JP2011119435A - Field effect transistor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain high mobility and a high on/off ratio, in a field effect transistor with a semiconductor layer containing a CNT on a substrate formed of an organic polymer compound. <P>SOLUTION: The field effect transistor includes a substrate formed of the organic polymer compound, a gate electrode, a gate insulating layer, the semiconductor layer, and a source electrode, and a drain electrode where the semiconductor layer contains a carbon nanotube composite having a conjugate polymer stuck on at least a part of the surface thereof. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a field effect transistor having a semiconductor layer containing carbon nanotubes on a substrate made of an organic polymer compound and a method for manufacturing the same.

  In recent years, field effect transistors (hereinafter referred to as FETs) using carbon nanotubes (hereinafter referred to as CNTs) having high mobility and excellent flexibility have attracted attention. CNTs tend to aggregate and usually exist in the form of bundles (CNT bundles), but it has been found that CNTs can be uniformly dispersed in a solution by irradiating ultrasonic waves in the presence of a dispersant. By using a CNT dispersion liquid in which CNTs are uniformly dispersed, circuit patterns can be formed directly on the substrate by inkjet technology, screening technology, etc., realizing low-cost and high-mobility FETs Research is being actively promoted as a leading technology.

  On the other hand, in order to realize the coming ubiquitous information society, the development of electronic devices that are more familiar and easy to use is being promoted. In particular, flexible electronic devices such as flexible displays are being researched as next-generation electronic devices because they are light, bent, and difficult to break. As a substrate for a flexible electronic device, a substrate made of an organic polymer compound such as polyethylene terephthalate (hereinafter referred to as PET) that is transparent, light, and highly flexible has been widely studied, but has a low glass transition temperature and a process temperature. Therefore, there are problems such as limited materials that can be used and difficulty in obtaining high performance. For example, since a conventional silicon semiconductor thin film requires a high-temperature process exceeding 300 ° C., it is difficult to manufacture on a flexible substrate made of an organic polymer compound. Therefore, in order to fabricate an FET on a flexible substrate, a semiconductor material that exhibits high performance (particularly mobility) in a relatively low temperature process is highly desired.

  Since organic semiconductors can be manufactured by a coating method that is a flexible and low-temperature process, research has been widely conducted as a semiconductor material for flexible FETs (see, for example, Non-Patent Document 1). However, there are few coating type organic semiconductors that exhibit high mobility, and many coating type organic semiconductors that exhibit high mobility require high-temperature annealing at 150 ° C. or higher (see, for example, Non-Patent Document 2).

  As another method for forming a semiconductor layer on a flexible substrate, an example using a uniform dispersion of CNTs is disclosed (for example, see Non-Patent Document 3). However, since a non-conjugated long-chain alkyl dispersant is used as the dispersant, high mobility has not been obtained.

Appl. Phys. Lett. , 2007, Vol. 90, p. 053504 J. et al. Am. Chem. Soc. , 2002, Vol. 124, no. 30, P.I. 8812-8813 Nano Letters, 2005, Vol. 5, no. 4, P. 757-760

  An object of the present invention is to achieve a high mobility and a high on / off ratio in a field effect transistor having a semiconductor layer on a substrate made of an organic polymer compound.

  The present invention relates to a field effect transistor having a substrate made of an organic polymer compound, a gate electrode, a gate insulating layer, a semiconductor layer, a source electrode, and a drain electrode, wherein the semiconductor layer has a conjugated weight on at least a part of its surface. It is a field effect transistor containing a carbon nanotube composite to which a coalescence is attached.

  According to the present invention, it is possible to provide a flexible field-effect transistor that exhibits high mobility and high on / off ratio.

Schematic sectional view showing an example of the FET of the present invention Schematic sectional view showing another example of the FET of the present invention

  The FET of the present invention will be described. The FET of the present invention is an FET in which a semiconductor layer is formed on a substrate made of an organic polymer compound, and the semiconductor layer is a CNT composite (hereinafter referred to as CNT) in which a conjugated polymer is attached to at least a part of the surface. (Referred to as a composite). By using a substrate made of an organic polymer compound that is excellent in flexibility and workability, a flexible display or the like becomes possible. On the other hand, since the process temperature is limited, it is difficult to obtain high mobility. The present invention enables high mobility and on / off ratio at a relatively low process temperature by forming a semiconductor layer containing a CNT complex on a substrate made of an organic polymer compound. This is because CNT has extremely high conductivity and does not require alignment control by heat treatment after coating, and by attaching a conjugated polymer that does not inhibit conductivity on the surface of CNT, This is because the uniform dispersion of CNTs was realized.

  1 and 2 are schematic sectional views showing examples of the FET of the present invention. In FIG. 1, a source electrode 5 and a drain electrode 6 are formed on a substrate 1 made of an organic polymer compound having a gate electrode 2 covered with a gate insulating layer 3, and a semiconductor containing a CNT composite is further formed thereon. Layer 4 is formed. In FIG. 2, a semiconductor layer 4 containing a CNT complex is formed on a substrate 1 made of an organic polymer compound having a gate electrode 2 covered with a gate insulating layer 3, and further a source electrode 5 and a drain are formed thereon. An electrode 6 is formed.

  The material used for the substrate 1 is not particularly limited as long as it is an organic polymer compound, but polyester such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone, polycarbonate, polyamide, polyimide, polyethylene, polyphenylene sulfide, polyparaxylene or Any of these derivatives and the like can be mentioned. In particular, polyesters, polyether sulfones, polycarbonates, polyamides, polyimides, or any derivatives thereof that are excellent in transparency, flexibility, and processability are preferable. Furthermore, from the viewpoint of cost, polyester or a derivative thereof is more preferable. There is no restriction | limiting in particular in the thickness of a board | substrate, A required thickness can be selected according to a use. In addition, for the purpose of enhancing the properties as a substrate such as transparency, flatness, and environmental resistance, one or more organic and / or inorganic thin films may be formed on the surface of the substrate.

  Examples of materials used for the gate electrode 2, the source electrode 5, and the drain electrode 6 include conductive metal oxides such as tin oxide, indium oxide, and indium tin oxide (ITO), platinum, gold, silver, copper, iron, Inorganic conductivity such as tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium, magnesium, palladium, molybdenum, metals such as amorphous silicon and polysilicon, alloys thereof, copper iodide, copper sulfide Examples include, but are not limited to, materials, polythiophene, polypyrrole, polyaniline, and a conductive polymer whose conductivity is improved by doping with iodine or the like, such as a complex of polyethylenedioxythiophene and polystyrenesulfonic acid. A plurality of materials may be laminated or mixed.

  The material used for the gate insulating layer 3 is not particularly limited, but inorganic materials such as silicon oxide and alumina, polyimide and derivatives thereof, polyvinyl alcohol, polyvinyl chloride, polyethylene terephthalate, polyvinylidene fluoride, polysiloxane and derivatives thereof, polyvinyl Examples thereof include organic polymer compounds such as phenol and derivatives thereof, mixtures of inorganic compound powders and organic polymer compounds, and mixtures of organic low molecular compounds and organic polymer compounds. In the present invention, the organic polymer compound indicates an organic compound having a molecular weight exceeding 3000, and the organic low molecular compound indicates an organic compound having a molecular weight of 3000 or less. The film thickness of the gate insulating layer 3 is preferably 50 nm to 3 μm, more preferably 100 nm to 1 μm. The gate insulating layer 3 may be a single layer or a plurality of layers. In addition, one layer may be formed from a plurality of insulating materials, or a plurality of insulating materials may be stacked.

  The semiconductor layer 4 in the present invention contains at least a CNT composite. By including a highly conductive CNT composite in the semiconductor layer, a high mobility FET can be obtained. Furthermore, since the conjugated polymer is attached to at least a part of the surface of the CNT, the CNT can be more uniformly dispersed on the substrate, and the mobility can be further improved and a high on / off ratio can be realized. The state in which the conjugated polymer is attached to at least a part of the CNT surface means a state in which a part or all of the CNT surface is covered with the conjugated polymer. The reason why the conjugated polymer can coat the CNT is presumed to be that an interaction occurs due to the overlap of π electron clouds derived from the respective conjugated structures. Whether or not the CNT is coated with the conjugated polymer can be determined by approaching the color of the conjugated polymer from the color of the uncoated CNT. Quantitatively, the presence of deposits and the weight ratio of deposits to CNTs can be identified by elemental analysis or X-ray photoelectron spectroscopy (XPS). In addition, the conjugated polymer attached to the CNT can be used regardless of the molecular weight, molecular weight distribution, or structure.

  The method for attaching the conjugated polymer to the CNT is as follows: (I) a method in which CNT is added and mixed in the molten conjugated polymer, and (II) the conjugated polymer is dissolved in a solvent, and the CNT is added to the CNT. (III) A method in which a conjugated polymer is added and mixed in a place where CNT has been pre-dispersed in a solvent in advance using ultrasonic waves, and (IV) a conjugated polymer in the solvent. And CNT, and a method of mixing the mixed system by irradiating ultrasonic waves. In the present invention, a plurality of methods may be combined.

  In the present invention, the CNT used in the CNT composite is a single-layer CNT in which one carbon film (graphene sheet) is wound in a cylindrical shape, and two layers in which two graphene sheets are wound in a concentric shape. Either CNT or multilayer CNT in which a plurality of graphene sheets are concentrically wound may be used, or two or more of these may be used. CNTs can be obtained by methods such as arc discharge, chemical vapor deposition (CVD), and laser ablation.

  In the present invention, the length of the CNT is preferably shorter than the distance (channel length) between the source electrode and the drain electrode. The average length of CNT depends on the channel length, but is preferably 5 μm or less, more preferably 2 μm or less. In general, commercially available CNTs have a distribution in length and may contain CNTs longer than the channel length, and therefore it is preferable to add a step of shortening the CNTs shorter than the channel length. For example, a method of cutting into short fibers by acid treatment with nitric acid, sulfuric acid or the like, ultrasonic treatment, or freeze pulverization is effective. Further, it is more preferable to use separation by a filter in view of improving purity.

  Moreover, the diameter of CNT is not specifically limited, However, 1 nm or more and 100 nm or less are preferable, More preferably, it is 50 nm or less.

  In the present invention, it is preferable to provide a step of uniformly dispersing CNT in a solvent and filtering the dispersion with a filter. By obtaining CNT smaller than the filter pore diameter from the filtrate, CNT shorter than the channel length can be obtained efficiently. In this case, a membrane filter is preferably used as the filter. The pore diameter of the filter used for filtration should just be smaller than channel length, and 0.5-10 micrometers is preferable.

  Other methods for shortening CNT include acid treatment, freeze pulverization treatment, and the like.

  Examples of the conjugated polymer that coats the CNT include a polythiophene polymer, a polypyrrole polymer, a polyaniline polymer, a polyacetylene polymer, a poly-p-phenylene polymer, and a poly-p-phenylene vinylene polymer. Examples thereof include a thiophene-heteroarylene polymer having a combination, a thiophene unit and a heteroaryl unit in the repeating unit, and two or more of these may be used. The polymer may be a single monomer unit arranged, a block copolymer of different monomer units, a random copolymer, a graft polymer or the like, but the thiophene skeleton is a repeating unit. It is preferable to include in. Among these, a polythiophene polymer and a thiophene-heteroarylene polymer that are easily attached to the CNT and easily form a CNT complex are particularly preferably used.

  As the polythiophene polymer, one having a side chain in a polymer having a poly-thiophene skeleton is preferable. Specific examples include poly-3-alkylthiophene (alkyl group) such as poly-3-methylthiophene, poly-3-butylthiophene, poly-3-hexylthiophene, poly-3-octylthiophene, poly-3-dodecylthiophene, and the like. Is preferably 1-12); poly-3-alkoxythiophene such as poly-3-methoxythiophene, poly-3-ethoxythiophene, poly-3-dodecyloxythiophene (the carbon number of the alkoxy group is preferably 1) -12); poly-3-alkoxy-4-alkylthiophene such as poly-3-methoxy-4-methylthiophene, poly-3-dodecyloxy-4-methylthiophene (the number of carbons of the alkoxy group and the alkyl group is preferably 1-12); poly-3-thiohexylthiophene and poly-3-thiodode Poly-3-thio-alkylthiophene such as Le thiophene (number of carbon atoms in the alkyl group is preferably 1 to 12) are exemplified, can be used singly or in combination. Among these, poly-3-alkylthiophene or poly-3-alkoxythiophene is preferable. As the former, poly-3-hexylthiophene is particularly preferable. The preferred molecular weight of the polythiophene polymer is 800 to 100,000 in terms of number average molecular weight. Further, the polymer need not necessarily have a high molecular weight, and may be an oligomer composed of a linear conjugated system.

  Examples of the thiophene-heteroarylene polymer include poly {(9,9-dioctylfluorene) -2,7-diyl-alt- [4,7-bis (3-decyloxythien-2-yl) -2,1. , 3-Benzothiadiazole] -5 ′, 5′-diyl}, poly {[4,7-bis (4,4′-dihexylbithiophen-2-yl) -2,1,3-benzothiadiazole] -5 Thiophene-benzothiadiazole-based polymers such as', 5'-diyl}, poly {(9,9-dioctylfluorene) -2,7-diyl-alt- [5,8-di-2-thienyl-2,3 -Bis (3-octyloxyphenyl) quinoxaline)]-5 ′, 5′-diyl} and the like, poly {5,7-di-2-thienyl-2,3-bis (3 5-di (2-ethyl) Hexyloxy) phenyl) thiophene such as thieno [2,4-b] pyrazine} - Chienopirajin polymer and the like.

  As a method for removing impurities from the conjugated polymer used in the present invention, a reprecipitation method, a Soxhlet extraction method, a filtration method, an ion exchange method, a chelate method, or the like can be used. In particular, when removing low molecular weight components, a reprecipitation method or Soxhlet extraction method is preferably used, and for removing metal components, a reprecipitation method, a chelate method, or an ion exchange method is preferably used. Two or more of these methods may be combined.

  Further, the semiconductor layer 4 may include an organic semiconductor, an insulating material, and the like in addition to the CNT composite as long as the conductivity of the CNT is not impaired. The organic semiconductor is not particularly limited, and specifically, polythiophenes such as poly-3-hexylthiophene and polybenzothiophene, polypyrroles, and poly (p-phenylenevinylene) s such as poly (p-phenylenevinylene), Polyanilines, polyacetylenes, polydiacetylenes, polycarbazoles, polyfurans such as polyfuran and polybenzofuran, polyheteroaryls having nitrogen-containing aromatic rings such as pyridine, quinoline, phenanthroline, oxazole and oxadiazole, Condensed polycyclic aromatic compounds such as anthracene, pyrene, naphthacene, pentacene, hexacene, rubrene, furan, thiophene, benzothiophene, dibenzofuran, pyridine, quinoline, phenanthroline, oxazole, oxadia Nitrogen-containing aromatic compounds such as alcohol, aromatic amine derivatives represented by 4,4′-bis (N- (3-methylphenyl) -N-phenylamino) biphenyl, bis (N-allylcarbazole) or bis Biscarbazole derivatives such as (N-alkylcarbazole), pyrazoline derivatives, stilbene compounds, hydrazone compounds, metal phthalocyanines such as copper phthalocyanine, metal porphyrins such as copper porphyrin, distyrylbenzene derivatives, aminostyryl derivatives, aromatic Acetylene derivatives, naphthalene-1,4,5,8-tetracarboxylic acid diimide, condensed ring tetracarboxylic acid diimides such as perylene-3,4,9,10-tetracarboxylic acid diimide, merocyanine, phenoxazine, rhodamine, etc. Examples include organic dyes. It is.

  Examples of the insulating material include, but are not limited to, organic polymer materials such as poly (methyl methacrylate), polycarbonate, and polyethylene terephthalate.

  The semiconductor layer 4 may be a single layer or a plurality of layers, and a plurality of layers containing a CNT composite may be laminated, or a layer containing a CNT composite and a layer made of a known organic semiconductor may be laminated. . The thickness of the semiconductor layer 4 is preferably 1 nm to 200 nm, and preferably 5 nm to 100 nm. By setting the film thickness in this range, it is easy to form a uniform thin film, and further, the source-drain current that cannot be controlled by the gate voltage can be suppressed, and the on / off ratio of the FET can be further increased. The film thickness can be measured by an atomic force microscope or an ellipsometry method.

  In the present invention, a second insulating layer may be provided on the side opposite to the gate insulating layer 3 with respect to the semiconductor layer 4 containing at least the CNT composite. Here, the side opposite to the gate insulating layer with respect to the semiconductor layer indicates, for example, the lower side of the semiconductor layer when the gate insulating layer is provided on the upper side of the semiconductor layer. Thereby, threshold voltage and hysteresis can be reduced, and a high-performance FET can be obtained. The material used for the second insulating layer is not particularly limited, but specifically, inorganic compounds such as silicon oxide and alumina, polyimide and derivatives thereof, polyvinyl alcohol, polyvinyl chloride, polyethylene terephthalate, polyvinylidene fluoride, polysiloxane and the like Examples thereof include organic polymer compounds such as derivatives, polyvinylphenol and derivatives thereof, mixtures of inorganic compound powders and organic polymer compounds, and mixtures of organic low molecular compounds and organic polymer compounds. Among these, it is preferable to use an organic polymer compound that can be prepared by a coating method such as inkjet. Especially when polyfluoroethylene, polynorbornene, polysiloxane, polyimide, polystyrene, polycarbonate or derivatives thereof, polyacrylic acid derivatives, polymethacrylic acid derivatives, or copolymers containing these are used, threshold voltage and hysteresis are reduced. A polyacrylic acid derivative, a polymethacrylic acid derivative, or a copolymer containing these is particularly preferable because the effect is greater.

  The film thickness of the second insulating layer is generally 50 nm to 10 μm, preferably 100 nm to 3 μm. The second insulating layer may be a single layer or a plurality of layers. In addition, one layer may be formed from a plurality of insulating materials, or a plurality of insulating materials may be stacked.

  The method for producing an FET of the present invention includes forming a gate electrode, a gate insulating layer, a semiconductor layer, a source electrode, and a drain electrode on a polymer substrate, and the step of forming the semiconductor layer includes: A step of applying a semiconductor solution containing a carbon nanotube composite having a conjugated polymer attached to at least a part of the surface, and a step of heat treatment at a temperature of 150 ° C. or lower.

  Examples of the method for forming the gate electrode, source electrode, and drain electrode include resistance heating vapor deposition, electron beam beam, sputtering, plating, CVD, ion plating coating, ink jet, and printing. Not. As an electrode pattern forming method, the electrode thin film prepared by the above method may be formed into a desired shape by a known photolithography method, or a mask having a desired shape may be formed at the time of electrode material vapor deposition or sputtering. A pattern may be formed through the pattern.

  The method for forming the gate insulating layer is not particularly limited, and it is possible to use a dry method such as resistance heating vapor deposition, electron beam, sputtering, and CVD, but from the viewpoint of manufacturing cost and adaptability to a large area, It is preferable to use a coating method. Specifically, as a coating method, a spin coating method, a blade coating method, a slit die coating method, a screen printing method, a bar coater method, a mold method, a printing transfer method, a dip pulling method, an ink jet method, a drop cast method, or the like is preferably used. The coating method can be selected according to the characteristics of the coating film to be obtained, such as coating film thickness control and orientation control. The formed coating film may be annealed in the air, under reduced pressure, or in an inert gas atmosphere (in a nitrogen or argon atmosphere). In the case where the second insulating layer is included, the second insulating layer can be formed by a similar method.

  As a method for forming the semiconductor layer, dry methods such as resistance heating vapor deposition, electron beam, sputtering, and CVD can be used. However, from the viewpoint of manufacturing cost and adaptability to a large area, a CNT composite is contained. The method of apply | coating a semiconductor solution and heat-processing at the temperature of 150 degrees C or less is preferable. By heat-treating at a temperature of 150 ° C. or lower, the substrate material can be selected from many organic polymer compounds, which makes it possible to select a substrate according to required properties such as cost, transparency, and flexibility. Become.

  Examples of the coating method include those exemplified as the method for forming the gate insulating layer, and the coating method can be selected according to the properties of the coating film to be obtained, such as coating thickness control and orientation control. In the present invention, the solvent of the semiconductor solution containing the CNT complex includes tetrahydrofuran, toluene, xylene, 1,2,3-trimethylbenzene, 1,2,3,5-tetramethylbenzene, 1,2,3,5. -Tetramethylbenzene, 1,3-diethylbenzene, 1,4-diethylbenzene, 1,3,5-triethylbenzene, 1,3-diisopropylbenzene, 1,4-isopropylbenzene, 1,4-dipropylbenzene, butylbenzene , Isobutylbenzene, 1,3,5-triisopropylbenzene, dichloromethane, dichloroethane, chloroform, chlorobenzene, dichlorobenzene, o-chlorotoluene, 1,2-dihydronaphthalene, 1,2,3,4-tetrahydronaphthalene, benzoic acid Ethyl, 2,4,6-trimethylbenzo Ethyl, ethyl 2-ethoxy benzoic acid, o- toluidine, m- toluidine and p- toluidine and the like. Two or more of these solvents may be used. In addition, the formed coating film may be annealed in the air, under reduced pressure, or in an inert gas atmosphere (in a nitrogen or argon atmosphere).

  In the FET formed as described above, the current flowing between the source electrode and the drain electrode can be controlled by changing the gate voltage. The mobility μ of the FET can be calculated using the following equation (a).

μ = (δId / δVg) L · D / (W · ε r · ε · Vsd) (a)
Where Id is the source-drain current (A), Vsd is the source-drain voltage (V), Vg is the gate voltage (V), D is the thickness of the gate insulating layer (m), and L is the channel length (m ), W is the channel width (m), ε _r is the dielectric constant of the gate insulating layer, and ε is the dielectric constant of vacuum (8.85 × 10 ⁻¹² F / m).

  Further, the on / off ratio can be obtained from the ratio of the value of Id (on current) at a certain negative gate voltage to the value of Id (off current) at a certain positive gate voltage.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited by these Examples.

In addition, the average molecular weight (number average molecular weight, weight average molecular weight) was calculated by an absolute calibration curve method using a GPC apparatus (manufactured by TOSOH Co., Ltd., to which chloroform was fed, high-speed GPC apparatus HLC-8220 GPC). The degree of polymerization n was calculated by the following formula.
Degree of polymerization n = [(weight average molecular weight) / (molecular weight of one monomer unit)].

Synthesis example 1
A conjugated polymer [WP-BT1] was synthesized as follows.

  2.0 g of 4,7-dibromo-2,1,3-benzothiadiazole and 4.3 g of bis (pinacolato) diboron are added to 40 ml of 1,4-dioxane, and 4.0 g of potassium acetate, [bis ( Diphenylphosphino) ferrocene] dichloropalladium (1.0 g) was added, and the mixture was stirred at 80 ° C. for 8 hours. 200 ml of water and 200 ml of ethyl acetate were added to the resulting solution, and the organic layer was separated, washed with 400 ml of water, and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: dichloromethane / ethyl acetate) and 4,7-bis (4,4,5,5-tetramethyl- [1,3,2] 1.3 g of dioxaborolan-2-yl) -2,1,3-benzothiadiazole was obtained.

  Next, 18.3 g of 2-bromo-3-hexylthiophene was dissolved in 250 ml of tetrahydrofuran and cooled to -80 ° C. After adding 45 ml of n-butyllithium (1.6M hexane solution), the temperature was raised to −50 ° C. and cooled again to −80 ° C. 2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (18.6 ml) was added, the temperature was raised to room temperature, and the mixture was stirred under a nitrogen atmosphere for 6 hours. 200 ml of 1N aqueous ammonium chloride and 200 ml of ethyl acetate were added to the resulting solution, and the organic layer was separated, washed with 200 ml of water, and then dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: hexane / dichloromethane) to give 2- (4,4,5,5-tetramethyl- [1,3,2] dioxaborolan-2-yl. ) -3-hexylthiophene (16.66 g) was obtained.

  Next, 2.52 g of the 2-bromo-3-hexylthiophene and the 2- (4,4,5,5-tetramethyl- [1,3,2] dioxaborolan-2-yl) -3-hexylthiophene 3.0 g was added to 100 ml of dimethylformamide, 13 g of potassium phosphate and 420 mg of [bis (diphenylphosphino) ferrocene] dichloropalladium were added under a nitrogen atmosphere, and the mixture was stirred at 90 ° C. for 5 hours. 200 ml of water and 100 ml of hexane were added to the resulting solution, and the organic layer was separated, washed with 400 ml of water, and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: hexane) to obtain 2.71 g of 3,3′-dihexyl-2,2′-bithiophene.

  Next, 2.71 g of the above 3,3′-dihexyl-2,2′-bithiophene was dissolved in 8 ml of dimethylformamide, a solution of N-bromosuccinimide 2.88 g in dimethylformamide (16 ml) was added, and 5 ° C. to 10 ° C. For 9 hours. 150 ml of water and 100 ml of hexane were added to the resulting solution, the organic layer was separated, washed with 300 ml of water, and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: hexane) to obtain 3.76 g of 5,5'-dibromo-3,3'-dihexyl-2,2'-bithiophene.

  Next, 3.76 g of the above 5,5′-dibromo-3,3′-dihexyl-2,2′-bithiophene and the above 2- (4,4,5,5-tetramethyl- [1,3,2] ] Dioxaborolan-2-yl) -3-hexylthiophene (4.71 g) was added to dimethylformamide (70 ml), and 19.4 g of potassium phosphate and [bis (diphenylphosphino) ferrocene] dichloropalladium (310 mg) were added under a nitrogen atmosphere. For 9 hours. To the resulting solution, 500 ml of water and 200 ml of hexane were added, and the organic layer was separated, washed with 300 ml of water, and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: hexane), and 3,4 ′, 3 ″, 3 ″ ′-tetrahexyl-2,2 ′: 5 ′, 2 ′. ': 5 ″, 2 ′ ″-Quarterthiophene 4.24g was obtained.

  Next, 520 mg of the above 3,4 ′, 3 ″, 3 ′ ″-tetrahexyl-2,2 ′: 5 ′, 2 ″: 5 ″, 2 ′ ″-quarterthiophene is dissolved in 20 ml of chloroform. Then, a solution of 280 mg of N-bromosuccinimide in dimethylformamide (10 ml) was added and stirred at 5 ° C. to 10 ° C. for 5 hours. To the obtained solution, 150 ml of water and 100 ml of dichloromethane were added, and the organic layer was separated, washed with 200 ml of water, and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: hexane), and 5,5 ′ ″-dibromo-3,4 ′, 3 ″, 3 ′ ″-tetrahexyl-2. , 2 ′: 5 ′, 2 ″: 5 ″, 2 ′ ″-quarterthiophene was obtained in an amount of 610 mg.

  Next, 280 mg of the above 4,7-bis (4,4,5,5-tetramethyl- [1,3,2] dioxaborolan-2-yl) -2,1,3-benzothiadiazole and the above 5,5 '' '-Dibromo-3,4', 3 '', 3 '' '-tetrahexyl-2,2': 5 ', 2' ': 5' ', 2' ''-quarterthiophene 596 mg in 30 ml of toluene Dissolved in. 10 ml of water, 1.99 g of potassium carbonate, 83 mg of tetrakis (triphenylphosphine) palladium (0) and 1 drop of Aliquat 336 were added thereto, and the mixture was stirred at 100 ° C. for 20 hours under a nitrogen atmosphere. 100 ml of methanol was added to the resulting solution, and the generated solid was collected by filtration and washed with methanol, water, acetone, and hexane in this order. The obtained solid was dissolved in 200 ml of chloroform, passed through a silica gel short column (eluent: chloroform), concentrated to dryness, then washed with methanol, acetone and methanol in this order to obtain a conjugated polymer [WP-BT1]. 480 mg was obtained. The weight average molecular weight was 29398, the number average molecular weight was 10916, and the polymerization degree n was 36.7.

Example 1
(1) Preparation of Semiconductor Solution Flask containing 5 ml of chloroform with 0.10 g of poly-3-hexylthiophene (Aldrich, regioregular, number average molecular weight (Mn): 13000, hereinafter referred to as P3HT) as a conjugated polymer In addition to the above, a P3HT chloroform solution was obtained by ultrasonic stirring in an ultrasonic cleaner (US-2, manufactured by Inoue Seieido Co., Ltd., output 120 W). Subsequently, this solution was taken in a dropper, and 0.5 ml was dropped into a mixed solution of 20 ml of methanol and 10 ml of 0.1N hydrochloric acid to perform reprecipitation. The solid P3HT was collected by filtration with a 0.1 μm pore size membrane filter (PTFE: tetrafluoroethylene), rinsed well with methanol, and then the solvent was removed by vacuum drying. Further, dissolution and reprecipitation were performed again to obtain 90 mg of reprecipitation P3HT.

  Next, 1.5 mg of CNT (manufactured by CNI, single-walled CNT, purity 95%, hereinafter referred to as single-walled CNT) and 1.5 mg of the above P3HT are added to 30 ml of chloroform, and an ultrasonic homogenizer (Tokyo Rika Co., Ltd.) is cooled with ice. Using an instrument (VCX-500 manufactured by Kikai Co., Ltd.), the mixture was ultrasonically stirred at an output of 250 W for 30 minutes. When the ultrasonic irradiation was performed for 30 minutes, the irradiation was stopped once, 1.5 mg of P3HT was added, and further ultrasonic irradiation was performed for 1 minute, whereby CNT dispersion A (CNT complex concentration with respect to the solvent was 0.05 g / l). )

  In order to examine whether or not P3HT adhered to CNTs in the CNT dispersion A, 5 ml of the dispersion A was filtered using a membrane filter, and CNTs were collected on the filter. The collected CNTs were quickly transferred onto a silicon wafer before the solvent was dried to obtain dried CNTs. When this CNT was subjected to elemental analysis using X-ray photoelectron spectroscopy (XPS), sulfur element contained in P3HT was detected. Therefore, it was confirmed that P3HT was adhered to the CNT in the CNT dispersion A.

  Next, a semiconductor solution for forming the semiconductor layer 4 was prepared. The CNT dispersion A was filtered using a membrane filter (pore size 10 μm, diameter 25 mm, Omnipore membrane manufactured by Millipore) to remove a CNT composite having a length of 10 μm or more. The obtained filtrate was designated as semiconductor solution A.

(2) Production of polymer solution for gate insulating layer 61.29 g (0.45 mol) of methyltrimethoxysilane, 12.31 g (0.05 mol) of β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 99.15 g (0.5 mol) of phenyltrimethoxysilane was dissolved in 203.36 g of propylene glycol monobutyl ether (boiling point: 170 ° C.), and 54.90 g of water and 0.864 g of phosphoric acid were added thereto with stirring. The obtained solution was heated at a bath temperature of 105 ° C. for 2.0 hours, the internal temperature was raised to 90 ° C., and a component mainly composed of methanol produced as a by-product was distilled off. Next, the bath was heated at 130 ° C. for 2.0 hours, the internal temperature was raised to 118 ° C., and a component mainly composed of water and propylene glycol monobutyl ether was distilled off. A weight percent polymer solution A was obtained.

  50 g of the obtained polymer solution A was weighed, mixed with 16.6 g of propylene glycol monobutyl ether (boiling point 170 ° C.), stirred at room temperature for 2 hours, and polymer solution B (solid content concentration 19.5 wt%) was obtained. Obtained.

(3) Production of FET The FET shown in FIG. 1 was produced. A gate electrode 2 was formed on a polyethylene terephthalate (PET) substrate 1 (thickness: 125 μm) by resistance heating and vacuum-depositing 5 nm of chromium and 50 nm of gold through a mask. Next, the polymer solution B prepared by the method described in (2) above is spin-coated (2000 rpm × 30 seconds) on the PET substrate on which the gate electrode is formed, and heat-treated at 150 ° C. for 2 hours in a nitrogen stream. Thus, the gate insulating layer 3 having a thickness of 600 nm was formed. Next, gold was vacuum-deposited so as to have a film thickness of 50 nm through a mask by a resistance heating method, and the source electrode 5 and the drain electrode 6 were formed.

  The width (channel width) of both electrodes was 0.1 cm, and the distance (channel length) between both electrodes was 100 μm. 1 μL of the semiconductor solution A prepared by the method described in (1) above was drop-cast on the substrate on which the electrode was formed, and the semiconductor layer 4 was obtained. Subsequently, after air drying at 30 ° C. for 10 minutes, a heat treatment was performed on a hot plate under a nitrogen stream at 150 ° C. for 30 minutes to obtain an FET.

(4) Evaluation of FET Next, the source-drain current (Id) -source-drain voltage (Vsd) characteristics when the gate voltage (Vg) of the FET was changed were measured. The measurement was performed in the atmosphere using a semiconductor characteristic evaluation system 4200-SCS type (manufactured by Keithley Instruments Co., Ltd.). When the mobility in the linear region was determined from the change in the value of Id at Vsd = −5 V when Vg = + 30 to −30 V, it was 0.48 cm ² / V · sec. Further, when the on / off ratio was determined from the ratio between the maximum value and the minimum value of Id at this time, it was 2.4 × 10 ⁵ .

Comparative Example 1
An FET was produced in the same manner as in Example 1 except that P3HT was not used when producing the semiconductor solution, and the characteristics were measured. When the mobility in the linear region was determined from the change in the value of Id at Vsd = −5 V when Vg was changed from +30 to −30 V, it was 0.015 cm ² / V · sec. Further, when the on / off ratio was determined from the ratio between the maximum value and the minimum value of Id at this time, it was 1.3 × 10 ³ .

Comparative Example 2
1.5 mg of CNT (manufactured by CNI, single-walled CNT, purity 95%, hereinafter referred to as single-walled CNT) and 1.5 mg of sodium lauryl sulfate (SDS) were added to 30 ml of water, and an ultrasonic homogenizer (Tokyo) The mixture was ultrasonically stirred at an output of 250 W for 3 hours using a VCX-500 manufactured by Rika Kikai Co., Ltd. to obtain a CNT dispersion B (CNT complex concentration 0.05 g / l with respect to the solvent). The obtained CNT dispersion B was centrifuged at 21000 G for 30 minutes using a centrifuge (Hitachi Koki Co., Ltd. CT15E), and 80% of the supernatant was taken out to obtain a semiconductor solution B. Next, an FET was produced in the same manner as in Example 1 except that the semiconductor solution B was used instead of the semiconductor solution A, and the characteristics were measured. When the mobility in the linear region was determined from the change in the value of Id at Vsd = −5V when Vg = + 30 to −30V, it was 0.012 cm ² / V · sec. Further, the on / off ratio obtained from the ratio between the maximum value and the minimum value of Id at this time was 75.

Example 2
An FET was produced in the same manner as in Example 1 except that polyethylene naphthalate (PEN) (thickness 125 μm) was used as the substrate, and the characteristics were measured. The results are shown in Table 1.

Example 3
An FET was produced in the same manner as in Example 1 except that polyethersulfone (PES) (thickness: 100 μm) was used as the substrate, and the characteristics were measured. The results are shown in Table 1.

Example 4
An FET was produced in the same manner as in Example 1 except that [WP-BT1] obtained in Synthesis Example 1 was used instead of P3HT, and characteristics were measured. The results are shown in Table 1.

Example 5
After the semiconductor solution A was drop-cast, a FET was prepared and measured for characteristics in the same manner as in Example 1 except that heat treatment was performed at 130 ° C. for 30 minutes in a nitrogen stream on a hot plate. The results are shown in Table 1.

  The field effect transistor of the present invention is preferably used for a smart card, a security tag, a transistor array for a flat panel display, and the like.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate electrode 3 Gate insulating layer 4 Semiconductor layer 5 Source electrode 6 Drain electrode

Claims (4)

A field effect transistor having a substrate made of an organic polymer compound, a gate electrode, a gate insulating layer, a semiconductor layer, a source electrode and a drain electrode, wherein the conjugated polymer is attached to at least a part of the surface of the semiconductor layer A field effect transistor containing a carbon nanotube composite. 2. The field effect transistor according to claim 1, wherein the organic polymer compound contains polyester, polyether sulfone, polycarbonate, polyamide, polyimide, or any derivative thereof. 3. The field effect transistor according to claim 1, wherein the conjugated polymer contains a thiophene skeleton in a repeating unit. A method of manufacturing a field effect transistor having a step of forming a gate electrode, a gate insulating layer, a semiconductor layer, a source electrode, and a drain electrode on a polymer substrate, wherein the step of forming the semiconductor layer comprises: The electric field according to any one of claims 1 to 3, comprising a step of applying a semiconductor solution containing a carbon nanotube composite having a conjugated polymer attached to at least a part of a surface and a heat treatment at a temperature of 150 ° C or lower. Method for producing effect transistor.

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