JP2009026852A - Oxide semiconductor thin film and thin film transistor, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel oxide semiconductor thin film, an oxide semiconductor thin film which is improved in variance in off current etc., makes a TFT element stable, and is improved in production efficiency by a method thereof, and a thin film transistor. <P>SOLUTION: The oxide semiconductor thin film is obtained by oxidizing a thin film after forming the thin film containing a dispersion product of metal particulates. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oxide semiconductor thin film obtained by providing a thin film containing metal fine particles and oxidizing the thin film, and a method for manufacturing the same, and relates to a thin film transistor using the oxide semiconductor.

  A thin film of amorphous silicon or the like is formed on a glass substrate, and the active matrix circuit of a field effect thin film transistor (TFT) that uses this as an active layer is used in place of a glass substrate to make it thinner and lighter. Attempts have also been made to use a flexible resin substrate.

  Since a transistor using a silicon thin film requires a relatively high temperature thermal process, it is difficult to form a transistor directly on a resin substrate having low heat resistance. In addition, development of oxide semiconductor thin films that can be manufactured at low temperatures with an inexpensive substrate has been actively conducted.

  For example, an attempt has been made to convert a metal film made of Cu, Zn, Al or the like formed on a substrate into a metal oxide semiconductor film by oxidation by thermal oxidation or plasma oxidation (for example, Patent Document 1).

  A field effect transistor using an active layer containing an amorphous oxide formed by vapor deposition, sputtering, or the like is also known (for example, Patent Document 2).

However, any of these methods uses a vapor deposition method, a pulse laser deposition method, a sputtering method, or the like for forming a thin film, and the production efficiency is low. The method by oxidation of the metal film has a problem that the efficiency of the oxidation reaction is low and the off current of the formed TFT is increased. In addition, the production of amorphous oxide by sputtering or pulse laser deposition also has a problem that it is difficult to control the composition ratio of oxygen, and performance variations tend to occur.
JP-A-8-264794 JP 2006-165527 A

  An object of the present invention is to provide an oxide semiconductor thin film and a thin film transistor with improved production efficiency that improve the variation of off current and the like and stabilize the TFT element by a new metal oxide semiconductor and its manufacturing method.

  The above object of the present invention is achieved by the following means.

  1. An oxide semiconductor thin film obtained by providing a thin film containing a dispersion of metal fine particles and then oxidizing the thin film.

  2. 2. The oxide semiconductor thin film according to 1 above, wherein the metal fine particles have an average particle diameter of 1 to 300 nm.

  3. 3. The oxide semiconductor thin film according to 1 or 2 above, wherein the metal fine particles contain any of In, Zn, and Sn.

  4). 4. The oxide semiconductor thin film according to any one of 1 to 3, wherein the metal fine particles contain one of Ga and Al.

  5). 4. The oxide semiconductor thin film according to any one of 1 to 3, wherein the oxidation is plasma oxidation.

  6). 5. The oxide semiconductor thin film as described in 4 above, wherein the substrate temperature during oxidation is 50 ° C. to 250 ° C.

  7. 4. The oxide semiconductor thin film according to any one of 1 to 3, wherein the oxidation is thermal oxidation.

  8). 8. The oxide semiconductor thin film according to any one of 1 to 7 above, wherein a thin film containing a dispersion of metal fine particles is provided, and then the thin film formed by fusing metal fine particles is oxidized.

  9. 9. A thin film transistor using the oxide semiconductor thin film according to any one of 1 to 8 as an active layer.

  10. A method for producing an oxide semiconductor thin film, comprising: providing a thin film containing a dispersion of metal fine particles; and oxidizing the thin film.

  With the oxide semiconductor thin film according to the present invention, a TFT element with little variation in off current or the like and stable performance and improved production efficiency can be obtained.

  The best mode for carrying out the present invention will be described below, but the present invention is not limited thereto.

  In the present invention, a thin film of a metal oxide semiconductor is obtained by providing a thin film containing a dispersion of metal fine particles and then oxidizing the thin film.

  As the material of the metal fine particles, silver, nickel, chromium, copper, iron, tin, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, zinc, gallium, or the like can be used. .

  Among these, it is preferable that any one of indium, zinc, and tin is included, and it is preferable that gallium is further included.

  It is preferable to form an electrode using a dispersion in which fine particles made of these metals are dispersed in water or a dispersion medium that is an arbitrary organic solvent using a dispersion stabilizer mainly made of an organic material.

  As a method for producing such a dispersion of metal fine particles, metal ions are reduced in a liquid phase, such as a physical generation method such as gas evaporation method, sputtering method, and metal vapor synthesis method, colloid method, and coprecipitation method. Examples of the chemical production method for producing metal fine particles include those described in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, JP-A-2000-239853, and the like. The colloid method described in Japanese Patent Application Laid-Open No. 2001-254185, 2001-53028, 2001-35255, 2000-124157, 2000-123634, Japanese Patent No. 2561537, etc. It is a dispersion of fine metal particles produced by a gas evaporation method.

  The average particle diameter of the metal fine particles is preferably 1 to 300 nm, and can promote the fusion described later and facilitate the conversion to an amorphous oxide semiconductor when an oxidation treatment is performed.

(Composition ratio of metal)
The metal preferably contains any one of In, Zn, and Sn, and further preferably contains Ga or Al. However, when the metal contains In, the composition ratio of the metal when In is set to 1, Zn _y Sn _1-y (where y is a positive number from 0 to ₁ ) is preferably from 0.2 to 5, more preferably from 0.5 to 2. Moreover, when In is set to 1, the composition ratio of Ga and Al is preferably 0 to 5, more preferably 0.5 to 2, respectively.

(Film formation method, patterning method)
As a method for forming a thin film containing metal fine particles, 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, etc. And a method of patterning by a printing method such as relief printing, intaglio printing, planographic printing, screen printing, and ink jet. The coating film may be patterned by photolithography, laser ablation, or the like. Conventionally known methods can be applied to the formation and patterning of a thin film containing metal fine particles.

  In addition, a dispersion of metal fine particles is dropped by, for example, ink jet and the dispersion medium is volatilized to form a thin film. Further, by heating the thin film made of the metal fine particles, the fine particles can be fused to obtain a metal thin film.

  The thickness of the formed metal thin film is 1 to 200 nm, more preferably 5 to 100 nm.

  Moreover, the metal thin film formed from the metal fine particles can be subjected to heat treatment before the oxidation step. The metal fine particles may be fused together by heat treatment. The degree of fusion can be arbitrarily adjusted, and the thin film can be oxidized from any fusion state.

  FIG. 1 schematically shows a process in which fusion of a thin film containing metal fine particles proceeds by heating, but the presence / absence and degree of fusion can be arbitrarily adjusted, and FIG. 1 (A), (B) , (C) can be oxidized from any state.

  In the case of metal fine particles having a particle size of 300 nm or less, the fusing temperature can be performed at a low temperature of 400 ° C. or less.

  From the viewpoint of dispersion stability, the metal fine particles are preferably dispersed in a dispersion medium using a dispersant, but the thin film containing the metal fine particles is formed, before the fusion, and before the oxidation step. For example, it is preferable to perform cleaning by a dry cleaning process such as oxygen plasma and UV ozone cleaning, and decompose and clean organic substances contained in the thin film such as a dispersant to exclude organic substances other than metal components (FIG. 2). .

(Thin film oxidation process)
Examples of a method for oxidizing a metal thin film formed from metal fine particles into an oxide semiconductor include an oxygen plasma method, a thermal oxidation method, a UV ozone method, and the like. As the oxygen plasma method, an atmospheric pressure plasma method is preferable. In the oxygen plasma method and the UV ozone method, the substrate is preferably heated in the range of 50 ° C. to 400 ° C., preferably 100 ° C. to 250 ° C.

  In the atmospheric pressure plasma method, an inert gas such as argon gas is used as a discharge gas under atmospheric pressure, and a reaction gas (a gas containing oxygen) is introduced into the discharge space, and a high frequency electric field is applied to the discharge gas. Is excited to generate plasma, and contact with a reactive gas to generate plasma containing oxygen, and the substrate surface is exposed to this to perform oxygen plasma treatment. Under atmospheric pressure represents a pressure of 20 to 110 kPa, preferably 93 to 104 kPa.

  Using the atmospheric pressure plasma method, oxygen plasma is generated as a reactive gas, oxygen plasma is generated, and the metal thin film formed from the metal fine particles is exposed to the plasma space. It undergoes plasma oxidation to form a metal oxide in the surface layer.

The high frequency power supply is 0.5 kHz or more and 2.45 GHz or less, and the power supplied between the counter electrodes is preferably 0.1 W / cm ² or more and 50 W / cm ² or less.

  The gas used varies depending on the type of thin film to be provided on the substrate, but is basically a mixed gas of a discharge gas (inert gas) and a reactive gas. The reaction gas (oxygen gas) is preferably contained in an amount of 0.01 to 10% by volume with respect to the mixed gas. Although it is more preferable that it is 0.1-10 volume%, More preferably, it is 0.1-5 volume%.

  Examples of the inert gas include Group 18 elements of the periodic table, specifically, helium, neon, argon, krypton, xenon, radon, nitrogen gas, and the like, in order to obtain the effects described in the present invention. For this, helium, argon, or nitrogen gas is preferably used.

  In order to introduce the reaction gas between the electrodes which are the discharge space, normal temperature and normal pressure may be used.

  The plasma method under atmospheric pressure is described in JP-A-11-61406, JP-A-11-133205, JP-A-2000-121804, JP-A-2000-147209, JP-A-2000-185362.

  By such treatment, an amorphous oxide semiconductor thin film can be formed.

  The UV ozone method is a method of irradiating ultraviolet light in the presence of oxygen to advance an oxidation reaction. It is preferable to irradiate so-called vacuum ultraviolet light having a wavelength of ultraviolet light of 100 nm to 450 nm, particularly preferably about 150 to 300 nm. As the light source, a low-pressure mercury lamp, a deuterium lamp, a xenon excimer lamp, a metal halide lamp, an excimer laser, or the like can be used.

(Amorphous oxide)
It is only necessary that the carrier electron density of the amorphous oxide, which is the metal oxide according to the present invention, is less than 10 ¹⁸ / cm ³ . The electron carrier concentration is a value when measured at room temperature. The room temperature is, for example, 25 ° C., specifically, a certain temperature appropriately selected from the range of about 0 ° C. to 40 ° C. Note that the electron carrier concentration of the amorphous oxide according to the present invention does not have to satisfy less than 10 ¹⁸ / cm ³ in the whole range of 0 ° C. to 40 ° C. For example, a carrier electron density of less than 10 ¹⁸ / cm ³ may be realized at 25 ° C. Further, when the electron carrier concentration is further reduced to 10 ¹⁷ / cm ³ or less, more preferably 10 ¹⁶ / cm ³ or less, a normally-off TFT can be obtained with a high yield.

  The electron carrier concentration can be measured by Hall effect measurement.

  The film thickness of the semiconductor that is a metal oxide is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the film thickness of the semiconductor film, and the film thickness varies depending on the semiconductor. Generally, 1 μm or less, particularly 10 to 300 nm is preferable.

In the present invention, the material, composition ratio, production conditions, and the like are controlled so that, for example, the electron carrier concentration is 10 ¹² / cm ³ or more and less than 10 ¹⁸ / cm ³ . More preferably, it is in the range of 10 ¹³ / cm ³ or more and 10 ¹⁷ / cm ³ or less, and more preferably 10 ¹⁵ / cm ³ or more and 10 ¹⁶ / cm ³ or less.

  FIG. 2 schematically shows a process of forming an oxide semiconductor thin film by dry cleaning a thin film containing metal fine particles and fusing it by heating, followed by a thin film oxidation process.

  The oxide semiconductor thin film according to the present invention can be used for a field effect thin film transistor (TFT).

(electrode)
In the present invention, the conductive material used for the electrodes (source electrode, drain electrode, gate electrode) constituting the TFT element is not particularly limited as long as the electrode has conductivity at a practical level. Platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin / antimony oxide, indium oxide -Tin (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, Nat Um, sodium - potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, a lithium / aluminum mixture, or the like is used.

  Moreover, as a conductive material, a conductive polymer, metal fine particles, or the like can be suitably used. As the dispersion containing metal fine particles, for example, a known conductive paste may be used, but a dispersion containing metal fine particles having a particle diameter of 1 nm to 50 nm, preferably 1 nm to 10 nm is preferable. In order to form an electrode from metal fine particles, the above-described method can be used in the same manner, and the metal described above can be used as the material of the metal fine particles.

(Method for forming electrodes, etc.)
As a method for forming an electrode, a method for forming an electrode using a known photolithographic method or a lift-off method from a conductive thin film formed by using a method such as vapor deposition or sputtering using the above as a raw material, or a metal foil such as aluminum or copper There is a method in which a resist is formed and etched by thermal transfer, ink jet or the like. Alternatively, a conductive polymer solution or dispersion, a dispersion containing metal fine particles, or the like may be directly patterned by an ink jet method, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning a conductive ink or conductive paste containing a conductive polymer or metal fine particles by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used.

  As a method for forming an electrode such as a source, drain, or gate electrode, a gate, or a source bus line without patterning a metal thin film using a photosensitive resin such as etching or lift-off, a method by an electroless plating method is used. Are known.

  Regarding the method of forming an electrode by electroless plating, as described in Japanese Patent Application Laid-Open No. 2004-158805, a liquid containing a plating catalyst that causes electroless plating by acting with a plating agent is applied to a portion where the electrode is provided. For example, after patterning by a printing method (including inkjet printing), a plating agent is brought into contact with a portion where an electrode is provided. If it does so, electroless plating will be performed to the said part by the contact of the said catalyst and a plating agent, and an electrode pattern will be formed.

  The application of the electroless plating catalyst and the plating agent may be reversed, and the pattern formation may be performed either. However, a method of forming a plating catalyst pattern and applying the plating agent to this is preferable.

  As the printing method, for example, screen printing, planographic printing, letterpress printing, intaglio printing, printing by ink jet printing, or the like is used.

(Element structure)
FIG. 3 is a diagram showing a typical element configuration of a thin film transistor element using an oxide semiconductor thin film according to the present invention.

  FIGS. 2A to 2F are cross-sectional views showing examples of the structure of a thin film transistor using a semiconductor thin film manufactured by the method for manufacturing an oxide semiconductor thin film according to the present invention. In FIG. 2, the semiconductor thin film is preferably configured such that a source electrode and a drain electrode are connected as a channel.

  In FIG. 5A, a source electrode 2 and a drain electrode 3 are formed on a support 6 with a metal foil or the like, and this is used as a base material (substrate). A field effect thin film transistor is formed by forming a semiconductor layer 1 made of a physical semiconductor thin film, forming an insulating layer 5 thereon, and further forming a gate electrode 4 thereon. FIG. 2B shows the semiconductor layer 1 formed between the electrodes in FIG. 1A so as to cover the entire surface of the electrode and the support using a coating method or the like. (C) shows that the semiconductor layer 1 is first formed on the support 6 using the method of the present invention, and then the source electrode 2, the drain electrode 3, the insulating layer 5, and the gate electrode 4 are formed.

  In FIG. 4D, after forming the gate electrode 4 on the support 6 with a metal foil or the like, the insulating layer 5 is formed, and the source electrode 2 and the drain electrode 3 are formed on the metal foil or the like on the insulating layer 5. A semiconductor layer 1 formed of the oxide semiconductor thin film of the present invention is formed between the electrodes. In addition, the configuration as shown in FIGS.

  FIG. 4 is a schematic equivalent circuit diagram of an example of a thin film transistor sheet 20 in which a plurality of thin film transistor elements according to the present invention are arranged.

  The thin film transistor sheet 20 has a large number of thin film transistor elements 24 arranged in a matrix. Reference numeral 21 denotes a gate bus line of the gate electrode of each thin film transistor element 24, and reference numeral 22 denotes a source bus line of the source electrode of each thin film transistor element 24. An output element 26 is connected to the drain electrode of each thin film transistor element 24. The output element 26 is, for example, a liquid crystal or an electrophoretic element, and constitutes a pixel in the display device. In the illustrated example, a liquid crystal is shown as an output element 26 by an equivalent circuit composed of a resistor and a capacitor. Reference numeral 25 denotes a storage capacitor, 27 denotes a vertical drive circuit, and 28 denotes a horizontal drive circuit.

  The present invention can be used to manufacture such a thin film transistor sheet in which TFT elements are two-dimensionally arranged on a support.

(Gate insulation film)
Although various insulating films can be used as the gate insulating film of the thin film transistor according to the present invention, an inorganic oxide film having a high relative dielectric constant is particularly preferable. Inorganic oxides include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, strontium titanate, Examples thereof include barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. Of these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide are preferable. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

  Examples of the method for forming the film include a vacuum process, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method, an ion plating method, a CVD method, a sputtering method, an atmospheric pressure plasma method, and a spray process. Examples include wet processes such as coating methods, spin coating methods, blade coating methods, dip coating methods, casting methods, roll coating methods, bar coating methods, die coating methods, and other methods such as printing and ink jet patterning. Can be used depending on the material.

  The wet process is a method of applying and drying a liquid in which fine particles of inorganic oxide are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as required, or an oxide precursor, for example, A so-called sol-gel method in which a solution of an alkoxide body is applied and dried is used.

  Of these, the atmospheric pressure plasma method is preferred.

  It is also preferable that the gate insulating film (layer) is composed of an anodized film or the anodized film and an insulating film. The anodized film is preferably sealed. The anodized film is formed by anodizing a metal that can be anodized by a known method.

  Examples of the metal that can be anodized include aluminum and tantalum, and the anodizing method is not particularly limited, and a known method can be used.

  Examples of organic compound films include polyimides, polyamides, polyesters, polyacrylates, photo-radical polymerization-type, photo-cation polymerization-type photo-curing resins, copolymers containing acrylonitrile components, polyvinyl phenol, polyvinyl alcohol, novolac resins, etc. Can also be used.

  An inorganic oxide film and an organic oxide film can be laminated and used together. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

(substrate)
Various materials can be used as the support material constituting the substrate. For example, ceramic substrates such as glass, quartz, aluminum oxide, sapphire, silicon nitride, silicon carbide, silicon, germanium, gallium arsenide, gallium phosphide. In addition, a semiconductor substrate such as gallium nitrogen, paper, and non-woven fabric can be used. In the present invention, the support is preferably made of a resin, for example, a plastic film sheet can be used. Examples of plastic films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose. Examples include films made of triacetate (TAC), cellulose acetate propionate (CAP), and the like. By using a plastic film, the weight can be reduced as compared with the case of using a glass substrate, the portability can be improved, and the resistance to impact can be improved.

  An element protective layer can be provided on the thin film transistor element of the present invention. Examples of the protective layer include the inorganic oxides and inorganic nitrides described above, and the protective layer is preferably formed by the atmospheric pressure plasma method described above.

  Hereinafter, examples of a thin film transistor using an oxide semiconductor thin film obtained by oxidizing a thin film containing a dispersion of metal fine particles according to the present invention will be described.

  This will be described with reference to the schematic view of the thin film transistor manufacturing process of FIG.

A polyethersulfone resin film (200 μm) was used as the resin support 11, and first, this was subjected to corona discharge treatment under the condition of 50 W / m ² / min. Thereafter, an undercoat layer was formed in order to improve adhesion as follows.

(Formation of undercoat layer)
A coating solution having the following composition was applied to a dry film thickness of 2 μm, dried at 90 ° C. for 5 minutes, and then cured for 4 seconds from a distance of 10 cm under a 60 W / cm high-pressure mercury lamp.

Dipentaerythritol hexaacrylate monomer 60g
Dipentaerythritol hexaacrylate dimer 20g
Dipentaerythritol hexaacrylate trimer or higher component 20g
Diethoxybenzophenone UV initiator 2g
Silicone surfactant 1g
75g of methyl ethyl ketone
Methyl propylene glycol 75g
Further, a 50 nm-thick silicon oxide film was formed on the layer by continuous atmospheric pressure plasma treatment under the following conditions, and these layers were used as the undercoat layer 18 (FIG. 4 (1)).

(Used gas)
Inert gas: helium 98.25% by volume
Reactive gas: oxygen gas 1.5 volume%
Reactive gas: Tetraethoxysilane vapor (bubbled with helium gas) 0.25% by volume
(Discharge conditions)
Discharge output: 10 W / cm ²
(Electrode condition)
The electrode is 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 a solution obtained by diluting tetramethoxysilane with ethyl acetate is applied and dried, and then sealed by ultraviolet irradiation. This is a roll electrode having a dielectric (relative permittivity of 10) that has been subjected to hole treatment and has a smooth surface and an Rmax of 5 μm, and is grounded. On the other hand, as the application electrode, a hollow rectangular stainless steel pipe was coated with the same dielectric as described above under the same conditions.

Next, a gate electrode is formed. An aluminum film having a thickness of 300 nm was formed on one surface by sputtering, and then etched by photolithography to form the gate electrode 12. (Fig. 5 (2))
(Anodized film forming process)
After forming the gate electrode, the substrate is washed thoroughly, and the anode is formed in a 30% by mass aqueous ammonium phosphate solution using a direct current supplied from a constant voltage power source of 30 V for 2 minutes until the thickness of the anodized film reaches 120 nm. Oxidized.

Next, at a film temperature of 200 ° C., a silicon oxide film having a thickness of 30 nm was provided by the above-described atmospheric pressure plasma method, and the above-described anodized aluminum layer was combined to form a gate insulating film 13 having a thickness of 150 nm. (Fig. 5 (3))
Next, a dispersion liquid (produced by the method described in Japanese Patent No. 2561537) in which fine particles having an average particle diameter of 8 nm made of an alloy of In, Zn with a composition ratio of 1: 1 are dispersed in toluene is used by using an inkjet apparatus. Then, the film was discharged onto the gate insulating film on which the gate electrode was arranged, and the dispersion medium was cast to form a thin film containing metal fine particles. The average film thickness was 30 nm (FIG. 5 (4)). Further, dry cleaning was performed by irradiating a 50 W low-pressure mercury lamp in the atmosphere at a distance of 30 mm from the film surface for 2 minutes. Furthermore, oxidation treatment was performed at a film temperature of 200 ° C. under the following conditions using oxygen plasma by an atmospheric pressure plasma method. The alloy thin film turned transparent and was converted to a metal oxide thin film 14 having a thickness of about 60 nm.

  The oxygen plasma was processed under the following conditions using the same apparatus as described above.

(Used gas)
Inert gas: Nitrogen gas 98% by volume
Reactive gas: 2% by volume of oxygen gas
(Discharge conditions)
Discharge output: 10 W / cm ²
Next, gold was deposited using a mask to form the source electrode 15 and the drain electrode 16 (FIG. 5 (5)). Each size is 10 μm wide, 50 μm long (channel width) and 50 nm thick, and the distance (channel length) between the source electrode 15 and the drain electrode 16 is 15 μm.

The thin film transistor manufactured by the above method was driven well and showed n-type enhancement operation. An increase in drain current (transfer characteristics) was observed when the drain bias was 10 V and the gate bias was swept from -10 V to +20 V. The mobility estimated from the saturation region was 8.5 cm ² / Vs, and the on / off ratio was 6 digits.

It is a figure which shows typically the process in which melt | fusion progresses. It is a schematic diagram which shows typically the formation process of an oxide semiconductor thin film. It is sectional drawing which shows some structural examples of a thin-film transistor. It is a schematic equivalent circuit diagram of an example of a thin-film transistor sheet. The schematic diagram of a thin-film transistor manufacturing process is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor layer 2 Source electrode 3 Drain electrode 4 Gate electrode 5 Insulating layer 20 Thin-film transistor sheet 21 Gate bus line 22 Source bus line 24 Thin-film transistor element 25 Storage capacitor 26 Output element 27 Vertical drive circuit 28 Horizontal drive circuit

Claims (10)

An oxide semiconductor thin film obtained by providing a thin film containing a dispersion of metal fine particles and then oxidizing the thin film. 2. The oxide semiconductor thin film according to claim 1, wherein the metal fine particles have an average particle diameter of 1 to 300 nm. 3. The oxide semiconductor thin film according to claim 1, wherein the metal fine particles include any one of In, Zn, and Sn. 4. The oxide semiconductor thin film according to claim 1, wherein the metal fine particles contain one of Ga and Al. The oxide semiconductor thin film according to claim 1, wherein the oxidation is performed by plasma oxidation. 5. The oxide semiconductor thin film according to claim 4, wherein the substrate temperature during oxidation is 50 ° C. to 250 ° C. 5. The oxide semiconductor thin film according to claim 1, wherein the oxidation is thermal oxidation. The oxide semiconductor thin film according to claim 1, wherein the thin film formed by fusing the metal fine particles is oxidized after the thin film containing the dispersion of metal fine particles is provided. A thin film transistor comprising the oxide semiconductor thin film according to claim 1 as an active layer. A method for producing an oxide semiconductor thin film, comprising: providing a thin film containing a dispersion of metal fine particles; and oxidizing the thin film.

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