A method for preparing a cobalt-iron-boron target material for magnetic spin storage

Abstract

The application discloses a preparation method of a cobalt-iron-boron target material for magnetic spin storage, which comprises the following steps: weighing intermediate alloy powder, high-energy ball milling and activation, cobalt plating treatment, vacuum preheating and pressing, hot isostatic pressing, hot pressing and sintering, back plate welding and the like. The method can well prepare the high-density cobalt-iron-boron target material for magnetic spin storage, the cobalt-iron-boron target material is formed at a lower temperature and the magnetic permeability (PTF) of the cobalt-iron-boron target material is improved; and the powder exhaust process added in the vacuum preheating and pressing process can effectively prevent the generation of internal cracks, and the overall vacuum hot pressing temperature is effectively reduced, and the economic cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor target technology, and specifically to a method for preparing a cobalt-iron-boron target for magnetic gyratory storage. Background Technology

[0002] Rotary magnetron sputtering memory (NMR) is a new type of high-end memory characterized by nanosecond-level read / write speeds, extremely high rewrite cycles, data retention even when power is lost, excellent resistance to radiation and harsh environments, and low power consumption. This represents a new technological high ground, and the development and industrialization of high-end memory chips, represented by NMR, is a major driving force for new scientific and technological innovation. NMR technology has broad market and development prospects in fields such as the Internet of Things (IoT), medical and health, industrial control and automotive electronics, memory and servers, core routers, and mobile terminals. The fabrication process of cobalt-iron-boron (CFeB) sputtering targets for NMR is also crucial. However, existing CFeB sputtering targets are brittle, and conventional cold and hot pressing processes easily result in non-density, even internal pores and voids, leading to brittleness during later processing. Furthermore, the melting point of boron (B) differs significantly from that of iron (Fe) and cobalt (Co). Directly melting Co, Fe, and B easily causes uneven compositional segregation, severely affecting the performance of the sputtering target. Therefore, there is an urgent need for a high-density, high-PTF (permeable magnetic flux density) CFeB sputtering target to meet the standards for NMR applications. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing cobalt-iron-boron (CFeB) targets for magnetic gyratory storage, which can effectively prepare highly dense CFeB targets suitable for magnetic gyratory storage, and can be formed at a lower temperature, thereby improving the permeability (PTF) of the CFeB targets. Furthermore, the powder degassing process added during vacuum preheating and pressing can effectively prevent the generation of internal cracks, and the overall vacuum hot pressing temperature is effectively reduced, thus reducing economic costs.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A method for preparing a cobalt-iron-boron target for magnetic gyratory storage is designed, comprising the following steps:

[0006] (1) Weigh Fe-B alloy powder with a purity of 4N, activate it with a high-energy ball mill, and then wash and dry it with anhydrous ethanol to obtain active powder A;

[0007] (2) Disperse active powder A in a constant temperature water bath containing plating solution for cobalt plating treatment, and then clean and dry it with anhydrous ethanol to obtain cobalt-coated alloy powder B.

[0008] (3) Cobalt-coated alloy powder B is loaded into a molybdenum crucible and vacuum preheated and pressed to obtain a target blank; the vacuum preheating and pressing process includes the powder degassing process.

[0009] (4) The target blank is further hot-pressed and densified by atmospheric protection using a hot isostatic press to obtain a dense target material.

[0010] (5) The dense target material is processed into a disc and welded to the back plate to form an integral cobalt iron boron target material.

[0011] Preferably, the Fe-B master alloy powder in step (1) is one or more of Fe10B, Fe15B, Fe20B, and Fe25B.

[0012] Preferably, the particle size D50 of the Fe-B master alloy powder in step (1) is 0.2 to 0.6 μm.

[0013] Preferably, the plating solution formulation in step (2) is 0.2-0.5 mol / L cobalt sulfate, 0.3-0.6 mol / L sodium hypophosphite, and 0.6-1.5 mol / L sodium citrate; the pH value is adjusted to 8.2-9.2 with ammonia water, and the temperature during the cobalt plating process is 70-90℃.

[0014] Preferably, the cobalt plating time in step (2) is 2 to 6 hours, and the water bath is always in a state of mechanical stirring or ultrasonic vibration during the cobalt plating period.

[0015] Preferably, the powder exhaust process in the vacuum preheating and pressing process of step (3) specifically includes the following steps: initially, slowly heating and pressurizing, specifically heating at a rate of 1-5℃ / min and a pressurization rate of 0.05-0.2MPa / min to 300-450℃, maintaining 10MPa for 10-30min, then depressurizing to zero and pausing for 30-80s; then increasing the pressurization rate to 0.1-0.3MPa / min to 20MPa, maintaining for 10-30min, then depressurizing to zero and pausing for 30-80s; continuing to heat at a rate of 5-8℃ / min to 750-900℃, while simultaneously pressurizing at a rate of 0.1-0.3MPa / min to 30-35MPa, and holding at that temperature for 50-90min.

[0016] Preferably, the hot isostatic pressing densification sintering process in step (4) specifically involves sintering under atmosphere protection for 90 to 150 minutes at a temperature of 1000 to 1250°C and a pressure of 140 to 180 MPa.

[0017] Preferably, the protective atmosphere in step (4) is argon.

[0018] Preferably, the elemental composition of the prepared target material is as follows by mass percentage: 45-50% cobalt, 37-50% iron, and 5-13% boron.

[0019] The beneficial effects of this invention are as follows:

[0020] The method for preparing cobalt-iron-boron (CFeB) targets for gyromagnetic storage of the present invention can effectively produce high-density CFeB targets suitable for gyromagnetic storage, and can be formed at a lower temperature, thereby improving the permeability (PTF) of the CFeB targets. Furthermore, the powder degassing process added during vacuum preheating effectively prevents the formation of internal cracks, and the overall vacuum hot pressing temperature is effectively reduced, thus lowering economic costs. Specifically, it includes the following advantages:

[0021] 1. This invention uses intermediate alloy powder as raw material, which avoids the problem of boron segregation. At the same time, after high-energy ball milling, a large amount of alloy powder with high interfacial energy is obtained, which improves the powder activity and provides favorable conditions for obtaining a dense cobalt coating and improving the density of the target material.

[0022] 2. The present invention employs a cobalt-coated iron boron powder processing technology, which can obtain powder with uniform composition at the microscale, creating favorable conditions for preparing cobalt iron boron targets with uniform structure.

[0023] 3. The addition of a powder degassing process during the vacuum preheating pressing process of the present invention can effectively remove the internal gas of the mixed powder, while reducing the stress concentration effect of powder pressing and effectively preventing crack formation; the hot isostatic pressing can further densify the target material, improving the high density of the cobalt iron boron target material for magnetic gyratory storage. Detailed Implementation

[0024] The following examples illustrate specific embodiments of the present invention. However, these examples are merely for illustrative purposes and do not limit the scope of the invention in any way. Unless otherwise specified, the equipment components involved in the following examples are conventional equipment components; and unless otherwise specified, the industrial raw materials involved are commercially available conventional industrial raw materials.

[0025] Example 1: A method for preparing a cobalt-iron-boron target for magnetic gyratory storage, comprising the following steps: weighing Fe-B alloy powder with a purity of 4N and a particle size of D50 = 0.2-0.6 μm, activating it with a high-energy ball mill, and then washing and drying it with anhydrous ethanol to obtain an active powder with high distortion energy and interfacial energy; the elemental composition of the target material by mass percentage is: cobalt 45%, iron 50%, and boron 5%; the Fe-B intermediate alloy powder can be one or more of Fe10B, Fe15B, Fe20B, and Fe25B, but is not limited to these, as long as it meets the final target material composition.

[0026] The active powder is mechanically stirred or ultrasonically dispersed in a constant-temperature water bath containing a plating solution for cobalt plating. The plating solution formula is 0.2-0.5 mol / L cobalt sulfate, 0.3-0.6 mol / L sodium hypophosphite, and 0.6-1.5 mol / L sodium citrate. The pH value is adjusted to 8.2-9.2 with ammonia water. The temperature during the cobalt plating process is 70-90℃. After a designed plating time of 2-6 hours, a dense cobalt layer of 0.06-0.3 μm can be uniformly deposited on the FeB alloy powder. After cleaning and drying with anhydrous ethanol, the cobalt-coated alloy powder is obtained.

[0027] Cobalt-coated alloy powder is loaded into a molybdenum crucible and vacuum preheated and pressed to obtain a target blank. To facilitate the removal of gas from the powder, an exhaust process is added during the vacuum preheating and pressing process: the initial heating and pressurization are slow, specifically, the temperature is increased to 300-450℃ at a heating rate of 1-5℃ / min and the pressurization rate is increased to 0.05-0.2MPa / min, and at 10MPa, it is held for 10-30min, then depressurized to zero and paused for 30-80s; then the pressure is increased to 20MPa at a pressurization rate of 0.1-0.3MPa / min, held for 10-30min, then depressurized to zero and paused for 30-80s; the temperature is further increased to 750-900℃ at a heating rate of 5-8℃ / min, and the pressure is increased to 30-35MPa at a pressurization rate of 0.1-0.3MPa / min, held for 50-90min, and then cooled with the furnace.

[0028] The densification process involves hot isostatic pressing at a relatively low temperature of 1000–1250℃, with an argon pressure of 140–180 MPa and a time of 90–150 min. After furnace cooling, the material is processed into round discs and welded to a back plate to form an integral cobalt-iron-boron target.

[0029] Comparative Example 1: Cobalt iron boron targets with the same composition as those in Example 1 were prepared by powder mixing and then subjected to hot isostatic pressing at 1350°C and 140 MPa under argon protection for 90 min.

[0030] The density of the cobalt-iron-boron target material obtained in Example 1 and Comparative Example 1 was obtained by comparing the actual density with the theoretical density using the water displacement method. The magnetic permeability (PTF) was also measured using a magnetic flux meter. The specific results are shown in Table 1. The test results show that the density and magnetic permeability of Example 1 after high-energy ball milling of intermediate alloy powder, cobalt plating, vacuum preheating and degassing, and hot isostatic pressing are higher than those of Comparative Example 1. This indicates that the steps of this invention can effectively improve the density and magnetic permeability of the cobalt-iron-boron target material.

[0031] Table 1 Comparison of target material detection results between Example 1 and Comparative Example 1

[0032] Density % PTF% Example 1 99.55 37.6 Comparison Example 1 98.21 26.81

[0033] Due to the high brittleness of cobalt-iron-boron targets, conventional forming processes such as cold pressing and hot pressing in existing technologies easily result in non-density, even internal pores and voids, leading to brittle fracture during later processing. Furthermore, the melting point of boron (B) differs significantly from that of fe and cobalt (Fe and Co). Directly melting Co, Fe, and B easily causes uneven compositional segregation, severely affecting the target's performance. To address these issues, this invention uses intermediate alloy powder as raw material, which undergoes high-energy ball milling and cobalt plating. This improves the uniformity of the target's chemical composition, significantly reduces the vacuum hot pressing temperature, and effectively lowers economic costs. The addition of a powder venting process during vacuum preheating pressing effectively removes internal gases from the mixed powder, reducing stress concentration and preventing internal cracks. Hot isostatic pressing further densifies the target, enhancing its high density for cobalt-iron-boron targets suitable for magnetic gyromagnetic storage.

[0034] In summary, the method for preparing cobalt-iron-boron targets for gyromagnetic storage of the present invention can effectively produce highly dense cobalt-iron-boron targets suitable for gyromagnetic storage, and can be formed at a lower temperature, thereby improving the permeability (PTF) of the cobalt-iron-boron targets. Furthermore, the powder degassing process added during vacuum preheating and pressing can effectively prevent the generation of internal cracks, and the overall vacuum hot pressing temperature is effectively reduced, thus reducing economic costs.

[0035] The present invention has been described in detail above with reference to the embodiments. However, those skilled in the art will understand that, without departing from the spirit of the present invention, various specific parameters in the above embodiments can be changed to form multiple specific embodiments, all of which are common variations of the present invention, and will not be described in detail here.

Claims

1. A method for preparing a cobalt-iron-boron target for magnetic gyratory storage, characterized in that, Includes the following steps: (1) Weigh Fe-B alloy powder with a purity of 4N, activate it with a high-energy ball mill, and then wash and dry it with anhydrous ethanol to obtain active powder A; (2) Disperse active powder A in a constant temperature water bath containing plating solution for cobalt plating treatment, and then clean and dry it with anhydrous ethanol to obtain cobalt-coated alloy powder B. (3) Cobalt-coated alloy powder B is loaded into a molybdenum crucible and vacuum preheated and pressed to obtain a target blank; the vacuum preheating and pressing process includes a powder exhaust process; wherein, the powder exhaust process in the vacuum preheating and pressing process specifically includes the following steps: initially, the temperature and pressure are slowly increased, specifically, the temperature is increased to 300-450℃ at a heating rate of 1-5℃ / min and the pressure is increased at a pressure rate of 0.05-0.2MPa / min, and when the pressure is 10MPa, it is held for 10-30min, then the pressure is released to zero and paused for 30-80s; then the pressure is increased to 20MPa at a pressure rate of 0.1-0.3MPa / min, held for 10-30min, then the pressure is released to zero and paused for 30-80s; the temperature is increased to 750-900℃ at a heating rate of 5-8℃ / min, and the pressure is increased to 30-35MPa at a pressure rate of 0.1-0.3MPa / min, and the temperature is held for 50-90min; (4) The target blank is further hot-pressed and densified by atmospheric protection through a hot isostatic press to obtain a dense target material; (5) The dense target material is processed into a disc and welded to the back plate to form an integral cobalt iron boron target material.

2. The method for preparing the cobalt-iron-boron target for magnetic gyratory storage according to claim 1, characterized in that, The Fe-B intermediate alloy powder in step (1) is one or more of Fe10B, Fe15B, Fe20B, and Fe25B.

3. The method for preparing the cobalt-iron-boron target for magnetic gyratory storage according to claim 1, characterized in that, The particle size D50 of the Fe-B intermediate alloy powder in step (1) is 0.2-0.6 μm.

4. The method for preparing the cobalt-iron-boron target for magnetic gyratory storage according to claim 1, characterized in that, The plating solution formulation in step (2) is 0.2-0.5 mol / L cobalt sulfate, 0.3-0.6 mol / L sodium hypophosphite, and 0.6-1.5 mol / L sodium citrate; the pH value is adjusted to 8.2-9.2 with ammonia water, and the temperature during the cobalt plating process is 70-90℃.

5. The method for preparing the cobalt-iron-boron target for magnetic gyratory storage according to claim 1, characterized in that, The cobalt plating time in step (2) is 2 to 6 hours, and the water bath is always in a state of mechanical stirring or ultrasonic vibration during the cobalt plating period.

6. The method for preparing the cobalt-iron-boron target for magnetic gyratory storage according to claim 1, characterized in that, The hot isostatic pressing densification sintering process in step (4) specifically involves sintering under atmosphere protection for 90 to 150 minutes at a temperature of 1000 to 1250°C and a pressure of 140 to 180 MPa.

7. The method for preparing a cobalt-iron-boron target for magnetic gyratory storage according to claim 6, characterized in that, The protective atmosphere in step (4) is argon.

8. The method for preparing the cobalt-iron-boron target for magnetic gyratory storage according to claim 1, characterized in that, The elemental composition of the prepared target material, by mass percentage, is as follows: cobalt 45-50%, iron 37-50%, and boron 5-13%.