JP2004207331A - Organic semiconductor device and method of manufacturing the same - Google Patents

Abstract

An object of the present invention is to improve the characteristics of an organic semiconductor element, reduce the manufacturing cost, and simplify the manufacturing process.
An organic semiconductor device having a source electrode, a drain electrode, an active semiconductor layer made of an organic semiconductor material connecting the source electrode and the drain electrode, and a gate electrode, wherein the active layer is a plasma under atmospheric pressure. An organic semiconductor element, which is arranged so as to be sandwiched between insulating films formed by processing.
[Selection diagram] Fig. 1

Description

【００５８】
実施例Ａ、Ｂでは大気圧プラズマ法で形成された２つの絶縁膜（第１、第２の絶縁膜）で有機半導体層が挟みこまれることにより、絶縁膜の一方がない比較例１に比して、ドレイン電流（リーク電流）が低減しており、またスイッチング動作としてＯＮ／ＯＦＦ比が大きく向上していることが分かる。特に絶縁膜の形成方法が異なる比較例２，３と比較すると、絶縁膜の形成方法として大気圧プラズマ法がドレイン電流（リーク電流）、ＯＮ／ＯＦＦ比における性能に大きく寄与していることが分かる。
こうした効果は素子の配置を変えた実施例Ｃ（ゲート電極を有機半導体層の上部に配置）でも同様に認められることが比較例４との比較によって分かる。
すなわち有機半導体材料によって形成された活性半導体層では、大気圧プラズマ法で形成された２つの絶縁膜（第１、第２の絶縁膜）との組み合わせ、および活性半導体層を挟み込む配置により非常に良好な特性を示すことが分かった。
また各実施例と比較例におけるＩ、ＲとＩｎ、Ｒｎの比較から本発明のように大気圧プラズマ法で形成された２つの絶縁膜（第１、第２の絶縁膜）で有機半導体層が挟みこまれることにより、その性能を高いレベルで長期に渡り維持することができた。
【００５９】
【発明の効果】
以上のことから本発明によれば、有機半導体材料が薄膜ＴＦＴ内の活性半導体層として使用される際のデバイスのオン／オフ比やリーク電流、等の特性および安定性が向上し、これまでの絶縁膜と有機半導体材料との組み合わせより、優れた薄膜トランジスタの効果が得られる。さらに大気圧環境下での成膜が可能であり、真空工程を必要としないことから製造コストの低減、製造プロセスの簡略化を実現するものである。
【図面の簡単な説明】
【図１】本発明の有機半導体素子の構成を示す概略図である。
【図２】従来のSi半導体を用いたＴＦＴ素子をディスプレイパネル基板上に形成した様子を示す図である。
【図３】本発明の素子の評価系を示す図である。
【図４】本発明における大気圧プラズマ成膜処理を行う装置を示す図である。
【符号の説明】
２５：ロール電極
３１：プラズマ発生処理容器
３６：電極
４１：電源
５１：ガス発生装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic semiconductor device including an organic semiconductor active layer (an active semiconductor layer formed of an organic semiconductor material) and a method of manufacturing the same.
[0002]
[Prior art]
With the spread of information terminals, needs for flat panel displays as displays for computers are increasing. In addition, with the progress of computerization, information provided in the form of paper has been provided electronically, and the number of opportunities to provide the information has increased, and electronic paper or digital media has become a thin, light, and portable mobile display medium. The need for paper is also growing.
[0003]
In general, display devices use liquid crystal, organic EL, electrophoresis, and other elements to form a display medium. In such a display medium, image driving is performed to ensure uniformity of screen luminance and screen rewriting speed. A technique using an active driving element (TFT element) as an element has become mainstream. For example, in a general computer display, these TFT elements are formed on a glass substrate, and a liquid crystal, an organic EL, and the like are sealed.
Here, semiconductors such as a-Si (amorphous silicon) and p-Si (polysilicon) can be mainly used for the TFT element. For example, as shown in FIG. ), And a TFT element is manufactured by sequentially forming a source, a drain, and a gate electrode on a substrate (for example, Patent Document 1 below). The production of such a TFT element usually requires sputtering and other vacuum-based production processes.
[0004]
On the other hand, recently, an organic material has been studied for use as an active semiconductor layer in a thin film transistor (TFT). Organic materials are easy to process and generally have a high affinity for a plastic substrate on which TFTs are formed, and thus are expected to be used as active semiconductor layers in thin film devices. Accordingly, studies have been made on low-cost and large-area devices, particularly active drive elements for displays (for example, Patent Documents 2 and 3 below).
[Patent Document 1]
Japanese Patent Application Laid-Open No. 9-31321 [Patent Document 2]
JP-A-10-190001 [Patent Document 3]
JP 2000-307172 A
[Problems to be solved by the invention]
However, in the case of manufacturing a TFT device using a Si semiconductor as in the former, each layer must be formed by repeating a vacuum-based manufacturing process including a vacuum chamber many times, and the equipment cost and running cost are extremely enormous. Had become something. Usually, in such a TFT device, it is necessary to repeat processes such as sputtering, CVD, and photolithography for forming each layer many times, and the device is formed on the substrate through dozens of processes.
[0006]
In such a conventional manufacturing method using a Si semiconductor, it is not easy to change the equipment, for example, a large design change of a manufacturing apparatus such as a vacuum chamber is required to meet the need for a large display screen.
Also, the gate insulating film of the transistor is generally formed of a silicon oxide film formed by thermal oxidation of a silicon substrate or an oxide thin film formed by a dry process such as sputtering.
[0007]
When an organic material is used as the active semiconductor layer in the TFT as in the latter, processing may be easy, but the ON / OFF ratio, leak current, stability and life of the resulting device are sufficiently high. Is not easy, and a specific method and an element configuration for realizing such characteristics have not been found so far.
An object of the present invention is to realize an organic semiconductor device in which characteristics and stability as a semiconductor device are improved while manufacturing costs are reduced and a manufacturing process is simplified.
[0008]
[Means for Solving the Problems]
The above object of the present invention has been achieved by each of the following constitutions.
(1) An organic semiconductor device having a source electrode, a drain electrode, an active semiconductor layer made of an organic semiconductor material connecting the source electrode and the drain electrode, and a gate electrode, wherein the active layer is subjected to plasma treatment under atmospheric pressure. Or (2) forming a first insulating film by plasma treatment under atmospheric pressure, wherein the first insulating film is disposed so as to be sandwiched between insulating films formed by Arranging a source electrode and a drain electrode as a channel on the film, arranging an active semiconductor layer made of an organic semiconductor material so as to connect the source electrode and the drain electrode, and under atmospheric pressure on the active semiconductor layer. Forming a second insulating film by plasma processing in the step (a). The manufacturing method of an organic semiconductor device.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The configuration of the element of the present invention is arranged, for example, as shown in FIG. That is, it is composed of a gate electrode G, a gate insulating film I, an active semiconductor layer P (organic semiconductor layer) made of an organic semiconductor material, a source electrode S, and a drain electrode D.
In FIG. 1A, a gate electrode, a first insulating film (gate insulating film), and a channel formed by an active semiconductor layer (organic semiconductor layer) made of an organic semiconductor material are arranged in this order on a support. Further, the organic semiconductor layer is covered with a second insulating film. That is, the active semiconductor layer (organic semiconductor layer) serving as a channel on the support is disposed above the gate electrode. The organic semiconductor layer is disposed so as to extend over the source electrode and the drain electrode which are disposed at a predetermined interval on the first insulating film, and forms a channel between the source electrode and the drain electrode.
[0010]
FIG. 1B shows a first insulating film, a channel formed by an active semiconductor layer (organic semiconductor layer) made of an organic semiconductor material, a second insulating film (gate insulating film), and a gate electrode arranged in this order on a support. This is an example in which a gate electrode is disposed above an active semiconductor layer (organic semiconductor layer) serving as a channel on a support.
[0011]
Note that a bonding film may be formed between the source electrode and the drain electrode and the organic semiconductor material. Examples of such a film include a Cr thin film, an Au thin film, a Pt thin film, and a conductive polymer thin film.
In the organic semiconductor device of the present invention, the first and second insulating films are insulating films formed by an atmospheric pressure plasma method, and an active semiconductor layer (organic semiconductor layer) made of an organic semiconductor material is formed by the insulating film thus formed. It is arranged to be sandwiched.
Hereinafter, the configuration, material, and process of each member will be described.
[0012]
<Active semiconductor layer made of organic semiconductor material (organic semiconductor layer)>
As the organic semiconductor material for forming the active semiconductor layer serving as the channel of the present invention, a π-conjugated polymer compound is preferable. For example, polypyrroles such as polypyrrole, poly (N-substituted pyrrole), poly (3-substituted pyrrole), poly (3,4-disubstituted pyrrole), polythiophene, poly (3-substituted thiophene), poly (3,4- Poly (diphenylthiophene), polythiophenes such as polybenzothiophene, polyisothianaphthenes such as polyisothianaphthene, polyphenylenevinylenes such as polyphenylenevinylene, poly (p-phenylenevinylene) such as poly (p-phenylenevinylene) Phenylene vinylenes), polyaniline, poly (N-substituted aniline), poly (3-substituted aniline), polyaniline such as poly (2,3-substituted aniline), polyacetylene such as polyacetylene, polydiacetylene such as polydiacetylene , Polyazulene such as polyazulene, polypyrene etc. Polypyrenes, polycarbazoles, polycarbazoles such as poly (N-substituted carbazole), polyselenophenes such as polyselenophene, polyfurans such as polyfuran and polybenzofuran, and poly (p-) such as poly (p-phenylene) Phenylenes), polyindoles such as polyindole, polypyridazines such as polypyridazine, naphthacene, pentacene, hexacene, heptacene, dibenzopentacene, tetrabenzopentacene, pyrene, dibenzopyrene, chrysene, perylene, coronene, terylene, ovalene, Polyacenes such as quaterylene and circum anthracene; and derivatives in which a part of carbon of the polyacenes is substituted with a functional group such as an atom such as N, S or O, or a carbonyl group (triphenodioxazine, triphenodithiazine Hexacene-6,15-quinone, etc.), polyvinylcarbazole, polyphenylene sulfide, or the like can be used polycyclic condensate described in polyvinylene sulfide polymer and JP-like de 11-195790. Further, for example, thiophene hexamer α-sexithiophene α, ω-dihexyl-α-sexithiophene, α, ω-dihexyl-α-quinquethiophene, α, ω-bis ( Oligomers such as 3-butoxypropyl) -α-sexithiophene and styrylbenzene derivatives can also be suitably used. Further, metal phthalocyanines such as copper phthalocyanine and fluorine-substituted copper phthalocyanine described in JP-A-11-251601, naphthalene 1,4,5,8-tetracarboxylic diimide, N, N'-bis (4-trifluoromethylbenzyl) N, N′-bis (1H, 1H-perfluorooctyl), N, N′-bis (1H, 1H-perfluorobutyl) and N, N′- along with naphthalene 1,4,5,8-tetracarboxylic diimide Dioctylnaphthalene 1,4,5,8-tetracarboxylic diimide derivatives, naphthalene tetracarboxylic diimides such as naphthalene 2,3,6,7 tetracarboxylic diimide, and anthracene 2,3,6,7-tetracarboxylic acid Condensed ring tetracarboxylic acids such as anthracenetetracarboxylic diimides such as diimide Examples include diimides, fullerenes such as C60, C70, C76, C78, and C84, carbon nanotubes such as SWNT, and dyes such as merocyanine dyes and hemicyanine dyes.
[0013]
Among these π-conjugated materials, thiophene, vinylene, chenylene vinylene, phenylene vinylene, p-phenylene, a substituted product thereof, or two or more of these are used as a repeating unit, and the number n of the repeating unit is 4 to 4. At least one selected from the group consisting of oligomers having 10 or a polymer in which the number n of the repeating units is 20 or more, condensed polycyclic aromatic compounds such as pentacene, fullerenes, condensed ring tetracarboxylic diimides, and metal phthalocyanines Species are preferred.
[0014]
Other organic semiconductor materials include tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTF-iodine complex, and TCNQ-iodine complex. , Etc. can also be used. Further, σ-conjugated polymers such as polysilane and polygermane, and organic / inorganic hybrid materials described in JP-A-2000-260999 can also be used.
[0015]
In the present invention, for example, a material having a functional group such as acrylic acid, acetamido, dimethylamino group, cyano group, carboxyl group, or nitro group in the active semiconductor layer, a benzoquinone derivative, tetracyanoethylene, and tetracyanoquinodimethane And materials that have an electron acceptor such as derivatives thereof and materials having functional groups such as amino group, triphenyl group, alkyl group, hydroxyl group, alkoxy group and phenyl group, and substituted amines such as phenylenediamine , Anthracene, benzoanthracene, substituted benzoanthracenes, pyrene, substituted pyrene, carbazole and its derivatives, tetrathiafulvalene and its derivatives, etc. Process Good.
[0016]
The doping means that an electron donating molecule (acsector) or an electron donating molecule (donor) is introduced as a dopant into the thin film. Therefore, the doped thin film is a thin film containing the condensed polycyclic aromatic compound and the dopant. Either an acceptor or a donor can be used as the dopant used in the present invention. As the acceptor, halogens such as Cl2, Br2, I2, ICl, ICl3, IBr, IF, Lewis acids such as PF5, AsF5, SbF5, BF3, BC13, BBr3, SO3, HF, HC1, HNO3, H2S-O4, HClO4, Protic acids such as FSO3H, ClSO3H, CF3SO3H, and organic acids such as acetic acid, formic acid, and amino acids; FeCl3, FeOCl, TiCl4, ZrCl4, HfCl4, NbF5, NbCl5, TaCl5, MoCl5, WF5, WCl6, UF6, LnCl3 (Ln = La, Lanthanoids such as Ce, Nd, Pr, etc. and transition metal compounds such as Y), electrolyte anions such as Cl-, Br-, I-, ClO4-, PF6-, AsF5-, SbF6-, BF4-, sulfonate anions, etc. Can be mentioned. Examples of the donor include alkali metals such as Li, Na, K, Rb, and Cs; alkaline earth metals such as Ca, Sr, and Ba; Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy. , Ho, Er, Yb, and other rare earth metals, ammonium ions, R4P +, R4As +, R3S +, acetylcholine, and the like. As a method of doping these dopants, any of a method of preparing a thin film of an organic semiconductor in advance and introducing the dopant later, and a method of introducing a dopant at the time of forming the thin film of the organic semiconductor can be used. As the doping of the former method, gas-phase doping using a gas-state dopant, liquid-phase doping in which a solution or liquid dopant is brought into contact with the thin film, and diffusion doping by bringing a solid-state dopant into contact with the thin film Solid doping method. In liquid phase doping, the efficiency of doping can be adjusted by performing electrolysis. In the latter method, a mixed solution or dispersion of an organic semiconductor compound and a dopant may be simultaneously applied and dried. For example, when a vacuum evaporation method is used, the dopant can be introduced by co-evaporating the dopant together with the organic semiconductor compound. When a thin film is formed by a sputtering method, a dopant can be introduced into the thin film by sputtering using a binary target of an organic semiconductor compound and a dopant. Still other methods include chemical doping such as electrochemical doping and photo-initiated doping and physical doping such as ion implantation as described in the publication {Industrial Materials, Vol. 34, No. 4, page 55, 1986}. Any of the conventional dopings can be used.
[0017]
These organic thin films can be prepared by vacuum deposition, molecular beam epitaxy, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, plasma polymerization, electrolytic polymerization, chemical polymerization, etc. Examples include a synthesizing method, a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, a roll coating method, a bar coating method, a die coating method, and an LB method, which can be used depending on the material. However, in terms of productivity, spin coating, blade coating, dip coating, roll coating, bar coating, die coating, etc., which can easily and precisely form a thin film using an organic semiconductor solution, are used. Preferred. The thickness of the organic semiconductor thin film is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the thickness of the active layer made of the organic semiconductor. Although it differs depending on the semiconductor, it is generally preferably 1 μm or less, particularly preferably 10 to 300 nm.
[0018]
<Electrode (source, drain, gate electrode)>
The gate electrode, source electrode, and drain electrode are not particularly limited as long as they are conductive materials, and include platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, and rhenium. , Iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin / antimony, indium / tin oxide (ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, Sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesi A mixture of silver / aluminum, a mixture of magnesium / aluminum, a mixture of magnesium / indium, a mixture of aluminum / aluminum oxide, a mixture of lithium / aluminum and the like are used, and platinum, gold, silver, copper, aluminum, indium, ITO and carbon are particularly preferable. . Alternatively, a known conductive polymer whose conductivity has been improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, or the like is also preferably used. As the source electrode and the drain electrode, those having low electric resistance at the contact surface with the organic semiconductor layer are preferable among the above.
[0019]
As a method of forming an electrode, a method of forming an electrode using a known photolithographic method or a lift-off method on a conductive thin film formed by using a method such as evaporation or sputtering using the above as a raw material, or a metal foil such as aluminum or copper There is a method of etching using a resist by thermal transfer, ink jet or the like. In addition, a conductive polymer solution or dispersion, or a conductive fine particle dispersion may be directly patterned by ink jet, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning an ink, a conductive paste, or the like containing a conductive polymer or conductive fine particles by a printing method such as letterpress, intaglio, lithographic, or screen printing can also be used.
[0020]
Examples of the conductive fine particles include metal fine particles having a particle diameter of 1 to 50 nm, preferably 1 to 10 nm, such as platinum, gold, silver, copper, cobalt, chromium, iridium, nickel, palladium, molybdenum, and tungsten. As a method for producing such a metal fine particle dispersion, a metal ion is reduced in a liquid phase, such as a physical generation method such as a gas evaporation method, a sputtering method, a metal vapor synthesis method, a colloid method, and a coprecipitation method. Although a chemical generation method for generating metal fine particles is exemplified, preferably, the method is described in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, and JP-A-2000-239853. Colloid method, described in JP-A-2001-254185, JP-A-2001-53028, JP-A-2001-35814, JP-A-2001-35255, JP-A-2000-124157, and JP-A-2000-123634. It is a dispersion produced by a gas evaporation method. After applying these dispersions and forming them into an electrode pattern, the solvent is dried, and further heat-treated at 100 to 300 ° C., preferably 150 to 200 ° C., to thereby heat-bond the metal fine particles. Then, an electrode is formed. Note that a gate line and a source line can be formed in a manner similar to that of the above electrode.
[0021]
<First insulating film (insulating layer) and second insulating film (insulating layer)>
Although various insulating films can be used as the insulating film of the present invention, silicon oxide, silicon nitride, aluminum oxide, tantalum oxide, and titanium oxide are particularly preferable. In the present invention, in particular, the insulating film is formed by a plasma film forming process under atmospheric pressure. The plasma film forming process under the atmospheric pressure will be described below.
[0022]
A method for forming an insulating film (eg, oxide: SiO ₂ , TiO ₂ , etc./nitride: Si ₃ N _4, etc.) by plasma film formation under atmospheric pressure will be described as follows.
The plasma film forming process under the above-mentioned atmospheric pressure refers to a process of discharging under an atmospheric pressure or a pressure near the atmospheric pressure, exciting a reactive gas by plasma, and forming a thin film on a base material. JP-A-11-133205, JP-A-2000-185362, JP-A-11-61406, JP-A-2000-147209, JP-A-2000-121804 and the like (hereinafter also referred to as atmospheric pressure plasma method) ). Thereby, a highly functional thin film can be formed with high productivity.
[0023]
FIG. 4 is a diagram showing an apparatus for performing a plasma film forming process. 4, a plasma discharge processing container 31, a gas generator 51, a power supply 41, an electrode cooling unit 60, and the like are arranged as a device configuration. As a coolant for the electrode cooling unit 60, an insulating material such as distilled water or oil is used.
The roll electrode 25 and the fixed electrode 36 are arranged at predetermined positions in the plasma discharge processing container 31, and the flow rate of the mixed gas generated by the gas generator 51 is controlled. Then, the inside of the plasma discharge processing container 31 is filled with a mixed gas used for plasma processing and exhausted from an exhaust port 53. Next, a voltage is applied to the electrode 36 by the power supply 41, the roll electrode 25 is grounded to ground, and discharge plasma is generated. Here, the base material F is supplied from the roll-shaped original winding base material 61, and the base material F wound around the roll electrode 25 via the guide roller 64 is pressed by the nip rollers 65 and 66, and the plasma discharge treatment container is formed. The substrate F is transported in a state of single-sided contact (in contact with the roll electrode 25) between the electrodes in the substrate 31, and the surface of the substrate F is subjected to discharge treatment by discharge plasma during the transport. Conveyed to the process. Here, the discharge treatment is performed only on the surface of the base material F that is not in contact with the roll electrode 25.
Further, the partition plate 54 is arranged close to the nip rollers 65 and 66, and suppresses the air accompanying the substrate F from entering the plasma discharge processing container 31.
The roll electrode 25, which is an earth electrode, is formed by spraying ceramics on a conductive base material such as a metal, and coating the dielectric with a ceramic-coated dielectric which is sealed using an inorganic material. Alternatively, a combination of a conductive base material such as a metal and a lining treated dielectric material provided with an inorganic material by lining may be used. As the lining material, silicate glass, borate glass, phosphate glass, germanate glass, tellurite glass, aluminate glass, vanadate glass and the like are preferably used. Of these, borate glass is more preferably used because it is easy to process. Examples of the conductive base material such as a metal include metals such as silver, platinum, stainless steel, aluminum, and iron, and stainless steel is preferable from the viewpoint of processing. As the ceramic material used for thermal spraying, alumina and silicon nitride are preferably used. Among them, alumina is more preferably used because it is easy to process. As a base material of the roll electrode, a stainless steel jacket roll base material having cooling means with cooling water can be used (not shown).
[0024]
The power source 41 for applying a voltage to the application electrode 36 is not particularly limited, but is a high frequency power source (200 kHz) manufactured by Pearl Industries, a high frequency power source (800 kHz) manufactured by Pearl Industries, a high frequency power source manufactured by JEOL (13.56 MHz), A high frequency power supply (150 MHz) manufactured by the company can be used.
[0025]
The distance between the electrodes is determined in consideration of the thickness of the solid dielectric placed on the base material of the electrode, the magnitude of the applied voltage, the purpose of using plasma, and the like. The shortest distance between the solid dielectric and the electrode when the solid dielectric is installed on one of the electrodes, and the distance between the solid dielectrics when the solid dielectric is installed on both of the electrodes is uniform in each case. From the viewpoint of discharging, the thickness is preferably 0.5 mm to 20 mm, particularly preferably 1 mm ± 0.5 mm.
[0026]
A high-frequency voltage exceeding 100 kHz and a power of 1 W / cm 2 or more are supplied between the opposing electrodes to excite the reactive gas to generate plasma. By applying such a high-power electric field, it is possible to obtain a dense, highly functional thin film having high uniformity in film thickness with high production efficiency.
[0027]
Here, the upper limit of the frequency of the high-frequency voltage applied between the electrodes is preferably 150 MHz or less. The lower limit of the frequency of the high-frequency voltage is preferably 200 kHz or more, and more preferably 800 kHz or more.
Further, the lower limit of the power supplied between the electrodes is preferably 1.2 W / cm2 or more, and the upper limit is preferably 50 W / cm2 or less, more preferably 20 W / cm2 or less. Note that the voltage application area (/ cm 2) at the electrode indicates an area within a range in which discharge occurs.
[0028]
The value of the voltage applied to the electrode 36 fixed by the power supply 41 is appropriately determined. Regarding the power supply method, either a continuous sine wave continuous oscillation mode called a continuous mode or an intermittent oscillation mode in which ON / OFF is intermittently called a pulse mode may be adopted, but the continuous mode is more preferable. A dense and high quality film can be obtained.
[0029]
In addition, in order to minimize the influence on the substrate during the discharge plasma treatment, the temperature of the substrate during the discharge plasma treatment may be adjusted to a temperature between room temperature (15 ° C. to 25 ° C.) and less than 200 ° C. Preferably, it is more preferably adjusted to room temperature to 100 ° C. In order to adjust the temperature to the above-mentioned temperature range, the electrodes and the substrate are subjected to a discharge plasma treatment while being cooled by a cooling means, if necessary.
[0030]
The above-mentioned discharge plasma treatment is performed at or near atmospheric pressure. Here, "atmospheric pressure" means a pressure of 20 kPa to 110 kPa, and preferably 93 kPa to 104 kPa.
[0031]
In the discharge electrode according to the method for forming a thin film, the maximum height (Rmax) of the surface roughness defined by JIS B0601 on at least the side of the electrode in contact with the base material is adjusted to be 10 μm or less. However, it is more preferable that the maximum value of the surface roughness is 8 μm or less, particularly preferably 7 μm or less.
[0032]
Further, the center line average surface roughness (Ra) specified in JIS B 0601 is preferably 0.5 μm or less, more preferably 0.1 μm or less.
[0033]
The mixed gas will be described. In carrying out the method of forming a thin film, the gas used depends on the type of the thin film to be provided on the substrate, but is basically a mixed gas of an inert gas and a reactive gas for forming the thin film. The reactive gas is preferably contained at 0.01 to 10% by volume based on the mixed gas.
[0034]
Examples of the inert gas include elements belonging to Group 18 of the periodic table, specifically, helium, neon, argon, krypton, xenon, and radon. Nitrogen gas is also useful as the inert gas. .
[0035]
As the reactive gas, a reactive gas containing a silicon compound, a titanium compound, or an organic fluorine compound can be used.
[0036]
When the above-described titanium compound is used in the mixed gas, the content of the titanium compound in the mixed gas is 0.1 to 10% by volume from the viewpoint of forming a uniform thin film on the base material by the discharge plasma treatment. Preferably, it is more preferably 0.1 to 5% by volume.
Further, the hardness of the thin film can be remarkably improved by containing 0.1 to 10% by volume of oxygen gas in the above-mentioned mixed gas.
In addition, by containing a component selected from oxygen, ozone, hydrogen peroxide, carbon dioxide, carbon monoxide, hydrogen, and nitrogen in the mixed gas in an amount of 0.01 to 5% by volume, the reaction is promoted and the density is increased. A high-quality thin film can be formed.
[0037]
As the silicon compound and the titanium compound described above, a metal hydrogen compound and a metal alkoxide are preferable from the viewpoint of handling, and a metal alkoxide is preferably used because corrosiveness, no generation of harmful gas, and less contamination in the process are preferred. Can be
[0038]
In order to introduce the above-mentioned silicon compound and titanium compound between the electrodes which are discharge spaces, both may be in a gas, liquid or solid state at normal temperature and normal pressure. In the case of gas, it can be directly introduced into the discharge space, but in the case of liquid or solid, it is used after being vaporized by means such as heating, decompression, and ultrasonic irradiation.
[0039]
When a silicon compound or a titanium compound is used after being vaporized by heating, a metal alkoxide which is liquid at ordinary temperature and has a boiling point of 200 ° C. or less is preferably used. The metal alkoxide may be used after being diluted with a solvent. As the solvent, an organic solvent such as methanol, ethanol, or n-hexane, or a mixed solvent thereof can be used. Since these diluting solvents are decomposed into molecules and atoms during the plasma discharge treatment, the influence on the formation of the thin film on the base material, the composition of the thin film, and the like can be almost ignored.
[0040]
Examples of the silicon compound described above include alkylsilanes such as dimethylsilane and tetramethylsilane, alkoxysilanes such as tetramethoxysilane, tetraethoxysilane and dimethyldiethoxysilane, organometallic compounds such as organosilane, and dichloride. It is preferable to use metal halides such as silane and trichloride silane, and other metal hydrogen compounds such as monosilane and disilane, but not limited thereto. These can be used in appropriate combination.
[0041]
When the silicon compound described above is used in the mixed gas, the content of the silicon compound in the mixed gas is 0.1 to 10% by volume from the viewpoint of forming a uniform thin film on the substrate by the discharge plasma treatment. It is preferably, but more preferably, 0.1 to 5% by volume.
[0042]
Examples of the titanium compound described above include alkylsilanes such as tetradimethylaminotitanium, metal alkoxides such as tetraethoxytitanium, tetraisopropoxytitanium, and tetrabutoxytitanium; and organic metal compounds such as titanium dichloride, titanium trichloride, It is preferable to use a metal halogen compound such as titanium chloride or the like, or a metal hydrogen compound such as monotitanium or dititanium, but is not limited thereto.
[0043]
<Support>
The support is made of a polymer support such as a flexible resin sheet or glass, and a plastic film, for example, can be used as the polymer support. Examples of the plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyether imide, polyether ether ketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), Examples include a film made of cellulose triacetate (TAC), cellulose acetate propionate (CAP), and the like. These films can be subjected to known surface treatment and surface coating. As described above, by using a plastic film, the weight can be reduced as compared with the case of using a glass substrate, portability can be improved, and resistance to impact can be improved.
[0044]
<Example>
Several embodiments based on the above are described below. The details of forming the first and second insulating films by the atmospheric pressure plasma method are as follows.
[0045]
[Processing example]
《Reactive gas》
The composition of the mixed gas (reactive gas) used for the plasma treatment is described below.
(For forming SiO ₂ layer)
Inert gas: 98.25% by volume of helium
Reactive gas 1: 1.5% by volume of oxygen gas
Reactive gas 2: Tetraethoxysilane vapor (bubble with helium gas) 0.25% by volume
[0046]
《Discharge conditions》
The discharge output is 10 W / cm2.
《Electrode conditions》
The roll electrode was coated with 1 mm of alumina by ceramic spraying on a stainless steel jacket roll base material having cooling means with cooling water, and then applied and dried a solution obtained by diluting tetramethoxysilane with ethyl acetate, followed by ultraviolet irradiation. This is a roll electrode having a dielectric material (relative dielectric constant of 10) which is cured, subjected to a sealing treatment, and has a smooth surface and Rmax of 5 μm, and is grounded. On the other hand, as an application electrode, a hollow rectangular stainless steel pipe is coated with the same dielectric as described above under the same conditions.
[0047]
On the base film 8, a plasma treatment is continuously performed under the atmospheric pressure under the above-mentioned reactive gas, the above-mentioned discharge conditions, and the above-mentioned electrode conditions to form a thin film having a thickness of 100 nm.
Hereinafter, the organic thin film transistor element manufactured will be described.
[0048]
<Example A>
The organic thin film transistor device shown in FIG. 1A was produced as follows.
An aluminum film having a thickness of 300 nm and a width of 300 μm was formed on a 150 μm-thick PES film by a sputtering method to form a gate electrode. On this gate electrode, a 200-nm-thick silicon oxide film was formed by the atmospheric pressure plasma method under the above-mentioned conditions, and used as a gate insulating film (first insulating film). A chloroform solution of a regioregular body of poly (3-hexylthiophene) (manufactured by Aldrich), which was well purified so that the contents of Zn and Ni became 10 ppm or less, was prepared on the surface of the gate insulating film in an N2 gas atmosphere. After applying using an applicator and drying at room temperature, a heat treatment was performed at 50 ° C. for 30 minutes in an N 2 gas atmosphere. At this time, the film thickness of poly (3-hexylthiophene) was 30 nm. Further, gold was deposited on the surface of the poly (3-hexylthiophene) film using a mask to form source and drain electrodes. Source and drain electrodes having a width of 100 μm and a thickness of 100 nm are arranged so as to be orthogonal to the gate electrode, and have a channel width W = 0.3 mm (length of a portion where the source electrode faces the drain electrode) and a channel length L = An organic thin film transistor having a thickness of 20 μm (the distance between the source and drain electrodes) was formed.
Further, a silicon oxide film (second insulating film) having a thickness of 300 nm was formed on the organic thin film transistor by the above-mentioned atmospheric pressure plasma method.
[0049]
<Example B>
An organic thin film transistor was prepared and evaluated in the same manner as in Example A, except that a titanium oxide thin film formed by an atmospheric pressure plasma method was used as the second insulating film.
[0050]
<Example C>
The organic thin-film transistor device shown in FIG. 1B was prepared as follows.
A 200-nm-thick silicon oxide film was formed as a first insulating film on a 150 μm-thick PES film by the atmospheric pressure plasma method under the above-described conditions. Gold was deposited on this insulating film using a mask to form source and drain electrodes. The channel length L was 20 μm, and the channel width W was 0.3 mm. Further, a purified chloroform solution of regioregular-poly (3-hexylthiophene) was discharged using a piezo-type inkjet, and the solution was filled between the source and drain electrodes. After drying chloroform as a solvent, it is heat-treated in a nitrogen gas atmosphere at 50 ° C. for 30 minutes and left in a vacuum for 24 hours, so that an active semiconductor layer (organic semiconductor layer) made of an organic semiconductor material is formed between the source and drain electrodes. Was formed. Thus, the thickness of the poly (3-hexylthiophene) film provided as the organic semiconductor layer was about 30 nm. A silicon oxide film having a thickness of 200 nm was formed as a second insulating film by the above-described atmospheric pressure plasma method so as to cover the organic semiconductor layer, the source electrode, and the drain electrode. Thereafter, a gate electrode having a width of 30 μm was further formed by a photolithography method on the organic semiconductor layer with the second insulating film interposed therebetween, whereby the transistor element shown in FIG. 1B was formed.
[0051]
<Comparative Example 1> (without insulating film)
An organic thin film transistor was fabricated in the same manner as in Example A except that the second insulating film was not formed.
[0052]
<Comparative Example 2> (An insulating film was formed by vapor deposition)
An organic thin-film transistor was fabricated in the same manner as in Example A, except that the second insulating film was formed by heat evaporation.
[0053]
<Comparative Example 3> (formed by applying and curing an insulating film)
An element was fabricated in the same manner as in Example A except that the silicon oxide film as the second insulating film of Example A was formed by coating and curing. When the insulating film is formed by coating and curing, specifically, at least one selected from a metal alkoxide and a hydrolyzate thereof, and a composition containing an organic solvent are applied on a transparent substrate, and an active energy ray is applied. For example, curing is performed by applying energy such as heat rays or ultraviolet rays.
Here, the composition obtained by the following preparation was applied on a support so as to have a dry film thickness of 3.5 μm, and dried at 80 ° C. for 5 minutes. Next, it is cured by irradiating it with 400 mJ / cm 2 of ultraviolet rays using a high-pressure mercury lamp (80 W). The composition was adjusted as follows.
[0054]
[Preparation of composition]
-6 parts by weight of SiO2 sol (Snowtex (IPA-ST, manufactured by Nissan Chemical Industries, Ltd.))-1 part by weight of trimethylolpropane triglycidyl ether (active energy ray reactive compound)-γ-glycidopropyltrimethoxysilane 0 0.3 parts by weight, 4,3'-bis (di (β-hydroxyethoxy) phenylsulfonio) phenylsulfide-bis-hexafluoroantimonate (UV initiator) 0.03 part by weight, cyclohexanone 600 parts by weight silicon oil (SH200, manufactured by Dow Corning Toray Silicone Co., Ltd.) 0.05 parts by weight
<Comparative Example 4> (no insulating film)
An element was prepared in the same manner as in Example C except that the first insulating film of Example C was not formed.
[0056]
(Comparison result)
The transistor characteristics of the above example and the comparative example were measured at atmospheric pressure by the transistor characteristic evaluation system shown in FIG. 3 (FIG. 3 schematically shows the connection between the source, drain, gate electrodes and the measurement unit. , Does not show the detailed structure of the element).
・ Drain current (leak current): I
The drain current was measured when the gate bias was 30 V and the bias between the source and the drain was -50 V.
・ ON / OFF ratio: R
The drain current was measured when the gate bias was -100 V and the bias between the source and drain was -50 V, and the ratio (ON / OFF ratio) to the current value of (1) was obtained.
-After leaving the prepared organic thin film transistor in the air at room temperature for one month, the above drain current and ON / OFF ratio were obtained. Let them be In and Rn, respectively.
[0057]
The evaluation results were as follows.

[0058]
In Examples A and B, the organic semiconductor layer was sandwiched between two insulating films (first and second insulating films) formed by the atmospheric pressure plasma method, so that the insulating film was compared with Comparative Example 1 in which one of the insulating films was not provided. As a result, it can be seen that the drain current (leakage current) has been reduced and the ON / OFF ratio has been greatly improved as a switching operation. In particular, when compared with Comparative Examples 2 and 3 in which the method of forming the insulating film is different, it can be seen that the atmospheric pressure plasma method greatly contributes to the drain current (leakage current) and the performance in the ON / OFF ratio as the method of forming the insulating film. .
It can be seen from a comparison with Comparative Example 4 that such an effect is similarly observed in Example C (where the gate electrode is disposed above the organic semiconductor layer) in which the arrangement of the elements is changed.
That is, an active semiconductor layer formed of an organic semiconductor material is very good because of a combination with two insulating films (first and second insulating films) formed by an atmospheric pressure plasma method and an arrangement sandwiching the active semiconductor layer. It has been found that it exhibits excellent characteristics.
Also, from the comparison of I, R, In, and Rn in each of the examples and the comparative example, the organic semiconductor layer is formed of two insulating films (first and second insulating films) formed by the atmospheric pressure plasma method as in the present invention. By being sandwiched, the performance could be maintained at a high level for a long time.
[0059]
【The invention's effect】
From the above, according to the present invention, when an organic semiconductor material is used as an active semiconductor layer in a thin film TFT, characteristics and stability such as an on / off ratio and a leak current of a device are improved. An excellent effect of a thin film transistor can be obtained by combining an insulating film and an organic semiconductor material. Further, film formation can be performed under an atmospheric pressure environment, and a vacuum process is not required, so that manufacturing cost can be reduced and a manufacturing process can be simplified.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of an organic semiconductor device of the present invention.
FIG. 2 is a view showing a state in which a TFT element using a conventional Si semiconductor is formed on a display panel substrate.
FIG. 3 is a view showing an evaluation system of the device of the present invention.
FIG. 4 is a view showing an apparatus for performing an atmospheric pressure plasma film forming process in the present invention.
[Explanation of symbols]
25: Roll electrode 31: Plasma generation processing vessel 36: Electrode 41: Power supply 51: Gas generator

Claims (22)

A source electrode, a drain electrode, an active semiconductor layer made of an organic semiconductor material connecting the source electrode and the drain electrode, and an organic semiconductor element having a gate electrode,
An organic semiconductor device, wherein the active layer is disposed so as to be sandwiched between insulating films formed by plasma processing under atmospheric pressure.  2. The organic semiconductor device according to claim 1, wherein the insulating film is made of an oxide or a nitride.  3. The organic semiconductor device according to claim 2, wherein the insulating film is made of any one of silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide.  3. The organic semiconductor device according to claim 2, wherein the insulating film is made of silicon nitride.  5. The organic semiconductor device according to claim 1, wherein the organic semiconductor material forming the active semiconductor layer is a π-conjugated polymer compound.  6. The organic semiconductor device according to claim 1, wherein the support is a resin sheet.  The organic semiconductor device according to claim 6, wherein the support is a plastic film.  The organic semiconductor device according to any one of claims 1 to 5, wherein the support is a polymer support.  9. The organic semiconductor device according to claim 1, wherein the active semiconductor layer, the insulating film, and the gate electrode are arranged on the support in this order.  10. The organic semiconductor device according to claim 1, wherein the gate electrode, the insulating film, and the active semiconductor layer are arranged on the support in this order. 11. The organic semiconductor device according to claim 1, wherein the organic semiconductor device is a transistor. A method for manufacturing an organic semiconductor element,
Forming a first insulating film by plasma treatment under atmospheric pressure;
Arranging a source electrode and a drain electrode as a channel on the first insulating film;
Disposing an active semiconductor layer made of an organic semiconductor material so as to connect the source electrode and the drain electrode, and forming a second insulating film on the active semiconductor layer by plasma treatment under atmospheric pressure. A method for manufacturing an organic semiconductor device, comprising:  13. The method for manufacturing an organic semiconductor device according to claim 12, wherein the first and second insulating films are formed by plasma-exciting a reactive gas at or near atmospheric pressure.  14. The method according to claim 12, wherein the first insulating film is formed after disposing a gate electrode on a support.  14. The method for manufacturing an organic semiconductor device according to claim 12, wherein a gate electrode is disposed after forming the second insulating film.  16. The method according to claim 12, wherein the insulating film is made of an oxide or a nitride.  17. The method according to claim 16, wherein the insulating film is made of any one of silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide.  17. The method according to claim 16, wherein the insulating film is made of silicon nitride.  19. The method according to claim 12, wherein the organic semiconductor material is a π-conjugated polymer compound.  20. The method according to claim 12, wherein the support is a resin sheet.  21. The method according to claim 20, wherein the support is a plastic film.  20. The method according to claim 12, wherein the support is a polymer support.

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