A method for manufacturing an ingot for a yttrium metal rotating target

Abstract

The application discloses a preparation method of a cast ingot for a yttrium metal rotary target material and relates to the technical field of metal target material preparation. The method sequentially comprises vacuum melting and electromagnetic stirring, centrifugal casting and ultrafast cooling, and a hot isostatic pressing treatment process. When casting, the yttrium metal melt is brought into contact with the inner wall of a mold and instantaneously starts cooling water, so as to be directionally and ultrafastly cooled along the outer wall of the mold to the center of the circle at a cooling speed of not less than 100 K / s. The application constructs a short-process preparation scheme of casting instead of forging, saves traditional forging and rolling processes, and can prepare a yttrium metal cast ingot with oxygen content of not more than 200 ppm, nitrogen content of not more than 50 ppm and density of not less than 98%. The target material sputtering and plating film is not cracked, the production efficiency is effectively improved, the manufacturing cost is reduced, and the application requirement of high-end sputtering and plating is met.

Description

Technical Field

[0001] This application relates to the field of metal target preparation, and more particularly to a method for preparing a casting ingot for a yttrium metal rotating target. Background Technology

[0002] Yttrium metal sputtering targets are core functional materials in high-end sputtering coating fields, widely used in semiconductor devices, flat panel displays, optical coatings, and the preparation of special functional thin films. As the coating industry continues to demand higher material utilization, film uniformity, and production efficiency, rotating targets, with their significant advantage of material utilization exceeding 50%, are gradually replacing traditional planar targets with only 20%–30% material utilization, becoming the mainstream direction for industry development.

[0003] Currently, the mainstream manufacturing process for metal sputtering targets is a long process involving smelting, forging, rolling, heat treatment, and machining. This process requires multiple hot working and heat treatment steps, resulting in a long overall production cycle and low production efficiency. Furthermore, repeated high-temperature hot working significantly increases energy consumption, equipment depreciation, and labor costs. More importantly, yttrium metal is chemically extremely reactive, and during the lengthy, multi-step production process, it easily introduces impurities such as oxygen and nitrogen, damaging the purity and performance of the final sputtering target. Due to the extremely high reactivity of yttrium powder, it is easily oxidized and can even spontaneously combust, leading to low density and numerous pores in sputtering targets prepared using traditional powder metallurgy.

[0004] Moreover, large-size rotating targets are difficult to prepare. When producing large-size rotating targets using traditional casting methods, defects such as component segregation, uneven structure, shrinkage cavities, and porosity are prone to occur. In addition, yttrium metal is brittle and difficult to process in subsequent steps. Summary of the Invention

[0005] To address the aforementioned deficiencies, this application provides a method for preparing yttrium metal rotating target ingots, which can efficiently and cost-effectively prepare high-purity, high-density yttrium metal rotating target ingots.

[0006] In a first aspect, a method for preparing a yttrium metal rotating target ingot is provided, the method comprising:

[0007] Vacuum melting and electromagnetic stirring: Yttrium ingots are vacuum melted, and electromagnetic stirring is used during the vacuum melting process to obtain yttrium metal melt;

[0008] Centrifugal casting and rapid cooling: Yttrium metal melt is fed into a sealed centrifugal casting system to complete centrifugal casting and directional rapid cooling to prepare the billet. During casting, cooling water is activated the instant the yttrium metal melt comes into contact with the inner wall of the mold, and directional rapid cooling is carried out along the outer wall of the mold towards the center at a cooling rate of not less than 100K / s.

[0009] The billet is subjected to hot isostatic pressing under an inert gas atmosphere to obtain a dense ingot.

[0010] In the embodiments of this application, an innovative short process integrating vacuum melting and electromagnetic stirring, centrifugal casting and rapid cooling, and hot isostatic pressing is constructed, with each process working synergistically to prepare high-purity, high-density yttrium rotating target ingots. The yttrium metal rotating target ingots prepared by this method have an oxygen content of no more than 200 ppm, a nitrogen content of no more than 50 ppm, and a density of no less than 98%.

[0011] Centrifugal casting employs an extremely rapid cooling rate of no less than 100 K / s, resulting in the formation of a fine-grained structure in the as-cast stage. This eliminates the need for forging and rolling, reducing costs and improving efficiency. The fine grains enhance the densification efficiency of hot isostatic pressing, disperse stress, and reduce the likelihood of cracking during sputtering. The hot isostatic pressing process can retain fine grains while closing shrinkage cavities and microcracks. This process, combined with the centrifugal force feeding effect of centrifugal casting, synergistically reduces the problems of shrinkage cavities and porosity in the billet, effectively improving the density of the billet.

[0012] As an embodiment of this application, in the vacuum melting and electromagnetic stirring steps, yttrium blocks are placed in a water-cooled copper crucible and then placed in a sealed furnace. The yttrium blocks are heated under vacuum conditions to melt them, and the melt is kept at a constant temperature.

[0013] Electromagnetic stirring was then performed, and the mixture was allowed to stand and be kept at a constant temperature to obtain yttrium metal melt.

[0014] In this embodiment, a water-cooled copper crucible is used in conjunction with electromagnetic stirring to strictly control the impurity baseline of the melt, effectively alleviate the problem of component segregation in the cast billet, and improve the axial performance consistency of large-size target billets.

[0015] As one embodiment of this application, the vacuum melting and electromagnetic stirring steps further include degassing the sealed furnace before heating the molten yttrium ingot: first, the sealed furnace is evacuated to a vacuum level not exceeding 5.0 × 10⁻⁶. -3 Pa, then heat the furnace to 800~1000℃ and hold for 5~10 minutes.

[0016] In this embodiment, a high-vacuum pre-heating and degassing technology is used before melting to effectively reduce the initial oxygen and nitrogen content of the melt, and to prevent a large amount of impurities from dissolving into the yttrium metal melt during the melting process, thereby controlling the impurity level from the early stage of smelting.

[0017] As an embodiment of this application, in the vacuum melting and electromagnetic stirring steps, the purity of the yttrium block is not less than 99.95%; the melting temperature of the yttrium block is 1550~1650℃, and the melt holding time is 10~20min.

[0018] In this embodiment, high-purity yttrium raw material feeding control technology is used to ensure the basic purity of the finished ingot. Simultaneously, high-temperature melting and holding technology combined with sufficient holding time further improves the purity of the melt, reduces porosity and air gap defects in the cast product, and lowers the gaseous impurity content of the finished product.

[0019] As an embodiment of this application, in the vacuum melting and electromagnetic stirring steps, the electromagnetic stirring frequency is 5-10Hz, the stirring time is 15-30min, and the standing and holding time is 3-5min.

[0020] In this embodiment of the application, the process can effectively alleviate the component segregation in the subsequent casting process, improve the axial composition and microstructure consistency of the tubular target billet, and ensure the overall performance of the product is uniform and stable.

[0021] As an embodiment of this application, in the centrifugal casting and rapid cooling steps, the mold needs to be preheated to 150~300°C, and the yttrium metal melt is poured into the mold smoothly and evenly. The temperature of the yttrium metal melt during casting is 1500~1600°C, and the rotation speed of the mold is 200~800 rpm. Rapid cooling is stopped when the casting temperature drops to 150~200°C to obtain the casting billet.

[0022] In this embodiment, mold preheating avoids molten splashing and cold shut defects caused by rapid cooling. Furthermore, matching the casting temperature control ensures complete filling and good surface quality of the cast billet, while providing a stable foundation for subsequent directional rapid cooling and the acquisition of a fine-grained structure.

[0023] Furthermore, by matching the centrifugal speed of the mold with an extremely rapid cooling rate, the timing of melt solidification is precisely controlled, allowing for the direct acquisition of a fine-grained microstructure in the as-cast state. Combined with electromagnetic stirring, this effectively addresses the industry pain points of high difficulty in preparing large-size rotating targets, and the tendency for compositional segregation and uneven microstructure.

[0024] As an embodiment of this application, the centrifugal casting and rapid cooling steps include a gas washing operation of the sealed chamber of the sealed furnace before casting: the sealed chamber is evacuated to no more than 1 Pa, and then filled with high-purity argon gas to 100~110 kPa, and this gas washing process is repeated 1~2 times.

[0025] In this embodiment, a circulating gas replacement technology is used to isolate the high-temperature yttrium melt from air, avoid oxidation and nitriding reactions during casting, effectively control the increase in oxygen and nitrogen in the billet, and ensure the purity of the final ingot.

[0026] As an embodiment of this application, in the centrifugal casting and rapid cooling steps, the mold is tubular in shape and made of copper.

[0027] Rapid cooling is achieved through water cooling: the cooling water pressure is 0.6~0.8MPa, and the cooling water temperature is 18~25℃, forming a cooling direction that proceeds from the outer wall towards the center.

[0028] In this embodiment, a copper tubular mold is used because copper has high thermal conductivity, which provides a hardware basis for rapid cooling.

[0029] Meanwhile, the use of high-pressure water-cooled directional solidification technology can ensure that the cooling rate is stable at no less than 100K / s, which can significantly improve the solidification nucleation rate and refine the grains; at the same time, it can reduce the microstructure inhomogeneity and internal porosity defects in the wall thickness direction.

[0030] As an embodiment of this application, in the hot isostatic pressing process, heat preservation and pressure holding treatment is carried out at a temperature of 900~1000℃ and a pressure of 100~150MPa.

[0031] In this embodiment of the application, during the hot isostatic pressing process, the temperature and pressure process parameters within a narrow range are controlled, which can not only fully close casting defects such as shrinkage cavities, porosity and microcracks inside the billet, but also avoid destroying the fine-grained structure formed by rapid cooling, thus achieving the dual effect of billet densification and grain refinement.

[0032] As an embodiment of this application, in the hot isostatic pressing process, the hot isostatic pressing furnace is first evacuated to a vacuum of no more than 1.0 Pa, then filled with high-purity argon gas to 1~2 MPa and then heated. The heating rate is 5~10℃ / min, and the holding time is 2~4h.

[0033] After the heat preservation and pressure holding are completed, depressurization and cooling are carried out. The depressurization rate is 1~2MPa / min, and the gas pressure drops to 10~20MPa after depressurization. The cooling rate is 5~10℃ / min, and an argon atmosphere is maintained during the cooling process.

[0034] In this embodiment, the pre-process of hot isostatic pressing prevents oxidation and oxygenation of the yttrium billet during hot isostatic pressing, allowing the internal pores of the target billet to fully collapse and diffuse for healing, thus significantly improving the density of the ingot.

[0035] At the same time, slow depressurization and slow cooling can smoothly release internal stress, ensure the structural integrity of the workpiece after densification treatment, maintain the surface purity of the product, and avoid secondary oxidation and contamination. Attached Figure Description

[0036] Figure 1 The diagram shows the process steps of the preparation method of yttrium metal rotating target ingot in the embodiments of this application. Detailed Implementation

[0037] To enhance understanding of this application, the following detailed description will be provided in conjunction with embodiments. These embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of this application.

[0038] To facilitate understanding of the technical solution of this application, the technical problem to be solved by the technical solution of this application will be explained first.

[0039] In some embodiments, a method for preparing high-purity metal rotating targets is disclosed. The method first involves vacuum melting of metal ingots such as aluminum and copper to obtain molten metal liquid, then centrifugation casting to obtain hollow billets, followed by multiple plastic deformation processes of hot spinning thinning and cold spinning forming to prepare hollow target billets, and finally cutting and back tube binding to obtain finished rotating targets. This method can improve the dimensional accuracy and yield of aluminum and copper rotating targets to a certain extent. However, this solution is only designed for low-activity metals such as aluminum and copper. The smelting process does not avoid contamination from the crucible material. Centrifugal casting uses sand molds. If applied directly to chemically highly reactive yttrium, the high-temperature melt will directly contact the crucible and mold, introducing a large amount of impurities such as oxygen, carbon, and iron, which cannot meet the purity requirements of high-purity yttrium targets. At the same time, this solution relies on multi-pass spinning plastic deformation to refine grains and increase density. However, yttrium is inherently brittle and is prone to cracking during spinning deformation. Furthermore, the lengthy multi-process production process will continuously increase the risk of oxidation and nitridation of yttrium, making it difficult to stably produce high-purity, high-density yttrium metal ingots for spinning targets.

[0040] To address the aforementioned technical problems, this embodiment provides a method for preparing yttrium metal rotating target ingots. This method optimizes the preparation steps and process parameters. The preparation steps are carried out sequentially in the order of vacuum melting and electromagnetic stirring, centrifugal casting and rapid cooling, and hot isostatic pressing. By controlling the cooling rate and the narrow temperature and pressure range of hot isostatic pressing, the formation of fine grains is precisely controlled, resulting in yttrium metal rotating target ingots with high purity and high density.

[0041] The preparation method of yttrium metal rotating target ingot according to the present application will be described in detail below with reference to specific embodiments.

[0042] In some embodiments, this application discloses a method for preparing a yttrium metal rotating target ingot, such as... Figure 1 As shown, this step includes S1-S5, specifically:

[0043] S1, Vacuum melting and electromagnetic stirring.

[0044] After the yttrium raw material block is placed into the crucible, the whole thing is placed into a sealed melting furnace. After the sealed furnace body is evacuated to a vacuum state, the heating program is started to gradually heat the yttrium block to complete melting. The temperature is maintained for melting and heat preservation, which promotes the escape and removal of dissolved gaseous impurities in the melt. After the heat preservation is completed, electromagnetic stirring is started to homogenize the melt and make the composition and temperature field of the melt uniformly distributed. After stirring is stopped, the melt is kept still for heat preservation until a uniform yttrium metal melt is obtained.

[0045] S2, centrifugal casting and rapid cooling.

[0046] The yttrium molten metal is smoothly transported to a high-speed rotating mold through a sealed centrifugal casting system. The rotation speed of the mold is controlled, and the centrifugal force is used to make the yttrium molten metal evenly adhere to the inner wall of the mold. At the instant the yttrium molten metal contacts the inner wall of the mold, the cooling water system is started simultaneously, and the yttrium molten metal is cooled rapidly along the outer wall of the mold towards the center at a cooling rate of not less than 100 K / s. When the overall temperature of the casting drops to the preset temperature, the mold rotation is stopped, the formed workpiece is removed, and the casting billet is obtained.

[0047] This invention employs an ultra-rapid cooling process of no less than 100 K / s, which can directly obtain a uniform, fine-grained microstructure in the as-cast state. The mechanism is as follows: according to the basic theory of metal solidification, during metal solidification, the cooling rate is positively correlated with the melt undercooling and nucleation rate; the higher the cooling rate, the greater the undercooling during melt solidification, the more the number of nucleation sites increases exponentially, the number of grains increases significantly, and the final product grain size is greatly reduced, forming a uniform and fine as-cast microstructure. This process can achieve grain refinement without relying on traditional forging, rolling, and other plastic deformation processes, which is the core foundation for this invention to achieve a short-process preparation using casting instead of forging.

[0048] S3. Hot isostatic pressing (HIP) treatment.

[0049] The billet is placed stably in the homogenization zone of the hot isostatic pressing furnace, the vacuum system is activated to evacuate the furnace, and then inert gas is introduced into the furnace cavity. The temperature and pressure are gradually increased according to the process procedure, and heat and pressure are maintained under these conditions. Through the synergistic effect of high temperature and high pressure, the shrinkage porosity and micropores inside the billet are fully collapsed and welded, achieving densification of the structure. After the treatment is completed, the pressure is gradually released and the temperature is lowered at the set rate. The workpiece is then removed to obtain a dense ingot.

[0050] The yttrium metal rotating target ingots prepared by the above method have an oxygen content of no more than 200 ppm, a nitrogen content of no more than 50 ppm, and a density of no less than 98%.

[0051] In the embodiments of this application, an innovative short process integrating vacuum melting and electromagnetic stirring, centrifugal casting and rapid cooling, and hot isostatic pressing is constructed. This process constructs a preparation scheme that replaces forging with casting, which significantly shortens the production cycle and reduces production costs. At the same time, it can stably prepare yttrium metal tubular ingots with low impurities and high density, solving the industry pain points of long preparation process, easy introduction of impurities, many casting defects, and coarse structure of traditional yttrium target materials.

[0052] In the embodiments of this application, the technical means of vacuum melting combined with electromagnetic stirring is used to control the introduction of impurities and achieve melt homogenization from the melting stage, so as to provide qualified raw materials for subsequent casting. The directional rapid cooling technology of instantaneous activation of cooling water when the melt contacts the mold is used to directly refine the as-cast grains through high cooling rate, eliminating the need for traditional plastic deformation processes such as forging and rolling. The hot isostatic pressing process can retain fine grains while closing shrinkage cavities and microcracks. This process, together with the centrifugal force feeding effect of centrifugal casting, forms a synergy to reduce the shrinkage and porosity of the target billet, effectively improving the density of the target billet.

[0053] Furthermore, the resulting dense ingots can undergo the following processing to meet the requirements for industrial use.

[0054] S4. Turning process.

[0055] The densified ingot is placed in an inert gas-protected machining environment, and the workpiece is machined to the target dimensions. After machining, the workpiece is immediately sealed in a vacuum bag under an argon atmosphere to isolate it from the outside air. The purpose of using inert atmosphere-protected turning technology is to isolate the workpiece from air at the high temperature of cutting, thus preventing surface oxidation.

[0056] S5. Finished product packaging.

[0057] Solvents are used to clean the surface of the yttrium metal rotating target ingot after turning to remove trace amounts of fingerprints, dust and other contaminants remaining on the workpiece surface; after the workpiece surface is completely dry, it is packaged: finally, the packaged ingot is placed in a high-strength corrugated cardboard box or wooden box for storage and transportation.

[0058] In some embodiments, the solvent in the finished product packaging step includes anhydrous ethanol;

[0059] The packaging uses a double-layer seal; the inner layer is sealed with an aluminum-plastic composite film, evacuated to a vacuum state and containing a desiccant; the outer cavity is filled with high-purity argon gas and then sealed.

[0060] In some embodiments, in the vacuum melting and electromagnetic stirring steps, the crucible is a water-cooled copper crucible; the electromagnetic stirring is intermittent electromagnetic stirring.

[0061] In this embodiment, a water-cooled copper crucible is used for vacuum melting, replacing the ceramic or graphite crucibles used in traditional processes. This avoids direct contact between the crucible material and the high-temperature yttrium melt, preventing the infiltration of impurities such as Fe, O, and C during the melting process and strictly controlling the impurity baseline of the melt. Simultaneously, intermittent electromagnetic stirring technology is used to homogenize the temperature and composition fields of the melt without mechanical contact or the introduction of additional contamination. This provides homogeneous raw materials for subsequent casting processes, effectively alleviating the problem of component segregation in the cast billet and improving the axial performance consistency of large-size target billets.

[0062] In some embodiments, the vacuum melting and electromagnetic stirring steps further include degassing the sealed furnace before heating the molten yttrium ingot: first, the sealed furnace is evacuated to a vacuum level not exceeding 5.0 × 10⁻⁶. -3 Pa, then heat the furnace to 800~1000℃ and hold for 5~10 minutes.

[0063] In this embodiment, a high-vacuum pre-heating and degassing technology is employed before melting. This technology removes water vapor and gas adsorbed on the surface of the yttrium ingot through high vacuum combined with medium-temperature heat preservation before the raw material melts, while simultaneously expelling residual air from inside the furnace cavity. This effectively reduces the initial oxygen and nitrogen content of the melt, preventing a large amount of impurities from dissolving into the yttrium metal melt during the melting process, thus controlling impurity levels from the early stages of smelting.

[0064] In some embodiments, during the vacuum melting and electromagnetic stirring steps, the purity of the yttrium block is not less than 99.95%; the melting temperature of the yttrium block is 1550~1650℃, and the melt holding time is 10~20min.

[0065] In this embodiment, the high-purity yttrium feedstock control technology can control the impurity baseline from the source, reducing the purification pressure in subsequent processes. This ensures the basic purity of the finished ingot, reduces the initial introduction of metallic and gaseous impurities, and provides the prerequisite for obtaining a high-purity product with low oxygen and low nitrogen.

[0066] Simultaneously, high-temperature melting and holding technology is employed to ensure the complete melting of the yttrium raw material. Sufficient holding time allows dissolved gaseous impurities such as oxygen and nitrogen to escape fully from the melt and be continuously extracted by the vacuum system. This further improves melt purity, reduces porosity and air gap defects in the cast product, and lowers the gaseous impurity content of the finished product.

[0067] In some embodiments, during the vacuum melting and electromagnetic stirring steps, the electromagnetic stirring frequency is 5–10 Hz, the stirring time is 15–30 min, and the standing and holding time is 3–5 min.

[0068] In this embodiment, electromagnetic stirring and static flow stabilization technology are employed. Non-contact stirring homogenizes the temperature and composition fields of the melt, while static holding eliminates turbulence and gas entrapment generated during stirring, stabilizing the melt state. This process effectively alleviates compositional segregation in subsequent casting processes, improves the axial composition and microstructure consistency of the target billet, and ensures uniform and stable overall product performance.

[0069] In some embodiments, during the centrifugal casting and rapid cooling steps, the mold needs to be preheated to 150~300°C, and the yttrium metal melt is poured into the mold smoothly and evenly. The temperature of the yttrium metal melt during casting is 1500~1600°C, and the rotation speed of the mold is 200~800 rpm. Rapid cooling is stopped when the casting temperature drops to 150~200°C to obtain the casting billet.

[0070] In this embodiment, during the centrifugal casting process, a preheating range of 150~300℃ avoids molten splashing and cold shut defects caused by rapid cooling of the cold mold during molten casting, while ensuring sufficient flowability of the melt. Matching this with a casting temperature of 1500~1600℃ balances filling performance and solidification quality. This ensures complete filling and good surface quality of the cast billet, while providing a stable foundation for subsequent directional rapid cooling and the acquisition of a fine-grained structure.

[0071] Furthermore, by matching the centrifugal rotation speed of the mold with an extremely rapid cooling rate, the timing of melt solidification is precisely controlled to obtain a fine-grained structure. This fine-grained structure increases grain boundaries, which is beneficial for atomic diffusion and pore closure, resulting in higher densification efficiency during hot isostatic pressing. Moreover, the fine-grained structure ensures uniform stress distribution, eliminating localized stress concentration points and enhancing resistance to thermal stress, thus preventing cracking of the sputtered coating. This process, combined with the preceding electromagnetic stirring process, effectively solves the industry pain points of high difficulty in preparing large-size rotating targets and the tendency for compositional segregation and uneven microstructure.

[0072] In some embodiments, the centrifugal casting and rapid cooling steps include a gas washing operation of the sealed chamber of the sealed furnace before casting: the sealed chamber is evacuated to a vacuum of no more than 1 Pa, and then filled with high-purity argon gas to 100~110 kPa, and this gas washing process is repeated 1~2 times.

[0073] In this embodiment, a circulating gas washing and replacement technology is used to thoroughly remove residual air from the cavity, ensuring a high-purity inert atmosphere throughout the casting and solidification process. This isolates the high-temperature yttrium melt from air, preventing oxidation and nitriding reactions during casting, effectively controlling the increase in oxygen and nitrogen in the billet, and ensuring the purity of the final ingot.

[0074] In some embodiments, during the centrifugal casting and rapid cooling steps, the mold is tubular in shape and made of copper.

[0075] Rapid cooling is achieved through water cooling: the cooling water pressure is 0.6~0.8MPa, and the cooling water temperature is 18~25℃, forming a cooling direction that proceeds from the outer wall towards the center.

[0076] In this embodiment, a copper tubular mold is used because copper has high thermal conductivity, which provides a hardware basis for rapid cooling.

[0077] Meanwhile, high-pressure water-cooled directional solidification technology is employed. The pressure and temperature parameters are set to provide strong heat transfer conditions for the cooling water, ensuring sufficient cooling intensity. The directional cooling from the outer wall to the center controls the solidification sequence of the casting, and combined with centrifugal force, achieves effective feeding. This allows the cooling rate to stably reach no less than 100 K / s, significantly improving the solidification nucleation rate and refining the grains; at the same time, it reduces microstructural inhomogeneity and internal porosity defects along the wall thickness direction.

[0078] Furthermore, the water cooling pipes used in the water cooling method are preferably built-in spiral water cooling channels to ensure uniform cooling throughout the entire area.

[0079] In some embodiments, the hot isostatic pressing step involves heat preservation and pressure holding at a temperature of 900~1000℃ and a pressure of 100~150MPa.

[0080] In this embodiment, during the hot isostatic pressing process, a narrow range of temperature and pressure process parameters are used for control. This temperature provides atoms with sufficient energy to diffuse and eliminate porosity, but is insufficient to drive overall grain boundary migration and grain coarsening. Under the synergistic effect of high temperature and isotropic high pressure, casting defects such as shrinkage cavities, porosity, and microcracks inside the billet can be fully closed without destroying the fine-grained structure formed by rapid cooling, thus achieving the dual effects of billet densification and grain refinement.

[0081] In some embodiments, in the hot isostatic pressing process, the hot isostatic pressing furnace is first evacuated to a vacuum of no more than 1.0 Pa, then filled with high-purity argon gas to 1~2 MPa before heating, with a heating rate of 5~10℃ / min and a holding time of 2~4 h.

[0082] After the heat preservation and pressure holding are completed, depressurization and cooling are carried out. The depressurization rate is 1~2MPa / min, and the gas pressure drops to 10~20MPa after depressurization. The cooling rate is 5~10℃ / min, and an argon atmosphere is maintained during the cooling process.

[0083] In this embodiment, a pre-heat isostatic pressing (HIP) process is employed, involving vacuuming, pre-filling with argon at low pressure, and finally slow heating. This process aims to remove residual air from the furnace and prevent high-temperature oxidation of the yttrium billet during heating. The heating rate parameters are carefully set to ensure uniform heating of the workpiece and prevent thermal stress cracking. The holding and pressure time parameters provide sufficient conditions for atomic diffusion, ensuring thorough pore welding. These process parameters prevent oxidation and oxygenation of the yttrium billet during HIP, allowing the internal pores of the billet to fully collapse and diffuse, significantly improving the ingot density.

[0084] Meanwhile, slow depressurization and slow cooling can smoothly release internal stress and prevent microcracks from forming in the workpiece due to sudden stress changes; the entire process is protected by an argon atmosphere to prevent oxidation of the workpiece surface at high temperatures during cooling. This process ensures the structural integrity of the workpiece after densification treatment, while maintaining the surface purity of the product and avoiding secondary oxidation contamination.

[0085] The following specific embodiments further illustrate the preparation method of the yttrium metal rotating target ingot (hereinafter referred to as yttrium rotating target ingot) according to the present application.

[0086] Example 1

[0087] S1. Vacuum melting and electromagnetic stirring: After cleaning the high-purity Y block, place it into a water-cooled copper crucible, close and seal the furnace door, and evacuate to ≤5.0×10. -3 Pa, adjust the equipment power to heat the furnace to 800℃, hold for 10 minutes for preliminary degassing, after which increase the power to raise the temperature to 1650℃ to completely melt the Y block into a melt, hold for 10 minutes to completely remove gas impurities such as N and O from the melt, after which perform intermittent electromagnetic stirring at a frequency of 5Hz for 30 minutes, stop electromagnetic stirring and let stand for 5 minutes, then transfer the purified melt to the next centrifugal casting station.

[0088] S2. Centrifugal Casting and Rapid Cooling: Before casting, the sealed chamber of the centrifuge must undergo a gas-washing operation. The chamber is closed and evacuated to ≤1 Pa, then high-purity argon is introduced to 110 kPa. This gas-washing process is repeated 1-2 times to ensure that the casting and solidification processes are carried out under an inert atmosphere. The inner cavity of the copper mold is cleaned and polished beforehand, preheated to 300℃, and the casting temperature is 1500℃. The molten material is poured smoothly and uniformly into a high-speed rotating tubular mold through a sealed gating system at 200 rpm. The cooling water valve is activated the instant the molten material contacts the water-cooled copper mold to begin cooling. Rapid cooling is achieved at a rate ≥100 K / s, directionally and rapidly cooling the casting from the outer wall of the mold towards the center. The cooling water pressure is 0.8 MPa, and the cooling water temperature is 18℃, forming a rapid cooling effect along the outer wall of the mold towards the center. Once the casting temperature drops to 200℃, the centrifuge rotation is stopped, and the cooling water is turned off. The formed tubular target blank is then removed from the mold using a special tool.

[0089] S3. Hot Isostatic Pressing (HIP) Treatment: The target blank is ultrasonically cleaned and dried using high-purity anhydrous ethanol in an argon-protected glove box. The target blank is then placed stably on a support in the homogenization zone of the HIP furnace. The vacuum system is activated to evacuate to ≤1.0 Pa, and then high-purity argon is introduced into the chamber to 1 MPa. At this pressure, the furnace temperature is heated to 900°C at a heating rate of 10°C / min. The pressure in the chamber is then increased to 100 MPa and held at this temperature and pressure for 4 hours. After the holding period, the pressure is reduced to 20 MPa at a depressurization rate of 1 MPa / min. Then, under the protection of an argon atmosphere, the furnace temperature is reduced to room temperature at a cooling rate of 5°C / min. After cooling to room temperature, the pressure in the chamber is depressurized to atmospheric pressure and the workpiece is removed.

[0090] S4. Turning: In an argon-protected machining chamber, the ingot is turned and stripped to the required dimensions using a PCD (polydioxanone) tool. A very small amount of pure alcohol is provided during the machining process for lubrication and cooling to prevent overheating and built-up edge on the tool. After machining is completed, the equipment is stopped. After the workpiece has completely cooled, it is placed in a vacuum-sealed bag under an argon atmosphere to prevent air exposure.

[0091] S5. Packaging: Clean the processed ingots with anhydrous ethanol to remove any trace fingerprints or dust. After drying, pack them in two layers. The inner layer is vacuum-sealed with aluminum-plastic composite film and desiccant. The outer layer is filled with high-purity argon gas and sealed. Place them in a high-strength corrugated cardboard box or wooden box.

[0092] Example 2

[0093] S1. Vacuum melting and electromagnetic stirring: After cleaning the high-purity Y block, place it into a water-cooled copper crucible, close and seal the furnace door, and evacuate to ≤1.0×10⁻⁶. -3 Pa, adjust the equipment power to heat the furnace to 1000℃, hold for 5 minutes for preliminary degassing, after which increase the power to raise the temperature to 1550℃ to completely melt the Y block into a melt, hold for 20 minutes to completely remove gaseous impurities such as N and O from the melt, after which perform intermittent electromagnetic stirring at a frequency of 10Hz for 15 minutes, stop electromagnetic stirring and let stand for 3 minutes, then transfer the purified melt to the next centrifugal casting station.

[0094] S2. Centrifugal Casting and Rapid Cooling: Before casting, the sealed chamber of the centrifuge must undergo a gas-washing operation. The chamber is closed and evacuated to ≤1 Pa, then filled with high-purity argon to 100 kPa. This gas-washing process is repeated 1-2 times to ensure that the casting and solidification processes are carried out under an inert atmosphere. The inner cavity of the copper mold is cleaned and polished beforehand, preheated to 150℃, and the casting temperature is 1600℃. The molten material is poured smoothly and uniformly into a high-speed rotating tubular mold through a sealed gating system at 800 rpm. The cooling water valve is activated the instant the molten material contacts the water-cooled copper mold to begin cooling. Rapid cooling is achieved at a rate ≥100 K / s, directed from the outer wall of the mold towards the center of the casting. The cooling water pressure is 0.6 MPa, and the cooling water temperature is 25℃, forming a rapid cooling effect along the outer wall of the mold towards the center. Once the casting temperature drops to 150℃, the centrifuge rotation is stopped, and the cooling water is turned off. The formed tubular target blank is then removed from the mold using a special tool.

[0095] S3. Hot Isostatic Pressing (HIP) Treatment: The target blank is ultrasonically cleaned and dried using high-purity anhydrous ethanol in an argon-protected glove box. The target blank is then placed stably on a support in the homogenization zone of the HIP furnace. The vacuum system is activated to evacuate to ≤1.0 Pa, and then high-purity argon is introduced into the chamber to 2 MPa. At this pressure, the furnace temperature is heated to 1000°C at a heating rate of 5°C / min. The pressure in the chamber is then increased to 150 MPa and held at this temperature and pressure for 2 hours. After the holding period, the pressure is reduced to 10 MPa at a depressurization rate of 2 MPa / min. Then, under the protection of an argon atmosphere, the furnace temperature is reduced to room temperature at a cooling rate of 10°C / min. After cooling to room temperature, the pressure in the chamber is depressurized to atmospheric pressure and the workpiece is removed.

[0096] S4. Turning: In an argon-protected machining chamber, the ingot is turned and stripped to the required dimensions using a PCD (polydioxanone) tool. A very small amount of pure alcohol is provided during the machining process for lubrication and cooling to prevent overheating and built-up edge on the tool. After machining is completed, the equipment is stopped. After the workpiece has completely cooled, it is placed in a vacuum-sealed bag under an argon atmosphere to prevent air exposure.

[0097] S5. Packaging: Clean the processed ingots with anhydrous ethanol to remove any trace fingerprints or dust. After drying, pack them in two layers. The inner layer is vacuum-sealed with aluminum-plastic composite film and desiccant. The outer layer is filled with high-purity argon gas and sealed. Place them in a high-strength corrugated cardboard box or wooden box.

[0098] Comparative Example 1

[0099] S1. Vacuum Melting: After cleaning and drying the surface of Y ingot, place it in a zirconium oxide crucible and use a molecular pump to draw a vacuum ≤3×10⁻⁶. - 2Pa, the temperature is raised to 1550℃ at a heating rate of 100℃ / min to melt the furnace charge, the casting mold is preheated to 450℃, the melt is poured into the mold through a tilting ladle, argon gas is used for protection during the casting process, solidification and feeding are carried out by the weight of the melt itself, and the mold is demolded after natural cooling to 200℃.

[0100] S2. Forging: The ingot is placed in a heating furnace and heated to 800℃ for 2 hours. Multi-directional forging is performed using a forging hammer, with a total forging ratio greater than 3:1.

[0101] S3. Rolling: The forging billet is placed in a heating furnace and heated to 650°C. It is then rolled in multiple passes on a two-roll hot rolling mill, with a deformation of about 10-15% per pass. After the cumulative hot rolling deformation reaches 60%, the billet is placed in an argon atmosphere annealing furnace for intermediate annealing. The holding temperature is 600°C and the holding time is 2 hours. After annealing, it is cold rolled at room temperature with a total deformation of 30%.

[0102] S4. Heat treatment: The rolled billet is placed in the material frame in an orderly manner and sent into an argon atmosphere annealing furnace for recrystallization annealing. The heating temperature is 500℃ and the holding time is 1.5h. After the holding time is completed, the material frame is placed in an argon atmosphere chamber for natural cooling.

[0103] S5. Machining: Use lathes, milling machines and other equipment to process the sheet metal to the final size. After processing, pickling is performed to remove the surface oxide layer.

[0104] The performance of the yttrium metal rotating target ingots prepared in the embodiments and comparative examples was further tested, and the test performance is as follows:

[0105] 1) Oxygen content / Nitrogen content

[0106] The oxygen and nitrogen analyzer heats the sample to over 3000°C, releasing oxygen and nitrogen elements from the material in an inert gas environment. The oxygen content is then detected using the principle of infrared light absorption, and the nitrogen content is determined using a thermal conductivity detector.

[0107] 2) Relative density

[0108] The theoretical basis of the displacement method is Archimedes' principle: an object immersed in a liquid will displace an amount of liquid equal to its volume. The volume difference V2-V1 can be used to accurately determine the object's volume, which can then be combined with its mass to calculate the density. Relative density is the percentage of the actual measured density to the theoretical density.

[0109] 3) Sputtering coating performance

[0110] The ingot is processed into a standard rotating target and continuously sputtered by DC magnetron sputtering; after removal, the entire surface is scanned with the naked eye and a microscope to observe for cracks.

[0111] The test results are shown in Table 1.

[0112] Table 1 Performance test data of yttrium metal rotating target ingots from Examples 1-2 and Comparative Example 1

[0113]

[0114] As shown in Table 1, compared with the forging process of Comparative Example 1, the oxygen content of the yttrium metal rotating target ingots prepared in Examples 1 and 2 of this application is reduced to 148 ppm and 169 ppm, and the nitrogen content is reduced to 40 ppm and 47 ppm, respectively, resulting in a significant improvement in purity. Meanwhile, by eliminating the forging and rolling processes, this method achieves a density of 98.7% and 99.5% for the ingots in Examples 1 and 2 through the synergistic effect of centrifugal force feeding and hot isostatic pressing densification. The higher density eliminates the source of internal defects, and combined with the homogenization effect of the fine-grained structure on stress, the prepared target material does not crack during the sputtering coating process.

[0115] In summary, this application, through innovative process route design, significantly shortens the production cycle and reduces manufacturing costs, while achieving a comprehensive upgrade in the purity, density, and performance of yttrium metal rotating target ingots. It effectively solves the problems of high cost, low efficiency, and difficulty in impurity control in traditional long-process manufacturing.

[0116] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a yttrium metal rotating target ingot, characterized in that, include: Vacuum melting and electromagnetic stirring: Yttrium ingots are vacuum melted, and electromagnetic stirring is used during the vacuum melting process to obtain yttrium metal melt; Centrifugal casting and rapid cooling: The yttrium metal melt is fed into a sealed centrifugal casting system to complete centrifugal casting and directional rapid cooling to prepare the billet. During casting, cooling water is started the instant the yttrium metal melt comes into contact with the inner wall of the mold, and directional rapid cooling is carried out along the outer wall of the mold towards the center at a cooling rate of not less than 100K / s. The billet is subjected to hot isostatic pressing under an inert gas atmosphere to obtain a dense ingot.

2. The method for preparing yttrium metal rotating target ingots according to claim 1, characterized in that, In the vacuum melting and electromagnetic stirring steps, the yttrium block is placed in a water-cooled copper crucible and then placed in a sealed furnace. The yttrium block is heated under vacuum conditions to melt it, and the melt is kept at a constant temperature. The electromagnetic stirring was then performed, and after stirring, the mixture was allowed to stand and be kept at a constant temperature to obtain the yttrium metal melt.

3. The method for preparing yttrium metal rotating target ingots according to claim 2, characterized in that, In the vacuum melting and electromagnetic stirring steps, before heating and melting the yttrium ingot, the sealed furnace is further degassed: the sealed furnace is first evacuated to a vacuum level not exceeding 5.0 × 10⁻⁶. -3 Pa, then heat the furnace to 800~1000℃ and hold for 5~10 minutes.

4. The method for preparing yttrium metal rotating target ingots according to claim 2, characterized in that, In the vacuum melting and electromagnetic stirring steps, the purity of the yttrium block is not less than 99.95%; the melting temperature of the yttrium block is 1550~1650℃, and the melt holding time is 10~20min.

5. The method for preparing yttrium metal rotating target ingots according to claim 2, characterized in that, In the vacuum melting and electromagnetic stirring steps, the electromagnetic stirring frequency is 5-10 Hz and the stirring time is 15-30 min; the standing and heat preservation time is 3-5 min.

6. The method for preparing yttrium metal rotating target ingots according to claim 1, characterized in that, In the centrifugal casting and rapid cooling steps, the mold needs to be preheated to 150~300℃, and the yttrium metal melt is poured into the mold smoothly and evenly. The temperature of the yttrium metal melt during casting is 1500~1600℃, and the rotation speed of the mold is 200~800rpm. Once the casting temperature drops to 150~200℃, the rapid cooling is stopped to obtain the casting billet.

7. The method for preparing the yttrium metal rotating target ingot according to claim 6, characterized in that, In the centrifugal casting and rapid cooling steps, a gas washing operation is also included in the sealed chamber of the sealed furnace before casting: the sealed chamber is evacuated to no more than 1 Pa, and then filled with high-purity argon gas to 100~110 kPa, and this gas washing process is repeated 1~2 times.

8. The method for preparing the yttrium metal rotating target ingot according to claim 6, characterized in that, In the centrifugal casting and rapid cooling steps, the mold is tubular in shape and made of copper. The rapid cooling adopts a water cooling method: the pressure of the cooling water is 0.6~0.8MPa, the temperature of the cooling water is 18~25℃, and the cooling direction is oriented from the outer wall to the center.

9. The method for preparing the yttrium metal rotating target ingot according to claim 1, characterized in that, In the hot isostatic pressing process, heat preservation and pressure holding are performed at a temperature of 900~1000℃ and a pressure of 100~150MPa.

10. The method for preparing the yttrium metal rotating target ingot according to claim 9, characterized in that, In the hot isostatic pressing process, the hot isostatic pressing furnace is first evacuated to a vacuum of no more than 1.0 Pa, then filled with high-purity argon gas to 1~2 MPa before heating. The heating rate is 5~10℃ / min, and the holding time is 2~4h. After the heat preservation and pressure holding are completed, depressurization and cooling are carried out. The depressurization rate is 1~2MPa / min, and the gas pressure drops to 10~20MPa after depressurization. The cooling rate is 5~10℃ / min, and the cooling process is protected by an argon atmosphere.

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