WO2010082414A1 - Organic thin film transistor, method for manufacturing same, and device equipped with same - Google Patents

Abstract

Disclosed is an organic thin film transistor characterized by comprising at least a gate electrode, a source electrode, a drain electrode, an insulating layer and an organic semiconductor layer all arranged on a support, wherein the insulating layer is a silica-type organic-inorganic hybrid film produced by shaping an amphipathic oligomer into a thin film, wherein the amphipathic oligomer is produced by the cohydrolysis/polycondensation of an alkoxysilane containing a linear hydrocarbon group and a tetraalkoxysilane or the hydrolysis/polycondensation of an alkoxysilane containing a linear hydrocarbon group.  Also disclosed is a method for manufacturing the organic thin film transistor.  Further disclosed is a device equipped with the organic thin film transistor.  It becomes possible to provide an organic insulating material which can be shaped into a film conveniently by means of a coating technique, a printing technique or the like and has excellent characteristics required for an insulating material for an organic transistor such as a low surface energy, a high dielectric constant, good insulation properties and good surface flatness, and therefore it becomes possible to provide an organic thin film transistor having a low threshold voltage and a high field effect mobility by utilizing the insulating material.

Description

ORGANIC THIN FILM TRANSISTOR, MANUFACTURING METHOD THEREOF, AND DEVICE PROVIDED WITH THE SAME

The present invention relates to an organic thin film transistor, a method for manufacturing the same, and an apparatus including the organic thin film transistor, and in particular, an organic thin film transistor having excellent device characteristics such as response speed, operating voltage, on / off ratio, and reliability by improving an insulating layer, The present invention relates to a manufacturing method and an apparatus including the manufacturing method.

Thin film transistors (hereinafter sometimes abbreviated as TFTs) are widely used as display switching elements in liquid crystal display devices and the like.
Conventionally, TFTs have been manufactured using amorphous or polycrystalline silicon. However, CVD devices used for manufacturing TFTs using such silicon are expensive and large-sized display devices using TFTs or the like. There has been a problem that the production is accompanied by a significant increase in manufacturing cost. In addition, the process of depositing amorphous or polycrystalline silicon is performed at a very high temperature, so the types of materials that can be used as a substrate are limited, light weight and flexibility can be imparted. However, there is a problem that a resin substrate or the like that can be designed in shape cannot be used. If a TFT can be manufactured on a lightweight resin substrate, it is expected that it can be applied to a portable electronic device.
In order to solve such a problem, a TFT using an organic semiconductor (hereinafter sometimes abbreviated as an organic TFT) has been proposed. Vacuum deposition and coating methods are known as film formation methods used when forming TFTs with organic semiconductors. According to these film formation methods, the device can be enlarged while suppressing an increase in manufacturing cost. Therefore, the process temperature required for film formation can be made relatively low. In addition, TFTs using organic substances have the advantage that there are few restrictions when selecting materials used for the substrate, and their practical application is expected.
As an element configuration of an organic thin film transistor, a top contact type, a bottom contact type, a bottom contact / top gate type, and the like are known. In any configuration, the insulator layer is an important configuration that affects the performance of the organic thin film transistor. Is an element. In order to achieve the desirable characteristics of organic thin film transistors, ie, high extraction current, low operating voltage, high on / off current ratio, and high reliability, various insulator materials have been studied.

Under such circumstances, various materials have been studied for the insulator layer of the organic TFT.
Examples of the inorganic insulating film material include SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , BZT, Ta ₂ O ₅ , and TiO ₂ . When a heavily doped silicon substrate is used as the gate electrode, the thermally oxidized SiO ₂ film on the surface thereof is an excellent insulating film, and is widely used in the evaluation of organic semiconductor materials. In general, Si—OH defects and water are present on the surface of the thermally oxidized SiO ₂ film, and the surface levels caused by these defects become charge traps, which reduce field effect mobility, hysteresis, threshold Adversely affects voltage. In order to avoid the above problems, a method of surface treatment with hexamethyldisilazane (HMDS) or octadecyltrichlorosilane (OTS) to make the surface water-repellent with low surface energy (increase the water contact angle) is studied. (For example, refer nonpatent literature 1). Film formation processes such as vapor deposition, sputtering, and CVD are used for the film formation of the inorganic material, but these have a demerit that they are expensive because they require a vacuum chamber and the operation cost is also high. In addition, in order to obtain good film quality, film formation at a high temperature may be necessary, and application to a flexible film substrate or the like is difficult.
In addition, polymer materials have been actively studied from the expectation that they are compatible with solution processes such as coating and film formation, and that cost reduction is possible. Typical polymer materials are polypropylene, polyvinyl alcohol (PVA), polyvinylphenol (PVP), polyisobutylene, polymethyl methacrylate (PMMA), polyparaxylylene, polyethylene terephthalate (PET), polyimide, and the like. The polymer insulating film generally has a smooth surface, but has a relative dielectric constant of about 3. If the film thickness is increased in order to ensure insulation, the gate capacitance decreases and the operation of the thin film transistor element tends to increase in voltage. . Materials having a strong polarity and a large relative dielectric constant, such as cyanopullulan, have been proposed. However, highly polar polymers are generally considered undesirable because traps present on the surface can degrade FET performance and induce hysteresis.
As described above, various insulator materials and their configurations have been studied, but it is difficult to obtain desired characteristics with one kind of insulator material. Thus, attempts have been made to use a combination of a plurality of insulator materials, a combination of inorganic fine particles and organic materials, and a modification of the insulator surface by surface treatment, but the manufacturing process becomes complicated and costly. Is also disadvantageous.

In order to solve the above problems, an attempt has been made to use an organic / inorganic hybrid film based on a siloxane network as an insulator layer.
For example, Patent Document 1 relates to an invention of an organic semiconductor element containing a resin component having a ladder-type silsesquioxane skeleton in an insulator layer. This insulator layer is formed at a low temperature by a simple process such as printing or spin coating. It is disclosed that the element can be driven at a low voltage and operates stably. However, in the structure of the resin component, since the side chain is short, the uniformity of the film is not sufficient. For this reason, the performance of the obtained organic transistor was insufficient particularly in the on / off current ratio. Also, the relative dielectric constant is 3.8, which is insufficient to contribute to lowering the voltage of the device.
Patent Document 2 relates to an invention of an organic semiconductor element containing a resin component having a silsesquioxane skeleton in an insulator layer, and an active group (hydroxyl group or a hydrogen atom of a hydroxyl group is substituted with a hydrophobic group in a side chain structure. In other words, it is said that a dense film can be obtained by introducing a base), whereby an organic semiconductor element capable of being driven at a low voltage and having a stable driving voltage value can be manufactured. However, when an active group such as a hydroxyl group enters the side chain structure, the surface of the insulating film has a low surface energy, which hinders the crystal growth of the organic semiconductor material formed on the film and lowers the transistor characteristics. It was.

In addition, Patent Document 3 discloses an organic TFT using a polymer of methacryloxypropyltrimethoxysilane which is an organic-inorganic hybrid substance as an insulating film material.
Patent Document 4 discloses an organic TFT using a dielectric material prepared from a siloxy / metal oxide hybrid composition as an insulating film. Siloxy components of the siloxy / metal oxide hybrid composition include siloxane. Alternatively, silsesquioxane or the like is described, and as the metal oxide, oxides such as titanium, aluminum, zirconium, hafnium, tantalum, strontium, yttrium, and lanthanum are described.
Patent Document 5 discloses a gate insulating layer of a thin film transistor comprising a sol-gel silica-containing compound processed at a temperature of less than about 250 ° C.
Patent Document 6 discloses an organic device using a highly aligned siloxane-based molecular film, and is said to exhibit high stability.
Patent Document 7 discloses a semiconductor element using an amino group-containing polysiloxane as an insulating film.
Further, Non-Patent Document 2 describes a TFT using polysilsesquioxane having a methyl group and a cyanoethyl group in the side chain as an insulating film.
Non-Patent Document 3 describes a TFT using polysilsesquioxane in which various functional groups are introduced into the side chain.
Non-Patent Document 4 describes a TFT using polysilsesquioxane in which an epoxy group is introduced into a side chain.

JP 2004-304121 A JP 2007-258663 A JP 2005-120371 A JP 2006-135327 A JP 2008-124431 A JP 2007-145984 A JP 2007-103921 A

However, with polysilsesquioxane insulation obtained by hydrolysis / condensation polymerization of trifunctional trimethoxysilane, it is essentially difficult to lengthen the alkyl chain structure of the side chain. When the length is increased, the balance between the siloxane network and the organic side chain deteriorates, the uniformity of the film is impaired, the crystallization of the semiconductor material is adversely affected, and the performance as a transistor is degraded. The obtained film was essentially an amorphous film and had no order.

The present invention has been made to solve the above problems, and can be easily formed by a coating method, a printing method, or the like, and has a low surface energy, a high dielectric constant, which are required for an insulator material for organic transistors, Provided is an excellent organic insulator material having characteristics such as good insulation and good surface flatness, and by applying the material, an organic thin film transistor having a low threshold voltage and a high field effect mobility, a manufacturing method thereof, and the same An object is to provide an apparatus.

As a result of intensive studies to achieve the above object, the present inventors have obtained a thin film of an amphiphilic oligomer obtained by (co) hydrolysis / condensation polymerization of a chain hydrocarbon group-containing alkoxysilane. It discovered that the silica type organic-inorganic hybrid film | membrane obtained by forming into a film was used. In this silica-based organic-inorganic hybrid film, self-organization occurs due to the interaction between the hydrophilic group and the hydrophobic group in the process of forming the film by the amphiphilic oligomer, and a long-range order is brought about in the film. Further, the order distance can be controlled (amorphous structure) by selecting the polymerization conditions. As a result, desirable characteristics such as low surface energy, high dielectric constant, good insulation, and good surface flatness are satisfied at the same time. When applied to the insulation film of organic thin film transistors, the performance of organic semiconductor materials is extracted, and excellent transistor characteristics. The present invention has been completed.
That is, the present invention
1. An organic thin film transistor having at least a gate electrode, a source electrode, a drain electrode, an insulator layer, and an organic semiconductor layer on a substrate, wherein the insulator layer is a chain hydrocarbon represented by the following general formula (1-a) Silica-based organic-inorganic hybrid obtained by forming a thin film of an amphiphilic oligomer obtained by cohydrolysis and condensation polymerization of a group-containing alkoxysilane A and a tetraalkoxysilane represented by the following general formula (2) An organic thin film transistor characterized by being a film,

Wherein R ¹ is a chain hydrocarbon group having 6 or more carbon atoms, R ² is a linear or branched alkyl group having 1 to 3 carbon atoms, and R ³ and R ⁴ are each independently And a straight-chain or branched alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms.)
Si (OR ⁵ ) ₄ (2)
(In the formula, R ⁵ is a methyl group or an ethyl group.)
2. An organic thin film transistor having at least a gate electrode, a source electrode, a drain electrode, an insulator layer, and an organic semiconductor layer on a substrate, wherein the insulator layer is a chain hydrocarbon represented by the following general formula (1-b) An organic thin film transistor characterized by being a silica-based organic-inorganic hybrid film obtained by thin-film formation of an amphiphilic oligomer obtained by hydrolysis / condensation polymerization of a group-containing alkoxysilane B;

(Wherein R ⁶ is a chain hydrocarbon group having 6 or more carbon atoms, and R ⁷ to R ⁹ are each independently a linear or branched alkyl group having 1 to 3 carbon atoms. R ⁷ , R ⁸ and R ⁹ may be the same or different from each other.)
3. The organic thin-film transistor according to 1 or 2 above, wherein the silica-based organic-inorganic hybrid film is a layered silica-based hybrid film,
4). 3. The organic thin film transistor according to 1 or 2 above, wherein the silica-based organic-inorganic hybrid film is an amorphous silica-based hybrid film,
5). 3. The organic thin film transistor according to 2 above, wherein the silica-based organic-inorganic hybrid film is a rod-like aggregate structure silica-based hybrid film,
6). 3. The organic thin film transistor according to 2 above, wherein R ⁶ in the general formula (1-b) is a chain hydrocarbon group having 14 to 18 carbon atoms, and the silica-based organic-inorganic hybrid film is a layered silica-based hybrid film;
7). 3. The organic thin film transistor according to 2 above, wherein R ⁶ in the general formula (1-b) is a chain hydrocarbon group having 6 to 13 carbon atoms, and the silica-based organic-inorganic hybrid film is a rod-like aggregated-structure silica-based hybrid film. ,
8). 8. The method for producing an organic thin film transistor according to any one of 1 to 7 above, wherein an amphiphilic oligomer is applied to form a silica-based organic-inorganic hybrid film; An apparatus comprising the organic thin film transistor according to any one of 1 to 7 above,
I will provide a.

The organic thin film transistor of the present invention can be easily formed by a coating method, a printing method, and the like, and an insulating layer having excellent characteristics such as low surface energy, high dielectric constant, good insulation, and good surface smoothness. Therefore, it has a low threshold voltage and a high field effect mobility.

It is sectional drawing which shows an example of a top contact type organic thin-film transistor. It is sectional drawing which shows an example of a bottom contact type organic thin-film transistor. It is sectional drawing which shows an example of a bottom contact top gate type organic thin-film transistor. It is a schematic diagram which shows the layered structure of the amphiphilic oligomer obtained from chain | strand-shaped hydrocarbon group containing alkoxysilane A and tetraalkoxysilane. It is a schematic diagram which shows the layered silica type hybrid film | membrane which uses chain | strand-shaped hydrocarbon group containing alkoxysilane A and tetraalkoxysilane. It is a schematic diagram which shows the layered structure of the amphiphilic oligomer obtained from chain hydrocarbon group containing alkoxysilane B. It is a schematic diagram which shows the layered silica type | system | group hybrid film | membrane formed using the linear hydrocarbon group containing alkoxysilane B. FIG. It is a schematic diagram which shows an amorphous silica type hybrid membrane. It is a schematic diagram which shows the cylindrical aggregate | assembly of an amphiphilic oligomer. It is a schematic diagram which shows a rod-shaped aggregate structure silica type hybrid membrane.

The present invention relates to an organic thin film transistor having at least a gate electrode, a source electrode, a drain electrode, an insulator layer, and an organic semiconductor layer on a substrate, and the insulator layer is obtained by forming an amphiphilic oligomer into a thin film. An organic thin-film transistor characterized by being a silica-based organic-inorganic hybrid film.

Hereinafter, the details of the organic TFT of the present invention will be described.
(Element structure)
The organic thin film transistor according to the present invention has an element configuration having at least a gate electrode, an insulator layer, a source electrode, a drain electrode, and an organic semiconductor layer on a substrate, and the insulator layer is obtained by hydrolytic condensation polymerization of organosilane molecules. It is composed of a silica-based organic-inorganic hybrid film obtained by forming a thin film of an amphiphilic oligomer.
1 to 3 show cross-sectional configurations of typical organic thin film transistors.
FIG. 1 shows a top contact (TC) type element structure in which a source electrode 2 and a drain electrode 3 are opposed to a substrate 6 with an organic semiconductor layer 4 interposed therebetween. The TC type organic thin film transistor has a gate electrode 1, an insulator layer 5 and an organic semiconductor layer 4 in this order on a substrate 6, and further a source electrode 2 formed on the organic semiconductor layer 4 with a predetermined interval. And a drain electrode 3. In the organic thin film transistor having such a configuration, the organic semiconductor layer 4 forms a channel region, and the current flowing between the source electrode 2 and the drain electrode 3 can be controlled by the voltage applied to the gate electrode 1. In this configuration, an organic semiconductor layer 4 is formed on a substrate on which a substrate 6 / gate electrode 1 / insulator layer 5 is formed by a solution coating process such as vacuum deposition, spin coating / dip coating / casting, and the like. Further, the source electrode 2 and the drain electrode 3 can be formed by, for example, vacuum vapor deposition using a vapor deposition mask.
FIG. 2 shows a bottom contact (BC) type device structure having an organic semiconductor layer 4 on the source electrode 2 and the drain electrode 3. The BC type organic thin film transistor first has a gate electrode 1 and an insulator layer 5 on a substrate 6, has a circuit pattern of a source electrode 2 and a drain electrode 3 thereon, and further has an organic semiconductor layer 4 thereon. Have. In this case, since a conventional photolithography method or the like can be applied to the formation of the electrode, a high-definition and large-area circuit pattern can be easily manufactured. In addition, since the organic semiconductor layer 4 is formed on a circuit pattern formed in advance, there is an advantage that the organic semiconductor material 4 is not deteriorated by physical / chemical stress accompanying electrode formation.
FIG. 3 shows a bottom contact / top gate type device structure having a source electrode 2 and a drain electrode 3, an organic semiconductor layer 4, and an insulator layer 5 in this order on a substrate 6, and a gate electrode 1 thereon. Show.

The organic thin film transistor of the present invention is characterized by the structure of the insulator layer and the manufacturing method thereof, and the element structure is shown in the top contact type shown in FIG. 1, the bottom contact type shown in FIG. It is not limited to the bottom contact / top gate type, and the organic semiconductor layer, the source electrode and the drain electrode formed so as to face each other with a predetermined interval, and the source electrode and the drain electrode respectively And a gate electrode formed at a distance, and the current flowing between the source and drain electrodes can be controlled by applying a voltage to the gate electrode. Here, the distance between the source electrode and the drain electrode is determined by the use of the organic thin film transistor of the present invention, and is usually about 0.1 μm to 1 mm, preferably 1 μm to 100 μm, more preferably 5 μm to 100 μm.

(Source electrode and drain electrode)
The source electrode and the drain electrode are not particularly limited as long as they are conductive materials such as metal materials and alloy materials generally used as source / drain electrodes in organic thin film transistors. For example, platinum, gold, silver, nickel, Chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, zinc, silver paste, lithium, beryllium, sodium, magnesium, potassium, calcium, Scandium, titanium, manganese, zirconium, gallium, niobium, sodium-potassium alloy, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / acid Aluminum mixture, a lithium / aluminum mixture, or the like is used.

Examples of the method for forming the electrode include vapor deposition, electron beam vapor deposition, sputtering, atmospheric pressure plasma, ion plating, chemical vapor deposition, electrodeposition, electroless plating, spin coating, Means such as printing or inkjet may be mentioned. Moreover, as a method of patterning as necessary, a method of forming a conductive thin film formed by using the above method using a known photolithography method or a lift-off method, on a metal foil such as aluminum or copper There is a method of forming and etching a resist by thermal transfer, ink jet, or the like. The film thickness of the electrode formed in this way is not particularly limited as long as current conduction is possible, but is preferably in the range of 0.2 nm to 10 μm, more preferably 4 nm to 300 nm. When the film thickness is 0.2 nm or more, the resistance is increased due to the thin film thickness, and a voltage drop does not occur. In addition, when the film thickness is 10 μm or less, the film formation does not take time, and when other layers such as a protective layer and an organic semiconductor layer are laminated, there is no step and the lamination can be performed smoothly.

The electrode may have a stacked structure of the metal layer and the oxide layer. Any material can be used for the oxide layer as long as it has electrical conductivity and exhibits a charge injection function with respect to the organic semiconductor layer. For _{example, GeO 2, SiO 2, MoO} 3, V 2 O 5, VO 2, V 2 O 3, MnO, Mn 3 O 4, ZrO 2, WO 3, TiO 2, In 2 O 3, ZnO, NiO, HfO ₂ , metal oxides such as Ta ₂ O ₅ , ReO ₃ and PbO ₂ are desirable. Further, GeO _x (1 ≦ x ≦ 2), SnO ₂ , PbO, ZnO, GaO, CdO, ZnOS, MgInO, CdInO, MgZnO, and the like are also suitable.
Also, oxides such as indium tin oxide (ITO), indium oxide zinc (IZO), indium tin oxide zinc (ITZO), and oxides such as Ce, Nd, Sm, Eu, Tb, Ho, etc. What added the element can also be used suitably.

The oxide layer is formed by means such as vapor deposition, electron beam vapor deposition, sputtering, atmospheric pressure plasma, ion plating, chemical vapor deposition, spin coating, dip coating, printing, or inkjet. A post-treatment such as a heat treatment is used in combination as necessary. In addition, as a method of patterning the oxide layer formed using the above method, a method using a metal mask at the time of vapor deposition or sputtering, a pattern using a known photolithographic method or a lift-off method for a formed thin film is used. There are a method of forming a pattern, a method of directly forming a pattern by ink jet or the like.
The thickness of the oxide layer thus formed is not particularly limited, but is preferably in the range of 0.2 nm to 100 nm, more preferably 1 nm to 10 nm. When the film thickness is 0.2 nm or more, the charge injection effect of the oxide layer appears. When the film thickness is 100 nm or less, the internal resistance interposed in the source / drain electrodes becomes small, and the threshold voltage tends to decrease.
Further, the metal surface may be modified for the purpose of improving the electrical contact between the electrode and the organic semiconductor layer described later. As the material for surface modification, various materials having affinity with the metal electrode and capable of surface modification by covering the metal layer, particularly materials known as self-assembled monolayer (SAMs) agents are suitable. In particular, those having end groups that can be attached to the surface of the metal layer by a coupling reaction are more preferable.
Specifically, thiophenols such as pentafluorothiophenol (PFTF), fluorothiophenol, trifluoromethylthiophenol (TFMTP), nitrothiophenol (NTP), chlorothiophenol (CTP), and methoxythiophenol (MOTP) , Pentanethiol (PT), octanethiol (OT), decanethiol (DT), alkanethiols such as stearyl mercaptan (SM), or partially fluorinated heptadecafluoro-1-decanethiol (HDFDT), Fluorinated alkanethiols such as tridecafluoro-1-octanethiol (TDFOT), and aromatic alkanethiols such as (ω- (biphenyl-4-yl) alkanethiol), but are not limited thereto.
The organic thin film layer can be formed on the metal layer by dissolving the material in a solvent such as dichloromethane or ethanol and immersing the substrate on which the metal layer is formed. The concentration of the solution is 0.1 to 100 mM, more preferably 0.1 to 10 mM. The immersion time depends on the material used and the temperature of the solution, but it is 1 minute to 24 hours, preferably 10 minutes to 6 hours at room temperature.

(Organic semiconductor layer)
The organic semiconductor used in the organic TFT of the present invention is not particularly limited. Organic semiconductors used for generally disclosed organic thin film transistors can be widely used. Examples thereof include organic semiconductor materials described in Chemical Review, 107, 1066, 2007. In the present invention, the organic semiconductor layer may be combined with a plurality of materials selected from the above organic semiconductor materials, and the plurality of materials may be mixed or stacked. Specific examples include the following, but are not limited thereto.

(1) Acenes which may have a substituent such as naphthalene, anthracene, tetracene, pentacene, hexacene, heptacene, etc. Specifically, 1,4-bisstyrylbenzene, 1,4-bis (2-methylstyryl) benzene 1,4-bis (3-methylstyryl) benzene (4MSB), 1,4-bis (4-methylstyryl) benzene, polyphenylene vinylene, etc. represented by C ₆ H ₅ —CH═CH—C ₆ H ₅ Compounds having a styryl structure, oligomers and polymers of such compounds. Further, these _{F, CF 3, C 2 F} 5 or fluorine, compounds substituted with a fluoroalkyl group.

(2) Compound containing thiophene ring i) Thiophene oligomer which may have a substituent such as α-4T, α-5T, α-6T, α-7T, α-8T derivatives, etc. ii) Polyhexylthiophene, poly Thiophene-based polymers such as (9,9-dioctylfluorenyl-2,7-diyl-co-bithiophene) iii) bisbenzothiophene derivatives, α, α'-bis (dithieno [3,2-b: 2 ' , 3′-d] thiophene), dithienothiophene-thiophene co-oligomers, condensed oligothiophenes such as pentathienoacene, particularly compounds having a thienobenzene skeleton or a dithienobenzene skeleton, and dibenzothienobenzothiophene derivatives are preferred.
A compound obtained by substituting the above compounds i to iii with a fluorine or fluoroalkyl group such as F, CF ₃ , C ₂ F ₅ or the like.

(3) Selenophen oligomer, metal-free phthalocyanine, copper phthalocyanine, lead phthalocyanine, titanyl phthalocyanine, porphyrins such as platinum porphyrin, porphyrin, benzoporphyrin, tetrathiafulvalene (TTF) and its derivatives, rubrene and its derivatives, and the like.
Further, these _{F, CF 3, C 2 F} 5 or fluorine, compounds substituted with a fluoroalkyl group.

(4) n-type organic semiconductor For example, tetracyanoquinodimethane (TCNQ), 11, 11, 12, 12-tetracyanonaphtho-2,6-quinodimethane (TCNNQ), which is known as an n-type semiconductor alone Quinoid oligomers, fullerenes such as C60, C70, PCBM and derivatives thereof, N, N′-diphenyl-3,4,9,10-perylenetetracarboxylic acid diimide, N, N′-dioctyl-3,4,9 , 10-perylenetetracarboxylic acid diimide (C8-PTCDI), N, N′-ditridecyl-3,4,9,10-perylenetetracarboxylic acid diimide (C13-PTCDI), NTCDA, 1,4,5,8- Tetracarboxylic acids such as naphthalenetetracarboxyldiimide (NTCDI), tetrathiafulvalene (TTF) and derivatives thereof .

A device having a high field effect mobility and a high on / off ratio can be obtained by using a high-purity organic semiconductor. Therefore, it is desirable to add purification by techniques such as column chromatography, recrystallization, distillation, sublimation, etc. as necessary. Preferably, it is possible to improve the purity by repeatedly using these purification methods or combining a plurality of methods. Furthermore, it is desirable to repeat sublimation purification at least twice as a final step of purification. By using these methods, it is preferable to use a material having a purity of 90% or more measured by HPLC, more preferably 95% or more, and particularly preferably 99% or more. In addition, the on / off ratio can be increased and the performance inherent to the material can be extracted.
The thickness of the organic semiconductor layer in the organic thin film transistor of the present invention is not particularly limited, but is usually 0.5 nm to 1 μm, and more preferably 2 nm to 250 nm. When the film thickness is 0.5 nm or more, a channel for transporting charges is effectively formed. If the film thickness is 1 μm or less, there will be no inconveniences such as growth of crystal grains and easy peeling.
A method for forming the organic semiconductor layer is not particularly limited, and a known method can be applied. For example, a molecular beam deposition method (MBE method), a vacuum deposition method, a chemical vapor deposition method, a dipping method in which a material is dissolved in a solvent, As described above by spin coating, casting, bar coating, roll coating, etc. printing, coating and baking, electropolymerization, molecular beam deposition, self assembly from solution, and combinations thereof. It is made of a material of an organic semiconductor layer. When the crystallinity of the organic semiconductor layer is improved, the field effect mobility is improved. Therefore, it is also effective to maintain the substrate temperature during film formation at a high temperature when film formation from the gas phase (evaporation, sputtering, etc.) is used. It is. The temperature is preferably 40 to 250 ° C., more preferably 70 to 150 ° C. Regardless of the film formation method, it is preferable to perform annealing after film formation because a high-performance device can be obtained. The annealing temperature is preferably 50 to 200 ° C., more preferably 70 to 200 ° C., and the time is preferably 10 minutes to 12 hours, more preferably 1 to 10 hours.

(Gate electrode)
As the gate electrode, in general, a thin film having conductivity and forming a film, such as a metal material, an alloy material, or a metal oxide material used as a source / drain electrode and a gate electrode in an organic thin film transistor, is widely used. it can.
Specifically, the same material as that of the source / drain electrodes can be preferably used. Particularly preferred are metals such as Au, Ag, Cu and Al, alloy materials and paste materials containing them, and oxide transparent electrodes such as ITO and IZO. The patterning of the gate electrode can also be performed by the same method as that for the source / drain electrodes.

(substrate)
The substrate in the organic thin film transistor of the present invention plays a role of supporting the structure of the organic thin film transistor. As a material, in addition to glass, inorganic compounds such as metal oxides and nitrides, plastic films (PET, PES, PC) It is also possible to use metal substrates or composites or laminates thereof. Further, when the structure of the organic thin film transistor can be sufficiently supported by the components other than the substrate, it is possible not to use the substrate. Further, a silicon (Si) wafer is often used as a material for the substrate. In this case, Si itself can be used as a gate electrode / substrate.

(Insulator layer)
The insulator layer in the organic thin film transistor of the present invention is composed of a silica-based organic-inorganic hybrid film obtained by forming an amphiphilic oligomer. The silica-based organic-inorganic hybrid film is described in A. It is described in detail in SHIMOJIMA, Journal of the Ceramic Society of Japan, 116, 278 (2008).

A typical method for producing the amphiphilic oligomer is shown below.
(Method 1 for producing amphiphilic oligomer)
A chain hydrocarbon group-containing alkoxysilane A represented by the following general formula (1-a) and a tetraalkoxysilane represented by the following general formula (2) are cohydrolyzed and polycondensed.

Wherein R ¹ is a chain hydrocarbon group having 6 or more carbon atoms, R ² is a linear or branched alkyl group having 1 to 3 carbon atoms, and R ³ and R ⁴ are each independently And a straight-chain or branched alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms.)
Si (OR ⁵ ) ₄ (2)
(In the formula, R ⁵ is a methyl group or an ethyl group.)

In the above general formula (1-a), R ¹ is preferably a chain hydrocarbon group having 6 to 18 carbon atoms, and more preferably a chain hydrocarbon group having 8 to 12 carbon atoms. When the number of carbon atoms of the chain hydrocarbon group is within the above range, self-organization is promoted during the formation of the insulator layer, and the film quality is improved. As a result, the crystal arrangement of the organic semiconductor material becomes uniform, the characteristics of the organic thin film transistor of the present invention are improved, pinholes are less likely to occur in the silica-based organic-inorganic hybrid film, and the dielectric strength is improved.
Further, the chain hydrocarbon group represented by R ¹ may be a saturated chain hydrocarbon group or an unsaturated chain hydrocarbon group. Specific examples of the saturated chain hydrocarbon group include a methylene chain represented by C _n H _{2n + 1} . Further, by making R ¹ an unsaturated chain hydrocarbon group having one or more double bonds, it is possible to give thermal polymerizability and improve film strength, or to give photopolymerizability and thereby by photolithography. Patterning can be enabled. Furthermore, for the purpose of improving the dielectric constant, a highly polar group such as —CN, —OH, —NH ₂ , —SH, and —NCO can be introduced.

The linear or branched alkyl group having 1 to 3 carbon atoms is represented by C _n H _{2n + 1} (n is an integer of 1 to 3), and specific examples thereof include a methyl group, an ethyl group, n -Propyl and isopropyl groups.
The alkoxy group having 1 to 3 carbon atoms is represented by OC _m H _{2m + 1} (m is an integer of 1 to 3), and specific examples thereof include methoxy group, ethoxy group, n-propoxy group and isopropyl group. Is mentioned.

As the chain hydrocarbon group-containing alkoxysilane A represented by the general formula (1-a), those having the following structures are preferably used.
R ¹ Si (OCH ₃ ) ₃ (1-a-1)
R ¹ Si (OCH ₂ CH ₃ ) ₃ (1-a-2)
R ¹ Si (CH ₃ ) (OCH ₃ ) ₂ (1-a-3)
R ¹ Si (CH ₃ ) ₂ (OCH ₃ ) (1-a-4)
R ¹ Si (CH ₂ CH ₃ ) (OCH ₃ ) ₂ (1-a-5)
R ¹ Si (CH ₂ CH ₃ ) ₂ (OCH ₃ ) (1-a-6)
R ¹ Si (CH ₃ ) (OCH ₂ CH ₃ ) ₂ (1-a-7)
R ¹ Si (CH ₃ ) ₂ (OCH ₂ CH ₃ ) (1-a-8)
R ¹ Si (CH ₂ CH ₃ ) (OCH ₂ CH ₃ ) ₂ (1-a-9)
R ¹ Si (CH ₂ CH ₃ ) ₂ (OCH ₂ CH ₃ ) (1-a-10)

Specific examples of the chain hydrocarbon group-containing alkoxysilane A represented by the general formula (1-a) include decyltrimethoxysilane and decyltriethoxysilane.

Specific examples of the tetraalkoxysilane represented by the general formula (2) include tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), ethoxytrimethoxysilane, diethoxymethoxysilane, and triethoxymethoxysilane. Tetramethoxysilane and tetraethoxysilane are particularly preferably used.

(Method 2 for producing amphiphilic oligomer)
The chain hydrocarbon group-containing alkoxysilane B represented by the following general formula (1-b) is hydrolyzed and polycondensed.

(Wherein R ⁶ is a chain hydrocarbon group having 6 or more carbon atoms, and R ⁷ to R ⁹ are each independently a linear or branched alkyl group having 1 to 3 carbon atoms. R ⁷ , R ⁸ and R ⁹ may be the same or different from each other.)

In the above general formula (1-b), R ⁶ is preferably a chain hydrocarbon group having 6 to 18 carbon atoms, and more preferably a chain hydrocarbon group having 10 to 16 carbon atoms. When the number of carbon atoms of the chain hydrocarbon group is within the above range, self-organization is promoted during the formation of the insulator layer, and the film quality is improved. As a result, the crystal arrangement of the organic semiconductor material becomes uniform, the characteristics of the organic thin film transistor of the present invention are improved, pinholes are less likely to occur in the silica-based organic-inorganic hybrid film, and the dielectric strength is improved.
The chain hydrocarbon group represented by R ⁶ may be a saturated chain hydrocarbon group or an unsaturated chain hydrocarbon group. Specific examples of the saturated chain hydrocarbon groups include methylene chains represented by C _m H _{2m + 1.} Further, by making R ⁶ an unsaturated chain hydrocarbon group having one or more double bonds, it is possible to give thermal polymerizability and improve film strength, or to give photopolymerizability and to perform photolithography. Patterning can be enabled. (Furthermore, a highly polar group can be introduced for the purpose of improving the dielectric constant.)
In the chain hydrocarbon group represented by R ⁶ , by setting the number of carbon atoms to 14 or more, a layered silica-based hybrid film described later is used, and by setting the carbon number to 13 or less, a rod-like aggregate structure silica-based hybrid film is formed. Obtainable.

As the chain hydrocarbon group-containing alkoxysilane B represented by the general formula (1-b), those having the following structures are preferably used.
R ⁶ Si [OSi (OCH ₃ ) ₃ ] ₃ (1-b-1)
R ⁶ Si [OSi (OC ₂ H ₅ ) ₃ ] ₃ (1-b-2)
R ⁶ Si [OSi (OCH ₃ ) ₃ ] [OSi (OC ₂ H ₅ ) ₃ ] ₂ (1-b-3)
R ⁶ Si [OSi (OCH ₃ ) ₃ ] ₂ [OSi (OC ₂ H ₅ ) ₃ ] (1-b-4)

Specific examples of the chain hydrocarbon group-containing alkoxysilane B represented by the general formula (1-b) are shown below.
C ₁₀ H ₂₁ Si [OSi (OCH ₃ ) ₃ ] ₃
C ₁₀ H ₂₁ Si [OSi (OC ₂ H ₅ ) ₃ ] ₃
C ₁₀ H ₂₁ Si [OSi (OCH ₃ ) ₃ ] [OSi (OC ₂ H ₅ ) ₃ ] ₂
C ₁₀ H ₂₁ Si [OSi (OCH ₃ ) ₃ ] ₂ [OSi (OC ₂ H ₅ ) ₃ ]
C ₈ H ₁₇ Si [OSi (OCH ₃ ) ₃ ] ₃
C ₈ H ₁₇ Si [OSi (OC ₂ H ₅ ) ₃ ] ₃
C ₈ H ₁₇ Si [OSi (OCH ₃ ) ₃ ] [OSi (OC ₂ H ₅ ) ₃ ] ₂
C ₈ H ₁₇ Si [OSi (OCH ₃ ) ₃ ] ₂ [OSi (OC ₂ H ₅ ) ₃ ]

(Silica-based organic-inorganic hybrid film)
Examples of the silica-based organic-inorganic hybrid film include (1) layered silica-based hybrid film, (2) amorphous silica-based hybrid film, and (3) rod-like aggregated-structure silica-based hybrid film described below. Is not to be done.
(1) Layered silica-based hybrid membrane A specific method for producing a layered silica-based hybrid membrane is described below.
About 1 to 20 moles (preferably 3 to 6 moles) of tetraalkoxysilane, 5 to 100 moles of THF (preferably 15 to 50 moles), 5 to 5 moles of water with respect to 1 mole of the alkoxysilane A containing chain hydrocarbon group. About 80 mol (preferably 15 to 30 mol) and HCl are mixed at 0.0001 mol or more and less than 0.1 mol (preferably 0.001 to 0.01 mol), and about 0.5 to 24 hours, preferably 1 Stir for ~ 12 hours.
Then, a chain hydrocarbon group-containing alkoxysilane A (for example, C ₁₀ H ₂₁ Si (OMe) ₃ ) and a tetraalkoxysilane (for example, Si (OMe) ₄ ) cause cohydrolysis and polycondensation, resulting in amphiphilic properties. An oligomer (eg, C ₁₀ H ₂₁ Si (OSi (OH) ₃ ) ₃ ) is formed.
This solution is diluted with THF so that the THF: Si ratio is about 1: 2 to 20 (molar ratio), preferably 1: 3 to 10 (molar ratio), and spin coating is performed using the obtained diluted solution. After the film is formed on the substrate by the method, it is dried. At this time, drying can be promoted by heating to about 40 to 120 ° C. As a solvent, ethanol or the like may be used instead of THF.
The amphiphilic oligomer formed on the substrate is self-assembled by the interaction between the hydrophilic portion and the hydrophobic portion, and as shown in FIG. 4, from the hydrophilic portion containing the silanol terminal and the chain hydrocarbon group. A layered structure is formed by alternately stacking hydrophobic portions. Here, passing through this oligomerization step is important for obtaining a uniform film. In the case of not passing through the oligomer form, phase separation occurs between the chain hydrocarbon group-containing alkoxysilane A and the tetraalkoxysilane in thinning, and a uniform film cannot be obtained.

Immediately after the film formation, the amphiphilic oligomer is in a liquid crystal state having an array structure as shown in FIG. 4, but the polycondensation of the silanol portion further progresses over time, and a siloxane network layer is formed, which is strong. A solid film is formed (see FIG. 5).
The siloxane network layer has a network structure based on a repeating unit of —Si—O—Si— siloxane bond, and the thickness thereof is a two-dimensional structure of about several silicon layers (1 to 1.5 nm). . Formation of the layer structure can be confirmed by observing a diffraction peak corresponding to the layer interval by X-ray analysis. Further, the layered structure can be directly confirmed by observation with an electron microscope.

In addition, a layered silica-based hybrid film can be obtained as follows. About 5 to 100 moles of THF (preferably with respect to 1 mole of the chain hydrocarbon group-containing alkoxysilane B represented by the general formula (1-b), wherein R ⁶ is a chain hydrocarbon group having 14 or more carbon atoms) 15 to 50 mol), about 5 to 80 mol (preferably 15 to 30 mol) of water and about 0.0001 to 0.1 mol (preferably 0.001 to 0.01 mol) of HCl and 0.5 to 0.5 mol. Stir for about 24 hours, preferably 1-12 hours.
Then, the chain hydrocarbon group-containing alkoxysilane B (for example, C ₁₆ H ₃₃ Si (OMe) ₃ ) is hydrolyzed to form an amphiphilic oligomer (for example, a compound represented by the following formula).

This solution is diluted with THF so that the THF: Si ratio is about 1: 2 to 20 (molar ratio), preferably 1: 3 to 10 (molar ratio), and spin coating is performed using the obtained diluted solution. After the film is formed on the substrate by the dip coating method or the dip coating method, it is dried. At this time, drying can be promoted by heating to about 40 to 120 ° C. As a solvent, ethanol or the like may be used instead of THF. The amphiphilic oligomer formed on the substrate is self-organized by the interaction between the hydrophilic part and the hydrophobic part, and as shown in FIG. 6, from the hydrophilic part containing the silanol terminal and the chain hydrocarbon group. A layered structure is formed by alternately stacking hydrophobic portions. Here, passing through this oligomerization step is important for obtaining a uniform film. The difference from the layered structure obtained from the chain hydrocarbon group-containing alkoxysilane A is the difference in whether the chain hydrocarbon sites are mutually nested structures.

Immediately after the film formation, the amphiphilic oligomer is in a liquid crystal state having an arrangement structure as shown in FIG. 6, but the polycondensation of the silanol portion further progresses with time, and a siloxane network layer is formed, which is strong. A solid film is formed (see FIG. 7).
Formation of the layer structure can be confirmed by observing a diffraction peak corresponding to the layer interval by X-ray analysis. Moreover, a layered structure can be confirmed by electron microscope observation.

(2) Amorphous silica-based hybrid film With respect to 1 mol of chain hydrocarbon group-containing alkoxysilane A, about 1 to 20 mol (preferably 3 to 6 mol) of tetraalkoxysilane, about 5 to 100 mol of THF (preferably 15 to 50 mol), about 5 to 80 mol (preferably 15 to 30 mol) of water and 0.1 to 5.0 mol (preferably 0.1 to 1.0 mol) of HCl and 0.5 to 24 hours. Stir to a degree, preferably 5-12 hours.
Then, a chain hydrocarbon group-containing alkoxysilane A (for example, C ₁₀ H ₂₁ Si (OMe) ₃ ) and a tetraalkoxysilane (for example, Si (OMe) ₄ ) cause cohydrolysis and polycondensation, resulting in amphiphilic properties. An oligomer (eg, C ₁₀ H ₂₁ Si (OSi (OH) ₃ ) ₃ ) is formed. Under this condition, the polycondensation of the amphiphilic oligomer proceeds to some extent at this stage, and a siloxane network is partially formed.
This solution is further diluted with THF so that the THF: Si ratio is about 1: 2 to 20 (molar ratio), preferably 1: 3 to 10 (molar ratio), and spin coating is performed using the obtained diluted solution. After the film is formed on the substrate by the method, it is dried. As the solvent, ethanol or the like may be used instead of THF. At this time, drying can be promoted by heating to about 40 to 120 ° C. Then, as shown in FIG. 8, the network siloxane network and the hydrophobic hydrocarbon chain part are partially mixed to form an amorphous layer in which the partially ordered layers are randomly stacked. In the X-ray analysis, when there is no diffraction peak corresponding to the layer spacing, it can be confirmed that the film is in an amorphous state.
After the coating film formation on the substrate, the formation of the siloxane network further progresses with time, and a solid solid film is formed.
When the above-mentioned chain hydrocarbon group-containing alkoxysilane A and tetraalkoxysilane are used, whether the finally formed film is in a layered state or an amorphous state depends on whether it is an oligomer-formed state or a partial siloxane It depends on how far the network is formed. Specifically, this progress process can be controlled by the amount of HCl added. By increasing the amount of HCl added, the formation of a partial siloxane network proceeds faster, and the finally formed film becomes amorphous. That is, as described above, a layered silica-based hybrid film is obtained by using less than 0.1 mol of HCl with respect to 1 mol of chain hydrocarbon group-containing alkoxysilane A, and amorphous by using 0.1 mol or more. A silica-based hybrid membrane is obtained.

(3) Rod-like aggregated silica-based hybrid film With respect to 1 mol of a chain hydrocarbon group-containing alkoxysilane B represented by the general formula (1-b), wherein R ⁶ is a chain hydrocarbon group having 13 or less carbon atoms About 5 to 100 mol of THF (preferably 15 to 50 mol), about 5 to 80 mol of water (preferably 15 to 30 mol) and about 0.0001 to 0.1 mol of HCl (preferably 0.001 to 0). .01 mol) and the mixture is stirred for about 0.5 to 24 hours, preferably 1 to 12 hours. Then, the chain hydrocarbon group-containing alkoxysilane B (for example, C ₁₂ H ₂₅ Si (OSi (OCH ₃ ) ₃ ) ₃ undergoes hydrolysis / condensation polymerization, and the chain hydrocarbon group-containing alkoxysilane B molecule is silanolated. Proceeds to form an amphiphilic oligomer (for example, C ₁₂ H ₂₅ Si (OSi (OH) ₃ ) ₃ ), and this solution is further added to a THF: Si ratio of about 1: 2 to 20 (molar ratio), Preferably, it is diluted with THF to a ratio of 1: 3 to 10 (molar ratio), and the resulting diluted solution is used to form a film on a substrate by spin coating, followed by drying. In this case, it is possible to promote drying by heating to about 40 to 120 ° C. In this case, the length of the tail group forming the hydrophobic group and the occupied volume are small. ,parent Since the size of the head group forming the functional group is large, the lamellar structure as in the case of the layered silica-based hybrid film of (1) cannot be taken, and the silanol parts gather to form a cylindrical wall, Finally, a rod-like ordered aggregate is formed (see Fig. 9) In this aggregate, the polycondensation of the silanol part further progresses with time, and a siloxane network layer is formed, and a solid solid film is formed. At this time, a silica skeleton having a hexagonal cross section is formed, and a thin film having a structure in which a chain hydrocarbon group is filled in the inside and the surface is formed (see FIG. 10). The diffraction peak corresponding to the repetitive period in the direction perpendicular to the substrate surface is obtained, so it can be confirmed that this form is achieved. In addition, it can be confirmed that the cross section has a hexagonal structure, and the hexagonal columnar structure is laminated so that its long axis is parallel to the substrate from SEM observation etc. I understand that.

The greatest feature of the silica-based hybrid film is that the dielectric constant is large. As will be described in detail in the examples below, the silica hybrid film is formed on a glass substrate with an ITO electrode, a laminated body in which gold is deposited using a metal mask as a counter electrode, and an LCR meter is used. When the dielectric constant was measured, it was an element having a film thickness of 500 nm and the relative dielectric constant was 6 to 8 (value at a frequency of 2 kHz). Compared with the relative dielectric constant of a typical polymer insulating film being around 3, this is a very large value. This can be said to be an unexpected property expressed by a silica-based organic-inorganic hybrid film obtained by forming an amphiphilic oligomer. This is a very desirable characteristic for an insulating film of an organic thin film transistor, which results in low voltage operation of the transistor.
Moreover, since the outermost surface of the silica-based hybrid film is covered with a chain hydrocarbon group that forms a hydrophobic site of the amphiphilic oligomer, it exhibits high water repellency. Actually, the water contact angle of ultrapure water is about 100 to 110 with respect to these film surfaces formed on a glass substrate by spin coating. Accordingly, the surface energy of these silica-based hybrid films is low, and when an organic semiconductor material is formed, it is possible to promote good crystal growth of the organic semiconductor and to exhibit excellent field effect characteristics. In order to obtain such high water repellency, it is usually necessary to use a fluorine-based polymer insulating film or to perform additional surface treatment with a SAM film or the like.
The silica-based hybrid film can be easily formed by coating with a solution, and has a high dielectric constant and high water repellency as a single film. This improves the manufacturing throughput of the insulating film for organic semiconductors and is very advantageous for cost reduction.
This invention also provides the manufacturing method of the said organic thin-film transistor which apply | coats an amphiphilic oligomer as a solution form etc. as mentioned above, and forms a silica type organic-inorganic hybrid film | membrane.

The thickness of the silica-based hybrid film is not particularly limited, but the insulating film for an organic transistor preferably has a thickness of 50 to 5000 nm, and more preferably 100 to 1500 nm. If the film thickness is less than 50 nm, the insulation is insufficient, and a leakage current is generated between the source / drain electrodes and the gate electrode, leading to deterioration of transistor characteristics. On the other hand, when the film thickness exceeds 1500 nm, the gate capacitance becomes small, and an undesirable effect such as an increase in threshold voltage is exerted.

(apparatus)
The present invention also provides an apparatus comprising the organic thin film transistor.
The device of the present invention is not particularly limited as long as it uses the above-described organic thin film transistor, and specific examples thereof include a circuit, a personal computer, a display, a mobile phone and the like.

Example 1
[Formation of insulator layer]
First, a glass substrate with an ITO transparent electrode manufactured by Geomatic was prepared. The glass substrate had a shape of 25 mm × 20 mm × 0.7 mm, an ITO film thickness of 120 nm, and ITO was processed into a stripe shape using a photolithography method, and this was used as a gate electrode. This substrate was ultrasonically cleaned in isopropyl alcohol for 5 minutes, and then UV ozone cleaning was performed for 30 minutes.
Decyltrimethoxysilane (C ₁₀ H ₂₁ Si (OMe) ₃ ), tetramethoxysilane (Si (OMe) ₄ ), tetrahydrofuran (THF), water, HCl in a molar ratio of 1: 4: 15: 19: 0 The mixture was mixed at 0.002 and stirred at room temperature for 6 hours to prepare an amphiphilic oligomer solution. This amphiphilic oligomer solution was applied on the above glass substrate using a spin coating method (3000 rpm, 10 seconds), and then dried at room temperature for 1 day to form an insulator layer. Under the same conditions, an insulator layer was formed on a plurality of substrates, and the following insulator layer evaluation and organic thin film transistor element production were performed.
As a result of the following X-ray analysis and transmission electron microscope observation, it was found that the insulator layer had a layered structure with a layer interval of about 3.3 nm.

[Evaluation of insulator layer]
The following measurements were performed on the insulator layer formed as described above. The results are shown in Table 1.
(Film thickness measurement)
The film thickness of the insulator layer was measured with a stylus type film thickness meter (ET3000, manufactured by Kosaka Laboratory).
(Surface roughness measurement)
Moreover, the surface roughness (RMS) of a 10 micrometer square area | region was measured using AFM (made by SII nanotechnology company).
(Water contact angle)
Using a water contact angle meter (DropMaster 500, manufactured by Kyowa Interface Science Co., Ltd.), the water contact angle of the surface of the insulating film with respect to ultrapure water was measured.
(Relative permittivity)
Using a vapor deposition method, a gold electrode (with a thickness of 80 nm) is formed on the insulator layer through a metal mask, and is opposed to the ITO electrode with the insulator layer interposed therebetween. An LCR meter (HP4284A, manufactured by Hewlett-Packard Company) ) Was used to measure the dielectric constant of the insulator layer at a frequency of 2 kHz.
(X-ray analysis)
X-ray analysis was performed using M03X-HF (manufactured by Bruker AXS), and the interlayer distance of the layered silica-based hybrid film or the repetition period distance of the rod-like aggregated structure silica-based hybrid film was derived from the diffraction peak position. Those having no peak corresponding to these distances were made amorphous.
(Transmission electron microscope observation)
Observation was performed using JEOL JEM2010 (manufactured by JEOL Ltd.).

[Manufacture of organic thin-film transistors]
The substrate on which the insulator layer is formed as described above is placed in a vacuum deposition apparatus (EX-400, manufactured by ULVAC), and pentacene is deposited to a film thickness of 50 nm at a deposition rate of 0.05 nm / s. Thus, an organic semiconductor layer was formed. Further, through a metal mask, gold was deposited at a deposition rate of 0.05 nm / s to a film thickness of 50 nm to obtain a top contact type organic thin film transistor element as a source electrode and a drain electrode (see FIG. 1). The electrodes were set to have a gap (channel length L) of 75 μm and a width (channel width W) of 5 mm.
A gate voltage of 0 to −100 V was applied to the gate electrode of the obtained organic thin film transistor, and a current was applied by applying a voltage between the source and drain electrodes. In this case, holes were induced in the channel region (between the source and drain electrodes) of the organic semiconductor layer and operated as a p-type transistor.
Using the following formula (A), the field effect mobility μ and the threshold voltage V _T were calculated to be 5.0 cm ^{2 /} Vs and +4.0 V, respectively. Compared to an element using a parylene insulator layer (Comparative Example 1, which will be described later), the mobility was high and the threshold voltage was low. The results are shown in Table 1.
I _D = (W / 2L) · Cμ · (V _G −V _T ) ² (A)
(Where _ID is the source-drain current, W is the channel width, L is the channel length, C is the capacitance per unit area of the gate insulator layer, V _T is the gate threshold voltage, and V _G is the gate voltage. is there.)

Example 2
An organic thin film transistor was manufactured by forming an insulating layer in the same manner as in Example 1 except that the insulating layer was formed as follows.
The amphiphilic oligomer solution prepared in the same manner as in Example 1 was further diluted with THF so that the THF: Si ratio was 40: 5 (molar ratio). This diluted amphiphilic oligomer solution was applied on a glass substrate using a spin coating method (3000 rpm, 10 seconds), and then dried at room temperature for 1 day to form an insulating layer.
The insulator layer and the organic thin film transistor were evaluated in the same manner as in Example 1. The results are shown in Table 1. As a result of X-ray analysis and transmission electron microscope observation, it was found that the insulator layer had the same layered structure as in Example 1.

Example 3
An organic thin film transistor was manufactured by forming an insulating layer in the same manner as in Example 1 except that the insulating layer was formed as follows.
Decyltrimethoxysilane, tetramethoxysilane, THF, water and HCl were mixed at a molar ratio of 1: 4: 15: 19: 0.2 and stirred at room temperature for 6 hours to prepare an amphiphilic oligomer solution. . This solution was further diluted with THF so that the THF: Si ratio was 40: 5 (molar ratio). This diluted amphiphilic oligomer solution was applied on the previous glass substrate using a spin coating method (3000 rpm, 10 seconds) and then dried at room temperature for 1 day to form an insulator layer.
The insulator layer and the organic thin film transistor were evaluated in the same manner as in Example 1. The results are shown in Table 1. As a result of X-ray analysis, it was found that the insulator layer was in an amorphous state having no long-range structure.

Example 4
An organic thin film transistor was manufactured by forming an insulating layer in the same manner as in Example 1 except that the insulating layer was formed as follows.
Dodecyltris (trimethoxysiloxy) silane, THF, water, and HCl were mixed at a molar ratio of 1: 50: 18: 0.002 and stirred at room temperature for 6 hours to prepare an amphiphilic oligomer solution. This amphiphilic oligomer solution was further diluted with water so that the water: Si ratio was 50: 4 (molar ratio). This solution was applied on the above glass substrate using a spin coating method (3000 rpm, 10 seconds), and then dried at room temperature for 1 day to form an insulator layer.
The insulator layer and the organic thin film transistor were evaluated in the same manner as in Example 1. The results are shown in Table 1. Also, X-ray analysis and transmission electron microscope observation revealed that this insulator layer has a rod-like aggregate structure.

Example 5
Except that 1,4-bis (3-methylstyryl) benzene (4MSB) was used as the organic semiconductor material, an insulator layer was formed and an organic thin film transistor was manufactured and evaluated in the same manner as in Example 1. did. The evaluation results are shown in Table 1.

Example 6
Except for using 4MSB as the organic semiconductor material, an insulator layer was formed and an organic thin film transistor was manufactured and evaluated in the same manner as in Example 2. The evaluation results are shown in Table 1.

Example 7
Except for using 4MSB as the organic semiconductor material, an insulator layer was formed and an organic thin film transistor was manufactured and evaluated in the same manner as in Example 3. The evaluation results are shown in Table 1.

Example 8
An insulator layer was formed and an organic thin film transistor was manufactured and evaluated in the same manner as in Example 4 except that 4MSB was used as the organic semiconductor material. The evaluation results are shown in Table 1.

Comparative Example 1
An organic thin film transistor was manufactured in the same manner as in Example 1 except that the insulator layer was formed as follows.
A glass substrate with ITO prepared and cleaned in the same manner as in Example 1 was set in a film forming section of a thermal CVD apparatus. On the other hand, in the raw material evaporation section, 250 mg of polyparaxylene derivative [polyparaxylene chloride (parylene)] (trade name; diX-C, manufactured by Sansei Kasei Co., Ltd.) is placed in a petri dish as a raw material for the insulator layer. did. The thermal CVD apparatus was evacuated with a vacuum pump and depressurized to 5 Pa, and then the evaporation part was heated to 180 ° C. and the polymerization part was heated to 680 ° C. and left for 2 hours to form an insulator layer having a thickness of 800 nm on the gate electrode. .
The insulator layer and the organic thin film transistor were evaluated in the same manner as in Example 1. The results are shown in Table 1. As a result of X-ray analysis, a weak diffraction peak due to the parylene crystal was observed, but a clear structure such as a layer structure was not observed.

Comparative Example 2
Except that 4MSB was used as the organic semiconductor material, an insulator layer was formed and an organic thin film transistor was manufactured and evaluated in the same manner as in Comparative Example 1. The evaluation results are shown in Table 1.

As described in detail above, the organic TFT of the present invention is useful as a transistor because it has high mobility and low threshold voltage.

1: Gate electrode 2: Source electrode 3: Drain electrode 4: Organic semiconductor layer 5: Insulator layer 6: Substrate

Claims (9)

1. An organic thin film transistor having at least a gate electrode, a source electrode, a drain electrode, an insulator layer, and an organic semiconductor layer on a substrate, wherein the insulator layer is a chain hydrocarbon represented by the following general formula (1-a) Silica-based organic-inorganic hybrid obtained by forming a thin film of an amphiphilic oligomer obtained by cohydrolysis and condensation polymerization of a group-containing alkoxysilane A and a tetraalkoxysilane represented by the following general formula (2) An organic thin film transistor characterized by being a film.
   

   

   Wherein R ¹ is a chain hydrocarbon group having 6 or more carbon atoms, R ² is a linear or branched alkyl group having 1 to 3 carbon atoms, and R ³ and R ⁴ are each independently And a straight-chain or branched alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms.)
   Si (OR ⁵ ) ₄ (2)
   (In the formula, R ⁵ is a methyl group or an ethyl group.)
2. An organic thin film transistor having at least a gate electrode, a source electrode, a drain electrode, an insulator layer, and an organic semiconductor layer on a substrate, wherein the insulator layer is a chain hydrocarbon represented by the following general formula (1-b) An organic thin film transistor characterized by being a silica-based organic-inorganic hybrid film obtained by forming a thin film of an amphiphilic oligomer obtained by hydrolysis / condensation polymerization of a group-containing alkoxysilane B.
   

   

   (Wherein R ⁶ is a chain hydrocarbon group having 6 or more carbon atoms, and R ⁷ to R ⁹ are each independently a linear or branched alkyl group having 1 to 3 carbon atoms. R ⁷ , R ⁸ and R ⁹ may be the same or different from each other.)
3. The organic thin-film transistor according to claim 1 or 2, wherein the silica-based organic-inorganic hybrid film is a layered silica-based hybrid film.
4. 3. The organic thin-film transistor according to claim 1, wherein the silica-based organic-inorganic hybrid film is an amorphous silica-based hybrid film.
5. 3. The organic thin film transistor according to claim 2, wherein the silica-based organic-inorganic hybrid film is a rod-like aggregated-structure silica-based hybrid film.
6. 3. The organic thin film transistor according to claim 2, wherein R ⁶ in the general formula (1-b) is a chain hydrocarbon group having 14 to 18 carbon atoms, and the silica-based organic-inorganic hybrid film is a layered silica-based hybrid film.
7. 3. The organic material according to claim 2, wherein R ⁶ in the general formula (1-b) is a chain hydrocarbon group having 6 to 13 carbon atoms, and the silica-based organic-inorganic hybrid film is a rod-like aggregate structure silica-based hybrid film. Thin film transistor.
8. 3. The method for producing an organic thin film transistor according to claim 1, wherein an amphiphilic oligomer is applied to form a silica-based organic-inorganic hybrid film.
9. An apparatus comprising the organic thin film transistor according to claim 1.

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