A method for preparing a CoFeB target by hot isostatic pressing

Abstract

The application provides a method for preparing a CoFeB target material by hot isostatic pressing, and the method comprises the following steps: (1) mixing FeB powder, Co powder and Fe powder according to a formula amount to obtain mixed powder; and (2) performing hot isostatic pressing sintering on the mixed powder obtained in the step (1) to obtain a CoFeB target material. The method for preparing the CoFeB target material by hot isostatic pressing sintering after mixing powder is adopted, the dense, high-purity and high-permeability CoFeB target material is prepared, the smelting and gas atomization powder preparation process is omitted, and the cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sputtering targets, and relates to a target material preparation method, in particular to a method for preparing a CoFeB target material by hot isostatic pressing. BACKGROUND

[0002] CoFeB is a very important alloy material in spintronics, which is widely used in magnetic tunnel junctions and magnetic random access memories. It contains two of the three room-temperature ferromagnetic metals and is doped with B to destroy the crystal structure of the pure metal mixture, remove the long-range order and form an amorphous structure, so that the problem of lattice mismatch does not need to be considered in the process of combining with semiconductor materials. In addition, since its growth depends on the magnetic control sputtering method, it is free from the limitations of growth methods such as molecular beam epitaxy, making it possible for large-scale industrial production.

[0003] However, the CoFeB alloy is mainly in the form of a thin film at present, and the preparation of CoFeB targets is still less studied. CN115747730A discloses a CoFeB alloy target and a preparation method thereof. In the preparation of the CoFeB alloy target, boron nitride coating and molybdenum paper are used as the spacing layer, which can effectively reduce the C content in the CoFeB alloy target. By adjusting the conditions of pressure sintering, the grain size, density and magnetic permeability of the target can be controlled. The finally prepared CoFeB alloy target has uniform grain size, high magnetic permeability, low C and O contents, and accurate and uniform composition. However, the preparation method provided by the patent has a complex process and high cost. Therefore, the patent uses the powder mixing and hot pressing sintering method to prepare the CoFeB target.

[0004] At present, the proportioning of the CoFeB alloy target is relatively single, and the preparation method mainly comprises the following steps: first, alloy powder is prepared by melting and gas atomization, and then the alloy powder is cold-pressed and sintered by hot pressing or hot isostatic pressing. This process route is complex, the loss in the intermediate process is large, and the cost is high. Therefore, it is necessary to provide a method for preparing a CoFeB target by hot isostatic pressing, which has low cost and simple process. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for preparing a CoFeB target by hot isostatic pressing, which can prepare a CoFeB target with high density, high purity and high magnetic permeability, and eliminates the processes of melting and gas atomization powdering, thereby greatly reducing the cost.

[0006] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0007] This invention provides a method for preparing CoFeB target material using hot isostatic pressing, the method comprising the following steps:

[0008] (1) Ball mill and mix FeB powder, Co powder and Fe powder according to the formula to obtain a mixed powder;

[0009] (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering to obtain CoFeB target material.

[0010] This invention uses a method of hot isostatic pressing sintering after powder mixing to prepare dense, high-purity CoFeB target material with high magnetic permeability, eliminating the need for smelting and gas atomization powder preparation processes, thus greatly reducing costs.

[0011] Preferably, the ball milling and mixing in step (1) is carried out in a protective atmosphere.

[0012] Preferably, the ball milling speed in step (1) is 50-200 r / min.

[0013] Preferably, the ball milling mixing time in step (1) is 10-48 hours.

[0014] Preferably, the ball-to-material ratio in the ball milling mixture in step (1) is 2:(3-10).

[0015] Preferably, the hot isostatic pressing sintering in step (2) is carried out in a stainless steel sheath.

[0016] Preferably, the mixed powder is separated from the stainless steel sheath by high-temperature cotton and graphite paper.

[0017] Preferably, the temperature of the hot isostatic pressing in step (2) is 750-950℃.

[0018] Preferably, the pressure of the hot isostatic pressing in step (2) is 100-130 MPa.

[0019] Preferably, the heat preservation and pressure holding time for hot isostatic pressing in step (2) is 3-5 hours.

[0020] Preferably, the molar ratio of Co, Fe and B in the mixed powder in step (1) is (20-60):(20-50):(5-30).

[0021] Preferably, the particle size D50 of the FeB powder in step (1) is 3-24 μm, and more preferably 5-20 μm.

[0022] Preferably, the particle size D50 of the Co powder in step (1) is 3-10 μm.

[0023] Preferably, the particle size D50 of the Fe powder in step (1) is 3-10 μm.

[0024] Preferably, the FeB powder in step (1) has a purity of 3N or higher.

[0025] Preferably, the purity of the Co powder in step (1) is above 4N.

[0026] Preferably, the Fe powder in step (1) has a purity of 4N or higher.

[0027] As a preferred technical solution of the present invention, the method includes the following steps:

[0028] (1) In a protective atmosphere, FeB powder, Co powder and Fe powder are ball-milled and mixed according to the formula to obtain a mixed powder;

[0029] The ball milling speed is 50-200 r / min, the time is 10-48 h, and the ball-to-material ratio is 2:(3-10);

[0030] The mass ratio of Co, Fe, and B in the mixed powder is (20-60):(20-50):(5-30);

[0031] The FeB powder has a particle size D50 of 5-20 μm and a purity of 3N or higher.

[0032] The Co powder has a particle size D50 of 3-10 μm and a purity of 4N or higher.

[0033] The Fe powder has a particle size D50 of 3-10 μm and a purity of 4N or higher.

[0034] (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering to obtain CoFeB target material;

[0035] The hot isostatic pressing sintering is carried out in a stainless steel sheath;

[0036] The mixed powder is isolated from the stainless steel sheath by high-temperature cotton and graphite paper;

[0037] The hot isostatic pressing temperature is 750-950℃, the pressure is 100-130MPa, and the heat and pressure holding time is 3-5h.

[0038] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention uses a hot isostatic pressing (HIP) sintering method after powder mixing to prepare dense, high-purity CoFeB target materials with high magnetic permeability. This eliminates the need for smelting and gas atomization powder preparation processes, greatly reducing costs. Moreover, it can prepare CoFeB target materials with a density of 99.5%, uniform phase structure, and a magnetic permeability of 35%. Detailed Implementation

[0041] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0042] An embodiment of the present invention provides a method for preparing CoFeB target material by hot isostatic pressing, the method comprising the following steps:

[0043] (1) Ball mill and mix FeB powder, Co powder and Fe powder according to the formula to obtain a mixed powder;

[0044] (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering to obtain CoFeB target material.

[0045] This invention uses a method of hot isostatic pressing sintering after powder mixing to prepare dense, high-purity CoFeB target material with high magnetic permeability, eliminating the need for smelting and gas atomization powder preparation processes, thus greatly reducing costs.

[0046] In some embodiments, the ball milling mixture in step (1) is carried out in a protective atmosphere.

[0047] The protective atmosphere described in this invention includes nitrogen and / or an inert gas.

[0048] The inert gas includes any one or a combination of at least two of helium, neon, or argon. Typical but non-limiting combinations include helium and neon, neon and argon, helium and argon, or helium, neon, and argon.

[0049] In some embodiments, the ball milling speed in step (1) is 50-200 r / min, for example, it can be 50 r / min, 100 r / min, 150 r / min or 200 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] For example, the ball milling mixing method in step (1) of the present invention includes, but is not limited to, planetary ball milling, with the rotation speed being the revolution speed of the planetary ball mill.

[0051] In some embodiments, the ball milling mixing time in step (1) is 10-48h, for example, it can be 10h, 15h, 20h, 30h, 40h or 48h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] In some embodiments, the ball-to-material ratio of the ball milling mixture in step (1) is 2:(3-10), for example, it can be 2:3, 2:4, 2:5, 2:6, 2:8 or 2:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] In some embodiments, the hot isostatic pressing sintering in step (2) is carried out in a stainless steel cladding.

[0054] In some embodiments, the mixed powder is separated from the stainless steel sheath by high-temperature cotton and graphite paper.

[0055] In some embodiments, the temperature of hot isostatic pressing in step (2) is 750-950°C, for example, it can be 750°C, 800°C, 850°C, 900°C or 950°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] In some embodiments, the pressure of the hot isostatic pressing in step (2) is 100-130 MPa, for example, it can be 100 MPa, 105 MPa, 110 MPa, 120 MPa or 130 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] In some embodiments, the heat preservation and pressure holding time of the hot isostatic pressing in step (2) is 3-5 hours, for example, it can be 3 hours, 4 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] In some embodiments, the molar ratio of Co, Fe, and B in the mixed powder described in step (1) is (20-60):(20-50):(5-30), for example, it can be 20:50:30, 40:30:20 or 60:20:5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] In some embodiments, the particle size D50 of the FeB powder in step (1) is 3-24 μm, preferably 5-20 μm, for example, it can be 3 μm, 5 μm, 10 μm, 15 μm, 20 μm or 24 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0060] In some embodiments, the particle size D50 of the Co powder in step (1) is 3-10 μm, for example, it can be 3 μm, 5 μm, 6 μm, 8 μm or 10 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, the particle size D50 of the Fe powder in step (1) is 3-10 μm, for example, it can be 3 μm, 5 μm, 6 μm, 8 μm or 10 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] In some embodiments, the purity of the FeB powder in step (1) is above 3N, for example, it can be 99.9wt%, 99.93wt%, 99.95wt%, 99.98wt%, or 99.99wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] In some embodiments, the purity of the Co powder in step (1) is above 4N, for example, it can be 99.99wt%, 99.993wt%, 99.995wt%, 99.998wt%, or 99.999wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the purity of the Fe powder in step (1) is above 4N, for example, it can be 99.99wt%, 99.993wt%, 99.995wt%, 99.998wt%, or 99.999wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] As a preferred technical solution of the present invention, the method includes the following steps:

[0066] (1) In a protective atmosphere, FeB powder, Co powder and Fe powder are ball-milled and mixed according to the formula to obtain a mixed powder;

[0067] The ball milling speed is 50-200 r / min, the time is 10-48 h, and the ball-to-material ratio is 2:(3-10);

[0068] The molar ratio of Co, Fe, and B in the mixed powder is (20-60):(20-50):(5-30);

[0069] The FeB powder has a particle size D50 of 5-20 μm and a purity of 3N or higher.

[0070] The Co powder has a particle size D50 of 3-10 μm and a purity of 4N or higher.

[0071] The Fe powder has a particle size D50 of 3-10 μm and a purity of 4N or higher.

[0072] (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering to obtain CoFeB target material;

[0073] The hot isostatic pressing sintering is carried out in a stainless steel sheath;

[0074] The mixed powder is isolated from the stainless steel sheath by high-temperature cotton and graphite paper;

[0075] The hot isostatic pressing temperature is 750-950℃, the pressure is 100-130MPa, and the heat and pressure holding time is 3-5h.

[0076] Example 1

[0077] This embodiment provides a method for preparing CoFeB target material using hot isostatic pressing, the method comprising the following steps:

[0078] (1) In a nitrogen atmosphere, FeB powder, Co powder and Fe powder are ball-milled and mixed according to the formula to obtain a mixed powder;

[0079] The ball milling mixing speed is 100 r / min, the time is 30 h, and the ball-to-material ratio is 2:6;

[0080] The molar ratio of Co, Fe, and B in the mixed powder is 30:50:20;

[0081] The FeB powder has a particle size D50 of 10 μm and a purity of 3N; the Co powder has a particle size D50 of 6 μm and a purity of 4N; the Fe powder has a particle size D50 of 6 μm and a purity of 4N.

[0082] (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering and machining to obtain CoFeB target material;

[0083] The hot isostatic pressing sintering is carried out in a stainless steel sheath;

[0084] The mixed powder is isolated from the stainless steel sheath by high-temperature cotton and graphite paper;

[0085] The hot isostatic pressing temperature is 850℃, the pressure is 115MPa, and the holding time is 4h.

[0086] Example 2

[0087] This embodiment provides a method for preparing CoFeB target material using hot isostatic pressing, the method comprising the following steps:

[0088] (1) In a nitrogen atmosphere, FeB powder, Co powder and Fe powder are ball-milled and mixed according to the formula to obtain a mixed powder;

[0089] The ball milling mixing speed was 50 r / min, the time was 48 h, and the ball-to-material ratio was 2:3;

[0090] The molar ratio of Co, Fe, and B in the mixed powder is 30:50:20;

[0091] The FeB powder has a particle size D50 of 5 μm and a purity of 3N; the Co powder has a particle size D50 of 3 μm and a purity of 4N; the Fe powder has a particle size D50 of 3 μm and a purity of 4N.

[0092] (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering and machining to obtain CoFeB target material;

[0093] The hot isostatic pressing sintering is carried out in a stainless steel sheath;

[0094] The mixed powder is isolated from the stainless steel sheath by high-temperature cotton and graphite paper;

[0095] The hot isostatic pressing temperature is 750℃, the pressure is 100MPa, and the holding time is 5h.

[0096] Example 3

[0097] This embodiment provides a method for preparing CoFeB target material using hot isostatic pressing, the method comprising the following steps:

[0098] (1) In a nitrogen atmosphere, FeB powder, Co powder and Fe powder are ball-milled and mixed according to the formula to obtain a mixed powder;

[0099] The ball milling speed was 200 r / min, the time was 10 h, and the ball-to-material ratio was 2:10.

[0100] The molar ratio of Co, Fe, and B in the mixed powder is 30:50:20;

[0101] The FeB powder has a particle size D50 of 20 μm and a purity of 3N; the Co powder has a particle size D50 of 10 μm and a purity of 4N; the Fe powder has a particle size D50 of 10 μm and a purity of 4N.

[0102] (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering and machining to obtain CoFeB target material;

[0103] The hot isostatic pressing sintering is carried out in a stainless steel sheath;

[0104] The mixed powder is isolated from the stainless steel sheath by high-temperature cotton and graphite paper;

[0105] The hot isostatic pressing temperature is 950℃, the pressure is 130MPa, and the holding time is 3h.

[0106] Example 4

[0107] This embodiment provides a method for preparing CoFeB target material by hot isostatic pressing. Except that the molar ratio of Co, Fe and B in the mixed powder is 60:20:20, everything else is the same as in Example 1.

[0108] Example 5

[0109] This embodiment provides a method for preparing CoFeB target material using hot isostatic pressing. Except for the particle size D50 of FeB powder being 3 μm, the rest is the same as in Example 1.

[0110] Example 6

[0111] This embodiment provides a method for preparing CoFeB target material using hot isostatic pressing. Except for the particle size D50 of FeB powder being 24 μm, the rest is the same as in Example 1.

[0112] Example 7

[0113] This embodiment provides a method for preparing CoFeB target material by hot isostatic pressing. Except that the hot isostatic pressing temperature is 700℃, the rest is the same as in Example 1.

[0114] Performance Characterization

[0115] The density and permeability of the CoFeB targets obtained in Examples 1-13 were measured. The density was measured by Archimedes' water displacement method. The permeability was measured using a dedicated permeability testing device. The results are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] In summary, this invention uses a method of hot isostatic pressing after powder mixing to prepare dense, high-purity CoFeB target materials with high magnetic permeability, eliminating the need for smelting and gas atomization powder preparation processes, thus greatly reducing costs; moreover, it can prepare CoFeB target materials with a density of 99.5%, uniform phase structure, and a magnetic permeability of 35%.

[0120] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing CoFeB target material by hot isostatic pressing, characterized in that, The method includes the following steps: (1) In a protective atmosphere, FeB powder, Co powder and Fe powder are ball-milled and mixed according to the formula to obtain a mixed powder; (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering to obtain CoFeB target material; The molar ratio of Co, Fe, and B in the mixed powder in step (1) is 30:50:20; The particle size D50 of the FeB powder in step (1) is 10 μm; The particle size D50 of the Co powder in step (1) is 3-10 μm; The particle size D50 of the Fe powder in step (1) is 3-10 μm; The temperature of hot isostatic pressing in step (2) is 750-850℃.

2. The method according to claim 1, characterized in that, The ball milling speed in step (1) is 50-200 r / min.

3. The method according to claim 1, characterized in that, The ball milling mixing time in step (1) is 10-48 hours.

4. The method according to claim 1, characterized in that, The ball-to-material ratio in the ball milling process described in step (1) is 2:(3-10).

5. The method according to claim 1, characterized in that, The hot isostatic pressing sintering in step (2) is carried out in a stainless steel cladding.

6. The method according to claim 5, characterized in that, The mixed powder is separated from the stainless steel sheath by high-temperature cotton and graphite paper.

7. The method according to claim 1, characterized in that, The pressure of the hot isostatic pressing in step (2) is 100-130 MPa.

8. The method according to claim 1, characterized in that, The heat preservation and pressure holding time for hot isostatic pressing in step (2) is 3-5 hours.

9. The method according to claim 1, characterized in that, The FeB powder mentioned in step (1) has a purity of 3N or higher.

10. The method according to claim 1, characterized in that, The purity of the Co powder mentioned in step (1) is above 4N.

11. The method according to claim 1, characterized in that, The Fe powder mentioned in step (1) has a purity of 4N or higher.

12. The method according to claim 1, characterized in that, The method includes the following steps: (1) In a protective atmosphere, FeB powder, Co powder and Fe powder are ball-milled and mixed according to the formula to obtain a mixed powder; The ball milling speed is 50-200 r / min, the time is 10-48 h, and the ball-to-material ratio is 2:(3-10); The molar ratio of Co, Fe, and B in the mixed powder is 30:50:20; The FeB powder has a particle size D50 of 10 μm and a purity of 3N or higher. The Co powder has a particle size D50 of 3-10 μm and a purity of 4N or higher. The Fe powder has a particle size D50 of 3-10 μm and a purity of 4N or higher. (2) The mixed powder obtained in step (1) is subjected to hot isostatic pressing sintering to obtain CoFeB target material; The hot isostatic pressing sintering is carried out in a stainless steel sheath; The mixed powder is isolated from the stainless steel sheath by high-temperature cotton and graphite paper; The hot isostatic pressing temperature is 750-850℃, the pressure is 100-130MPa, and the heat and pressure holding time is 3-5h.

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