Preparation process of large-size high-purity copper target material

Abstract

The application belongs to the technical field of high-purity metal target material preparation for sputtering film coating, and discloses a preparation process of large-size high-purity copper target material; the process takes high-purity copper smelting master batch as raw material, melts in vacuum and adds copper-based titanium boride interalloy to prepare molten copper liquid, realizes melt purification through electronic beam sectional refining combined with electromagnetic induction stirring, and then prepares copper ingot blank body through directional solidification forming; after the blank body is subjected to vacuum preheating, heat preservation and pressure preservation and hot rolling treatment, cross warm rolling and annealing are carried out under high-purity argon protection, and finally the target material is prepared through turning processing, ultrasonic cleaning and hot air drying; the target material prepared by the application has uniform structure and excellent density, is suitable for high-end sputtering film coating scene, and has good industrial production feasibility.

Description

Technical Field

[0001] This invention belongs to the field of high-purity metal target preparation technology for sputtering coating, specifically relating to a preparation process for a large-size high-purity copper target. Background Technology

[0002] High-purity copper sputtering targets, with their excellent electrical and thermal conductivity and anti-electromigration properties, are the core basic material for sputtering coating in fields such as integrated circuits and flat panel displays. As downstream electronic devices continue to upgrade towards larger sizes and higher precision, the industry has set stringent standards for the purity, oxygen content, density, and microstructure uniformity of copper sputtering targets. The stable preparation of large-size high-purity copper sputtering targets has become a key technical aspect of the industry.

[0003] Existing large-size high-purity copper targets are mostly prepared by combining melting and casting with plastic processing. During the production process, problems such as high oxygen content, residual defects inside the ingot, insufficient grain control, and uneven dispersion of reinforcing phase are prone to occur, which directly affect the density of the target and the uniformity of the sputtered coating.

[0004] Currently, the industry faces prominent issues such as insufficient raw material purification, lack of end-to-end atmosphere protection, and poor integration between melt refining and forming processes. These issues make it difficult to reliably guarantee the comprehensive performance of large-size copper sputtering targets, limiting their application in high-end electronic devices. Therefore, suitable preparation technologies are needed to meet the actual needs of the industry. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present invention provide a preparation process for large-size high-purity copper targets, which solves the problems of insufficient uniformity and density of large-size high-purity copper targets in the prior art.

[0006] To address the above problems, the present invention provides the following technical solution: A process for preparing a large-size high-purity copper target includes the following steps: S1. Take high-purity copper smelting masterbatch and evacuate the cavity until the pressure inside is 3×10⁻⁶. -3 Pa ~ 5 × 10 -3 Pa, heat to 1150℃~1200℃ for melting treatment, hold for 20min~30min, then introduce high-purity argon gas to the cavity pressure to 0.05MPa~0.08MPa, add copper-based titanium boride master alloy, hold for 10min~15min to obtain molten copper liquid; S2. The obtained molten copper liquid is subjected to electron beam segmented refining, maintaining the vacuum level in the refining chamber at 5×10⁻⁶. -5 Pa ~ 1×10 -4Pa, first refine with 100kW~120kW power for 25min~35min, then maintain constant temperature with 60kW~80kW power for 15min~25min, and electromagnetic induction stirring is applied to the molten copper liquid throughout the refining process; S3. The refined molten copper liquid is directionally solidified and shaped. The preheating temperature of the upper part of the directional solidification device is controlled at 650℃~700℃ and the preheating temperature of the lower part is controlled at 550℃~600℃. The temperature gradient along the solidification direction is maintained at 100℃ / cm~150℃ / cm and the solidification rate is 5mm / min~8mm / min to obtain a copper ingot billet. S4. The copper ingot billet is first preheated under vacuum conditions, and then placed in an environment of high-purity argon protection, temperature 850℃~900℃, pressure 120MPa~150MPa for 2h~3h. S5. After heat preservation and pressure treatment, the ingot billet is hot rolled into shape, and the initial rolling temperature is controlled at 800℃~850℃ and the final rolling temperature is controlled at 650℃~720℃. S6. The hot-rolled billet is warm-rolled under a high-purity argon protective atmosphere at a rolling temperature of 350℃~450℃. The warm rolling process adopts intermittent cross rolling. With the rolling direction as the reference, after each 2 to 4 passes of rolling, the billet is rotated 15°~30° around the axis and rolled again. S7. The billet obtained by warm rolling is annealed under a high-purity argon protective atmosphere at a temperature of 250℃~300℃ and a holding time of 1h~2h. After the holding time is completed, it is naturally cooled to room temperature in the furnace. S8. The annealed billet is subjected to rough turning, semi-finish turning, and finish turning in sequence, and then ultrasonic cleaning and hot air drying are performed to complete the preparation.

[0007] Furthermore, the high-purity copper smelting masterbatch in step S1 is prepared by the following method: a copper preform is subjected to vacuum arc remelting, with a vacuum degree of 3 × 10⁻⁶ in the remelting chamber. -3 Pa~8×10 -3The melting current is 1800A~2200A; a constant longitudinal static magnetic field with a magnetic induction intensity of 0.15T~0.30T is applied along the axial direction of the billet, and the magnetic field is continuously applied from the start of arc melting until the molten pool solidifies; after remelting, it is first slowly cooled to 650℃~700℃ in a vacuum environment at a rate of 1℃ / min~3℃ / min, and then switched to a high-purity argon protective atmosphere under normal pressure, using a three-stage gradient cooling: the first stage is cooled from 650℃~700℃ to 500℃~550℃ at a rate of 4℃ / min~5℃ / min; the second stage is cooled from 500℃~550℃ to 300℃~350℃ at a rate of 2℃ / min~3℃ / min; the third stage is cooled from 300℃~350℃ to room temperature at a rate of 1℃ / min~2℃ / min, to obtain high-purity copper smelting masterbatch.

[0008] Furthermore, the copper preform is prepared by the following method: a cathode electrolytic copper substrate with a purity ≥99.995% is surface-polished to remove impurities, and then activated by surface micro-etching using an acidic micro-etching solution based on phosphoric acid, with a micro-etching temperature of 25℃~35℃ and a micro-etching time controlled at 4min~7min; the micro-etched substrate is then calcined under a high-purity argon protective atmosphere, with a heating rate of 3℃ / min~5℃ / min, a calcination temperature of 450℃~500℃, and held at a constant temperature for 1.5h~2.5h, and then cooled to room temperature in the furnace to obtain the copper preform.

[0009] Furthermore, the phosphoric acid system acidic micro-etching solution is made from the following components in parts by weight: 52-60 parts phosphoric acid, 6-8 parts sulfuric acid, 3.5-5 parts hydrogen peroxide, 0.3-0.6 parts benzotriazole copper corrosion inhibitor, and 30.9-38.2 parts deionized water.

[0010] Furthermore, in step S1, the mass fraction of titanium boride in the copper-based titanium boride master alloy is 10% to 20%, and the amount of master alloy added is 0.1% to 0.5% of the mass of the high-purity copper smelting masterbatch.

[0011] Furthermore, the copper-based titanium boride master alloy is prepared by the following method: titanium powder and boron powder are uniformly mixed at a Ti to B molar ratio of 1:2.02 to 1:2.08, and cemented carbide grinding balls are added. The mixture is then ball-milled under the protection of high-purity argon gas. The resulting composite powder is then placed under a vacuum of 3×10⁻⁶. -3 Pa~8×10 -3 In a Pa environment, the temperature is raised to 180℃~220℃ and held for 15min~25min, then an argon gas mixture containing 0.3%~0.7% hydrogen is introduced, and the temperature is further raised to 280℃~320℃ and held for 20min~30min; the cathode copper is then electrolyzed and evacuated to a vacuum of 5×10⁻⁶. -4 Pa ~ 1×10 -3After Pa, the temperature is raised to 1320℃~1340℃ to melt, and high-purity argon gas is introduced to bring the pressure inside the cavity to 0.015MPa~0.025MPa. The composite powder is added to the copper liquid in three equal portions, with a total addition amount of 5%~8% of the copper liquid mass, and an interval of 6min~7min between each addition. Immediately after each addition, a pulsed ultrasonic field is applied for 3min~4min. After all the additions are completed, the temperature is kept constant at 1290℃~1300℃ for 10min~20min, with continuous ultrasonication throughout. After the holding period, rapid cooling is immediately applied by jet cooling at a rate of 25℃ / s~35℃ / s. The mixture is crushed under argon protection and sieved to 20 mesh~40 mesh to obtain a copper-based titanium boride master alloy.

[0012] Furthermore, in step S2, the electromagnetic induction stirring frequency is 50Hz to 100Hz.

[0013] Furthermore, in step S4, the preheating rate is 2℃ / min to 4℃ / min, and after preheating to 400℃ to 500℃, the temperature is maintained at a constant temperature for 30min to 60min.

[0014] Furthermore, in step S8, the finishing cutting speed is 150m / min~200m / min, and the feed rate is 0.05mm / r~0.1mm / r; after cleaning, it is dried with hot air under a high-purity argon protective atmosphere at a drying temperature of 60℃~80℃ for 20min~30min.

[0015] Furthermore, the large-size high-purity copper target has a diameter ≥300mm and a thickness ≥10mm.

[0016] Compared with the prior art, the advantages of the present invention are: This invention uses high-purity copper smelting masterbatch as raw material, which is vacuum melted and supplemented with a copper-based titanium boride master alloy. The entire process is conducted in a high-purity atmosphere, which blocks the high-temperature oxidation path of the melt, maintains the stability of the melt composition, and ensures that the titanium boride phase is uniformly distributed in the matrix melt. Electron beam segmented refining combined with electromagnetic induction stirring achieves deep purification of the melt, removing impurities, ensuring uniform melt temperature and composition, and eliminating melt segregation problems. Directional solidification standardizes the solidification process of the billet, eliminating internal porosity and voids in the ingot, and improving the density and microstructure uniformity of the billet. Vacuum preheating and heat preservation and pressure holding further eliminate internal defects in the billet and enhance the densification effect. Hot rolling improves the plasticity of the billet, and cross-temperature rolling under high-purity argon protection refines the matrix grains, improves the isotropic nature of the billet microstructure, and avoids oxidation problems during rolling. Low-temperature annealing eliminates processing stress in the billet, stabilizes the matrix microstructure, and ensures a uniform and consistent billet microstructure. Step-by-step turning ensures the dimensional accuracy and surface quality of the target material, while ultrasonic cleaning and hot air drying remove impurities from the target surface, preventing secondary oxidation and contamination. The target material of this invention has a uniform structure, high density, and low oxygen content, which meets the process requirements of sputtering coating and supports the large-scale production of large-size high-purity copper targets. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 A process for preparing a large-size high-purity copper target according to the present invention includes the following steps: S1. Take high-purity copper smelting masterbatch and evacuate the cavity to a pressure of 5×10⁻⁶. -3 Pa, heated to 1200℃ for melting treatment, held for 30 min, then high-purity argon gas was introduced until the pressure inside the cavity was 0.08 MPa, copper-based titanium boride master alloy was added, and held for 15 min to obtain molten copper liquid; S2. The obtained molten copper liquid is subjected to electron beam segmented refining, maintaining the vacuum level in the refining chamber at 1×10⁻⁶. -4 Pa, first refine at 120kW power for 35min, then maintain constant temperature at 80kW power for 25min. Electromagnetic induction stirring is applied to the molten copper liquid throughout the refining process, with a stirring frequency of 100Hz. S3. The refined molten copper liquid is directionally solidified and shaped. The preheating temperature of the upper part of the directional solidification device is controlled at 700℃ and the preheating temperature of the lower part is controlled at 600℃. The temperature gradient along the solidification direction is maintained at 150℃ / cm and the solidification rate is 8mm / min to obtain a copper ingot billet. S4. The copper ingot billet is first preheated under vacuum conditions at a preheating rate of 4℃ / min. After preheating to 500℃, it is kept at a constant temperature for 60min. Then it is placed in an environment of high-purity argon protection, temperature of 900℃ and pressure of 150MPa for 3h. S5. After heat preservation and pressure treatment, the ingot billet is hot rolled into shape, with the initial rolling temperature controlled at 850℃ and the final rolling temperature at 720℃. S6. The hot-rolled billet is warm-rolled under a high-purity argon protective atmosphere at a rolling temperature of 450°C. The warm rolling process adopts intermittent cross rolling. With the rolling direction as the reference, after each 4 passes of rolling, the billet is rotated 30° around the axis and rolled again. S7. The billet obtained by warm rolling is annealed under a high-purity argon protective atmosphere at a temperature of 300°C for 2 hours. After the holding time, it is naturally cooled to room temperature in the furnace. S8. The annealed billet is subjected to rough turning, semi-finish turning, and finish turning in sequence. The finish turning cutting speed is 200m / min and the feed rate is 0.1mm / r. Then it is ultrasonically cleaned and hot air dried in a high-purity argon protective atmosphere at a drying temperature of 80℃ for 30min to obtain a large-size high-purity copper target with a diameter of 350mm and a thickness of 15mm.

[0019] The high-purity copper smelting masterbatch is prepared by the following method: a copper preform is subjected to vacuum arc remelting, with a vacuum degree of 8 × 10⁻⁶ in the remelting chamber. -3 Pa, melting current of 2200A, a longitudinal constant static magnetic field with a magnetic induction intensity of 0.30T is applied along the axial direction of the billet. The magnetic field is continuously applied from the start of arc melting until the molten pool solidifies. After remelting, it is first slowly cooled to 700℃ in a vacuum environment at a rate of 3℃ / min, and then switched to a high-purity argon protective atmosphere under normal pressure. A three-stage gradient cooling is adopted. The first stage is cooled from 700℃ to 550℃ at a rate of 5℃ / min, the second stage is cooled from 550℃ to 350℃ at a rate of 3℃ / min, and the third stage is cooled from 350℃ to room temperature at a rate of 2℃ / min to obtain high-purity copper smelting masterbatch.

[0020] The copper preform is prepared by the following method: the surface of a cathode electrolytic copper substrate with a purity of not less than 99.995% is polished to remove impurities, and the surface is activated by micro-etching with an acidic micro-etching solution based on phosphoric acid. The micro-etching temperature is 35℃ and the micro-etching time is controlled at 7min. The micro-etched substrate is then calcined under a high-purity argon protective atmosphere at a heating rate of 5℃ / min and a calcination temperature of 500℃. The calcination is held at a constant temperature for 2.5h and then cooled to room temperature in the furnace to obtain the copper preform.

[0021] The phosphoric acid system acidic micro-etching solution is made from the following components in parts by weight: 60 parts phosphoric acid, 8 parts sulfuric acid, 5 parts hydrogen peroxide, 0.6 parts benzotriazole copper corrosion inhibitor, and 38.2 parts deionized water.

[0022] The copper-based titanium boride master alloy is prepared by the following method: titanium powder and boron powder are uniformly mixed at a Ti to B molar ratio of 1:2.08, and then cemented carbide grinding balls are added. The mixture is then ball-milled under high-purity argon protection. The resulting composite powder is then placed under a vacuum of 8×10⁻⁶. -3 In a Pa environment, the temperature was raised to 220℃ and held for 25 min, then an argon gas mixture containing 0.7% hydrogen was introduced, and the temperature was further raised to 320℃ and held for 30 min; the cathode copper was then electrolyzed and evacuated to a vacuum of 1×10⁻⁶. -3 After Pa, the temperature was raised to 1340℃ to melt, and high-purity argon gas was introduced until the pressure inside the cavity was 0.025MPa. The composite powder was added to the copper liquid in three equal portions, with a total addition amount of 8% of the copper liquid mass and an interval of 7 minutes between each addition. Immediately after each addition, a pulsed ultrasonic field was applied for 4 minutes each time. After all the additions were completed, the temperature was kept constant at 1300℃ for 20 minutes, with continuous ultrasonication throughout. After the holding period, rapid cooling was immediately applied by jet cooling at a rate of 35℃ / s. The mixture was crushed under a high-purity argon protective atmosphere and sieved to 40 mesh to obtain a copper-based titanium boride master alloy, in which the titanium boride mass fraction was 20% and the amount of master alloy added was 0.5% of the mass of the high-purity copper smelting masterbatch.

[0023] Example 2 A process for preparing a large-size high-purity copper target according to the present invention includes the following steps: S1. Take high-purity copper smelting masterbatch and evacuate the cavity until the pressure inside is 4×10⁻⁶. -3 Pa, heated to 1175℃ for melting treatment, held for 25 min, then high-purity argon gas was introduced until the pressure inside the cavity was 0.07 MPa, copper-based titanium boride master alloy was added, and held for 12 min to obtain molten copper liquid; S2. The obtained molten copper liquid is subjected to electron beam segmented refining, maintaining the vacuum level in the refining chamber at 8×10⁻⁶. -5 Pa, first refine at 110kW power for 30min, then maintain constant temperature at 70kW power for 20min. Electromagnetic induction stirring is applied to the molten copper liquid throughout the refining process, with a stirring frequency of 75Hz. S3. The refined molten copper liquid is directionally solidified and shaped. The preheating temperature of the upper part of the directional solidification device is controlled at 675℃ and the preheating temperature of the lower part is controlled at 575℃. The temperature gradient along the solidification direction is maintained at 125℃ / cm and the solidification rate is 6mm / min to obtain a copper ingot billet. S4. The copper ingot billet is first preheated under vacuum conditions at a preheating rate of 3℃ / min. After preheating to 450℃, it is kept at a constant temperature for 45min. Then it is placed in an environment of high-purity argon gas protection, temperature 875℃ and pressure 135MPa for 2.5h. S5. The ingot billet after heat preservation and pressure is hot rolled into shape, with the initial rolling temperature controlled at 825℃ and the final rolling temperature at 685℃. S6. The hot-rolled billet is warm-rolled under a high-purity argon protective atmosphere at a rolling temperature of 400°C. The warm rolling process adopts intermittent cross rolling. With the rolling direction as the reference, after each 3 passes of rolling, the billet is rotated 22° around the axis and rolled again. S7. The billet obtained by warm rolling is annealed under a high-purity argon protective atmosphere at a temperature of 275°C for 1.5 hours. After the holding time, it is naturally cooled to room temperature in the furnace. S8. The annealed billet is subjected to rough turning, semi-finish turning, and finish turning in sequence. The finish turning cutting speed is 175m / min and the feed rate is 0.075mm / r. Then, it is ultrasonically cleaned and dried with hot air under a high-purity argon protective atmosphere at a drying temperature of 70℃ for 25min to obtain a large-size high-purity copper target with a diameter of 320mm and a thickness of 12mm.

[0024] The high-purity copper smelting masterbatch is prepared by the following method: a copper preform is subjected to vacuum arc remelting, with a vacuum degree of 6 × 10⁻⁶ in the remelting chamber. -3 Pa, melting current of 2000A, a longitudinal constant static magnetic field with a magnetic induction intensity of 0.22T is applied along the axial direction of the billet. The magnetic field is continuously applied from the start of arc melting until the molten pool solidifies. After remelting, it is first slowly cooled to 675℃ in a vacuum environment at a rate of 2℃ / min, and then switched to a high-purity argon protective atmosphere under normal pressure. A three-stage gradient cooling is adopted. The first stage is cooling from 675℃ to 525℃ at a rate of 4.5℃ / min, the second stage is cooling from 525℃ to 325℃ at a rate of 2.5℃ / min, and the third stage is cooling from 325℃ to room temperature at a rate of 1.5℃ / min to obtain high-purity copper smelting masterbatch.

[0025] The copper preform is prepared by the following method: the surface of a cathode electrolytic copper substrate with a purity of not less than 99.995% is polished to remove impurities, and the surface is activated by micro-etching with an acidic micro-etching solution based on a phosphoric acid system at a micro-etching temperature of 30°C and a micro-etching time of 5 min; the micro-etched substrate is then calcined under a high-purity argon protective atmosphere at a heating rate of 4°C / min and a calcination temperature of 475°C, held at a constant temperature for 2 h, and then cooled to room temperature in the furnace to obtain the copper preform.

[0026] The phosphoric acid system acidic micro-etching solution is made from the following components in parts by weight: 56 parts phosphoric acid, 7 parts sulfuric acid, 4 parts hydrogen peroxide, 0.5 parts benzotriazole copper corrosion inhibitor, and 34 parts deionized water.

[0027] The copper-based titanium boride master alloy is prepared by the following method: titanium powder and boron powder are uniformly mixed at a Ti to B molar ratio of 1:2.05, and then cemented carbide grinding balls are added. The mixture is then ball-milled under high-purity argon protection. The resulting composite powder is then placed under a vacuum of 6×10⁻⁶. -3 In a Pa environment, the temperature was raised to 200℃ and held for 20 min, then an argon gas mixture containing 0.5% hydrogen was introduced, and the temperature was further raised to 300℃ and held for 25 min; the cathode copper was then electrolyzed and evacuated to a vacuum of 8 × 10⁻⁶. -4 After Pa, the temperature was raised to 1330℃ to melt, and high-purity argon gas was introduced until the pressure inside the cavity was 0.020MPa. The composite powder was added to the copper liquid in three equal portions, with a total addition amount of 6% of the copper liquid mass and an interval of 6.5 min between each addition. A pulsed ultrasonic field was applied immediately after each addition, with each ultrasonication lasting 3.5 min. After all the additions were completed, the temperature was kept constant at 1295℃ for 15 min, with continuous ultrasonication throughout. After the holding period, rapid cooling was immediately applied by jet cooling at a rate of 30℃ / s. The mixture was crushed under a high-purity argon protective atmosphere and sieved to 30 mesh to obtain a copper-based titanium boride master alloy, in which the titanium boride mass fraction was 15%, and the amount of master alloy added was 0.3% of the mass of the high-purity copper smelting masterbatch.

[0028] Example 3 A process for preparing a large-size high-purity copper target according to the present invention includes the following steps: S1. Take high-purity copper smelting masterbatch and evacuate the cavity until the pressure inside is 3×10⁻⁶. -3 Pa, heated to 1150℃ for melting treatment, held for 20 min, then high-purity argon gas was introduced until the pressure inside the cavity was 0.05 MPa, copper-based titanium boride master alloy was added, and held for 10 min to obtain molten copper liquid; S2. The obtained molten copper liquid is subjected to electron beam segmented refining, maintaining the vacuum level in the refining chamber at 5×10⁻⁶. -5 Pa, first refine with 100kW power for 25min, then maintain constant temperature with 60kW power for 15min. Electromagnetic induction stirring is applied to the molten copper liquid throughout the refining process, with a stirring frequency of 50Hz. S3. The refined molten copper liquid is directionally solidified and shaped. The preheating temperature of the upper part of the directional solidification device is controlled at 650℃ and the preheating temperature of the lower part is controlled at 550℃. The temperature gradient along the solidification direction is maintained at 100℃ / cm and the solidification rate is 5mm / min to obtain a copper ingot billet. S4. The copper ingot billet is first preheated under vacuum conditions at a preheating rate of 2℃ / min. After preheating to 400℃, it is kept at a constant temperature for 30min. Then it is placed in an environment of high-purity argon gas protection, temperature 850℃ and pressure 120MPa for 2h. S5. After heat preservation and pressure treatment, the ingot billet is hot rolled into shape, with the initial rolling temperature controlled at 800℃ and the final rolling temperature at 650℃. S6. The hot-rolled billet is warm-rolled under a high-purity argon protective atmosphere at a rolling temperature of 350°C. The warm rolling process adopts intermittent cross rolling. With the rolling direction as the reference, after each two rolling passes, the billet is rotated 15° around the axis and rolled again. S7. The billet obtained by warm rolling is annealed under a high-purity argon protective atmosphere at a temperature of 250°C for 1 hour. After the holding time, it is naturally cooled to room temperature in the furnace. S8. The annealed billet is subjected to rough turning, semi-finish turning, and finish turning in sequence. The finish turning cutting speed is 150m / min and the feed rate is 0.05mm / r. Then, it is ultrasonically cleaned and dried with hot air under a high-purity argon protective atmosphere at a drying temperature of 60℃ for 20min to obtain a large-size high-purity copper target with a diameter of 300mm and a thickness of 10mm.

[0029] The high-purity copper smelting masterbatch is prepared by the following method: a copper preform is subjected to vacuum arc remelting, with a vacuum degree of 3 × 10⁻⁶ in the remelting chamber. -3 Pa, melting current of 1800A, a longitudinal constant static magnetic field with a magnetic induction intensity of 0.15T is applied along the axial direction of the billet. The magnetic field is continuously applied from the start of arc melting until the molten pool solidifies. After remelting, it is first slowly cooled to 650℃ in a vacuum environment at a rate of 1℃ / min, and then switched to a high-purity argon protective atmosphere under normal pressure. A three-stage gradient cooling is adopted. The first stage is cooled from 650℃ to 500℃ at a rate of 4℃ / min, the second stage is cooled from 500℃ to 300℃ at a rate of 2℃ / min, and the third stage is cooled from 300℃ to room temperature at a rate of 1℃ / min to obtain high-purity copper smelting masterbatch.

[0030] The copper preform is prepared by the following method: the surface of a cathode electrolytic copper substrate with a purity of not less than 99.995% is polished to remove impurities, and the surface is activated by micro-etching with an acidic micro-etching solution based on phosphoric acid. The micro-etching temperature is 25℃ and the micro-etching time is controlled at 4min. The micro-etched substrate is then calcined under a high-purity argon protective atmosphere at a heating rate of 3℃ / min and a calcination temperature of 450℃. The calcination is held at a constant temperature for 1.5h and then cooled to room temperature in the furnace to obtain the copper preform.

[0031] The phosphoric acid system acidic micro-etching solution is made from the following components in parts by weight: 52 parts phosphoric acid, 6 parts sulfuric acid, 3.5 parts hydrogen peroxide, 0.3 parts benzotriazole copper corrosion inhibitor and 30.9 parts deionized water.

[0032] The copper-based titanium boride master alloy is prepared by the following method: titanium powder and boron powder are uniformly mixed at a Ti to B molar ratio of 1:2.02, and then cemented carbide grinding balls are added. The mixture is then ball-milled under high-purity argon protection. The resulting composite powder is then placed under a vacuum of 3×10⁻⁶. -3 In a Pa environment, the temperature was raised to 180℃ and held for 15 min, then an argon gas mixture containing 0.3% hydrogen was introduced, and the temperature was further raised to 280℃ and held for 20 min; the cathode copper was then electrolytically removed and evacuated to a vacuum of 5 × 10⁻⁶. -4 After Pa, the temperature was raised to 1320℃ to melt, and high-purity argon gas was introduced until the pressure inside the cavity was 0.015MPa. The composite powder was added to the copper liquid in three equal portions, with a total addition amount of 5% of the copper liquid mass and an interval of 6 minutes between each addition. Immediately after each addition, a pulsed ultrasonic field was applied for 3 minutes each time. After all the additions were completed, the temperature was kept constant at 1290℃ for 10 minutes, with continuous ultrasonication throughout. After the holding period, rapid cooling was immediately applied by jet cooling at a rate of 25℃ / s. The mixture was crushed under a high-purity argon protective atmosphere and sieved to 20 mesh to obtain a copper-based titanium boride master alloy, in which the titanium boride mass fraction was 10% and the amount of master alloy added was 0.1% of the mass of the high-purity copper smelting masterbatch.

[0033] Comparative Example 1 The main difference between this comparative example and Example 1 is that: in step S1, a copper-based titanium boride master alloy was not used, and titanium powder and boron powder mixed raw materials were directly added to the molten copper liquid. The preparation methods of high-purity copper smelting masterbatch, copper preforms, and all other preparation steps and process parameters are exactly the same as in Example 1.

[0034] Comparative Example 2 The main difference between this comparative example and Example 1 is that the warm rolling process in step S6 does not use an intermittent cross rolling process. The preparation methods of high-purity copper smelting masterbatch, copper preform, copper-based titanium boride master alloy, and all other preparation steps and process parameters are exactly the same as in Example 1.

[0035] The testing method is as follows: Oxygen content: Referring to GB / T 5121.8-2022, the target material is processed into a regular sample, and after surface cleaning to remove the oxide layer, it is placed in a pulse melting furnace and melted at high temperature under the protection of high-purity inert gas to release oxygen. The oxygen content is detected and calculated by an infrared detector. Relative density: According to GB / T 3850-2015, the target material sample was degreased and dried, and the dry weight and saturated water weight of the sample were tested respectively. The measured density was calculated, and the relative density was calculated based on the theoretical density of copper. Average grain size: Referring to GB / T 6394-2017, the average grain size was measured in 5 fields of view by metallographic cross section method and the arithmetic mean was taken as the average grain size. Uniformity of the material: The cross-section of the target material was observed in 10 fields of view using a metallographic microscope. The material was graded from 1 to 5 according to the range of grain size fluctuation and the distribution of the second phase: Grade 5: Grain size fluctuation ≤10%, uniform and diffuse second phase without aggregation; Grade 4: Grain size fluctuation 10%-20%, slight local aggregation of the second phase; Grade 3: Grain size fluctuation 20%-30%, local aggregation of the second phase; Grade 2: Grain size fluctuation 30%-40%, significant aggregation of the second phase; Grade 1: Grain size fluctuation >40%, severe aggregation and segregation of the second phase. Sputtered film thickness uniformity: The thickness of the film was measured at 9 points on the coated surface, divided into 8 equal parts at the center and circumference, using a white light interferometer. The film thickness uniformity was calculated as (maximum thickness - minimum thickness) / average thickness × 100%.

[0036] Table 1. Experimental results of Examples 1-3 and Comparative Examples 1-2

[0037] In summary, referring to Table 1, Examples 1-3 of this invention, through the synergistic combination of copper-based titanium boride master alloy, electron beam segmented refining, heat-holding and pressure-pressurization densification, and intermittent cross-rolling processes, can reduce the oxygen content of the target material, increase its relative density, refine the grains, and improve the uniformity of the microstructure, effectively enhancing the uniformity of the sputtered film thickness. In contrast, Comparative Example 1, which did not use a copper-based titanium boride master alloy and directly added titanium-boron mixed powder, easily generated melt oxidation inclusions and uneven dispersion of the second phase, resulting in increased oxygen content, decreased density, coarse grains, and poor microstructure uniformity of the target material, significantly deteriorating the uniformity of the sputtered film. Comparative Example 2, which did not employ an intermittent cross-rolling process, struggled to achieve uniform grain control, leading to larger target grains, insufficient microstructure uniformity, and consequently, reduced uniformity of the sputtered film thickness.

Claims

1. A process for preparing large-size high-purity copper targets, characterized in that, Includes the following steps: S1. Take high-purity copper smelting masterbatch and evacuate the cavity until the pressure inside is 3×10⁻⁶. -3 Pa ~ 5 × 10 -3 Pa, heat to 1150℃~1200℃ for melting treatment, hold for 20min~30min, then introduce high-purity argon gas to the cavity pressure to 0.05MPa~0.08MPa, add copper-based titanium boride master alloy, hold for 10min~15min to obtain molten copper liquid; S2. The obtained molten copper liquid is subjected to electron beam segmented refining, maintaining the vacuum level in the refining chamber at 5×10⁻⁶. -5 Pa ~ 1×10 -4 Pa, first refine with 100kW~120kW power for 25min~35min, then maintain constant temperature with 60kW~80kW power for 15min~25min, and electromagnetic induction stirring is applied to the molten copper liquid throughout the refining process; S3. The refined molten copper liquid is directionally solidified and shaped. The preheating temperature of the upper part of the directional solidification device is controlled at 650℃~700℃ and the preheating temperature of the lower part is controlled at 550℃~600℃. The temperature gradient along the solidification direction is maintained at 100℃ / cm~150℃ / cm and the solidification rate is 5mm / min~8mm / min to obtain a copper ingot billet. S4. The copper ingot billet is first preheated under vacuum conditions, and then placed in an environment of high-purity argon protection, temperature 850℃~900℃, pressure 120MPa~150MPa for 2h~3h. S5. After heat preservation and pressure treatment, the ingot billet is hot rolled into shape, and the initial rolling temperature is controlled at 800℃~850℃ and the final rolling temperature is controlled at 650℃~720℃. S6. The hot-rolled billet is warm-rolled under a high-purity argon protective atmosphere at a rolling temperature of 350℃~450℃. The warm rolling process adopts intermittent cross rolling. With the rolling direction as the reference, after each 2 to 4 passes of rolling, the billet is rotated 15°~30° around the axis and rolled again. S7. The billet obtained by warm rolling is annealed under a high-purity argon protective atmosphere at a temperature of 250℃~300℃ and a holding time of 1h~2h. After the holding time is completed, it is naturally cooled to room temperature in the furnace. S8. The annealed billet is subjected to rough turning, semi-finish turning, and finish turning in sequence, and then ultrasonic cleaning and hot air drying are performed to complete the preparation.

2. The preparation process of the large-size high-purity copper target according to claim 1, characterized in that, The high-purity copper smelting masterbatch in step S1 is prepared by the following method: a copper preform is subjected to vacuum arc remelting, with a vacuum degree of 3 × 10⁻⁶ in the remelting chamber. -3 Pa~8×10 -3 Pa, melting current of 1800A~2200A; a longitudinal constant static magnetic field with a magnetic induction intensity of 0.15T~0.30T is applied along the axial direction of the billet, and the magnetic field is continuously applied from the start of arc melting until the molten pool solidifies. After remelting, the temperature is first slowly cooled to 650℃~700℃ in a vacuum environment at a rate of 1℃ / min~3℃ / min, and then switched to a high-purity argon protective atmosphere at atmospheric pressure, using a three-stage gradient cooling method. The first stage involves cooling the material from 650℃ to 700℃ to 500℃ to 550℃ at a rate of 4℃ / min to 5℃ / min; the second stage involves cooling the material from 500℃ to 550℃ to 300℃ to 350℃ at a rate of 2℃ / min to 3℃ / min; and the third stage involves cooling the material from 300℃ to 350℃ to room temperature at a rate of 1℃ / min to 2℃ / min, thereby obtaining a high-purity copper smelting masterbatch.

3. The preparation process of the large-size high-purity copper target according to claim 2, characterized in that, The copper preform is prepared by the following method: the surface of a cathode electrolytic copper substrate with a purity ≥99.995% is polished to remove impurities, and the surface is activated by micro-etching with an acidic micro-etching solution based on phosphoric acid. The micro-etching temperature is 25℃~35℃, and the micro-etching time is controlled to be 4min~7min. The micro-etched substrate is then calcined under a high-purity argon protective atmosphere with a heating rate of 3℃ / min~5℃ / min and a calcination temperature of 450℃~500℃. The calcination is held at a constant temperature for 1.5h~2.5h, and then cooled to room temperature in the furnace to obtain the copper preform.

4. The preparation process of the large-size high-purity copper target according to claim 3, characterized in that, The phosphoric acid system acidic micro-etching solution is made from the following components in parts by weight: 52-60 parts phosphoric acid, 6-8 parts sulfuric acid, 3.5-5 parts hydrogen peroxide, 0.3-0.6 parts benzotriazole copper corrosion inhibitor, and 30.9-38.2 parts deionized water.

5. The preparation process of the large-size high-purity copper target according to claim 1, characterized in that, In step S1, the mass fraction of titanium boride in the copper-based titanium boride master alloy is 10% to 20%, and the amount of master alloy added is 0.1% to 0.5% of the mass of the high-purity copper smelting masterbatch.

6. The preparation process of the large-size high-purity copper target according to claim 5, characterized in that, The copper-based titanium boride master alloy is prepared by the following method: titanium powder and boron powder are uniformly mixed at a Ti to B molar ratio of 1:2.02 to 1:2.08, and cemented carbide grinding balls are added. The mixture is then ball-milled under the protection of high-purity argon gas. The resulting composite powder is then placed under a vacuum of 3×10⁻⁶. -3 Pa~8×10 -3 In a Pa environment, the temperature is raised to 180℃~220℃ and held for 15min~25min, then an argon gas mixture containing 0.3%~0.7% hydrogen is introduced, and the temperature is further raised to 280℃~320℃ and held for 20min~30min; the cathode copper is then electrolyzed and evacuated to a vacuum of 5×10⁻⁶. - 4 Pa ~ 1×10 -3 After Pa, the temperature is raised to 1320℃~1340℃ to melt, and high-purity argon gas is introduced to bring the pressure inside the cavity to 0.015MPa~0.025MPa. The composite powder is added to the copper liquid in three equal portions, with a total addition amount of 5%~8% of the copper liquid mass, and an interval of 6min~7min between each addition. Immediately after each addition, a pulsed ultrasonic field is applied for 3min~4min. After all the additions are completed, the temperature is kept constant at 1290℃~1300℃ for 10min~20min, with continuous ultrasonication throughout. After the holding period, rapid cooling is immediately applied by jet cooling at a rate of 25℃ / s~35℃ / s. The mixture is crushed under argon protection and sieved to 20 mesh~40 mesh to obtain a copper-based titanium boride master alloy.

7. The preparation process of the large-size high-purity copper target according to claim 1, characterized in that, In step S2, the electromagnetic induction stirring frequency is 50Hz to 100Hz.

8. The preparation process of the large-size high-purity copper target according to claim 1, characterized in that, In step S4, the preheating rate is 2℃ / min to 4℃ / min, and the temperature is maintained at 400℃ to 500℃ for 30min to 60min.

9. The preparation process of the large-size high-purity copper target according to claim 1, characterized in that, In step S8, the finishing cutting speed is 150m / min to 200m / min, and the feed rate is 0.05mm / r to 0.1mm / r. After cleaning, the machine is dried with hot air under a high-purity argon protective atmosphere at a temperature of 60℃ to 80℃ for 20min to 30min.

10. The preparation process of the large-size high-purity copper target according to claim 1, characterized in that, The large-size high-purity copper target has a diameter ≥300mm and a thickness ≥10mm.

Images