JP2010093164A - Thin-film transistor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate conversion of an oxide semiconductor precursor formed from a coated film into an oxide film by microwave heating, thereby improving a production efficiency of a thin-film transistor element having an oxide semiconductor film as an active layer. <P>SOLUTION: In a method of manufacturing a thin-film transistor for heating an oxide semiconductor precursor thin film and converting it to an oxide semiconductor film, a material which absorbs microwaves and generates heat is disposed inside the precursor thin film or in contact with the precursor thin film, and microwaves are applied to the material so that it is converted to the oxide semiconductor film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a metal oxide semiconductor with high semiconductor conversion efficiency, wherein a metal salt that can be applied with an aqueous solution is used as a precursor to perform a semiconductor conversion process to form a metal oxide semiconductor.

  A thin film transistor using an amorphous oxide as an active layer is known (for example, Patent Documents 1 and 2).

  Conventionally, a vapor deposition method, a pulse laser deposition method, a sputtering method, or the like is used to form a semiconductor thin film, and patterning is generally performed using a photolithograph. Also, each time the process is complicated, such as using a photoresist.

  On the other hand, as a technique for oxidizing a metal film as a precursor and converting it to a metal oxide semiconductor film, a film containing a metal such as Cu, Zn, Al, etc. formed on a substrate is oxidized by thermal oxidation, plasma oxidation, etc. Attempts to convert to an oxide semiconductor film have been made (for example, Patent Document 3). There is a description such as In in the dopant.

  It is also known that an amorphous oxide semiconductor is formed by forming a thin film containing an organic metal as a precursor by coating and subjecting it to decomposition oxidation (heating, decomposition reaction) (for example, Patent Document 4). .

  In addition, synthesis of an oxide semiconductor thin film by a sol-gel method is also known (Non-Patent Document 1).

  According to these, an oxide semiconductor thin film can be easily formed by forming a precursor thin film by a coating method without using a complicated process and performing a conversion treatment using thermal oxidation or plasma oxidation.

  However, when a normal thermal oxidation method is used, processing in a very high temperature range of 300 ° C. or higher is necessary, energy efficiency is low, a relatively long processing time is required, and a substrate being processed Since the temperature also rises to the same temperature as the processing temperature, it is difficult to apply it to a resin substrate that is light and flexible.

  In the case of plasma oxidation, since processing is performed in a very reactive plasma space, in the thin film transistor manufacturing process, electrodes and insulating films are deteriorated, and mobility and off current (dark current) deteriorate. Problems occur.

Therefore, it is necessary to improve the energy efficiency required for the conversion from the precursor to the semiconductor and to improve the deterioration of characteristics.
JP 2006-165528 A JP 2006-186319 A JP 2003-179242 A JP 2005-223231 A Chemical Industry, December 2006, pages 7-12

  Accordingly, an object of the present invention is to facilitate conversion of an oxide semiconductor precursor formed from a coating film into an oxide film by using microwave heating, and to provide a thin film transistor element having an oxide semiconductor film as an active layer. It is to improve production efficiency.

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

  1. In a thin film transistor manufacturing method in which a precursor thin film of an oxide semiconductor is heated to be converted into an oxide semiconductor film, a material that absorbs microwaves and generates heat is disposed inside the precursor thin film or in contact with the precursor thin film. A method for manufacturing a thin film transistor, wherein the material is converted into an oxide semiconductor film by irradiation with microwaves.

  2. 2. The method for producing a thin film transistor according to 1 above, wherein the oxide semiconductor precursor thin film is formed from a coating solution of a precursor solution or dispersion.

  3. 3. The method of manufacturing a thin film transistor according to 1 or 2 above, wherein the material that absorbs microwaves and generates heat is a metal oxide.

  4). 4. The method of manufacturing a thin film transistor according to 3 above, wherein the material that generates heat is a conductor.

  5. 5. The method for producing a thin film transistor according to 3 or 4 above, wherein the material that generates heat is fine particles of metal oxide.

  6). 6. A thin film transistor produced using the method for producing a thin film transistor according to any one of 1 to 5 above.

  According to the present invention, conversion of an oxide semiconductor precursor formed from a coating film into an oxide film can be facilitated by using microwave heating, and the production efficiency of a thin film transistor element using an oxide semiconductor film as an active layer is improved. Can be made.

  The best mode for carrying out the present invention will be described below.

  The present invention improves the energy efficiency of conversion by using a material having an electromagnetic wave absorbing ability for converting an oxide semiconductor precursor thin film into a semiconductor.

  According to such a method, a semiconductor thin film can be manufactured by a coating process (printing or IJ), and the precursor thin film can be efficiently converted into a semiconductor without deterioration of the characteristics. Efficiency can be improved.

(Microwave irradiation)
In the present invention, a material that absorbs microwaves and generates heat with respect to a metal oxide precursor thin film is disposed inside the precursor thin film or in contact with the precursor thin film, and the microwave (0.5 to 50 GHz) is disposed here. ). Then, since the material that absorbs microwaves generates heat, it is possible to efficiently convert the precursor thin film adjacent thereto to an oxide semiconductor film using the generated heat.

  If a material that absorbs microwaves and generates heat inside the semiconductor precursor thin film is dispersed, for example, in the form of fine particles, the fine particles of the material that absorbs microwaves and generates heat in contact with the precursor thin film are uniformly distributed. By arranging, when irradiated with microwaves, electrons in the material that absorbs microwaves and generates heat oscillates, generating Joule heat, so the precursor thin film is heated uniformly from the inside and from the close proximity region. The

  In microwave heating, microwave absorption concentrates on strongly absorbing substances and can be heated up to 500-600 ° C. in a very short time. Therefore, when this method is used in the present invention, The substrate itself is not affected by heating due to electromagnetic waves, and the material that absorbs microwaves in the precursor thin film and generates heat rises in a short time, and the precursor thin film is heated and fired to obtain the precursor. It becomes possible to convert a thin film into a semiconductor. For example, since a substrate such as glass or resin hardly absorbs in the microwave region, the semiconductor substrate itself hardly generates heat, and only the semiconductor precursor thin film portion can be selectively heated.

  The microwave generally refers to an electromagnetic wave having a frequency of 0.5 to 50 GHz, and is used in 0.8 MHz and 1.5 GHz band, 2 GHz band, amateur radio, aircraft radar, etc. used in mobile communication. The 1.2 GHz band, microwave oven, local radio, 2.4 GHz band used for VICS, 3 GHz band used for ship radar, etc., and 5.6 GHz used for other ETC communications are all in the microwave category. It is.

  In the present invention, the material that absorbs microwaves and generates heat is preferably a metal oxide. Indium oxide, tin oxide, zinc oxide, and the like are preferable. Among them, a conductor is preferable, and when ITO, IZO, or the like, which is a conductor, is used, In oxide, Zn oxide, and particularly Sn oxide have electromagnetic wave absorption ability. Because it is high, it becomes a strong heat source when irradiated with microwaves.For example, when these fine particles are uniformly dispersed in the precursor thin film, and when these fine particles are uniformly arranged on the precursor thin film, The precursor thin film is rapidly heated from the inside or from a very close position due to the heat generation of ITO by irradiation, so that the conversion to a semiconductor is performed quickly and the efficiency of forming an oxide semiconductor by firing (thermal oxidation) is improved. be able to.

  Therefore, the present invention can selectively and uniformly heat the semiconductor precursor thin film in a short time.

  A method in which a metal oxide semiconductor precursor thin film contains a material that absorbs microwaves to generate heat and is irradiated with microwaves is a method in which the precursor thin film is subjected to a firing reaction in a short time. However, since heat is transferred to the base material due to heat conduction, the substrate can be controlled by controlling the microwave output, the irradiation time, and the number of times of irradiation, especially in the case of a base material with low heat resistance such as a resin substrate. It can process so that temperature may be 50 to 200 degreeC and the surface temperature of the thin film containing a precursor will be 200 to 400 degreeC. The temperature of the thin film surface, the temperature of the substrate, etc. can be measured by a surface thermometer using a thermocouple or a non-contact surface thermometer.

  In the present invention, “arranged in the precursor thin film or in contact with the precursor” means that the island that absorbs microwaves and generates heat is isolated in the precursor thin film, for example, in the form of particles. This means that they are arranged inside or in contact with the thin film in a form separated from each other. Accordingly, the material that absorbs microwaves and generates heat is preferably in the form of fine particles, and the thin film transistor element or the like includes a source, a drain electrode, a gate electrode, a bus line, etc. in contact with or adjacent to the semiconductor layer. However, it is particularly preferable that the continuous layer that short-circuits the source and drain electrodes is dispersed and disposed so that the material that absorbs the microwave and generates heat so that the material that absorbs the microwave does not form.

For example, fine particles such as ITO as a conductor are used. Fine particles having an average particle diameter of 1 nm to ⁵ μm, particularly 5 nm to 100 nm are preferable, and they are preferably arranged at a surface density of 10 ⁵ particles / μm ² or less and 0.1 particles / μm ² or more with respect to the semiconductor thin film plane. The number can be measured by using an SPM such as an optical microscope, an electron microscope, or an AFM.

  As a material that absorbs microwaves and generates heat, an oxide containing any metal element such as In, Sn, Zn, Mn, or Mo, or a semiconductor such as Si or Ge is preferable. The conductivity is increased by a technique such as doping. A conductor or resistor improved to 0.1 S / cm or more is preferable. For example, indium oxide, tin oxide, zinc oxide, IZO, ITO, FTO, AZO and the like are preferable. In particular, ITO fine particles are preferable because they are very fine and highly dispersed.

  These metal oxide fine particles are obtained, for example, from a gel-like material obtained by heating a solution having a adjusted pH, by a method such as heating or low-temperature sintering. A paint (ink) dispersed in an appropriate solvent is preferable because it does not cause clogging due to aggregation or the like and is highly dispersed.

  Moreover, it can manufacture by the PVS (Physical Vapor Synthesis) method etc. A metal raw material is generated as vapor of metal atoms by thermal energy, and forms metal oxide molecules and clusters by contact with a reactive gas (oxygen). Thereafter, an ultrafine particle material in which an increase in particle size is suppressed is manufactured by instantaneous cooling. Since the semiconductor (precursor) thin film is disposed inside and in contact with the thin film, nanoparticles having a particle size of 50 nm or less are preferable. Such particles are preferably in the range of 5 nm to 50 nm.

These are commercially available and can also be obtained directly from the market. Examples thereof include ITO dispersions manufactured by ULVAC, such as NanoTek Slurry ITO manufactured by CI Kasei Co., Ltd., SnO _{2 and the} like.

Also available as powder, SnO ₂ fine particles (Nanotech powder SnO ₂ : 21 nm), ITO fine particles (Nanotech powder ITO: 30 nm) and the like can be obtained and used by being dispersed in various solvents.

  As described above, by performing microwave heating, the precursor thin film of the metal oxide semiconductor of the present invention absorbs the microwave disposed inside or in contact with the semiconductor precursor by heat from a material that generates heat. The thin film is heated to a high temperature uniformly in a short time, and conversion into an oxide semiconductor is efficiently performed.

  According to the method of the present invention that increases the efficiency of heat treatment by microwave irradiation, semiconductor performance can be obtained in a short time without requiring a high process temperature as compared with baking treatment by an electric furnace or the like.

  The metal oxide semiconductor (thin film) according to the present invention can be used in various electronic devices, TFT elements, electronic circuits, etc., and a metal oxide semiconductor layer can be produced by a low temperature process, and a resin substrate is used. It can be preferably applied to the manufacture of a thin film transistor element (TFT element).

  In the present invention, a precursor of an oxide semiconductor is a material that is converted into a metal oxide (semiconductor) by heating. In the present invention, a material that absorbs microwaves and generates heat is used inside the precursor thin film or as a precursor. By placing the thin film in contact with the thin film and irradiating the material with microwaves, the precursor material is converted into an oxide semiconductor by heat generated from the material.

(precursor)
In the present invention, examples of the oxide semiconductor precursor material include metal atom-containing compounds, and examples of the metal atom-containing compound include metal salts, metal halide compounds, and organometallic compounds containing metal atoms. .

  Metals of metal salts, halogen metal compounds, and organometallic compounds include Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb, Bi, Ce, Pr Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like.

  Among these metal salts, it is preferable to contain any metal ion of In (indium), Sn (tin), or Zn (zinc), and they may be used in combination.

  Moreover, it is preferable that other metals include Ga (gallium) or Al (aluminum).

  As metal salts, nitrates, sulfates, phosphates, carbonates, acetates or oxalates are preferred. Further, nitrates, acetates, etc. are used, and chlorides, iodides, bromides, etc. are suitably used as halogen metal compounds. be able to.

  Examples of the organometallic compound include those represented by the following general formula (I).

Formula (I) R ¹ _x MR ² _y R ³ _z
In the formula, M is a metal, R ¹ is an alkyl group, R ² is an alkoxy group, R ³ is a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group, and a ketooxy group (ketooxy complex group). X + y + z = m, x = 0 to m, or x = 0 to m−1, and y = 0 to m, z = 0. ~ M, each of which is 0 or a positive integer. Examples of the alkyl group for R ¹ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkoxy group for R2 include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a 3,3,3-trifluoropropoxy group. Further, a hydrogen atom in the alkyl group may be substituted with a fluorine atom. Examples of the group selected from the β-diketone complex group, β-ketocarboxylic acid ester complex group, β-ketocarboxylic acid complex group and ketooxy group (ketooxy complex group) of R3 include, for example, 2,4-diketone complex group, Pentanedione (also called acetylacetone or acetoacetone), 1,1,1,5,5,5-hexamethyl-2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 1,1,1-trifluoro-2,4-pentanedione and the like, and β-ketocarboxylic acid ester complex groups include, for example, acetoacetic acid methyl ester, acetoacetic acid ethyl ester, acetoacetic acid propyl ester, trimethylacetoacetic acid Ethyl, methyl trifluoroacetoacetate and the like can be mentioned, and examples of β-ketocarboxylic acid include , Acetoacetic acid, there may be mentioned trimethyl acetoacetate, and as Ketookishi, for example, can be exemplified acetoxy group (or an acetoxy group), a propionyloxy group, Buchirirokishi group, acryloyloxy group, a methacryloyloxy group. These groups preferably have 18 or less carbon atoms. Further, it may be linear or branched, or a hydrogen atom may be a fluorine atom. Among organometallic compounds, those having at least one oxygen in the molecule are preferable. As such, an organometallic compound containing at least one alkoxy group of R ² , a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group and a ketooxy group (ketooxy group) of R ³ Most preferred are metal compounds having at least one group selected from (complex groups). Of the metal salts, nitrates are preferred. Nitrate is easily available as a high-purity product and has high solubility in water, which is preferable as a medium for use. Examples of nitrates include indium nitrate, tin nitrate, zinc nitrate, and gallium nitrate.

  Of the above oxide semiconductor precursors, preferred are metal nitrates, metal halides, and alkoxides. Specific examples include indium nitrate, zinc nitrate, gallium nitrate, tin nitrate, aluminum nitrate, indium chloride, zinc chloride, tin chloride (divalent), tin chloride (tetravalent), gallium chloride, aluminum chloride, tri-i-. Examples include propoxyindium, diethoxyzinc, bis (dipivaloylmethanato) zinc, tetraethoxytin, tetra-i-propoxytin, tri-i-propoxygallium, and tri-i-propoxyaluminum.

(Method for depositing oxide semiconductor precursor thin film)
In order to form a thin film containing a metal as a precursor of these oxide semiconductors, a known film formation method, vacuum deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, ion plate Various methods such as a coating method, a CVD method, a sputtering method, and an atmospheric pressure plasma method can be used. In the present invention, a substrate is used by using a solution in which a metal salt, a halide, an organometallic compound, or the like is dissolved in an appropriate solvent. It is preferable that the coating is continuously performed on the top because productivity can be greatly improved. From the viewpoint of solubility, it is preferable to use chloride, nitrate, acetate, metal alkoxide, or the like as the metal compound.

  The solvent is not particularly limited as long as it dissolves metal compounds in addition to water, but water, alcohols such as ethanol, propanol and ethylene glycol, ethers such as tetrahydrofuran and dioxane, and methyl acetate. , Esters such as ethyl acetate, ketones such as acetone, methyl ethyl ketone, cyclohexanone, glycol ethers such as diethylene glycol monomethyl ether, acetonitrile, and other aromatic hydrocarbon solvents such as xylene and toluene, o-dichlorobenzene, Aromatic solvents such as nitrobenzene and m-cresol, aliphatic hydrocarbon solvents such as hexane, cyclohexane and tridecane, α-terpineol, and halogenated alkyl solvents such as chloroform and 1,2-dichloroethane, - methylpyrrolidone, can be preferably used carbon disulfide and the like.

  When a metal halide and / or metal alkoxide is used, a solvent having a relatively high polarity is preferable. Among them, water having a boiling point of 100 ° C. or less, alcohols such as ethanol and propanol, acetonitrile, or a mixture thereof is used. Since the drying temperature can be lowered, it can be applied to the resin substrate, which is more preferable. In particular, the solvent preferably contains 50% by mass or more of water or alcohol.

  Addition of metal alkoxide and various ligands such as alkanolamines, α-hydroxy ketones, β-diketones and other chelating ligands in the solvent stabilizes the metal alkoxide and the solubility of the carboxylate. It is preferable to add in a range that does not cause adverse effects.

  As a method of forming a thin film by applying a liquid containing an oxide semiconductor precursor material on a substrate, a spin coating method, a spray coating method, a blade coating method, a dip coating method, a casting method, a bar coating method, Examples of the coating method include a coating method in a broad sense, such as a coating method such as a die coating method, and a printing method such as a relief printing plate, an intaglio printing plate, a planographic printing method, a screen printing method, and an ink jet printing method. An ink jet method, a spray coating method, and the like that can apply a thin film are also preferable methods.

  In the case of film formation, a thin film of a metal oxide precursor is formed by volatilizing the solvent at about 50 to 150 ° C. after coating. In addition, when dropping the solution, it is preferable to heat the substrate itself to the above temperature because two processes of coating and drying can be performed simultaneously.

  Photolithographic methods can be used for patterning the semiconductor precursor layer or the semiconductor thin film.

  As a coating method of the photoresist layer, a known coating method such as dipping, spin coating, knife coating, bar coating, blade coating, squeeze coating, reverse roll coating, gravure roll coating, curtain coating, spray coating, die coating or the like is used. It can be carried out.

  The exposure method for the photoresist layer is not particularly limited, and flash exposure may be performed through a mask such as a xenon lamp, a halogen lamp, or a mercury lamp, or scanning exposure may be performed using laser light. Laser exposure can be preferably used because the exposure area can be easily reduced to a very small size and a high-resolution image can be formed.

The laser light may be any of ultraviolet light, visible light, and infrared light, and is generally well-known solid laser such as ruby laser, YAG laser, glass laser; He—Ne laser, Ar ion laser, Kr ion laser, CO Gas laser such as ₂ laser, CO laser, He—Cd laser, N ₂ laser, and excimer laser; Semiconductor laser such as InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP ₂ laser, and GaSb laser; Chemical laser And a dye laser. A semiconductor laser having a transmission wavelength in the infrared region is preferable.

  An oxide semiconductor precursor material thin film is preferably used by an inkjet method or the like because it can be directly patterned on the semiconductor layer. In particular, the use of an electrostatic attraction type ink jet apparatus (SIJ) is preferable for drawing a fine pattern because fine droplets can be ejected and drawn with high accuracy.

[Electrostatic suction type liquid discharge device]
FIG. 1 is a cross-sectional view showing the overall configuration of an electrostatic suction type liquid ejection apparatus preferably used in the present invention. The liquid discharge head 2 of the present invention can be applied to various liquid discharge apparatuses such as a so-called serial method or line method.

  The liquid ejection apparatus 1 according to the present embodiment includes a liquid ejection head 2 on which a nozzle 10 that ejects a droplet D of a chargeable liquid L such as ink is formed, and an opposing surface that faces the nozzle 10 of the liquid ejection head 2. And a counter electrode 3 that supports the base material K that receives the landing of the droplet D on the opposing surface thereof.

  A resin nozzle plate 11 having a plurality of nozzles 10 is provided on the side of the liquid ejection head 2 facing the counter electrode 3. The liquid discharge head 2 is configured as a head having a flat discharge surface in which the nozzle 10 does not protrude from the discharge surface 12 facing the counter electrode 3 of the nozzle plate 11 or the nozzle 10 protrudes only about 30 μm as described above. (For example, see FIG. 2D described later).

  Each nozzle 10 is formed by perforating a nozzle plate 11, and each nozzle 10 has a small-diameter portion 14 having a discharge hole 13 on the discharge surface 12 of the nozzle plate 11 and a larger diameter formed behind the small-diameter portion 14. A two-stage structure with the large-diameter portion 15 is adopted. In the present embodiment, the small-diameter portion 14 and the large-diameter portion 15 of the nozzle 10 are each formed in a tapered shape having a circular cross-section and a smaller diameter on the counter electrode side. The nozzle diameter is 10 μm, and the internal diameter of the open end of the large diameter portion 15 farthest from the small diameter portion 14 is 75 μm.

  The shape of the nozzle 10 is not limited to the above-described shape, and various nozzles 10 having different shapes can be used, for example, as shown in FIGS. Further, the nozzle 10 may have a polygonal cross-section, a cross-sectional star shape, or the like instead of forming a circular cross-section.

  On the surface opposite to the ejection surface 12 of the nozzle plate 11, a charging electrode 16 made of a conductive material such as NiP, for example, for charging the liquid L in the nozzle 10 is provided in layers. In the present embodiment, the charging electrode 16 extends to the inner peripheral surface 17 of the large-diameter portion 15 of the nozzle 10 and comes into contact with the liquid L in the nozzle.

  The charging electrode 16 is connected to a charging voltage power source 18 as an electrostatic voltage applying means for applying an electrostatic voltage that generates an electrostatic attractive force, and the single charging electrode 16 is connected to all the nozzles 10. When the electrostatic voltage is applied from the charging voltage power source 18 to the charging electrode 16, the liquid L in all the nozzles 10 is simultaneously charged, and the liquid ejection head 2 and the counter electrode 3 are in contact with each other. In particular, an electrostatic attraction force is generated between the liquid L and the substrate K.

  A body layer 19 is provided behind the charging electrode 16. A portion of the body layer 19 facing the opening end of the large-diameter portion 15 of each nozzle 10 is formed with a substantially cylindrical space having an inner diameter substantially equal to the opening end, and each space is discharged. The cavity 20 is used for temporarily storing the liquid L.

  Behind the body layer 19 is provided a flexible layer 21 made of a flexible metal thin plate, silicon, or the like. The flexible layer 21 defines the liquid ejection head 2 from the outside.

  In the body layer 19, a flow path (not shown) for supplying the liquid L to the cavity 20 is formed. Specifically, the silicon plate as the body layer 19 is etched to provide a cavity 20, a common channel, and a channel that connects the common channel and the cavity 20. A supply pipe (not shown) for supplying the liquid L from a liquid tank (not shown) is connected, and the flow path, the cavity 20, the nozzle 10, etc. A predetermined supply pressure is applied to the liquid L.

  Piezo elements 22 that are piezoelectric element actuators as pressure generating means are provided in portions corresponding to the respective cavities 20 on the outer surface of the flexible layer 21, and a drive voltage is applied to the elements. A drive voltage power source 23 for deforming the element is connected. The piezo element 22 is deformed by the application of a drive voltage from the drive voltage power source 23 to generate a pressure on the liquid L in the nozzle, thereby forming a meniscus of the liquid L in the discharge hole 13 of the nozzle 10. . In addition to the piezoelectric element actuator as in the present embodiment, for example, an electrostatic actuator, a thermal method, or the like can be adopted as the pressure generating means.

  The charging voltage power supply 18 for applying an electrostatic voltage to the drive voltage power supply 23 and the charging electrode 16 is connected to the operation control means 24, and is controlled by the operation control means 24, respectively.

  In this embodiment, the operation control means 24 is composed of a computer in which a CPU 25, a ROM 26, a RAM 27, etc. are connected by a BUS (not shown). The CPU 25 is charged with a charging voltage based on a power control program stored in the ROM 26. The power supply 18 and each drive voltage power supply 23 are driven to discharge the liquid L from the discharge hole 13 of the nozzle 10.

  In the present embodiment, the liquid repellent layer 28 for suppressing the oozing of the liquid L from the discharge holes 13 is provided on the discharge surface 12 other than the discharge holes 13 on the discharge surface 12 of the nozzle plate 11 of the liquid discharge head 2. It is provided on the entire surface. For the liquid repellent layer 28, for example, a material having water repellency is used if the liquid L is aqueous, and a material having oil repellency is used if the liquid L is oily. Fluorine resins such as hexafluoropropylene), PTFE (polytetrafluoroethylene), fluorine siloxane, fluoroalkylsilane, and amorphous perfluoro resin are often used, and a film is formed on the discharge surface 12 by a method such as coating or vapor deposition. Has been. The liquid repellent layer 28 may be formed directly on the ejection surface 12 of the nozzle plate 11 or may be formed through an intermediate layer in order to improve the adhesion of the liquid repellent layer 28. .

  Below the liquid discharge head 2, a plate-like counter electrode 3 that supports the substrate K is disposed in parallel to the discharge surface 12 of the liquid discharge head 2 and separated by a predetermined distance. The separation distance between the counter electrode 3 and the liquid ejection head 2 is appropriately set within a range of about 0.1 mm to 3 mm.

  In the present embodiment, the counter electrode 3 is grounded and is always maintained at the ground potential. Therefore, when an electrostatic voltage is applied from the charging voltage power source 18 to the charging electrode 16, an electric field is generated between the liquid L in the ejection hole 13 of the nozzle 10 and the opposing surface of the counter electrode 3 facing the liquid ejection head 2. Has come to occur. When the charged droplet D lands on the substrate K, the counter electrode 3 releases the electric charge by grounding.

  The counter electrode 3 or the liquid ejection head 2 is provided with positioning means (not shown) for positioning the liquid ejection head 2 and the substrate K by relatively moving them. The droplets D discharged from each nozzle 10 can be landed on the surface of the substrate K at an arbitrary position.

The liquid L discharged by the liquid discharge apparatus 1 is, for example, water, COCl ₂ , HBr, HNO ₃ , H ₃ PO ₄ , H ₂ SO ₄ , SOCl ₂ , SO ₂ Cl ₂ , or FSO ₃ H as an inorganic liquid. Etc. Examples of the organic liquid include methanol, n-propanol, isopropanol, n-butanol, 2-methyl-1-propanol, tert-butanol, 4-methyl-2-pentanol, benzyl alcohol, α-terpineol, ethylene glycol, Alcohols such as glycerin, diethylene glycol and triethylene glycol; phenols such as phenol, o-cresol, m-cresol and p-cresol; dioxane, furfural, ethylene glycol dimethyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethyl carbitol, Ethers such as butyl carbitol, butyl carbitol acetate, epichlorohydrin; acetone, methyl ethyl ketone, 2-methyl-4-pentanone, Ketones such as tophenone; fatty acids such as formic acid, acetic acid, dichloroacetic acid, trichloroacetic acid; methyl formate, ethyl formate, methyl acetate, ethyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-3-methoxybutyl, acetic acid- n-pentyl, ethyl propionate, ethyl lactate, methyl benzoate, diethyl malonate, dimethyl phthalate, diethyl phthalate, diethyl carbonate, ethylene carbonate, propylene carbonate, cellosolve acetate, butyl carbitol acetate, ethyl acetoacetate, cyanoacetic acid Esters such as methyl and ethyl cyanoacetate; nitromethane, nitrobenzene, acetonitrile, propionitrile, succinonitrile, valeronitrile, benzonitrile, ethylamine, diethylamine, ethylenediamine, aniline, N-methylanily , N, N-dimethylaniline, o-toluidine, p-toluidine, piperidine, pyridine, α-picoline, 2,6-lutidine, quinoline, propylenediamine, formamide, N-methylformamide, N, N-dimethylformamide, Nitrogen-containing compounds such as N, N-diethylformamide, acetamide, N-methylacetamide, N-methylpropionamide, N, N, N ′, N′-tetramethylurea, N-methylpyrrolidone; dimethyl sulfoxide, sulfolane, etc. Sulfur-containing compounds: benzene, p-cymene, naphthalene, cyclohexylbenzene, cyclohexene and other hydrocarbons; 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,1, 2-tetrachloroethane, 1,1,2,2-te Lachloroethane, pentachloroethane, 1,2-dichloroethylene (cis-), tetrachloroethylene, 2-chlorobutane, 1-chloro-2-methylpropane, 2-chloro-2-methylpropane, bromomethane, tribromomethane, 1-bromopropane And halogenated hydrocarbons. Two or more of the above liquids may be mixed and used.

  Here, the discharge principle of the liquid L in the liquid discharge head 2 is demonstrated using FIG.

  In the present embodiment, an electrostatic voltage is applied from the charging voltage power source 18 to the charging electrode 16, and an electric field is generated between the liquid L in the ejection hole 13 of the nozzle 10 and the opposing surface of the counter electrode 3 facing the liquid ejection head 2. Give rise to Further, a driving voltage is applied from the driving voltage power source 23 to the piezo element 22 to deform the piezo element 22, thereby forming a meniscus of the liquid L in the discharge hole 13 of the nozzle 10 with the pressure generated in the liquid L.

  When the insulation property of the nozzle plate 11 is increased as in the present embodiment, the equipotential lines in the nozzle plate 11 are substantially perpendicular to the ejection surface 12 as shown by equipotential lines by simulation in FIG. And a strong electric field is generated toward the liquid L in the small diameter portion 14 of the nozzle 10 and the meniscus portion of the liquid L.

  In particular, as can be seen from the fact that the equipotential lines are dense at the tip of the meniscus in FIG. 3, a very strong electric field concentration occurs at the tip of the meniscus. Therefore, the meniscus is torn off by the electrostatic force of the electric field and separated from the liquid L in the nozzle to become a droplet D. Further, the droplet D is accelerated by the electrostatic force, and is attracted and landed on the base material K supported by the counter electrode 3. At that time, since the droplet D attempts to land closer by the action of electrostatic force, the angle at the time of landing on the substrate K is stabilized and accurately performed.

  As described above, when the principle of discharging the liquid L in the liquid discharge head 2 of the present invention is used, the liquid discharge head 2 having a flat discharge surface also uses the nozzle plate 11 having high insulating properties to form the discharge surface 12. On the other hand, by generating a potential difference in the vertical direction, strong electric field concentration can be generated, and an accurate and stable discharge state of the liquid L can be formed.

  Hereinafter, a preferred embodiment of an electrostatic suction type liquid discharge apparatus preferably used in the present invention will be described with reference to the drawings. However, the present invention is not limited to these.

  The electrostatic suction type ink jet apparatus used in the present invention has a multi-nozzle head 100 as shown in FIG. The multi-nozzle head 100 includes a nozzle plate 31, a body plate 32, and a piezoelectric element 33. The nozzle plate 31 is a silicon substrate or a silicon oxide substrate having a thickness of about 150 μm to 300 μm. A plurality of nozzles 101 are formed on the nozzle plate 31, and the plurality of nozzles 101 are arranged in a line.

  The body plate 32 is a silicon substrate having a thickness of about 200 μm to 500 μm. In the body plate 32, an ink supply port 201, an ink storage chamber 202, a plurality of ink supply paths 203, and a plurality of pressure chambers 204 are formed.

  The ink supply port 201 is a circular through hole having a diameter of about 400 μm to 1500 μm.

  The ink storage chamber 202 is a groove having a width of about 400 μm to 1000 μm and a depth of about 50 μm to 200 μm.

  The ink supply path 203 is a groove having a width of about 50 μm to 150 μm and a depth of about 30 μm to 150 μm. The pressure chamber 204 is a groove having a width of about 150 μm to 350 μm and a depth of about 50 μm to 200 μm.

  The nozzle plate 31 and the body plate 32 are joined to each other, and in the joined state, the nozzle 101 of the nozzle plate 31 and the pressure chamber 204 of the body plate 32 correspond to each other on a one-to-one basis. .

  When ink is supplied to the ink supply port 201 in a state where the nozzle plate 31 and the body plate 32 are joined, the ink is temporarily stored in the ink storage chamber 202, and then each ink supply from the ink storage chamber 202 is performed. Each pressure chamber 204 is supplied through a passage 203.

  The piezoelectric element 33 is bonded to a position corresponding to the pressure chamber 204 of the body plate 32. The piezoelectric element 33 is an actuator made of PZT (lead zirconium titanate), and is deformed when a voltage is applied to eject ink inside the pressure chamber 204 from the nozzle 101.

  Although not shown in FIG. 4, a borosilicate glass plate 34 (see FIG. 6) is interposed between the nozzle plate 31 and the body plate 32.

  As shown in FIG. 5, one nozzle 101 and one pressure chamber 204 are configured corresponding to one piezoelectric element.

  In the nozzle plate 31, a step is formed in the nozzle 101, and the nozzle 101 includes a lower step portion 101a and an upper step portion 101b. Both the lower step portion 101a and the upper step portion 101b have a cylindrical shape, and the diameter D1 (the distance in the left-right direction in FIG. 5) of the lower step portion 101a is smaller than the diameter D2 (the distance in the left-right direction in FIG. 5) of the upper step portion 101b. It has become.

  The lower part 101a of the nozzle 101 is a part that directly ejects ink circulated from the upper part 101b. The lower step portion 101a has a diameter D1 of 1 μm to 10 μm and a length L (a distance in the vertical direction in FIG. 5) of 1.0 μm to 5.0 μm. The reason why the length L of the lower step portion 101a is limited to the range of 1.0 μm to 5.0 μm is that the ink landing accuracy can be remarkably improved.

  On the other hand, the upper stage portion 101b of the nozzle 101 is a part that circulates the ink circulated from the pressure chamber 204 to the lower stage portion 101a, and has a diameter D2 of 10 μm to 60 μm.

  The lower limit of the diameter D2 of the upper stage portion 101b is limited to 10 μm or more. If the diameter D2 is less than 10 μm, the flow path resistance of the upper stage portion 101b cannot be ignored with respect to the flow path resistance of the entire nozzle 101 (lower stage portion 101a and upper stage portion 101b). This is because the ink ejection efficiency tends to decrease.

  Conversely, the upper limit of the diameter D2 of the upper step portion 101b is limited to 60 μm or less because the lower step portion 101a as the ink discharge site becomes thinner as the diameter D2 of the upper step portion 101b increases (the area of the lower step portion 101a increases). This is because the mechanical strength is reduced), and the ink is easily deformed when ejected, and as a result, the ink landing accuracy is lowered. That is, when the upper limit of the diameter D2 of the upper step portion 101b exceeds 60 μm, the deformation of the lower step portion 101a becomes very large as ink is ejected, and the landing accuracy can be suppressed within a specified value (= 0.5 °). This is because it may disappear.

  A borosilicate glass plate 34 having a thickness of about several hundred μm is provided between the nozzle plate 31 and the body plate 32, and the borosilicate glass plate 34 has an opening for communicating the nozzle 101 and the pressure chamber 204. A portion 34a is formed. The opening 34 a is a through-hole that communicates with the pressure chamber 204 and the upper stage portion 101 b of the nozzle 101, and is a part that functions as a flow path through which ink flows from the pressure chamber 204 toward the nozzle 101. The pressure chamber 204 is a portion that receives deformation of the piezoelectric element 33 and applies pressure to the ink inside the pressure chamber 204.

  In the multi-nozzle head 100 having the above configuration, when the piezoelectric element 33 is deformed, pressure is applied to the ink inside the pressure chamber 204, and the ink flows from the pressure chamber 204 through the opening 34 a of the borosilicate glass plate 34. Then, the nozzle 101 is reached and finally discharged from the lower step portion 101a of the nozzle 101.

  As an aspect of the ink jet apparatus according to the present invention, a substrate electrode is provided at a position facing the nozzle plate 1 of the multi-nozzle head 100 (not shown), and between the nozzle 101 and the substrate electrode. An electrostatic field is applied.

  For this reason, the ink ejected from the nozzle 101 lands on the recording material on the substrate electrode while receiving the action of the electrostatic field.

(Composition ratio of metal)
As a preferred metal composition ratio, when In is 1, Zn _y Sn _1-y (where y is a positive number from 0 to ₁ ) is 0.2 to 5, preferably 0.5 to 2. . Further, when In is 1, the Ga composition ratio is 0.2 to 5, preferably 0.5 to 2.

  Moreover, the film thickness of a precursor thin film is 1-200 nm, More preferably, it is 5-100 nm.

(Amorphous oxide)
As the oxide semiconductor formed by thermal oxidation, any state of single crystal, polycrystal, and amorphous can be used, but an amorphous thin film is preferable.

The electron carrier concentration of an amorphous oxide, which is a metal oxide according to the present invention, formed from a metal compound material that becomes a precursor of an oxide semiconductor only needs to be 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 temperature appropriately selected from the range of about 0 ° C. to 40 ° C. Note that the electron carrier concentration of the amorphous (amorphous) oxide according to the present invention does not need to satisfy less than 10 ¹⁸ / cm ³ in the entire 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 thin film transistor 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 precursor 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. 6 is a schematic cross-sectional view illustrating an example of the structure of the thin film transistor. The figure shows a cross-sectional view of a top-gate / top-contact thin film transistor including a semiconductor layer 306, a source electrode 304, and a drain electrode 305, in which a gate electrode 302 and a gate insulating film 303 are formed over a substrate 301. Show.

  The present invention is not limited to this element as long as the method of the present invention is used in the step of forming an active layer of a thin film transistor, that is, a semiconductor layer, and is in the scope of the present invention in any configuration. It is not limited only to these elements.

  Hereinafter, in the present invention, each element other than the semiconductor layer constituting the thin film transistor or the thin film transistor sheet will be described.

(electrode)
In the present invention, the conductive material used for the electrodes such as the source electrode, the drain electrode, and the gate electrode constituting the thin film transistor is not particularly limited as long as it has conductivity at a practical level as an electrode. Gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, for example, tin oxide / antimony, indium oxide・ Electrode materials with electromagnetic wave absorbing ability such as tin (ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium , Ma Gun, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, lithium / aluminum A mixture or the like is used.

  Moreover, a conductive polymer, metal microparticles, etc. can be used suitably as a conductive material.

  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, the above-described materials are used as a raw material, a method of forming using a method such as vapor deposition or sputtering through a mask, or a conductive thin film formed by a method such as vapor deposition or sputtering as a known photolithographic method, There are a method of forming an electrode using a lift-off method and a method of forming a resist on a metal foil such as aluminum or copper by thermal transfer, ink jet or the like and etching. 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.

  Further, as a method of forming a source, drain, gate electrode, etc., and a gate bus line, source bus line, etc. without patterning a metal thin film using a photosensitive resin such as etching or lift-off, a method by an electroless plating method It has been 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 on a portion where an electrode is provided After patterning, for example, 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 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 way, but 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.

(Gate insulation film)
Various insulating films can be used as a gate insulating film of the thin film transistor. In particular, an inorganic oxide film having a high relative dielectric constant is 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.

  As a method for forming the film, a dry process such as a vacuum deposition method, 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 CVD method, Examples include wet processes such as spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, and other coating methods, and printing and inkjet patterning methods. 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.

  Among these, the atmospheric pressure plasma method is preferable.

  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-cationic polymerization-type photo-curable 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.

[Protective layer]
It is also possible to provide a protective layer on the organic thin film transistor element. Examples of the protective layer include inorganic oxides or inorganic nitrides, metal thin films such as aluminum, polymer films with low gas permeability, and laminates thereof. By having such a protective layer, the durability of the organic thin film transistor can be obtained. Will improve. As a method for forming these protective layers, the same method as the method for forming the gate insulating film described above can be used. Further, the protective layer may be provided by a method such as simply laminating a film in which various inorganic oxides are laminated on the polymer film.

(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 (substrate) 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 (PPS), polyarylate, polyimide (PI), and polyamide. Examples thereof include films made of imide (PAI), polycarbonate (PC), cellulose 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.

  Hereafter, each process is demonstrated about the embodiment of manufacture of the preferable thin-film transistor of this invention using the cross-sectional schematic diagram of FIG.

Example 1
First, a polyethersulfone resin film (200 μm) was used as the substrate 301, and first, a corona discharge treatment was performed on the substrate 301 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 silicon oxide film having a thickness of 50 nm was formed on the layer by continuous atmospheric pressure plasma treatment under the following conditions, and these layers were used as an undercoat layer (barrier layer) 310 (FIG. 7 (1)). In addition, the atmospheric pressure plasma processing apparatus used the apparatus according to FIG. 6 as described in Unexamined-Japanese-Patent No. 2003-303520.

(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. After an aluminum film having a thickness of 300 nm was formed on one surface by sputtering, patterning was performed by photolithography to form a gate electrode 302 (FIG. 7 (1)).

  Next, at a film temperature of 200 ° C., a 180 nm thick silicon oxide film was provided by the atmospheric pressure plasma method described above to form a gate insulating film 303 (FIG. 7B).

Next, the substrate was immersed in a toluene solution (0.1% by mass, 60 ° C.) in which octyltrichlorosilane (C ₈ H ₁₇ SiCl ₃ ) (OTS) was dissolved, then rinsed with toluene, and further an ultrasonic cleaner. After the treatment for 10 minutes, the entire surface of the gate insulating film reacted with OTS to be surface-treated by drying. A monomolecular film made of octyltrichlorosilane is formed by the surface treatment, but this monomolecular film is represented by the surface treatment layer 308 for convenience (FIG. 7 (3)).

  After this surface treatment, ultraviolet light with a wavelength of 254 nm was irradiated from a low-pressure mercury lamp through a photomask M having a light transmission portion corresponding to the semiconductor channel region (FIG. 7 (4)). Thereby, the surface of the exposure part was decomposed | disassembled and the surface treatment part was hydrophilized. The decomposition product was removed by washing with ethanol to expose the surface of the gate insulating layer 303 corresponding to the channel region (FIG. 7 (5)).

  Next, a 10% by mass aqueous solution in which indium nitrate, zinc nitrate, and gallium nitrate, which are semiconductor precursor materials, are mixed at a metal ratio of 1: 1: 1 (molar ratio) is used as an ink in FIGS. In the electrostatic attraction type inkjet apparatus described above, a bias voltage of 2000 V is applied, and a pulse voltage (400 V) is further superimposed to eject ink according to a semiconductor layer pattern (substantially gate electrode pattern), thereby providing a semiconductor precursor material A thin film 306 'was formed (FIG. 7 (6)). The inner diameter of the nozzle outlet was 10 μm, and the gap between the nozzle outlet and the substrate was kept at 500 μm. At this time, the substrate temperature was 80 ° C.

  The precursor material thin film 306 ′ formed by heat treatment at 100 ° C. and drying was 30 nm in average thickness (FIG. 7 (7)).

Next, an ITO fine particle toluene dispersion (Cai Kasei Co., Ltd., NanoTek Slurry ITO (particle size 30 nm) 15% by mass dispersion) diluted with ink was prepared and discharged onto the surface with an inkjet device. The ITO fine particles were dispersed on the precursor material thin film 306 'so as not to form a continuous layer. FIG. 7 (8) schematically shows ITO fine particles dispersedly disposed on the precursor material thin film 306 ′. The ink was diluted and prepared so that the surface density was about 2000 / μm ² .

  Next, microwave irradiation was performed from the support side. That is, the treatment was performed at 200 ° C. for 20 minutes by irradiating with microwaves (2.45 GHz) at an output of 500 W under an atmospheric pressure condition where the partial pressure of oxygen and nitrogen was 1: 1. The precursor material was converted into an oxide semiconductor by heat generation due to microwave absorption of ITO fine particles placed on the ITO (gate electrode 302) and on the precursor material, and a semiconductor layer 306 was formed on the gate insulating film ( FIG. 7 (9)).

Next, the substrate was immersed again in a toluene solution (0.1 mass%, 60 ° C.) in which octyltrichlorosilane (C ₈ H ₁₇ SiCl ₃ ) (OTS) was dissolved, and then rinsed with toluene. After treatment in a sonic cleaner for 10 minutes and drying, the surface of the formed oxide semiconductor layer 306 having ITO fine particles also reacted with OTS to form a monomolecular film and surface treatment. Similarly, this monomolecular film was represented by the surface treatment layer 308 (FIG. 7 (10)).

  Next, a protective film is formed.

  The protective film formation region was irradiated with ultraviolet light of 254 nm using a mask covering the region other than the protective film formation region on the semiconductor layer (FIG. 7 (11)). The surface treatment layer 308 in the protective film formation region on the semiconductor layer was decomposed to expose the semiconductor layer. Note that since the width of the protective film forms the channel length (distance between the source electrode 304 and the drain electrode 305), the exposure region is adjusted so that the width of the protective film is 15 μm so that only the channel region of the semiconductor layer is exposed (FIG. 7 (12)).

  Perhydropolysilazane (Aquamica NP110 (registered trademark)) xylene solution, which is a protective film material, is deposited on the oxide semiconductor layer 306 in the oxide semiconductor layer using the same electrostatic suction ink jet apparatus as described above. (Fig. 7 (13)). Subsequently, this was heat-treated at 200 ° C. for 30 minutes to convert it into a silicon dioxide thin film layer to form a protective layer 307 (FIG. 7 (14)). The thickness of the protective layer was 200 nm.

  Next, the remaining surface treatment layer 308 is decomposed by oxygen plasma treatment under the following conditions using the same atmospheric pressure plasma apparatus as described above, and the surfaces other than the surfaces covered with the protective films of the gate insulating layer 303 and the semiconductor layer 306 are exposed. (FIG. 7 (15)).

(Used gas)
Inert gas: Nitrogen gas 98% by volume
Reactive gas: 2% by volume of oxygen gas
(Discharge conditions)
High frequency power supply: 13.56 MHz
Discharge output: 10 W / cm ²
Next, a silver fine particle dispersion (CCI-300 (silver content 20 mass%) manufactured by Cabot) is ejected from a piezo-type inkjet head, and printing is performed on the source electrode and drain electrode portions including the exposed regions of the semiconductor layer. gave. Next, heat treatment was performed at 200 ° C. for 30 minutes to form a source electrode 304 and a drain electrode 305 (FIG. 2 (14)). Each size was 40 μm wide, 100 μm long (channel width), and 100 nm thick, and the distance (channel length) between the source electrode 304 and the drain electrode 305 was 20 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 15 cm ² / Vs, the on / off ratio was 7 digits, and the threshold Vt was 4.3 V.

  A thin film transistor prepared in the same manner except that ITO fine particles are not disposed on the semiconductor precursor layer can be easily and uniformly converted into a semiconductor, and has a high mobility and a high on / off ratio.

Example 2
In Example 1, instead of placing ITO fine particles on the semiconductor precursor layer, NanoTek Powder ITO (particle size: 30 nm) manufactured by CI Kasei Co., Ltd. is 3% by mass, and the semiconductor precursor materials are indium nitrate and zinc nitrate. The ink mixed with an aqueous gallium nitrate solution was used as the ink.

  Here, as shown in the schematic cross-sectional view of FIG. 8, ITO fine particles are dispersed and contained in the precursor material thin film 306. Other than that, a thin film transistor was formed in the same manner.

Also for this thin film transistor, conversion into a semiconductor was easy and uniform, and a thin film transistor having a high mobility and a high on / off ratio was obtained as in Example 1. The mobility was 18 cm ² / Vs, the on / off ratio was 7 digits, and the threshold Vt was 5V.

Comparative Example 1
In Example 1, a thin film transistor was prepared in the same manner except that ITO fine particles were not arranged on the semiconductor precursor layer.

Similarly, the mobility and on / off ratio of the thin film transistor thus prepared were estimated. In Comparative Example 1, the mobility was 1.2 cm ² / Vs, the on / off ratio was 6 digits, and the threshold Vt was 6 V. The characteristics were inferior.

  As described above, a sample that is converted into a semiconductor layer by placing a material that absorbs microwaves and generates heat inside the precursor thin film or in contact with the precursor thin film has a higher conversion efficiency to the semiconductor layer. Recognize.

It is sectional drawing which shows the whole structure of the electrostatic suction type liquid discharge device used by this invention. It is a figure which shows the modification of the nozzle from which a shape differs. It is a schematic diagram which shows the electric potential distribution of the discharge hole vicinity of the nozzle by simulation. 2 is an exploded perspective view showing a schematic configuration of a multi-nozzle head 100. FIG. 2 is a cross-sectional view showing an internal configuration of a multi-nozzle head 100. FIG. It is a cross-sectional schematic diagram which shows an example of a structure of a thin-film transistor. It is a cross-sectional schematic diagram explaining each process of manufacture of the thin-film transistor of this invention. It is a cross-sectional schematic diagram which shows a mode that ITO fine particle was disperse | distributed and contained in the precursor material thin film.

Explanation of symbols

301 Substrate 302 Gate electrode 303 Gate insulating layer 304 Source electrode 305 Drain electrode 306 Semiconductor layer 306 ′ Precursor material thin film

Claims (6)

In a thin film transistor manufacturing method in which a precursor thin film of an oxide semiconductor is heated to be converted into an oxide semiconductor film, a material that absorbs microwaves and generates heat is disposed inside the precursor thin film or in contact with the precursor thin film. A method for manufacturing a thin film transistor, wherein the material is converted into an oxide semiconductor film by irradiation with microwaves. 2. The method of manufacturing a thin film transistor according to claim 1, wherein the oxide semiconductor precursor thin film is formed from a coating solution of a precursor solution or dispersion. 3. The method of manufacturing a thin film transistor according to claim 1, wherein the material that absorbs microwaves and generates heat is a metal oxide. 4. The method of manufacturing a thin film transistor according to claim 3, wherein the material that generates heat is a conductor. 5. The method of manufacturing a thin film transistor according to claim 3, wherein the heat-generating material is metal oxide fine particles. A thin film transistor produced using the method for producing a thin film transistor according to claim 1.

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