JP6941538B2 - Manufacturing method of coated metal oxide film, coated metal oxide film and electronic device manufactured using it - Google Patents

Description

The present invention comprises, for example, coating metal oxidation constituting an electronic device such as a thin film transistor used for driving an organic EL (Electro-Luminescence) element (OLED (Organic Light Emitting Diode)) or LCD (Liquid Crystal Display). The present invention relates to a method for producing a material film, a coating type metal oxide film produced using the same, and an electronic device.

A thin film transistor (TFT) is used as a driving thin film transistor for a display device, and is an electronic device required for driving each pixel. TFTs that use metal oxides as semiconductor materials have been put to practical use in manufacturing by vacuum film forming methods such as sputtering, and are attracting attention. In particular, as a material, IGZO-based metal oxide TFTs using In-Ga-Zn as a metal species are generally ^{known to exhibit a relatively high mobility of 5-10 cm 2} / Vs or more, and are used. There is. However, when the vacuum film forming method is used, a large-scale vacuum device is required, and there are problems that the production efficiency is lowered and the load on the environment is increased. Another problem is that it is difficult to form a uniform thin film on a large area.

Therefore, a liquid phase coating type metal oxide that can easily form a film in the atmosphere without using a vacuum device and can cope with a large area has been actively studied.

By the way, when producing a coating type metal oxide, generally, a photosensitive photoresist is applied, exposure using ultraviolet rays, development with a developing solution, etching for removing unnecessary parts, and peeling of the photoresist. Each of the configured photoresist processes is performed in sequence. Since the photolithography process is composed of a plurality of complicated processes, a method for performing patterning more easily has been proposed.
As an example of simple patterning, there is a method such as direct patterning in which direct patterning is performed by reacting a directly coated metal oxide with ultraviolet rays or the like without using a photoresist. This method is also applied to metal oxides, and by adding a photosensitive component that reacts with ultraviolet rays to the precursor solution, it is possible to impart photosensitivity and perform patterning (Non-Patent Documents 1 and 2 below). (See) has been reported.

Further, there is known an inkjet method in which a solution is applied only to a necessary place by utilizing the feature of a solution, and the solution is heated and oxidized to obtain a metal oxide film.
However, in the forming method using the inkjet method, it is difficult to process the film shape control, which is an extremely important element. That is, it is difficult to form a uniform film because a coffee stain phenomenon occurs in which the central portion is dented and the edge portion is raised due to the difference in the drying speed of the coating film. In particular, when the area is increased, the shape variation becomes large, which is directly linked to the mobility in the TFT, and stable electrical characteristics cannot be obtained. Therefore, as a method for uniformly forming the film, control of the film shape by humidity control (see, for example, Non-Patent Document 3 below), a manufacturing method of applying the film to a heated substrate (see, for example, Patent Document 1 below), etc. A method of correction is known.

Republished Patent WO 2015/182679

HS Lim, YS Rim, and HJ Kim, “Photoresist-Free Fully Self-Patterned Transparent Amorphous Oxide Thin-Film Transistors Obtained by Sol-Gel Process,” Sci. Rep., Vol. 4, no. 1, (2014). ) HJ Kim, Y. Kim, SP Park, D. Kim, N. Kim, JS Choi, and HJ Kim, “14-4L: Late-News Paper: Self-Pattern Process of InZnO Thin-Film Transistors using Photosensitive Precursors,” SID Symposium Digest of Technical Papers, vol. 48, no. 1, pp. 180-182, (2017).) K. Fukuda, T. Sekine, D. Kumaki, and S. Tokito, “Profile Control of Inkjet Printed Silver Electrodes and Their Application to Organic Transistors,” ACS Applied Materials & Interfaces, vol. 5, no. 9, pp. 3916 -3920, (2013)

However, even when the film is formed into a uniform film by using the above-mentioned method, it cannot always be said that the film forming process is sufficiently simplified.
Further, when a photosensitive component is added to the metal oxide precursor, when the photosensitive component is a metal oxide, it is not sufficiently oxidized and decomposed and behaves as a residual impurity, which causes a factor of lowering the performance.
Therefore, the methods proposed so far are simple and have good performance.
There are not enough methods to form. And it is difficult especially when trying to increase the area.

The present invention has been made to solve the above problems, and when a metal oxide film is produced by a coating method, a metal oxide film having a uniform shape can be formed by a simpler manufacturing process. It is an object of the present invention to provide a method for producing a coated metal oxide film capable of increasing the area, a coated metal oxide film produced by using the method, and an electronic device.

To achieve the above objectives
The method for producing a coating type metal oxide film of the present invention is
A precursor solution generation step of dissolving an inorganic acid salt composed of a metal salt in a solvent in which an aqueous solvent occupies a weight of 50% or more to produce a precursor solution of a water-soluble metal oxide.
A precursor coating step of applying the precursor solution produced in the precursor solution generation step onto a predetermined object to be coated, and a precursor coating step.
A soft annealing step of drying the object to be coated to which the precursor solution has been applied in the precursor coating step, and a soft annealing step.
An energy ray is irradiated to a predetermined region of the precursor film of the metal oxide applied on the object to be coated, which has been dried in the soft annealing step , and the predetermined region is oxidized to form a metal oxide film. Metal oxide film formation process and
Wherein not the metal oxide film forming step odor Te before Symbol metal oxide film, the metal oxide of the precursor film are removed in the region other than the predetermined region, an etching step of performing direct patterning,
It is characterized by having.

As for the solvent, it is preferable that the aqueous solvent occupies 80% or more by weight.
It is preferable that the energy ray has a strength that allows the aqueous solvent to generate active oxygen species.
In the etching step, it is preferable to perform etching with a solution containing an organic acid.
In this case, the organic acid is preferably a hydroxycarbonate-based organic acid having a chelating effect of forming a metal ligand complex with respect to metal ions.

Further, the coating type metal oxide film of the present invention is characterized in that it is produced by any of the above-mentioned methods for producing a coating type metal oxide film.

Further, the electronic device of the present invention is characterized in that it is manufactured by any of the above-mentioned coating type metal oxide film manufacturing methods.
In this case, the electronic device can be a thin film transistor.

According to the method for producing a coated metal oxide film of the present invention, an inorganic acid salt composed of a metal salt is dissolved in a solvent containing water as a main component to generate a precursor solution of a water-soluble metal oxide. Since the generated water-soluble metal oxide precursor solution is applied onto a predetermined object to be coated and the water-soluble metal oxide film is irradiated with energy rays, the water-soluble metal oxide precursor solution is used. When water, which is the main component of the solvent, is irradiated with energy rays, it causes a water splitting reaction to generate active oxygen species such as oxygen radicals.

The generated reactive oxygen species oxidizes the desired region of the metal oxide film precursor, and then the unoxidized region is removed by etching, so that the desired shape irradiated with energy rays is exactly the same. Moreover, the pattern of the metal oxide film can be easily formed.
As a result, a metal oxide film having no variation in shape can be formed by a simpler manufacturing process.

Further, since the electronic device is manufactured by using the metal oxide film, it is possible to manufacture an electronic device having characteristics that are inexpensive and have no variation by a simpler manufacturing process.

It is the schematic which shows each step (A) of the manufacturing method of the coating type metal oxide film which concerns on embodiment of this invention, and each step (B) by the prior art method. It is a figure which conceptually shows the operation in the energy ray irradiation step (a) and the etching step (b) in the embodiment shown in FIG. It is the schematic which shows the TFT element composition for evaluation which concerns on Example. A group of TFT elements regularly arranged and created according to the present embodiment (before the source and drain electrodes are attached) (a) and one created TFT element (after the source and drain electrodes are attached) (b). ) Is a photograph showing the situation. It is a figure which shows the state of the change of the pattern with the change ((a)-(f)) of the etching time in the metal oxide film pattern-formed by this embodiment. It is a graph which shows the gate voltage-drain current characteristic of the TFT formed by using an Example. It is a graph which shows the change of mobility according to the change of the ratio of water solvent in a solvent. It is a laminated cross-sectional view (without etching stop layer) which shows the structure of a general TFT element. It is a laminated cross-sectional view (with an etching stop layer) which shows the structure of a general TFT element.

Hereinafter, a method for producing a coated metal oxide film according to an embodiment of the present invention, a coated metal oxide film produced by using the method, and an electronic device will be described.

<< Embodiment >>
Hereinafter, the method for producing the coated metal oxide film according to the present embodiment will be described, but as a premise thereof, the cross-sectional structure of the TFT in which the coated metal oxide film is laminated as the semiconductor layer (channel layer) will be briefly described. explain.
FIG. 8 shows a generally known cross-sectional structure of a TFT (first example: no etching stop layer).
The gate electrode 102, the gate insulating film 103, the semiconductor layer 104 made of a coated oxide semiconductor, and the source / drain electrode 106 are laminated on the substrate 101.
FIG. 9 also shows a generally known cross-sectional structure of a TFT (second example: with an etching stop layer).
On the substrate 201, a gate electrode 202, a gate insulating film 203, a semiconductor layer 204 made of a coated oxide semiconductor, an etching stop layer 205 for protecting the semiconductor layer 204 from etching, and a source / drain The electrodes 206 are laminated.

The thin film transistor (TFT) according to the electronic device of the present embodiment will be described below. Further, in this description, the method for producing the coating type metal oxide film of the present embodiment and the coating type metal oxide film produced by this production method will be described in detail.
As the layer of the TFT, it is assumed that the layer is configured as shown in FIG.
That is, the gate electrode 102, the gate insulating film 103, the coated semiconductor layer 104, and the source / drain electrode 106 are sequentially formed on the substrate 101. The semiconductor layer 104 is coated with a water-soluble metal oxide precursor solution, and a metal oxide film is formed by the subsequent treatment.

The method for producing a coating type metal oxide film according to the present embodiment is not limited to the method for producing a coating type metal oxide film for a TFT, and is not limited to the method for producing a coating type metal oxide film for various other electronic devices. It can be applied to the manufacturing method of. Further, it can be applied not only to the production of oxides exhibiting semiconductor characteristics, but also to the production methods of oxides exhibiting conductive characteristics used for electrodes and the like, and oxides exhibiting insulating characteristics.

(A) First, the material for forming the substrate 101 is washed, a barrier layer or a flattening layer (inorganic thin film or organic thin film) is formed on the surface by sputtering or the like, and a gate electrode (for example, gold, titanium, chromium, aluminum, etc.) is formed. (Molybdenum or an alloy thereof, a laminated film, etc.) 102 is formed, and patterning is performed so as to obtain a desired shape. Photolithography (microfabrication technology by ultraviolet exposure) is used for forming fine patterns.

(B) Next, the gate insulating film 103 is formed. The gate insulating film 103 is preferably composed of an inorganic oxide film having a high relative permittivity. Examples of the inorganic oxide include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide and the like. Inorganic nitrides such as silicon nitride and aluminum nitride can also be used.

(C) Next, regarding the step of forming the semiconductor layer 104, which forms the shape of the semiconductor layer 104 using the water-soluble metal oxide precursor, the precursor that produces the precursor solution of the water-soluble metal oxide is used as the pre-step. Perform a solution generation step.

Next, as shown in FIG. 1 (A), the precursor solution coating step (a), the soft annealing step (b), the energy ray irradiation step (c), and the etching step (d) are performed in this order.

First, in the above-mentioned step of producing a precursor solution of a metal oxide, an inorganic acid salt is used as the precursor solution. More specifically, it is composed of at least one metal salt of nitrate, chloride salt, sulfate, acetate, carbonate and fluoride salt.
Examples of the composition of the metal component include 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. Of course, it is not limited to this.
More specifically, a metal atom-containing compound that forms an oxide that can be applied to an oxide semiconductor can be mentioned, and a metal salt, a metal halide compound, an organic metal compound, and the like containing a metal atom can be mentioned. .. Specific metal elements include indium, gallium, zinc, aluminum, strontium, zirconium, tin and the like.

In addition, as metal element-containing compounds, indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), indium-zinc oxide (IZO), indium-gallium-zinc oxide (IGZO), zinc-tin oxide ( It may be a precursor solution in which a metal oxide such as ZnSnO) or titanium oxide (TiO _{2) is atomized and dispersed.}

Dissolve these metal salts in a solvent to prepare a precursor solution. Water is the main component of the solvent to be dissolved. Solvents such as ethanol, propanol, ethylene glycol, 2-methoxyethanol, and acetonitrile can be mixed and used to improve the coatability. Furthermore, the solubility can be improved by changing Ph to acidic or basic.

As for the ratio of water, it is preferable that the solvent ratio is 100% water solvent, but an organic solvent can be mixed in order to improve the coatability. In that case, even when the solvent ratio of water is reduced to a ratio of 50%, the patterning property and the electrical characteristics as an electronic device can be reached to a predetermined reference value. That is, the characteristics of patterning property and mobility in TFT may be as long as the content of the aqueous solvent is 50% or more, and it is possible to form a metal oxide film by photopatterning according to the present invention. The ratio of the water solvent in the coating type precursor solution is more preferably 80% or more, and further, as described above, the ratio of the water solvent is preferably 100%.

The precursor solution is prepared by weighing the metal salt concentration so that the solution concentration is in the range of 0.01 mol / L to 1 mol / L, and stirring and dissolving in the solution. More preferably, the solution concentration is in the range of 0.1 mol / L to 0.5 mol / L.
Next, in the precursor solution coating step (a) described above, the precursor solution produced as described above is coated on the upper surface of the base material (specifically, the substrate, the gate electrode, and the gate insulating film) 101. By doing so, a thin film of the precursor solution is formed. The thickness of the coating type semiconductor layer can be adjusted by the concentration of the solution and by the number of times the solution is applied.

The thickness is preferably 1 nm to 100 nm. As a coating method, a printing method such as a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, a roll coating method, a bar coating method, or a die coating method can be used.

Next, the soft annealing (drying treatment such as low temperature drying) step (b) is performed.
The soft annealing step is also called a gentle drying step. Specifically, since the semiconductor layer (metal oxide film) 104 contains a large amount of water, water, which is the main component of the solvent, is used. This step is performed for the purpose of leaving the residue, and is a step performed to ensure the effectiveness of the oxidation treatment of the pattern formed in the energy ray irradiation step performed thereafter.
As the soft annealing treatment, low temperature drying, natural drying, vacuum drying, hot air / cold air / room temperature air drying, infrared light drying and the like can be used. It may be dried by a reaction by a heating device using microwaves.

Next, the energy ray irradiation step (c) is performed.
In this energy ray irradiation step, the metal oxide film is patterned by irradiating the moisture remaining in the metal oxide film in the oxide semiconductor layer (metal oxide film) 104 with energy rays such as ultraviolet rays. Can be easily performed.
Hereinafter, the action performed on the oxide semiconductor layer 104 in this energy ray irradiation step (c) will be described with reference to FIG.
In this energy ray irradiation step, the water molecules remaining in the membrane are irradiated with energy rays to cause the following photochemical reaction.
H ₂ O + hν → HO ・ + ・ H
As a result, hydroxyl radical (OH ·), which is an active oxygen species, is generated.

The wavelength of the ultraviolet rays irradiated here is preferably 180 to 400 nm. Examples thereof include ultraviolet rays from excima lamps, heavy hydrogen lamps, low pressure mercury lamps, high pressure mercury lamps, ultrahigh pressure mercury lamps, metal halide lamps, helium lamps, carbon arc lamps, cadmium lamps, electrodeless discharge lamps and the like. It is more preferable to use a low-pressure mercury lamp because the conversion from the precursor film to the oxide film can be easily performed. At this time, by irradiating through a light-shielding mask having a pattern, selective oxidation treatment becomes possible, and a pattern can be easily formed.

Finally, an etching step (d) is performed to remove the precursor film in the region that has not been oxidized (for example, the region that is not irradiated with energy rays by the mask).
In the etching step, it is preferable to use an etching solution that causes less damage to the metal oxide film, and good etching can be performed by setting the pH in the range of 2 or more and 4 or less.

Specifically, acetic acid, propionic acid, oxalic acid, succinic acid, citric acid, malonic acid, malic acid, tartaric acid, oxalic acid, formic acid, glycolic acid, maleic acid, etc., whose concentrations have been adjusted appropriately, are generally known. Any organic acid may be used.
More preferably, a hydroxycarbonate-based organic acid having a hydroxy group and a carboxylic acid group, which has a chelating effect of forming a metal ligand complex with respect to a metal ion, is desirable. According to this, it is easily adsorbed by the metal ion component, desirable etching characteristics can be obtained, and the influence on the oxide layer left as a pattern can be reduced. From this point of view, among the above organic acids, citric acid, glycolic acid, tartaric acid, malic acid and the like are preferable.

A PH adjuster can be appropriately contained in the solvent, if necessary, and the etching solution can be easily adjusted to a pH range of 2 or more and 4 or less with such a PH adjuster.
Specifically, as such a PH adjuster, ammonia, potassium hydroxide, tetramethylammonium hydroxide and the like can be used.

By sufficiently rinsing with pure water or the like after etching, the metal oxide film can be patterned only in the region selectively irradiated in the irradiation step.
After that, the patterned metal oxide film is further subjected to a firing treatment to promote the oxidation treatment, and a semiconductor layer of the TFT having further excellent characteristics can be obtained. The firing treatment in this case is, for example, a time in the range of 30 minutes to 6 hours at 150 ° C. to 400 ° C.
In the firing treatment at this time, natural drying, hot air / cold air / room temperature air drying, infrared light drying, vacuum drying and the like can be used. It may be dried by a heating device using microwaves. Each firing process can be performed not only in the atmosphere but also in a gas atmosphere such as oxygen, nitrogen and argon.

(D) When the formation of the oxide semiconductor layer 104 is completed in this way, a step of forming the source / drain electrode 106 on the oxide semiconductor layer 104 as shown in FIG. 8 is performed.

When the source / drain electrode 106 is patterned by wet etching, an etching stop layer (corresponding to the etching stop layer 205 in FIG. 9) may be formed in order to alleviate damage to the oxide semiconductor layer 104. By doing so, deterioration of semiconductor characteristics can be suppressed. As the etching stop layer, the same material as the gate insulating film 103 can be applied.
As the material of the source / drain electrode 106, transparent electrodes such as ITO and IZO, metal electrodes such as Al, Ag, Cr, Mo and Ti, and alloys thereof can be used. By laminating two or more layers, the contact resistance can be reduced and the adhesion can be improved.

As the etching solution, various etching solutions such as a mixed acid of phosphoric acid, acetic acid and nitric acid (PAN etchant) and oxalic acid can be used.
Further, in the source / drain electrode 106 and the gate electrode 102 described above, the oxide composition is made of a highly conductive material, so that a conductive film related to the oxide is formed by using a water-soluble metal oxide precursor. It is also possible. The precursor solution for forming the conductive film here is an inorganic acid salt. More specifically, it is composed of at least one metal salt of nitrate, chloride salt, sulfate, acetate, carbonate and fluoride salt.

Examples of the highly conductive material include metal atom-containing compounds that form oxides (oxide conductor materials) that exhibit conductor properties by oxidation, and include metal atoms, metal salts, metal halide compounds, and organic metals. Compounds and the like can be mentioned. Specific metal elements include indium, gallium, zinc, tin and the like.
Specific examples of the oxide conductor material include, but are not limited to, In-Sn-based oxides, Ga-Zn-based oxides, In-Zn-based oxides, and Zn-based oxides.
By irradiating the moisture remaining in the film with energy rays such as ultraviolet rays by using the same method as the method produced in the semiconductor layer, the metal oxide film can be easily patterned.
Further, by using the same method and setting the composition of the metal element in the oxide to, for example, Zr, Hf, Al, etc., it is possible to form a functional oxide applicable to an insulating film having high dielectric properties. can.

As described above, a metal oxide film having a pattern required for an electronic device can be formed by a simple method, and as a result, an inexpensive electronic device using a metal oxide having high characteristics can be provided.

In the process of forming the semiconductor layer according to the prior art, as shown in FIG. 1 (B), a precursor solution coating step (a), an annealing step (b), a photolithography coating step (c), and an energy ray irradiation step ( A photolithography process in which d), a developing process (e), an etching process (f), and a film removing process (g) are performed in this order is adopted, and the number of processes is larger than that of the manufacturing method of the present embodiment. It is clear that it is complicated.
In the present embodiment, as described above, the solvent containing water as a main component is irradiated with energy rays, and the metal oxide film is oxidized by the generated active oxygen species such as hydroxyl radicals, which is complicated. The troublesome photolithography process can be omitted, and the process can be simplified.

Here, each of the above-described configurations of the TFT, which is the electronic device of the present embodiment, will be supplemented.
That is, the above-mentioned substrates 101 and 201 are made of, for example, quartz, glass, or a plastic film, but by being made of a flexible plastic film, they can be applied to a flexible display (for example, an organic EL display). .. Examples of the plastic film include PET, PEN, polyimide, and the like, and in some cases, a metal plate such as stainless steel can be used.

The film thickness of the gate electrodes 102 and 202 is, for example, 10 to 100 nm.

Further, as a material for forming the gate insulating films 103 and 203, in addition to the above-mentioned configurations, tin oxide, vanadium oxide, barium titanate strontium, barium titanate zodiac, lead titanate titanate, lead lanthanum titanate, and titanic acid Examples thereof include strontium, barium titanate, barium magnesium fluoride, bismuth titanate, strontium titanate bismuth, strontium titanate bismuth, bismuth niobate tantanate, and trioxide ittrium.
The film thickness is, for example, 100 nm to 300 nm.

Hereinafter, the method for producing the coating type metal oxide film of the present invention, the coating type metal oxide film produced by using the same, and the electronic device will be described in more detail with reference to Examples.

As the evaluation TFT according to this example, a low resistance silicon wafer with a thermal oxide film having a thickness of 100 nm was used, and a TFT as shown in FIG. 3 was prepared.
That is, in this embodiment, a low resistance silicon wafer with a thermal oxide film was used as the substrate 1, the gate electrode 2, and the gate insulating film 3. Next, in order to form the coating type semiconductor film 4, a metal oxide precursor thin film was coated on a silicon wafer by a spin coating method.

その後、室温にて、6時間撹拌することで、各金属酸化物が完全に溶解した状態の前駆
体溶液を作成した。 Examples of the water-soluble metal oxide precursor solution for forming the metal oxide film (Example 1) include indium nitrate hydrate (In (NO ₃ ) ₃ · xH ₂ O Aldrich) and gallium nitrate hydrate (manufactured by O Aldrich). Ga (NO ₃ ) ₃ · xH ₂ O Aldrich) and zinc nitrate hydrate (Zn (NO ₃ ) ₂ · xH ₂ O Aldrich) were weighed in the molar ratio shown in Table 1 below and dissolved in pure water. Then, a coated semiconductor precursor solution shown in Table 1 below was prepared, in which water was the main component of the solvent (in Example 1, the content of the aqueous solvent in the total solvent was 100%). At this time, the concentration of the sample was 0.3 mol / L.

Then, the mixture was stirred at room temperature for 6 hours to prepare a precursor solution in which each metal oxide was completely dissolved.

Subsequently, the precursor solution thus prepared is applied onto a silicon wafer by a spin coating method, and low-temperature dried on a hot plate at a low temperature of 80 ° C. so that water, which is the main component of the solvent, remains in the film. I let you.

After that, a mask having a pattern shape of the coating type semiconductor layer 4 formed on the low resistance silicon wafer (1, 2, 3) with a thermal oxide film is set on the coated metal oxide front skeleton film. A low-pressure mercury lamp was used to irradiate the metal oxide precursor film with ultraviolet rays through this mask for 10 minutes. The main UV wavelengths were 185 nm and 254 nm. As a result, the oxidation treatment process of the metal oxide precursor film was carried out. At this time, the water remaining in the forearm film was irradiated with ultraviolet rays to partially oxidize the radicalized hydroxyl radicals to prepare a metal oxide film.

Then, an etching treatment is performed with a 1% by weight solution of citric acid, which is a hydroxycarbonate-based organic acid, to remove the metal oxide forearm film in the ultraviolet non-irradiated region which has not been subjected to the oxidation treatment. It will be. In this etching treatment, it was applied for 30 seconds.
As described above, a metal oxide film having a desired pattern was formed.

Then, the metal oxide film was fired in an air oven at 300 degrees for 1 hour to form the semiconductor layer 4.
The film thickness of the semiconductor layer 4 at this time was 15 nm.
Subsequently, masking was performed with a metal mask having a predetermined shape, and source / drain electrodes 6a and 6b were formed by a DC sputtering method using molybdenum.
As a result, a TFT for evaluation was created.

FIG. 4A shows a group of TFTs in which a large number of evaluation TFTs created as described above are arranged, and FIG. 4B shows a photopatterned region (metal oxide) in one TFT. It is a schematic diagram which shows what kind of positional relationship each region of a source electrode 6a and a drain electrode 6b is superposed with respect to a region).
In the etching process for forming the pattern, the etching resistance in the UV region irradiated with ultraviolet rays is different from that in the region not irradiated with ultraviolet rays.

Of FIGS. 5 (a) to 5 (f), (a) is not etched after UV irradiation, (b) is not etched after UV irradiation, and (c) is etched after UV irradiation for 10 seconds. (D) is the etching treatment for 15 seconds after the ultraviolet irradiation, (e) is the etching treatment for 30 seconds after the ultraviolet irradiation, and (f) is the etching treatment for 45 seconds after the ultraviolet irradiation. It shows the residual state of the metal oxide film.
In FIGS. 5 (c) to 5 (f) showing the states of each pattern when the etching treatment time was changed after the irradiation with ultraviolet rays, an island-shaped pattern could be formed. In particular, in a state where etching treatment was performed for 15 seconds after irradiation with ultraviolet rays (see FIG. 5D), a uniform island-like pattern could be formed.

The semiconductor characteristics (gate voltage-drain current characteristics) were measured with respect to the obtained TFTs of the above examples. The result is shown in FIG. According to the characteristics shown in FIG. 6, the gate voltage rises from a state of substantially 0, and hysteresis is hardly observed, so that it is clear that good performance is exhibited. Further, although not shown in FIG. 6, even if the same measurement was repeated, the variation was extremely small, and good characteristics were obtained in each case, so that it was confirmed that there was reproducibility.

^{Table 2 below shows the mobility (cm 2} / Vs), Ion / Ioff ratio, and sub-threshold value (V / decade) in the TFT of the above embodiment. As shown in Table 2, in the TFT of this embodiment, the mobility is ^{5.0 (cm 2 / Vs),} Ion / Ioff ratio is 10 ^7, sub-threshold value is 0.37 ( V / decade), and good results were obtained in both cases.

<About the content of water solvent>
In Example 1 described above, the content of the aqueous solvent with respect to all the solvents was set to 100%. However, in the present invention, it is possible to mix an organic solvent in order to improve the coatability while using water as the main solvent. Even in that case, it is necessary that the content of the water solvent (weight ratio of the water solvent in the total solvent) is 50% or more in order to secure the mobility and good patternability in the TFT.
Hereinafter, the content of this aqueous solvent will be verified. First, the precursor solutions of Examples 2 and 3 and Comparative Examples 1 and 2 were prepared by using a mixture of water and an organic solvent as shown in Table 3 below as a solvent. The other preparation methods of Examples 2 and 3 and Comparative Examples 1 and 2 were the same as those of Example 1 described above.

^{FIG. 7 shows the change in mobility (cm 2} / Vs) in TFT with respect to the change in the content of water solvent (ratio of water solvent in all solvents).
As shown in FIG. 7, in the mobility in the TFT, deterioration of the characteristics was observed as the content of the aqueous solvent decreased. ^{Assuming that 0.5 cm 2} / Vs, which is the mobility of amorphous silicon, can be secured as a characteristic of TFT, it is a condition that the content of water solvent is 50% or more. That is, the content of the aqueous solvent is 100% (Example 1), 80% (Example 2) and 50% (Example 3), and the mobility (cm ² / Vs) is 5.0 and 1.2, respectively. , And 0.5, so that if the content of the aqueous solvent in the total solvent is 50% or more, the numerical condition regarding the mobility in the TFT can be satisfied. Further, when the content of the aqueous solvent is 50% or more, the patterning property (the shape of the pattern when forming the metal oxide film by using optical patterning) is also good.

On the other hand, when the content of the aqueous solvent is less than 50%, the mobility (cm ² / Vs) does not reach 0.5, and when the content of the aqueous solvent is 20% (Comparative Example 1) and 0% (Comparative Example 2), the mobility (cm 2 / Vs) does not reach 0.5. The mobility (cm ² / Vs) was 0.3.

Considering the patterning property and the good mobility in TFT, the content of the aqueous solvent in the solvent is preferably 80% or more (Examples 1 and 2).
Of course, when the mobility (cm ² / Vs) and the goodness of patterning in the TFT are given the highest priority, the content of the aqueous solvent in the solvent is preferably 100% (Example 1).

<About etching solution>
In Examples 1 to 3 described above, the etching solution used in the etching treatment was a 1% by weight solution of citric acid, which is a hydroxycarbonate-based organic acid.
In this etching process, the mobility and patterning property change depending on the etching solution, so it was verified below what kind of solution is excellent as the etching solution.
As shown in Table 4, the verified etching solutions were, in addition to Example 1, a solution of 1% by weight of glycolic acid, which is a hydroxycarbonate-based organic acid (Example 4), and 0 of formic acid, which is an organic acid. .1% by weight solution (Example 5), 1% by weight solution of acetic acid which is an organic acid (Example 6), and 0.01% by weight solution of hydrochloric acid which is an inorganic acid (Comparative Example 3). ..
In the etching treatment, the immersion time in the solution was 30 seconds in both Examples 4 to 6 and Comparative Example 3.
In the evaluation of patterning property, when the immersion time has passed 30 seconds, it depends on whether or not the pattern of the oxide thin film remains, that is, if it remains, it is good (○), and if it does not remain, it is bad (○). X) was evaluated.

The evaluation results of the patternability and mobility of the obtained TFT are shown in Table 4 below.

As shown above, when each organic acid (Examples 1, 4 to 6) was used as the etching solution, good results were obtained in the mobility and patterning property of the TFT characteristics.
When an inorganic acid such as hydrochloric acid (Comparative Example 3) is used, the damage to the metal oxide film due to etching is large, the desired pattern cannot be obtained, and the mobility, which is a characteristic of the TFT, is improved. I couldn't do that either. Further, even as an organic acid, a hydroxycarbonate-based organic acid having a hydroxy group and a carboxylic acid group and exhibiting a chelating effect was used rather than an organic acid such as formic acid or acetic acid (Examples 5 and 6). Citrate (Example 1) and glycolic acid (Example 4) gave better results in both mobility and patterning of TFT characteristics.

The method for producing a coating type metal oxide film of the present invention and the coating type metal oxide film produced by using the same are not limited to those described in the above-described embodiment, and other various aspects thereof. It can be changed.

Further, the electronic device of the present invention is not limited to the above-described embodiment, and it is also possible to have a configuration in which another layer is interposed between the layers shown in the embodiment.
Further, in the above embodiment, the TFT as the electronic device has a bottom gate type configuration, but the top gate type TFT can be similarly applied as the electronic device of the present invention. However, in the case of a top-gate type TFT, the precursor solution of the metal oxide film is usually applied on the source / drain electrode or the substrate to form the metal oxide film.
Further, the method for manufacturing a coating type oxide film is not limited to that used as a method for manufacturing a semiconductor layer (channel layer) of a TFT, and is not limited to that used as a method for manufacturing a semiconductor layer (channel layer) of a TFT. It can also be suitably used for manufacturing methods such as.

In the embodiment of the present invention, the metal oxide film is a coating type, and each of the other layers is not necessarily a coating type, but all the layers may be a coating type. In this case, all the systems for performing the processing in vacuum can be eliminated.
Further, the display drive unit can be formed by using the above-mentioned TFT, and various display devices such as an organic EL display (OLED) and an LCD can be formed, for example.

By the way, as described above, in the present invention, water, which is the main component of the solvent in the precursor solution of the water-soluble metal oxide, causes a water splitting reaction when irradiated with energy rays, and activates oxygen radicals and the like. By being configured to generate oxygen species, a metal oxide film having no variation in shape can be formed by a simpler manufacturing process (see the present specification, paragraphs 0014 to 0016).
Therefore, as compared with the conventional coating type oxide semiconductor, it is possible to easily form a TFT having good performance, and it is possible to increase the area in particular, which is very useful.

The difference between the present invention and the prior art is the degree of crystallinity or bonding of the extent to which the precursor film is converted into a metal oxide film by the oxidizing action of active oxygen species such as oxygen radicals generated by the water splitting reaction. Although it is due to the difference in state, it is impossible to unequivocally specify the structure or characteristics related to the difference by wording.

On the other hand, the difference in crystallinity or bonding state between the present invention and the prior art can be measured in principle by using X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), or the like. However, although it may be possible to measure this at one or two points, the XRD or XPS spectrum is obtained by manufacturing or purchasing a number of coated oxide semiconductors according to the present invention and the prior art, respectively, which are statistically significant. After measuring the numerical characteristics of the above and performing statistical processing thereof, it is necessary to find a significant index and its value that distinguish the present invention from the prior art, which requires a huge amount of time and cost. Moreover, since there are enormous possibilities for the prior art, it is not possible to unambiguously determine a statistically significant number.
It is practically impractical to find the above indicators and their values and thereby directly identify the features of the present invention by the structure or properties of the object.

In consideration of such circumstances, the claims according to the present invention are defined by the style of the manufacturing method at present, but in the future, the style of the claims relating to the coating type metal oxide film having the following constitution will be adopted. If permitted, it is hoped that the following configuration will be added as a claim.
(Structure of coating type metal oxide film)
An inorganic acid salt composed of a metal salt is dissolved in a solvent in which an aqueous solvent occupies a weight of 50% or more to produce a water-soluble metal oxide precursor solution.
The generated precursor solution is applied onto a predetermined object to be coated, and the mixture is applied.
An energy ray is irradiated to a predetermined region of the precursor solution of the metal oxide coated on the predetermined object to be coated, and the region is oxidized to form a metal oxide film.
A coating type metal oxide film, which is formed by patterning the generated metal oxide film.

1, 101, 201 Substrate 2, 102, 202 Gate electrode 3, 103, 203 Gate insulating film 4, 104, 204 Semiconductor layer (coated metal oxide film)
205 Etching stop layer 6, 106, 206 Source / drain electrode 6a Source electrode 6b Drain electrode

Claims (8)

A precursor solution generation step of dissolving an inorganic acid salt composed of a metal salt in a solvent in which an aqueous solvent occupies a weight of 50% or more to produce a precursor solution of a water-soluble metal oxide.
A precursor coating step of applying the precursor solution produced in the precursor solution generation step onto a predetermined object to be coated, and a precursor coating step.
A soft annealing step of drying the object to be coated to which the precursor solution has been applied in the precursor coating step, and a soft annealing step.
An energy ray is irradiated to a predetermined region of the precursor film of the metal oxide applied on the object to be coated, which has been dried in the soft annealing step , and the predetermined region is oxidized to form a metal oxide film. Metal oxide film formation process and
Wherein not the metal oxide film forming step odor Te before Symbol metal oxide film, the metal oxide of the precursor film are removed in the region other than the predetermined region, an etching step of performing direct patterning,
A method for producing a coating type metal oxide film. The method for producing a coated metal oxide film according to claim 1, wherein the solvent occupies a weight of 80% or more of the aqueous solvent. The method for producing a coated metal oxide film according to claim 1 or 2, wherein the energy ray has a strength capable of generating active oxygen species in the aqueous solvent. The method for producing a coated metal oxide film according to any one of claims 1 to 3, wherein in the etching step, etching is performed with a solution containing an organic acid. The production of a coated metal oxide film according to claim 4, wherein the organic acid is a hydroxycarbonate-based organic acid having a chelating effect of forming a metal ligand complex with respect to metal ions. Method. A coated metal oxide film produced by the method for producing a coated metal oxide film according to any one of claims 1 to 5. An electronic device comprising the coating type metal oxide film according to claim 6. An electronic device according to claim 7, wherein the electronic device is configured as a thin film transistor.

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