JPH05110069A - Manufacture of field effect transistor - Google Patents

Abstract

PURPOSE:To obtain a method of manufacturing a field effect transistor, where an organic semiconductor thin film which is able to protect an electrode against deterioration, excellent in productivity, lightweight, and excellent in flexibility can be used as an active layer. CONSTITUTION:An organic thin film 11 is subjected to an activation treatment to turn into an organic semiconductor thin film 1, a source electrode 2 and a drain electrode 3 are formed on the organic semiconductor thin film 1, and a gate electrode 7 is formed so as to control conductivity between the source electrode 2 and the drain electrode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a field effect transistor using an organic compound as an active layer.

[0002]

2. Description of the Related Art Among organic compounds, low molecular weight compounds represented by phthalocyanine, π-conjugated polymers represented by polythiophene, and skeletons of the above π-conjugated polymers are the same, Many π-conjugated oligomers, which are represented by thiophene oligomers having a small number of units, and the like, which show semiconductor properties, are known. It is considered that these organic compounds form a band structure composed of a valence band, a conduction band, and a forbidden band separating them, similarly to an inorganic semiconductor, and a chemical method, an electrochemical method, a physical method, or the like. It is explained that by removing electrons from the valence band (oxidation) or by injecting electrons into the conduction band (reduction) (hereinafter referred to as doping), carriers carrying charges are generated. Due to such semiconductor properties, these organic compounds can be applied to various devices, and some reports have been made so far.

Specifically, a Schottky junction element using polyacetylene {publication (J. Appl. Phys.
52, p.869, 1981) and JP-A-56-1.
No. 47486, etc.}, Schottky junction device using polypyrrole-based polymer {publication (J. Appl. Phy
s. 54, 2511, 1983) and JP-A-5
No. 9-63760, etc.} are known. Further, a heterojunction device in which n-type CdS which is an inorganic semiconductor and p-type polyacetylene are combined has been reported {publication (J. Appl. Phys. 51, 4252, 19:
80 years)}. As a junction element in which organic semiconductors are combined, p-type and p-type using n-type polyacetylene are used.
n homojunction elements are known {publications (Appl. P
hys. Lett. 33, p. 18, 1978)}.
Further, a heterojunction element composed of polypyrrole and polythiophene {publication (Jpn. J. Appl. Phys. 2
4, L553, 1985)}, a heterojunction element pyrrole composed of polyacetylene and poly N-methyl {publication (J. Appl. Phys. 58, 1279, 1
985)} is also known.

Recently, attempts have been made to apply an organic semiconductor to the active layer of a field effect transistor, using polyacetylene {publication (J. Appl. Phys.
54, p. 3255, 1983)}, using poly (N-methylpyrrole) {Publications (Chem. Let.
t. 863, 1986}, using polythiophene {Publications (Appl. Phys. Lett. 49.
Vol. 1210, 1986)}, using metal phthalocyanines {Publications (Chem. Phys. Let.
t. 145, pp. 343, 1988}, using thiophene oligomers {Publications (Solid Stat
e Comm. 72, p. 381, 1989)} and the like are known.

Here, regarding the field effect transistor,
First, an example using polythiophene will be described. Figure 1
2 shows a cross-sectional view of a conventional transistor using polythiophene as an active layer. Here, 1 is a polythiophene film serving as an active layer, 2 is a gold film serving as a source electrode, 3 is a gold film serving as a drain electrode, 4 is a silicon oxide film serving as a gate insulating film, and 5 is a substrate also serving as a gate electrode. Shaped silicon wafer,
Reference numeral 6 is an electrode for making ohmic contact with the silicon wafer. Next, a method of manufacturing a transistor using this polythiophene as an active layer will be described. A thermal oxide film or a natural oxide film 4 is formed on the surface of an n-type silicon wafer 5 by a conventional method, and a gold film pattern to be the source electrode 2 and the drain electrode 3 is formed thereon by a conventional photolithography method or etching method. Formed and on that electrode a few
The polythiophene film 1 to be the active layer is formed between the electrodes by the electric field polymerization method. The electrode 6 for forming an ohmic contact with the silicon wafer is formed by removing the oxide film on the side opposite to the surface of the silicon substrate on which the source electrode, the drain electrode and the active layer are formed, and applying a Ga—In alloy. In addition to the above-mentioned electric field polymerization method, vacuum deposition method, ion cluster beam method (ICB method), spin coating method, Langmuir-Blodgett method (LB method), etc. have been reported as conventional methods for forming an active layer of an organic transistor. Has been done.

Next, a field effect transistor using oligothiophene will be described as an example. FIG. 13 shows a cross-sectional view of a transistor using oligothiophene as an active layer. Here, 1 is an oligothiophene film serving as an active layer, 2 is a gold film serving as a source electrode, 3 is a gold film serving as a drain electrode, 4 is a silicon oxide film serving as a gate insulating film, and 5 is a substrate also serving as a gate electrode. An n-type silicon wafer 6 is an electrode for making an ohmic contact with the silicon wafer.
A method for manufacturing a transistor using this oligothiophene as an active layer will be described. A thermal oxide film or a natural oxide film 4 is formed on the surface of the n-type silicon wafer 5 by a conventional method, and an oligothiophene film to be an active layer is formed thereon by a vacuum deposition method. Then, the source electrode 2 is formed on the active layer by the usual photolithography method and etching method.
And the pattern of the gold film which becomes the drain electrode 3 is formed. The electrode 6 for forming an ohmic contact with the silicon wafer is formed by removing the oxide film on the side opposite to the surface of the silicon substrate on which the source electrode, the drain electrode and the active layer are formed, and Ga-I
This is done by applying an n alloy. All conventional organic transistors are manufactured by either of the above two methods.

Next, the operation of a transistor using polythiophene as an active layer will be described as an example. When a voltage is applied between the source electrode 2 and the drain electrode 3, a current flows between the source electrode 2 and the drain electrode 3 through the polythiophene film 1. At this time, when a voltage is applied to the silicon plate 5 serving as a gate electrode which is separated from the polythiophene film 1 by the insulating film 4, the polythiophene film 1 is formed by the electric field effect.
Of the source / drain electrodes 2 and 3 can be controlled. It is considered that this is because the width of the storage layer in the polythiophene film 1 adjacent to the insulating film 4 changes depending on the voltage applied to the silicon plate 5, and the channel cross-sectional area of effective positive carriers changes. There is.

[0008]

Among the conventional field effect transistors described above, those using poly (N-methylpyrrole) and polythiophene as the active layer are produced by an electrolytic polymerization method and lack productivity. Further, those using metal phthalocyanines or oligothiophenes as the active layer are produced by a vacuum vapor deposition method and lack productivity with a large vacuum apparatus. In general, most organic materials that can be the active layer of a field effect transistor are insoluble in a solvent. However, as a conductive polymer material obtained from a solvent-soluble precursor having excellent processability, for example, poly (2,5,5)
-Thienylene vinylene) {publications (Polym. Com
mun. 28, p. 229, 1987)}, poly (p-phenylene vinylene) {publication (Polym. C
ommun. 25, p. 327, 1984}, polyacetylene {Publications (Synth. Met. 14: 24.
5 pages, 1986} etc. are reported. These solvent-soluble polymers have excellent moldability and can form a thin film on a large-area substrate by a simple method such as spin coating, and thus have excellent productivity. However, in order to use these materials for the active layer of a field effect transistor, it is necessary to first thin a solvent-soluble precursor and then convert (activate) the precursor into a conductive polymer (semiconductor). .. This conversion process (activation process) is generally performed by heating the precursor thin film, but the conversion often does not proceed efficiently by heating alone. Generally, it is effective to carry out chemical treatment, more specifically acid treatment, in order to accelerate these conversions. However, when chemically treated,
There has been a problem that the source electrode, the drain electrode or the gate electrode causes an undesired chemical change. Further, such a problem also occurs when performing a chemical doping process used to control the electrical characteristics of the organic thin film that is the active layer, and the source electrode, the drain electrode, and the gate electrode are corroded by the chemical doping process. It may cause unfavorable chemical changes.

The present invention has been made to solve the above problems, and prevents deterioration of electrodes, and is an electric field in which an organic semiconductor thin film which is excellent in productivity, lightweight and rich in flexibility can be used as an active layer. The object is to obtain a method for manufacturing an effect transistor.

[0010]

A method of manufacturing a field effect transistor according to the present invention comprises a step of subjecting an organic thin film to be a semiconductor by activation to an organic semiconductor thin film,
A step of forming a source electrode and a drain electrode in the organic semiconductor thin film, and a step of forming a gate electrode so as to control the conductivity between the source electrode and the drain electrode are performed.

According to another aspect of the present invention, there is provided a method of manufacturing a field effect transistor, which comprises a step of providing a gate insulating film on a gate electrode having a terminal, a step of providing an organic thin film to be a semiconductor by activation treatment on the gate insulating film, Performing a step of exposing the terminals of the gate electrode after activating the organic thin film to form an organic semiconductor thin film while protecting the gate electrode, and forming a source electrode and a drain electrode in the organic semiconductor thin film. is there.

[0012]

In the present invention, when the organic thin film is made into the organic semiconductor thin film by the activation treatment, the electrode is not exposed to the activation treatment, so that the intended purpose can be achieved.

[0013]

1 is a cross-sectional view of a field effect transistor according to an embodiment of the present invention, in which 1 is an organic semiconductor thin film serving as an active layer, 2 is a source electrode, 3 is a drain electrode, 4
Is a gate insulating film, 7 is a gate electrode, and 8 is a substrate. 2A to 2E are process diagrams of a method for manufacturing a field effect transistor according to an embodiment of the present invention, in which 11 is an organic thin film which becomes an organic semiconductor by activation treatment. First, the organic thin film 11 is formed on the substrate 8 (FIG. 2A), and the organic thin film 1 is formed.
1 is subjected to a desired activation treatment (chemical treatment and chemical doping treatment) to convert it into an organic semiconductor thin film 1 which serves as an active layer {FIG. 2 (b)}. After that, source and drain electrodes 2 and 3 are formed on the organic semiconductor thin film 1 (see FIG. 2).
(C)}, and then the gate insulating film 4 is formed thereon {FIG. 2 (d)}, and the gate electrode 7 is further formed {FIG. 2
(E)}. By this procedure, the influence on the source electrode 2, the drain electrode 3 and the gate electrode 7 due to the activation treatment such as the chemical treatment and the chemical doping treatment performed on the organic thin film 11 can be avoided.

FIG. 3 is a sectional view of a field effect transistor according to another embodiment of the present invention, in which 1 is an organic semiconductor thin film which becomes an active layer, 2 is a source electrode, 3 is a drain electrode, 4 Is a gate insulating film, 7 is a gate electrode having a terminal, 8 is a substrate, and 11 is an organic thin film which becomes an organic semiconductor by an activation treatment. 4 (a) to 4 (d) are process diagrams of a method for manufacturing a field effect transistor of another embodiment of the present invention, and FIGS. 5 (e) to 5 (f) are views of another invention of the present invention. FIG. 6 is a process chart of a method for manufacturing a field effect transistor of one embodiment, showing a process after FIG. 4D, and 9 is a protective film. First, the gate electrode 7 having terminals is formed on the substrate 8 {FIG. 4A}, and the gate insulating film 4 is formed thereon {FIG. 4B}. Next, an organic thin film 11 serving as an active layer is formed on the gate insulating film 4 {FIG. 4 (c)}, and the exposed portion of the gate electrode not covered with the gate insulating film 4 is covered with the protective film 9 {FIG. 4 (d)}. After that, organic thin film 1
1 is subjected to desired chemical treatment and chemical doping treatment to form an organic semiconductor thin film 1 (FIG. 5 (a)), the protective film 9 is removed to expose the terminal, and the source electrode is formed on the organic semiconductor thin film 1. 2 and the drain electrode 3 are formed. By this procedure, the influence of the chemical treatment and the chemical doping treatment performed on the organic thin film 11 on the source electrode 2, the drain electrode 3 and the gate electrode 7 can be avoided.

6 (a) to 6 (d) are process diagrams of a method for manufacturing a field effect transistor of another embodiment of the present invention, and FIGS. 7 (e) to 7 (f) are views of the present invention. FIG. 7D is a process diagram of a method of manufacturing a field effect transistor according to another embodiment of another invention, which shows a process following that shown in FIG. First, the gate electrode 7 is formed on the substrate 8 {FIG. 6 (a)}, and the gate insulating film 4 is formed thereon {FIG. 6 (b)}. Then, the organic thin film 11 is formed on the gate insulating film 4 {FIG. 6C}. Thereafter, the organic thin film 11 is subjected to desired chemical treatment and chemical doping treatment to obtain the organic semiconductor thin film 1 {FIG.
(D)}. After the above process is completed, the gate insulating film on the gate electrode terminal portion is removed, and the source electrode and the drain electrode 2, 3 are formed on the organic semiconductor thin film 1. By this procedure,
The influence of the chemical treatment and the chemical doping treatment performed on the organic thin film 11 on the source electrode, the drain electrode and the gate electrodes 2, 3 and 7 can be avoided.

As the gate electrode according to the present invention, gold,
Although metals such as platinum, chromium, palladium, aluminum, indium, molybdenum, low resistance polysilicon and low resistance amorphous silicon, tin oxide, indium oxide and indium tin oxide (ITO) are generally used. Of course, it is not limited to these materials, and two or more kinds of these materials may be used. Here, as a method for providing the metal film, there are vapor deposition, sputtering, plating, and various CVD growth methods.
In addition, depending on the purpose of use, it may serve as the gate electrode 7 and the substrate 8,
It is also possible to use a conductive plate such as a silicon wafer, a stainless plate, or a copper plate.

The insulating film 4 according to the present invention may be made of any inorganic or organic material as long as it has an insulating property. Generally, silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, or oxide is used. Titanium, polyethylene, polyester, polyimide, polyphenylene sulfide, polyparaxylene, polyacrylonitrile, various insulating LB films and the like are used, and two or more of these materials may be used in combination. In particular, the above inorganic oxides and nitrides are preferable in order to serve also as a protective film in the gate insulating film shown in the other embodiment of the present invention. The method for forming these insulating films is not particularly limited, and examples thereof include a CVD method, a plasma CVD method, a plasma polymerization method, a vapor deposition method, a spin coating method, a dipping method, a cluster ion beam vapor deposition method, and an LB method. Can also be used. When a silicon wafer is used also as the gate electrode 7 and the substrate 8, a silicon oxide film obtained by a thermal oxidation method of silicon or the like is suitable as the insulating film 4.

The organic thin film which becomes an organic semiconductor by activation treatment such as chemical treatment and chemical doping treatment according to the present invention has a semiconducting property by performing chemical treatment after thin film formation and has an active layer. Any material that works effectively and that has semiconductor characteristics by chemical doping treatment and works effectively as an active layer may be used. Examples of materials that effectively act as an active layer by performing a chemical treatment after forming a thin film include polyacetylene, poly (2,5-thienylenevinylene), poly (2,5-thienylenevinylene) derivatives, poly (2,5 -Furylene vinylene), poly (2,5-furylene vinylene) derivative,
Poly (2,5-phenylene vinylene), poly (2,5-
A π-conjugated polymer obtained by chemically converting a precursor thin film soluble in a solvent such as phenylene vinylene) derivative, polyaniline, poly (N-substituted aniline),
Poly (2-substituted aniline), poly (3-substituted aniline), poly (2,3-disubstituted aniline), and the like, polyanilines capable of having a desired structure by chemical conversion, and these two types Π-Conjugated polymers such as the above copolymers and amphipathic derivatives thereof can be used.
Here, the number of repeating units of these polymers is not limited, and an oligomer having 4 or more repeating units can also be used.
The π-conjugated polymer obtained by chemically converting from the solvent-soluble precursor thin film may be converted by heat treatment as well. It is possible to increase the conversion efficiency by using them together. Among the above-mentioned π-conjugated polymers, poly (2,5-thienylenevinylene), poly (2,5-thienylenevinylene) derivatives, poly (2,5-furylene) are particularly preferable in view of transistor characteristics and stability thereof. Vinylene), poly (2,5-furylenevinylene) derivative, poly (2,5-)
Phenylene vinylene), poly (2,5-phenylene vinylene) derivative and the like are preferable. In the chemical formula (1), polyarylene vinylene

[0019]

[Chemical 1]

The chemical structural formula is shown below. By chemical doping treatment, as an active layer effectively controlling the electrical properties of the organic thin film, for example, porphyrins, metalloporphyrins, phthalocyanines, metal phthalocyanines, low molecular weight organic semiconductors such as merocyanine and , Tetrathiafulvalene (TTF), tetracyanoquinodimethane (TCNQ), and their complexes (TTF-T
Various low molecular weight compounds represented by CNQ) and high molecular weight charge transfer complexes can also be used, and two or more kinds of these compounds may be used in combination. Furthermore, for example, polyacetylene, polypyrrole, poly (N-substituted pyrrole), poly (3-substituted pyrrole), poly (3,4-disubstituted pyrrole), polythiophene, poly (3-substituted thiophene),
Poly (3,4-disubstituted thiophene), polybenzothiophene, polyisothianaphthene, poly (p-phenylene vinylene), poly (p-phenylene vinylene) derivative, poly (2,5-thienylene vinylene), poly ( 2,5-thienylene vinylene) derivative, poly (2,5-furylene vinylene), poly (2,5-furylene vinylene) derivative,
Polyaniline, poly (N-substituted aniline), poly (2-
Substituted aniline), poly (3-substituted aniline), poly (2,3-disubstituted aniline), polydiacetylenes, polyazulene, polypyrene, polycarbazole, poly (N
-Substituted carbazole), polyselenophene, polyfuran, polybenzofuran, polyparaphenylene, polyparaphenylenevinylene, polyindole, polypyridazine, polyacene and graphitic polymers, and copolymers of two or more kinds thereof and their parents. A π-conjugated polymer such as a medium derivative can be used. Here, the number of repeating units of these polymers is not limited, and an oligomer having 4 or more repeating units can also be used.

As methods for producing these organic thin films, vacuum vapor deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, plasma polymerization method, electrolytic polymerization method , A chemical polymerization method, a spin coating method, a casting method, a dipping method, a roll coating method, a bar coating method, an LB method and the like, and they can be used depending on the material. However, among these, in terms of productivity, a spin coating method, a casting method, a dipping method, which can easily form a thin film,
A roll coat method, a bar coat method, etc. are preferred. The thickness of the thin film made of these organic semiconductors is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the thickness of the active layer made of an organic semiconductor. Although it varies depending on the semiconductor, it is generally preferably 3000 angstroms or less. An organic thin film that works effectively as an active layer by chemical treatment after thin film formation
The electrical properties are often controlled by the doping process, but unless other components are chemically altered,
(1) doping from the gas phase, (2) doping from the liquid phase, (3) electrochemical doping, (4) chemical doping such as photoinitiated doping and publications {industrial materials, Vol. 34, No. 4 , 55, 1986}, any of the physical doping methods such as ion implantation may be used.

The protection of the gate electrode in the step of activating the organic thin film according to another invention of the present invention is carried out when the gate electrode is coated with the gate insulating film at the same time when the gate insulating film is provided (FIG. 6, FIG. 7) is not necessary, but when a part of the gate electrode is exposed, the exposed part needs to be provided with a protective film that is resistant to chemical treatment and chemical doping treatment and that effectively protects the electrode. .. Examples of the protective film include ordinary novolac-based, chlorinated polystyrene-based, PMMA-based, polyvinylphenol-based resist materials and the like.

Any insulating material can be used for the substrate according to the present invention. Specifically, glass, alumina sintered body, polyimide film, polyester film, polyethylene film, polyphenylene sulfide film, poly Various insulating plastics such as paraxylene film can be used. Hereinafter, more specific examples will be described, but of course this does not limit the present invention.

Example 1. It is represented by the structural formula (2) on a non-alkali glass wafer having a diameter of 2 inches and a thickness of 0.7 mm, which is a substrate.

[0025]

[Chemical 2]

A 2 wt% dimethylformamide solution of a precursor polymer of poly (2,5-thienylenevinylene) was spin-coated on the element substrate to obtain an organic thin film. Spin coating, rotation speed: 4000 rpm, rotation time: 60
Sec., Atmospheric temperature: 60 ° C., in air. The thin film made of the precursor polymer thus formed was sufficiently dried and then subjected to a chemical treatment by heating at 200 ° C. for 60 minutes under a nitrogen stream containing hydrogen chloride gas using an infrared gold image furnace. The organic semiconductor thin film used as an active layer was obtained. To supply hydrogen chloride gas, pour nitrogen gas over the hydrochloric acid reagent stock solution in the gas cleaning bottle, dry the nitrogen gas containing hydrogen chloride gas flowing out of this gas cleaning bottle with concentrated sulfuric acid and a calcium chloride drying tube, and then in the image furnace. It was done by flowing into. After the above heat treatment, poly (2,5-
The precursor polymer of thienylene vinylene) is represented by the structural formula (3).

[0027]

[Chemical 3]

It was converted to poly (2,5-thienylene vinylene) to give a glossy brown very homogeneous film.
The conversion of this precursor polymer into poly (2,5-thienylene vinylene) is seen in the infrared absorption spectrum of the organic semiconductor film obtained by the chemical treatment according to the embodiment of the present invention shown in FIG. .. That is, the absorption of C—O—C stretching vibration of 1100 cm ⁻¹ based on the side chain ether bond of the precursor polymer disappears, and the transbin of 1590 cm ⁻¹ based on the vinylene bond of poly (2,5-thienylene vinylene) disappears. This was confirmed by the appearance of absorption of out-of-plane bending vibration of Len C-H. FIG. 9 shows, for comparison, the infrared absorption spectrum of the above organic thin film that was subjected only to heat treatment. Further, the conversion of the precursor polymer into poly (2,5-thienylene vinylene) is seen in the electronic spectrum, and after the heat treatment, absorption based on π-π ^* having a maximum at about 530 nm appears, resulting in a single Π − due to repeating bonds and double bonds
It was also confirmed from the fact that a conjugated bond was formed. Then, an indium tin oxide (ITO) thin film pattern having a thickness of 1000 angstrom was formed on the poly (2,5-thienylene vinylene) film of the organic semiconductor film by using a usual vapor deposition method, photolithography method and etching method. Formed. An SiO _x insulating film having a thickness of 5000 angstrom was formed thereon by using a usual vapor deposition method and a mask method. Further, a chrome thin film pattern having a thickness of 1000 angstrom was formed thereon by the usual vapor deposition method, photolithography method and etching method to obtain a field effect transistor according to an embodiment of the present invention. The transistor thus obtained is composed of an insulated gate field effect transistor and has the cross section shown in FIG. In this case, 1 is a PTV film serving as an active layer, 2 is an ITO film serving as a source electrode, 3 is an ITO film serving as a drain electrode, 4 is a SiO ₂ vapor deposition film serving as a gate insulating film, and 7 is a chromium film serving as a gate electrode. , 8 are glass wafer element substrates. here,
Poly (2,5-thienylene vinylene) exhibits semiconductor characteristics without any doping treatment and acts as an active layer of a transistor. The channel width (W) and channel length (L) of the above transistor are 2 mm and 2.5 μ, respectively.
m. FIG. 10 is an electrical characteristic diagram comparing a transistor according to an embodiment of the present invention with a conventional transistor,
The horizontal axis represents the gate voltage of the transistor (V _G), with the vertical axis channel current (I _D), the source-drain voltage V _DS = -2
The static characteristics at 0v are shown. In the figure, A is the electrical characteristics of the transistor according to one embodiment of the present invention.

Comparative Example 1. A transistor was obtained in the same manner as in Example 1 except that the organic thin film was not chemically treated, and its electrical characteristics were measured in the same manner as in Example 1. The electric characteristics are shown by C in FIG.

As shown in FIG. 10, the field-effect transistor obtained in Example 1, which uses an organic semiconductor thin film obtained by chemical treatment without damaging the electrodes as an active layer, has an ON current of about one digit as compared with the conventional one. You can see that you can increase. Carrier mobility is approximately 1 × 10 ^-1 cm ² / V · s
ec was required.

Example 2. A chrome pattern having a thickness of 1000 Å was formed on a non-alkali glass wafer having a diameter of 2 inches and a thickness of 0.7 mm, which is a substrate, by using a usual vapor deposition method, photolithography method and etching method. An SiO _x insulating film having a thickness of 5000 angstrom was formed thereon by using a usual vapor deposition method and a mask method. As in Example 1, 2 of the precursor polymer of poly (2,5-thienylenevinylene) represented by the chemical formula (1) was used.
A wt% dimethylformamide solution was spin-coated on the element substrate. Spin coating speed: 4000r
pm, rotation time: 60 seconds, ambient temperature: 60 ° C. in air. On the exposed portion of the chromium electrode which is not covered with the insulating film, such as the electrode lead-out portion, there is a normal novolac-based positive resist film AZ13 as a protective film for the chromium electrode.
50 was coated to a thickness of 1.5 μm.

The organic thin film made of the precursor polymer thus formed was sufficiently dried and then subjected to an infrared gold image furnace under a nitrogen stream containing hydrogen chloride gas for 20 minutes.
A chemical treatment was carried out by heating at 0 ° C. for 60 minutes to obtain an organic semiconductor thin film. To supply hydrogen chloride gas, pour nitrogen gas onto the hydrochloric acid reagent stock solution in the gas cleaning bottle, dry the nitrogen gas containing hydrogen chloride gas flowing out from this gas cleaning bottle with concentrated sulfuric acid and a calcium chloride drying tube, and then in the image furnace. It was done by flowing into. Similar to Example 1, after the heat treatment, the precursor polymer of poly (2,5-thienylenevinylene) was poly (2,5) represented by the chemical formula (2).
-Thienylene vinylene) resulting in a glossy brown very homogeneous film.

The conversion of this precursor polymer into poly (2,5-thienylenevinylene) was carried out in the infrared absorption spectrum of the film after chemical treatment by C-at 1100 cm ^-1 based on the side chain ether bond of the precursor polymer. Absorption of OC stretching vibration disappeared, and poly (2,5-thienylene vinylene)
It was confirmed by the absorption of the transbinlen C—H out-of-plane bending vibration at 1590 cm ⁻¹ based on the vinylene bond of ¹ . In addition, poly (2,5-
Thienylene vinylene) is converted into π having a maximum at about 530 nm in the electronic spectrum after the above heat treatment.
This was also confirmed by the appearance of absorption based on −π ^* and the formation of a π-conjugated bond by repeating single and double bonds.

Next, AZ1350, which is a novolac-based positive resist, on the electrode not covered with the insulating film such as the electrode extraction portion was removed with acetone. After that, a 300 angstrom thick chromium thin film was formed on the poly (2,5-thienylene vinylene) film by a conventional vapor deposition method, and subsequently a 700 angstrom thick gold thin film was formed thereon. Here, the underlying chromium was used for the purpose of improving the adhesion between the gold electrode and the poly (2,5-thienylene vinylene) film. Next, this gold electrode having chromium as a base was patterned into a desired shape by a usual photolithography method and etching method to obtain a field effect transistor according to another embodiment of the present invention. The transistor thus obtained is composed of an insulated gate field effect transistor and has a cross section shown in FIG. here,
1 is a PTV film which will be an active layer, 2 is a gold film which will be a source electrode, 3 is a gold film which will be a drain electrode, 4 is a SiO ₂ vapor deposition film which will be a gate insulating film, 7 is a chromium film which is a gate electrode,
8 is a glass wafer element substrate. Where poly (2,
5-thienylene vinylene) exhibits semiconductor characteristics without any doping treatment and acts as an active layer of a transistor. The channel width (W) and the channel length (L) of the above transistor are 2 mm and 2.5 μm, respectively. Figure 1
In 0, B shows electrical characteristics of the obtained transistor.
According to this, the same characteristics as in Example 1 were obtained, and by using the organic semiconductor thin film obtained by performing the chemical treatment without damaging the electrode as the active layer, the ON current was increased by about one digit compared with the conventional one. I know what I can do. The carrier mobility was determined to be approximately 1 × 10 ⁻¹ cm ² / V · sec.

Example 3. On a non-alkali glass wafer having a diameter of 2 inches and a thickness of 0.7 mm, which is a substrate, poly (3
-Hexylthiophene) in a 5 wt% chloroform solution was spin-coated on the device substrate to obtain an organic thin film. Spin coating, rotation speed: 4000 rpm, rotation time: 60
Second, atmosphere temperature: 20 ° C., and nitrogen atmosphere. The organic thin film thus formed was sufficiently dried and then subjected to chemical doping treatment in a nitrogen stream containing hydrogen chloride gas to obtain an organic semiconductor thin film. To supply hydrogen chloride gas, pour nitrogen gas over the hydrochloric acid reagent stock solution in the gas cleaning bottle, dry the nitrogen gas containing hydrogen chloride gas flowing out of this gas cleaning bottle with concentrated sulfuric acid and a calcium chloride drying tube, and then in the glow box. It was done by flowing into. By this doping treatment, the electric conductivity is 10 ⁻⁸ S / cm to 10 ⁻⁶ S / cm.
Increased.

Then, a 300 Å thick chromium thin film is formed on the doped poly (3-hexylthiophene) by a conventional vapor deposition method, and then a 700 Å thick gold thin film is formed thereon. A thin film was formed. Here, the underlying chromium was used for the purpose of improving the adhesion between the gold electrode and the poly (3-hexylthiophene) film. Next, this chromium-based gold electrode was patterned into a desired shape by a usual photolithography method and etching method. An SiO _x insulating film having a thickness of 5000 angstrom was formed thereon by using a usual vapor deposition method and a mask method. Further, a chromium thin film pattern having a thickness of 1000 angstrom was formed thereon by using the ordinary vapor deposition method, the photolithography method and the etching method to obtain a field effect transistor according to another embodiment of the present invention.

The transistor thus obtained is composed of an insulated gate field effect transistor and has the cross section shown in FIG. In this case, 1 is a poly (3-hexylthiophene) film to be an active layer, 2 is a gold film to be a source electrode, 3 is a gold film to be a drain electrode, and 4 is Si to be a gate insulating film.
An O ₂ vapor deposition film, 7 is a chromium film as a gate electrode, and 8 is a glass wafer element substrate. The channel width (W) and channel length (L) of the above transistor are 2 mm and 2.5, respectively.
μm. FIG. 11 is an electrical characteristic diagram comparing a transistor according to another embodiment of the present invention with a conventional transistor. In the figure, D indicates the electrical characteristic of the transistor obtained in the third embodiment. The horizontal axis represents the gate voltage of the transistor (V _G), the vertical axis represents the static characteristic of the source-drain voltage V _DS = -20 V in the channel current (I _D).

Comparative Example 2. In Example 3, a transistor was obtained in the same manner as in Example 3 except that the organic thin film was not chemically doped, and its electrical characteristics were measured in the same manner as in Example 1. The electrical characteristics are shown by E in FIG.

As shown in FIG. 11, the field effect transistor obtained in Example 3 in which the organic semiconductor thin film obtained by performing the chemical doping treatment without damaging the electrode was used as the active layer, the ON current was about one digit higher than that of the conventional one. It turns out that can be increased. Carrier mobility is approximately 1 × 10 ⁻³ cm ^2.
/ V · sec was required.

Example. A chrome pattern having a thickness of 1000 A was formed on a non-alkali glass wafer having a diameter of 2 inches and a thickness of 0.7 mm, which is four substrates, by using a usual vapor deposition method, photolithography method and etching method. On top of that, a thickness of 5000 is obtained by using a usual vapor deposition method and a mask method.
The SiO _x insulating film A was formed on the entire surface of the substrate. As in Example 1, a 2 wt% dimethylformamide solution of a precursor polymer of poly (2,5-thienylenevinylene) represented by Chemical Formula 2 was spin-coated on the element substrate. Spin coating, rotation speed: 4000 rpm, rotation time: 60
Sec., Atmospheric temperature: 60 ° C., in air. afterwards,
This precursor polymer was patterned by the usual lithography method and etching method.

The precursor polymer pattern thus formed was sufficiently dried and then subjected to a chemical treatment by heating it at 200 ° C. for 60 minutes under a nitrogen stream containing hydrogen chloride gas using an infrared gold image furnace. gave. To supply hydrogen chloride gas, pour nitrogen gas over the hydrochloric acid reagent stock solution in the gas cleaning bottle, dry the nitrogen gas containing hydrogen chloride gas flowing out of this gas cleaning bottle with concentrated sulfuric acid and a calcium chloride drying tube, and then in the image furnace. It was done by flowing into. As in Example 1, after the above heat treatment, poly (2,5
The precursor polymer of thienylene vinylene) has the formula 3
Was converted into poly (2,5-thienylenevinylene) represented by the formula (3) to give a glossy brown extremely uniform film.

The conversion of this precursor polymer to poly (2,5-thienylene vinylene) was carried out by the infrared absorption spectrum of the film after chemical treatment, and the C of 1100 cm ^-1 based on the side chain ether bond of the precursor polymer was used. It was confirmed that absorption of -OC stretching vibration disappeared, and absorption of transbinlen C-H out-of-plane bending vibration at 1590 cm ^-1 based on vinylene bond of poly (2,5-thienylene vinylene) appeared. It was In addition, the conversion of the precursor polymer into poly (2,5-thienylenevinylene) is carried out by an electronic spectrum, and π- having a maximum at about 530 nm after the heat treatment.
It was also confirmed from the appearance of absorption based on π ^* and the formation of π-conjugated bond by repeating single bond and double bond.

Next, by photolithography using a resist material, only the insulating film on the electrode, such as the electrode lead-out portion, which needs to be exposed, was etched with a mixed solution of hydrofluoric acid and ammonium fluoride. Then, a poly (2,5-thienylene vinylene) film was formed on the poly (2,5-thienylene vinylene) film to a thickness of
00A chrome thin film is formed, and then a thickness of 7
A gold thin film of 00A was formed. Here, the underlying chromium was used for the purpose of improving the adhesion between the gold electrode and the poly (2,5-thienylene vinylene) film. Next, this chromium-based gold electrode was patterned into a desired shape by a usual photolithography method and etching method.

The transistor thus obtained is composed of an insulated gate field effect transistor. FIG. 3 shows a cross-sectional view of the transistor. Here, 1 is P which becomes an active layer
TV film, 2 is a gold film serving as a source electrode, 3 is a gold film serving as a drain electrode, 4 is a SiO _x vapor deposition film serving as a gate insulating film,
Reference numeral 7 is a chromium film which is a gate electrode, and 8 is a glass wafer element substrate. Here, poly (2,5-thienylenevinylene) exhibits semiconductor characteristics without any doping treatment and acts as an active layer of a transistor. The channel width (W) and the channel length (L) of the above transistor are 2 mm and 2.5 μm, respectively. The transistor showed the same characteristics as the electric characteristics of the transistor obtained in Example 3 shown in FIG.
Similar to Example 3, the same characteristics as in Example 1 were obtained, and by using an organic thin film that had been chemically treated without deteriorating the element structure as the active layer, the ON current was increased by about one digit compared to the conventional case. I know what I can do. Carrier mobility is about 1
It was determined to be × 10 ^-1 cm ² / V · sec.

[0045]

As described above, according to the present invention, a step of activating an organic thin film to be a semiconductor by an activation treatment to form an organic semiconductor thin film, a step of forming a source electrode and a drain electrode on the organic semiconductor thin film, And a step of forming a gate electrode so as to control the conductivity between the source electrode and the drain electrode, and another aspect of the present invention is to provide a gate insulating film on the gate electrode having a terminal. A step of providing an organic thin film which becomes a semiconductor by an activation treatment on the gate insulating film, a step of exposing the terminal of the gate electrode after the organic thin film is activated by the activation treatment of the organic thin film while protecting the gate electrode, In addition, by performing a step of forming a source electrode and a drain electrode on the organic semiconductor thin film, alteration of the electrode is prevented and productivity is improved. Excellent, it can be obtained a method of manufacturing a field effect transistor which can be used an organic semiconductor thin film rich in flexibility, lightweight as an active layer.

[Brief description of drawings]

FIG. 1 is a sectional view of a field effect transistor according to an embodiment of the present invention.

FIG. 2 is a process drawing for manufacturing a field effect transistor according to an embodiment of the present invention.

FIG. 3 is a sectional view of a field effect transistor according to another embodiment of the present invention.

FIG. 4 is a process drawing for manufacturing a field-effect transistor according to another embodiment of the present invention.

FIG. 5 is a process drawing for manufacturing a field-effect transistor according to another embodiment of the present invention.

FIG. 6 is a process drawing for manufacturing a field effect transistor according to another embodiment of another invention of the present invention.

FIG. 7 is a process drawing for manufacturing a field-effect transistor according to another embodiment of the present invention.

FIG. 8 is an infrared absorption spectrum diagram of an organic semiconductor film obtained by a chemical treatment according to an example of the present invention.

FIG. 9 is an infrared absorption spectrum diagram of an organic thin film that is not chemically treated.

FIG. 10 is an electrical characteristic diagram comparing a transistor according to the present invention with a conventional one.

FIG. 11 is an electrical characteristic diagram comparing a transistor according to the present invention with a conventional one.

FIG. 12 is a cross-sectional view of a conventional transistor.

FIG. 13 is a cross-sectional view of a conventional transistor.

[Explanation of symbols]

 1 Organic Semiconductor Film 2 Source Electrode 3 Drain Electrode 4 Gate Insulating Film 7 Gate Electrode 11 Organic Thin Film

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[Procedure amendment]

[Submission date] February 4, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

Specifically, a Schottky junction element using polyacetylene {publication (J. Appl. Phys.
52, p.869, 1981) and JP-A-56-1.
No. 47486, etc.}, Schottky junction device using polypyrrole-based polymer {publication (J. Appl. Phy
s. 54, 2511, 1983) and JP-A-5
No. 9-63760, etc.} are known. Further, a heterojunction device in which n-type CdS which is an inorganic semiconductor and p-type polyacetylene are combined has been reported {publication (J. Appl. Phys. 51, 4252, 19:
80 years)}. As a junction element in which organic semiconductors are combined, p-type and p-type using n-type polyacetylene are used.
n homojunction elements are known {publications (Appl. P
hys. Lett. 33, p. 18, 1978)}.
Further, a heterojunction element composed of polypyrrole and polythiophene {publication (Jpn. J. Appl. Phys. 2
4 (L553, 1985)}, a heterojunction device composed of polyacetylene and poly N-methylpyrrole {Journal (J. Appl. Phys. 58, 1279, 1
985)} is also known.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

Next, a field effect transistor using oligothiophene will be described as an example. FIG. 13 shows a cross-sectional view of a transistor using oligothiophene as an active layer. Here, 1 is an oligothiophene film serving as an active layer, 2 is a gold film serving as a source electrode, 3 is a gold film serving as a drain electrode, 4 is a silicon oxide film serving as a gate insulating film, and 5 is a substrate also serving as a gate electrode. An n-type silicon wafer 6 is an electrode for making an ohmic contact with the silicon wafer.
A method for manufacturing a transistor using this oligothiophene as an active layer will be described. A thermal oxide film or a natural oxide film 4 is formed on the surface of the n-type silicon wafer 5 by a conventional method, and an oligothiophene film to be an active layer is formed thereon by a vacuum deposition method. Then on top of this active layer a normal
The pattern of the gold film to be the source electrode 2 and the drain electrode 3 is formed by the mask method . The electrode 6 for forming an ohmic contact with the silicon wafer is formed by removing the oxide film on the side opposite to the surface of the silicon substrate on which the source electrode, the drain electrode and the active layer are formed, and applying a Ga—In alloy. All of the conventional organic transistors are described above.
Except for the method of forming the active layer, the method is prepared by either of the above two methods.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

[0019]

[Chemical 1]

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

Any insulating material can be used for the substrate according to the present invention. Specifically, glass and stone are used.
In the UK , various insulating plastics such as alumina sintered bodies, polyimide films, polyester films, polyethylene films, polyphenylene sulfide films, and polyparaxylene films can be used. Hereinafter, more specific examples will be described, but of course this does not limit the present invention.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

It was converted to poly (2,5-thienylene vinylene) to give a glossy brown very homogeneous film.
The conversion of this precursor polymer into poly (2,5-thienylene vinylene) is seen in the infrared absorption spectrum of the organic semiconductor film obtained by the chemical treatment according to the embodiment of the present invention shown in FIG. .. That is, the absorption of C—O—C stretching vibration of 1100 cm ⁻¹ based on the side chain ether bond of the precursor polymer disappears, and the transbin of 1590 cm ⁻¹ based on the vinylene bond of poly (2,5-thienylene vinylene) disappears. This was confirmed by the appearance of absorption of out-of-plane bending vibration of Len C-H. FIG. 9 shows, for comparison, the infrared absorption spectrum of the above organic thin film that was subjected only to heat treatment. Further, the conversion of the precursor polymer into poly (2,5-thienylene vinylene) is seen in the electronic spectrum, and after the heat treatment, absorption based on π-π ^* having a maximum at about 530 nm appears, resulting in a single Π − due to repeating bonds and double bonds
It was also confirmed from the fact that a conjugated bond was formed. Then, an indium tin oxide (ITO) thin film pattern having a thickness of 1000 angstrom was formed on the poly (2,5-thienylene vinylene) film of the organic semiconductor film by using a usual sputtering method, a photolithography method and an etching method. Formed. An SiO _x insulating film having a thickness of 5000 angstrom was formed thereon by using a usual vapor deposition method and a mask method. Further, a thickness of 100 is formed thereon by using a conventional vapor deposition method, a photolithography method and an etching method.
A 0 Å chrome thin film pattern was formed to obtain a field effect transistor according to an embodiment of the present invention. The transistor thus obtained is composed of an insulated gate field effect transistor and has the cross section shown in FIG. In this case, 1 PTV film serving as an active layer, ITO film serving as a source electrode 2, ITO film serving as the drain electrode 3, Si O _X deposited film to be the gate insulating film 4, 7 denotes a gate electrode of chromium The film, 8 is a glass wafer element substrate. Here, poly (2,5-thienylenevinylene) exhibits semiconductor characteristics without any doping treatment and acts as an active layer of a transistor. The channel width (W) and channel length (L) of the above transistor are 2 mm and 2.5 μ, respectively.
m. FIG. 10 is an electrical characteristic diagram comparing a transistor according to an embodiment of the present invention with a conventional transistor,
The horizontal axis represents the gate voltage of the transistor (V _G), with the vertical axis channel current (I _D), the source-drain voltage V _DS = -2
The static characteristics at 0v are shown. In the figure, A is the electrical characteristics of the transistor according to one embodiment of the present invention.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

Example 2. A chrome pattern having a thickness of 1000 Å was formed on a non-alkali glass wafer having a diameter of 2 inches and a thickness of 0.7 mm, which is a substrate, by using a usual vapor deposition method, photolithography method and etching method. An SiO _x insulating film having a thickness of 5000 angstrom was formed thereon by using a usual vapor deposition method and a mask method. As in Example 1, 2 of the precursor polymer of poly (2,5-thienylenevinylene) represented by the chemical formula (1) was used.
A wt% dimethylformamide solution was spin-coated on the element substrate. Spin coating speed: 4000r
pm, rotation time: 60 seconds, ambient temperature: 60 ° C. in air. Such as electrode extraction portion, the chromium electrode exposed part on which is not covered by the insulating film, a conventional novolak type positive resist as a protective film of chromium electrode AZ13
50 was coated to a thickness of 1.5 μm.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

Next, AZ1350, which is a novolac-based positive resist, on the electrode not covered with the insulating film such as the electrode extraction portion was removed with acetone. After that, a 300 angstrom thick chromium thin film was formed on the poly (2,5-thienylene vinylene) film by a conventional vapor deposition method, and subsequently a 700 angstrom thick gold thin film was formed thereon. Here, the underlying chromium was used for the purpose of improving the adhesion between the gold electrode and the poly (2,5-thienylene vinylene) film. Next, this gold electrode having chromium as a base was patterned into a desired shape by a usual photolithography method and etching method to obtain a field effect transistor according to another embodiment of the present invention. The transistor thus obtained is composed of an insulated gate field effect transistor and has a cross section shown in FIG. here,
1 is a PTV film which will be an active layer, 2 is a gold film which will be a source electrode, 3 is a gold film which will be a drain electrode, 4 is a SiO _x vapor deposition film which will be a gate insulating film, 7 is a chromium film which is a gate electrode,
8 is a glass wafer element substrate. Where poly (2,
5-thienylene vinylene) exhibits semiconductor characteristics without any doping treatment and acts as an active layer of a transistor. The channel width (W) and the channel length (L) of the above transistor are 2 mm and 2.5 μm, respectively. Figure 1
In 0, B shows electrical characteristics of the obtained transistor.
According to this, the same characteristics as in Example 1 were obtained, and by using the organic semiconductor thin film obtained by performing the chemical treatment without damaging the electrode as the active layer, the ON current was increased by about one digit compared with the conventional one. I know what I can do. The carrier mobility was determined to be approximately 1 × 10 ⁻¹ cm ² / V · sec.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

The transistor thus obtained is composed of an insulated gate field effect transistor and has the cross section shown in FIG. In this case, 1 is a poly (3-hexylthiophene) film to be an active layer, 2 is a gold film to be a source electrode, 3 is a gold film to be a drain electrode, and 4 is Si to be a gate insulating film.
An O _x vapor deposition film, 7 is a chromium film as a gate electrode, and 8 is a glass wafer element substrate. The channel width (W) and channel length (L) of the above transistor are 2 mm and 2.5, respectively.
μm. FIG. 11 is an electrical characteristic diagram comparing a transistor according to another embodiment of the present invention with a conventional transistor. In the figure, D indicates the electrical characteristic of the transistor obtained in the third embodiment. The horizontal axis represents the gate voltage of the transistor (V _G), the vertical axis represents the static characteristic of the source-drain voltage V _DS = -20 V in the channel current (I _D).

Claims (2)

[Claims] 1. A step of activating an organic thin film that becomes a semiconductor by an activation treatment to form an organic semiconductor thin film, a step of forming a source electrode and a drain electrode on the organic semiconductor thin film, and a step between the source electrode and the drain electrode. A method of manufacturing a field effect transistor, which comprises the step of forming a gate electrode so as to control the conductivity of the field effect transistor. 2. A step of providing a gate insulating film on a gate electrode having a terminal, a step of providing an organic thin film which becomes a semiconductor on the gate insulating film by an activation treatment, and activating the organic thin film while protecting the gate electrode. A method for manufacturing a field effect transistor, which comprises a step of exposing a terminal of the gate electrode after processing to form an organic semiconductor thin film, and a step of forming a source electrode and a drain electrode on the organic semiconductor thin film.