JP6774593B2 - Crystalline oxide film - Google Patents

Description

The present invention relates to crystalline oxide films and their uses.

The indium oxide film is suitable as a transparent conductive film because it exhibits a metallic electrical resistivity of about 1 × 10 ^-4 Ωcm by doping with tin and at the same time maintains transparency, and is suitable for a liquid crystal display. It is widely used as a pixel electrode, a carrier collecting electrode for solar cells, and the like. When used in such applications, a high surface resistance value causes the output to be lowered. Therefore, it is generally desirable that the surface resistance value is relatively low, and therefore an indium oxide film having high crystallinity is required. (Patent Document 1).

Further, in the field of oxide electronics, indium oxide is a promising semiconductor based on a large bandgap of 3.6 to 3.75 eV. When indium oxide is used as a semiconductor, it is necessary to devise ways to increase the mobility as much as possible, but there are problems such as difficulty in producing a thick film having high crystallinity.
Further, when configuring a device, an insulating film is often required in addition to the semiconductor film having high mobility. In such a case, if indium oxide having high mobility and indium oxide having insulating properties can be obtained, an electronic device such as a FET transistor can be realized by laminating them with each other. When indium oxide is used as an insulating film, the electrical resistivity must be increased as much as possible, contrary to the case of a transparent electrode material. Therefore, it is necessary to remove impurity ions as much as possible and devise ways to minimize oxygen defects. (Patent Document 2).

As an effort to create a thick film while increasing the crystallinity of the indium oxide film, in Non-Patent Document 1, an In ₂ O ₃ film having a big bite structure is formed on an In ₂ O ₃ substrate by using the MBE method. and rocking curve half width of the X-ray diffraction method is to create a highly crystalline film (thickness 720 nm) as 83.1Arcsec. However, with the MBE method, it is difficult to obtain a highly crystalline film having a film thickness of 1 μm or more, and in particular, it has not been possible to obtain a film having a half width of 100 arcsec or less and a film thickness of 1 μm or more. Further, as in the invention described in Patent Document 3, the preparation of an indium oxide film using the mist CVD method is being studied. For example, in Non-Patent Document 2, the In ₂ O ₃ thin film having a corundum structure on a sapphire substrate using a mist CVD method is grown, the rocking curve half width of the X-ray diffraction method to obtain a thin film highly oriented that 182arcsec Although it was successful, the film thickness was about 300 nm at most. Further, even if these techniques are used, it is difficult to produce a film having a lower half width than this, and usually only a thin film of about 300 to 1000 arcsec is obtained. In addition, such a film has problems such as pits on the surface, and the surface smoothness is not satisfactory.

Japanese Unexamined Patent Publication No. 2013-193440 Japanese Patent No. 4480809 Japanese Unexamined Patent Publication No. 2014-234337

Cornelia Haas, "Molecular Beam Epitaxial Growth and Doping Studies of In2o3 Films on ZrO2: Y (111) and In2O3 (111)", Inaugural dissertation of university of Freiburg, 2013 Norihiro Suzuki, Kentaro Kaneko, Shizuo Fujita, "Growth of corundum-structured In2O3 thin films on sapphire particularly with Fe2O3 buffer layers", Journal of Crystal Growth 364, 2013

An object of the present invention is to provide a crystalline oxide film containing an oxide containing indium, which has high crystallinity, as a main component and having a film thickness of 1 μm or more.

As a result of diligent studies to achieve the above object, the present inventors, when a film is formed by the mist CVD method under specific conditions, contains an oxide containing highly crystalline indium as a main component, and further. It has been found that a crystalline oxide film containing a metastable phase corundum structure can be formed. Further, the present inventors have found that such a crystalline oxide film can solve the above-mentioned conventional problems at once.
In addition, after obtaining the above findings, the present inventors have further studied and completed the present invention.

That is, the present invention relates to the following invention.
[1] A crystalline oxide film containing an oxide containing indium as a main component, characterized in that the film thickness is 1 μm or more and the half-value width of the locking curve of the X-ray diffraction method is 100 arcsec or less. Crystalline oxide film.
[2] The crystalline oxide film according to the above [1], wherein the oxide is a single crystal or a polycrystalline.
[3] The crystalline oxide film according to the above [1] or [2], wherein the oxide is indium oxide.
[4] The crystalline oxide film according to any one of [1] to [3], wherein the oxide has a corundum structure.
[5] The crystalline oxide film according to any one of [1] to [4] above, which contains a dopant.
[6] The crystalline oxide film according to any one of [1] to [5], wherein the half width is 50 arcsec or less.
[7] The crystalline oxide film according to any one of [1] to [6] above, which is a transparent conductive film.
[8] A device including at least one or more films selected from an insulating film, a semiconductor film, and a conductive film and an electrode, wherein the film is described in any one of the above [1] to [7]. A device characterized by being a crystalline oxide film of.
[9] The device according to the above [8], wherein the film is the crystalline oxide film according to claim 7.
[10] The device according to [9] above, which is a solar cell, a display, lighting, electronic paper, a transistor, a printable circuit, or a transparent surface heating element.

According to the present invention, it is possible to provide a crystalline oxide film containing an oxide containing indium, which has high crystallinity, as a main component and having a film thickness of 1 μm or more.

It is a schematic block diagram of the film forming apparatus (mist CVD) used in an Example. It is a schematic block diagram of the film forming apparatus (mist CVD) used in the comparative example. It is a figure which shows the observation result of AFM in an Example.

Crystalline oxide film of the present invention is a crystalline oxide film comprising an oxide containing indium as a main component, the film thickness is 1 [mu] m, the rocking curve half value width of the X-ray diffraction method is less 100arcsec It is characterized by being.

The crystalline oxide film of the present invention may be an insulating film, a semiconductor film or a conductive film, but may be a conductive film or a transparent conductive film.

The crystal contained in the crystalline oxide film may be a single crystal or a polycrystal, or a mixture thereof. In the present invention, it is preferable that the crystal is made of an oxide containing indium. The "main component" is a composition ratio (atomic ratio) in the crystalline oxide film, which contains 50% or more of the oxide, preferably 70% or more, and more preferably. Is 90% or more.

The oxide is not particularly limited as long as it contains indium. Examples of the oxide containing indium include indium oxide, tin-doped indium oxide (ITO), gallium-doped indium oxide, and indium-doped zinc oxide. As the oxide, preferably, indium oxide or tin-doped indium oxide can be mentioned, and more preferably, indium oxide can be mentioned. In the present invention, the oxide preferably has a corundum structure, more preferably indium oxide having a corundum structure or tin-doped indium oxide, and indium oxide having a corundum structure. Is most preferable.

The film thickness of the crystalline oxide film is not particularly limited as long as it is 1 μm or more, but in the present invention, the film thickness is preferably 1.5 μm or more, more preferably 1.8 μm or more. .. The shape of the crystalline oxide film is not particularly limited, and may be a quadrangular shape, a circular shape, or a polygonal shape. The surface area of the crystalline oxide film is not particularly limited, and in the present invention, it is preferably 3 mm square or more, more preferably 5 mm square or more, and most preferably 50 mm or more in diameter.

The crystalline oxide film may contain a dopant. The dopant is not particularly limited and may be a known one. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants. In the present invention, the dopant is preferably tin. The content of the dopant is preferably 0.00001 atomic% or more, more preferably 0.00001 atomic% to 20 atomic%, and 0.00001 atomic% to 0.00001 atomic% in the composition of the crystalline oxide film. Most preferably, it is 10 atomic%.

The above-mentioned "half-value width" means a value obtained by measuring the half-value width of the locking curve by XRD (X-ray diffraction: X-ray diffraction method). The plane orientation is not particularly limited, and examples thereof include [0006]. In the present invention, the full width at half maximum is usually 100 arcsec or less, but is preferably 50 arcsec or less, and more preferably 40 arcsec or less.

Hereinafter, preferred methods for producing the crystalline oxide film will be described, but the present invention is not limited to these preferred methods.

As a preferable method for producing the crystalline oxide film, for example, a cold wall type mist CVD apparatus as shown in FIG. 1 is used to atomize or dropletize the raw material solution (atomization / droplet atomization step). The mist or droplets are transported to a substrate installed in the film forming chamber by a carrier gas (inert gas) (transportation step), and then the mist or droplets are thermally reacted at 500 ° C. or lower in the film forming chamber. Examples thereof include a method of forming a crystalline oxide film on the substrate (deposition step).

(Atomization / droplet formation process)
In the atomization / droplet atomization step, the raw material solution is atomized or dropletized. The means for atomizing or dropletizing the raw material solution is not particularly limited as long as the raw material solution can be atomized or atomized, and may be known means, but in the present invention, ultrasonic waves are used. The atomizing means or droplet forming means used is preferable. The mist or droplet obtained by using ultrasonic waves is preferable because it has a zero initial velocity and floats in the air. For example, it is possible to float in space and transport it as a gas instead of spraying it like a spray. Since it is a possible mist, it is not damaged by collision energy, so it is very suitable. The droplet size is not particularly limited and may be a droplet of about several mm, but is preferably 50 μm or less, and more preferably 0.1 to 10 μm.

(Ingredient solution)
The raw material solution can be atomized or dropletized, and is not particularly limited as long as it contains indium. In the present invention, as the raw material solution, a solution in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or a salt can be preferably used. Examples of the form of the complex include an acetylacetonate complex, a carbonyl complex, an ammine complex, and a hydride complex. Examples of the salt form include organic metal salts (for example, metal acetate, metal oxalate, metal citrate, etc.), metal sulfide salts, nitrified metal salts, phosphor oxide metal salts, and metal halide metal salts (for example, metal chloride). Salts, metal bromide salts, metal iodide salts, etc.) and the like. In the present invention, it is preferable that the raw material solution is an indium halide metal salt. By using such a preferable raw material solution, the surface smoothness of the film can be improved, and the crystallinity of the film can be further improved.

The raw material solution may contain a dopant. By including the dopant in the raw material solution, doping can be performed satisfactorily. The dopant is not particularly limited as long as it does not interfere with the object of the present invention. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants. The concentration of the dopant may usually be about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant should be as low as about 1 × 10 ¹⁷ / cm ³ or less, for example. You may. Further, according to the present invention, the dopant may be contained in a high concentration of about 1 × 10 ²⁰ / cm ³ or more.

The solvent of the raw material solution is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solvent of the inorganic solvent and the organic solvent. In the present invention, the solvent preferably contains water, more preferably water or a mixed solvent of water and alcohol, and most preferably water. More specific examples of the water include pure water, ultrapure water, tap water, well water, mineral spring water, mineral water, hot spring water, spring water, fresh water, seawater, and the like. Ultrapure water is preferred.

(Transport process)
In the transfer step, the mist or the droplets are conveyed into the film forming chamber by using the carrier gas. As the carrier gas, an inert gas such as nitrogen or argon is used. Further, the type of the carrier gas may be one type, but may be two or more types, and a diluted gas having a reduced flow rate (for example, a 10-fold diluted gas) or the like is further used as the second carrier gas. May be good. Further, the carrier gas may be supplied not only at one location but also at two or more locations. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min. In the case of a diluting gas, the flow rate of the diluting gas is preferably 0.001 to 2 L / min, more preferably 0.1 to 1 L / min.

(Film formation process)
In the film forming step, a crystalline oxide film is formed on the substrate by thermally reacting the mist or droplets in the film forming chamber. The thermal reaction may be such that the mist or droplet reacts with heat, and the reaction conditions and the like are not particularly limited as long as the object of the present invention is not impaired. In this step, the thermal reaction is usually carried out at a temperature of 500 ° C. or lower, preferably 400 ° C. or lower, more preferably 350 ° C. or lower, and most preferably 150 ° C. to 350 ° C. Further, the thermal reaction may be carried out in any of vacuum, non-oxygenic atmosphere, reducing gas atmosphere and oxygen atmosphere as long as the object of the present invention is not impaired, but the thermal reaction may be carried out in a non-oxygen atmosphere (for example). , In an atmosphere such as an inert gas such as nitrogen or argon or a reducing gas such as hydrogen gas or forming gas), and more preferably in an inert gas atmosphere. Further, it may be carried out under any conditions of atmospheric pressure, pressurization and depressurization, but in the present invention, it is preferably carried out under atmospheric pressure. The film thickness can be set to 1 μm or more by adjusting the film formation time.

(Hypokeimenon)
The substrate is not particularly limited as long as it can support the crystalline oxide film. The material of the substrate is also not particularly limited as long as it does not interfere with the object of the present invention, and may be a known substrate, an organic compound, or an inorganic compound. The shape of the substrate may be any shape and is effective for any shape, for example, plate-like, fibrous, rod-like, columnar, prismatic, such as a flat plate or a disk. Examples thereof include a tubular shape, a spiral shape, a spherical shape, a ring shape, and a porous body shape, but in the present invention, a substrate is preferable. The thickness of the substrate is not particularly limited in the present invention.

The substrate is not particularly limited as long as it has a plate shape and serves as a support for the crystalline oxide film. It may be an insulator substrate, a semiconductor substrate, a metal substrate or a conductive substrate, but it is preferable that the substrate is an insulator substrate, and the surface is made of metal. A substrate having a film is also preferable. The shape of the substrate is not particularly limited and may be substantially circular (for example, circular, elliptical, etc.) or polygonal (for example, triangular, square, rectangular, pentagonal, hexagonal, heptagonal). , Heptagon, nonagon, etc.), and various shapes can be preferably used. In the present invention, the shape of the film formed on the substrate can be set by making the shape of the substrate a preferable shape. Further, in the present invention, a large-area substrate can be used, and by using such a large-area substrate, the area of the crystalline oxide film can be increased. The substrate includes, for example, a base substrate containing a substrate material having a corundum structure as a main component, a substrate substrate containing a substrate material having a β-gaul structure as a main component, and a substrate material having a hexagonal structure as a main component. Examples include a base substrate. Here, the "main component" means that the substrate material having the specific crystal structure has an atomic ratio of preferably 50% or more, more preferably 70% or more, still more preferably 90% with respect to all the components of the substrate material. It means that it is contained in% or more, and may be 100%.

The substrate material is not particularly limited and may be known as long as it does not interfere with the object of the present invention. Examples of the substrate material having the corundum structure are α-Al ₂ O ₃ (sapphire substrate) or α-Ga ₂ O ₃ , and a-plane sapphire substrate, m-plane sapphire substrate, and r-plane sapphire substrate are preferable. , C-plane sapphire substrate, α-type gallium oxide substrate (a-plane, m-plane or r-plane) and the like are more preferable examples. As the base substrate mainly composed of the substrate material having a β-gaul structure, for example, β-Ga ₂ O ₃ substrate or Ga ₂ O ₃ and Al ₂ O ₃ are included, and Al ₂ O ₃ is more than 0 wt%. Examples thereof include a mixed crystal substrate having a content of 60 wt% or less. Further, examples of the base substrate containing a substrate material having a hexagonal structure as a main component include a SiC substrate, a ZnO substrate, and a GaN substrate.

In the present invention, the substrate preferably has a corundum structure, more preferably a base substrate containing a substrate material having a corundum structure as a main component, and most preferably a sapphire substrate or an α-type gallium oxide substrate. preferable. Further, the substrate preferably contains aluminum, more preferably a base substrate containing an aluminum-containing substrate material having a corundum structure as a main component, and a sapphire substrate (preferably a c-plane sapphire substrate, an a-plane sapphire substrate, M-plane sapphire substrate, r-plane sapphire substrate) is most preferable.

In the present invention, a film may be formed on the substrate as it is, but it is preferable that the buffer layer is laminated on the substrate and then formed on the substrate via the buffer layer. Examples of the buffer layer include a semiconductor layer containing a corundum structure, an insulator layer, a conductor layer, and the like, and among them, a semiconductor layer containing a corundum structure is preferable. Examples of the semiconductor layer containing the corundum structure include α-Fe ₂ O ₃ , α-Ga ₂ O ₃ , and α-Al ₂ O ₃ . The means for laminating the buffer layer is not particularly limited, and may be the same as the means for laminating the crystalline oxide film.

Crystalline oxide film obtained as described above, the film thickness is not less 1μm or more, further, the rocking curve half width of the X-ray diffraction method is less 100 arcsec, is excellent in crystallinity. Such a crystalline oxide film can be suitably used for devices and the like. Examples of the device include a solar cell, a display, a lighting, an electronic paper, a transistor, a printable circuit, a transparent sheet heating element, and the like. In the present invention, it is preferable that the device includes at least one or more films selected from an insulating film, a semiconductor film, and a conductive film and an electrode.

Examples of the present invention will be described below, but the present invention is not limited thereto.

(Example 1)
1. 1. Film formation device The mist CVD device 1 used in this embodiment will be described with reference to FIG. The mist CVD apparatus 1 includes a carrier gas source 2a for supplying a carrier gas, a flow rate control valve 3a for adjusting the flow rate of the carrier gas sent out from the carrier gas source 2a, and a carrier gas (diluted) for supplying the carrier gas (diluted). Diluted) source 2b, flow control valve 3b for adjusting the flow rate of carrier gas (diluted) sent out from carrier gas (diluted) source 2b, mist source 4 containing precursor solution 4a, and water 5a. The container 5, the ultrasonic vibrator 6 attached to the bottom surface of the container 5, the film forming chamber 7, the supply pipe 9 connecting the mist generation source 4 to the film forming chamber 7, and the inside of the film forming chamber 7. It is provided with a hot plate 8 installed in the above and an exhaust port 11 for discharging mist, droplets and exhaust gas after a thermal reaction. The substrate 10 is installed on the hot plate 8.
2. Preparation of precursor solution Indium bromide was mixed with ultrapure water, and the aqueous solution was adjusted to 0.025 mol of indium bromide.

3. 3. Preparation for film formation 2. The precursor solution 4a obtained in 1 above was housed in the mist source 4. Next, as the substrate 10, a sapphire substrate (2 inches in diameter) on which an α-Fe ₂ O ₃ film is laminated as a buffer layer on the surface is installed on the hot plate 8 and the hot plate 8 is operated to operate the film forming chamber. The temperature inside 7 was raised to 350 ° C. Next, the flow rate control valves 3a and 3b are opened, the carrier gas is supplied into the film forming chamber 7 from the carrier gas supply means 2a and 2b which are the carrier gas sources, and the atmosphere of the film forming chamber 7 is sufficiently filled with the carrier gas. After the replacement, the flow rate of the carrier gas was adjusted to 5.0 L / min, and the flow rate of the carrier gas (dilution) was adjusted to 0.5 L / min. Nitrogen was used as the carrier gas.

4. Membrane formation Next, the ultrasonic transducer 6 was vibrated at 2.4 MHz, and the vibration was propagated to the precursor solution 4a through water 5a to atomize the precursor solution 4a to generate mist 4b. .. This mist 4b is introduced into the film forming chamber 7 by the carrier gas through the supply pipe 9, and the mist thermally reacts in the film forming chamber 7 at 350 ° C. under atmospheric pressure to cause the substrate 10 to react. An indium oxide film was formed on the film. The film thickness was 1.8 μm, and the film formation time was 120 minutes.

Above 4. The indium oxide film obtained in 1) was a clean crystal without cloudiness. Was the identification of membranes using X-ray diffraction apparatus, the resulting film was α-In ₂ O ₃ film. Further, the rocking curve half width measured by X-ray diffraction method is 36Arcsec, was highly crystalline film. Further, when the film surface was observed with an atomic force microscope (AFM), as shown in FIG. 3, a film having no pits or the like on the surface and having excellent surface smoothness was obtained.

(Comparative Example 1)
With reference to FIG. 2, for explaining the mist CVD apparatus 19 used in Comparative Example 1. The mist CVD apparatus 19 includes a susceptor 21 on which the substrate 20 is placed, a carrier gas supply means 22a for supplying the carrier gas, and a flow control valve 23a for adjusting the flow rate of the carrier gas sent out from the carrier gas supply means 22a. , A carrier gas (diluted) supply means 22b for supplying a carrier gas (diluted), a flow control valve 23b for adjusting the flow rate of the carrier gas sent out from the carrier gas (diluted) supply means 22b, and a raw material solution 24a are accommodated. A supply pipe 27 composed of a mist generation source 24, a container 25 containing water 25a, an ultrasonic transducer 26 attached to the bottom surface of the container 25, and a quartz tube having an inner diameter of 40 mm, and a peripheral portion of the supply tube 27. It is equipped with a heater 28 installed in. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal plane. By making both the supply pipe 27 and the susceptor 21 serving as the film forming chamber from quartz, it is possible to prevent impurities derived from the apparatus from being mixed into the film formed on the substrate 20.

The film was formed in the same manner as in Example 1 except that the mist CVD device 19 shown in FIG. 4 was used as the film forming apparatus and the film forming time was set to 40 minutes. The resulting film per, was identified using X-ray diffraction device was α-In ₂ O _3. The measured half width with a X-ray diffraction device was 187Arcsec. The film thickness was 250 nm.

As described above, it can be seen that the crystalline oxide film of the present invention is excellent in crystallinity and has a film thickness of 1 μm or more.

The crystalline oxide film of the present invention can be used for various devices, but is particularly useful for solar cells, displays, lighting, electronic paper, transistors, printable circuits, transparent sheet heating elements, and the like.

1 Mist CVD equipment 2a Carrier gas source 2b Carrier gas (dilution) source 3a Flow control valve 3b Flow control valve 4 Mist generation source 4a Raw material solution 4b Mist 5 Container 5a Water 6 Ultrasonic transducer 7 Formation chamber 8 Hot plate 9 Supply Tube 10 Board 11 Exhaust port 19 Mist CVD device 20 Board 21 Suceptor 22a Carrier gas supply means 22b Carrier gas (diluted) supply means 23a Flow control valve 23b Flow control valve 24 Mist source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic vibration Child 27 Supply pipe 28 Heater 29 Exhaust port

Claims (9)

A crystalline oxide film containing an oxide containing indium as a main component, having a film thickness of 1 μm or more, and having a locking curve half-value width of 100 arcsec measured with respect to the [0006] plane. or less, wherein the oxide has a corundum structure, further, the crystalline oxide film, wherein the oxide, characterized in that indium oxide, tin-doped indium oxide or gallium oxide doped indium arm. The crystalline oxide film according to claim 1, wherein the oxide is single crystal or polycrystalline. The crystalline oxide film according to claim 1 or 2, wherein the oxide is indium oxide. The crystalline oxide film according to any one of claims 1 to 3, which contains a dopant. The crystalline oxide film according to any one of claims 1 to 4, wherein the half width is 50 arcsec or less. The crystalline oxide film according to any one of claims 1 to 5, which is a transparent conductive film. A device comprising at least one or more films selected from an insulating film, a semiconductor film, and a conductive film and an electrode, wherein the film is a crystalline oxide film according to any one of claims 1 to 6. A device characterized by being. The device according to claim 7, wherein the film is the crystalline oxide film according to claim 6. The device according to claim 8, which is a solar cell, a display, a lighting, an electronic paper, a transistor, a printable circuit, or a transparent sheet heating element.