JP6714071B2 - Method for producing zinc oxide film - Google Patents

Description

The present invention relates to a method for manufacturing a zinc oxide film.

Zinc oxide (ZnO) is expected to be applied to transparent conductive films, solar cells, light emitting devices and the like. ZnO can be controlled in conductivity by doping with an element such as Al or Ga. As a method of manufacturing a conductive ZnO film, a sputtering method and an ion plating method are widely known. Although a film having a resistivity as low as 10 ⁻⁴ Ωcm has been obtained by these methods, these methods require a vacuum process. Therefore, there is a problem that the manufacturing cost becomes excessive.

On the other hand, it has been attempted to form a conductive ZnO film using a wet method which is a low cost process. In Non-Patent Document 1 (Adv. Mater. 26 (2014) pp.632-636), a ZnO film having a specific resistance of 5.0×10 ⁻³ Ωcm is obtained by using a chemical bath deposition method (CBD method). ing. However, since unevenness is seen on the film surface, it is not suitable for manufacturing a device that requires stacking or bonding.

Further, an oriented zinc oxide (ZnO) substrate having high transparency and high conductivity has been proposed as a substrate for a light emitting device such as a light emitting diode (LED) and a surface emitting element, and an optical device such as a solar cell and an optical sensor. ing. For example, Patent Document 1 (WO2016/035721A1) discloses a plate-shaped zinc oxide sintered body containing a dopant element such as Al and having a (002) plane orientation degree of 60% or more in the plate surface. There is.

WO2016/035721A1

Harald Hagendorfer et al., "Highly Transparent and Conductive ZnO: Al Thin Films from a Low Temperature Aqueous Solution Approach", Adv. Mater. 26 (2014) pp.632-636

By the way, when a zinc oxide film is formed on a zinc oxide ceramic substrate by wet synthesis in the production of a light emitting element or a solar cell, an in-plane distribution occurs in the film thickness and the film density, and it is impossible to form a uniform film. There's a problem. The cause of the non-uniformity of the wet-synthesized zinc oxide film is not clear, but there are variations in the orientation of the particles that make up the underlying zinc oxide ceramics substrate, and even if these particles are oriented, polar (Zn plane/ It is conceivable that the (O face) becomes non-uniform.

The present inventors have now formed an underlying film having a structure different from zinc oxide, that is, a crystal structure other than wurtzite type or an amorphous structure, on a zinc oxide ceramic substrate prior to the formation of the zinc oxide film. As a result, it was found that a highly uniform zinc oxide film can be formed on a zinc oxide ceramic substrate by a wet method.

Therefore, an object of the present invention is to provide a method capable of forming a highly uniform zinc oxide film on a zinc oxide ceramic substrate by a wet method.

According to one aspect of the present invention, there is provided a method of manufacturing a zinc oxide film,
A step of forming a base film made of a material having a crystal structure or an amorphous structure other than wurtzite type on a zinc oxide ceramic substrate,
Forming a seed layer composed of zinc oxide by converting the base film into zinc oxide or by depositing zinc oxide on the base film;
A step of forming a zinc oxide film on the seed layer by a wet method,
Is provided.

It is the image which observed the surface of the zinc oxide film produced in Example 1 which is a comparative example with the scanning electron microscope. It is the image which observed the surface of the zinc oxide film produced in Example 3 with the scanning electron microscope.

Method for Producing Zinc Oxide Film In the method for producing a zinc oxide film according to the present invention, first, a base film made of a material having a crystal structure or an amorphous structure other than wurtzite type is formed on a zinc oxide ceramic substrate. To do. Then, the seed layer formed of zinc oxide is formed by converting the base film into zinc oxide or by depositing zinc oxide on the base film. Then, a zinc oxide film is formed on the seed layer by a wet method. Thus, prior to the formation of the zinc oxide film, the zinc oxide ceramic substrate is formed with a base film having a structure different from that of zinc oxide, that is, a crystalline structure other than wurtzite type or an amorphous structure. A highly uniform zinc oxide film can be formed on a ceramic substrate by a wet method. In this respect, even if the sputtered film of zinc oxide is formed on the zinc oxide ceramics substrate, the non-uniformity of the zinc oxide film formed by the wet method on the substrate does not disappear. On the other hand, when, for example, metallic zinc (which has a crystal structure other than wurtzite type) is formed on a zinc oxide ceramic substrate, and then zinc oxide is formed by an oxidation treatment, the zinc oxide film is formed by a wet method. Unexpectedly, a uniform film can be formed. Although the cause of this behavior is not clear, the crystal information derived from the zinc oxide ceramic substrate under the base film is formed by forming the base film made of a material having a crystal structure other than wurtzite type on the zinc oxide ceramic substrate. Is considered to be blocked and does not affect the zinc oxide film formed thereon by wet synthesis. For the same reason, it is considered that the same effect as described above can be obtained by forming a material having an amorphous structure on the zinc oxide ceramics substrate.

(1) Formation of Underlayer Film on Zinc Oxide Ceramic Substrate An underlayer film made of a material having a crystal structure or an amorphous structure other than wurtzite type is formed on a zinc oxide ceramic substrate. The zinc oxide ceramic substrate has an excellent advantage that it is cheaper than a general-purpose substrate such as a gallium nitride substrate as a material that can have transparency and conductivity. Therefore, the zinc oxide ceramic substrate having high transparency and high conductivity is preferable as a substrate for a light emitting device such as a light emitting diode (LED) or a surface emitting element, or an optical device such as a solar cell or an optical sensor. From such a viewpoint, the zinc oxide ceramics substrate is preferably a zinc oxide oriented polycrystalline sintered body, and particularly preferably a zinc oxide oriented polycrystalline sintered body containing a dopant element such as Al (see, for example, Patent Document 1). Is.

The base film is not particularly limited as long as it is made of a material having a crystal structure or an amorphous structure other than wurtzite type. That is, the underlayer typically has a crystal structure other than wurtzite type, but may have an amorphous structure. In any case, when considering application to a light emitting element or a solar cell, a material having a crystal structure or an amorphous structure other than wurtzite type is a material having transparency and conductivity, or a post-treatment. A material that can be converted into a material having transparency and conductivity by (for example, oxidation treatment) is preferable.

In a preferred embodiment of the present invention, the material forming the base film (that is, the material having a structure other than wurtzite type) is metallic zinc. Since metallic zinc is a material that can be converted into a material having transparency and conductivity (specifically, zinc oxide) by a post-treatment (specifically, oxidation treatment), the formation of the seed layer in the subsequent step can be performed with It can be performed by oxidation to zinc oxide, and as a result, the number of film forming steps can be reduced. In this way, metallic zinc can be converted into zinc oxide by the subsequent oxidation treatment, so that a seed layer having both transparency and conductivity can be provided.

In another preferred embodiment of the present invention, the material forming the underlayer film (that is, the material having a structure other than wurtzite type) is a material other than metallic zinc. The material having a structure other than the wurtzite type is not particularly limited, but in consideration of application to a light emitting device or a solar cell, a material having both transparency and conductivity is preferable. Preferred examples of the material having a crystal structure or an amorphous structure other than the wurtzite type include indium-tin oxide (ITO), fluorine-doped tin oxide, niobium-added titanium oxide, magnesium oxide, and any combination thereof. Can be mentioned.

In any of the above embodiments, the method for forming the base film on the zinc oxide ceramics substrate is not particularly limited. From the viewpoint of uniformity and the like, the formation of the base film is preferably performed by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Physical vapor deposition (PVD) is more preferable, and sputtering is most preferable from the viewpoint of film quality, uniformity, cost and the like. The sputtering method is not particularly limited, but magnetron sputtering is preferable. The thickness of the base film is not particularly limited as long as it is a thickness capable of blocking crystal information derived from the zinc oxide ceramics substrate below the base film, but is preferably 1 to 500 nm, more preferably 1 to 100 nm, and further It is preferably 1 to 50 nm.

(2) Formation of Zinc Oxide Seed Layer Next, a seed layer composed of zinc oxide is formed. The seed layer is formed by converting the base film into zinc oxide or by forming zinc oxide on the base film.

As described above, in the embodiment in which the material forming the underlayer film (that is, the material having a structure other than the wurtzite type) is metallic zinc, it is preferable that the seed layer is formed by oxidizing metallic zinc to zinc oxide. .. The oxidation of metallic zinc to zinc oxide is preferably performed by heat treatment at a predetermined temperature in an oxidizing atmosphere such as an oxygen atmosphere. The heat treatment temperature is preferably 200 to 600°C, more preferably 300 to 500°C. The heat treatment time at the above temperature is not particularly limited, but is preferably 1 hour or more, more preferably 1 to 20 hours, and further preferably 3 to 10 hours.

On the other hand, in a mode in which the material forming the underlayer film (that is, the material having a structure other than the wurtzite type) is a material other than metallic zinc, the seed layer is formed by forming zinc oxide on the underlayer film. Preferably. The method for forming the seed layer is not particularly limited, but it is preferable that the seed layer is formed by physical vapor deposition (PVD) or chemical vapor deposition (CVD) from the viewpoint of uniformity. Physical vapor deposition (PVD) is more preferable, and sputtering is most preferable from the viewpoint of film quality, uniformity, cost and the like. The sputtering method is not particularly limited, but magnetron sputtering is preferable. The thickness of the seed layer is not particularly limited, but is preferably 10 to 500 nm, more preferably 50 to 300 nm, further preferably 100 to 200 nm.

(3) Formation of Zinc Oxide Film by Wet Method After that, a zinc oxide film is formed on the seed layer by a wet method which is a low-cost process. The zinc oxide film may be formed by a wet method by a known method and is not particularly limited. Preferably, the zinc oxide film is formed by a wet method by immersing the zinc oxide ceramic substrate on which the seed layer is formed in a raw material solution containing zinc ions at a liquid temperature of 50 to 100° C. to deposit zinc oxide on the seed layer. It is performed by depositing in a film form. The liquid temperature of the raw material solution is preferably 50 to 100°C, more preferably 50 to 95°C, further preferably 60 to 95°C, and particularly preferably 70 to 95°C. The time for dipping the substrate with seed layer is not particularly limited as long as the time until the required film thickness is obtained is not particularly limited, but is preferably 30 minutes or more, more preferably 30 to 120 minutes, further preferably 60 to 120. Minutes.

The raw material solution contains zinc ions. The Zn concentration of the raw material solution (that is, the concentration of the Zn source) is preferably 0.01 to 0.2 mol/L, more preferably 0.01 to 0.1 mol/L. The Zn concentration in the raw material solution can be realized by dissolving the zinc ion supply source (Zn source). Examples of the Zn source include zinc sulfate, zinc nitrate, zinc chloride and the like. The pH of the raw material solution is preferably 10.0 to 11.0, and more preferably 10.2 to 10.8. The pH may be adjusted by adding aqueous ammonia to the raw material aqueous solution.

Preferably, the raw material solution contains a conductive dopant. A desired conductivity can be imparted to the zinc oxide film by adding a conductive dopant. Preferable examples of the conductive dopant include Group 3B elements such as Al and Ga, and Group 7B elements such as F, Cl, Br and I, and the like, with Al and Ga being particularly preferable, and Al being most preferable. The conductive dopant may be dissolved in the raw material solution in the form of a compound or ion containing the conductive dopant.

When the conductive dopant is Al, it is preferable that an aluminum salt is dissolved as an Al source in the raw material solution. At this time, the Al concentration of the raw material solution is preferably 0.001 to 0.010 mol/L, more preferably 0.001 to 0.008 mol/L, and further preferably 0.001 to 0.005 mol/L. is there. Examples of aluminum salts include aluminum nitrate, aluminum acetate, and aluminum chloride. In the preparation of this raw material solution, it is preferable to prepare a solution containing a Zn source and an Al source and then adjust the pH of the solution to 10.0 to 11.0 using NH ₃ or the like.

Before dipping the substrate in the raw material solution, it is preferable to heat the raw material solution until the liquid temperature is reached. Further, it is more preferable to immerse the substrate after holding the raw material solution for 15 to 60 minutes after reaching the liquid temperature. As described above, it is preferable to adjust the pH of the raw material solution containing the Zn source and the Al source to 10.0 to 11.0 using NH ₃ or the like. By heating this raw material solution, the solubility of NH ₃ is increased. Decrease to cause a decrease in pH. As a result, the state is changed to Zn and Al being simultaneously precipitated. By immersing the substrate with the seed layer in the raw material solution in that state, Al is taken into the zinc oxide film.

The zinc oxide film-coated substrate taken out from the raw material solution is preferably washed with ion-exchanged water. This cleaning is preferably performed by ultrasonic cleaning.

If necessary, the obtained zinc oxide film may be heat-treated at a predetermined temperature. The preferable heat treatment temperature is 300 to 800°C, more preferably 300 to 700°C, further preferably 300 to 600°C, and particularly preferably 300 to 500°C. The heat treatment time at the above temperature is not particularly limited, but is preferably 1 hour or more, more preferably 1 to 10 hours, and further preferably 5 to 10 hours. The heat treatment of the zinc oxide film is preferably performed in a reducing atmosphere containing hydrogen or the like because it is easy to realize a lower specific resistance. By heat-treating the thus-produced film, Al taken into the film functions more effectively as a dopant and conductivity is improved.

Although Al has been described as an example of the conductive dopant in the above description, other conductive dopants such as Ga can be used in the same manner as Al.

The present invention will be described more specifically by the following examples.

Example 1 (comparison)
(1) Preparation of Highly Oriented ZnO Ceramics Substrate 1730 g of zinc sulfate heptahydrate (manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 4.5 g of sodium gluconate (manufactured by Wako Pure Chemical Industries) were dissolved in 3000 g of ion-exchanged water. This solution was placed in a beaker and heated to 90° C. with stirring with a magnetic stirrer. While maintaining this solution at 90° C. and stirring, 490 g of 25% ammonium water was added dropwise with a microtube pump. After completion of dropping, the mixture was kept at 90° C. for 4 hours while stirring, and then left standing. The precipitate was separated by filtration, washed with ion-exchanged water three times, and dried to obtain a white powdery zinc oxide precursor. The obtained zinc oxide precursor was placed on a zirconia setter and calcined in the atmosphere in an electric furnace to obtain a plate-like porous zinc oxide powder. The temperature schedule during calcination was that the temperature was raised from room temperature to 900° C. at a rate of temperature increase of 100° C./h, held at 900° C. for 30 minutes, and allowed to cool naturally. The obtained plate-shaped zinc oxide powder was crushed with a ball made of ZrO _{2 to an} average particle size of 1.0 μm by a ball mill.

4.8 parts by weight of zinc oxide plate-like particles obtained by the above method, 95.2 parts by weight of commercially available high-purity ZnO powder (specific surface area 9.4 m ² /g), and commercially available high-purity θ-Al ₂ O 0.25 parts by weight of ₃ powders (specific surface area 82 m ² /g), binder (polyvinyl butyral: product number BM-2, manufactured by Sekisui Chemical Co., Ltd.), plasticizer (DOP: di(2-ethylhexyl) phthalate, black Kinkasei Co., Ltd.), a dispersant (product name: Leodol SP-O30, manufactured by Kao Co., Ltd.), and a dispersion medium (2-ethylhexanol) were mixed with a three-roll mill. The amount of the dispersion medium was adjusted so that the slurry viscosity would be 20000 cP. The slurry thus prepared was formed into a sheet by a doctor blade method on a PET film so that the thickness after drying was 50 μm. The obtained tape was cut and laminated, placed on an aluminum plate having a thickness of 10 mm, and then vacuum packed. This vacuum pack was hydrostatically pressed at a pressure of 200 kgf/cm ^{2 in} warm water of 85° C. to prepare a disk-shaped molded body having a diameter of about 65 mm×a thickness of 1.5 mm. The obtained molded body was placed in a degreasing furnace and degreased at 600° C. for 20 hours. The obtained degreased body was fired under atmospheric pressure at 1400° C. for 5 hours under atmospheric pressure to produce a disc-shaped sintered body. The produced sintered body was put in a 90 mm square alumina sheath, and hot isostatic pressing (HIP) treatment was performed in Ar gas at 1300° C. for 2 hours. The periphery of the obtained sintered body is processed, and the surface is mirror-polished with a diamond slurry to obtain a ZnO ceramic substrate having a surface roughness (arithmetic mean roughness) Ra≦5 nm, a diameter of about 52 mm and a thickness of 0.6 mm. It was The ZnO ceramics substrate obtained in this manner showed conductivity due to Al as a dopant, oxygen deficiency, and the like, and also showed high translucency due to a high degree of c-plane orientation.

(2) Film formation of wet-synthesized ZnO film A ZnO thin film having a thickness of 100 nm was formed as a seed layer on the above ZnO ceramic substrate by RF magnetron sputtering. Thus, a substrate with a seed layer was obtained.

Zinc nitrate hexahydrate (manufactured by Kanto Kagaku) as a Zn source and aluminum nitrate nonahydrate (manufactured by Kanto Kagaku) as an Al source were dissolved in ion-exchanged water to obtain a Zn concentration of 25 mM and an Al concentration of 0.5 mM. A raw material aqueous solution was prepared. Ammonia water (manufactured by Sigma-Aldrich) was added to the obtained raw material aqueous solution so that the pH was 10.4. The pH adjusted aqueous solution was heated to 90°C. Thirty minutes after the temperature reached 90° C., the substrate with seed layer was immersed in the raw material aqueous solution. The substrate with the seed layer was allowed to stand while the liquid temperature was maintained at 90° C. to deposit a ZnO precipitate in the form of a film, which was taken out after 60 minutes. The taken-out substrate was ultrasonically cleaned in ion-exchanged water. Thus, a wet-synthesized ZnO film was formed on the ZnO ceramic substrate.

(3) Confirmation of homogeneity of wet-synthesized ZnO film by observing surface/cross-section The surface and cross-section of the wet-synthesized ZnO film formed on the prepared ZnO ceramic substrate were observed by a scanning electron microscope, and the results shown in FIG. 1 were obtained. Inhomogeneity of the film state was observed. In order to manufacture a light emitting element or a solar cell device, it is necessary to subsequently deposit a material such as a p-type layer or an electrode. However, the above-mentioned inhomogeneity causes in-plane variation of device characteristics and leakage current. Is a cause of deterioration of device characteristics and is not preferable.

Example 2 (comparison)
(1) Preparation of ZnO ceramic substrate A ZnO ceramic substrate was prepared in the same manner as in Example 1.

(2) Formation of Wet Synthetic ZnO Film The wet synthetic ZnO film was formed as follows without forming a seed layer on the ZnO ceramic substrate. First, zinc nitrate hexahydrate (manufactured by Kanto Chemical Co., Inc.) as a Zn source and aluminum nitrate nonahydrate (manufactured by Kanto Chemical Co., Inc.) as an Al source were dissolved in ion-exchanged water to obtain a Zn concentration of 25 mM and an Al concentration of 0, respectively. A 0.5 mM raw material aqueous solution was prepared. Ammonia water (manufactured by Sigma-Aldrich) was added to the obtained raw material aqueous solution so that the pH was 10.4. The pH adjusted aqueous solution was heated to 90°C. The substrate was immersed in the raw material aqueous solution 30 minutes after the temperature reached 90°C. The substrate was allowed to stand while the liquid temperature was kept at 90° C. to deposit a ZnO precipitate in the form of a film, which was taken out after 60 minutes. The taken-out substrate was ultrasonically cleaned in ion-exchanged water. Thus, a wet-synthesized ZnO film was formed on the ZnO ceramic substrate.

(3) Confirmation of homogeneity of wet-synthesized ZnO film by surface/cross-section observation As a result of confirming homogeneity of the wet-synthesized ZnO film as in Example 1, it was confirmed to be non-homogeneous.

Example 3
(1) Preparation of ZnO ceramic substrate A ZnO ceramic substrate was prepared in the same manner as in Example 1.

(2) Formation of wet-synthesized ZnO film A metal Zn layer having a thickness of 50 nm was formed on the above ZnO ceramic substrate by DC magnetron sputtering. Then, the substrate with the metal Zn thin film was kept in an oxygen atmosphere at 400° C. for 10 hours to oxidize the metal Zn into ZnO to form a ZnO film as a seed layer. Thus, a substrate with a seed layer was obtained.

Zinc nitrate hexahydrate (manufactured by Kanto Kagaku) as a Zn source and aluminum nitrate nonahydrate (manufactured by Kanto Kagaku) as an Al source were dissolved in ion-exchanged water to obtain a Zn concentration of 25 mM and an Al concentration of 0.5 mM. A raw material aqueous solution was prepared. Ammonia water (manufactured by Sigma-Aldrich) was added to the obtained raw material aqueous solution so that the pH was 10.4. The pH adjusted aqueous solution was heated to 90°C. Thirty minutes after the temperature reached 90° C., the substrate with seed layer was immersed in the raw material aqueous solution. While keeping the liquid temperature at 90° C., the solution was left standing to deposit a ZnO precipitate in a film form, and after 60 minutes, it was taken out. The taken-out substrate was ultrasonically cleaned in ion-exchanged water. Thus, a wet-synthesized ZnO film was formed on the ZnO ceramic substrate.

(3) Confirmation of homogeneity of wet-synthesized ZnO film by surface/cross-section observation As a result of confirming homogeneity of the wet-synthesized ZnO film as in Example 1, it was confirmed that the wet-synthesized ZnO film was homogeneous as shown in FIG.

Example 4
(1) Preparation of ZnO ceramic substrate A ZnO ceramic substrate was prepared in the same manner as in Example 1.

(2) Film formation of wet-synthesized ZnO film On the above ZnO ceramic substrate, a MgO layer having a thickness of 50 nm was formed as an underlayer by RF magnetron sputtering. Then, a 100 nm-thick ZnO thin film was formed as a seed layer on the underlayer by RF magnetron sputtering. Thus, a substrate with a seed layer was obtained.

Zinc nitrate hexahydrate (manufactured by Kanto Chemical Co., Inc.) as a Zn source and aluminum nitrate nonahydrate (manufactured by Kanto Chemical Co., Inc.) as an Al source were dissolved in ion-exchanged water to obtain a Zn concentration of 25 mM and an Al concentration of 0.5 mM. A raw material aqueous solution was prepared. Ammonia water (manufactured by Sigma-Aldrich) was added to the obtained raw material aqueous solution so that the pH was 10.4. The pH adjusted aqueous solution was heated to 90°C. Thirty minutes after the temperature reached 90° C., the seed layer-coated substrate was immersed in the raw material aqueous solution. While keeping the liquid temperature at 90° C., the solution was left standing to deposit a ZnO precipitate in a film form, and after 60 minutes, it was taken out. The taken-out substrate was ultrasonically cleaned in ion-exchanged water. Thus, a wet-synthesized ZnO film was formed on the ZnO ceramic substrate.

(3) Confirmation of homogeneity of wet-synthesized ZnO film by surface/cross-section observation As a result of confirming homogeneity of the wet-synthesized ZnO film as in Example 1, it was confirmed to be homogeneous.

Example 5
(1) Preparation of ZnO ceramic substrate A ZnO ceramic substrate was prepared in the same manner as in Example 1.

(2) Film formation of wet-synthesized ZnO film On the ZnO ceramic substrate, an indium-tin oxide (ITO) layer having a thickness of 50 nm was formed as a base layer by DC magnetron sputtering. Then, a 100 nm-thick ZnO thin film was formed as a seed layer on the underlayer by RF magnetron sputtering. Thus, a substrate with a seed layer was obtained.

Zinc nitrate hexahydrate (manufactured by Kanto Kagaku) as a Zn source and aluminum nitrate nonahydrate (manufactured by Kanto Kagaku) as an Al source were dissolved in ion-exchanged water to obtain a Zn concentration of 25 mM and an Al concentration of 0.5 mM. A raw material aqueous solution was prepared. Ammonia water (manufactured by Sigma-Aldrich) was added to the obtained raw material aqueous solution so that the pH was 10.4. The pH adjusted aqueous solution was heated to 90°C. Thirty minutes after the temperature reached 90° C., the substrate with seed layer was immersed in the raw material aqueous solution. While keeping the liquid temperature at 90° C., the solution was left standing to deposit a ZnO precipitate in a film form, and after 60 minutes, it was taken out. The taken-out substrate was ultrasonically cleaned in ion-exchanged water. Thus, a wet-synthesized ZnO film was formed on the ZnO ceramic substrate.

(3) Confirmation of homogeneity of wet-synthesized ZnO film by surface/cross-section observation As a result of confirming homogeneity of the wet-synthesized ZnO film as in Example 1, it was confirmed to be homogeneous.

Claims (11)

A method of manufacturing a zinc oxide film, comprising:
A step of forming a base film made of a material having a crystal structure or an amorphous structure other than wurtzite type on a zinc oxide ceramic substrate,
Forming a seed layer composed of zinc oxide by converting the base film into zinc oxide or by depositing zinc oxide on the base film;
A step of forming a zinc oxide film on the seed layer by a wet method,
Including the method. The method according to claim 1, wherein the formation of the underlayer is performed by physical vapor deposition or chemical vapor deposition. The method according to claim 2, wherein the formation of the underlayer is performed by physical vapor deposition, and the physical vapor deposition is sputtering. The material having a crystal structure or an amorphous structure other than the wurtzite type is a material having transparency and conductivity, or a material which can be converted into a material having transparency and conductivity by post-treatment, The method according to claim 1. The material having a crystal structure or an amorphous structure other than the wurtzite type is metallic zinc, and the formation of the seed layer is performed by oxidizing the metallic zinc to zinc oxide. The method according to paragraph 1. The material having a crystal structure or an amorphous structure other than the wurtzite type is a material other than metallic zinc, and the seed layer is formed by forming zinc oxide on the base film. The method according to any one of 1 to 4. The material having a crystal structure or an amorphous structure other than the wurtzite type is at least one selected from the group consisting of indium-tin oxide (ITO), fluorine-doped tin oxide, niobium-added titanium oxide, and magnesium oxide. 7. The method of claim 6, wherein The method according to claim 6, wherein the seed layer is formed by physical vapor deposition or chemical vapor deposition. The method according to claim 8, wherein the formation of the seed layer is performed by physical vapor deposition, and the physical vapor deposition is sputtering. To form the zinc oxide film by the wet method, the zinc oxide ceramic substrate having the seed layer formed thereon is immersed in a raw material solution containing zinc ions at a liquid temperature of 50 to 100° C. to form zinc oxide on the seed layer. 10. A method according to any one of claims 1-9, comprising depositing the in a film. The method according to claim 1, wherein the zinc oxide ceramic substrate is a zinc oxide oriented polycrystalline sintered body.