KR102748330B1 - Transparent conducting film, target for transparent conducting film and its manufacturing method - Google Patents

Abstract

The present invention provides a transparent conductive film having high electron mobility and low resistivity and carrier concentration even under conditions of lowering the heat treatment temperature by including an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound, a target for a transparent conductive film for producing the same, and a method for producing the same.

Description

{Transparent conducting film, target for transparent conducting film and its manufacturing method}

The present invention relates to a transparent conductive film having excellent electron mobility, a target for a transparent conductive film, and a method for manufacturing the same.

Transparent conductive films can be used as transparent electrodes for solar cells, flat panel displays, and light-sensitive elements. In addition, transparent conductive films are also widely used for automobile windows, heat reflecting films for construction, and anti-static films.

When a transparent conductive film is used as a transparent electrode, high light transmittance and electrical conductivity are required. For example, the transparent electrode should have a light transmittance of 85% or more in the visible light range, and the resistivity should be lower than 1×10 ^-3 Ωcm. As described above, a transparent electrode having low resistivity is particularly suitable for use as a surface element of solar cells, liquid crystals, organic EL (organic electro luminescence) and inorganic EL (inorganic electro luminescence), or touch panels.

As transparent conductive films, tin oxide (SnO ₂ ) thin films, zinc oxide (ZnO) thin films, and indium oxide (In ₂ O ₃ ) thin films are known. Among these, tin oxide thin films mainly contain antimony (Sb) as a dopant (ATO thin film) or contain fluorine (F) as a dopant (FTO thin film). In addition, zinc oxide thin films mainly contain aluminum (Al) as a dopant (AZO thin film) or contain gallium (Ga) as a dopant (GZO thin film). Indium tin oxide (ITO, hereinafter referred to as "ITO") and indium zinc oxide (IZO, hereinafter referred to as "IZO") are used as indium oxide thin films. The ITO and IZO thin films have excellent optical and electrical properties and are currently widely used as transparent electrode materials.

Meanwhile, transparent conductive films are mainly manufactured by sputtering or ion plasma. In particular, sputtering is effective in cases where it is necessary to precisely control the film thickness or the film formation of a material with low vapor pressure, and is widely used because the operation is very simple and convenient. The sputtering method uses a target, which is a raw material for the thin film, to manufacture the thin film. The target is a solid containing a metal element that is formed to form a film and constitutes the thin film, and a sintered body such as a metal, metal oxide, metal nitride, or metal carbide is used, or in some cases, a single crystal is used. The sputtering method generally uses a device having a vacuum chamber in which a substrate and a target can be placed inside. First, the substrate and target are placed in the vacuum chamber, and then a high vacuum is created, and then a rare gas such as argon is injected to control the inside of the vacuum chamber to a gas pressure of approximately 10 Pa or less. Then, the substrate is made an anode, and the target is made a cathode, and argon plasma is generated by glow discharge between the two. At this time, argon positive ions in the plasma collide with the cathode target, and the target particles bounced off by the collision are deposited on the substrate to form a transparent electrode.

However, ITO thin films need to be crystallized to lower the resistivity, and therefore, it is necessary to form a film at high temperatures or perform heat treatment at high temperatures after film formation. Accordingly, in the case of ITO, after being deposited on a substrate such as glass or plastic, it is crystallized through heat treatment, and the crystallized ITO is used at ambient temperature. In this case, ITO has a low resistivity value. Accordingly, when manufacturing a device using an ITO thin film manufactured by the above-described method, the evaluation of the device's characteristics due to the change in resistivity depending on the process temperature used is being pointed out as a problem.

The heat treatment process of such ITO thin films is mainly carried out at a temperature of 200℃ or higher. However, if the heat treatment is carried out below 200℃ to secure the sustainability of the process, such as reducing process costs, there is a disadvantage in that the crystallization of the thin film is insufficient, resulting in reduced thermal stability. In this case, it can cause serious damage to the hydrogen-doped amorphous silicon (a-Si:H), which is used as a core structure during the operation of the solar cell, and this causes a problem of reduced energy efficiency.

That is, ITO, which is currently used in solar cell materials that are in the spotlight as a green energy business, has the disadvantages of low transparency and high light absorption in the long wavelength range used in solar cells, and especially, low electron mobility when heat-treated at low temperatures below 200℃, making it difficult to apply to high-efficiency solar cells. To overcome this, composite oxides with various ratios have been developed, but there is a problem that although the electrical conductivity is excellent when heat-treated at low temperatures, the electron mobility characteristics decrease.

Accordingly, much research has been conducted recently to increase the efficiency of solar cells, and among these, research on minimizing damage to hydrogen-doped amorphous silicon (a-Si:H), which is used as the core structure of solar cells, and on methods for manufacturing more efficient transparent electrodes even at lower process temperatures is in the spotlight.

Accordingly, the present invention aims to provide a transparent conductive film having high electron mobility, low carrier concentration, very high transparency, low resistivity, and excellent electrical conductivity to increase the cell efficiency of an HJT (Hetero-Junction-Technology) solar cell.

Republic of Korea Patent Publication No. 10-1240197 (2013.03.06.) Republic of Korea Patent Publication No. 10-1264111 (May 14, 2013) U.S. Patent No. 9,336,920 (May 10, 2016)

The present invention provides a transparent conductive oxide and a transparent conductive film which have a stable resistivity value according to the process temperature as a material for electrodes of various types of flat displays and solar cells, exhibit high electron mobility at a relatively low temperature, have excellent transmittance in a long wavelength range with a lower carrier concentration than conventional ITO, and exhibit low absorption.

The present invention provides an oxide having a uniform particle size distribution of 50 nm or less, which can be formed by a co-precipitation method, an ultrafine synthetic powder, and which has a high heat treatment driving force, thereby functioning as a target for a high-concentration transparent conductive film with excellent densification, and a method for manufacturing a sintered body and/or a sputtering target using the oxide.

The present invention provides a transparent conductive film characterized in that it includes 0.01 to 10 wt% of an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound; and 90 to 99.99 wt% of indium tin oxide, based on the total weight of the transparent conductive film.

The above additive may include at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ).

The above transparent conductive film may have a light transmittance of 85 to 100%.

The above transparent conductive film may have a resistivity of 3.0×10 ^-4 to 5.5×10 ^-4 Ωcm.

The above transparent conductive film can have a carrier concentration of 2.80×10 ²⁰ to 3.20×10 ²⁰ cm ^-3 .

In addition, the present invention provides a transparent conductive film target characterized in that it includes 0.01 to 10 wt% of an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound; and 90 to 99.99 wt% of indium tin oxide, based on the total weight of the transparent conductive film target.

The above additive may include at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ).

In addition, the present invention provides a method for manufacturing a target for a transparent conductive film, comprising the steps of: manufacturing a solution containing an indium precursor and a tin precursor; adding an alkaline compound to the solution to form ITO; forming a molded body by mixing an additive containing at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO; and heat-treating the molded body to manufacture a sputtering target.

The step of forming ITO by adding an alkaline compound to the solution may include the steps of: adding an alkaline compound to the solution; reacting the solution with the alkaline compound added at 20 to 80° C. for 15 to 25 hours to form a precipitate; washing and drying the precipitate; and heat-treating the precipitate at 600 to 900° C. for 1.5 to 2.5 hours to form ITO.

The step of forming a molded body by mixing an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO may include the steps of: forming a first mixture by mixing an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO; forming a second mixture by mixing a binder into the first mixture; forming a slurry by pulverizing the second mixture; and forming a molded body by pressurizing the slurry.

The step of manufacturing a sputtering target by heat-treating the above-mentioned molded body may be characterized by heat-treating the above-mentioned molded body at 1,400 to 1,800°C for 10 to 20 hours.

The present invention provides a transparent conductive film, a target for a transparent conductive film, and a method for manufacturing the same, wherein the transparent conductive film has the advantages of high electron mobility, electrical conductivity equivalent to or higher than that of ITO, and low carrier density, thereby allowing high light (particularly visible light) transmittance even when heat-treated at a relatively low temperature by adding a metal oxide to indium tin oxide (ITO).

Figure 1 is a graph showing the results of measuring the electron mobility of transparent conductive films provided as comparative examples and examples.
Figure 2 is a graph showing the results of measuring the carrier concentration of transparent conductive films provided as comparative examples and examples.
Figure 3 is a graph showing the results of resistivity measurements of transparent conductive films provided as comparative examples and examples.

Hereinafter, a transparent conductive film, a target for a transparent conductive film, and a manufacturing method thereof according to the present invention will be described in detail. The drawings introduced below are provided as examples so that those skilled in the art can sufficiently convey the spirit of the present invention. Therefore, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be illustrated in an exaggerated manner to clarify the spirit of the present invention. At this time, if there is no other definition for the technical and scientific terms used in the present invention, they have the meaning commonly understood by a person having ordinary skill in the art to which this invention belongs, and a description of well-known functions and configurations that may unnecessarily obscure the gist of the present invention in the following description and the accompanying drawings will be omitted.

In the case of conventional synthesis of indium tin oxide (ITO), if heat treatment is performed at a low temperature, it tends to not be properly crystallized, resulting in high resistivity, low transmittance, and poor thermal stability. The present invention provides a transparent conductive film to overcome these problems of conventional inventions.

[Transparent film]

The present invention provides a transparent conductive film characterized in that it includes 0.01 to 10 wt% of a metal oxide additive and 90 to 99.99 wt% of indium tin oxide based on the total weight of the transparent conductive film.

The above metal oxide additive is represented by a chemical formula of M _x O _y , and may specifically include at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound. That is, in the chemical formula M _x O _y , the metal element M is preferably at least one selected from cerium, gallium, and tantalum, x may be a real number in the range of 1 to 2, and y may be a real number in the range of 2 to 5. More specifically, the additive may include at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ).

Indium of the above transparent conductive film and M, a metal element of the above additive, exist in the form of trivalent cations, and the ionic radius and relative size of each are as follows. Here, the relative size means the ratio of the ionic radius of each metal element ion compared to the indium ion, which is the main component of the transparent conductive film.

Metal ion Ionic radius (Å) Relative size Indium ion (In ³⁺ ) 0.80 1.00 Cerium ion (Ce ³⁺ ) 1.01 1.26 Gallium ion (Ga ³⁺ ) 0.62 0.78 Tantalum ion (Ta ³⁺ ) 0.72 0.90

In Table 1, it can be confirmed that the ionic radius of cerium ion is about 26% larger than that of indium ion, while that of gallium ion and tantalum ion is about 10% and 22% smaller, respectively. According to the present invention, by adding the metal element having an ionic radius different from that of indium, solid solution between the mixture constituting the transparent conductive film can be more efficiently achieved, electron mobility can be increased, and carrier concentration and resistivity can be reduced. In addition, when such a metal ion is included, the transmittance can be maintained high at 85% or higher even when heat-treated at a lower temperature than that of a conventional indium tin oxide-based transparent conductive film. At this time, the upper limit of the transmittance of the transparent conductive film can be 95% or less, and preferably can be 100% or less.

At this time, gallium ions or tantalum ions having smaller ionic radii than indium can be particularly effective in solidifying the mixture when heat-treated at a lower temperature than before. However, in this case, as the content of gallium ions or tantalum ions increases, defects in the lattice structure increase, which may result in a somewhat higher resistivity.

In addition, in the case of cerium ions having a larger ionic radius than indium, the electron mobility of transparent conductive films can be increased, carrier concentration can be reduced, and solid solution between mixtures can be positively affected at low heat treatment temperatures by intentionally inducing deformation and defects in the lattice of tin oxide.

Accordingly, the transparent conductive film is characterized by including indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), and at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ). At this time, the specific ratio of each oxide may be such that indium oxide (In ₂ O ₃ ) is 85.0 to 99.0 wt%, tin oxide (SnO ₂ ) is 0.99 to 5.0 wt%, and at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ) is 0.01 to 10.0 wt% relative to the total weight of the transparent conductive film.

Therefore, by satisfying the above composition, the transparent conductive film can have a light transmittance of 85 to 100%, an electron mobility of 40 to 55 cm ² V ^-1 s ^-1 , a carrier concentration of 2.80×10 ²⁰ to 3.20×10 ²⁰ cm ^-3 , and a resistivity of 3.0×10 ^-4 to 5.5×10 ^-4 Ωcm.

In addition, it is preferable to include 95.0 to 98.0 wt% of indium oxide (In ₂ O ₃ ), 1.9 to 3.8 wt% of tin oxide (SnO ₂ ), and 0.1 to 1.2 wt% of at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ).

By satisfying the above composition, preferably, the transparent conductive film can have a light transmittance of 85 to 100%, an electron mobility of 42 to 55 cm ² V ^-1 s ^-1 , a carrier concentration of 2.85 × 10 ²⁰ to 3.15 × 10 ²⁰ cm ^-3 , and a resistivity of 3.0 × 10 ^-4 to 4.0 × 10 ^-4 Ωcm.

In addition, more preferably, a particularly preferable composition for satisfying the properties of the transparent conductive film described above is preferably included including 96.0 to 96.7 wt% of indium oxide (In ₂ O ₃ ), 2.8 to 3.2 wt% of tin oxide (SnO ₂ ), and 0.5 to 0.8 wt% of at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ). At this time, electron mobility, carrier concentration, and resistivity can be exhibited in an optimal state.

By satisfying the above composition, preferably, the transparent conductive film can have a light transmittance of 85 to 100%, an electron mobility of 48 to 55 cm ² V ^-1 s ^-1 , a resistivity of 3.0×10 ^-4 to 3.8×10 ^-4 Ωcm, and a carrier concentration of 2.80×10 ²⁰ to 3.00×10 ²⁰ cm ^-3 .

The above transparent conductive film is used particularly in solar cells, flat panel displays, and photosensitive elements, and for this purpose, it is preferable that the light transmittance be at least 85% or higher in the visible light wavelength range. However, if the composition of the above transparent conductive film deviates from the above, crystallization cannot be achieved at low temperatures, and the resulting lattice structure defects may increase the resistivity. In addition, light scattering due to the defects may cause negative effects such as an increase in carrier concentration and a decrease in transmittance. This tendency may appear particularly when the additive is included in an amount less than or exceeding the above-described range, resulting in the occurrence of lattice defects.

[Target for transparent conductive film]

The present invention provides a transparent conductive film target, characterized in that it includes 0.01 to 10 wt% of a metal oxide additive and 90 to 99.99 wt% of indium tin oxide based on the total weight of the transparent conductive film target.

The above metal oxide additive is represented by the chemical formula M _x O _y , and more specifically may include at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound.

The above additive may include at least one selected from the group consisting of cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ).

The material composition and characteristics of the target for the transparent conductive film are the same as those of the transparent conductive film, and redundant description is omitted.

[Target for transparent conductive film, manufacturing method of transparent conductive film]

The present invention provides a method for manufacturing a target for a transparent conductive film, comprising the steps of: preparing a solution containing an indium precursor and a tin precursor; adding an alkaline compound to the solution to form ITO; forming a molded body by mixing an additive containing at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO; and heat-treating the molded body to manufacture a sputtering target.

The above indium precursor and tin precursor are not particularly limited as long as they are used in the technical field of the present invention, but are preferably metal alkoxide precursors. More specifically, the indium precursor and tin precursor may include, for example, indium nitrate (In(NO ₃ ) ₃ ), indium chloride (InCl ₃ ), tin chloride (SnCl ₂ ), or tin sulfide (SnS).

At this time, it is preferable that the pH of the solution containing the indium precursor and tin precursor be adjusted to 1 to 4. If the pH of the solution is outside this range, problems such as the reaction speed of the solution becoming too slow may occur, so it is preferable to maintain the above-mentioned range. As a regulator for adjusting pH, any regulator used to adjust the pH of a typical aqueous solution can be used without restriction.

The step of forming ITO by adding an alkaline compound to the solution may include the steps of: adding an alkaline compound to the solution; reacting the solution with the alkaline compound added at 20 to 80° C. for 15 to 25 hours to form a precipitate; washing and drying the precipitate; and heat-treating the precipitate at 600 to 900° C. for 1.5 to 2.5 hours to form ITO.

At this time, it is preferable that the pH of the solution to which the alkaline compound is added is 7 to 10. In addition, it is preferable to form a precipitate by reacting at 20 to 80°C for 15 to 25 hours while maintaining the pH within the above range. By satisfying such pH conditions, temperature, and reaction time, the process in which the indium precursor and the tin precursor form a precipitate through a co-precipitation reaction can be promoted. If the pH is lower than the above range, crystallization is difficult, which inhibits the formation of a precipitate, so the yield may decrease, and if it exceeds the above range, the time required for the washing and filtration processes increases, which is not preferable.

At this time, when the reaction is performed at 30 to 50℃ for 15 to 25 hours while maintaining the pH within the above-mentioned range, the formation of the precipitate can be most promoted. If the temperature of the solution exceeds the above-mentioned range during the precipitate formation process, the reaction time becomes very long if the temperature is maintained below the above-mentioned range, and if it is maintained above the above-mentioned temperature, excessive growth of the primary particles may occur, making it difficult to manufacture the precipitate into a fine powder having an average particle size of 50㎚ or less, which may be disadvantageous for subsequent processing. In order to facilitate subsequent processing as a transparent conductive film, it is preferable that the precipitate has an average particle size of primary particles of 10 to 50㎚.

Next, after obtaining the precipitate, it can be filtered and separated, and then washed and dried. The precipitate is obtained in the form of a metal hydroxide, and can be oxidized and converted into indium tin oxide by heat treatment.

Filtration and separation of the above sediment can be performed using, for example, a filter press or a centrifuge, but is not necessarily limited thereto.

The washing of the above sediment can be performed using any hydrophilic solvent commonly used in the art, without limitation, and for example, ultrapure water or ethanol can be used.

Drying of the above sediment may be accomplished using a method such as hot air drying, and it is preferable to control the temperature within the range of 80 to 200°C.

The dried precipitate can be heat-treated at a temperature of 600 to 1,000°C to decompose and remove moisture and salts remaining in the precipitate, thereby forming indium tin oxide (ITO). At this time, if the heat treatment is performed below the temperature range described above, the salt chemically bonded to the precipitate will not completely volatilize, and if the heat treatment is performed above the range described above, sintering (growth of particle size) between primary particles will occur, which is not desirable. Normally, sintering of particles is not a big problem, but in the present invention, adding an additive to the indium tin oxide that has undergone such heat treatment and uniformly distributing it is an important factor in the physical performance of the transparent conductive film, and therefore, it may be difficult to provide the transparent conductive film that the present invention intends to provide as a result. In addition, if the primary particles are sintered to form secondary particles, much greater energy is required to pulverize the secondary particles, and therefore, considering the subsequent process, it is not desirable for the primary particles to be sintered. At this time, it is recommended that the heat treatment of the above sediment be performed for 1 to 3 hours.

Indium tin oxide (hereinafter referred to as ITO), which has undergone drying and heat treatment, is then mixed with the above-described additives and molded and heat-treated. At this time, the secondary particles of the ITO may have an average particle diameter of 1.0 to 10.0 ㎛ and a specific surface area of 10 to 30 m ² g ^-1 . If the average particle diameter of the secondary particles of the indium tin oxide is larger than 10 ㎛ or the specific surface area is smaller than 10 m ² g ^-1 , it becomes very difficult to form a transparent conductive film with a high-density and dense structure, and if the average particle diameter is smaller than 1 ㎛ or the specific surface area is larger than 30 m ² g ^-1 , there is a concern that cracks may occur during molding, and even during subsequent heat treatment, excessive shrinkage may increase internal residual stress, which may cause cracks to occur.

The step of forming a molded body by mixing an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO may include the steps of: forming a first mixture by mixing an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO; forming a second mixture by mixing a binder into the first mixture; forming a slurry by pulverizing the second mixture; and forming a molded body by pressurizing the slurry.

Since the mixing ratio of the above ITO and the above additive follows the material composition of the transparent conductive film described above, redundant explanation is omitted.

The second mixture may be manufactured by forming the first mixture, mixing a binder into the first mixture, coating the particle surface with the binder, and then drying the mixture. The binder may be any commonly used binder, such as polyvinyl alcohol, without limitation. By performing powder processing using such a binder, the molding density and sintering density can be increased when molding a transparent conductive film target with the second mixture.

The above second mixture may be ground by a dry or wet method that is commonly used. For example, a method such as a wet ball mill may be used.

More specifically, the wet ball milling is performed within 20 hours, and the second mixture is ground into powder having an average particle size of 0.25 to 1.0 μm, so that 90% or more of the final obtained powder has an average particle size of 1.0 μm or less.

The powder formed in this manner can be formed into a molded body through a CIP (Cold Isostatic Press) method, etc. By controlling the average particle size and specific surface area of the powder through heat treatment, binder mixing, grinding, etc. as described above, the density of the molded body is very high, approximately 58 to 62% of the theoretical density of the sputtering target after sintering is completed.

The above binder can be used without limitation on its type as long as it does not excessively inhibit the transmittance of the transparent conductive film, as long as it is commonly used in the art. For example, polyvinyl alcohol (PVA) can be used. In order for the transparent conductive film to satisfy the above-described physical properties such as transmittance, electron mobility, carrier concentration, and resistivity, it is preferable to mix 0.6 to 1.2 parts by weight of the binder with respect to 100 parts by weight of the powder. If the content of the binder is lower than this, the shape stability and physical strength of the transparent conductive film may deteriorate and become unstable, and if the content of the binder is higher than this, it may have a negative effect on the electrical properties such as electron mobility, carrier concentration, and resistivity.

Thereafter, the step of heat-treating the molded body to manufacture a sputtering target may be characterized by heat-treating the molded body at 1,400 to 1,800°C for 10 to 20 hours. At this time, it is preferable that the heat treatment is performed at a temperature of 1,450 to 1,650°C for 10 to 20 hours.

The sputtering target manufactured as described above can have a relative density of 98% or more as measured by the Archimedes method. This relative density is due to the formation of a precipitate composed of primary particles having an average particle diameter of 10 to 50 nm as described above, and the precipitate has a high sintering driving force, so that a high-density target with excellent densification can be manufactured.

In addition, the sputtering target manufactured therefrom can form a uniform transparent conductive film that does not cause phase separation due to high temperature and thus does not cause cracks or nodules during sputtering. In addition, a target for a transparent conductive film that is thermally and chemically stable and has excellent electrical conductivity and a surface resistivity of 1.0×10 ^-3 or less, preferably 6.0×10 ^-4 or less, more preferably 4.0×10 ^-4 or less can be manufactured.

The target for a transparent conductive film manufactured as described above is loaded into a sputtering device, and the initial vacuum level in the chamber of the sputtering device is adjusted to 0.1×10 ^-6 torr or less, and then the gas concentration and deposition pressure are adjusted to perform sputtering at room temperature, thereby forming a transparent conductive film.

Next, the transparent conductive film can be further heat-treated at a temperature of 100 to 300°C. At this time, the heat-treatment atmosphere may be oxygen, nitrogen, a vacuum, or an air atmosphere, but is not necessarily limited thereto, and is preferably an air atmosphere that can easily create a process environment. In addition, when the heat-treatment is preferably performed at a temperature of 150 to 250°C, and more preferably at a temperature of 150°C or more and less than 200°C, the physical performances of the transparent conductive film, such as electron mobility, carrier concentration, and resistivity, can be most optimized.

Hereinafter, the transparent conductive film, the target for the transparent conductive film, and the manufacturing method thereof according to the present invention will be described in more detail through examples. However, the following examples are only a reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is only for the purpose of effectively describing specific embodiments and is not intended to limit the present invention. In addition, the unit of additives not specifically described in the specification may be weight percent.

[Manufacturing examples and comparative examples]

Tin hydroxide (Sn(OH) ₂ ) was added to an indium nitrate (In( _NO3 ) ₃ ) aqueous solution and stirred at 50°C for 3 hours to obtain a precursor aqueous solution having a pH of 3.0. Then, _NH3OH aqueous solution was added to the precursor aqueous solution to adjust the pH to 9.0, and the mixture was reacted at 40°C for 20 hours to produce indium tin hydroxide. The precipitated indium tin hydroxide precipitate was separated, washed three times with ultrapure water, and dried with hot air at 120°C. Next, the dried powder was put into an electric furnace and heat-treated (calcined) at 750°C for ₂ hours to obtain indium oxide ( _In2O3 ) and tin oxide ( _SnO2 ) powders. The average particle size of the indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₂ ) powders was observed to be uniformly distributed at 3 to 4 μm. In addition, the specific surface area of the indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₂ ) powders was measured using BET, and was found to be 12 m2/g.

The additives, cerium oxide (CeO ₂ ), gallium oxide (Ga ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ), were manufactured by Deoksan Chemical with a purity of 99.99% or higher and an average particle size of less than 10㎛.

Composition (weight%) Indium oxide
(In ₂ O ₃ ) Tin oxide
(SnO ₂ ) cerium oxide
(CeO ₂ ) gallium oxide
(Ga ₂ O ₃ ) Tantalum oxide
(Ta ₂ O ₅ ) Comparative Example 1 99 1 - - - Comparative Example 2 97 3 - - - Comparative Example 3 95 5 - - - Comparative Example 4 90 10 - - - Comparative Example 5 99 1 - - - Comparative Example 6 98 2 - - - Comparative Example 7 97 3 - - - Comparative Example 8 95 5 - - - Comparative Example 9 90 10 - - - Example 1 98.901 0.999 0.1 - - Example 2 98.703 0.997 0.3 - - Example 3 98.505 0.995 0.5 - - Example 4 98.208 0.992 0.8 - - Example 5 98.010 0.990 1.0 - - Example 6 97.812 0.988 1.2 - - Example 7 97.902 1.998 0.1 - - Example 8 97.706 1.994 0.3 - - Example 9 97.510 1.990 0.5 - - Example 10 97.216 1.984 0.8 - - Example 11 97.020 1.980 1.0 - - Example 12 96.824 1.976 1.2 - - Example 13 96.903 2.997 0.1 - - Example 14 96.709 2.991 0.3 - - Example 15 96.515 2.985 0.5 - - Example 16 96.224 2.976 0.8 - - Example 17 96.030 2.970 1.0 - - Example 18 95.836 2.964 1.2 - - Example 19 94.905 4.995 0.1 - - Example 20 94.715 4.985 0.3 - - Example 21 94.525 4.975 0.5 - - Example 22 94.240 4.960 0.8 - - Example 23 94.050 4.950 1.0 - - Example 24 93.860 4.940 1.2 - - Example 25 96.983 2.917 - 0.1 - Example 26 96.789 2.911 - 0.3 - Example 27 96.595 2.905 - 0.5 - Example 28 96.303 2.897 - 0.8 - Example 29 96.109 2.891 - 1.0 - Example 30 96.953 2.947 - - 0.1 Example 31 96.809 2.891 - - 0.3 Example 32 96.615 2.886 - - 0.5 Example 33 96.323 2.877 - - 0.8 Example 34 96.129 2.871 - - 1.0

The mixed powder prepared according to the composition described in Table 2 was placed in a dispersion pot, and wet milling was performed using water as a medium. At this time, YTZ 0.3 mm balls (zirconia) were used as the crushing and dispersion medium, and the particle size after milling was controlled to 0.35 to 0.45 μm, and a binder (polyvinyl alcohol) was added together to the pot to produce a mixed slurry. At this time, the amount of the binder was adjusted to 0.8 parts by weight per 100 parts by weight of the powder. Thereafter, the mixed slurry was spray dried to obtain a spherical powder composed of secondary particles having an average particle size of 50 to 80 μm, and this powder was pressed into a mold to produce a thin film-shaped molded body having a thickness of 100 nm. Thereafter, the molded body was put into an electric furnace, heated to 1,600°C, and then maintained for 12 hours to perform heat treatment (sintering).

The density of the sintered body (target for transparent conductive film) manufactured as above was measured by the Archimedes method and was 7.08 to 7.12 gcm ^-3 , and the surface resistivity was measured to be 2.0×10 ^-4 Ωcm or less.

Next, the transparent conductive film target was mounted on a DC magnetron sputter, and the initial vacuum inside the chamber was adjusted to 1.0×10 ^-6 torr or less, and then a thin film was formed on a glass substrate with a thickness of 100 nm at room temperature, and this was heat-treated at 190°C for 30 minutes in an air atmosphere. However, Comparative Examples 1 to 4 were heat-treated at 200°C for 30 minutes. The electron mobility, carrier concentration, and resistivity of the transparent conductive films obtained therefrom were confirmed by Hall measurement, and the results are shown in Table 3.

Hall measurement results Electron mobility
[cm ² V ^-1 s ^-1 ] carrier concentration
×10 ²⁰ [cm ^-3 ] Resistivity
×10 ^-4 [Ωcm] Comparative Example 1 48.0 2.87 4.08 Comparative Example 2 43.0 3.24 3.30 Comparative Example 3 45.0 3.85 3.02 Comparative Example 4 39.0 3.58 4.24 Comparative Example 5 35.0 2.84 5.80 Comparative Example 6 32.3 2.96 5.40 Comparative Example 7 32.7 3.12 4.87 Comparative Example 8 28.6 3.27 5.90 Comparative Example 9 27.5 3.24 6.20 Example 1 45.0 2.87 4.12 Example 2 46.6 2.95 4.20 Example 3 47.8 2.93 4.38 Example 4 49.2 3.01 4.42 Example 5 48.4 3.11 4.82 Example 6 49.0 3.32 4.46 Example 7 44.2 2.96 3.76 Example 8 47.2 2.89 3.94 Example 9 47.6 2.91 3.94 Example 10 46.4 2.97 3.96 Example 11 48.3 3.05 3.71 Example 12 46.3 3.01 3.76 Example 13 42.3 3.04 3.82 Example 14 45.4 3.04 3.86 Example 15 52.4 3.06 3.64 Example 16 51.7 2.97 3.38 Example 17 52.4 3.04 3.63 Example 18 51.6 3.04 3.82 Example 19 38.6 3.27 4.60 Example 20 42.4 3.12 4.87 Example 21 44.5 3.12 5.12 Example 22 44.4 3.28 5.32 Example 23 46.8 3.12 5.32 Example 24 45.4 3.05 5.45 Example 25 44.4 2.98 4.12 Example 26 47.6 2.87 3.94 Example 27 49.0 3.04 3.94 Example 28 49.0 2.98 3.78 Example 29 51.8 3.00 3.89 Example 30 45.0 3.08 3.83 Example 31 46.2 3.04 3.64 Example 32 48.4 3.00 3.42 Example 33 50.0 3.12 3.42 Example 34 48.9 3.04 3.68

In Fig. 1, in the case of the comparative examples, the electron mobility tended to decrease as the tin content increased overall. In addition, the comparative examples 1 to 4 heat-treated at 200°C showed higher electron mobility overall than the comparative examples 5 to 9 heat-treated at 190°C. That is, in the case of the comparative examples composed of only indium oxide and tin oxide, it can be confirmed that the crystallinity increases only when the heat treatment temperature is higher (200°C).

On the other hand, in the case of Examples 1 to 24 to which cerium oxide was added, there was some deviation depending on the change in content, but the electron mobility was at least 35.0 cm ² V ^-1 s ^-1 or higher and up to about 52.4 cm ² V ^-1 s ^-1 , showing an overall higher tendency than the comparative examples.

In addition, in the case of Examples 25 to 29 with added gallium and Examples 30 to 34 with added tantalum, the electron mobility showed a tendency to gradually increase as the gallium content increased, and it could be confirmed that the electron mobility was high, at least 44.0 cm ² V ^-1 s ^-1 or higher and up to about 51.8 cm ² V ^-1 s ^-1 .

Next, in Fig. 2, Comparative Examples 1 and 5 have relatively small carrier concentrations, but Comparative Examples 2 to 4 and Comparative Examples 6 to 9, where the tin oxide content is high, show a tendency for the carrier concentration to increase rapidly. The tendency for the carrier concentration to increase when the concentration of tin oxide or added metal oxide (M _x O _y ) increases was similarly observed in the Examples, but in the Comparative Examples, the change in carrier concentration due to the increase in the tin oxide concentration was particularly rapid, showing a very high carrier concentration of up to 3.80×10 ²⁰ cm ^-3 .

On the other hand, in Examples 1 to 24 in which cerium oxide was added, the tendency for the increase in carrier concentration was alleviated compared to the comparative examples, and in particular, in Examples 7 to 12 in which the content of tin oxide in the transparent conductive film was 1.998 to 1.976 wt%, it was confirmed that this tendency for the increase was suppressed.

In addition, in the case of Examples 25 to 29 in which gallium oxide was added, the carrier concentration was generally low, ranging from 2.87×10 ²⁰ to 3.04×10 ²⁰ cm ^-3 , although there was no consistent trend. In the case of Examples 30 to 34 in which tantalum was added, the carrier concentration was generally low, ranging from 3.00×10 ²⁰ to 3.12×10 ²⁰ cm ^-3 , although there was no consistent trend.

Lastly, in the case of Comparative Examples 1 to 9, it can be confirmed that the resistivity of Comparative Examples 5 to 9, which were heat-treated at 190°C, is relatively higher than that of Comparative Examples 1 to 4, which were heat-treated at 200°C.

Examples 1 to 34 showed that the range of change in resistivity according to the content of tin or added metal was smaller than that of the comparative examples, and the resistivity values were also generally low.

Although the present invention has been described through specific matters and limited examples as above, these have been provided only to help with the overall understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations from this description.

Therefore, the idea of the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims described below as well as the claims are included in the scope of the idea of the present invention.

Claims (12)

Regarding the total weight of the transparent conductive film,
0.01 to 10 wt% of an additive comprising at least one selected from the group consisting of cerium oxide (CeO ₂ ) and gallium oxide (Ga ₂ O ₃ ); and
Containing 90 to 99.99 wt% of indium tin oxide;
The above transparent conductive film is characterized by having an electron mobility of 40 to 55 cm ² V ^-1 s ^-1 , a resistivity of 3.0×10 ^-4 to 5.5×10 ^-4 Ωcm, and a carrier concentration of 2.80×10 ²⁰ to 3.20×10 ²⁰ cm ^-3 . delete delete In the first paragraph,
The above transparent conductive film is characterized by a light transmittance of 85 to 100%. delete delete Regarding the total weight of the target for the transparent conductive film,
0.01 to 10 wt% of an additive comprising at least one selected from the group consisting of cerium oxide (CeO ₂ ) and gallium oxide (Ga ₂ O ₃ ); and
Containing 90 to 99.99 wt% of indium tin oxide;
A target for a transparent conductive film, characterized in that the electron mobility is 40 to 55 cm ² V ^-1 s ^-1 , the resistivity is 3.0×10 ^-4 to 5.5×10 ^-4 Ωcm, and the carrier concentration is 2.80×10 ²⁰ to 3.20×10 ²⁰ cm ^-3 . delete A step of preparing a solution containing an indium precursor and a tin precursor;
A step of forming ITO by adding an alkaline compound to the above solution;
A step of forming a molded body by mixing an additive including at least one selected from the group consisting of cerium oxide (CeO ₂ ) and gallium oxide (Ga ₂ O ₃ ) into the ITO; and
A method for manufacturing a target for a transparent conductive film, characterized by including a step of heat-treating the above-mentioned molded body to manufacture a target having an electron mobility of 40 to 55 cm ² V ^-1 s ^-1 , a resistivity of 3.0×10 ^-4 to 5.5×10 ^-4 Ωcm, and a carrier concentration of 2.80×10 ²⁰ to 3.20×10 ²⁰ cm ^-3 . In Article 9,
The step of forming ITO by adding an alkaline compound to the above solution is:
A step of adding an alkaline compound to the above solution;
A step of forming a precipitate by reacting a solution to which the alkaline compound is added at 20 to 80°C for 15 to 25 hours;
A step of washing and drying the above sediment; and
A method for manufacturing a target for a transparent conductive film, characterized by including a step of forming ITO by heat-treating the above-mentioned precipitate at 600 to 900°C for 1.5 to 2.5 hours. In Article 9,
The step of forming a molded body by mixing an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO is as follows.
A step of forming a first mixture by mixing an additive including at least one selected from the group consisting of a cerium compound, a gallium compound, and a tantalum compound into the ITO;
A step of forming a second mixture by mixing a binder into the first mixture;
a step of forming a slurry by crushing the second mixture; and
A method for manufacturing a target for a transparent conductive film, characterized by comprising a step of forming a molded body by pressurizing the above slurry. In Article 9,
The step of manufacturing a sputtering target by heat treating the above-mentioned molded body is as follows:
A method for manufacturing a target for a transparent conductive film, characterized in that the molded body is heat treated at 1,400 to 1,800°C for 10 to 20 hours.