A NiFe sputtering target, its preparation method and application

Abstract

This invention belongs to the field of sputtering target technology, and specifically relates to a NiFe sputtering target, its preparation method, and its application. The NiFe sputtering target of this invention comprises a main component and microalloying elements; the main component includes Ni and Fe; and based on the total number of atoms in the main component, the atomic percentages of Ni and Fe are Ni 79.5-80.5 at% and Fe 19.5-20.5 at%, respectively; the microalloying elements include Y and Zr. This invention utilizes the strong oxygen affinity of Y to achieve deep deoxidation, with an oxygen content ≤30ppm. By adding Zr, precise control of Ni-Fe atomic diffusion is achieved, suppressing non-uniform long-range diffusion of Ni and Fe atoms, improving dendrite segregation, and achieving highly uniform Ni / Fe composition. Simultaneously, combined with a reasonable preparation process, the sputtering target exhibits uniform composition, refined and anisotropic grains, excellent defect and particle control, low oxygen content, and significantly improved soft magnetic properties.

Description

Technical Field

[0001] This invention belongs to the field of sputtering target technology, and specifically relates to a NiFe sputtering target, its preparation method, and its application. Background Technology

[0002] NiFe (typical component is Ni) 80 Fe 20 Permalloy is a core material for preparing soft magnetic thin films and is widely used in high-end electronic devices such as magnetoresistive memory (MRAM), magnetic read heads, semiconductor metallization, and high-frequency inductors. As electronic devices develop towards higher density, higher frequency, and smaller size, stringent requirements are placed on NiFe sputtering targets, such as: 1) extremely high compositional uniformity, with Ni / Fe fluctuations controlled within ±0.3%; 2) fine and uniform grains to avoid sputtering rate inhomogeneities and magnetic anisotropy caused by columnar crystals; 3) extremely low oxygen content (≤30ppm) to ensure the film's conductivity and soft magnetic properties; and 4) high density (≥99.5%) to reduce sputtering particle contamination.

[0003] Currently, there are many problems in the preparation of NiFe sputtering targets: 1) Severe compositional segregation: Dendritic segregation is easily generated during the melting and solidification process, resulting in Ni / Fe composition fluctuations often exceeding ±1.5%, which directly affects the consistency of the magnetic properties of the thin film; 2) Coarse and anisotropic structure: Conventional annealing easily forms columnar crystals with a size exceeding 200μm, causing uneven sputtering rate and significant anisotropy of magnetic properties, which cannot meet the requirements of high-precision devices; 3) Difficulty in controlling oxygen content: It is difficult to stably control the oxygen content in high-purity targets below 50ppm, and impurity oxygen will significantly reduce the conductivity and soft magnetic properties of the thin film; 4) Defects and particle problems: Ingot casting and deformation processes are prone to leaving pores and inclusions, generating a large amount of particle contamination during sputtering, which seriously reduces the yield of semiconductor and memory devices.

[0004] Furthermore, current research focuses on optimizing only a single step, lacking a systematic solution encompassing "deoxidation + segregation suppression + grain control." There are also significant technological gaps in the synergistic control of atomic-level segregation suppression, precise oxygen control, and grain homogenization, making it difficult to meet the requirements of semiconductor-level applications.

[0005] Therefore, it is of great significance to provide a NiFe sputtering target with uniform composition, fine grains, low oxygen content, and high density. Summary of the Invention

[0006] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial alternative. Specifically, the present invention provides a NiFe sputtering target with high compositional uniformity, Ni and Fe composition fluctuations ≤ ±0.3%, equiaxed crystals, fine grains, oxygen content ≤ 30 ppm, and high density.

[0007] The inventive concept of this invention: The NiFe sputtering target of this invention includes a main component and microalloying elements; the main component includes Ni and Fe; and based on the total number of atoms of the main component, the atomic percentages of Ni and Fe are Ni 79.5-80.5 at% and Fe 19.5-20.5 at% respectively; the microalloying elements include Y and Zr.

[0008] This invention, by limiting the proportion of Ni and Fe atoms, can effectively match the optimal soft magnetic range of permalloy. Deep deoxidation is achieved through the strong oxygen affinity of Y, stably controlling the oxygen content to ≤30ppm. Precise control of Ni-Fe atomic diffusion is achieved through Zr. The atomic radius of Zr differs significantly from that of Ni and Fe. After solidification into the NiFe matrix, Zr increases the diffusion activation energy of Ni and Fe atoms, suppressing non-uniform long-range diffusion. This suppresses dendritic segregation during solidification and heat treatment at the atomic level, achieving a highly uniform Ni / Fe composition. Furthermore, Y purifies grain boundaries and eliminates porosity; Zr suppresses dendrites and refines grains. The synergistic effect of these two factors ensures a uniform, dense, and anisotropic target structure.

[0009] Therefore, a first aspect of the present invention provides a NiFe sputtering target.

[0010] Specifically, the NiFe sputtering target comprises a main component and microalloying elements; the main component comprises Ni and Fe; and based on the total number of atoms of the main component, the atomic percentages of Ni and Fe are 79.5-80.5 at% and 19.5-20.5 at% respectively. The microalloying elements include Y and Zr.

[0011] Preferably, based on the total mass of the main components, the microalloying elements include 0.01-0.05wt% Y and 0.02-0.08wt% Zr.

[0012] Preferably, the NiFe sputtering target also contains impurities, and based on the mass of the NiFe sputtering target, the content of the impurities is: C≤10ppm, O≤30ppm, N≤5ppm, S≤2ppm, and total metal impurities≤50ppm.

[0013] Specifically, metallic impurities include at least one of Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Co, Cu, Zn, Mo, W, and Pb.

[0014] Preferably, the NiFe sputtering target has equiaxed crystals with a grain size of 50-80 μm.

[0015] A second aspect of the present invention provides a method for preparing the NiFe sputtering target described in the first aspect of the present invention.

[0016] Specifically, the preparation method of the NiFe sputtering target includes the following steps: The ingredients are mixed, then subjected to gradient melting, casting, complex large deformation, and staged annealing to obtain the product. The methods of complex large deformation include hot forging, hot rolling, and cold rolling; The graded annealing includes recrystallization annealing, homogenization annealing, and stress-relief annealing.

[0017] Preferably, the raw materials for preparing the NiFe sputtering target include Ni particles, Fe particles, Y wire, and Zr wire.

[0018] Specifically, the Ni particles, Fe particles, Y wires, and Zr wires are of the 5N grade. The mass ratio of Ni and Fe is calculated based on the atomic ratio of Ni and Fe, and the amount of Y wires and Zr wires is calculated based on the ratio of microalloying elements Y and Zr. Thus, the amount of each raw material used in the preparation of the NiFe sputtering target is obtained, and then the materials are prepared for sputtering target preparation.

[0019] Preferably, each raw material is first subjected to vacuum annealing, pickling, ultrasonic cleaning, and vacuum drying pretreatment in sequence to obtain clean, low-oxygen, and oxide-free high-purity raw materials, and then subjected to gradient melting.

[0020] Preferably, the vacuum degree of the vacuum annealing is 1×10⁻⁶. -5 -1×10 -4 Pa.

[0021] Preferably, the vacuum annealing temperature is 200-400℃.

[0022] Preferably, the vacuum annealing time is 1-3 hours.

[0023] Preferably, the pickling is performed using a dilute hydrochloric acid solution.

[0024] Preferably, the volume fraction of the dilute hydrochloric acid solution is 5-15 vol%.

[0025] Preferably, the pickling temperature is room temperature, and the pickling time is 30-120 seconds.

[0026] Preferably, the ultrasonic cleaning is performed by sequentially using anhydrous ethanol and water.

[0027] Preferably, anhydrous ethanol and water are used for ultrasonic cleaning 1-2 times, each time for 3-8 minutes.

[0028] Preferably, the vacuum drying temperature is 60-90℃.

[0029] Preferably, the vacuum degree of the vacuum drying process is ≤100Pa.

[0030] Preferably, the vacuum drying time is 2-4 hours.

[0031] Preferably, when feeding materials, the main component is added first, and after it is completely melted and the slag is removed, Y and Zr are added.

[0032] Specifically, the main components, with their high melting point and low volatility, can be added first; trace active elements such as Y and Zr, which are easily burned and oxidized, should be added later to improve recovery rates. This invention employs a segmented feeding and sequential addition method to ensure uniform composition, avoid burn-off, and control oxygen content.

[0033] Preferably, the gradient melting includes holding at 1150-1250℃ for 0.5-1.5 hours; then holding at 1400-1500℃ for 1.5-2.5 hours; and finally holding at 1520-1580℃ for 0.5-1.5 hours. More preferably, the gradient melting includes holding at 1200℃ for 1 hour; then holding at 1450℃ for 2 hours; and finally holding at 1550℃ for 1 hour.

[0034] Preferably, during the gradient melting process, the temperature is first increased to 1150-1250℃ at a heating rate of 8-12℃ / min; then increased to 1400-1500℃ at a heating rate of 5-8℃ / min; and finally increased to 1520-1580℃ at a heating rate of 3-5℃ / min.

[0035] Preferably, the gradient melting is gradient vacuum induction melting.

[0036] Preferably, stirring is performed during the gradient melting process to homogenize the composition.

[0037] Preferably, the stirring includes electromagnetic stirring.

[0038] Preferably, the frequency of the electromagnetic stirring is 20-30Hz, and the current of the electromagnetic stirring is 70-90A.

[0039] Preferably, the preparation method further includes refining after the gradient melting is completed.

[0040] Preferably, the refining temperature is 1520-1580℃, and the refining holding time is 20-40 minutes.

[0041] Preferably, stirring is performed during the refining process to achieve deep deoxidation, impurity removal, and final homogenization of components.

[0042] Preferably, the stirring includes electromagnetic stirring.

[0043] Preferably, the frequency of electromagnetic stirring for refining is 10-20Hz and the current is 50-70A.

[0044] Preferably, the cooling rate during casting is ≥50℃ / s; by controlling the cooling rate, a fine-grained, low-segregation ingot is obtained.

[0045] Preferably, the casting involves pouring the molten metal into a preheated copper mold.

[0046] Preferably, the hot forging temperature is 950-1050℃; for example, 950℃, 1000℃, 1050℃, etc.

[0047] Preferably, the total deformation of the hot forging is ≥70%; more preferably, the total deformation of the hot forging is 70-90%.

[0048] Preferably, the hot rolling temperature is 800-900℃; for example, 800℃, 850℃, 900℃, etc.

[0049] Preferably, the total deformation of the hot rolling is ≥60%; more preferably, the total deformation of the hot rolling is 60-85%.

[0050] Preferably, the total deformation of the cold rolling is ≥80%; more preferably, the total deformation of the cold rolling is 80-90%.

[0051] Specifically, the present invention utilizes a composite large deformation process combining hot forging, hot rolling, and cold rolling to break up the as-cast structure, close pores, refine grains, and increase density, which can be increased to ≥99.5%.

[0052] Preferably, the recrystallization annealing temperature is 600-700℃ and the time is 1.5-2.5h; for example, the temperature is 600℃, 650℃, 700℃, etc., and the time is 1.5h, 2h, 2.5h, etc.

[0053] Preferably, the recrystallization annealing is completed and the furnace is cooled to room temperature.

[0054] Specifically, recrystallization is completed and fine crystal nuclei are formed through recrystallization annealing in a vacuum atmosphere.

[0055] Preferably, the homogenization annealing temperature is 720-760℃ and the time is 3.5-5h; for example, the temperature is 720℃, 730℃, 740℃, 750℃, 760℃ and the time is 3.5h, 4h, 4.5h, 5h, etc.

[0056] Preferably, the homogenization annealing is completed and the furnace is cooled to room temperature.

[0057] Specifically, under a protective atmosphere, homogenization annealing is used to eliminate compositional segregation and allow the grains to grow uniformly to 50-80 μm.

[0058] Preferably, the protective atmosphere includes Ar.

[0059] Preferably, the stress-relief annealing temperature is 500-600℃ and the time is 2.5-3.5h; for example, the temperature is 500℃, 550℃, 600℃, etc., and the time is 2.5h, 3h, 3.5h, etc.

[0060] Preferably, the cooling method for the stress-relief annealing is vacuum cooling.

[0061] Specifically, graded annealing eliminates compositional segregation, stabilizes grain size to 50-80μm equiaxed grains, and eliminates internal stress.

[0062] Preferably, the preparation method further includes machining, chemical polishing, cleaning, and vacuum drying after the graded annealing; this can obtain a clean target surface with a low-deterioration layer, significantly reducing the risk of sputtering particles.

[0063] Preferably, the flatness of the machined part is ≤0.02mm and the roughness (Ra) is ≤0.4μm.

[0064] Preferably, the reagents used in the chemical polishing include HNO3, HF, and CH3COOH.

[0065] Preferably, the volume ratio of HNO3, HF and CH3COOH is 1:(0.4-0.6):(2.5-3.5).

[0066] Preferably, the chemical polishing is performed at room temperature for 30-120 seconds.

[0067] Preferably, the cleaning is ultrasonic cleaning.

[0068] Preferably, the ultrasonic cleaning involves cleaning with deionized water 1-2 times, each time for 3-8 minutes.

[0069] Preferably, after the graded annealing, the vacuum drying process involves a vacuum degree ≤100Pa, a temperature of 60-90℃, and a time of 2-4 hours.

[0070] A third aspect of the present invention provides an application of the NiFe sputtering target described in the first aspect of the present invention in electronic devices.

[0071] Preferably, the application of the NiFe sputtering target in electronic devices includes applications in MRAM, magnetic heads, semiconductor metallization, high-frequency inductors, or magnetic sensors.

[0072] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: (1) Extremely uniform composition: By adding Zr, the diffusion activation energy of Ni and Fe atoms can be increased, and the non-uniform long-range diffusion of Ni and Fe atoms can be suppressed. This suppresses dendrite segregation during solidification and heat treatment at the atomic level, achieving a high degree of uniformity in Ni / Fe composition. At the same time, combined with gradient heating melting and staged annealing processes, compositional segregation is further suppressed, ultimately controlling the Ni / Fe composition fluctuation within ±0.3% (the fluctuation of both Ni and Fe compositions is controlled within this range), which is far superior to the industry level of ±1.5%, significantly improving the performance consistency of the magnetic head and MRAM memory cell.

[0073] (2) Refined grains without anisotropy: By adding Y and Zr and combining gradient heating melting and staged annealing processes, this invention can obtain equiaxed grain structure of 50-80μm, ensuring stable sputtering rate and magnetic anisotropy of less than 5%.

[0074] (3) Excellent control of defects and particles: This invention achieves a target density of ≥99.5% by purifying the microstructure through Y-Zr microalloying, reducing porosity through gradient melting and rapid casting, compacting pores through composite large deformation, and eliminating defects through graded annealing. The target is free of residual pores and inclusions, sputtering particle contamination is reduced by more than 90%, and device yield is improved by 5-14%.

[0075] (4) Low oxygen content and significantly improved soft magnetic properties: By adding Y, deep deoxygenation can be achieved, with an oxygen content of ≤30ppm, which increases the magnetic permeability of the thin film by about 15%, and greatly enhances its conductivity and stability. Detailed Implementation

[0076] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0077] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0078] Example 1: Standard semiconductor-grade NiFe sputtering target This embodiment provides a NiFe sputtering target, which includes a main component, microalloying elements, and trace amounts of impurities. The main components are Ni and Fe, with the atomic percentages of Ni and Fe being 79.5 at% and 20.5 at% respectively, based on the total number of atoms of the main components. The microalloying elements are Y and Zr, with the mass percentages of Y and Zr being 0.03 wt% and 0.05 wt% respectively, based on the total mass of the main components. Based on the total mass of the target, the impurity content is: C 6 ppm, O 25 ppm, N 3 ppm, S 1 ppm; the metallic impurities are: Al 12 ppm, Ca 8 ppm, Cr 4 ppm, Cu 3 ppm, Pb 1 ppm, and other metallic impurities were not detected.

[0079] This embodiment also provides a method for preparing the above-mentioned NiFe sputtering target, the specific steps of which are as follows: (1) Raw material pretreatment Ni particles, Fe particles, Y wire, and Zr wire with a purity ≥5N were used as raw materials. The raw material input was calculated based on the target mass ratio of Y and Zr in the final target material, combined with the melting and burn-off rate of 15% Y and 7% Zr under vacuum induction melting. Each raw material was first heated under a vacuum of 5×10⁻⁶. -5 Vacuum annealing at 300℃ for 2 hours; then pickling with 10 vol% dilute hydrochloric acid solution at room temperature for 60 seconds; followed by ultrasonic cleaning with anhydrous ethanol and deionized water once each for 5 minutes; finally, vacuum drying at 70℃ and vacuum degree ≤50Pa for 3 hours to complete the raw material pretreatment and obtain a clean, low-oxygen, oxide-free high-purity raw material. (2) Gradient vacuum induction melting The pretreated raw materials are added to the vacuum induction melting furnace in batches: first, Ni particles and Fe particles are added, and the vacuum is drawn to 5×10⁻⁶. - 5 Pa, then high-purity Ar is added to bring the pressure to 0.05 MPa; under electromagnetic stirring at 25 Hz and 80 A, the temperature is increased to 1200 ℃ at 10 ℃ / min and held for 1 h to completely melt and mix Ni and Fe; then the temperature is increased to 1450 ℃ at 6 ℃ / min and held for 2 h; at the end of the holding period at 1450 ℃, Y wire and Zr wire are added in batches, and the temperature is increased to 1550 ℃ at 4 ℃ / min and held for 1 h; finally, the temperature is refined at 1550 ℃, 15 Hz and 60 A under weak electromagnetic stirring for 30 min to complete the smelting. (3) Rapid cooling casting The molten liquid after melting in step (2) is poured into a copper mold preheated to 300°C, and the cooling rate is controlled to be ≥50°C / s to obtain a fine-grained, low-segregation ingot. (4) Composite large deformation The ingot obtained in step (3) is subjected to hot forging, hot rolling and cold rolling in sequence; wherein, the temperature of hot forging is 1000℃ and the total deformation is 75%; the temperature of hot rolling is 850℃ and the total deformation is 65%; the total deformation of cold rolling is 80%. (5) Graded annealing The material obtained after composite large deformation was subjected to recrystallization annealing, homogenization annealing and stress relief annealing in sequence. Among them, recrystallization annealing was carried out in a vacuum atmosphere at a temperature of 650℃ for 2 hours and then cooled to room temperature in the furnace after annealing; homogenization annealing was carried out in an Ar atmosphere at a temperature of 750℃ for 4 hours and then cooled to room temperature in the furnace after annealing; stress relief annealing was carried out at a temperature of 550℃ for 3 hours and then cooled in a vacuum. (6) Machining and Surface Treatment The target size was obtained by CNC turning and grinding, with flatness controlled to ≤0.02mm and Ra≤0.4μm. Then, a polishing slurry with a volume ratio of HNO3, HF and CH3COOH of 1:0.5:3 was used for chemical polishing at room temperature for 60s. Next, the target was ultrasonically cleaned twice with deionized water for 5min each time. Finally, the target was vacuum dried at 70℃ and ≤50Pa for 3h to obtain the NiFe sputtering target.

[0080] Example 2: Low-stress flexible electronic target material NiFe sputtering device This embodiment provides a NiFe sputtering target, which includes a main component, microalloying elements, and trace amounts of impurities. The main components are Ni and Fe, with Ni accounting for 79 at% and Fe accounting for 21 at% of the total atomic number of the main components. The microalloying materials are Y and Zr, with Y and Zr accounting for 0.01 wt% and 0.08 wt% of the total mass of the main components, respectively. Based on the total mass of the target, the impurity content is: C 5 ppm, O 22 ppm, N 2 ppm, S 0.8 ppm; the metallic impurities are: Al 9 ppm, Ca 6 ppm, Cr 3 ppm, Cu 2 ppm, Pb 0.5 ppm, and other metallic impurities were not detected.

[0081] The difference between the preparation method of NiFe sputtering target in Example 2 and Example 1 is that the temperature of the third stage gradient heating melting and refining is 1530℃, the cold rolling deformation is increased to 85%, the homogenization annealing temperature is 720℃, and the holding time is 5h. The rest is the same as the preparation method in Example 1.

[0082] Example 3: MRAM High-End Low Coercivity NiFe Sputtering Target This embodiment provides a NiFe sputtering target, which includes a main component, microalloying elements, and trace amounts of impurities. The main components are Ni and Fe, with the atomic percentages of Ni and Fe being 80.2 at% and 19.8 at% respectively, based on the total atomic number of the main components. The microalloying elements are Y and Zr, with the mass percentages of Y and Zr being 0.04 wt% and 0.06 wt% respectively, based on the total mass of the main components. Based on the total mass of the target, the impurity content is: C 7 ppm, O 23 ppm, N 3 ppm, S 1.2 ppm; the metallic impurities are: Al 10 ppm, Ca 7 ppm, Cr 3 ppm, Cu 2 ppm, Pb 1 ppm, and other metallic impurities were not detected.

[0083] This embodiment also provides a method for preparing the above-mentioned NiFe sputtering target, the specific steps of which are as follows: (1) Raw material pretreatment Ni particles, Fe particles, Y wire, and Zr wire with a purity ≥5N were used as raw materials. The raw material input was calculated based on the target mass ratio of Y and Zr in the final target material, combined with the melting and burn-off rate of 15% Y and 7% Zr under vacuum induction melting. Each raw material was first heated under a vacuum of 1×10⁻⁶. -5 Vacuum annealing at 300℃ for 2 hours; then pickling with 10 vol% dilute hydrochloric acid solution at room temperature for 60 seconds; followed by ultrasonic cleaning with anhydrous ethanol and deionized water once each for 5 minutes; finally, vacuum drying at 70℃ and vacuum degree ≤50Pa for 3 hours to complete the raw material pretreatment and obtain a clean, low-oxygen, oxide-free high-purity raw material. (2) Gradient vacuum induction melting The pretreated raw materials are added to the vacuum induction melting furnace in batches: first, Ni particles and Fe particles are added, and the vacuum is drawn to 5×10⁻⁶. - 5 Pa, then high-purity Ar is added to bring the pressure to 0.05 MPa; under electromagnetic stirring at 25 Hz and 80 A, the temperature is increased to 1200 ℃ at 10 ℃ / min and held for 1 h to completely melt and mix Ni and Fe; then the temperature is increased to 1450 ℃ at 6 ℃ / min and held for 2 h; at the end of the holding period at 1450 ℃, Y wire and Zr wire are added in batches, and the temperature is increased to 1550 ℃ at 4 ℃ / min and held for 1 h; finally, the temperature is refined at 1550 ℃, 15 Hz and 60 A under weak electromagnetic stirring for 30 min to complete the smelting. (3) Rapid cooling casting The molten liquid after melting in step (2) is poured into a copper mold preheated to 300°C, and the cooling rate is controlled to be ≥50°C / s to obtain a fine-grained, low-segregation ingot. (4) Composite large deformation The ingot obtained in step (3) is subjected to hot forging, hot rolling, and cold rolling in sequence; wherein, the temperature of hot forging is 1000℃ and the total deformation is 75%; the temperature of hot rolling is 850℃ and the total deformation is 65%; and the total deformation of cold rolling is 82%. (5) Graded annealing The material obtained after composite large deformation was subjected to recrystallization annealing, homogenization annealing and stress relief annealing in sequence; recrystallization annealing was carried out in a vacuum atmosphere at a temperature of 650℃ for 2 hours; homogenization annealing was carried out in an Ar atmosphere at a temperature of 750℃ for 4 hours; stress relief annealing was carried out at a temperature of 550℃ for 3 hours. (6) Machining and Surface Treatment The target size was obtained by CNC turning and grinding, with flatness controlled to ≤0.02mm and Ra≤0.4μm. Then, a polishing slurry with a volume ratio of HNO3, HF and CH3COOH of 1:0.5:3 was used for chemical polishing at room temperature for 60s. Next, the target was ultrasonically cleaned twice with deionized water for 5min each time. Finally, the target was vacuum dried at 70℃ and ≤50Pa for 3h to obtain the NiFe sputtering target.

[0084] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not include Y; otherwise, they are the same as Example 1.

[0085] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 did not include Zr; otherwise, they are the same as Example 1.

[0086] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not involve three-stage gradient heating and melting, but directly involves constant temperature melting, that is, it is directly melted at 1550℃ for 3 hours under the action of electromagnetic stirring at 25Hz and 80A. The rest is the same as Example 1.

[0087] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that Comparative Example 4 does not undergo graded annealing, but is directly annealed in one step at 750°C for 6 hours, while the rest is the same as Example 1.

[0088] Performance testing The performance of the NiFe sputtering targets prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and test methods are as follows: Compositional uniformity: ICP-OES method, tested according to GB / T 20125-2006. Multiple sampling points were used with ICP-OES to test the Ni and Fe content in different regions of the target material, obtaining multiple sets of measured atomic percentages. Compositional fluctuation = (measured value) (Theoretical standard value) / Theoretical standard value × 100%, ± represents the actual component's fluctuation range around the standard value; Grain size: Tested by metallographic cross-section method, in accordance with GB / T 6394-2017; Density: Archimedes displacement method, tested according to GB / T 3850-2015; Oxygen content: tested using pulsed heating infrared method, in accordance with GB / T 11261-2022; Magnetic properties (coercivity Hc, permeability μ): VSM / BH tester, using vibrating sample magnetometer (VSM) / BH tester, tested in accordance with GB / T 13012-2008 "Measurement method of DC magnetic properties of soft magnetic materials"; Magnetic anisotropy: Multi-directional magnetic performance comparison method, with reference to GB / T 13012-2008 "Measurement method of DC magnetic properties of soft magnetic materials", the magnetic anisotropy value is calculated by testing the permeability in the rolling direction, perpendicular to the rolling direction and 45° direction. Sputtered particle count: After the film is formed by sputtering the target material, the defects of large particles on the film surface are counted and the size distribution is statistically analyzed using an optical microscope or a surface defect scanner (SSIS) (a surface defect scanner is used in this test); Device yield: Using MRAM memory cells and high-frequency inductors as test objects, the batch performance statistical method was adopted to test the permeability, resistivity, breakdown voltage and leakage current respectively, and the percentage of qualified devices was statistically analyzed.

[0089] Thin film stress: The substrate bending method (curvature method) was used, and the test was conducted in accordance with GB / T 44517-2024 "Micro-electromechanical systems (MEMS) technology MEMS film residual stress wafer curvature and cantilever beam deflection test method".

[0090] The performance test results of the NiFe sputtering targets prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0091] Table 1: Performance test results of NiFe sputtering targets prepared in Examples 1-3 and Comparative Examples 1-4

[0092] The compositional fluctuation data in Table 1 represent the values ​​listed above for both Ni and Fe components.

[0093] As can be seen from Table 1, the present invention employs Y-Zr microalloying + gradient melting + composite large deformation + staged annealing, which results in a sputtering target material with uniform composition, equiaxed grains of 50-60μm, oxygen content ≤25ppm, density ≥99.6%, magnetic anisotropy <3.5%, fewer sputtered particles, and high device yield.

[0094] Comparative Example 1, without the addition of Y, resulted in the sputtering target failing to achieve deep deoxidation, leading to excessive oxygen content, significant deterioration of magnetic properties, coarse and uneven grains, large compositional fluctuations, and an increase in particle size. This demonstrates that Y is essential for deep deoxidation and reducing oxygen content.

[0095] In Comparative Example 2, the absence of Zr resulted in the sputtering target failing to suppress Ni-Fe dendritic segregation. The segregation was severe, with prominent columnar crystals, coarse grains, and a significant decrease in compositional uniformity, along with high magnetic anisotropy. This demonstrates that Zr plays a crucial role in suppressing segregation, refining grains, and improving uniformity.

[0096] Comparative Example 3, with its non-gradient heating melting process, resulted in severe compositional segregation of the sputtering target, coarse microstructure, the appearance of large dendrites, high film stress, and significant magnetic anisotropy. This demonstrates that gradient heating melting is crucial for achieving compositional homogenization.

[0097] Comparative Example 4 uses single-step annealing, which fails to eliminate segregation and stress in the sputtering target, resulting in severely coarse grains, high magnetic anisotropy, high internal stress in the thin film, easy film detachment, and poor sputtering rate uniformity. This demonstrates that staged annealing, combining recrystallization annealing, homogenization annealing, and stress-relief annealing, is essential for eliminating stress and obtaining equiaxed crystals.

[0098] In summary, this invention utilizes the strong oxygen affinity of γ to achieve deep deoxidation, stably controlling the oxygen content to ≤30ppm. By adding Zr, precise control of Ni-Fe atomic diffusion is achieved, suppressing the non-uniform long-range diffusion of Ni and Fe atoms. This suppresses dendritic segregation during solidification and heat treatment at the atomic level, resulting in highly uniform Ni / Fe composition. Furthermore, combined with a reasonable preparation process, especially gradient heating melting and staged annealing, the sputtering target exhibits uniform composition, refined and anisotropic grains, excellent defect and particle control, low oxygen content, and significantly improved soft magnetic properties.

[0099] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A NiFe sputtering target, characterized in that, The NiFe sputtering target includes a main component and microalloying elements; The main components include Ni and Fe; and based on the total number of atoms of the main components, the atomic percentages of Ni and Fe are 79.5-80.5 at% and 19.5-20.5 at% respectively. The microalloying elements include Y and Zr.

2. The NiFe sputtering target according to claim 1, characterized in that, The microalloying elements, based on the total mass of the main components, include 0.01-0.05 wt% Y and 0.02-0.08 wt% Zr.

3. The NiFe sputtering target according to claim 1, characterized in that, The NiFe sputtering target also contains impurities, and based on the mass of the NiFe sputtering target, the content of the impurities is: C≤10ppm, O≤30ppm, N≤5ppm, S≤2ppm, and total metal impurities≤50ppm.

4. The NiFe sputtering target according to claim 1, characterized in that, The NiFe sputtering target has equiaxed crystals with a grain size of 50-80 μm.

5. The method for preparing the NiFe sputtering target according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: The ingredients are mixed, then subjected to gradient melting, casting, complex large deformation, and staged annealing to obtain the product. The methods of complex large deformation include hot forging, hot rolling, and cold rolling; The graded annealing includes recrystallization annealing, homogenization annealing, and stress-relief annealing.

6. The preparation method according to claim 5, characterized in that, The gradient melting process includes first holding at 1150-1250℃ for 0.5-1.5 hours; then holding at 1400-1500℃ for 1.5-2.5 hours; and finally holding at 1520-1580℃ for 0.5-1.5 hours. And / or, stirring is performed during the gradient melting process; And / or, the preparation method further includes refining after the gradient melting is completed; And / or, the cooling rate during casting is ≥50℃ / s.

7. The preparation method according to claim 6, characterized in that, The stirring includes electromagnetic stirring; And / or, the refining temperature is 1520-1580℃, and the refining holding time is 20-40min.

8. The preparation method according to claim 5, characterized in that, The hot forging temperature is 950-1050℃; And / or, the total deformation of the hot forging is ≥70%; And / or, the hot rolling temperature is 800-900℃; And / or, the total deformation of the hot rolling is ≥60%; And / or, the total deformation of the cold rolling is ≥80%.

9. The preparation method according to claim 5, characterized in that, The recrystallization annealing temperature is 600-700℃, and the time is 1.5-2.5h; And / or, the homogenization annealing temperature is 720-760℃, and the time is 3.5-5h; And / or, the stress-relief annealing temperature is 500-600℃, and the time is 2.5-3.5h; And / or, the preparation method further includes machining, chemical polishing, cleaning, and vacuum drying processes after the graded annealing.

10. The application of the NiFe sputtering target according to any one of claims 1-4 in electronic devices.

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