Method for producing coated conductive film and precursor solution for coated conductive film

Abstract

To reduce a sheet resistance of a formed conductive film, facilitate film lamination on the conductive film, easily form a fine pattern of the conductive film, and reduce an environmental load.SOLUTION: Patterned electrodes 106a', 106b' are formed by sequentially performing: an electrode patterning film formation processing step (B) of forming an electrode patterning film 105' made of a hydrophobic organic silane compound on a semiconductor layer 104'; a light irradiation processing step (C) of irradiating a prescribed region of the electrode patterning film 105' with deep ultraviolet to convert it into a hydrophilic region; a printing processing step (D) of performing processing such that a conductive oxide solution 160 is left only in the hydrophilic region by applying the conductive oxide solution 160 made of a 2-methoxyethanol / ethylene glycol mixed solution containing indium and tin on the electrode patterning film 105'; and an in-air calcination processing step (E) of performing heat processing on the conductive oxide solution 160 left only in the hydrophilic region.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a coating-type conductive film and a precursor solution for the coating-type conductive film, which are used in display devices such as organic electroluminescence (EL) elements (organic light emitting diodes (OLEDs)) and liquid crystal displays (LCDs), sensors for IoT devices, touch panels, solar cells, etc. More specifically, the present invention relates to a method for producing a coating-type conductive film that can be produced without using a vacuum device, and a precursor solution for the coating-type conductive film. [Background technology]

[0002] Conductive films are used in a wide range of fields, including as electrodes in display devices such as organic electroluminescent (EL) elements and LCDs, various sensors, touch panels, solar cells, etc., as well as functional conductive films for heat-reflecting electromagnetic wave shielding, antistatic properties, anti-fogging properties, etc. In particular, the transparent conductive film indium-tin oxide (ITO) is widely used due to its high visible light transmittance and electrical conductivity.

[0003] The ITO oxide is generally formed on a substrate using a vacuum film-forming method (including photolithography) such as sputtering or chemical vapor deposition. Conventionally, the production of such an ITO thin film involves evacuating the processing equipment, followed by a pattern-forming process including a number of steps, such as (A) in Figure 10, (B) photosensitive material coating and baking, (C) ultraviolet exposure, (D) development, (E) etching, and (F) photosensitive material film removal, to form an ITO thin film with the required pattern shape and complete the device.

[0004] However, when a vacuum film-forming method is used, a large-scale vacuum device is required, and the time and cost required to form a vacuum atmosphere are also required. Furthermore, the pattern formation process also requires a photosensitive resist material and further requires photolithography processing using an exposure device that uses ultraviolet light, which makes the process complicated and increases the burden on the environment. Therefore, there has been a demand for a method for manufacturing a conductive film that simplifies each patterning process in the production of a conductive film and can reduce the burden on the environment.

[0005] A technique for patterning a conductive film without using a vacuum film-forming method is known from Patent Document 1 below. The technology described in Patent Document 1 below forms a conductive film by using a coating method, and includes: a pattern resist formation step of forming a photoresist pattern that is soluble in an organic solvent and insoluble in water on a substrate; a transparent conductive film formation step of applying a coating liquid for forming a transparent conductive film, which is composed of conductive oxide particles, an inorganic binder, and a solvent, to the entire surface of the substrate on which the photoresist pattern has been formed, and then drying and curing the coating liquid to form a transparent conductive film mainly composed of conductive oxide particles and an inorganic binder matrix; and a transparent conductive film patterning step of developing the photoresist pattern by dissolving and removing it with an organic solvent, thereby removing the transparent conductive film formed on the photoresist pattern, thereby obtaining a transparent conductive pattern film, wherein the solvent of the coating liquid for forming a transparent conductive film is mainly composed of water or a water-alcohol mixed solution. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-232628 Summary of the Invention [Problem to be solved by the invention]

[0007] According to the technology described in Patent Document 1, a conductive film is formed by film formation using a coating solution, which eliminates the need for a large-scale vacuum device, but the pattern formation of the conductive film requires a complicated photolithography process. Furthermore, since a developing solution, which increases the environmental load, is used, it is difficult to reduce the environmental load.

[0008] The present invention has been made in view of the above circumstances, and has an object to provide a method for producing a coating-type conductive film and a precursor solution for a coating-type conductive film, which reduce the sheet resistance of the formed conductive film, facilitate the lamination of films on this conductive film, and enable the easy formation of a fine pattern of the conductive film while also reducing the environmental load. [Means for solving the problem]

[0009] The method for producing a coating-type conductive film according to the present invention comprises the steps of: an electrode patterning film forming step of forming an electrode patterning film made of a hydrophobic organic silane compound on the laminated body; an energy beam irradiation step of irradiating a predetermined region of the electrode patterning film where a conductive film is to be formed with energy beams, so as to make the predetermined region a hydrophilic region and to maintain a hydrophobic state in a region other than the predetermined region; a printing step of applying a coating type conductive oxide solution containing indium oxide and tin oxide and made by mixing 2-methoxyethanol and ethylene glycol onto the electrode patterning film so that the coating type conductive oxide solution remains only in the hydrophilic region; a conductive film forming step of subjecting the coating-type conductive oxide solution remaining only in the hydrophilic region to a heat treatment to form a patterned conductive film; Do the following in this order: stomach, In the coating type conductive oxide solution, the weight ratio of the 2-methoxyethanol in the mixture of the 2-methoxyethanol and the ethylene glycol is 50% or more. It is characterized by:

[0010] In addition, the ratio (In / (In+Sn)) of the content (weight) of indium In to the total content (weight) of indium In and tin Sn in the coating-type conductive oxide solution is preferably 0.87 or more and 0.95 or less, and more preferably 0.89 or more and 0.91 or less.

[0011] Also ,before It is more preferable that the weight ratio of 2-methoxyethanol is 50% or more and 80% or less.

[0012] The energy rays are preferably deep ultraviolet rays. It is also preferable that the difference in contact angle of the coating-type conductive oxide solution between the hydrophilic region and the hydrophobic region is set to be 30 degrees or more.

[0013] The precursor solution of the coating type conductive film according to the present invention is A precursor solution of a coating type conductive film to be coated on an electrode patterning film, It consists of a mixed solution of 2-methoxyethanol and ethylene glycol containing indium oxide and tin oxide, The ratio (In / (In+Sn)) of the content (weight) of indium In to the total content (weight) of indium In and tin Sn is 0.87 or more and 0.95 or less, and the weight proportion of 2-methoxyethanol in the mixed solution of 2-methoxyethanol and ethylene glycol is 50% or more. [Effects of the Invention]

[0014] According to the method for producing a coating-type conductive film of the present invention, a patterned conductive film can be easily formed by coating film formation without using an expensive vacuum device or a photolithography technique, so there is no need for complicated processing, and furthermore, there is no need for a development step using a developer solution, so that an increase in the environmental load can be suppressed.

[0015] Furthermore, by irradiating the electrode patterning film, which serves as the underlayer for the conductive film, with energy rays only in the conductive film formation area to perform hydrophilic treatment, the conductive film patterning process can be performed with high precision simultaneously with the printing process. In addition, the coating-type conductive film solution is made from a solution containing indium oxide and tin oxide, which is a mixture of 2-methoxyethanol and ethylene glycol, so the center of the cross-sectional shape of the conductive film can be prevented from collapsing significantly due to the coffee ring effect. This makes it possible to prevent an increase in sheet resistance, and makes it easy to stack other films on the conductive film.

[0016] Furthermore, the precursor solution for the coated conductive film according to the present invention contains indium (In) and tin (Sn), and the ratio of the content (by weight) of indium (In) to the total content (by weight) of indium (In) and tin (Sn) (In / (In+Sn)) is set to 0.87 or more and 0.95 or less, and the weight ratio of 2-methoxyethanol in the mixed solution of 2-methoxyethanol and ethylene glycol is set to 50% or more, so that the upper surface portion of the conductive film can be made nearly flat, which reliably prevents an increase in sheet resistance and makes it extremely easy to stack other films on the conductive film.

[0017] Furthermore, according to the method for producing a coating-type conductive film and the precursor solution for a coating-type conductive film of the present invention, a photolithography process is not used, so that a fine pattern of the conductive film can be easily formed, and further, since there is no need to use a developing solution or the like, the environmental burden can be reduced. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating a concept of a method for producing a coating-type conductive film according to an embodiment of the present invention. [Figure 2] 1 is a conceptual diagram illustrating a thin film transistor according to an embodiment of the present invention. [Figure 3] 1A to 1C are diagrams illustrating steps in a method for manufacturing a coating-type conductive film according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram illustrating the concept of a surface modification treatment in a coating-type conductive film manufacturing method according to an embodiment of the present invention. [Figure 5] 1 is a graph showing how the contact angle varies depending on the type of organic solvent. [Figure 6] 3A and 3B are diagrams illustrating how water is desorbed by baking an electrode in a method for producing a coating-type conductive film according to an embodiment of the present invention. [Figure 7] FIG. 1 is a schematic diagram showing the change in alkyl chains when irradiated with deep ultraviolet light in the presence of oxygen molecules. [Figure 8] FIG. 10 is a diagram showing how the cross-sectional shape of the formed patterned conductive film for evaluation differs depending on the composition ratio of the coating-type oxide solution in the examples of the present invention. [Figure 9] 1 is a graph showing the sheet resistance (kΩ / □) that changes depending on the metal composition ratio in the coating-type oxide solution in an example of the present invention. [Figure 10] 1A to 1C are process diagrams showing a conventional method for producing a coating-type conductive film. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a method for producing a coating-type conductive film and a precursor solution for a coating-type conductive film according to an embodiment of the present invention will be described with reference to the drawings.

[0020] <Concept of this embodiment> First, a method for producing a coating-type conductive film according to an embodiment of the present invention will be briefly described with reference to FIG. An electrode patterning film 105 made of a hydrophobic organic silane compound is applied onto a substrate 101 (which, if the product is a thin film transistor, already has a gate conductive film 102, a gate insulating film 103, and a semiconductor layer 104 formed thereon) (see FIG. 1(A) electrode patterning film formation process).

[0021] This electrode patterning film 105 is irradiated with deep ultraviolet rays 120 through a metal mask 110 having a predetermined pattern of through-holes, thereby forming hydrophilic regions on the electrode patterning film 105 (see the light irradiation process in FIG. 1(B)). At this time, the regions of the electrode patterning film 105 that are not irradiated with deep ultraviolet rays 120 remain hydrophobic regions. Therefore, by irradiating the electrode patterning film 105 with deep ultraviolet rays 120, the electrode patterning film 105 is divided into hydrophilic regions and the remaining hydrophobic regions.

[0022] Thereafter, the mask 110 is removed from the electrode patterning film 105, and a water-soluble coating material (conductive oxide solution; hereinafter the same) 130 is applied onto the electrode patterning film 105 using a coating means such as a blade coater 140. On the electrode patterning film 105, the coating material 130 wets the hydrophilic regions and can form the necessary conductive film, but the coating material 130 does not wet the hydrophobic regions and no conductive film is formed (see the printing process of the coating material in Figure 1(C)).

[0023] Furthermore, by subjecting the coating material 130 to a baking treatment, a predetermined conductive film can be dried (see baking treatment in FIG. 1(D)), thereby producing a conductive film patterned into a predetermined shape.

[0024] As described above, in this embodiment, only predetermined areas of the hydrophobic electrode patterning film 105 are hydrophilized to form areas that can be wetted with the water-soluble coating material 130, and then the coating material 130 is applied onto the electrode patterning film 105 to form a conductive film only in the predetermined areas. This allows the film formation process and pattern formation process in the conventional photoresist method to be carried out simultaneously, and a simple printing method can be constructed.

[0025] In particular, in this embodiment, the coating material 130 is made from a solution containing indium oxide and tin oxide, which is a mixture of 2-methoxyethanol and ethylene glycol, and this can prevent the center of the cross-sectional shape of the conductive film from sinking significantly due to the coffee ring effect, thereby preventing an increase in sheet resistance and making it easier to stack other films on the conductive film.

[0026] The coating-type conductive film manufacturing method according to the present embodiment described above can be used to form conductive films for a variety of applications, and can be suitably used, for example, to manufacture conductive films for the electrodes of thin film transistors. FIG. 2 shows a cross-sectional structure of a thin film transistor (TFT) in which a source electrode 106a and a drain electrode 106b are formed using the above-mentioned coating-type conductive film manufacturing method. That is, Figure 2 shows the cross-sectional structure of the TFT 100a, which is composed of a substrate 101 on which a gate electrode 102, a gate insulating film 103, a semiconductor layer 104 made of a coating-type oxide semiconductor, an electrode patterning film 105 made of an organic silane compound (composed of Si and alkyl chains), and a source electrode 106a and a drain electrode 106b are stacked.

[0027] The electrode patterning film 105 disposed under the source electrode 106a and the drain electrode 106b is made of an organosilane compound that has been subjected to a hydrophilic treatment. These electrodes 106a and 106b contain indium (In) and tin (Sn), and the ratio (In / (In+Sn)) of the content (weight) of indium (In) to the total content (weight) of indium (In) and tin (Sn) is set to be 0.87 or more and 0.95 or less. In this way, the source electrode 106a and the drain electrode 106b of the TFT 100a are formed using the above-mentioned coating-type conductive film manufacturing method, but instead of or in addition to these, the gate electrode 102 can be formed using the above-mentioned coating-type conductive film manufacturing method.

[0028] <Details of an example in which the coating-type conductive film manufacturing method according to this embodiment is applied to a thin film transistor manufacturing method> Next, a method for manufacturing a thin film transistor using the coating-type conductive film manufacturing method according to this embodiment and an example of a thin film transistor manufactured by the method will be specifically and in detail described below. First, the detailed structure of the manufactured thin film transistor will be described using the above-mentioned FIG. 2, and then the method for manufacturing the thin film transistor will be described in detail.

[0029] [Thin-film transistor] (Substrate 101) First, a substrate 101 is prepared. The substrate 101 is made of a cleaned plastic film, glass, or the like. Examples of plastic films that can be used include films made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polycarbonate (PC), nanocellulose, etc. When a plastic film is used, it is possible to reduce the weight compared to when a glass substrate is used, which increases portability and allows for the realization of flexible electronic devices that can be formed into desired shapes. As the glass, for example, alkali-free glass that does not contain alkali metal oxides, such as that used as substrate glass for display panels, and substrate glass for solar cells that has a function of preventing the diffusion of alkali metal oxides, can be suitably used.

[0030] (gate electrode 102) This gate electrode 102 may be formed by sputtering or photolithography (using conductive oxides such as ITO and IZO, as well as metals such as Au, Al, Ag, Cr, Mo, Ti, and Cu, and alloys thereof), but it is more preferable to form it by the same method as the coating-type conductive film manufacturing method for manufacturing the source electrode 106 a and the drain electrode 106 b described in the section on the concept of this embodiment above (in the latter case, an electrode patterning film will be disposed between the gate electrode 102 and the substrate 101 in FIG. 1(A)).

[0031] (Gate insulating film 103) A gate insulating film 103 is formed on the gate electrode 102 . Materials for forming the gate insulating film 103 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, barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, yttrium trioxide, etc. Among these, particularly preferred are silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide. Furthermore, inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

[0032] (Oxide semiconductor layer 104) An oxide semiconductor layer 104 is formed on the gate insulating film 103 . Furthermore, an inorganic acid salt is used as the precursor solution for the oxide semiconductor layer 104. More specifically, it is composed of at least one metal salt selected from the group consisting of nitrates, chlorides, sulfates, acetates, carbonates, and fluorides. Examples of the metal component include, but are not limited to, In-Ga-Zn-based oxides, In-Zn-based oxides, In-Sn-Zn-based oxides, and Zn-Sn-based oxides, which are known as oxide semiconductor materials.

[0033] Further, metal atom-containing compounds that form oxides applicable to oxide semiconductors can be used, such as metal salts, metal halide compounds, organometallic compounds, etc. Specific metal elements include indium, gallium, zinc, aluminum, strontium, zirconium, tin, cadmium, tantalum, yttrium, gadolinium, etc.

[0034] (Electrode patterning film 105) An electrode patterning film 105 is formed on the oxide semiconductor layer 104 . The electrode patterning film 105 is a film made of alkylsilane, alkyldisilazanes, etc., which is provided to effectively pattern the electrodes of thin film transistors. In the manufacturing process, when it is first applied, the film is entirely hydrophobic, but in the region where the electrode is to be formed (the region where the electrode is to be patterned), it is subsequently converted into a hydrophilic region by irradiation with deep ultraviolet light, etc.

[0035] Examples of alkylsilanes and alkyldisilazanes include alkoxysilane-based materials such as methyltriethoxysilane, ethyltriethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, octyltriethoxysilane, octadecyltriethoxysilane, trimethylethoxysilane, methyltrimethosilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, octyltrimethoxysilane, and octadecyltrimethoxysilane, and examples of alkyldisilazanes include compounds such as hexamethyldisilazane.

[0036] (Source electrode 106a and drain electrode 106b) On the electrode patterning film 105, a conductive film that constitutes a source electrode 106a and a drain electrode 106b is formed. The conductive film that constitutes the source electrode 106a and the drain electrode 106b is made of In--Sn oxide (ITO) that contains an indium-based metal and a tin-based metal.

[0037] [Method of manufacturing thin film transistors] Specific steps of the method for manufacturing a thin film transistor according to this embodiment (the description will begin with the step of forming the semiconductor layer 104') will be described in more detail with reference to FIGS. 3(A) to 3(E). (Formation process of semiconductor layer 104') First, as shown in FIG. 3(A), a coating type semiconductor layer (also referred to as a metal oxide semiconductor layer) 104' is formed on a silicon substrate 101' (which is formed by laminating a gate electrode 102 and a gate insulating film 103). The precursor solution for the semiconductor layer 104' uses an inorganic acid salt. More specifically, it is composed of at least one metal salt selected from the group consisting of nitrates, chlorides, sulfates, acetates, carbonates, and fluorides. Examples of the metal component include, but are not limited to, In-Ga-Zn-based oxides, In-Zn-based oxides, In-Sn-Zn-based oxides, and Zn-Sn-based oxides, which are known as oxide semiconductor materials.

[0038] More specifically, examples of the metal element include metal atom-containing compounds that form oxides that can be used in oxide semiconductors, such as metal salts, metal halide compounds, and organometallic compounds containing metal atoms. Specific examples of the metal element include indium, gallium, zinc, aluminum, strontium, zirconium, tin, cadmium, tantalum, yttrium, and gadolinium. The metal element-containing compound may also be a precursor solution containing dispersed finely divided metal oxides such as indium oxide (In2O3), zinc oxide (ZnO), indium-zinc oxide (IZO), indium-gallium-zinc oxide (IGZO), zinc-tin oxide (ZnSnO), and titanium oxide (TiO2).

[0039] These metal salts are dissolved in a solvent to prepare a precursor solution. The solvent to be used is not particularly limited as long as it can stably dissolve or disperse the various metal sources, and can be appropriately selected depending on the purpose. Examples include water, methanol, ethanol, propanol, 1-butanol, 1-propanol, 1-pentanol, ethylene glycol, 2-methoxyethanol, acetonitrile, toluene, xylene, and mesitylene. Furthermore, the solubility can be improved by making the solution acidic or basic. The obtained precursor solution is applied onto the substrate 101' to form a thin film of the precursor solution. The thickness of the semiconductor layer 104' can be adjusted by the concentration of the solution and the number of times the solution is applied. The coating method may be a film-forming method such as spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, or die coating.

[0040] Subsequently, the oxidation process is accelerated by performing a baking process, thereby obtaining the semiconductor layer 104'. The baking process in this case is carried out, for example, at a temperature of 150°C to 600°C for a time period ranging from 30 minutes to 6 hours. The calcination process can be carried out by natural drying, hot air, cold air, room temperature air drying, infrared light drying, or reduced pressure drying. Drying using a microwave heating device is also possible. Each calcination process can be carried out not only in air, but also in a gas atmosphere such as oxygen, nitrogen, or argon. To promote oxidation, the thin film can be irradiated with energy rays such as ultraviolet rays before or after calcination.

[0041] Examples of energy rays include excimer lamps, deuterium lamps, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, helium lamps, carbon arc lamps, cadmium lamps, and electrodeless discharge lamps. In particular, the use of a low-pressure mercury lamp can easily promote the conversion of the precursor film to an oxide film. Through the above processing, the semiconductor layer forming processing (semiconductor layer forming step) shown in FIG. 3(A) is completed.

[0042] Next, the process of forming the source electrode 106a and the drain electrode 106b, which is a characteristic feature of this embodiment, will be described in detail with reference to FIGS. 3(B) to 3(E). (Formation process of electrode patterning film 105') First, the process of forming an electrode patterning film (monomolecular film) will be described with reference to FIG. 3(B). That is, first, the surface of the film made of silicon and alkyl chains is modified. For the surface modification process, an organic silane compound having a hydrophobic substituent can be used, such as a material made of alkylsilane or alkyldisilazane. Examples of hydrophobic substituents include alkyl groups with alkyl chains such as methyl or ethyl groups, phenyl groups, and fluoroalkyl groups. These groups have groups that are reactive with hydroxyl groups and the like on the surfaces of the semiconductor layer 104' and the gate insulating film 103 (see Figure 2), chemically bonding to them to form a surface-modified film with Si-O-Si bonds.

[0043] Furthermore, the surface modification step in this embodiment will be described below as an example of a process in which the substrate 101' coated with the above-mentioned organosilane compound is placed in a sealed container and the organosilane compound is exposed to vapor in the atmosphere of the sealed container, but the surface modification process is not limited to these methods. That is, the surface modification treatment of the exposed surfaces of the semiconductor layer 104' and the gate insulating film 103 is carried out by placing an organic silane compound in a sealed container filled with a nitrogen atmosphere, exposing the exposed surfaces of the semiconductor layer 104' and the gate insulating film 103 to steam, removing the substrate 101' from the container, cleaning it with an alcohol-based organic solvent, and then heating the substrate 101' to perform a hydrophobic treatment.

[0044] Any container may be used as long as it is not corroded, decomposed, or adsorbed by the vapor, and specific examples include fluororesin containers, stainless steel containers, etc. The vaporization temperature can be raised from room temperature to 150°C, which is sufficient for surface modification treatment. A more preferable temperature is 100°C or higher and 150°C or lower, in terms of being able to eliminate the influence of water. The time of exposure to steam can be adjusted to a predetermined time between 1 minute and 3 hours. In particular, in the case of a trimethoxy-based organosilane compound, from the viewpoint of reactivity, sufficient surface modification can be achieved by heating at 110°C for 2 hours, filling the container with the steam, and exposing the exposed surfaces of the semiconductor layer 104' and the gate insulating film 103. A hot plate or an oven can be used as a heating means.

[0045] When the surface modification treatment of the electrode patterning film 105' made of an organic silane compound is performed using OTS (octadecyl-trimethoxy-silane) under the conditions described above, a hydrophobic treatment can be performed to make the water contact angle of the electrode patterning film 105' 100 degrees or more. Alternatively, a method of diluting a liquid of an organosilane compound with an alcohol-based organic solvent and directly coating the diluted solution containing the organosilane compound by spin coating or the like to form a film, or a method of immersing a substrate in the diluted solution to form a film, can be applied.

[0046] (Irradiation treatment with deep ultraviolet light, etc.) Next, the process of hydrophilizing a predetermined region (light irradiation process) will be described with reference to FIG. 3(C). The hydrophilization treatment can be carried out by irradiation with energy rays such as ultraviolet rays or lasers. An excimer lamp or excimer laser can be used as a light source for energy rays such as a laser. Here, irradiation with deep ultraviolet rays having an output light wavelength of 172 nm using an Xe2 excimer lamp as a light source for energy rays will be described as an example of hydrophilic treatment.

[0047] The organosilane compound formed on the substrate 101' has hydrophobic substituents formed on the outer surface. When deep ultraviolet light (ultraviolet light with a wavelength of 300 nm or less), especially vacuum ultraviolet light (ultraviolet light with a wavelength of 200 nm or less), is irradiated in an oxygen-containing environment, the oxygen is excited into highly reactive states such as active oxygen and ozone. These active oxygen react with the terminal alkyl groups (-CH3) of the surface modification film, for example, as shown in Figure 4, to oxidize and hydrophilize the surface, and hydroxyl groups (-OH), aldehyde groups (-CHO), carboxyl groups (-COOH), etc. are bonded to the outermost surface (the state transitions from Figure 4(a) to Figure 4(b) to Figure 4(c)).

[0048] Depending on the amount of deep ultraviolet light irradiated, the hydrophobic groups in the organosilane compound undergo intermittent reactions, causing the length of the alkyl chain to change. In other words, if irradiated for a long period of time, the hydrophobic groups are eventually etched away by oxidation. If such etching is performed excessively, the hydrophobic groups in the organosilane compound will disappear, and in a subsequent printing process using a coating solution, the coating solution will come into contact with the semiconductor layer 104' located below the organosilane compound. In other words, the solvent contained in the coating solution comes into direct contact with the semiconductor layer 104', which prevents the formation of a good interface and, in some cases, may even dissolve the semiconductor layer 104'. To prevent this from happening, it is important to ensure that the organosilane compound is distributed over the entire interface.

[0049] The UV irradiation time should be long enough to reduce the water contact angle by 30 degrees or more, so that the hydrophobicity of the surface modified by the organosilane compound is lost and hydrophilization is promoted. More preferably, the water contact angle should be 10 degrees or less, and in this case, a printing method that takes advantage of the difference in surface state between the hydrophobic and hydrophilic regions can be used to achieve sufficiently good electrode patterning (see Figure 6). On the other hand, excessive irradiation with ultraviolet light is undesirable because it etches the hydrophobic substituents contained in the organosilane compound, as described above.

[0050] (Printing process of coated electrodes) Next, the steps of the printing process for the coated electrode will be described with reference to FIG. As the printing process, a printing method using a general-purpose printer can be applied, such as a coating method including spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, and die coating, as well as an inkjet method. In the method of this embodiment, the wettability of the surface can be controlled down to the finest detail, so that a film can be formed in a self-aligned manner only in the required area, without using conventional patterning processes such as photolithography, and the pattern shape required for device application can be created. In other words, the source and drain electrodes required for transistors can be easily and satisfactorily formed. Note that FIG. 3(D) shows an example in which a conductive oxide solution (ITO solution) 160 is applied.

[0051] The conductive oxide solution (precursor solution for coating-type conductive film: the same applies hereinafter) 160 is a mixture of 2-methoxyethanol and ethylene glycol containing indium oxide and tin oxide. Here, the ratio (In / (In+Sn)) of the content (weight) of indium In to the total content (weight) of indium In and tin Sn is set to 0.87 or more and 0.95 or less, and further, the weight proportion of 2-methoxyethanol in the mixed solution of 2-methoxyethanol and ethylene glycol is set to 50% or more (main component). By setting it in this way, it is possible to prevent the central portion of the conductive film from sinking or from becoming extremely protruding, thereby preventing an increase in sheet resistance and making it easier to stack other films on the conductive film.

[0052] To further improve this effect, the ratio (In / (In+Sn)) is set to 0.89 or more and 0.91 or less. Similarly, the weight ratio of 2-methoxyethanol to the mixed solution of 2-methoxyethanol and ethylene glycol is set to 50% or more and 80% or less. By setting it in this way, it is possible to prevent the central part of the conductive film from sinking and to reliably prevent the central part from protruding significantly more than the edges, thereby reliably preventing an increase in sheet resistance and making it extremely easy to stack other films on the conductive film. By setting the lower limit of the weight ratio of 2-methoxyethanol to 60% or more, the above effects can be further improved.

[0053] If the conductive oxide solution 160 does not contain ethylene glycol, it is possible to obtain a coating shape in which the center is raised relative to the edges. However, if only 2-methoxyethanol is used, as shown in the upper part of Figure 8, the viscosity and boiling point of 2-methoxyethanol (ME) are low, so the amount of solvent evaporation is large, and a stable conductive film pattern cannot be obtained during printing.

[0054] Even when the surface coated with an organosilane compound having a hydrophobic alkyl group exhibits hydrophobicity with a water contact angle of 90 degrees or more, when an organic solvent is used, as shown in Figure 5, not all organic solvents can provide a high contact angle, and the selection of the solvent is an extremely important factor in generating a patterned conductive film with hydrophobic properties.

[0055] As shown in FIG. 5, even on a surface where the contact angle of water (used as a reference) is 100 degrees or more, common straight-chain alcohols (octanol, hexanol, butanol) result in a low contact angle of approximately 20 degrees or less. Therefore, the conductive oxide solution 160 according to this embodiment cannot be produced using such straight-chain alcohols. By using the conductive oxide solution 160 made of a mixed solution of 2-methoxyethanol and ethylene glycol according to this embodiment, a high contact angle of 50 degrees or more can be obtained, and the difference in the surface contact angle before and after the ultraviolet treatment can be made 30 degrees or more. In other words, by making the difference between the hydrophilic and hydrophobic (water-repellent) regions 30 degrees or more, the conductive film can be formed into any pattern shape.

[0056] The metal salts of indium and tin are composed of at least one metal salt selected from the group consisting of nitrates, chlorides, sulfates, acetates, carbonates, and fluorides. Furthermore, a patterned conductive film can be formed by using the above solution and performing a printing process with a simple printer, and the conductive film can have a shape in which the center is thicker than the edges, thereby suppressing the occurrence of the coffee ring effect.

[0057] (baking in air) Next, the step of baking in air after printing the coated electrode will be described with reference to FIG. In this air baking process, a pre-annealing process is performed to remove the solvent, followed by a baking process to promote oxidation of the source electrode 106a' and the drain electrode 106b', thereby forming these electrodes 106a', b'. The baking process in this case is performed, for example, at 150°C to 600°C for 30 minutes to 6 hours.

[0058] The firing process can be carried out by natural drying, hot air, cold air, or room temperature air drying, infrared drying, or reduced pressure drying. Microwave heating may also be used. Each firing process can be carried out not only in air but also in a gas atmosphere such as oxygen, nitrogen, or argon.

[0059] To further promote oxidation, the thin films of the electrodes 106a' and 106b' may be irradiated with energy rays such as ultraviolet rays before or after firing. Examples of energy rays include excimer lamps, deuterium lamps, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, helium lamps, carbon arc lamps, cadmium lamps, and electrodeless discharge lamps. In particular, the use of a low-pressure mercury lamp can easily promote the conversion of the precursor film to an oxide film.

[0060] The state of water being released by baking the electrodes 106a' and 106b' is shown in Fig. 6. That is, as drying by baking progresses, the state (electrode patterning film 105d) in which the oligomers form hydrogen bonds with the OH groups of the substrate changes to the state (electrode patterning film 105e) in which water is released and covalent bonds are formed, as shown in Fig. 6(b).

[0061] Furthermore, when the baking temperature is 250°C or higher, a process for removing the organic alkyl chains on the surface of the semiconductor layer 104' using a UV ozone device, oxygen plasma device, or the like can be performed after pre-annealing. This process for removing the organic alkyl chains can prevent degradation of device characteristics due to carbonization of the organic material on the surface of the semiconductor layer 104' caused by high-temperature treatment. This process can remove the organic silane compound from the back channel side of the semiconductor layer 104', as shown in FIG. 3(E), improving transistor characteristics.

[0062] Vacuum baking is effective for reducing the resistance of a patterned conductive film. After baking in the atmosphere, the sheet resistance can be reduced by baking the film under a vacuum of about 10 Pa at, for example, 150°C to 600°C for 30 minutes to 6 hours.

[0063] By forming a coating electrode using the process described above, a conductive film with a fine pattern can be formed on the semiconductor layer 104' using a simple printer. This eliminates the need for a large-scale film-forming device equipped with a vacuum system for sputtering or the like, and allows thin-film transistors required for displays and the like to be easily and quickly produced using inexpensive film-forming equipment. Furthermore, by setting the concentration of the metal salts of indium and tin to 0.01 mol / L-1 mol / L in the solution components, a conductive film with a thickness of approximately 30 to 200 nm, which is generally used as a transparent conductive film, can be formed after heat treatment. [Example]

[0064] In the following examples, the present invention will be described in more detail by evaluating samples of patterned conductive films prepared under different conditions. (Creating a patterned conductive film for evaluation) A low-resistivity silicon wafer with a 100 nm-thick thermal oxide film was used to create a patterned conductive film for evaluation according to the example, as shown in Fig. 2. The example will be described below with reference to the reference numerals in Fig. 2. That is, in this example, a low-resistivity silicon wafer with a thermal oxide film was used, in which a gate electrode 102 and a gate insulating film 103 were laminated on a substrate 101. Next, to form a coating-type semiconductor layer 104, a metal oxide precursor solution was applied onto the silicon wafer by spin coating.

[0065] Next, a surface modification treatment was performed using OTS (octadecyl-trimethoxy-silane). For the treatment, 1 ml of OTS solution and the substrate 101 having the semiconductor layer 104 were placed in a fluorine-based container, and the substrate 101 was heated in an oven at 105°C for 1 hour. Thereafter, the substrate 101 was washed with ethanol and isopropanol, and dried again at 80°C, thereby performing surface modification. The surface side of the substrate 101, which had been surface-modified in this manner, was made into a hydrophobic region showing a contact angle θ1 with water of 105° or more on both the semiconductor layer 104 and the gate insulating film 103. Specifically, as shown in Fig. 7, the contact angle θ1 with water in the hydrophobic region according to this example was set to 109°, and a non-wettable region was formed on the electrode patterning film 105.

[0066] Next, ultraviolet irradiation was performed using a 172 nm excimer lamp. The substrate 101 was set so that the ultraviolet irradiation atmosphere was atmospheric. A mask 110 having a conductive film pattern was set on the substrate 101 so that 172 nm deep ultraviolet rays 120 were irradiated to a predetermined region during irradiation. Deep ultraviolet rays 120 were irradiated through this mask 110 for 1 minute, and the irradiated region was made hydrophilic, with a contact angle with water of 10 degrees or less. Specifically, as shown in FIG. 7, the water contact angle θ2 in the hydrophilic region was set to 6 degrees, and a wettable region in a desired pattern was formed on the electrode patterning film 105.

[0067] After that, a printing process using each conductive oxide solution was carried out using a blade coater printer. The gap between the blade and the substrate surface was set to approximately 10 μm, and the coating was carried out using the blade. Subsequently, the conductive oxide solution was oxidized by baking at 400°C to form a conductive film for evaluation.

[0068] In order to investigate the solvent ratio dependency of the solution, seven samples were prepared as the first conductive film for evaluation by changing the ratio of 2-methoxyethanol and ethylene glycol that constituted the conductive oxide solution. That is, the solvent ratio of 2-methoxyethanol to ethylene glycol was 0:1 for Sample 1, 0.2:0.8 for Sample 2, 0.34:0.66 for Sample 3, 0.5:0.5 for Sample 4, 0.66:0.34 for Sample 5, 0.8:0.2 for Sample 6, and 1:0 for Sample 7. In Samples 1 to 7, the ratio (In / (In+Sn)) of the content (weight) of indium In to the total content (weight) of indium In and tin Sn was all 0.9.

[0069] In addition, in order to investigate the dependence of the metal content ratio of the solution, 14 samples were created as a second evaluation conductive film by changing the content ratio of indium (In) and tin (Sn) contained in the conductive oxide solution. That is, the ratio of the content (weight) of indium In to the total content (weight) of indium In and tin Sn (In / (In+Sn)) was 0.87, which was designated Sample A, the ratio was 0.88 which was designated Sample B, the ratio was 0.89 which was designated Sample C, the ratio was 0.90 which was designated Sample 5', the ratio was 0.91 which was designated Sample D, the ratio was 0.92 which was designated Sample E, the ratio was 0.93 which was designated Sample F, the ratio was 0.94 which was designated Sample G, the ratio was 0.95 which was designated Sample H, the ratio was 0.96 which was designated Sample I, the ratio was 0.97 which was designated Sample J, the ratio was 0.98 which was designated Sample K, the ratio was 0.99 which was designated Sample L, and the ratio was 1.00 which was designated Sample M. The sample 5' is identical to the sample 5 described above in both the solvent ratio and the metal content ratio of the solution. In addition, in the above Samples A to M and Sample 5', the weight ratio of 2-methoxyethanol to ethylene glycol constituting the conductive oxide solution was set to 0.66:0.34 in all cases.

[0070] (Evaluation of patterned conductive films) (First evaluation) The cross-sectional shape, printing stability and overall evaluation of the seven samples 1 to 7 prepared as described above are shown in Table 1 below. The cross-sectional shape analysis was performed using a film thickness step meter attached to the Dektak XT Stylus Profiler stylus profiling system. Shapes with raised edges and a concave center were given a NG rating, while shapes with a center that was more convex than the edges but extremely protruding, making them unsuitable for lamination, were also given a NG rating. Shapes suitable for lamination, positioned between these two NG-rated shapes, were given a OK rating. The cross-section analyzed was the longitudinal cross-section at the position indicated by the dashed line in the schematic diagram of the cross-section of the conductive film sample shown in the upper left diagram of Figure 8.

[0071] Here, printing stability means "the degree to which the solvent can be applied well to the substrate without evaporating too much." In other words, if the solvent is 2-methoxyethanol alone, which has a low boiling point, it dries easily and the concentration changes with repeated printing, making it impossible to obtain a stable shape and resulting in poor printing stability. On the other hand, even if ethylene glycol alone has a high boiling point, printing stability cannot be obtained due to concerns about the precipitation of metal salts. For these reasons, it is preferable to mix appropriate amounts of 2-methoxyethanol and ethylene glycol to obtain printing stability. When printing stability is obtained in this manner (as in the case of samples 4 to 6 below), an OK rating was given, and in all other cases an NG rating was given. Furthermore, if both the cross-sectional shape and the printing stability were evaluated as OK, an overall evaluation of OK was given.

[0072] [Table 1]

[0073] As a result of the analysis of the cross-sectional shape, Sample 1 has a concave shape with a sunken center as shown in Figure 8(a), which increases the sheet resistance and makes it difficult to stack other films on the conductive film. On the other hand, Sample 3 has a shape with an extremely protruding center as shown in Figure 8(b), which increases the sheet resistance, although not as much as the shape shown in Figure 8(a), and the stackability is not necessarily good.

[0074] In contrast, in Sample 5, the central portion is neither recessed nor extremely protruding, and is formed relatively flat, which prevents an increase in sheet resistance and makes it easy to stack other films on the conductive film. Therefore, a shape like Sample 5 is evaluated as having a good cross-sectional shape. As is clear from Table 1, samples 4 to 6 (bold, double underlined) were OK in both cross-sectional shape and printing stability, and received an overall rating of OK. This means that the rating can be considered good when the weight ratio of 2-methoxyethanol in the mixed solution of 2-methoxyethanol and ethylene glycol is 50 to 80% (provided that the ratio of the indium In content (weight) to the total content (weight) of indium In and tin Sn (In / (In+Sn)) = 0.9).

[0075] (Second evaluation) The sheet resistance (kΩ / □) and evaluation of the 14 samples A to M and sample 5′ prepared as described above are shown in Table 2 below. The sheet resistance was measured by a four-terminal method using a Loresta-GX MCP-T700 resistivity meter.

[0076] [Table 2]

[0077] As is clear from Table 2, samples B to G and sample 5' (bold, double underlined) had sheet resistances that were sufficiently small, at 10 kΩ / □ or less, and were rated as OK (the boundary value Fair is included in NG).This means that the rating can be determined as Good when the ratio of the indium In content (weight) to the total indium In and tin Sn content (weight) (In / (In+Sn)) is 0.88 to 0.94 (however, the ratio of 2-methoxyethanol to ethylene glycol is 0.66:0.34 in both cases).

[0078] The method for producing a coating-type conductive film and the precursor solution for the coating-type conductive film of the present invention are not limited to those described in the above embodiments, and various other modifications are possible. Furthermore, the product of the present invention (e.g., a thin film transistor) is not limited to the above embodiments, and it is also possible to have a configuration in which other layers are interposed between the layers shown in the embodiments. In addition, in the above embodiment, a coating method is used for the electrode patterning film and the conductive film, and it is preferable to use a coating method for forming each of the other layers as well, but if necessary, they may be formed using a vacuum method (including photolithography techniques) as appropriate.

[0079] Furthermore, the coating-type conductive film manufacturing method applied to the thin film transistor manufacturing method according to this embodiment may be used to manufacture at least one of the source / drain electrodes and the gate electrode, and the rest may be manufactured by a vacuum film forming method. Furthermore, the hydrophilization treatment is performed by irradiating the area on the electrode patterning film where the conductive film is to be formed with deep ultraviolet light, but the hydrophilization method is not limited to this and may also be performed by irradiating other energy rays.

[0080] Furthermore, in the first evaluation of the above-described examples, cross-sectional shapes such as those shown in FIG. 8(b), in which the central portion protrudes significantly more than the ends, are included in the evaluation of NG, as they do not necessarily provide a good effect. However, in the manufacturing method of the coat-type conductive film and the precursor solution of the coat-type conductive film of the present invention, even a shape such as that shown in FIG. 8(b) can be used well depending on the application, and therefore the range in which a conductive film of this shape can be manufactured is also included in the scope of the invention. [Explanation of symbols]

[0081] 100a, b Thin film transistor (TFT) 101, 101´, 301 board 101a´ Substrate heating section 102 gate electrode 103 Gate insulating film 104, 104' Semiconductor layer (metal oxide semiconductor layer) 105, 105', 105a-e Electrode patterning film 106a, 106a´ Source electrodes 106b, 106b´ drain electrodes 110, 110´ Mask 120 Deep UV 130, 330 Coating material 140 Blade Coater 160 Conductive oxide solution

Claims

1. an electrode patterning film forming step of forming an electrode patterning film made of a hydrophobic organic silane compound on the laminated body; an energy beam irradiation step of irradiating a predetermined region of the electrode patterning film where a conductive film is to be formed with energy beams, so as to make the predetermined region a hydrophilic region and to maintain a hydrophobic state in a region other than the predetermined region; a printing step of applying a coating type conductive oxide solution containing indium oxide and tin oxide and made by mixing 2-methoxyethanol and ethylene glycol onto the electrode patterning film so that the coating type conductive oxide solution remains only in the hydrophilic region; a conductive film forming step of subjecting the coating-type conductive oxide solution remaining only in the hydrophilic region to a heat treatment to form a patterned conductive film; Do the following in this order: The method for producing a coating type conductive film, wherein in the coating type conductive oxide solution, the weight ratio of 2-methoxyethanol in the mixed solution of 2-methoxyethanol and ethylene glycol is 50% or more.

2. 2. The method for producing a coating-type conductive film according to claim 1, wherein the ratio (In / (In+Sn)) of the content (weight) of indium In to the total content (weight) of indium In and tin Sn in the coating-type conductive oxide solution is 0.87 or more and 0.95 or less.

3. 3. The method for producing a coating-type conductive film according to claim 2, wherein the ratio (In / (In+Sn)) is 0.89 or more and 0.91 or less.

4. 2. The method for producing a coating-type conductive film according to claim 1, wherein the weight ratio of 2-methoxyethanol in the mixed solution of 2-methoxyethanol and ethylene glycol is 50% or more and 80% or less.

5. 5. The method for producing a coating-type conductive film according to claim 1, wherein the energy rays are deep ultraviolet rays.

6. 6. The method for producing a coating-type conductive film according to claim 1, wherein the difference in contact angle between the hydrophilic region and the hydrophobic region of the coating-type conductive oxide solution is set to be 30 degrees or more.

7. A precursor solution of a coating type conductive film to be coated on an electrode patterning film, It consists of a mixed solution of 2-methoxyethanol and ethylene glycol containing indium oxide and tin oxide, A precursor solution for a coating type conductive film, characterized in that the ratio of the content (weight) of indium In to the total content (weight) of indium In and tin Sn (In / (In+Sn)) is 0.87 or more and 0.95 or less, and the weight ratio of 2-methoxyethanol in the mixed solution of 2-methoxyethanol and ethylene glycol is 50% or more and 80% or less.

Images