Normal-pressure atmosphere sintering method for large-size ITO rotating target material

Abstract

The invention relates to the technical field of rotating target materials, in particular to a normal-pressure atmosphere sintering method of a large-size ITO rotating target material, which comprises the following steps: placing a large-size ITO target material biscuit in a normal-pressure sintering furnace, sealing the furnace body, and then carrying out pre-exhaust treatment in the furnace; a sintering furnace temperature rising program is started, meanwhile, oxygen atmosphere is introduced into the furnace, the oxygen concentration and the gas flow are controlled to be kept stable, and the steps of pre-exhausting, multi-section temperature rising sintering, precise micropore exhausting and oxygen atmosphere cooling are conducted. Normal-pressure oxygen atmosphere sintering is adopted, compared with high-pressure oxygen atmosphere sintering, high-pressure equipment is not needed, the equipment cost and the production risk are reduced, and industrial large-scale production is easier; by controlling the oxygen concentration and flow, high-temperature decomposition of SnO2 is effectively inhibited, the low-resistivity performance of the target material is ensured, the density is larger than or equal to 98.5%, the resistivity is smaller than or equal to 0.12 m omega.cm, the cost is reduced, and industrialization is easy.

Description

Technical Field

[0001] This invention relates to the field of rotating target technology, and specifically to a method for sintering large-size ITO rotating targets under normal pressure atmosphere. Background Technology

[0002] ITO sputtering targets are the core material for preparing transparent conductive films, widely used in electronic information fields such as flat panel displays, solar cells, and touch screens. With the development of display technology towards larger sizes and higher resolutions, the demand for large-size ITO rotating sputtering targets is increasing. Compared to planar sputtering targets, rotating sputtering targets have advantages such as higher utilization and better coating uniformity. However, the preparation of large-size rotating sputtering targets (diameter over 300mm and length over 1000mm) is significantly more difficult, especially the sintering process, which directly determines the final performance of the target. Sintering is the core step that imparts key properties such as density, conductivity, and microstructure to the target. For large-size ITO rotating sputtering targets, due to their large size and uneven thickness, uneven heating is prone to occur during high-temperature sintering. Simultaneously, SnO2 in ITO easily decomposes at high temperatures, generating oxygen, leading to changes in oxygen partial pressure within the furnace. This further causes defects such as coarse main phase grains, uneven distribution of the second phase (such as In2O3-SnO2 solid solution), and insufficient density, ultimately affecting the conductivity and sputtering performance of the target and reducing the quality of the thin film product. In existing technologies, high-pressure oxygen atmosphere sintering or hot-pressing sintering are commonly used to solve the sintering problem of large-size ITO targets. While high-pressure oxygen atmosphere sintering can suppress SnO2 decomposition, it places extremely high demands on the pressure resistance of the sintering furnace, resulting in expensive equipment. Furthermore, the uniformity of the atmosphere within the furnace under high pressure is difficult to control, leading to localized performance differences. Hot-pressing sintering promotes densification by applying pressure, but the uniformity of pressure application for large-size targets is difficult to guarantee, easily generating internal stress and cracks. It also has low production efficiency and is not suitable for large-scale industrial production. Therefore, developing a low-cost, easily industrially implementable sintering method that effectively solves the problems of uneven heating and oxygen loss during the sintering of large-size ITO rotating targets is of great significance for improving the performance and yield of large-size ITO targets. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the purpose of this invention is to provide a method for sintering large-size ITO rotating targets under normal pressure atmosphere, so as to solve the problems mentioned in the background art.

[0004] The present invention solves the technical problem by adopting the following technical solution: This invention provides a method for sintering large-size ITO rotating targets under normal pressure atmosphere, comprising the following steps: Step 1: Place the large-size ITO target blank into an atmospheric pressure sintering furnace, seal the furnace body, and pre-ventilate the furnace. Step 2: Start the sintering furnace heating program and simultaneously introduce an oxygen atmosphere into the furnace, controlling the oxygen concentration and gas flow rate to remain stable. Step 3: Sintering is carried out using a multi-stage heating and holding mode, sequentially passing through a low-temperature preheating section, a medium-temperature densification section, a high-temperature holding section, and a cooling section. Step 4: During the sintering process, impurity gases are continuously discharged from the furnace through a precision microporous exhaust device to ensure uniform circulation of the atmosphere inside the furnace. Step 5: After sintering, the material is cooled to room temperature in the furnace under an oxygen atmosphere to obtain a large-size ITO rotating target. The oxygen flow rate during the cooling process is 0.3-1 L / min, and oxygen is stopped below 200°C.

[0005] Preferably, the pre-venting treatment in step one is as follows: first, a mechanical pump is used to evacuate the furnace to a pressure ≤50Pa, and after holding the temperature for 1-2 hours, an inert gas is introduced to replace it 2-3 times. After each replacement, the pressure is evacuated to ≤50Pa. The inert gas is nitrogen.

[0006] Preferably, the oxygen concentration in step two is 95%-99.99%, the gas flow rate is 0.5-2 L / min, and the heating rate of the heating program is 5-10 °C / min.

[0007] Preferably, the multi-stage heating and heat preservation mode in step three specifically refers to: (1) Low temperature preheating section: heat up to 800-1000℃ and keep warm for 3-5 hours; (2) Medium-temperature densification stage: Heat to 1400-1500℃ at a rate of 3-5℃ / min and hold for 8-12 hours; (3) High temperature insulation section: heat up to 1550-1570℃ at a rate of 2-3℃ / min and keep warm for 20-25h; (4) Cooling section: Cool down to 800℃ at a rate of 5-8℃ / min, and then cool down to room temperature at a rate of 10-15℃ / min.

[0008] Preferably, the micropore diameter of the precision micropore exhaust device in step four is 5-20 μm, the exhaust rate is matched with the oxygen introduction rate, and the pressure inside the furnace is maintained at atmospheric pressure ±50 Pa.

[0009] Preferably, the large-size ITO rotating target has a diameter of 300-600mm, a length of 1000-3000mm, and a green blank density of ≥55%.

[0010] Preferably, the oxygen flow rate is maintained at 0.3-1 L / min until the furnace temperature drops below 200°C, at which point the oxygen supply is stopped.

[0011] Preferably, the ITO rotating target material obtained after sintering has a density ≥98.5%, resistivity ≤0.12 mΩ·cm, and Sn 4+ The proportion is ≥88%, the main phase grain size is uniform, and the grain size deviation is ≤10%.

[0012] Compared with the prior art, the present invention has the following beneficial effects: This invention employs atmospheric oxygen atmosphere sintering, which, compared to high-pressure oxygen atmosphere sintering, eliminates the need for high-pressure equipment, reducing equipment costs and production risks, and facilitating large-scale industrial production. By controlling the oxygen concentration and flow rate, SnO2 is effectively suppressed. 2 The high-temperature decomposition ensures the low resistivity of the target material (≤0.12mΩ·cm). Employing a multi-stage heating and holding curve, through low-temperature preheating, medium-temperature densification, high-temperature long-term holding, and segmented cooling, not only is sufficient densification of the green blank achieved (density ≥98.5%), but abnormal grain growth caused by excessively high temperatures is also avoided, ensuring the uniformity of the main phase grain size with a grain size deviation ≤10%. Combined with a precision microporous exhaust device, uniform flow and stable pressure within the furnace atmosphere are achieved, avoiding problems of excessively low or high local oxygen partial pressure. This ensures the consistency of the sintering environment across all parts of the large-size target material, solving the defects of uneven heating and uneven second-phase distribution in large-size targets, and improving the overall uniformity of the target material's performance. The method of this invention is simple and convenient to operate, producing large-size ITO rotating targets with excellent performance and a high yield, meeting the application requirements of large-size flat panel displays, solar cells, and other fields. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] This embodiment of a method for sintering a large-size ITO rotating target material under normal pressure includes the following steps: Step 1: Place the large-size ITO target blank into an atmospheric pressure sintering furnace, seal the furnace body, and pre-ventilate the furnace. Step 2: Start the sintering furnace heating program and simultaneously introduce an oxygen atmosphere into the furnace, controlling the oxygen concentration and gas flow rate to remain stable. Step 3: Sintering is carried out using a multi-stage heating and holding mode, sequentially passing through a low-temperature preheating section, a medium-temperature densification section, a high-temperature holding section, and a cooling section. Step 4: During the sintering process, impurity gases are continuously discharged from the furnace through a precision microporous exhaust device to ensure uniform circulation of the atmosphere inside the furnace. Step 5: After sintering, the material is cooled to room temperature in an oxygen atmosphere to obtain a large-size ITO rotating target.

[0015] The pre-venting process described in step one of this embodiment is as follows: First, a mechanical pump is used to evacuate the furnace to a pressure ≤50Pa. After holding the furnace at this temperature for 1-2 hours, inert gas is introduced to replace the pressure 2-3 times. After each replacement, the pressure is evacuated to ≤50Pa.

[0016] In step two of this embodiment, the oxygen concentration is 95%-99.99%, the gas flow rate is 0.5-2L / min, and the heating rate of the heating program is 5-10℃ / min.

[0017] The multi-stage heating and heat preservation mode described in step three of this embodiment is as follows: (1) Low temperature preheating section: heat up to 800-1000℃ and keep warm for 3-5 hours; (2) Medium-temperature densification stage: Heat to 1400-1500℃ at a rate of 3-5℃ / min and hold for 8-12 hours; (3) High temperature insulation section: heat up to 1550-1570℃ at a rate of 2-3℃ / min and keep warm for 20-25h; (4) Cooling section: Cool down to 800℃ at a rate of 5-8℃ / min, and then cool down to room temperature at a rate of 10-15℃ / min.

[0018] In step four of this embodiment, the micropore diameter of the precision micropore exhaust device is 5-20 μm, the exhaust rate is matched with the oxygen introduction rate, and the pressure inside the furnace is maintained at atmospheric pressure ±50 Pa.

[0019] The large-size ITO rotating target in this embodiment has a diameter of 300-600mm, a length of 1000-3000mm, and a green blank density of ≥55%.

[0020] In this embodiment, the oxygen flow rate is maintained at 0.3-1 L / min until the furnace temperature drops below 200°C, at which point the oxygen supply is stopped.

[0021] The ITO rotating target material obtained after sintering in this embodiment has a density ≥98.5%, resistivity ≤0.12 mΩ·cm, and Sn 4+ The proportion is ≥88%, the main phase grain size is uniform, and the grain size deviation is ≤10%.

[0022] Example 1. This embodiment of a method for sintering a large-size ITO rotating target material under normal pressure includes the following steps: Step 1: Place the large-size ITO target blank into an atmospheric pressure sintering furnace, seal the furnace body, and pre-ventilate the furnace. Step 2: Start the sintering furnace heating program and simultaneously introduce an oxygen atmosphere into the furnace, controlling the oxygen concentration and gas flow rate to remain stable. Step 3: Sintering is carried out using a multi-stage heating and holding mode, sequentially passing through a low-temperature preheating section, a medium-temperature densification section, a high-temperature holding section, and a cooling section. Step 4: During the sintering process, impurity gases are continuously discharged from the furnace through a precision microporous exhaust device to ensure uniform circulation of the atmosphere inside the furnace. Step 5: After sintering, the material is cooled to room temperature in an oxygen atmosphere to obtain a large-size ITO rotating target.

[0023] The pre-venting process described in step one of this embodiment is as follows: First, a mechanical pump is used to evacuate the furnace to a pressure ≤50Pa. After holding the furnace at this temperature for 1 hour, inert gas is introduced to replace the pressure twice. After each replacement, the pressure is evacuated to ≤50Pa.

[0024] In step two of this embodiment, the oxygen concentration is 95% and the gas flow rate is 0.5 L / min; the heating rate of the heating program is 5 °C / min.

[0025] The multi-stage heating and heat preservation mode described in step three of this embodiment is as follows: (1) Low temperature preheating section: heat up to 800℃ and keep warm for 3 hours; (2) Medium-temperature densification section: The temperature is increased to 1400℃ at a rate of 3℃ / min and held for 8 hours; (3) High temperature insulation section: The temperature is increased to 1550℃ at a rate of 2℃ / min and kept for 20h; (4) Cooling section: Cool down to 800℃ at a rate of 5℃ / min, and then cool down to room temperature at a rate of 10℃ / min.

[0026] In step four of this embodiment, the micropore diameter of the precision micropore exhaust device is 5μm, the exhaust rate is matched with the oxygen introduction rate, and the pressure inside the furnace is maintained at atmospheric pressure ±50Pa.

[0027] The large-size ITO rotating target in this embodiment has a diameter of 300mm, a length of 1000mm, and a green blank density of ≥55%.

[0028] In this embodiment, the oxygen flow rate is maintained at 0.3 L / min until the furnace temperature drops below 200°C, at which point the oxygen supply is stopped.

[0029] The ITO rotating target material obtained after sintering in this embodiment has a density ≥98.5%, resistivity ≤0.12 mΩ·cm, and Sn 4+ The proportion is ≥88%, the main phase grain size is uniform, and the grain size deviation is ≤10%.

[0030] Example 2. This embodiment of a method for sintering a large-size ITO rotating target material under normal pressure includes the following steps: Step 1: Place the large-size ITO target blank into an atmospheric pressure sintering furnace, seal the furnace body, and pre-ventilate the furnace. Step 2: Start the sintering furnace heating program and simultaneously introduce an oxygen atmosphere into the furnace, controlling the oxygen concentration and gas flow rate to remain stable. Step 3: Sintering is carried out using a multi-stage heating and holding mode, sequentially passing through a low-temperature preheating section, a medium-temperature densification section, a high-temperature holding section, and a cooling section. Step 4: During the sintering process, impurity gases are continuously discharged from the furnace through a precision microporous exhaust device to ensure uniform circulation of the atmosphere inside the furnace. Step 5: After sintering, the material is cooled to room temperature in an oxygen atmosphere to obtain a large-size ITO rotating target.

[0031] The pre-venting process described in step one of this embodiment is as follows: First, a mechanical pump is used to evacuate the furnace to a pressure ≤50Pa. After holding the furnace at this temperature for 2 hours, inert gas is introduced to replace the pressure 3 times. After each replacement, the pressure is evacuated to ≤50Pa.

[0032] In step two of this embodiment, the oxygen concentration is 99.99% and the gas flow rate is 2L / min; the heating rate of the heating program is 10℃ / min.

[0033] The multi-stage heating and heat preservation mode described in step three of this embodiment is as follows: (1) Low temperature preheating section: heat up to 1000℃ and keep warm for 5 hours; (2) Medium-temperature densification section: The temperature is increased to 1500℃ at a rate of 5℃ / min and held for 12h; (3) High temperature insulation section: The temperature is increased to 1570℃ at a rate of 3℃ / min and kept for 25h; (4) Cooling section: Cool down to 800℃ at a rate of 8℃ / min, and then cool down to room temperature at a rate of 15℃ / min.

[0034] In step four of this embodiment, the micropore diameter of the precision micropore exhaust device is 20 μm, the exhaust rate is matched with the oxygen introduction rate, and the pressure inside the furnace is maintained at atmospheric pressure ±50 Pa.

[0035] The large-size ITO rotating target in this embodiment has a diameter of 600mm, a length of 3000mm, and a green blank density of ≥55%.

[0036] In this embodiment, the oxygen flow rate is maintained at 1L / min until the furnace temperature drops below 200°C, at which point the oxygen supply is stopped.

[0037] The ITO rotating target material obtained after sintering in this embodiment has a density ≥98.5%, resistivity ≤0.12 mΩ·cm, and Sn 4+ The proportion is ≥88%, the main phase grain size is uniform, and the grain size deviation is ≤10%.

[0038] Example 3. This embodiment of a method for sintering a large-size ITO rotating target material under normal pressure includes the following steps: Step 1: Place the large-size ITO target blank into an atmospheric pressure sintering furnace, seal the furnace body, and pre-ventilate the furnace. Step 2: Start the sintering furnace heating program and simultaneously introduce an oxygen atmosphere into the furnace, controlling the oxygen concentration and gas flow rate to remain stable. Step 3: Sintering is carried out using a multi-stage heating and holding mode, sequentially passing through a low-temperature preheating section, a medium-temperature densification section, a high-temperature holding section, and a cooling section. Step 4: During the sintering process, impurity gases are continuously discharged from the furnace through a precision microporous exhaust device to ensure uniform circulation of the atmosphere inside the furnace. Step 5: After sintering, the material is cooled to room temperature in an oxygen atmosphere to obtain a large-size ITO rotating target.

[0039] The pre-venting process described in step one of this embodiment is as follows: First, a mechanical pump is used to evacuate the furnace to a pressure ≤50Pa. After holding the furnace at this temperature for 1.5 hours, inert gas is introduced to replace the pressure twice. After each replacement, the pressure is evacuated to ≤50Pa.

[0040] In step two of this embodiment, the oxygen concentration is 98% and the gas flow rate is 1L / min; the heating rate of the heating program is 7.5℃ / min.

[0041] The multi-stage heating and heat preservation mode described in step three of this embodiment is as follows: (1) Low temperature preheating section: heat up to 900℃ and keep warm for 4 hours; (2) Medium-temperature densification section: The temperature is increased to 1450℃ at a rate of 4℃ / min and held for 10h; (3) High temperature insulation section: The temperature is increased to 1560℃ at a rate of 2.5℃ / min and kept for 22h; (4) Cooling section: Cool down to 800℃ at a rate of 6.5℃ / min, and then cool down to room temperature at a rate of 12.5℃ / min.

[0042] In step four of this embodiment, the micropore diameter of the precision micropore exhaust device is 10 μm, the exhaust rate is matched with the oxygen introduction rate, and the pressure inside the furnace is maintained at atmospheric pressure ±50 Pa.

[0043] The large-size ITO rotating target in this embodiment has a diameter of 450mm, a length of 2000mm, and a preform density of ≥55%.

[0044] In this embodiment, the oxygen flow rate is maintained at 0.6 L / min until the furnace temperature drops below 200°C, at which point the oxygen supply is stopped.

[0045] The ITO rotating target material obtained after sintering in this embodiment has a density ≥98.5%, resistivity ≤0.12 mΩ·cm, and Sn 4+ The proportion is ≥88%, the main phase grain size is uniform, and the grain size deviation is ≤10%.

[0046] Comparative Example 1. Unlike Example 3, the multi-stage heating and heat preservation mode does not use a low-temperature preheating stage.

[0047] Comparative Example 2. Unlike Example 3, the multi-stage heating and heat preservation mode does not use a medium-temperature densification stage.

[0048] Comparative Example 3. Unlike Example 3, the multi-stage heating and heat preservation mode does not use a high-temperature heat preservation stage.

[0049] Comparative Example 4. Unlike Example 3, in the multi-stage heating and heat preservation mode, the cooling stage is directly replaced by air cooling to room temperature.

[0050] Performance tests were conducted on the products of Examples 1-3 and Comparative Examples 1-4, and the test results are as follows:

[0051] The test results from Examples 1-3 show that the atmospheric pressure sintering method of the present invention can prepare high-performance large-size ITO rotating targets with a density ≥98.5%, resistivity ≤0.12mΩ·cm, and grain size deviation ≤10%, without defects such as cracks or deformation. The performance indicators meet or even exceed those of existing high-pressure oxygen sintering methods. The results of Comparative Examples 1-4 verify the necessity of the multi-stage process and oxygen-protected cooling of the present invention: Lack of a low-temperature preheating stage: Impurities in the green blank are not fully removed, resulting in decreased density, increased resistivity, and surface cracks caused by thermal stress; Lack of a medium-temperature densification stage: Insufficient particle rearrangement, inadequate densification, and increased porosity; Lack of a high-temperature holding stage: Complete densification cannot be achieved, leading to significantly worse density and conductivity; Direct air cooling and cessation of oxygen supply: Thermal stress causes deformation, secondary grain growth, and increased size deviation.

[0052] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0053] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for sintering large-size ITO rotating targets under normal pressure atmosphere, characterized in that, Includes the following steps: Step 1: Place the large-size ITO target blank into an atmospheric pressure sintering furnace, seal the furnace body, and pre-ventilate the furnace. Step 2: Start the sintering furnace heating program and simultaneously introduce an oxygen atmosphere into the furnace, controlling the oxygen concentration and gas flow rate to remain stable. Step 3: Sintering is carried out using a multi-stage heating and holding mode, sequentially passing through a low-temperature preheating section, a medium-temperature densification section, a high-temperature holding section, and a cooling section. Step 4: During the sintering process, impurity gases are continuously discharged from the furnace through a precision microporous exhaust device to ensure uniform circulation of the atmosphere inside the furnace. Step 5: After sintering, the material is cooled to room temperature in an oxygen atmosphere to obtain a large-size ITO rotating target.

2. The method according to claim 1, characterized in that, The pre-venting process described in step one is as follows: First, use a mechanical pump to evacuate the furnace to a pressure ≤50Pa, keep it at that temperature for 1-2 hours, and then introduce inert gas to replace it 2-3 times. After each replacement, evacuate the furnace to a pressure ≤50Pa. The inert gas is nitrogen.

3. The method according to claim 1, characterized in that, In step two, the oxygen concentration is 95%-99.99% and the gas flow rate is 0.5-2 L / min; the heating rate of the heating program is 5-10 °C / min.

4. The method according to claim 1, characterized in that, The multi-stage heating and heat preservation mode mentioned in step three is specifically as follows: (1) Low temperature preheating section: heat up to 800-1000℃ and keep warm for 3-5 hours; (2) Medium-temperature densification stage: Heat to 1400-1500℃ at a rate of 3-5℃ / min and hold for 8-12 hours; (3) High temperature insulation section: heat up to 1550-1570℃ at a rate of 2-3℃ / min and keep warm for 20-25h; (4) Cooling section: Cool down to 800℃ at a rate of 5-8℃ / min, and then cool down to room temperature at a rate of 10-15℃ / min.

5. The method according to claim 1, characterized in that, The micropore diameter of the precision micropore exhaust device described in step four is 5-20 μm, the exhaust rate is matched with the oxygen introduction rate, and the pressure inside the furnace is maintained at atmospheric pressure ±50 Pa.

6. The method according to claim 1, characterized in that, The large-size ITO rotating target has a diameter of 300-600mm, a length of 1000-3000mm, and a green blank density of ≥55%.

7. The method according to claim 1, characterized in that, In step five, during the process of cooling the furnace to room temperature under the protection of an oxygen atmosphere, the oxygen flow rate is maintained at 0.3-1 L / min until the furnace temperature drops below 200°C and then the oxygen supply is stopped.

8. The method according to any one of claims 1-7, characterized in that, The ITO rotating target material obtained after sintering has a density ≥98.5%, resistivity ≤0.12 mΩ·cm, and Sn 4+ The proportion is ≥88%, the main phase grain size is uniform, and the grain size deviation is ≤10%.

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