A Co-Fe-W-Nb alloy sputtering target and preparation method thereof

Abstract

The present invention discloses a Co-Fe-W-Nb alloy sputtering target and a preparation method thereof, wherein the preparation method comprises the following steps: (1) adding Fe metal, Nb metal, Co-W master alloy and Co metal into a smelting furnace, performing vacuum induction smelting, and obtaining an alloy melt; (2) casting the alloy melt in step (1) into a mold, and controlling the cooling rate of the mold to be 13-26°C / min during the casting process; after cooling and demoulding, obtaining a target blank; wherein the casting thickness is 12-25mm; (3) machining the target blank in step (2) to obtain a Co-Fe-W-Nb alloy sputtering target. The method of the present invention controls the cooling rate and the thickness of the ingot during the casting process, and can make the target obtain a more uniform and fine microstructure while ensuring that the target does not crack, thereby improving the magnetic permeability of the sputtering target; and the method can also eliminate large-sized shrinkage cavities and improve the uniformity and density of the target.

Description

Technical Field

[0001] This invention belongs to the field of alloy sputtering target technology, specifically relating to a Co-Fe-W-Nb alloy sputtering target and its preparation method. Background Technology

[0002] As the demand for information storage capacity in magnetic recording media increases, improving the recording quality of these media has been a key research topic for industry professionals. Based on the direction of magnetization of the magnetic head, existing magnetic recording media can be categorized into horizontal and vertical types. Taking vertical magnetic recording media as an example, its layered structure, from bottom to top, includes a substrate, an adhesion layer, a soft magnetic layer, a seed layer, an intermediate layer, a magnetic recording layer, a capping layer, and a lubricating layer. Existing soft magnetic layers are mostly composed of Co and Fe. To further improve the corrosion resistance of the soft magnetic layer, existing technologies incorporate Nb, Ta, and other components to enhance its quality when applied to magnetic recording media.

[0003] Co-Fe-W-Nb alloys are mainly composed of the Co-Fe phase and metallic compound phases formed by one or two elements from Co or Fe and one or two elements from W or Nb. They are characterized by high melting point, high density, high hardness, high brittleness, and difficulty in plastic processing. Currently, the preparation method for Co-Fe-W-Nb sputtering targets mainly involves pre-alloying some elements to obtain alloy powder, then mixing the alloy powder with other metal element powders, followed by hot pressing sintering and machining. However, Co-Fe-W-Nb sputtering targets prepared by this hot pressing sintering method suffer from poor uniformity, low density, high porosity, high oxygen content, complex processing, and high cost.

[0004] Vacuum melting and casting is also a method for preparing alloy targets. The alloy targets prepared by this method have lower carbon and oxygen content and higher purity. However, since Co-Fe-W-Nb alloys are composed of two phases and have a high melting point, the casting process will generate large structural and thermal stresses, making the target material prone to cracking. Moreover, this method will also lead to unavoidable large shrinkage cavities inside the target material, resulting in low material utilization and uneven metallographic structure. Summary of the Invention

[0005] The main objective of this invention is to provide a crack-free, low-cost Co-Fe-W-Nb alloy sputtering target and its preparation method.

[0006] This invention provides a method for preparing a Co-Fe-W-Nb alloy sputtering target, using the following technical solution: A method for preparing a Co-Fe-W-Nb alloy sputtering target includes the following steps: (1) Add Fe metal, Nb metal, Co-W master alloy and Co metal into a melting furnace and perform vacuum induction melting to obtain alloy melt; (2) The alloy melt in step (1) is poured into the mold. During the pouring process, the cooling rate of the mold is controlled to be 13~26℃ / min. After cooling and demolding, the target blank is obtained. The thickness of the casting is 12~25mm. (3) The target blank in step (2) is machined to obtain Co-Fe-W-Nb alloy sputtering target.

[0007] Preferably, the structural formula of the Co-Fe-W-Nb alloy is (Co 100-Y Fe Y ) 100-X (W 14~19 Nb 1~6 ) X , wherein: 20at%≤X≤28at%, 0<Y<100 at%; in step (1), Fe metal, Nb metal, Co-W master alloy, and Co metal are added according to the atomic percentages of Co, Fe, W, and Nb in the structural formula of the Co-Fe-W-Nb alloy system.

[0008] Preferably, in step (1), the temperature of vacuum induction melting is 1600~1670℃, and the time of vacuum induction melting is 40~60min.

[0009] Preferably, in step (1), the order of feeding Fe metal, Nb metal, Co-W master alloy, and Co metal into the smelting furnace is Fe metal, Nb metal, Co-W master alloy, and Co metal; that is, Fe metal is placed at the bottom layer of the smelting furnace, Nb metal and Co-W master alloy are placed on the upper layer of Fe metal, and Co metal is placed on the top layer.

[0010] Preferably, in step (1), the preparation method of the Co-W master alloy includes the following steps: Co metal and W metal are added alternately in layers to a melting furnace for magnetic levitation melting. After melting, the mixture is cooled to obtain the Co-W master alloy.

[0011] More preferably, the mass ratio of Co metal to W metal is (1~4):1.

[0012] More preferably, the magnetic levitation melting temperature is 2500~3000℃, the magnetic levitation melting time is 10~15min, and the magnetic levitation melting is performed 2~3 times.

[0013] Preferably, in step (2), the casting speed is 2~3 kg / s.

[0014] Preferably, in step (3), the machining includes wire cutting and grinding of the target blank.

[0015] Based on the same inventive concept, the present invention provides a Co-Fe-W-Nb alloy sputtering target prepared by the above preparation method.

[0016] The above-described one or more technical solutions of the present invention can achieve at least one of the following beneficial effects: The Co-Fe-W-Nb alloy sputtering target prepared by the melting and casting method in this invention has lower C and O content and higher purity compared with the target prepared by the pressure sintering method; moreover, the preparation method of this invention is simple and has lower production cost.

[0017] The method of the present invention controls the cooling rate and the thickness of the ingot during the casting process. While ensuring that the Co-Fe-W-Nb alloy sputtering target does not crack, it can make the target material obtain a more uniform and fine microstructure, thereby improving the magnetic permeability of the sputtering target. Moreover, the method can also eliminate large-sized shrinkage cavities and improve the uniformity and density of the target material. Attached Figure Description

[0018] Figure 1 The image shows the metallographic structure of the 64Co-15Fe-15W-6Nb alloy sputtering target prepared in Example 1.

[0019] Figure 2 The image shows the metallographic structure of the 64Co-15Fe-15W-6Nb alloy sputtering target prepared in Comparative Example 1.

[0020] Figure 3 The image shows the metallographic structure of the 64Co-15Fe-15W-6Nb alloy sputtering target prepared in Comparative Example 2. Detailed Implementation

[0021] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0022] A method for preparing a Co-Fe-W-Nb alloy sputtering target includes the following steps: (1) Add Fe metal, Nb metal, Co-W master alloy and Co metal into a melting furnace and perform vacuum induction melting to obtain alloy melt; (2) The alloy melt in step (1) is poured into the mold, and the cooling rate of the mold is controlled to be 13~26℃ / min. After cooling and demolding, the target blank is obtained; wherein the thickness of the casting is 12~25mm. (3) The target blank in step (2) is machined to obtain Co-Fe-W-Nb alloy sputtering target.

[0023] The Co-Fe-W-Nb alloy sputtering target prepared by the melting and casting method in this invention can have low C and O content and higher purity. Moreover, the preparation method of this invention is simple and has lower production cost.

[0024] The method of the present invention controls the cooling rate and the thickness of the ingot during the casting process. While ensuring that the Co-Fe-W-Nb alloy sputtering target does not crack, it can make the target material obtain a more uniform and fine microstructure, thereby improving the magnetic permeability of the sputtering target. Moreover, the method can also eliminate large-sized shrinkage cavities and improve the uniformity and density of the target material.

[0025] Preferably, the structural formula of the Co-Fe-W-Nb alloy is (Co 100-Y Fe Y ) 100-X (W 14~19 Nb 1~6 ) X , wherein: 20at%≤X≤28at%, 0<Y<100 at%; in step (1), Fe metal, Nb metal, Co-W master alloy, and Co metal are added according to the atomic percentages of Co, Fe, W, and Nb in the structural formula of the Co-Fe-W-Nb alloy system.

[0026] Preferably, in step (1), the temperature of vacuum induction melting is 1600~1670℃, and the time of vacuum induction melting is 40~60min.

[0027] Preferably, in step (1), the order of feeding Fe metal, Nb metal, Co-W master alloy, and Co metal into the smelting furnace is Fe metal, Nb metal, Co-W master alloy, and Co metal; that is, Fe metal is placed at the bottom layer of the smelting furnace, Nb metal and Co-W master alloy are placed on the upper layer of Fe metal, and Co metal is placed on the top layer.

[0028] The Nb and Co-W master alloys have high melting points, and W has a high density and is easy to settle. Therefore, in the method of the present invention, the Nb metal and Co-W master alloy are placed in the middle position where the induction effect is better, which can further improve the uniformity of the alloy melt.

[0029] Preferably, in step (1), the preparation method of the Co-W master alloy includes the following steps: Co metal and W metal are added alternately in layers to a melting furnace for magnetic levitation melting. After melting, the mixture is cooled to obtain the Co-W master alloy.

[0030] W metal has a high melting point, high density, and high mass ratio, making it difficult to melt. This invention first prepares a Co-W master alloy through magnetic levitation melting, which can lower the melting point of W metal, reduce the holding time of subsequent vacuum induction melting, and improve melting efficiency.

[0031] More preferably, the mass ratio of Co metal to W metal is (1~4):1.

[0032] More preferably, the magnetic levitation melting temperature is 2500~3000℃, the magnetic levitation melting time is 10~15min, and the magnetic levitation melting is performed 2~3 times.

[0033] Preferably, in step (2), the casting speed is 2~3 kg / s.

[0034] Preferably, in step (3), the machining includes wire cutting and grinding of the target blank.

[0035] Example 1 In this embodiment, the Co-Fe-W-Nb alloy sputtering target is a 64Co-15Fe-15W-6Nb alloy sputtering target, and the specific preparation method is as follows: Step 1: Co metal and W metal are added to the melting furnace at a mass ratio of 1:1 and magnetically levitated and melted twice at 2800℃, each time for 10 minutes. After melting, the mixture is cooled in a copper crucible to obtain a Co-W master alloy.

[0036] Step 2: Add the raw materials in the following order: Fe metal, Nb metal, Co-W master alloy, and Co metal. Then, perform vacuum induction melting at 1630℃ for 50 minutes to obtain the alloy melt. The Fe metal, Nb metal, Co-W master alloy, and Co metal are added in an atomic percentage ratio of 64:15:15:6 for Co, Fe, W, and Nb.

[0037] Step 3: Pour the alloy molten liquid into a water-cooled copper mold at a casting speed of 2.5 kg / s, where the casting thickness is 16 ± 2 mm, and the cooling rate is controlled at 16~21℃ / min using a water-cooled copper mold; after cooling to room temperature, demold to obtain the target blank.

[0038] Step 4: Using the relatively flat surface of the target blank as a reference, perform wire cutting on the top of the target blank; then, using the cut surface as a reference, perform a second wire cutting to obtain a target blank with flat upper and lower surfaces; after wire cutting, grind the target blank on both sides to obtain a 64Co-15Fe-15W-6Nb alloy sputtering target with a diameter of 190mm and a thickness of 10mm.

[0039] The method for testing the metallographic structure of the sputtering target in this invention is as follows: A sample is taken from the alloy sputtering target, mechanically polished, and then subjected to HCl:HNO₃... 3: H2O in a ratio of 2:2:3 was used as the metallographic etchant to etch the polished target sample, and then the metallographic structure of the target was observed using an optical microscope.

[0040] The metallographic image of the 64Co-15Fe-15W-6Nb alloy sputtering target in this embodiment is as follows: Figure 1 As shown, the average grain size of the target material is less than 10 μm, and the alloy phases rich in W and Nb and the Co-Fe alloy phase are evenly distributed in equal proportions.

[0041] Comparative Example 1 The process is basically the same as in Example 1, except that step three is different. Specifically, the alloy melt is poured into a graphite mold at a casting speed of 2.5 kg / s, with a casting thickness of 16 ± 2 mm. The cooling rate is controlled at 1~5 °C / min using a graphite mold. After cooling to room temperature, the mold is removed to obtain the target blank.

[0042] The metallographic image of the 64Co-15Fe-15W-6Nb alloy sputtering target prepared in this comparative example is shown below. Figure 2 As shown, the average grain size of the target material significantly exceeds 10 μm, and the alloy phases rich in W and Nb elements and the Co-Fe alloy phase are unevenly distributed, indicating that the compositional uniformity of the target material is poor.

[0043] Comparative Example 2 The process is basically the same as in Example 1, except that step three is different. Specifically, the alloy melt is poured into the cast steel mold at a casting speed of 2.5 kg / s, with a casting thickness of 16 ± 2 mm. The cooling rate is controlled at 4~8℃ / min using the cast steel mold. After cooling to room temperature, the mold is removed to obtain the target blank.

[0044] Metallographic image of the 64Co-15Fe-15W-6Nb alloy sputtering target prepared in this comparative example, as shown below. Figure 3As shown, the average grain size of the target material significantly exceeds 10 μm, and the alloy phases rich in W and Nb elements and the Co-Fe alloy phase are unevenly distributed, indicating that the compositional uniformity of the target material is poor.

[0045] Comparative Example 3 The process is basically the same as in Example 1, except that step three is different. Specifically, the alloy melt is poured into the water-cooled copper mold at a casting speed of 2.5 kg / s, with a casting thickness of 8 ± 2 mm. The circulating water pressure of the water-cooled copper mold is increased, the circulating water temperature is reduced, and the cooling rate is controlled at 27~32℃ / min. The molten metal has poor fluidity and the ingot has low flatness. After cooling to room temperature, the ingot is demolded to obtain the target billet. The target blank prepared in this comparative example is brittle and has poor machinability. When wire cutting and grinding are performed in step four, the target material cracks.

[0046] Comparative Example 4 It is basically the same as Example 1, except that in step three, the thickness of the casting is 28±2mm.

[0047] The 64Co-15Fe-15W-6Nb alloy sputtering target prepared in this comparative example could not withstand the internal stress after cooling to room temperature, resulting in cracks and eventually overall cracking.

[0048] Example 2 The process is basically the same as in Example 1, except that in step two, Nb metal, Co-W master alloy, Fe metal, and Co metal are mixed and then added to the smelting furnace.

[0049] Example 3 In this embodiment, the Co-Fe-W-Nb alloy sputtering target is a 65Co-16Fe-15W-4Nb alloy sputtering target, and the specific preparation method is as follows: Step 1: Co metal and W metal are added to the melting furnace at a mass ratio of 1:1 and magnetically levitated at 2500℃ for 3 times, each melting for 15 minutes. After melting, the mixture is cooled in a copper crucible to obtain a Co-W master alloy.

[0050] Step 2: Add the raw materials in the following order: Fe metal, Nb metal, Co-W master alloy, and Co metal. Then, perform vacuum induction melting at 1600℃ for 60 minutes to obtain the alloy melt. The Fe metal, Nb metal, Co-W master alloy, and Co metal are added in an atomic percentage ratio of 65:16:15:4 for Co, Fe, W, and Nb.

[0051] Step 3: The alloy molten liquid is poured into a water-cooled copper mold at a casting speed of 3.0 kg / s, with a casting thickness of 15 ± 2 mm. The cooling rate is controlled at 20~25℃ / min using a water-cooled copper mold. After cooling to room temperature, the mold is removed to obtain the target blank. Step 4: Using the relatively flat surface of the target blank as a reference, perform wire cutting on the top of the target blank; then, using the cut surface as a reference, perform a second wire cutting to obtain a target blank with flat upper and lower surfaces; after wire cutting, grind the target blank on both sides to obtain a 65Co-16Fe-15W-4Nb alloy sputtering target with a diameter of 190mm and a thickness of 13mm.

[0052] Example 4 In this embodiment, the Co-Fe-W-Nb alloy sputtering target is a 70Co-10Fe-16W-4Nb alloy sputtering target, and the specific preparation method is as follows: Step 1: Co metal and W metal are added to the melting furnace at a mass ratio of 2:1 and magnetically levitated twice at 3000℃, each melting for 12 minutes. After melting, the mixture is cooled in a copper crucible to obtain a Co-W master alloy.

[0053] Step 2: Add the raw materials in the following order: Fe metal, Nb metal, Co-W master alloy, and Co metal. Then, perform vacuum induction melting at 1670℃ for 40 minutes to obtain the alloy melt. The Fe metal, Nb metal, Co-W master alloy, and Co metal are added in an atomic percentage ratio of 70:10:16:4 for Co, Fe, W, and Nb.

[0054] Step 3: The alloy molten liquid is poured into a water-cooled copper mold at a casting speed of 2.0 kg / s, with a casting thickness of 21 ± 2 mm. The cooling rate is controlled at 14~19℃ / min using a water-cooled copper mold. After cooling to room temperature, the mold is removed to obtain the target blank. Step 4: Using the relatively flat surface of the target blank as a reference, perform wire cutting on the top of the target blank; then, using the cut surface as a reference, perform a second wire cutting to obtain a target blank with flat upper and lower surfaces; after wire cutting, grind the target blank on both sides to obtain a 70Co-10Fe-16W-4Nb alloy sputtering target with a diameter of 190mm and a thickness of 14mm.

[0055] The compositional uniformity, average grain size, magnetic permeability, and crack condition of the Co-Fe-W-Nb alloy sputtering targets prepared in Examples 1-4 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0056] The test method for compositional uniformity is as follows: after sampling different parts of the same alloy sputtering target, the alloy composition is analyzed by inductively coupled plasma mass spectrometry (ICP-MS).

[0057] The test for magnetic permeability shall be performed in accordance with the test method in ASTM F2806-01.

[0058] Table 1 As can be seen from the data in Table 1, the 64Co-15Fe-15W-6Nb alloy sputtering target prepared in Example 1 has good compositional uniformity, small grain size, high magnetic permeability, and no cracking. In Comparative Examples 1 and 2, the cooling rate was too slow, resulting in a significant increase in the grain size of the target material, thus causing a significant decrease in magnetic permeability compared to Example 1. In Comparative Example 3, to accelerate the cooling rate, the casting thickness of the target material was controlled to about 8 mm, and the cooling rate reached 27~32℃ / min. This excessively fast cooling rate resulted in greater brittleness of the target blank, poor machinability, and easy breakage during processing; therefore, the magnetic permeability of the target material was not tested. In Comparative Example 4, the alloy casting thickness was about 28 mm, resulting in a significantly lower uniformity of the prepared target material compared to Example 1. Furthermore, due to the occurrence of cracking, the magnetic permeability of the target material was not tested.

[0059] In Example 2, the order of feeding metal materials was not controlled, and the uniformity of the prepared target material was significantly reduced compared to Example 1. This may be because W has a high density and a high melting point, and it is easy to settle to the bottom of the crucible, resulting in unevenness of the target material.

[0060] In Examples 3 and 4, the main adjustments were made to the preparation process parameters of the target material and the proportion of each element in the target material. The overall performance of the target material may fluctuate to some extent, but it maintains good overall performance.

[0061] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a Co-Fe-W-Nb alloy sputtering target, characterized in that: The following steps are involved: (1) Adding Fe metal, Nb metal, Co-W master alloy, and Co metal into a melting furnace for vacuum induction melting to obtain an alloy melt; (2) Casting the alloy melt in step (1) into a mold, controlling the cooling rate of the mold to be 13-26°C / min during the casting process; after cooling and demolding, obtaining a target blank; wherein the casting thickness is 12-25 mm; (3) The target blank in step (2) is machined to obtain a Co—Fe—W—Nb alloy sputtering target.

2. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 1, characterized in that: The structural formula of the Co-Fe-W-Nb alloy is (Co 100-Y Fe Y ) 100-X (W 14~19 Nb 1~6 ) X , wherein: 20at%≤X≤28at%, 0<Y<100at%; in the step (1), Fe metal, Nb metal, Co-W master alloy, and Co metal are added according to the atomic percentage of Co, Fe, W, and Nb in the structural formula of the Co-Fe-W-Nb alloy.

3. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 1 or 2, characterized in that: In the step (1), the temperature of the vacuum induction melting is 1600-1670° C., and the time of the vacuum induction melting is 40-60 min.

4. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 1 or 2, characterized in that: In the step (1), the order of adding Fe metal, Nb metal, Co-W master alloy and Co metal into the smelting furnace is Fe metal, Nb metal, Co-W master alloy and Co metal.

5. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 1, characterized in that: In the step (1), the preparation method of the Co-W master alloy comprises the following steps: Co metal and W metal are added into a smelting furnace alternately in layers, magnetic suspension smelting is performed, and after smelting, the smelting is completed, cooling is performed to obtain the Co-W master alloy.

6. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 5, characterized in that: The mass ratio of the Co metal to the W metal is (1-4):

1.

7. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 5 or 6, characterized in that: The temperature of the magnetic suspension melting is 2500-3000° C., the time of the magnetic suspension melting is 10-15 minutes, and the number of magnetic suspension melting is 2-3 times.

8. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 1, characterized in that: In the step (2), the casting speed is 2-3 kg / s.

9. The method for preparing a Co-Fe-W-Nb alloy sputtering target according to claim 1, characterized in that: In the step (3), machining includes wire cutting and grinding of the target blank.

10. A Co-Fe-W-Nb alloy sputtering target, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

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