JPH0722670A - Field-effect transistor - Google Patents

Abstract

PURPOSE:To raise conductivity of an electrode and to realize high response of a gate voltage by forming at least one element of a semiconductor layer, a source electrode, a drain electrode and a gate electrode of a conjugate high polymer having a repetition unit expressed by a specified formula. CONSTITUTION:At least one element of a semiconductor layer 2, a source electrode 3, a drain electrode 4 and a gate electrode 5 is formed of a conjugate high polymer having a repetition unit expressed by a formula I. In the formula, Ar<1> and Ar<2> is a conjugate aromatic ring which can have a substituent group or a conjugate complex ring which can have a substituent group. They can be different by (m) and (p), (m) is an integer of 1 or more, (n) is 0 or 1, (p) is 0 or an integer of 1 or more and (q) is an integer of 2 or more. When (n) is 1, (p) is an integer of 1 or more. Since an azo group is provided to a principal chain and an entire of the principal chain is pi electron conjugate, it is possible to improve semiconductor property to raise conductivity of an electrode and to realize high response by a gate voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect transistor using a conjugated polymer having an azo group in its main chain.

[0002]

2. Description of the Related Art Field effect transistors (hereinafter referred to as FETs)
In the element), the conductivity of the semiconductor layer, which is the current path between the source electrode and the drain electrode, is controlled by the voltage applied to the gate electrode. Various proposals have been made to use an organic semiconductor as a semiconductor layer of such an FET element. For example, in Japanese Patent Laid-Open No. 1-259563, a π-electron conjugated polymer such as polythiophene or polypyrrole is used as a semiconductor layer, and a conductive polymer obtained by doping these polymers with a dopant is used as a source electrode or a drain electrode. Also, an FET element used as a gate electrode has been proposed.

However, when the conductive polymer is used as an electrode, the electric conductivity is still low. In addition, the conjugated polymer such as polythiophene that constitutes the semiconductor layer is not yet sufficient in characteristics as a semiconductor. Therefore, the response due to the gate voltage is low, and the electrical conductivity of the semiconductor layer between the source electrode and the drain electrode cannot be accurately controlled.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an FET device having a high electrode conductivity and a high responsiveness to a gate voltage despite using an organic polymer. is there.

Another object of the present invention is to provide an FET device capable of controlling the electric conductivity of a semiconductor layer between a source electrode and a drain electrode with high accuracy.

[0006]

As a result of intensive studies to achieve the above object, the present inventors have found that a polymer in which an azo group in the main chain is bonded to a conjugated aromatic ring or a conjugated heterocycle has excellent characteristics as a semiconductor. The present invention has been completed by discovering that it exhibits high conductivity.

That is, in the field effect transistor of the present invention, at least one element of the semiconductor layer, the source electrode, the drain electrode and the gate electrode has a conjugated polymer having a repeating unit represented by the following formula (I). Is formed by.

[Chemical 6] (In the formula, Ar ¹ and Ar ² are a conjugated aromatic ring which may have a substituent or a conjugated heterocycle which may have a substituent, and may be different depending on m and p. , M
Is an integer of 1 or more, n is 0 or 1, p is an integer of 0 or 1 or more, and q is an integer of 2 or more. However, when n is 1, p is an integer of 1 or more) In the formula (I), A
Examples of the aromatic compound that constitutes the conjugated aromatic ring represented by r ¹ and Ar ² include benzene, naphthalene, anthracene, phenanthrene, naphthacene, triphenylene, pyrene, chrysene, perylene, and indacene. Preferred conjugated aromatic rings include 1 to 4, particularly 1 or 2 aromatic rings such as benzene ring and naphthalene ring.

As the heterocyclic compound constituting the conjugated heterocycle, a compound containing a heterocycle having at least one hetero atom selected from oxygen atom, sulfur atom and nitrogen atom,
For example, compounds containing 5-membered heterocycles such as thiophene, furan, pyrrole, oxazole, thiazole, imidazole, pyrazole, isothiazole and isoxazole; 6-membered heterocycles such as viridine, pyridazine, pyrazine, indole, quinoline, carbazole and phenanthroline. And the like.

The compound having a preferable heterocycle includes, for example, a compound represented by the following formula (III).

[Chemical 7] (In the formula, X represents an oxygen atom or a sulfur atom, and R represents a hydrogen atom, an alkyl group, an alkenyl group, an acyl group, an aryl group, an aralkyl group, an alkylsulfonyl group or an arylsulfonyl group.) In the formula (III), In the compounds represented, X is often a nitrogen atom. Examples of the alkyl group include methyl, ethyl, propyl,
An alkyl group having about 1 to 10 carbon atoms such as isopropyl, butyl, t-butyl, hexyl and octyl is included.
Alkenyl groups include, for example, vinyl, allyl, propenyl, isopropenyl groups and the like. The acyl group includes
Examples include formyl, acetyl, propionyl, butyryl groups and the like. Aryl groups include, for example, phenyl,
Examples include naphthyl, biphenyl and their derivatives. The aralkyl group includes, for example, a benzyl group, the alkylsulfonyl group includes methylsulfonyl, ethylsulfonyl and the like, and the arylsulfonyl group includes phenylsulfonyl, naphthylsulfonyl and the like.

Examples of the substituent which may be substituted on the aromatic ring or the heterocycle include a halogen atom (eg, fluorine, chlorine, bromine etc.), an alkyl group (eg, methyl,
Lower alkyl groups having about 1 to 6 carbon atoms such as ethyl, propyl, isopropyl, butyl, etc.), hydroxyl groups,
Alkoxy groups (eg, lower alkoxy groups having about 1 to 6 carbon atoms such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, etc.) are included. The substitution position of these substituents is not particularly limited. The number of substituents is, for example, about 1 to 3.

Ar ¹ and Ar ² may be different by repeating m and p. Preferred m is 1-5,
Especially, it is about 1 to 3. n is 0 or 1, and preferable p is 0 to 3, particularly about 0 or 1. q is 2 or more, preferably 5 to 10000, and more preferably 10 to 10
It is often around 00. However, when n is 1, p is an integer of 1 or more.

A preferred conjugated polymer has the following formula (I
It has a repeating unit represented by a), (Ib) or (Ic).

[Chemical 8] (In the formula, A ¹ ring, A ² ring, A ³ ring and A ⁴ ring are the same or different and represent a 5- or 6-membered heterocyclic ring which may have a substituent, and X is an oxygen atom, a sulfur atom or Indicates a nitrogen atom, A
When ¹ to A ⁴ ring is 5-membered heterocyclic ring, the nitrogen atom has a hydrogen atom, an alkyl group, an alkenyl group, an acyl group, an aryl group, an aralkyl group, an alkylsulfonyl group or an arylsulfonyl group. Ar ^1a and Ar ^1b are the same or different and each represents a conjugated fused ring containing two or more aromatic rings which may have a substituent, and Ar ^1c represents one or more aromatic rings which may have a substituent. A conjugated aromatic ring containing is shown.
(m is an integer of 1 to 3, p is 0 or 1, and q is an integer of 2 or more) More specifically, one example of the conjugated polymer of the present invention is as follows. (Ia1) ~ (Ic
A polymer having the repeating unit of 1) is included.

[Chemical 9] (In the formula, R, m, p and q are the same as above) The conjugated polymer of the present invention may form a salt. Examples of the salt of the conjugated polymer include organic carboxylic acid salts (for example, salts with acetic acid, propionic acid, formic acid, trichloroacetic acid, trifluoroacetic acid, etc.), sulfonic acid salts (for example, p-toluenesulfonic acid, methane). Sulfonic acid, ethanesulfonic acid, trichloromethanesulfonic acid, salts with trifluoromethanesulfonic acid, etc.); inorganic acid salts (for example, hydrochloric acid, sulfuric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid) , Tetrafluoroboric acid, salts with fluoroarsenic acid, etc.) and the like.

The conjugated polymer of the present invention itself has a property as a p-type semiconductor and can be used as a semiconductor layer of an FET element. Further, it can be used as, for example, an n-type semiconductor by doping an appropriate dopant.

When used as a source, drain or gate electrode of an FET element, a particularly preferred conjugated polymer is doped with an ionic compound as a dopant in order to enhance the electric conductivity.

The conjugated polymer doped with the dopant has, for example, a repeating unit represented by the following formula (II) and has a high electric conductivity.

[Chemical 10] (In the formula, Y represents an anion and a represents a valence of the anion.
Is an integer of 1 to 3 and r is 0 to 2. Ar ¹ , Ar ² ,
(m, n, p and q are the same as above) In the polymer containing the repeating unit represented by the above formula (II), the preferred anion valency a is 1 or 2, especially 1, and r is a source , 0.0 when used as a drain or gate electrode
It is about 01 to 2, preferably about 0.01 to 1.

The anion represented by Y is, for example,
Organic acid ions (for example, p-toluenesulfonate ion, methanesulfonate ion, ethanesulfonate ion, trichloromethanesulfonate ion, trifluoromethanesulfonate ion, etc.); halogen ion (for example, fluorine ion, chlorine ion, bromine ion) , Iodine ion); inorganic acid ions (for example, perchlorate ion, tetrafluoroborate ion, fluoroarsenate ion, sulfate ion, iron chloride ion, etc.) and the like. One or more of these anions may be doped in the polymer. As the dopant, an acid or salt (for example, sodium salt, potassium salt, etc.) corresponding to the anion can be used.

Doping can be carried out by a conventional method such as electrolytic oxidation polymerization method or ion implantation method. In addition, the polymer represented by the formula (I) is a compound corresponding to the anion represented by Y, for example, concentrated hydrochloric acid,
The above formula (II) can also be obtained by immersing in a liquid compound such as concentrated sulfuric acid, organic acid or sulfonic acid and its salt, doping from a liquid phase, exposing to vapor of a gaseous compound such as halogen, or doping from a gas phase. A polymer represented by can be obtained. From the viewpoint of operability and controllability of doping amount,
An electrolytic oxidative polymerization method in which electricity is applied in a supporting electrolyte solution described later is preferable.

Contrary to the above, when the polymer doped with the dopant is subjected to the electrolytic reduction reaction, the above formula (I)
A polymer represented by can be obtained.

The polymer represented by the formula (I) can be produced by polymerizing a compound corresponding to the repeating unit or a salt thereof. For example, among the polymers represented by the above formula (Ia), the polymer with p = 1 can be produced by polymerizing the compound represented by the following formula (IV). The polymer represented by the formula (Ic) can be produced by polymerizing a compound represented by the following formula (V).

[Chemical 11] (In the formula, A ¹ ring to A ⁴ ring, Ar ^1c and X are the same as described above) For the polymerization, either an electrolytic oxidative polymerization method or a chemical oxidative polymerization method can be used. The electrolytic oxidative polymerization is carried out by the compound represented by the formula (IV), for example, 2,2′-azopyrrole, or the compound represented by the formula (V), for example, 1,4-.
It can be carried out by polymerizing bis (2-pyrrolylazo) benzene or the like in an electrolytic solution containing a supporting electrolyte.

The supporting electrolyte is soluble in a solvent,
Salts that are easily dissociated into ions are preferable, and examples thereof include perchlorates such as tetraethylammonium perchlorate, tetrabutylammonium perchlorate, and lithium perchlorate; sodium tetrafluoroborate, lithium tetrafluoroborate, and tetrafluoroborate. Acid tetraethylammonium,
Tetrafluoroborate salts such as tetrabutylammonium tetrafluoroborate; Hexafluorophosphate salts such as tetraethylammonium hexafluorophosphate and tetrabutylammonium hexafluorophosphate; Sulfonate salts such as tetraethylammonium paratoluenesulfonate; Iodates such as lithium bromide; Hydrobromides such as lithium bromide; Hydrochlorides such as lithium chloride;
Sodium salts such as sodium hydroxide are included.
Preferred supporting electrolytes include perchlorates such as tetrabutylammonium perchlorate; tetrafluoroborates such as tetraethylammonium tetrafluoroborate and tetrabutylammonium tetrafluoroborate.

The concentration of the supporting electrolyte is usually 0.01 to
1.0 mol / L, preferably 0.05 to 0.5 mol / L
It is a degree.

As the solvent, a good solvent for the supporting electrolyte, for example, alcohols such as methanol, ethanol and isopropanol; ethers such as tetrahydrofuran; carbonates such as propylene carbonate; nitro compounds such as nitromethane, nitroethane and nitrobenzene; acetonitrile, Examples thereof include nitriles such as benzonitrile; amides such as dimethylformamide and dimethylacetamide; sulfoxides such as dimethylsulfoxide; halogenated hydrocarbons such as dichloromethane; mixed solvents thereof. The amount of the solvent used can be selected according to the concentration of the supporting electrolyte.

The amount of the compound represented by the formula (IV) or (V) or a salt thereof used is not particularly limited, but is 0.01 to
It is often 1 mol / L, preferably 0.1 to 0.5 mol / L.

The electrolytic oxidative polymerization can be carried out by a constant potential method, a constant current method, a potential scanning method or the like, and may be a two pole method or a three pole method using a reference electrode. The current density is
For example, the electric potential is, for example, about 0.1 to 10 mA / cm ² , and the electric potential is, for example, about 0.3 to 1 V (vs Ag / AgCl).

When the electrolytic oxidative polymerization is carried out in this way, the polymer is deposited in the form of a film on the surface of the anode. Therefore, a thin film made of the polymer can be formed on the surface of the anode. Moreover, the film thickness can be easily and accurately controlled by adjusting the current density, the potential, and the energization time for electrolytic oxidation.

The chemical oxidative polymerization method can be carried out in the presence of a polymerization initiator. As the polymerization initiator, an acid (eg, hydrochloric acid, sulfuric acid, etc.); an oxidizing agent (eg, ferric chloride,
Transition metal salts such as ferric perchlorate, silver chloride, silver perchlorate, cupric chloride, copper perchlorate, and copper tetrafluoroborate,
Hydrogen peroxide, benzoquinone, quinones such as naphthoquinone). Of these polymerization initiators, an oxidizing agent, for example, a ferric compound such as ferric chloride or ferric perchlorate, or a silver compound such as silver chloride or silver perchlorate is often used. The concentration of the polymerization initiator is determined by the above formula (I
V) Compound represented by (V) or salt thereof (monomer) 1
It is about 1 to 5 mol, preferably about 1 to 4 mol per mol.

The reaction is usually carried out in the presence of a solvent. As the solvent, for example, methanol, ethanol,
Alcohols such as isopropanol; Halogenated hydrocarbons such as methylene chloride; Ethers such as tetrahydrofuran; Carbonates such as propylene carbonate; Nitro compounds such as nitromethane, nitroethane and nitrobenzene; Nitriles such as acetonitrile and benzonitrile; Dimethylformamide, Examples thereof include amides such as dimethylacetamide; sulfoxides such as dimethyl sulfoxide; mixed solvents thereof and the like.

The amount of the solvent used is not particularly limited, but the concentration of the compound represented by the above formula (IV) (V) or a salt thereof is 0.01 to 1 mol / L, preferably 0.1 to 0. .5
In many cases, the amount is about mol / L.

The polymerization temperature is not higher than the reflux temperature, for example, -3.
0 to 100 ° C, preferably about -10 to 90 ° C,
The polymerization time is, for example, 0.5 to 24 hours, preferably 2
It is about 12 hours.

The conjugated polymer of the present invention can be obtained by recovering the polymer produced by the polymerization and purifying it by a purification means such as solvent washing. Incidentally, the conjugated polymer may be precipitated from the reaction system along with the polymerization. In this case, the generated precipitate can be collected by a simple method such as filtration.

The novel compound represented by the formula (V) has a heterocyclic compound (eg, pyrrole) corresponding to the A ³ ring and / or A ⁴ ring and an arylene group corresponding to Ar ^1c. It is obtained by coupling with a bisdiazonium salt in a solvent. The bisdiazonium salt can be obtained by tetrazotizing a diaminoaryl compound corresponding to Ar ^1c by a conventional method. The tetrazotization reaction mixture can be subjected to the coupling reaction as it is, but an acid, for example, tetrafluoroboric acid, an aqueous solution of sodium tetrafluoroborate or the like is added, and isolated as a bisdiazonium salt to be subjected to the coupling reaction. It is preferable to provide.

The coupling reaction is carried out, for example, by cooling the solution of the heterocyclic compound and the solvent in an inert gas atmosphere,
It can be carried out by gradually adding about 0.4 to 0.6 mol of the bisdiazonium salt compound to 1 mol of the heterocyclic compound.

As the reaction solvent, aprotic solvents such as halogenated hydrocarbons such as methylene chloride; ethers such as tetrahydrofuran; carbonates such as propylene carbonate; nitriles such as acetonitrile; dimethylformamide, dimethylacetamide and the like. Amides; sulfoxides such as dimethyl sulfoxide; mixed solvents thereof, and the like. The amount of the solvent used is, for example, 0.01 to 0.5 for the concentration of the heterocyclic compound.
The amount is often about mol / L, preferably about 0.1 to 0.2 mol / L.

The reaction temperature is, for example, -20 to 10 ° C, preferably -10 to 0 ° C, and the reaction time is 0.5.
~ 6 hours, preferably 1 to 4 hours. After completion of the reaction, for example, a large amount of water is added to the reaction product, and the product is purified by washing with a solvent or the like, whereby the bisazo compound represented by the formula (V) can be obtained.

Among the polymers represented by the above formula (Ia), p
The polymer of = 0 and the polymer represented by the formula (Ib) can be produced by polymerizing a compound represented by the following formula (VI) or a salt thereof.

[Chemical 12] (Wherein Ar ^1a and Ar ^1b are the same as above) Formula (VI)
Among the compounds represented by, preferred diaminoheterocyclic compounds include diaminoheterocyclic compounds such as 2,5-dianopyridine, and preferred diaminoaryl compounds include diamino-compounded with about 2 to 4 aromatic rings. A conjugated aromatic compound, for example, 1,4-diaminonaphthalene,
Diaminonaphthalene such as 2,6-diaminonaphthalene and salts thereof are included.

The polymerization of the diaminoheterocyclic compound, the diaminoaryl compound or their salts can be carried out in the presence of an oxidizing agent. As the oxidizing agent, for example, a perborate such as sodium perborate or potassium perborate, or a mixture of perborate and boric acid can be used. The amount of the oxidizing agent used is about 2 to 10 times mol, preferably about 2 to 5 times mol, of the compound represented by the formula (VI) or a salt thereof. When boric acid is used, it is used in an amount of 0.1 to 2 times, preferably 0.5 to 1 times the mol of the perborate.

The reaction is usually carried out in the presence of a solvent. As the solvent, a good solvent for the above compound or a salt thereof, for example, water; alcohols such as methanol, ethanol and isopropanol; ethers such as tetrahydrofuran; organic acids such as acetic acid; inorganic acids such as hydrochloric acid and sulfuric acid; pyridine and pyrrolidone , Nitrogen compounds such as methylpyrrolidone; nitriles such as acetonitrile; amides such as dimethylformamide and dimethylacetamide; sulfoxides such as dimethylsulfoxide; mixed solvents thereof and the like. Preferred solvents include, for example:
Examples include alcohols such as methanol and sulfoxides such as dimethyl sulfoxide.

The amount of the diaminoaryl compound represented by the above formula (VI) or a salt thereof is not particularly limited,
It is often 0.01 to 1 mol / L, preferably 0.1 to 0.5 mol / L.

The polymerization temperature is not higher than the reflux temperature, for example, 30
To 100 ° C, preferably about 50 to 90 ° C, and the polymerization time is, for example, 0.5 to 24 hours, preferably 4 to 1
It takes about 2 hours.

The conjugated polymer can be obtained by purifying the polymer produced by the polymerization by a purifying means such as solvent washing.

The conjugated polymer of the present invention is usually colored black or the like, is thermally stable, and has excellent semiconductor characteristics and film forming properties. Therefore, the polymer is useful as a semiconductor layer material for FET devices. Further, the conjugated polymer doped with a dopant has a particularly high conductivity and can be suitably used as the source, drain and gate electrodes of an FET element.

Although the structure of the FET element is not particularly limited,
The insulated gate type element and the like shown in FIGS. 1 to 3 are exemplified.

In FIG. 1, a semiconductor layer 2 is provided on a substrate 1, on which a source electrode 3 and a drain electrode 4 are provided.
And are provided separately from each other. The semiconductor layer 2, the source electrode 3 and the drain electrode 4 are covered with an insulating film 6, and a gate electrode 5 is formed on the insulating film 6.
As shown in FIG. 2, the gate electrode 5 and the insulating film 6 may be provided on the substrate 1, and the source electrode 3, the drain electrode 4 and the semiconductor layer 3 may be provided thereon.

Depending on the purpose, as shown in FIG.
Lead wire 7 from the source electrode 3 or the drain electrode 4,
A metal film may be used as the gate electrode 8 and the gate electrode 5.

As the substrate 1, glass, an alumina sintered body, an electrically insulating polymer having a film forming ability such as polyester, polyimide or the like can be used.

The substrate 1 can also be formed of a semiconductor such as silicon or a metal such as stainless steel or copper, depending on the purpose of use. In this case, the gate electrode 5 can be omitted.

In the FET element, at least one element of the semiconductor layer 2, the source electrode 3, the drain electrode 4 and the gate electrode 5 can be formed by using the conjugated polymer.

The conjugated polymer of the present invention has a property as a p-type semiconductor when it is not doped, and can be used as it is for a semiconductor layer. Further, by doping with an appropriate dopant, it can be used as an n-type semiconductor, for example. Such a conjugated polymer is useful as a material for the semiconductor layer. When the semiconductor layer is formed of a conjugated polymer, the source electrode, the drain electrode, and the gate electrode can be formed of a metal or a conductive polymer.

The source electrode, the drain electrode, and the gate electrode are preferably formed of a dopant-doped conjugated polymer, for example, a polymer having a repeating unit represented by the formula (II). Such a polymer is particularly excellent in conductivity and is suitable as a material for these electrodes. In this case, the semiconductor layer can be formed of an inorganic semiconductor such as silicon or an organic semiconductor.

As described above, the semiconductor layer 2 shown in FIG. 1 is electrolytically polymerized using the substrate as an anode to form a film of a conjugated polymer on the substrate, and a polymer solvent solution is spin-coated or dipping. It can be formed by a coating method. In addition, a method of coating a catalyst in advance and introducing a monomer gas to form a film, a sputtering method, a CVD method, a plasma CVD method, an evaporation method such as a cluster ion beam evaporation method, a Langmuir-Blodgett method, or the like You can also In the case of the Langmuir-Blodgett method, either a method of polymerizing before depositing on the substrate or a method of polymerizing after depositing may be used.

The solvent is a good solvent for the conjugated polymer, for example, aromatic hydrocarbons such as benzene and toluene; organic acids such as formic acid and acetic acid; inorganic acids such as hydrochloric acid; ethers such as tetrahydrofuran. Dimethylformamide,
Examples thereof include amides such as dimethylacetamide; sulfoxides such as dimethyl sulfoxide; mixed solvents of these.

In the FET element, the semiconductor layer 2, the source electrode 3, the drain electrode 4, the gate electrode 5 and the insulating film 6
Can be formed, for example, by processing a conductive thin film and a semiconductive thin film made of the above-mentioned conjugated polymer into a pattern according to each purpose. As such a processing method, photolithography using a positive resist or a negative resist, masking, etching or the like can be appropriately selected. In addition, after forming a semiconductive thin film, it is possible to perform doping by doping only a specific portion by masking or the like to impart conductivity, and patterning.

As shown in FIG. 3, when the lead wires 7 and 8 are formed of a metal film, the source electrode 3 made of a conjugated polymer is used.
The drain electrode 4 can also be formed, for example, by performing the electrolytic oxidation polymerization as described above using the patterned metal film as an anode.

Examples of such a metal film include metals such as gold, platinum, chromium, palladium, aluminum and indium; oxides such as tin and indium; and metal oxides such as indium / tin oxide. These may be used alone or in combination of two or more.

The method for forming the metal film is not particularly limited, and examples thereof include plating, vapor deposition, sputtering and CVD.
A conventional method such as a plasma CVD method or a plasma CVD method can be appropriately selected.

As the insulating film 6, any organic or inorganic material can be used as long as it is an electrically insulating material. For example, silicon oxide, silicon nitride, aluminum oxide,
Inorganic materials such as mullite; polyethylene, polyimide, polyvinylcarbazole, polyvinyl butyral, polyester, polytetrafluoroethylene, tetrafluoroethylene-hexafluoroethylene copolymer, polyvinyl chloride, polypropylene, polybutadiene, cellulose acetate, polyphenylene oxide, polyphenylene sulfide Examples include organic insulating polymers such as phenol resin, epoxy resin, and polystyrene. These insulating materials may be used alone or in combination of two or more.

These insulating films are formed by a conventional method, for example,
CVD method, plasma CVD method, vapor deposition method, spin coating method, cluster ion beam vapor deposition method, electrolytic polymerization method,
It can be formed by a method such as a chemical polymerization method or a Langmuir-Blodgett method.

A preferable FET element includes one in which a semiconductor layer, a source electrode, a drain electrode and a gate electrode are made of a material containing the conjugated polymer and an organic material is used as an insulating film.

In such an element, since the difference in the coefficient of thermal expansion between the materials is small, peeling of the semiconductor layer does not occur. Also,
Since it is not necessary to use a silicon semiconductor that also serves as a substrate and a gate electrode, the manufacturing cost is reduced. Furthermore, since a conjugated polymer having excellent film forming properties is used, it is possible to make the device thin, have a large area, and have a large number of devices.

Since the FET element of the present invention can be made thin, have a large area, and have a large number of elements as described above, it can be suitably used for a switching element or a driving portion of a liquid crystal display device. . In particular, when a thin film of an organic polymer is used as the substrate, the entire element can be made of an organic material, so that the liquid crystal display device can be made thinner, have a larger area, and have a larger number of elements.

[0061]

The conjugated polymer used in the present invention has an azo group in the main chain and the whole main chain is a π-electron conjugated system, so that it has high semiconductor characteristics. Also, by doping,
The conductivity can be easily adjusted. Further, it has excellent film-forming properties, and a semiconductive or conductive thin film can be easily formed. Therefore, it is useful as a material for semiconductor layers, source electrodes, drain electrodes, and gate electrodes of FET elements.

The field-effect transistor formed of such a material has a high electrode conductivity and a high responsiveness to the gate voltage, so that the drain current can be controlled accurately.

[0063]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

Example 1 Tetrabutylammonium perchlorate 1 mmol, 2,
1 mmol of 2'-azopyrrole was added to 10 m of acetonitrile.
a glass plate having a conductive coating film formed on its surface as a working electrode, and a counter electrode Pt plate was immersed in this solution under an argon atmosphere by a constant current method of 0.2 mA / cm ^2. Electrolytically oxidatively polymerized. After energizing 24 coulombs,
When the working electrode was taken out, a black precipitate was deposited on the glass plate. The deposit was washed with methanol and then dried under reduced pressure to obtain a thin film made of polyazopyrrole.

The infrared absorption spectrum and elemental analysis results of the polyazopyrrole peeled from the glass plate were as follows.

IR (KBr) ν (cm ^-1 ): 1578,
1479,1033,897,782 Elemental analysis: the above formula (Ia) with R = H doped
1) Polymer H C N O Cl Measured value (%) 4.7 53.0 30.8 7.4 4.1 Theoretical value (%) 3.8 53.7 31.3 7.4 4.4. 1 From the results of the above elemental analysis, carbon C / nitrogen N (molar ratio) =
It was about 2, and it was confirmed that the product was polyazopyrrole represented by the formula (Ia1) and that the dopant was doped.

When the obtained polymer was pelletized and the electric conductivity was measured, it was 2 × 10 ^-2 S / cm. When the pellets were left in the air for 2 months and the electric conductivity was measured again, no change in the electric conductivity was observed.

Example 2 A 3-necked flask equipped with a stirrer, a cooling ring and a thermometer was charged with 0.58 g of 2,5-diaminopyridine dihydrochloride, 1.41 g of sodium perborate tetrahydrate and boric acid. 0.36
g and 6 ml of water were charged and dissolved, and while stirring, 4
The reaction was carried out at 5 ° C for 8 hours. The reaction mixture was suction filtered to give a black solid. The solid was thoroughly washed with boiling water, further washed with methanol, and dried under reduced pressure at 100 ° C. to obtain 0.20 g of polyazopyridine hydrate.

IR (KBr) ν (cm ⁻¹ ): 1625
1562, 1503, 1398, 1341, 1298,
1240, 1130, 1012, 830 Elemental analysis: H C N O measured value (%) 3.95 50.88 35.20 9.97 theoretical value (%) 3.80 50. for the polymer of the formula (Ia2). 60 35.42 10.18 From the results of the above elemental analysis, carbon C / nitrogen N (molar ratio) =
It was 1.68 (theoretical value: 1.67), and the polymer produced was found to be the polyazopyridine represented by the above formula (Ia2). The polymer is a hydrate (C
₅ H ₃ N ₃ ) _0.53 · (H ₂ O) _0.43 .

The obtained polymer was dissolved in formic acid and the solution was coated on a glass plate by spin coating, whereby a thin film made of the polymer could be formed.

Example 3 In a three-necked flask equipped with a stirrer, a cooling ring and a thermometer, 0.34 g of 1,4-diaminonaphthalene dihydrochloride was added.
Sodium perborate tetrahydrate 0.70 g, boric acid 0.1
8 g and 4 ml of methanol were charged and dissolved, and the mixture was reacted at 70 ° C. for 7 hours while stirring. The reaction mixture was suction filtered to give a black solid. The solid was thoroughly washed with boiling water, further washed with methanol, and dried under reduced pressure at 100 ° C to obtain 0.13 g of polyaminoazonaphthalene.

IR (KBr) ν (cm ^-1 ): 1636,
1599, 1579, 1516, 1453, 1420,
1339, 1315, 1212, 762 Elemental analysis: H C N measured value (%) 4.07 80.22 15.71 theoretical value (%) 4 for the polymer of the formula (Ib1) with m = 2 and p = 1 .23 80.18 15.59 From the results of the above elemental analysis, carbon C / nitrogen N (molar ratio) =
It is 6.0. Further, from the result of N ^1S of ESCA, a peak of 398.9 eV derived from the nitrogen of the amino group and a peak of 400.2 eV derived from the azo group were observed. From these data, the product was confirmed to be polyaminoazonaphthalene.

1 part by weight of the obtained polymer was dissolved in 100 parts by weight of N-methylpyrrolidone, and the solution was applied to a glass plate by spin coating to form a thin film of the polymer.

Example 4 Instead of 1,4-diaminonaphthalene dihydrochloride, 2,6
Example 3 except using diaminonaphthalene dihydrochloride
In the same manner as in (1), 0.15 g of polyaminoazonaphthalene was obtained.

IR (KBr) ν (cm ^-1 ): 1618,
1602, 1587, 1527, 1432, 1388,
1343, 1245, 1143, 855, 836, 81
0 Elemental analysis: H C N measured value (%) 4.33 79.53 16.13 Theoretical value (%) 4.15 79.60 16 for the polymer of the formula (Ib2) in which m = 3 and p = 1 .25 From the results of the above elemental analysis, carbon C / nitrogen N (molar ratio) =
It is 5.7. Further, from the result of N ^1S of ESCA, a peak of 398.9 eV derived from the nitrogen of the amino group and a peak of 399.9 eV derived from the azo group were observed. From these data it was confirmed that the product was a polyaminoazonaphthalene polymer.

The obtained polymer was dissolved in N-methylpyrrolidone and coated on a glass plate by a spin coating method, whereby a thin film composed of the polymer could be formed.

Example 5 To a 3-necked flask equipped with a stirrer, a cooling ring and a thermometer, 2.16 g of p-phenylenediamine was added a phosphoric acid solution (d = 1.7) and dissolved while heating. After cooling the solution to about -5 ° C, 30 ml of concentrated sulfuric acid and nitrosylsulfuric acid synthesized from 2.88 g of sodium nitrite were added dropwise, and after completion of the addition, reaction was carried out for 30 minutes. 40 ml of 42% tetrafluoroboric acid solution was added to the reaction mixture, and the precipitated crystals were filtered, washed with methanol, and then dried under reduced pressure.
A 1,4-benzenebisdiazonium salt was obtained.

0.2 g of pyrrole and 8 ml of acetonitrile
The solution of and is cooled to -10 ° C, 0.46 g of bisdiazonium salt is gradually added to this solution, and the mixture is stirred for 1 hour to carry out a coupling reaction to contain 1,4-bis (2-pyrrolylazo) benzene. An acetonitrile solution was obtained.

Instead of the acetonitrile solution of Example 1 containing tetrabutylammonium perchlorate and 2,2'-azopyrrole, tetrabutyl perchlorate was added to the acetonitrile solution containing 1,4-bis (2-pyrrolylazo) benzene. A thin film made of the above polymer was formed on a glass plate in the same manner as in Example 1 except that electrolytic oxidation polymerization was performed using a solution in which ammonium was dissolved.

The infrared absorption spectrum and elemental analysis results of the polymer produced by electrolytic oxidation polymerization are as follows.

IR (KBr) ν (cm ^-1 ): 1594,
1540, 1506, 1486, 1404, 1339,
1236, 1169, 1135, 1048, 926, 8
36,787 Elemental analysis: HCN measured value (%) 3.62 51.43 24.95 theoretical value (%) 3.04 51.28 25. for polymer of formula (Ic1) wherein R = H. 68 From the results of the above elemental analysis, carbon C / nitrogen N (molar ratio) =
2.40 (theoretical value 2.33), and the polymer produced by electrolytic oxidation polymerization is a polymer poly (bisazopyrrolyl) containing bisazopyrrolylphenylene represented by the above formula (Ic1) as a repeating unit. Benzene).

When the obtained polymer was pelletized and the electric conductivity was measured, it was 10 ^-3 S / cm. Also,
When the pellet was left in the air for 2 months and the electric conductivity was measured again, no change in the electric conductivity was observed.

Example 6 A field effect transistor having the structure shown in FIG. 3 was prepared using the materials obtained above.

A 400 μm thick n-type silicon plate (2.5
(cm × 2.5 cm), a silicon oxide film having a thickness of about 2500 Å was formed as the insulating film 6 on both surfaces by thermal oxidation. The lead wires 7 and 8 of the source electrode 3 and the drain electrode 4 are provided on one surface thereof.
A pattern for forming a metal film serving as a metal film was drawn, and then a chromium film having a thickness of 180 Å and a gold film having a thickness of 250 Å were sequentially formed on the chromium film by a vacuum evaporation method. The resist was removed to form metal films that act as the lead wires 7 and 8 of the source electrode 3 and the drain electrode 4. A lead wire was further taken on the lead wires 7 and 8 with a silver paste, and the contact portion was fixed with an epoxy resin to obtain an element substrate.

With the exception that the metal films 7 and 8 on the silicon plate were used as working electrodes and electricity was applied at 100 μA / cm ² for 5 minutes,
In the same manner as in Example 1, the source electrode 3 and the drain electrode 4 were formed by depositing the dopant-doped polyazopyrrole only on the patterned working electrode.
The substrate 1 on which polyazopyrrole was deposited was taken out, washed with methanol, dried under reduced pressure, and stored in vacuum. The thickness of the dried polyazopyrrole thin film was 2000Å.

The polyazopyridine obtained in Example 2 was used as a formic acid solution and was coated on the substrate on which the polyazopyrrole film was formed by a spin co-coating method in an argon atmosphere to form a semiconductor layer 2 made of polyazopyridine. Was formed. After washing with methanol, it was dried by blowing nitrogen gas, and then completely dried in vacuum.

The silicon oxide on the surface of the obtained substrate 1 opposite to the surface on which the semiconductor layer 2, the source electrode 3 and the drain electrode 4 are formed is partially removed with sandpaper, and n is removed with an indium-gallium alloy. The lead wire was taken out from the contact with the mold silicon. Fix the contact part with epoxy resin,
Through this lead wire, the n-type silicon which is the substrate 1 also acts as the gate electrode 5.

In the FET device thus obtained, the characteristics of the drain current with respect to the gate-source voltage were examined, and it was found that in the region of the gate-source voltage of 0 to -40V,
The drain current was largely controlled by the gate-source voltage, and good characteristics were obtained.

Further, the FET element of this embodiment is
No deterioration in properties was observed even when heated at 5 ° C. or left in air for 2 months.

Example 7 A thin film of poly (bisazopyrrolylbenzene) was formed as the source electrode 3 and the drain electrode 4 in the same manner as in Example 5, and the polyaminoazo obtained in Example 3 was used as the semiconductor layer 2. An FET element was prepared in the same manner as described above except that a naphthalene thin film was formed.

When the characteristics of the drain current with respect to the gate-source voltage were examined in the same manner as described above, good characteristics were obtained in the region of the gate-source voltage of 0 to -40V.
In addition, no deterioration of properties due to heating in air or leaving in air was observed.

Example 8 An FET device was prepared in the same manner as in Example 7 except that the polyaminoazonaphthalene thin film obtained in Example 4 was formed as the semiconductor layer 2.

When the characteristics of the drain current with respect to the gate-source voltage were examined in the same manner as described above, good characteristics were obtained in the region of the gate-source voltage of 0 to -40V.
In addition, no deterioration of properties due to heating in air or leaving in air was observed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a field effect transistor of the present invention.

FIG. 2 is a cross-sectional view showing another example of a field effect transistor.

FIG. 3 is a sectional view showing still another example of a field effect transistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Semiconductor layer 3 ... Source electrode 4 ... Drain electrode 5 ... Gate electrode 6 ... Insulating film 7, 8 ... Lead wire

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 29/786 9056-4M H01L 29/78 311 B

Claims (7)

[Claims] 1. A field effect transistor in which at least one element of a semiconductor layer, a source electrode, a drain electrode, and a gate electrode is formed of a conjugated polymer having a repeating unit represented by the following formula (I). .. [Chemical 1] (In the formula, Ar ¹ and Ar ² are a conjugated aromatic ring which may have a substituent or a conjugated heterocycle which may have a substituent, and may be different depending on m and p. , M
Is an integer of 1 or more, n is 0 or 1, p is an integer of 0 or 1 or more, and q is an integer of 2 or more. However, when n is 1, p is an integer of 1 or more) 2. The field effect transistor according to claim 1, wherein Ar ¹ and Ar ² are a conjugated aromatic ring containing at least one aromatic ring, or a 5- or 6-membered heterocyclic ring containing a nitrogen atom. 3. The field effect transistor according to claim 1, wherein m is an integer of 1 to 5, n is 0 or 1, and p is 0 or 1. 4. The field effect transistor according to claim 1, wherein the conjugated polymer has a repeating unit represented by the following formula (Ia). [Chemical 2] (In the formula, the A ¹ ring and the A ² ring are the same or different and each represents a 5- or 6-membered heterocyclic ring which may have a substituent, X represents an oxygen atom, a sulfur atom or a nitrogen atom, and the A ¹ ring And when the A ² ring is a 5-membered heterocycle, the nitrogen atom has a hydrogen atom, an alkyl group, an alkenyl group, an acyl group, an aryl group, an aralkyl group, an alkylsulfonyl group or an arylsulfonyl group, and p is 0. Or 1, q is an integer of 2 or more) 5. The field effect transistor according to claim 1, wherein the conjugated polymer has a repeating unit represented by the following formula (Ib). [Chemical 3] (In the formula, Ar ^1a and Ar ^1b are the same or different and each represents a conjugated fused ring containing two or more aromatic rings which may have a substituent, m is an integer of 1 to 3, and p is 0 or 1 , Q is an integer of 2 or more) 6. The field effect transistor according to claim 1, wherein the conjugated polymer has a repeating unit represented by the following formula (Ic). [Chemical 4] (In the formula, A ³ ring and A ⁴ ring are the same or different and each represents a 5- or 6-membered heterocyclic ring which may have a substituent, X represents an oxygen atom, a sulfur atom or a nitrogen atom, and an A ³ ring and when a ⁴ ring is 5-membered heterocyclic ring, the nitrogen atom is a hydrogen atom, an alkyl group, an alkenyl group, an acyl group, an aryl group, an aralkyl group, the .Ar ^1c has a alkylsulfonyl group or an arylsulfonyl group A conjugated aromatic ring containing one or more aromatic rings that may have a substituent, q represents an integer of 2 or more) 7. The source electrode, the drain electrode, and at least one electrode of the gate electrode is formed of a conjugated polymer having a repeating unit represented by the following formula (II) doped with a dopant. The field effect transistor described. [Chemical 5] (In the formula, Y represents an anion and a represents a valence of the anion.
Is an integer of 1 to 3 and r is 0 to 2. Ar ¹ , Ar ² ,
(m, n, p and q are the same as above)