insulating layer provided on the organic semiconductor layer, and reference numeral 5 denotes a gate electrode provided on the gate insulating layer, which has a top gate structure.

The support is made of glass or a flexible resin sheet. In the present invention, a sheet (polymer sheet) made of a polymer material such as polyethylene terephthalate (PET) is preferably used. The source and drain electrodes are formed of a conductive material also described later, and an organic semiconductor layer made of an organic semiconductor such as polypyrrole or polythiophene is provided between the source and drain electrodes, which will be described in detail later. A gate electrode is provided via an insulating layer to constitute an organic transistor.

After the organic semiconductor layer is provided, a gate insulating layer is formed. As the gate insulating layer, a film made of metal oxide or nitride is used.

A dry process such as a vacuum deposition method, a CVD method, a sputtering method, or an atmospheric pressure plasma method is used as a method for forming these metal oxide or nitride films. In these methods, active radiation is used. Since active molecular species and the like are generated and deposited on the substrate to form a film, the organic semiconductor layer is exposed to the active molecular species or actinic radiation, and the surface of the organic semiconductor and carriers near the surface in the organic semiconductor layer are removed. Denaturation of the channel portion causes problems such as an increase in the leak current, a small current when the gate potential is applied, and a decrease in the ON / OFF ratio.

When a film such as a metal oxide is formed by a wet method, for example, a sol-gel method by coating,
The organic semiconductor is modified by the influence of the active species, and the O
The N / OFF ratio is reduced, and the solvent remaining after film formation affects the life.

In the present invention, it is preferable to provide an organic thin film layer comprising an organic compound film between the organic semiconductor layer and the gate insulating layer. After the organic semiconductor layer is provided, a gate insulating layer is formed by a vacuum evaporation method by forming an organic compound film such as polyolefins such as polyethylene and polypropylene, polymers such as polyimide, polyamide, polyester and polyacrylate or various surfactants. Also, when the organic semiconductor layer is formed by a dry process such as an atmospheric pressure plasma method, or when formed by a sol-gel method, which is a wet process, the organic semiconductor layer is damaged by exposure to active molecular species, and the organic semiconductor layer is damaged. Deterioration of the semiconductor can be prevented.

For the formation of the organic thin film layer, it is preferable to use an atmospheric pressure plasma method, a coating method, or a wet process such as screen printing from the viewpoint that a thin film can be continuously applied easily and accurately. The thickness of the organic thin film formed by these methods is 1 nm to 1 μm, preferably 5 nm.
１００100 nm. If the thickness is too large, the gate electric field effect decreases, which is not preferable. If the thickness is too small, the organic semiconductor is adversely affected, and the effect of the present invention cannot be sufficiently obtained.

These organic thin-film layers protect the organic semiconductor layer against active reactive species, have little effect on the organic semiconductor, and have a metal oxide or nitride as a gate insulating layer depending on the active reactive species. The organic thin film layer is not particularly limited as long as it is an organic compound film that does not hinder the deposition on the substrate. Examples of the material used for the organic thin film layer include polyolefins such as polyethylene and polypropylene, various surfactants, and polyimide. , Polyamide, polyester, polyacrylate, photo-radical polymerization type, photo-cationic polymerization type photo-curable resin, or copolymer containing acrylonitrile component, polyvinyl phenol, polyvinyl alcohol, novolak resin, and cyanoethyl pullulan, polymer, elastomer Use of phosphazene compounds containing Can, inter alia polyimide, polyamide, polyester and polyacrylate preferred.

FIG. 2A is a schematic view showing an example of the organic transistor of the present invention. Reference numeral 1 denotes the organic thin film formed between the organic semiconductor layer 4 and the gate insulating layer 6.

FIG. 2B is a schematic view showing another example of the organic transistor of the present invention. In this example, the organic semiconductor layer 4 is applied over the entire surface of the source and drain electrodes (2 and 3 respectively) patterned on the support. In this case, the organic thin film 1 is applied and formed on the entire surface following the application of the organic semiconductor layer 4.

By forming the organic thin film layer between the organic semiconductor layer and the gate insulating layer, the ON / OFF ratio of the organic transistor can be improved.

Hereinafter, each component of the gate insulating layer, the organic semiconductor layer and the like will be described. As the gate insulating layer, metal oxide or nitride is preferable. As inorganic metal oxides, silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate,
Lead zirconate titanate, lanthanum lead titanate, strontium titanate, barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate,
Bismuth tantalate niobate, yttrium trioxide and the like can be mentioned. Among them, preferred are silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide. Similarly, silicon nitride, aluminum nitride, and the like can be suitably used as the metal nitride. As the nitride, silicon nitride is particularly preferred.

As a method for forming a film made of a metal oxide or a nitride, there are a vacuum deposition method, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method, an ion plating method, a CVD method, a sputtering method, A dry process such as a pressure plasma method may be used. The preferred method of the dry process is C
A VD method, a sputtering method, an atmospheric pressure plasma method, particularly an atmospheric pressure plasma method is preferred.

The atmospheric pressure plasma method refers to a process of discharging under an atmospheric pressure or a pressure close to the atmospheric pressure, exciting a reactive gas by plasma, and forming a thin film on a base material. Can be formed with high productivity.
The method is described in JP-A-11-61406, 11
No.-133205, JP-A-2000-185362, 2
000-147209 and 2000-121804. Thereby, a highly functional thin film can be continuously formed on a roll-shaped substrate, for example, by a method with high production efficiency.

A plasma discharge treatment apparatus for forming a metal oxide or nitride film by an atmospheric pressure plasma method discharges between opposed electrodes, introduces a reactive gas between the electrodes to form a plasma state, A thin film is formed by exposing a long film-shaped substrate carried therein to a reactive gas in a plasma state. Further, a jet method or the like may be used in which the substrate is placed or transported near the electrodes, not between the electrodes, and the generated plasma is sprayed on the substrate to form a thin film.

As the electrode, a combination of a conductive base material such as a metal and a lining treated dielectric provided with a lining such as a silicate glass, a borate glass or a phosphate glass is used. In particular, borate-based glass is more preferably used because it is easily processed. Examples of the conductive base material such as a metal include metals such as silver, platinum, stainless steel, aluminum, and iron, and stainless steel is preferable from the viewpoint of processing.

Further, a combination in which ceramic is sprayed on a conductive base material such as a metal and coated with a ceramic-coated dielectric material which has been subjected to pore-sealing treatment using an inorganic material may be used. As a ceramic material used for thermal spraying, alumina is preferably used because it is easy to process.

As a power source for applying a voltage to the application electrode,
Although not particularly limited, a high frequency power supply (2
00 kHz), high frequency power supply (800
kHz), a high frequency power supply (13.56M) manufactured by JEOL Ltd.
Hz), Pearl Industry Co., Ltd. high frequency power supply (150MH)
z) etc. can be used.

The distance between the electrodes is determined in consideration of the thickness of the solid dielectric placed on the base material of the electrodes, the magnitude of the applied voltage, the purpose of utilizing the plasma, and the like. The shortest distance between the solid dielectric and the electrode when a solid dielectric is installed on one of the electrodes,
The distance between the solid dielectrics when the solid dielectrics are installed on both of the electrodes is preferably 0.5 to 20 mm, particularly preferably 1 ± 0.5 mm, from the viewpoint of performing a uniform discharge in any case. is there.

A high-frequency voltage exceeding 100 kHz and a power of 1 W / cm ² or more are supplied between the opposing electrodes to excite the reactive gas to generate plasma. By applying such a high-power electric field, it is possible to obtain a dense, highly functional thin film having high uniformity in film thickness with high production efficiency.

Here, the upper limit of the frequency of the high frequency voltage applied between the electrodes is preferably 150 MHz or less. The lower limit of the frequency of the high-frequency voltage is preferably 200 kHz or more, and more preferably 800 kHz or more.

Further, the lower limit of the power supplied between the electrodes is
It is preferably at least 1.2 W / cm ² , and the upper limit is preferably at most 50 W / cm ² , more preferably at most 20 W / cm ² . Note that the voltage application area of the electrode refers to an area in a range where discharge occurs.

The value of the voltage applied to the electrode fixed from the power supply is determined as appropriate. Regarding the power supply method, either a continuous sine wave continuous oscillation mode called a continuous mode or an intermittent oscillation mode in which ON / OFF is intermittently called a pulse mode may be adopted, but the continuous mode is more preferable. A dense and high quality film can be obtained.

In order to minimize the influence on the substrate during the discharge plasma treatment, the temperature of the substrate during the discharge plasma treatment is adjusted to a temperature between room temperature (15 to 25 ° C.) and less than 200 ° C. And more preferably room temperature to 100
It is to adjust to ° C. In order to adjust the temperature to the above-mentioned temperature range, the electrodes and the base material are subjected to a discharge plasma treatment while being cooled by a cooling means as necessary.

The above-mentioned discharge plasma treatment is performed at or near atmospheric pressure.
Represents a pressure of 110 kPa, preferably 93 to 104
kPa.

In carrying out the thin film forming method, the gas used is basically a mixed gas of an inert gas and a reactive gas for forming a thin film. The reactive gas is preferably contained at 0.01 to 10% by volume based on the mixed gas.

The inert gas includes elements belonging to Group 18 of the periodic table, specifically, helium, neon, argon, krypton, xenon, radon and the like.
Argon is preferably used.

As the reaction gas, a compound which forms an insulating film such as a metal oxide or a nitride is selected, and a metal compound such as a silicon compound and a titanium compound can be mentioned. Metal alkoxides are preferred, and metal alkoxides are preferably used because they have no corrosiveness, no harmful gas is generated, and there is little contamination in the process.

In order to introduce the silicon compound and the titanium compound between the electrodes, which are discharge spaces, both of them must be gaseous
It may be in a liquid or solid state. In the case of gas, it can be directly introduced into the discharge space, but in the case of liquid or solid, it is used after being vaporized by means such as heating, decompression, or ultrasonic irradiation. When a silicon compound or a titanium compound is used after being vaporized by heating, it is liquid at normal temperature and has a boiling point of 20 such as tetraethoxysilane and tetraisopropoxytitanium.
A metal alkoxide having a temperature of 0 ° C. or lower is preferably used.
The metal alkoxide may be used after being diluted with a solvent. As the solvent, an organic solvent such as methanol, ethanol, or n-hexane, or a mixed solvent thereof can be used. Note that these diluting solvents are decomposed into molecules and atoms during the plasma discharge treatment, so that the influence on the formation of the thin film on the base material, the composition of the thin film, and the like can be almost ignored.

Examples of the silicon compound include organometallic compounds such as dimethylsilane and tetramethylsilane, metal hydrogen compounds such as monosilane and disilane, silane dichloride, and the like.
It is preferable to use a metal halide such as trichloride silane, an alkoxysilane such as tetramethoxysilane, tetraethoxysilane, or dimethyldiethoxysilane, or an organosilane, but it is not limited thereto. These can be used in appropriate combination.

When the above-described silicon compound is used in the mixed gas, the content of the silicon compound in the mixed gas is 0.1 to 0.1 from the viewpoint of forming a uniform thin film on the substrate by discharge plasma treatment. The content is preferably 10% by volume, more preferably 0.1 to 5% by volume.

Examples of the titanium compound include organometallic compounds such as tetradimethylaminotitanium; metal hydrogen compounds such as monotitanium and dititanium; metal halogen compounds such as titanium dichloride, titanium trichloride and titanium tetrachloride; tetraethoxytitanium; It is preferable to use metal alkoxides such as isopropoxytitanium and tetrabutoxytitanium, but not limited thereto.

When a titanium compound is used in the mixed gas,
From the viewpoint of forming a uniform thin film on the base material by the discharge plasma treatment, the content of the titanium compound in the mixed gas is 0.1%.
The content is preferably from 1 to 10% by volume, and more preferably from 0.1 to 5% by volume.

The mixed gas contains hydrogen gas in an amount of 0.1 to 1%.
By containing 0% by volume, the hardness of the thin film can be remarkably improved, and 0.01 to 5% by volume of a component selected from oxygen, ozone, hydrogen peroxide, carbon dioxide, carbon monoxide, hydrogen and nitrogen is contained. By doing so, the reaction is promoted, and a dense and high-quality thin film can be formed.

As the method of forming the insulating film, there are coating methods such as spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, printing and ink jet printing. And a wet process such as a method based on patterning.

In the wet process, a solution of a metal oxide precursor, for example, a metal alkoxide is applied and dried.
The so-called sol-gel method is particularly preferred because of its high production efficiency.

The sol-gel method is a method in which a metal oxide gel film is formed by dehydrating a hydrated oxide sol using a metal compound such as a metal alkoxide having sol-gel reactivity. And can be formed by coating.

As a metal compound having sol-gel reactivity
Is a metal alkoxide, acetylacetonato complex, metal
Acetate, metal oxalate, metal nitrate, metal sulfate, gold
Genus carbonate, metal oxychloride, etc.
Alkoxides are highly reactive, from the metal-oxygen bond
This is preferable because the resulting polymer is easily formed. Metal alkoxy
Do is M (OR)_n(M is a metal element
Element, R represents an alkyl group, and n represents the oxidation number of the metal element).
As an example, Si (OCH_Three)_Four, Si (OC _TwoH_Five)
_Four, Si (OC_ThreeH₇)_Four, Al (OCH_Three)_Three, Al (OC
_TwoH_Five)_Three, Ti (OCH_Three)_Four, Ti (OC_TwoH_Five)_Four, Zr
(OCH_Three)_FourAre used. Further, CH_ThreeSi (O
CH_Three)_ThreeMonosubstituted silicon alkoxides such as
You.

Among them, Si (OCH ₃ ) ₄ and Si (OCH ₃ ) ₄
Silicon alkoxide compounds such as C ₂ H ₅ ) ₄ and Si (OC ₃ H ₇ ) ₄ are particularly inexpensive and readily available, and a metal oxide coating layer obtained therefrom is particularly preferable because of its excellent developer resistance.
Oligomers obtained by partially hydrolyzing and condensing these silicon alkoxide compounds are also preferable.

The content of the metal compound having sol-gel reactivity is preferably 10% by mass or more, and is preferably 20 to 6%.
A range of 0% by mass is more preferable.

In order to make these metal compounds having sol-gel reactivity into a reaction solution having sol-gel reactivity, it is preferable to include a catalyst, water and an organic solvent.

As a catalyst, an organic acid, an inorganic acid or an alkali is used. Examples thereof include inorganic acids such as hydrochloric acid and sulfuric acid, acetic acid, fluoroacetic acid, citric acid, organic acids such as oxalic acid, hydroxides of alkali metals and alkaline earth metals,
Examples include alkali such as ammonia and ethanolamine.

In addition to the above, organic acids such as sulfonic acids such as p-toluenesulfonic acid can also be used.

The amount of the catalyst is preferably 0.001 to 10% by mass, more preferably 0.05 to 5% by mass, based on the metal compound having sol-gel reactivity. If the amount of the catalyst is less than this range, the start of the sol-gel reaction is delayed, and if it is more than this range, the reaction proceeds rapidly, resulting in an uneven film.

To initiate the sol-gel reaction, it is preferable to have an appropriate amount of water. The preferable addition amount of water is preferably 0.05 to 50 times, more preferably 0.5 to 30 times, the amount of water necessary for completely hydrolyzing the binder (metal compound) having a sol-gel reaction. It is. If the amount of water is less than this range, the hydrolysis does not easily proceed, and if it is more than this range, the reaction becomes difficult to proceed, probably because the raw materials are diluted.

Examples of the organic solvent include lower alcohols such as methanol, ethanol, propanol, and butanol.
Ketones such as acetone, methyl ethyl ketone and diethyl ketone are used. Lower alcohols that are miscible with water are preferred. The content of the organic solvent is 100 to 5000% by mass (1 to
50 times), preferably from 200 to 2000% by mass.
(1 to 20 times) is more preferable.

The sol-gel reactive coating solution is applied on the organic semiconductor layer by the above-mentioned wet process, and is heated and dried. Further, if necessary, the gate insulating layer is obtained by baking (100 ° C. or higher).

The thickness of the gate insulating layer formed by these methods is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

Examples of the method for producing these organic semiconductor thin films include vacuum deposition, molecular beam epitaxial growth, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, and the like.
Plasma polymerization, electrolytic polymerization, chemical polymerization, spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, LB coating, etc. Can be used according to However, from the viewpoint of productivity, spin coating, blade coating, dip coating, and the like, which can easily and accurately form a thin film using a solution of an organic semiconductor.
Roll coating, bar coating, die coating and the like are preferred. The thickness of these organic semiconductor thin films is
Although there is no particular limitation, the characteristics of the obtained transistor often largely depend on the thickness of the organic semiconductor layer, and the thickness varies depending on the organic semiconductor, but is generally 1 μm or less, particularly preferably 10 to 300 nm. .

The electrode material such as the gate electrode, the source electrode and the drain electrode is not particularly limited as long as it is a conductive material. Platinum, gold, silver, nickel, chromium, copper, iron, tin,
Antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy Carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese,
Zirconium, gallium, niobium, a sodium-potassium alloy, a magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide mixture, a lithium / aluminum mixture, and the like are used. , Gold, silver, copper, aluminum, indium, ITO and carbon are preferred. Alternatively, a known conductive polymer whose conductivity has been improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, or the like is also preferably used. Among the above, the source electrode and the drain electrode preferably have low electric resistance at the contact surface with the semiconductor layer.

As a method for forming an electrode, a method of forming an electrode by patterning a conductive thin film formed by using the above materials as a raw material by a method such as vapor deposition or sputtering by a known photolithographic method or lift-off method, And a method of performing etching using a resist by thermal transfer, ink jet, or the like on a metal foil such as copper or copper. Further, a solution or dispersion of a conductive polymer or a metal fine particle dispersion may be directly patterned by an inkjet method, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning an ink or a conductive paste containing a conductive polymer or metal fine particles by a printing method such as letterpress, intaglio, lithographic, or screen printing can also be used.

As a method for producing such a metal fine particle dispersion, metal ions can be formed in a physical layer such as a gas evaporation method, a sputtering method or a metal vapor synthesis method, or in a liquid layer such as a colloid method or a coprecipitation method. A chemical production method of producing metal fine particles by reduction is mentioned, and preferably, a method of JP-A-11-7680 is used.
No. 0, No. 11-80647, No. 11-319538
, Colloid method disclosed in JP-A-2000-239853, JP-A-2001-254185 and JP-A-2001-530.
28, 2001-35814, 2001-3525
5, 2000-124157, 2000-1236
24 is a dispersion produced by a gas evaporation method described in No. 24 or the like. After these dispersions are applied and molded into an electrode pattern, the solvent is dried, and the temperature is further increased to 100 to 300 ° C.
Preferably, heat treatment is performed at a temperature in the range of 150 to 200 ° C., and the metal fine particles are thermally fused to form an electrode.

As the support, a glass or flexible resin sheet can be used. In particular, for forming a flexible organic transistor, it is preferable to use a polymer sheet such as a plastic film.
Examples of the plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyether imide, polyether ether ketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose. Triacetate (T
AC), cellulose acetate propionate (CA)
P) and the like. These films can be subjected to known surface treatment and surface coating. For example, a co-evaporated film of silicon oxide and aluminum oxide, a mixed film of silicon oxide and a metal oxide such as aluminum oxide by an atmospheric pressure plasma method or a multilayer composite film may be formed as the gas barrier layer. Further, a composite film obtained by laminating a film or the like on which a metal thin film of aluminum or the like is deposited may be used, or metal oxide fine particles may be contained in the film. As described above, by using a plastic film, it is possible to achieve flexibility and weight reduction as compared with the case of using a glass substrate, to improve portability, and to improve resistance to impact.

Further, the organic transistor according to the present invention is preferably separated from the atmosphere by a protective film in order to prevent the life of the organic transistor from being shortened by oxygen, moisture and the like in the atmosphere. As the protective film, a gas barrier film such as PVA or ethylene-vinyl alcohol copolymer, or an inorganic material described in the description of the insulating layer can be used.

[0082]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 (Production of Organic Transistor 1) An organic transistor 1 was produced according to the configuration example shown in FIG.

On a 150 μm thick polyimide film,
A 20 nm Au thin film was deposited and source and drain electrodes (2 and 3 respectively) were formed by photolithography. The length of the channel between the source and the drain was 10 μm. Furthermore, commercially available poly (3-hexylthiophene)
Was discharged using a piezo-type inkjet, and the solution was filled between the source and drain electrodes. After drying the solvent chloroform, it was heat-treated at 100 ° C. for 5 minutes and left in vacuum for 24 hours. The thickness of the formed poly (3-hexylthiophene) film of the organic semiconductor layer 4 was about 50 nm. After exposing this to an ammonia gas atmosphere at room temperature for 5 hours, using an atmospheric pressure plasma discharge treatment apparatus described in JP-A-2000-80182, argon (98.2% by volume), tetramethoxysilane ( 0.3% by volume) and a thickness of 500 μm on the organic semiconductor layer 4 using a mixed gas of hydrogen gas (1.5% by volume).
A silicon oxide film having a thickness of 10 nm was formed as the gate insulating layer 6.

Next, using a commercially available Ag paste,
An organic transistor 1 was obtained by forming a gate electrode of 0 μm by screen printing.

(Preparation of Organic Transistor 2) In place of commercially available poly (3-hexylthiophene), commercially available poly (3
-Hexylthiophene) was dissolved in toluene, and the purification method of adding and reprecipitating with acetone was repeated three times to produce an organic transistor 2 in the same manner as the organic transistor 1 except that purified poly (3-hexylthiophene) was used.

(Preparation of Organic Transistor 3) Instead of commercially available poly (3-hexylthiophene), commercially available poly (3
-Hexylthiophene) was dissolved in chloroform, and Cefilt MF (pore size 0.1 μm) manufactured by NGK Insulators, Ltd. was used.
An organic transistor 3 was produced in the same manner as in the organic transistor 1 except that poly (3-hexylthiophene) purified by microfiltration using m) was used.

(Preparation of Organic Transistor 4) Instead of commercially available poly (3-hexylthiophene), commercially available poly (3
-Hexylthiophene) was dissolved in chloroform, and Cefilt UF (manufactured by NGK Insulators, Ltd.) was used.
Organic transistor 4 was produced in the same manner as in organic transistor 1, except that poly (3-hexylthiophene) purified by ultrafiltration using 000 and a pore diameter of 4 nm was used.

(Preparation of Organic Transistor 5) FIG. 2 (b)
The organic transistor 5 was produced in accordance with the configuration example.

On a 150 μm thick polyimide film,
A 20 nm Au thin film was deposited and source and drain electrodes (2 and 3 respectively) were formed by photolithography. The length of the channel between the source and the drain was 10 μm. Furthermore, commercially available poly (3-hexylthiophene)
Is dissolved in chloroform, and NGK NGK Insulators, Ltd.
ilt UF (fraction molecular weight 10,000, pore size 4n
m) was used for ultrafiltration. A chloroform solution of the purified poly (3-hexylthiophene) was discharged using a piezo-type inkjet, and the solution was filled between the source and drain electrodes. After drying the solvent chloroform, 1
Heat treated at 00 ° C. for 5 minutes and left in vacuum for 24 hours.
The thickness of the formed poly (3-hexylthiophene) film of the organic semiconductor layer 4 was about 50 nm. After exposing this to an ammonia gas atmosphere at room temperature for 5 hours, a source electrode,
On a drain electrode and a poly (3-hexylthiophene) film, a polyimide (Ricacoat SN-20, 20% by mass N-methyl-2-pyrrolidone solution: Shin Nippon Rika Co., Ltd.)
The solution was applied and dried to form an organic thin film 1 having a thickness of 30 nm. Further, using an atmospheric pressure plasma discharge treatment apparatus described in JP-A-2000-80182, argon (98.2% by volume), tetramethoxysilane (0.3% by volume), and hydrogen gas (1.5% by volume) were used as reactive gases. %), A silicon oxide film having a thickness of 500 nm was formed as the gate insulating layer 6 on the organic thin film 1 using a mixed gas consisting of

Next, using a commercially available Ag paste, the width 2
A gate electrode of 0 μm was formed by screen printing to obtain an organic transistor 5.

(Preparation of Organic Transistor 6) Instead of commercially available poly (3-hexylthiophene), commercially available poly (3
Organic transistor 6 was produced in the same manner as in the organic transistor 1 except that -octylthiophene) was used.

(Preparation of Organic Transistor 7) In place of commercially available poly (3-hexylthiophene), commercially available poly (3
-Octylthiophene) was dissolved in chloroform, and Cefilt UF (fraction molecular weight 1) manufactured by NGK Insulators, Ltd.
Organic transistor 7 was produced in the same manner as in the case of organic transistor 1, except that poly (3-octylthiophene) purified by ultrafiltration using 000 and a pore diameter of 4 nm was used.

(Preparation of Organic Transistor 8) Instead of commercially available poly (3-hexylthiophene), commercially available poly (3
Organic transistor 8 was produced in the same manner as in the organic transistor 1 except that -butylthiophene) was used.

(Preparation of Organic Transistor 9) In place of commercially available poly (3-hexylthiophene), commercially available poly (3
-Butylthiophene) was dissolved in chloroform, and Cefilt UF (manufactured by NGK Insulators, Ltd.) was used.
Organic transistor 9 was produced in the same manner as in the organic transistor 1 except that poly (3-butylthiophene) purified by ultrafiltration using 000 and a pore size of 4 nm was used.

(Measurement of Low Molecular Weight Component) A low molecular weight component having a molecular weight of 2000 or less in the organic semiconductor used in the organic transistors 1 to 9 was measured under the following conditions.

Apparatus: HLC-8220GPC (manufactured by Tosoh Corporation) Column: TSKgel GMHXL (manufactured by Tosoh Corporation)
Column temperature: 40 ° C. Eluent: THF Eluent flow rate: 1.0 ml / min Detector: RI The molecular weight distribution measurement charts of the organic semiconductor used in the organic transistors 1, 2, and 4 are shown in FIG. (B),
It is shown in (c). 21. Retention time at the lower right of each measurement chart
The component after 5 minutes is a low molecular weight component having a molecular weight of 2000 or less. Table 1 shows the low molecular weight components (% by mass).

(Evaluation of Organic Transistor)
The evaluation of the transistor was performed using an evaluation system as shown in FIG.
3 × 10 ^-2The test was performed under a vacuum of Pa. Leakage current
Current value when the voltage between the source and drain is -30 V
And the ON / OFF ratio is a voltage between the source and the drain of −3.
0 V and the gate voltage is -30 V (ON)
The current value between the source and the drain and the gate voltage were set to 0 V
Time (OFF) and the ratio between the current value between the source and the drain
Represent. Table 1 shows the measurement results.

[0099]

[Table 1]

In order for an organic semiconductor to be used as an active semiconductor layer in a thin film field effect transistor, generally,
ON / OFF ratio must be at least 10 ^3. In this example, it was confirmed that the ON / OFF ratio was improved and the leak current was reduced.

[0101]

As described above, it is possible to provide an organic transistor having a reduced leakage current and an excellent ON / OFF ratio, and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of a configuration of an organic transistor.

FIG. 2 is a schematic view showing an example of the organic transistor of the present invention.

FIG. 3 is a diagram showing an evaluation system for an organic transistor.

FIG. 4 is a chart for measuring the molecular weight distribution of an organic semiconductor.

[Explanation of symbols]

1 Organic thin film 2 Source electrode 3 Drain electrode 4 Organic semiconductor layer 5 Gate electrode 6 Gate insulating layer 7 Support

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Hiroyuki Yasukawa             Konica Stock Exchange, 1 Sakuracho, Hino-shi, Tokyo             In-house (72) Inventor Akira Maruyama             Konica Stock Exchange, 1 Sakuracho, Hino-shi, Tokyo             In-house F term (reference) 5F110 AA06 BB01 CC05 DD01 DD02                       EE02 EE03 EE07 EE42 EE43                       EE44 FF01 FF02 FF03 FF09                       FF27 FF28 FF29 FF30 FF35                       FF36 GG05 GG06 GG25 GG28                       GG42 HK02 HK03 HK32 HK33                       QQ06 QQ14

Claims (6)

[Claims] An organic transistor comprising an organic semiconductor having a low molecular weight component having a molecular weight of 2000 or less and 0.5 mass% or less. 2. A source and drain electrode provided on a support, an organic semiconductor layer formed in contact with the electrode, a gate insulating layer formed in contact with the organic semiconductor layer, and a gate insulating layer formed on the gate insulating layer. In the organic transistor comprising the gate electrode, the gate insulating layer is made of a metal oxide or nitride formed by an atmospheric pressure plasma method, and the organic semiconductor layer between the source and drain electrodes has a low molecular weight component having a molecular weight of 2000 or less. An organic transistor comprising an organic semiconductor of 0.5% by mass or less. 3. A source and drain electrode provided on a support, an organic semiconductor layer formed in contact with the electrode, a gate insulating layer formed in contact with the organic semiconductor layer, and a gate insulating layer formed on the gate insulating layer. In the organic transistor consisting of the gate electrode, the gate insulating layer is made of silicon oxide, silicon nitride,
Selected from at least one of aluminum oxide, tantalum oxide, and titanium oxide, wherein the organic semiconductor layer between the source and drain electrodes is made of an organic semiconductor having a low molecular weight component having a molecular weight of 2000 or less and 0.5 mass% or less. Characteristic organic transistor. 4. A source and drain electrode provided on a support, an organic semiconductor layer formed in contact with the electrode, a gate insulating layer formed in contact with the organic semiconductor layer, and a gate insulating layer formed on the gate insulating layer. Organic transistor comprising a gate electrode, the organic semiconductor layer is polyimide, polyamide,
The organic semiconductor layer between the source and drain electrodes is formed in contact with a layer made of either polyester or polyacrylate.
An organic transistor comprising an organic semiconductor in an amount of 5% by mass or less. 5. A method for producing an organic transistor, comprising using an organic semiconductor purified by ultrafiltration so that a low molecular weight component having a molecular weight of 2000 or less is reduced to 0.5% by mass or less. 6. A method for producing an organic transistor, comprising using an organic semiconductor purified by microfiltration so that a low molecular weight component having a molecular weight of 2,000 or less is reduced to 0.5% by mass or less.