Method for producing oxide sputtering target and method for forming transparent conductive oxide film
By controlling the sintering temperature and optimizing the oxygen flow, the expansion and cracking problems of In-Ge-O sputtering targets were solved, and IGO thin films suitable for low-temperature deposition were prepared, which improved the electrical and optical performance of solar cells and increased cell efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KV MATERIALS CO LTD
- Filing Date
- 2025-01-20
- Publication Date
- 2026-06-30
AI Technical Summary
When preparing In-Ge-O oxide sputtering targets, the liquid phase and high vapor pressure of GeO2 cause volatilization, resulting in defects such as expansion and cracks, which affect the target density and film quality. Furthermore, ITO films deposited at high temperatures may damage solar cells.
By controlling the sintering temperature range and oxygen flow rate, and optimizing the oxygen inflow, In-Ge-O sputtering targets were prepared to avoid the volatilization and cracking of GeO2, and IGO thin films were formed by low-temperature deposition.
A dense In-Ge-O sputtering target was successfully prepared at low temperature, forming a transparent conductive oxide thin film with excellent electrical and optical properties, thereby improving the efficiency of solar cells.
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Figure CN122301533A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing an oxide sputtering target and a method for forming a transparent conductive oxide thin film. More specifically, it relates to a method for preparing an oxide sputtering target based on In, Ge, and O components and a method for forming a transparent conductive oxide thin film using the prepared target. Background Technology
[0002] Transparent conductive oxide (TCO) films are thin films with low resistance and high transmittance, and are used in a variety of fields. Particularly in the field of solar cells, TCO films applied to solar cells form films with low resistance, high transmittance, and high mobility, allowing light received from the sun to be effectively transmitted into the solar cell unit, and enabling photoelectrons generated from the unit to move smoothly, thereby improving the efficiency of the solar cell unit.
[0003] TCO thin films are widely used as the top and bottom electrodes in solar cells. Recently, in order to overcome the limitations of single-junction solar cells, multi-junction solar cells have been proposed, which combine two or more solar cells that absorb light from different regions. In these multi-junction solar cells, TCO thin films are also used as an intermediate layer connecting the top and bottom cells.
[0004] Currently, the most widely used material for this type of TCO thin film is indium tin oxide (ITO), which exhibits excellent electrical and optical properties. To achieve these superior electrical and optical properties, ITO requires deposition processes or post-heat treatment at temperatures above 200°C. However, for solar cells, if ITO used as the top electrode is deposited at high temperatures, the layer deposited in the preceding processes may deform and become damaged, potentially leading to reduced solar cell efficiency. In particular, perovskites, which are attracting attention as next-generation solar cells, may degrade or decompose at temperatures above 200°C; therefore, ITO used as the top electrode and intermediate layer needs to be deposited at low temperatures. However, ITO deposited at low temperatures has a higher resistivity compared to ITO deposited at high temperatures or undergoing high-temperature post-heat treatment. Higher electrode resistivity reduces the fill power of the solar cell, resulting in decreased efficiency.
[0005] Therefore, there is a need for transparent conductive oxide thin films that possess excellent electrical and optical properties even when deposited at low temperatures, and IGO thin films based on In, Ge, and O compositions can be proposed to replace ITO thin films. However, swelling and internal or external cracks that occur during the preparation of sputtering targets for IGO film deposition reduce the density of the sputtering target and adversely affect the quality of the film formed using that sputtering target. Therefore, there is a need for a target preparation method that minimizes swelling and crack formation in the sputtering target to prepare a dense sputtering target. Summary of the Invention
[0006] The technical problem to be solved by the present invention is that, when sintering a mixed powder molded body containing In2O3 powder with a relatively high melting point (1,910°C) and GeO2 powder with a relatively low melting point (1,115°C), various defects are generated due to the volatilization of GeO2 due to its liquid phase and high vapor pressure during sintering at a temperature above the melting point of GeO2 (1,115°C). The technical problem to be solved is to prepare sputtering targets of In-Ge oxides that do not have defects caused by the volatilization of GeO2 by controlling the sintering atmosphere in the temperature range before and after GeO2 volatilization and optimizing the oxygen inflow according to the temperature range.
[0007] According to a first aspect of the present invention, a method for preparing an oxide sputtering target is provided, comprising the steps of: obtaining a mixture comprising a metal oxide; introducing the mixture into a sintering furnace; and sintering the mixture, wherein the step of sintering the mixture is performed as follows: simultaneously heating the mixture by introducing oxygen into the sintering furnace at a first flow rate; then further heating the mixture by introducing oxygen into the sintering furnace at a second flow rate; and then further heating the mixture by introducing oxygen into the sintering furnace at a third flow rate. The metal oxide is composed only of In₂O₃ and GeO₂, the first heating is performed until the sintering atmosphere reaches any temperature within the range of 1050°C to 1150°C, the second heating is performed until the sintering atmosphere reaches any temperature within the range of 1200°C to 1300°C, and the first flow rate and the third flow rate may be greater than the second flow rate.
[0008] According to some embodiments, the primary heating can be performed until the sintering atmosphere reaches any temperature within the range of 1050°C to 1150°C. According to some embodiments, the primary heating can be performed until the sintering atmosphere reaches 1100°C. According to some embodiments, the secondary heating can be performed until the sintering atmosphere reaches 1250°C.
[0009] According to some embodiments, the three heating cycles may be performed until the sintering atmosphere reaches 1450°C to 1550°C. According to some embodiments, the three heating cycles may be performed until the sintering atmosphere reaches 1500°C.
[0010] According to some embodiments, the first flow rate and the third flow rate can be per cubic meter of the sintering furnace. 3 The oxygen flow rate is 101L~608L per minute into the volume of the sintering furnace. According to some embodiments, the first flow rate and the third flow rate can be per cubic meter of oxygen per minute in the sintering furnace. 3 The oxygen flow rate is 152L~557L per minute into the volume of the sintering furnace. According to some embodiments, the first flow rate and the third flow rate can be per cubic meter of oxygen per minute in the sintering furnace. 3 The flow rate of oxygen flowing into the volume is 213L~456L per minute.
[0011] According to some embodiments, the second flow rate may be per 1m³ within the sintering furnace. 3 The flow rate of oxygen flowing into the volume is 0L to 50L per minute. According to some embodiments, the second flow rate may be per cubic meter of oxygen per 1m³ in the sintering furnace. 3 The flow rate of 0L of oxygen flowing into the volume per minute.
[0012] According to some embodiments, at least one of the primary heating, the secondary heating, and the tertiary heating can be performed simultaneously by raising the sintering atmosphere at a rate of 0.1°C / min to 0.5°C / min. According to some embodiments, at least one of the primary heating, the secondary heating, and the tertiary heating can be performed simultaneously by raising the sintering atmosphere at a rate of 0.2°C / min to 0.3°C / min.
[0013] According to a second aspect of the present invention, a method for forming a transparent conductive oxide thin film can be provided, wherein the oxide sputtering target is prepared by a method for preparing the oxide sputtering target. Attached Figure Description
[0014] Figure 1 This is a flowchart illustrating a method for preparing an oxide sputtering target according to an embodiment of the present invention.
[0015] Figure 2This is a graph showing the degree of thermal expansion of In-Ge oxides.
[0016] Figure 3 This is a graph showing the experimental results of Comparative Example 1.
[0017] Figure 4 and Figure 5 This is a graph showing the experimental results of Comparative Example 2.
[0018] Figures 6 to 8 This is a graph showing the experimental results of Comparative Example 3.
[0019] Figure 9 and Figure 10 This is a graph showing the experimental results of Comparative Example 4.
[0020] Figure 11 and Figure 12 This is a graph showing the experimental results of Example 1.
[0021] Figure 13 and Figure 14 This is a graph showing the experimental results of Example 2.
[0022] Figure 15 and Figure 16 This is a graph showing the experimental results of Example 3.
[0023] Figure 17 It is a graph comparing the optical properties of transparent conductive oxide films deposited at room temperature according to their composition.
[0024] Figure 18 This is a graph showing the results of XRD analysis on the crystal structure and phases of a transparent conductive film deposited at room temperature.
[0025] Figure 19 and Figure 20 This figure shows the results of SEM and AFM analysis of the surface shape of a transparent conductive film deposited at room temperature. Detailed Implementation
[0026] The embodiments of the present invention will be described in detail below.
[0027] <Preparation Methods of Sputtering Targets> This invention relates to the sintering of mixed powders containing In₂O₃ and GeO₂. Specifically, by controlling the environment within a temperature range during sintering, defects (cracks, swelling, etc.) that may occur during liquid-phase sintering due to the melting point difference between In₂O₃ and GeO₂ can be eliminated. This allows for the fabrication of complete In-Ge oxide sputtering targets with defect-free sintered bodies.
[0028] The preparation method of sputtering targets for In-Ge oxides can be realized based on the In, Ge, and O composition in oxide form.
[0029] Reference Figure 1 The method for preparing the sputtering target of the present invention may include the following steps: obtaining a mixture comprising metal oxides (S1); introducing the mixture into a sintering furnace (S2); and sintering the mixture in the sintering furnace (S3). Here, the metal oxides may consist only of In2O3 and GeO2. Here, "comprising" should be interpreted as an open-ended meaning, that is, it may contain other substances besides those explicitly mentioned, and "consisting of" should be interpreted as a closed-ended meaning, that is, it contains only the substances explicitly mentioned. That is, the mixture of the present invention may include other substances (e.g., binder components, etc.) besides metal oxides, but does not contain other metal oxides (e.g., SnO2, ZnO, etc.) besides In2O3 and GeO2. According to one embodiment, the target can be prepared by mixing In2O3 and GeO2 such that the GeO2 content is 3% to 5% by weight relative to the total content of In atoms, Ge atoms, and O atoms, and then sintering it.
[0030] When preparing sputtering targets for In-Ge oxides, sintering a mixture of In₂O₃ (with a relatively high melting point, 1,910°C) and GeO₂ (with a low melting point, 1,115°C) powders results in liquid-phase sintering due to the low melting point of GeO₂. This liquid-phase sintering causes various defects within the target material. In this invention, when sintering a mixture of In₂O₃ and GeO₂ powders, defects in the sintered body are removed by controlling the sintering environment within a specific temperature range, thereby producing a complete sintered body.
[0031] More specifically, in order to obtain a target material with a usable density by sintering the mixed powder, sintering at a temperature above 1300°C is empirically preferred. However, when GeO2 is sintered at temperatures above 1300°C, it becomes a liquid phase and vaporizes due to the high vapor pressure. This results in cracks or swelling phenomena within the sintered body. More specifically, the liquid GeO2 vaporizes very easily, creating empty spaces within the sintered body, thus causing cracks, or swelling phenomena due to gases failing to escape from the inside of the sintered body. In this invention, by controlling external oxygen near the temperature at which GeO2 becomes a liquid phase, it becomes easy to induce the movement of vaporized GeO2, thereby enabling the preparation of In-Ge based oxide sputtering targets without internal cracks or swelling phenomena.
[0032] In this invention, the step (S3) of sintering the mixture may include the following steps: heating the mixture by introducing oxygen into the sintering furnace at a first flow rate to heat the mixture once (S31); then, heating the mixture by introducing oxygen into the sintering furnace at a second flow rate to heat the mixture a second time (S32); subsequently, heating the mixture by introducing oxygen into the sintering furnace at a third flow rate to heat the mixture a third time (S33).
[0033] During the heating range of sintering In-Ge oxide molded bodies, an oxygen atmosphere is maintained, and it may be necessary to remove the oxygen atmosphere near the melting point of GeO2, 1115°C. According to some embodiments, the oxygen atmosphere can be removed and sintering can be performed in a temperature range of 1,000°C to 1,300°C to prepare sintered bodies without defects such as swelling and cracks.
[0034] In some embodiments, the heating process may be performed until the sintering atmosphere reaches any temperature within the range of 1000°C to 1150°C (e.g., before reaching 1000°C). In some of these embodiments, the heating process may be performed until the sintering atmosphere reaches any temperature within the range of 1050°C to 1150°C (e.g., before reaching 1050°C). In some of these embodiments, the heating process may be performed until the sintering atmosphere reaches 1100°C.
[0035] In some embodiments, secondary heating, performed with oxygen introduced into the sintering furnace removed or minimized, can be performed until the sintering atmosphere reaches any temperature in the range of 1200°C to 1300°C (e.g., up to 1300°C). That is, it can be performed from any temperature in the range of 1050°C to 1150°C until any temperature in the range of 1200°C to 1300°C is reached. In some embodiments of these embodiments, secondary heating can be performed until the sintering atmosphere reaches 1250°C.
[0036] In some embodiments, the three heating cycles may be performed until the sintering atmosphere reaches 1450°C to 1550°C. In some of these embodiments, the three heating cycles may be performed until the sintering atmosphere reaches 1500°C. Figure 2 This is a graph showing the degree of thermal expansion of In-Ge oxides. The horizontal axis represents the sintering temperature, and the vertical axis represents the length of the sintered body. As shown in the figure, it can be seen that at temperatures exceeding 1500°C, the sintered body hardly shrinks (i.e., the density of the sintered body hardly increases). Therefore, it can be concluded that sintering at an atmosphere temperature of 1450°C to 1550°C (for example, up to 1500°C) is effective.
[0037] In some embodiments, an atmospheric sintering furnace is used as the sintering furnace, and at least one of the primary and tertiary heating processes can be carried out in a sintering atmosphere every 1 m 3 10¹L~60⁸L of oxygen flows into the volume per minute (10¹min·m⁻¹) 3 ~608L / min·m 3 Simultaneous execution. In some of these embodiments, at least one of the first and third heatings can be performed every 1m of sintering atmosphere. 3 152L~557L of oxygen flows into the volume per minute (152L / min·m) 3 ~557L / min·m 3 Simultaneous execution. In some of these embodiments, at least one of the first and third heatings can be performed every 1m of sintering atmosphere. 3 213L~456L of oxygen flows into the volume per minute (213L / min·m 3 Up to 456 L / min·m 3 Simultaneously with the primary and tertiary heating processes, secondary heating is performed without the introduction of oxygen into the furnace, or if oxygen is introduced, it is introduced at a much smaller rate than that introduced into the sintering furnace during primary and tertiary heating. In some embodiments, secondary heating can be performed at a rate of 1 m³ / s of sintering atmosphere. 3 Oxygen flows into the volume at a rate of 0 L / min to 50 L / min (0 L / min·m3 ~50 L / min·m 3 Simultaneous execution. In some embodiments of these examples, secondary heating can be performed every 1m of sintering atmosphere. 3 It is executed while 0L of oxygen flows into the volume per minute (i.e., without introducing oxygen).
[0038] In some embodiments, at least one of the primary, secondary, and tertiary heating processes can be performed simultaneously by increasing the sintering atmosphere temperature at a rate of 0.1°C / min to 0.5°C / min. In some of these embodiments, at least one of the primary, secondary, and tertiary heating processes can be performed simultaneously by increasing the sintering atmosphere temperature at a rate of 0.2°C / min to 0.3°C / min.
[0039] The step (S1) of obtaining the mixture may include a step of shaping the mixture. Shaping can be achieved by powder metallurgy. For example, In2O3 powder and GeO2 powder are mixed in a specified ratio, or In2O3 powder and GeO2 powder are mixed in a specified ratio and then shaped by methods such as cold press, slip casting, filter press, cold isostatic press, gel casting, centrifugal sedimentation, and gravimetric sedimentation to obtain the mixture. The target material can then be prepared by sintering the mixture thus obtained. According to some embodiments, the In-Ge oxide sputtering target of the present invention can be shaped into various forms such as plate, disk, and rotary.
[0040] (Comparative Example 1) During the sintering of In-Ge oxide molded bodies, when external oxygen flows in throughout the entire heating range, the following occurs: Figure 3 The swelling phenomenon shown.
[0041] [Table 1]
[0042] (Comparative Example 2) When external oxygen inflow was removed within the temperature range of 750℃ to 1500℃, no swelling phenomenon occurred, but the following occurred: Figure 4 and Figure 5 The internal / external cracks are shown.
[0043] [Table 2]
[0044] (Comparative Example 3) During the sintering of the In-Ge oxide molded body, external oxygen inflow was removed in the temperature range of 750℃ to 1300℃, and the oxygen content was reduced to 101 L / min·m in the temperature range of 1300℃ to 1500℃. 3 The result is as follows: Figure 6 and Figure 7 As shown, no swelling occurred, but external cracks appeared, and as... Figure 8 As shown, the results of ultrasonic testing confirmed the presence of numerous internal cracks.
[0045] [Table 3]
[0046] (Comparative Example 4) To confirm the effect of oxygen concentration, the oxygen concentration was increased by 101 L / min·m in the temperature range of 1300℃ to 1500℃. 3 →456L / min·m 3 ),like Figure 9 and Figure 10 As shown, it was confirmed that some of the internal cracks were reduced.
[0047] [Table 4]
[0048] (Example 1) External oxygen inflow was removed within the temperature range of 1000℃ to 1300℃, such as Figure 11 As shown, no swelling or external cracking occurred. However, as... Figure 12 As shown, the ultrasonic examination results confirmed the presence of internal cracks within the sintered body, but this represents a significant improvement compared to removing the internal cracks caused by external oxygen inflow at the aforementioned 750℃~1300℃.
[0049] [Table 5]
[0050] (Example 2) The external oxygen inflow removal range was narrowed, and external oxygen inflow was removed within the temperature range of 1050℃ to 1300℃. Although... Figure 13 and Figure 14As shown, similar results were obtained to those in the 1000℃~1300℃ range, but it was confirmed that the internal cracks were further improved.
[0051] [Table 6]
[0052] (Example 3) To minimize the external oxygen inflow removal range, external oxygen inflow was removed within the temperature range of 1100℃ to 1250℃, thus achieving the following results: Figure 15 and Figure 16 The sintered body shown is a complete sintered body without the aforementioned defects.
[0053] [Table 7]
[0054] As a result, in order to suppress the volatilization of GeO2, an oxygen atmosphere was maintained to suppress the occurrence of cracks, and the oxygen supply was removed in the region near the melting point of GeO2 to suppress the occurrence of swelling, thereby obtaining a complete sintered body.
[0055] <Methods for forming transparent conductive oxide thin films> A transparent conductive oxide thin film can be formed by sputtering an oxide sputtering target prepared by the above-described method for preparing oxide sputtering targets.
[0056] The IGO thin films (thin films based on In, Ge, and O components) mentioned below are prepared by mixing In₂O₃ and GeO₂ to make the GeO₂ content 3% by weight relative to the total content of In, Ge, and O atoms, followed by sintering to prepare a target material, and then sputtering the target material. As a comparison, the ITO thin films are prepared by mixing In₂O₃ and SnO₂ to make the SnO₂ content 3% by weight relative to the total content of In, Sn, and O atoms, followed by sintering to prepare a target material, and then sputtering the target material. As a comparison, the IZO thin films are prepared by mixing In₂O₃ and ZnO to make the ZnO content 10% by weight relative to the total content of In, Zn, and O atoms, followed by sintering to prepare a target material, and then sputtering the target material.
[0057] Table 8 below shows the results obtained through Hall measurement, four-point probe analysis, etc., and compares the electrical properties of transparent conductive oxide films deposited at room temperature according to composition. No heat treatment was performed after deposition, and the film thickness was 50 nm.
[0058] [Table 8]
[0059] The requirements for a transparent electrode in a solar cell are: i) high light transmittance to increase the amount of sunlight incident on the light-absorbing layer; ii) low sheet resistance to reduce the loss of generated charge; and iii) a work function that matches well with the charge transport layer to form an ohmic contact. Assuming all three components are overdoped, since IGO, ITO, and IZO are all In₂O₃-based with small amounts of other substances, the differences in their work functions are not expected to be significant. Therefore, conditions i) and ii) are satisfied. Comparing the electrical properties of the three components, IGO has the lowest resistivity, and thus the lowest sheet resistance for films of the same thickness. Furthermore, compared to the other components, IGO has the lowest charge concentration and the highest charge mobility. Even with the same resistivity, only low charge concentration and high charge mobility can reduce light scattering caused by charge and increase light transmittance; therefore, IGO is the most suitable for a transparent electrode.
[0060] Figure 17 Table 9 below shows the results obtained through UV-Vis analysis, ellipsometric measurement, etc., and compares the optical properties of the transparent conductive oxide films deposited at room temperature according to composition. No heat treatment was performed after deposition, and the film thickness was 50 nm.
[0061] [Table 9]
[0062] Observing the light transmittance measured by UV-vis spectrophotometry according to wavelength, there were no significant differences in light transmittance among the three components of the film, but IGO exhibited a higher light transmittance on average by about 0.6%. In particular, if only the light transmittance at the 550nm wavelength, which accounts for the largest proportion in the solar spectrum, is compared, IGO is about 1% higher than the films of other components. This trend is consistent with the trend of the low charge concentration results of IGO mentioned above. At 550nm, the refractive index of IGO is 1.93, which is lower than that of ITO and closer to that of ordinary glass (1.5~1.9). Therefore, it can be determined that when used as a transparent electrode (a transparent electrode under perovskite) composed of IGO / glass, it is advantageous in terms of light reflectance.
[0063] Figure 18 The results of XRD analysis of the crystal structure and phases of a transparent conductive film deposited at room temperature are shown.
[0064] XRD patterns reveal that the three-component films deposited at low temperatures are all close to amorphous phases. Crystalline films typically exhibit a tendency for surface roughness to increase as facets are exposed. That is, generally, amorphous films have lower surface roughness than crystalline films, thus increasing the likelihood of reduced interface defect concentration when other layers are deposited on them. Furthermore, low-temperature deposited transparent electrodes are frequently used in flexible devices, where lower surface roughness is known to result in less stress concentration and better dispersion during bending, leading to less damage. Additionally, amorphous phases are known to withstand tensile stresses better than crystalline phases due to their superior atomic bonding properties.
[0065] Figure 19 and Figure 20 The results of surface morphology analysis of transparent conductive films deposited at room temperature are shown.
[0066] Both SEM and AFM results were obtained after post-annealing at 100℃. Even after heat treatment at 100℃, due to its amorphous phase, its shape was not expected to change even without post-annealing. Although no significant differences were observed in the SEM images, AFM analysis revealed that the surface roughness of IGO was significantly lower than that of ITO.
[0067] By using the transparent conductive oxide thin film according to the present invention as the transparent electrode or electron transport layer of a solar cell, the efficiency of the solar cell can be improved. In particular, using the IGO thin film deposited according to the present invention as the upper or lower electrode of the solar cell can increase the shunt resistance of the solar cell, thereby improving the energy conversion efficiency.
[0068] According to one embodiment, the solar cell can be any one of a perovskite solar cell, a silicon solar cell, a silicon / perovskite double-junction solar cell, and a perovskite / perovskite double-junction solar cell. The structures of perovskite solar cells, silicon solar cells, silicon / perovskite double-junction solar cells, and perovskite / perovskite double-junction solar cells are well known in the art to which this invention pertains, and therefore, descriptions of these structures will be omitted in this specification.
[0069] According to the present invention, as described above, a transparent conductive oxide thin film with excellent electro-optic properties that does not degrade even when deposited at low temperatures can be provided, thus making it suitable for perovskite solar cells that are at risk of degradation or decomposition at high temperatures above 200°C, and suitable for use as an upper electrode or intermediate layer.
Claims
1. A method for preparing an oxide sputtering target, comprising the following steps: To obtain a mixture including metal oxides; The mixture is introduced into a sintering furnace; and Sinter the mixture, wherein The step of sintering the mixture is carried out in the following manner: Oxygen is introduced into the sintering furnace at a first flow rate while the temperature is increased to heat the mixture once. Next, oxygen is introduced into the sintering furnace at a second flow rate while the temperature is further increased to reheat the mixture. Next, oxygen is introduced into the sintering furnace at a third flow rate while the temperature is further increased, thus heating the mixture three times. The metal oxide consists only of In₂O₃ and GeO₂. The heating process continues until the sintering atmosphere reaches any temperature within the range of 1050℃ to 1150℃. The secondary heating is performed until the sintering atmosphere reaches any temperature within the range of 1200℃ to 1300℃. The first flow rate and the third flow rate are greater than the second flow rate.
2. The method for preparing the oxide sputtering target as described in claim 1, wherein, The first heating is performed until the sintering atmosphere reaches any temperature within the range of 1050℃ to 1150℃.
3. The method for preparing the oxide sputtering target as described in claim 1, wherein, The first heating is performed until the sintering atmosphere reaches 1100°C.
4. The method for preparing the oxide sputtering target as described in claim 1, wherein, The secondary heating is performed until the sintering atmosphere reaches 1250°C.
5. The method for preparing the oxide sputtering target as described in claim 1, wherein, The three heating cycles are performed until the sintering atmosphere reaches any temperature within the range of 1450℃ to 1550℃.
6. The method for preparing the oxide sputtering target as described in claim 1, wherein, The three heating cycles are performed until the sintering atmosphere reaches 1500°C.
7. The method for preparing the oxide sputtering target as described in claim 1, wherein, The first flow rate and the third flow rate are flow rates of oxygen flowing into 101 L to 608 L per 1 m3of volume in the sintering furnace per minute. 3 of volume in the sintering furnace per minute.
8. The method for preparing the oxide sputtering target as described in claim 7, wherein, The first flow rate and the third flow rate are flow rates of oxygen flowing into 152 L to 557 L per 1 m 3 of volume in the sintering furnace per minute.
9. The method for preparing the oxide sputtering target as described in claim 8, wherein, The first flow rate and the third flow rate are flow rates of oxygen flowing into 213 L to 456 L per 1 m3of volume in the sintering furnace per minute. 3 of volume in the sintering furnace per minute.
10. The method for preparing the oxide sputtering target as described in claim 1, wherein, The second flow rate is a flow rate of oxygen of 0 L to 50 L per 1 m 3 of volume in the sintering furnace per minute.
11. The method for preparing the oxide sputtering target as described in claim 10, wherein, The second flow rate is a flow rate of oxygen flowing into 0 L per 1 m 3 of volume in the sintering furnace per minute.
12. The method for preparing the oxide sputtering target as described in claim 1, wherein, At least one of the first heating, the second heating, and the third heating is performed simultaneously by increasing the sintering atmosphere at a rate of 0.1℃ / min to 0.5℃ / min.
13. The method for preparing the oxide sputtering target as described in claim 12, wherein, At least one of the first heating, the second heating, and the third heating is performed simultaneously by increasing the temperature of the sintering atmosphere at a rate of 0.2℃ / min to 0.3℃ / min.
14. A method of forming a transparent conductive oxide film by sputtering an oxide sputter target, wherein, The oxide sputtering target is prepared by the method for preparing an oxide sputtering target according to any one of claims 1 to 13.