High-purity copper-nickel-cobalt alloy target material for semiconductor and preparation process thereof

Abstract

The application relates to the technical field of semiconductor materials, and particularly discloses a high-purity copper-nickel-cobalt alloy target material for semiconductors and a preparation process thereof. The preparation process of the high-purity copper-nickel-cobalt alloy target material for semiconductors comprises the following steps: independently deep-purifying Cu, Ni and Co; atomizing and powdering high-purity Cu, high-purity Ni and high-purity Co respectively; applying a pulse magnetic field at 400-500 DEG C to perform orientation treatment; switching the pulse magnetic field to a direct-current magnetic field after the orientation treatment, and meanwhile performing discharge plasma sintering; and performing stress relief annealing on the sintered compact after cooling. The application independently deep-purifies each element, atomizes and powderizes and mechanically alloyizes to obtain pre-alloy powder, rapidly densifies through discharge plasma sintering, in-situ fixes an orientation structure, maintains a magnetic field in a cooling process to prevent orientation relaxation, and finally obtains a target material with fine-grained structure and strong <111> texture synergy.

Description

Technical Field

[0001] This application relates to the field of semiconductor materials technology, and more specifically, to a high-purity copper-nickel-cobalt alloy target for semiconductors and its preparation process. Background Technology

[0002] As semiconductor chip manufacturing processes advance to 3 nanometers and below, the problems of electron migration and increased resistivity in thin layers of traditional copper interconnects are becoming increasingly prominent. Copper-nickel-cobalt alloys, due to their excellent magnetic properties and resistance to electromigration, are considered ideal candidates for the top electrode of the magnetic tunnel junction or novel interconnect barrier layers in next-generation spin-transfer torque magnetic random access memories. Currently, copper-nickel-cobalt alloy targets are typically prepared using a melting and casting deformation method. First, commercially available high-purity copper, high-purity nickel, and high-purity cobalt are purchased as raw materials and proportioned according to the target atomic ratio. Then, the raw materials are melted and alloyed in a vacuum induction melting furnace or a vacuum arc melting furnace, and cast into alloy ingots. Subsequently, the alloy ingots undergo plastic deformation processing such as forging and rolling, followed by recrystallization annealing to obtain a target blank with a specific grain size and crystal orientation. Finally, the finished target is obtained through machining and backing plate bonding.

[0003] However, grain growth is uncontrollable during the recrystallization process of high-purity alloys, easily leading to coarse grains or bimodal grain structures. In order to obtain... <111> The deformation and annealing processes required for texturing often further exacerbate grain coarsening, which can easily lead to micro-arcs and particulate contamination during sputtering. Summary of the Invention

[0004] To address the problems of micro-arcs and particulate contamination during sputtering caused by existing copper-nickel-cobalt alloy sputtering materials, this application provides a high-purity copper-nickel-cobalt alloy sputtering material for semiconductors and its preparation process.

[0005] This application provides a high-purity copper-nickel-cobalt alloy target for semiconductors and its preparation process, employing the following technical solution: In a first aspect, this application provides a process for preparing a high-purity copper-nickel-cobalt alloy target for semiconductors, employing the following technical solution: A process for preparing a high-purity copper-nickel-cobalt alloy target for semiconductors includes the following steps: S1. Cu, Ni, Co and Y are purified independently to obtain high-purity Cu, high-purity Ni, high-purity Co and high-purity Y; S2. High-purity Cu, high-purity Ni, and high-purity Co are atomized and powdered to obtain spherical powder with a particle size D50 of 10~20μm. High-purity Y is crushed to a particle size ≤10μm and then mixed with the spherical powder and mechanically alloyed to obtain pre-alloyed powder. S3. Load the pre-alloyed powder into the mold, apply a pulsed magnetic field at 400~500℃ for orientation treatment, and hold for 30~60 minutes. S4. After orientation treatment, the pulsed magnetic field is switched to a DC magnetic field, and the sample is heated to 950-1050°C by spark plasma sintering at a heating rate of 80-120°C / min, held for 5-10 min, and subjected to an axial pressure of 40-60 MPa to obtain a sintered green body. After sintering, the sample is cooled at a cooling rate of 20-30°C / min, and a DC magnetic field is continued to be applied during the cooling process until the temperature drops below 300°C. S5. After cooling, the sintered blank is subjected to stress-relief annealing, then machined to the target size and bound to the back plate to obtain the target material.

[0006] By adopting the above technical solution, the ultra-high purity of raw materials is ensured through independent deep purification of each element. Pre-alloyed powder is obtained through atomization powdering and mechanical alloying. After the powder particles are oriented and aligned in a magnetic field, rapid densification is achieved through spark plasma sintering, fixing the oriented structure in situ. The magnetic field is maintained during cooling to prevent orientation relaxation. Therefore, a fine-grained structure and high strength are obtained. <111> The textured sputtering target solves the problems of micro-arcs and particulate contamination caused by the coarse grains and random texture of existing sputtering targets.

[0007] Preferably, in step S1, the independent deep purification of Cu, Ni, Co, and Y specifically includes the following steps: Cu was purified by electrolytic refining and zone melting to obtain high-purity Cu. The electrolyte composition of the electrolytic refining was Cu². + 40~50g / L, H2SO4 150~180g / L, electrolysis temperature 50~60℃, current density 200~300A / m², the zone melting is carried out in a flowing high-purity hydrogen atmosphere, the zone melting speed is 2~5mm / min, and the number of zone meltings is ≥3 times. Ni is purified by carbonylation refining and electron beam melting to obtain high-purity Ni. The carbonylation reaction temperature in the carbonylation refining process is 50-80℃, the top temperature of the distillation column is 40-45℃, the bottom temperature is 55-60℃, and the thermal decomposition temperature is 200-250℃. The vacuum degree of the electron beam melting process is ≤1×10⁻⁶. - ³Pa, power is 15~25kW; High-purity Co was purified by extraction separation and plasma melting. The extraction separation had an extraction ratio of O / A = 1:1 to 2:1 and 8 to 10 extraction stages. The plasma melting was carried out in an Ar-H2 mixed atmosphere with an H2 volume ratio of 5 to 10% and a vacuum degree ≤1×10⁻⁶. - ²Pa, power 20~30kW; Y was purified by vacuum distillation and solid-state electro-deoxygenation to obtain high-purity Y, wherein the vacuum degree of the vacuum distillation was ≤1×10⁻⁶. - The solid electrodeoxidation is carried out in CaCl2 molten salt at a distillation temperature of 1650~1750℃, an electrolysis temperature of 850~950℃, a voltage of 2.5~3.5V, and an electrolysis time of 10~20h.

[0008] By adopting the above technical solutions, Cu, Ni, and Co are independently purified using electrolytic refining and zone melting, carbonyl refining and electron beam melting, and extraction separation and plasma melting processes, respectively. This can specifically remove the characteristic impurities of each element and obtain semiconductor-grade ultra-high purity raw materials. Y is independently purified using vacuum distillation and solid-state electro-deoxidation to obtain high-purity rare earth elements. This achieves targeted purification of the entire elemental impurity spectrum and provides a pure raw material basis for subsequent multi-element rare earth synergistic doping and the formation of fine-grained texture.

[0009] Preferably, in step S2, the mass percentages of Cu, Ni and Co in the spherical powder are 30-50%, 25-35% and 25-35% respectively, and the total doping amount of high-purity Y is 0.01-0.05 wt%.

[0010] By employing the above technical solution and limiting the mass percentages of Cu, Ni, and Co, grain boundary pinning and texture-inducing effects can be achieved through rare-earth Y doping, while ensuring the intrinsic properties of the matrix alloy. Y mainly segregates at grain boundaries to form a pinning layer, inhibiting grain growth and promoting… <111> Oriented growth avoids the problems of insufficient pinning when the doping level is too low or the formation of segregated clusters when the doping level is too high.

[0011] Preferably, in step S2, the ball milling time for mechanical alloying is 8~12h, the ball milling speed is 200~250rpm, the ball-to-material ratio is 8:1~12:1, the ball milling jar is made of WC-Co or ZrO2, and the ball milling is carried out under argon protection. During the ball milling process, the machine is stopped every 1h for cooling and reverse rotation.

[0012] By adopting the above technical solution, the ball milling time, speed and ball-to-material ratio of mechanical alloying are controlled. A ball milling jar made of WC-Co or ZrO2 material is used and ball milling is carried out under argon protection. At the same time, the machine is stopped for cooling and rotated in reverse every 1 hour. This can control the degree of oxidation and temperature accumulation of the powder while ensuring uniform mixing of powder components, and avoid powder agglomeration or grain coarsening due to overheating.

[0013] Preferably, in step S2, the micro-strain of the pre-alloyed powder is 0.15~0.25%.

[0014] By adopting the above technical solution, the micro-strain of the pre-alloyed powder can introduce an appropriate amount of deformation energy storage into the powder particles. In the subsequent magnetic field orientation process, the stress release assists the particle rotation, thereby improving the orientation efficiency. This not only provides sufficient orientation driving force but also avoids excessive strain leading to severe powder work hardening.

[0015] Preferably, in step S3, the intensity of the pulsed magnetic field is 12~18T and the frequency is 1~10Hz.

[0016] By adopting the above technical solution, the pulsed magnetic field can generate sufficiently strong magnetic torque to drive powder particles to rotate during the orientation process. Simultaneously, frequency adjustment optimizes the micro-region rearrangement between particles, improving... <111> The alignment efficiency of the easily magnetized axes along the magnetic field direction, and the matching of magnetic field strength and frequency, can balance the orientation driving force and orientation uniformity, laying the foundation for obtaining strong... <111> The texture lays the foundation.

[0017] Preferably, in step S4, the strength of the DC magnetic field is 11~13T.

[0018] By adopting the above technical solution, the DC magnetic field strength can stably maintain the obtained orientation structure during the sintering stage, preventing orientation disorder caused by grain rotation at high temperatures. The matching of magnetic field strength with sintering temperature and holding time can achieve synergy between orientation fixation and rapid densification, ensuring that the sintered green body simultaneously possesses high density and strength. <111> Texture.

[0019] Preferably, in step S5, the stress-relief annealing temperature is 600~700℃, the holding time is 2~4h, and the vacuum degree is ≤1×10 - ³Pa.

[0020] By adopting the above technical solution, stress-relief annealing and holding time can eliminate the residual stress generated during sintering and cooling, while avoiding excessively high annealing temperatures that could lead to grain growth and damage to the obtained fine-grained structure. This annealing process can optimize the grain boundary structure, further improve the structural stability of the target material, and provide a guarantee for subsequent sputtering applications.

[0021] Preferably, in step S5, the backplate bonding adopts indium soldering process, with bonding temperature of 180~200℃, pressure of 10~20MPa, and heat and pressure holding time of 10~15min.

[0022] By adopting the above technical solution and using indium soldering for backplate bonding, it is possible to avoid the impact of high-temperature bonding on the target microstructure and texture while ensuring the bonding strength between the target and the backplate, thus meeting the requirements of magnetron sputtering equipment for target components.

[0023] Secondly, this application provides a high-purity copper-nickel-cobalt alloy target for semiconductors, employing the following technical solution: A high-purity copper-nickel-cobalt alloy target for semiconductors is prepared by the above-mentioned preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors.

[0024] By adopting the above technical solution and the preparation process, the target material obtained has the characteristics of ultra-high purity, fine grain structure, and high strength. <111> The texture exhibits synergistic characteristics, with uniform and fine grain size, high texture strength, and good uniformity of sputtered film thickness. The fabricated magnetic tunnel junction device achieves a high TMR value improvement rate, which can meet the requirements of advanced semiconductor devices for the target material.

[0025] In summary, this application has the following beneficial effects: 1. Because this application employs independent deep purification of each element to ensure ultra-high purity of the raw materials, pre-alloyed powder is obtained through atomization powdering and mechanical alloying. After the powder particles are oriented and aligned in a magnetic field, rapid densification is achieved through spark plasma sintering, fixing the oriented structure in situ. The magnetic field is maintained during cooling to prevent orientation relaxation. Therefore, a fine-grained structure and strong... <111> The textured sputtering target solves the problems of micro-arcs and particulate contamination caused by the coarse grains and random texture of existing sputtering targets.

[0026] 2. This application achieves a pinning effect in fine-grained texture enhancement through rare-earth Y doping. Y segregates at grain boundaries to form a pinning layer, inhibiting grain growth and promoting grain growth. <111> Oriented growth.

[0027] 3. This application establishes a complete orientation control system through full-process control of magnetic field orientation, encompassing pulsed magnetic field heating and orientation, DC magnetic field holding and sintering, and magnetic field maintenance during cooling. During the orientation stage, a pulsed magnetic field is applied to fully rotate and align the powder particles; during the sintering stage, a DC magnetic field is applied to fix the orientation structure; and during the cooling stage, the magnetic field is maintained to prevent orientation relaxation. This achieves stable control of the orientation structure throughout the entire process, ensuring the target material achieves strong magnetic field strength. <111> Texture. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors provided in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Technical Concept: With the continuous miniaturization of semiconductor chip manufacturing processes, copper-nickel-cobalt alloy sputtering targets, as key materials for novel memory devices, directly influence the quality of sputtered thin films and device performance through their microstructure and crystal texture. However, when using traditional casting deformation methods to prepare targets, the grain growth of high-purity alloys becomes uncontrollable during recrystallization, easily leading to coarse grains or bimodal grain structures. To obtain the desired... <111> Texture deformation and annealing processes often further exacerbate grain coarsening, leading to micro-arcs and particulate contamination during sputtering.

[0031] To address the aforementioned issues, this application employs a complete technological chain combining independent deep purification, rare-earth Y doping, strong magnetic field orientation, and spark plasma sintering. This overcomes the bottleneck of simultaneously achieving fine grain structure and strong texture. Rare-earth Y can segregate at grain boundaries to form a pinning layer, inhibiting grain growth and promoting grain development. <111> Orientation growth; simultaneously, a pulsed magnetic field is applied during the orientation stage to fully rotate and align the powder particles, a DC magnetic field is applied during the sintering stage to fix the orientation structure, and the magnetic field is maintained during the cooling process to prevent orientation relaxation. This enables stable control of the orientation structure throughout the entire process, solving the problems of micro-arcs and particle contamination during sputtering caused by the large grain size and random texture of existing targets.

[0032] Unless otherwise specified, all experimental methods used below are conventional methods. All materials, reagents, methods, and instruments used, unless otherwise specified, are conventional materials, reagents, methods, and instruments in this field, which can be obtained commercially or prepared according to literature methods by those skilled in the art.

[0033] Preparation Example 1: Preparation of High-Purity Cu Electrolytic copper with a purity of 99.99% was used as raw material and placed in an electrolytic cell for electrolytic refining. The electrolyte composition was Cu²⁺. + The cathode copper sheet obtained by electrolysis was 45 g / L, H2SO4 165 g / L, electrolysis temperature 55℃, current density 250 A / m², electrode spacing 40 mm. After being cleaned and dried with deionized water, it was placed in a zone melting furnace for multi-pass zone melting purification. The zone melting was carried out in a flowing high-purity hydrogen atmosphere with a flow rate of 0.8 L / min, the zone melting heating coil moving speed was 3.5 mm / min, the melting zone width was 12 mm, and the number of zone meltings was 3 times, to obtain high-purity Cu with U and Th contents <0.1 ppb.

[0034] Preparation Example 2: Preparation of High-Purity Ni Crude nickel was placed in a reaction vessel, and high-purity CO gas was introduced. The reaction proceeded at 65°C and atmospheric pressure to produce Ni(CO)₄ gas. The resulting mixed gas was cooled to 2°C and condensed, then compressed to 0.8 MPa before entering a distillation column. The distillation column had 25 theoretical plates, with the top temperature controlled at 42.5°C and the bottom temperature at 57.5°C. The top fraction was collected, and the purified Ni(CO)₄ was decomposed in a thermal decomposition furnace at 225°C to obtain nickel powder. The nickel powder was pressed into blocks at 250 MPa and then placed in an electron beam melting furnace with a vacuum degree ≤1×10⁻⁶. - ³Pa, electron beam power 20kW, melting time 25min, to obtain high-purity Ni with Fe and Co content <10ppb.

[0035] Preparation Example 3: Preparation of High-Purity Co Using crude cobalt salt solution as raw material, Co² + A cobalt solution with a concentration of 25 g / L was subjected to multi-stage countercurrent extraction using a P204 extraction system. The organic phase composition was 22 vol% P204 + 12 vol% TBP + sulfonated kerosene, with a saponification rate of 65%. The extraction ratio was O / A = 1.5:1, with 9 extraction stages, 4 washing stages, and 5 back-extraction stages. Oxalic acid was added to the resulting high-purity cobalt solution at 1.15 times the theoretical amount. Precipitation was carried out at 55℃ and pH 1.8 for 2.5 h. After filtration and washing, the precipitate was dried at 110℃ and then calcined at 450℃ for 2.5 h to obtain cobalt oxide. The cobalt oxide was reduced in a tube furnace under a hydrogen atmosphere at a flow rate of 1.5 L / min and a reduction temperature of 850℃ for 5 h to obtain cobalt powder. The cobalt powder was briquetted and placed in a plasma melting furnace under an Ar-H2 mixture atmosphere with an H2 volume ratio of 7.5% and a vacuum degree ≤1×10⁻⁶. - At 2 Pa, plasma power of 25 kW, and melting time of 25 min, high-purity Co was obtained with an O content of 45 ppm and a C content of 15 ppm.

[0036] Preparation Example 4: Preparation of High-Purity Y Using commercially available Y metal with a purity of approximately 99% as raw material, it is purified by distillation in a vacuum induction furnace with a vacuum degree ≤1×10⁻⁶. - The distillation process was carried out at 1700℃ for 3 hours, with a condensation temperature of 450℃, and the condensate was collected. The distilled Y metal was placed in a solid-state electro-deoxidation apparatus, with Y metal as the cathode, high-purity graphite as the anode, and anhydrous CaCl2 (purity ≥99.9%) as the molten salt. The electrolysis temperature was 900℃, the voltage was 3V, and the electrolysis time was 15 hours. The entire process was carried out under argon protection. The electrolyzed Y metal was washed and dried with anhydrous ethanol to obtain high-purity Y with an O content of 80 ppm.

[0037] To better understand the above technical solutions, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0038] The following is a further description with reference to the embodiments: Example 1: Please refer to the appendix Figure 1 A process for preparing a high-purity copper-nickel-cobalt alloy target for semiconductors includes the following steps: S1. Cu, Ni, Co and Y are purified independently to obtain high-purity Cu, high-purity Ni, high-purity Co and high-purity Y; S2. High-purity Cu, high-purity Ni, and high-purity Co are atomized and powdered to obtain spherical powder with a particle size D50=15μm. High-purity Y is crushed to a particle size ≤10μm and mixed with the spherical powder, and then mechanically alloyed to obtain pre-alloyed powder. S3. Load the pre-alloyed powder into the mold, apply a pulsed magnetic field at 450°C for orientation treatment, and hold for 45 minutes. S4. After orientation treatment, the pulsed magnetic field is switched to a DC magnetic field, and the sample is heated to 1000°C at a heating rate of 100°C / min and held for 7.5 min with an axial pressure of 50 MPa to obtain a sintered green body. After sintering, the sample is cooled at a cooling rate of 25°C / min, and a DC magnetic field is continued to be applied during the cooling process until the temperature drops below 300°C. S5. After cooling, the sintered blank is subjected to stress-relief annealing, then machined to the target size and bound to the back plate to obtain the target material.

[0039] In step S1, Cu, Ni, Co, and Y are individually and deeply purified, specifically including the following steps: Cu was purified by electrolytic refining and zone melting to obtain high-purity Cu. The electrolyte composition for electrolytic refining was Cu². + 45 g / L, H2SO4 165 g / L, electrolysis temperature 55℃, current density 250 A / m², zone melting is carried out in a flowing high-purity hydrogen atmosphere, zone melting speed 3.5 mm / min, zone melting times ≥ 3 times; Ni was purified by carbonylation and electron beam melting to obtain high-purity Ni. The carbonylation reaction temperature in the carbonylation process was 65℃, the top temperature of the distillation column was 42.5℃, the bottom temperature was 57.5℃, and the thermal decomposition temperature was 225℃. The vacuum degree of the electron beam melting was ≤1×10⁻⁶. - ³Pa, power is 20kW; Co was purified by extraction separation and plasma melting to obtain high-purity Co. The extraction separation ratio was O / A = 1.5:1, with 9 extraction stages. The plasma melting was carried out in an Ar-H2 mixed atmosphere with an H2 volume ratio of 7.5% and a vacuum degree ≤1×10⁻⁶. - ²Pa, power 25kW; Y was purified by vacuum distillation and solid-state electro-deoxygenation to obtain high-purity Y. The vacuum degree of vacuum distillation was ≤1×10⁻⁶. - The solid electrodeoxidation was carried out in CaCl2 molten salt at a temperature of 900℃, a voltage of 3V, and a time of 15h. The distillation temperature of La was 1750℃, the distillation temperature of Ce was 1650℃, and the distillation temperature of Y was 1700℃. The solid electrodeoxidation was carried out in CaCl2 molten salt at a temperature of 900℃, a voltage of 3V, and a time of 15h.

[0040] In step S2, the mass percentages of Cu, Ni and Co in the spherical powder are 40%, 30% and 30% respectively, and the total doping amount of high-purity Y is 0.03wt%.

[0041] In step S2, the ball milling time for mechanical alloying is 10 hours, the ball milling speed is 225 rpm, the ball-to-material ratio is 10:1, the ball milling jar is made of WC-Co or ZrO2, and the ball milling is carried out under argon protection. During the ball milling process, the machine is stopped every 1 hour for cooling and reverse rotation.

[0042] In step S2, the microstrain of the pre-alloyed powder is 0.2%.

[0043] In step S3, the intensity of the pulsed magnetic field is 15T and the frequency is 5.5Hz.

[0044] In step S4, the intensity of the DC magnetic field is 12T.

[0045] In step S5, the stress-relief annealing temperature is 650℃, the holding time is 3 hours, and the vacuum degree is ≤1×10⁻⁶. - ³Pa.

[0046] In step S5, the backplate is bonded using indium soldering, with a bonding temperature of 190℃, a pressure of 15MPa, and a holding time of 12.5min.

[0047] A high-purity copper-nickel-cobalt alloy target for semiconductors is prepared by the above-mentioned preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors.

[0048] Example 2: This example differs from Example 1 above in that: A process for preparing a high-purity copper-nickel-cobalt alloy target for semiconductors includes the following steps: S1. Cu, Ni, Co and Y are purified independently to obtain high-purity Cu, high-purity Ni, high-purity Co and high-purity Y; S2. High-purity Cu, high-purity Ni, and high-purity Co are atomized and powdered to obtain spherical powder with a particle size D50=20μm. High-purity Y is crushed to a particle size ≤10μm and mixed with the spherical powder. Mechanical alloying is then performed to obtain pre-alloyed powder. S3. Load the pre-alloyed powder into the mold, apply a pulsed magnetic field at 500℃ for orientation treatment, and hold for 60 minutes. S4. After orientation treatment, the pulsed magnetic field is switched to a DC magnetic field, and the sample is heated to 1050°C at a heating rate of 120°C / min and held for 10 min with an axial pressure of 60 MPa to obtain a sintered green body. After sintering, the sample is cooled at a cooling rate of 30°C / min, and a DC magnetic field is continued to be applied during the cooling process until the temperature drops below 300°C. S5. After cooling, the sintered blank is subjected to stress-relief annealing, then machined to the target size and bound to the back plate to obtain the target material.

[0049] In step S1, the process of independently purifying Cu, Ni, Co, and Y specifically includes the following steps: Cu was purified by electrolytic refining and zone melting to obtain high-purity Cu. The electrolyte composition of the electrolytic refining was Cu². + The concentrations of H2SO4 and H2SO4 are 50 g / L, the electrolysis temperature is 60℃, the current density is 300 A / m², and the zone melting is carried out in a flowing high-purity hydrogen atmosphere with a melting speed of 5 mm / min and ≥3 melting cycles. Ni was purified by carbonylation refining and electron beam melting to obtain high-purity Ni. The carbonylation reaction temperature in the carbonylation refining process was 80℃, the distillation column top temperature was 45℃, the column bottom temperature was 60℃, and the thermal decomposition temperature was 250℃. The vacuum degree in the electron beam melting process was ≤1×10⁻⁶. - ³Pa, power is 25kW; High-purity Co was obtained by extraction separation and plasma melting. The extraction separation had an O / A ratio of 2:1 and 10 extraction stages. The plasma melting was carried out in an Ar-H2 mixed atmosphere with an H2 volume ratio of 10% and a vacuum degree ≤1×10⁻⁶. - ²Pa, power 30kW; Y was purified by vacuum distillation and solid-state electro-deoxygenation to obtain high-purity Y, wherein the vacuum degree of the vacuum distillation was ≤1×10⁻⁶. - The solid electrodeoxidation was carried out in CaCl2 molten salt at a distillation temperature of 1750℃ and a voltage of 3.5V for 20h. The electrolysis temperature was 950℃ and the voltage was 3.5V.

[0050] In step S2, the mass percentages of Cu, Ni and Co in the spherical powder are 50%, 35% and 35% respectively, and the total doping amount of high-purity Y is 0.05wt%.

[0051] In step S2, the ball milling time for mechanical alloying is 12 hours, the ball milling speed is 250 rpm, the ball-to-material ratio is 12:1, the ball milling jar is made of WC-Co or ZrO2, and the ball milling is carried out under argon protection. During the ball milling process, the machine is stopped every 1 hour for cooling and reverse rotation.

[0052] In step S2, the micro-strain of the pre-alloyed powder is 0.25%.

[0053] In step S3, the intensity of the pulsed magnetic field is 18T and the frequency is 10Hz.

[0054] In step S4, the intensity of the DC magnetic field is 13T.

[0055] In step S5, the stress-relief annealing temperature is 700℃, the holding time is 4 hours, and the vacuum degree is ≤1×10⁻⁶. - ³Pa.

[0056] In step S5, the backplate bonding adopts indium soldering process, with bonding temperature of 200℃, pressure of 20 MPa, and heat and pressure holding time of 15 min.

[0057] A high-purity copper-nickel-cobalt alloy target for semiconductors is prepared by the above-mentioned preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors.

[0058] Example 3: This example differs from Example 1 above in that: A process for preparing a high-purity copper-nickel-cobalt alloy target for semiconductors includes the following steps: S1. Cu, Ni, Co and Y are purified independently to obtain high-purity Cu, high-purity Ni, high-purity Co and high-purity Y; S2. High-purity Cu, high-purity Ni, and high-purity Co are atomized and powdered to obtain spherical powder with a particle size D50=10μm. High-purity Y is crushed to a particle size ≤10μm and mixed with the spherical powder. Mechanical alloying is then performed to obtain pre-alloyed powder. S3. Load the pre-alloyed powder into the mold, apply a pulsed magnetic field at 400℃ for orientation treatment, and hold for 30 minutes. S4. After orientation treatment, the pulsed magnetic field is switched to a DC magnetic field, and the sample is heated to 950°C at a heating rate of 80°C / min and held for 5 minutes with an axial pressure of 40MPa to obtain a sintered green body. After sintering, the sample is cooled at a cooling rate of 20°C / min, and a DC magnetic field is continued to be applied during the cooling process until the temperature drops below 300°C. S5. After cooling, the sintered blank is subjected to stress-relief annealing, then machined to the target size and bound to the back plate to obtain the target material.

[0059] In step S1, the process of independently purifying Cu, Ni, Co, and Y specifically includes the following steps: Cu was purified by electrolytic refining and zone melting to obtain high-purity Cu. The electrolyte composition of the electrolytic refining was Cu². + 40 g / L, H2SO4 150 g / L, electrolysis temperature 50℃, current density 200 A / m², the zone melting is carried out in a flowing high-purity hydrogen atmosphere, the zone melting speed is 2 mm / min, and the number of zone meltings is ≥3 times; Ni is purified by carbonylation refining and electron beam melting to obtain high-purity Ni. The carbonylation reaction temperature in the carbonylation refining process is 50℃, the distillation column top temperature is 40℃, the column bottom temperature is 55℃, and the thermal decomposition temperature is 200℃. The vacuum degree in the electron beam melting process is ≤1×10⁻⁶. - ³Pa, power is 15kW; High-purity Co was obtained by extraction separation and plasma melting. The extraction separation had an O / A ratio of 1:1 and consisted of 8 extraction stages. The plasma melting was carried out in an Ar-H2 mixed atmosphere with an H2 volume ratio of 5% and a vacuum degree ≤1×10⁻⁶. - ²Pa, power 20kW; Y was purified by vacuum distillation and solid-state electro-deoxygenation to obtain high-purity Y, wherein the vacuum degree of the vacuum distillation was ≤1×10⁻⁶. - The solid electrodeoxidation was carried out in CaCl2 molten salt at a distillation temperature of 1650℃ and a voltage of 2.5V for 10h. The electrolysis temperature was 850℃ and the voltage was 2.5V.

[0060] In step S2, the mass percentages of Cu, Ni and Co in the spherical powder are 30%, 25% and 25% respectively, and the total doping amount of high-purity Y is 0.01wt%.

[0061] In step S2, the ball milling time for mechanical alloying is 8~12h, the ball milling speed is 200rpm, the ball-to-material ratio is 8:1, the ball milling jar is made of WC-Co or ZrO2, and the ball milling is carried out under argon protection. During the ball milling process, the machine is stopped every 1h for cooling and reverse rotation.

[0062] In step S2, the micro-strain of the pre-alloyed powder is 0.15%.

[0063] In step S3, the intensity of the pulsed magnetic field is 12T and the frequency is 1Hz.

[0064] In step S4, the intensity of the DC magnetic field is 11T.

[0065] In step S5, the stress-relief annealing temperature is 600℃, the holding time is 2 hours, and the vacuum degree is ≤1×10⁻⁶.- ³Pa.

[0066] In step S5, the backplate bonding adopts indium soldering process, with bonding temperature of 180℃, pressure of 10MPa, and heat and pressure holding time of 10min.

[0067] A high-purity copper-nickel-cobalt alloy target for semiconductors is prepared by the above-mentioned preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors.

[0068] Comparative Example 1: A preparation process for a copper-nickel-cobalt alloy target material, comprising the following steps: Take commercially available electrolytic copper plates with a purity of 99.99%, electrolytic nickel plates with a purity of 99.95%, and electrolytic cobalt plates with a purity of 99.95%, and mix them in a mass ratio of 40:30:30. The raw materials are placed in a vacuum induction melting furnace with a vacuum degree ≤1×10⁻⁶. - ² Pa, heated to 1500℃ and smelted for 30 min, then cast into a copper mold to obtain an ingot; The ingot was homogenized and annealed at 1000℃ for 24 h, then subjected to multi-pass hot rolling at 900℃ with a total deformation of 70%, and finally recrystallized and annealed at 800℃ for 2 h to obtain the target billet. The blank is machined to the target size and then bound to the back plate to obtain the target material.

[0069] Comparative Example 2: This comparative example differs from Example 1 above in that: No rare earth element Y is added in step S2.

[0070] Comparative Example 3: This comparative example differs from Example 1 above in that: The total doping amount of high-purity Y in step S2 is 0.06 wt%.

[0071] Comparative Example 4: This comparative example differs from Example 1 above in that: The total doping amount of high-purity Y in step S2 is 0.005 wt%.

[0072] Comparative Example 5: This comparative example differs from Example 1 above in that: In step S2, the total doping concentration of La, Ce, and Y is 0.1 wt%. Comparative Example 6: This comparative example differs from Example 1 above in that: In step S3, no pulsed magnetic field is applied for orientation treatment; the pre-alloyed powder is directly sintered by SPS. No DC magnetic field is applied in step S4.

[0073] Comparative Example 7: This comparative example differs from Example 1 above in that: In step S4, no DC magnetic field is applied during the cooling process; the cooling occurs naturally.

[0074] Performance testing: Target purity testing: The content of impurity elements in the target material was detected by glow discharge mass spectrometry, and the total purity was calculated; Average grain size: Statistical analysis of grain size of the target cross-section was performed using electron backscatter diffraction. <111> Texture intensity: The pole figure of the sputtered surface of the target was determined by X-ray diffraction, and the Lotgering factor was calculated to characterize the texture. <111> Texture strength; Thin film thickness uniformity: The target was mounted in a magnetron sputtering apparatus to deposit a CuNiCo thin film with a thickness of 100 nm on a silicon wafer with a diameter of 200 mm. The film thickness was measured at 9 points on the silicon wafer using a profilometer, and the thickness uniformity was calculated as ((maximum value - minimum value) / (2 × average value) × 100%). TMR value improvement rate: The thin film sputtered from the target is used to prepare a magnetic tunnel junction device. The tunneling magnetoresistance ratio (TMR) of the device is tested. The TMR value improvement rate of each embodiment and the comparative example is calculated with the TMR value of Comparative Example 1 as a baseline (set to 0%).

[0075] Table 1

[0076] Combining Examples 1 to 3 and Comparative Examples 1 to 7 with Table 1, it can be seen that the preparation process combining independent deep purification, rare earth Y doping, strong magnetic field orientation, and spark plasma sintering can achieve high purity, fine grain structure, and strong magnetic field orientation of the target material. <111> The coordinated control of texture is achieved by obtaining ultra-high purity raw materials through independent deep purification of each element, realizing grain boundary pinning and texture induction through rare earth Y doping, and obtaining strong texture through full-process control of pulsed magnetic field orientation and DC magnetic field maintenance. <111> Preferred orientation is achieved by rapidly densifying the orientation structure in situ through spark plasma sintering, thereby improving the sputtering uniformity of the target material and the TMR value of the device.

[0077] Combining Example 1 and Comparative Example 2 with Table 1, it can be seen that doping with rare earth Y can achieve fine grain strengthening texture. Y can segregate at grain boundaries to form a pinning layer, inhibiting grain growth and promoting grain growth. <111> Oriented growth, but without Y doping, the grains are coarse and the texture strength is significantly reduced, resulting in poor uniformity of sputtered films and a decrease in the improvement rate of device TMR value.

[0078] As can be seen from Example 1 and Comparative Examples 3 to 5 and Table 1, the doping amount of rare earth Y needs to be controlled. When the doping amount is too low, the pinning effect is insufficient to fully inhibit grain growth. When the doping amount is too high, it may form segregated clusters, which will hinder the grain orientation growth. The doping amount range of this application can take into account both the pinning effect and the uniformity of the structure, ensuring that the target material obtains the best comprehensive performance.

[0079] Combining Example 1 and Comparative Examples 6 and 7 with Table 1, it can be seen that full-process control of the magnetic field orientation is essential for obtaining strong magnetic field strength. <111> The texture is guaranteed. When no magnetic field is applied for orientation, the texture strength is low and the film uniformity is poor. When a magnetic field is applied during the orientation and sintering stages but not maintained during the cooling process, the texture strength decreases significantly. However, when a pulsed magnetic field is applied during the orientation stage to make the powder particles rotate and align fully, a DC magnetic field is applied during the sintering stage to fix the orientation structure, and the magnetic field is maintained during the cooling stage to prevent orientation relaxation, the highest texture strength is finally obtained. This shows that the three links of pulsed magnetic field heating orientation, DC magnetic field heat preservation sintering, and magnetic field maintenance during the cooling process together constitute a complete orientation control system.

[0080] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A process for preparing a high-purity copper-nickel-cobalt alloy target for semiconductors, characterized in that, Includes the following steps: S1. Cu, Ni, Co and Y are purified independently to obtain high-purity Cu, high-purity Ni, high-purity Co and high-purity Y; S2. High-purity Cu, high-purity Ni, and high-purity Co are atomized and powdered to obtain spherical powder with a particle size D50 of 10~20μm. High-purity Y is crushed to a particle size ≤10μm and then mixed with the spherical powder and mechanically alloyed to obtain pre-alloyed powder. S3. Load the pre-alloyed powder into the mold, apply a pulsed magnetic field at 400~500℃ for orientation treatment, and hold for 30~60 minutes. S4. After orientation treatment, the pulsed magnetic field is switched to a DC magnetic field, and the sample is heated to 950-1050°C by spark plasma sintering at a heating rate of 80-120°C / min, held for 5-10 min, and subjected to an axial pressure of 40-60 MPa to obtain a sintered green body. After sintering, the sample is cooled at a cooling rate of 20-30°C / min, and a DC magnetic field is continued to be applied during the cooling process until the temperature drops below 300°C. S5. After cooling, the sintered blank is subjected to stress-relief annealing, then machined to the target size and bound to the back plate to obtain the target material.

2. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S1, the process of independently purifying Cu, Ni, Co, and Y specifically includes the following steps: Cu was purified by electrolytic refining and zone melting to obtain high-purity Cu. The electrolyte composition of the electrolytic refining was Cu². + 40~50g / L, H2SO4 150~180g / L, electrolysis temperature 50~60℃, current density 200~300A / m², the zone melting is carried out in a flowing high-purity hydrogen atmosphere, the zone melting speed is 2~5mm / min, and the number of zone meltings is ≥3. Ni is purified by carbonylation refining and electron beam melting to obtain high-purity Ni. The carbonylation reaction temperature in the carbonylation refining process is 50-80℃, the top temperature of the distillation column is 40-45℃, the bottom temperature is 55-60℃, and the thermal decomposition temperature is 200-250℃. The vacuum degree of the electron beam melting process is ≤1×10⁻⁶. - ³Pa, power is 15~25kW; High-purity Co was purified by extraction separation and plasma melting. The extraction separation had an extraction ratio of O / A = 1:1 to 2:1 and 8 to 10 extraction stages. The plasma melting was carried out in an Ar-H2 mixed atmosphere with an H2 volume ratio of 5 to 10% and a vacuum degree ≤1×10⁻⁶. - ²Pa, power 20~30kW; Y was purified by vacuum distillation and solid-state electro-deoxygenation to obtain high-purity Y, wherein the vacuum degree of the vacuum distillation was ≤1×10⁻⁶. - The solid electrodeoxidation is carried out in CaCl2 molten salt at a distillation temperature of 1650~1750℃, an electrolysis temperature of 850~950℃, a voltage of 2.5~3.5V, and an electrolysis time of 10~20h.

3. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S2, the mass percentages of Cu, Ni and Co in the spherical powder are 30-50%, 25-35% and 25-35% respectively, and the total doping amount of high-purity Y is 0.01-0.05 wt%.

4. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S2, the ball milling time for mechanical alloying is 8~12h, the ball milling speed is 200~250rpm, the ball-to-material ratio is 8:1~12:1, the ball milling jar is made of WC-Co or ZrO2, and the ball milling is carried out under argon protection. During the ball milling process, the machine is stopped every 1h for cooling and reverse rotation.

5. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S2, the micro-strain of the pre-alloyed powder is 0.15~0.25%.

6. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S3, the intensity of the pulsed magnetic field is 12~18T and the frequency is 1~10Hz.

7. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S4, the intensity of the DC magnetic field is 11~13T.

8. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S5, the stress-relief annealing temperature is 600~700℃, the holding time is 2~4h, and the vacuum degree is ≤1×10 - ³Pa.

9. The preparation process of a high-purity copper-nickel-cobalt alloy target for semiconductors according to claim 1, characterized in that: In step S5, the backplate bonding adopts indium soldering process, with bonding temperature of 180~200℃, pressure of 10~20 MPa, and heat and pressure holding time of 10~15min.

10. A high-purity copper-nickel-cobalt alloy target for semiconductors, characterized in that: It is prepared by the process described in any one of claims 1-9 for the preparation of a high-purity copper-nickel-cobalt alloy target for semiconductors.

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