Preparation method of ultra-high purity CuAl alloy

Abstract

The application provides a preparation method of ultra-high-purity CuAl alloy, and the preparation method comprises the following steps: preparing an alloy ingot raw material, the center of the alloy ingot raw material is aluminum, and the outer side of the aluminum is coated with copper; placing electrolytic copper and the obtained alloy ingot raw material into a graphite crucible to perform vacuum induction smelting, and obtaining the ultra-high-purity CuAl alloy. The preparation method of the ultra-high-purity CuAl alloy provided by the application effectively avoids the introduction of carbon particles into the alloy due to the direct contact between aluminum and the graphite crucible during smelting, and avoids the alloy composition not meeting the requirements due to the burning loss of aluminum, so that the purity and quality of the alloy are improved, and the use requirements of high-quality target materials can be met.

Description

Technical Field

[0001] This invention belongs to the field of alloy preparation technology, and relates to a CuAl alloy, and more particularly to a method for preparing an ultra-high purity CuAl alloy. Background Technology

[0002] With the rapid development of very large-scale integrated circuits (VLSI), semiconductor chip sizes have shrunk to the nanometer level. RC delay and electromigration in metal interconnects have become major factors affecting chip performance. Compared to traditional aluminum and aluminum alloys, copper has higher resistance to electromigration and higher conductivity, especially ultra-high purity copper (purity ≥6N), which is crucial for reducing interconnect resistance and improving processing speed. Below the 14nm semiconductor process node, the electromigration problem of ultra-high purity copper is more severe. Currently, ultra-high purity CuAl alloy targets are used as a barrier layer during wiring. This improves the wettability between the copper conductor and the SiO2 substrate and mitigates the diffusion of Cu atoms from the copper conductor into the SiO2 substrate, reducing conductivity losses in the semiconductor chip. Currently, CuAl alloys are prepared using a melting method.

[0003] CN104561618A discloses a method for smelting aluminum-copper alloys. This method involves continuously immersing a copper tube into molten pure aluminum to produce a copper-aluminum alloy with uniform composition and minimal segregation.

[0004] CN115261655A discloses an ultra-high purity CuAl alloy, its preparation method and application. The method involves vacuum induction melting of ultra-high purity electrolytic Cu and ultra-high purity Cu-xAl master alloy in a crucible to obtain the ultra-high purity CuAl alloy.

[0005] CN115466862A discloses a smelting process for ultra-high purity copper-aluminum alloy. The process involves melting copper material under vacuum, then adding aluminum material three times while it is being purged, followed by static refining, and finally casting to obtain the ultra-high purity copper-aluminum alloy.

[0006] In existing technologies, when preparing ultra-high purity CuAl alloys by melting ultra-high purity Cu and ultra-high purity Al, the melting points of pure copper (melting point 1083℃) and pure aluminum (melting point 660℃) differ significantly. During the melting process, aluminum is easily burned off, resulting in alloy composition that does not meet requirements. On the other hand, the melting process is generally carried out in a high-purity graphite crucible. Aluminum has a lower melting point, and after heating, aluminum will preferentially melt and directly contact the graphite crucible. As the temperature continues to rise, aluminum is prone to react with the crucible, thereby introducing carbon particles into the alloy solution, ultimately causing particle abnormalities during the use of the target material.

[0007] Therefore, in view of the shortcomings of the existing technology, there is a need to provide a method for preparing ultra-high purity CuAl alloy. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing ultra-high purity CuAl alloy, which can improve the purity and quality of CuAl alloy and meet the requirements for use as a target material.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for preparing ultra-high purity CuAl alloy, the method comprising the following steps:

[0011] (1) Prepare alloy ingot raw materials, wherein the center of the alloy ingot raw materials is aluminum and the outer side of the aluminum is coated with copper;

[0012] (2) Electrolytic copper and the alloy ingot raw material obtained in step (1) are placed in a graphite crucible and vacuum induction melting is performed to obtain ultra-high purity CuAl alloy.

[0013] The preparation method provided by this invention involves coating aluminum in copper during the feeding process and then smelting to prepare an ultra-high purity CuAl alloy. This avoids the introduction of carbon particles due to direct contact between aluminum and the crucible during the smelting process, and also solves the problem of non-compliance with composition caused by aluminum burn-off, thereby improving the purity and quality of the alloy.

[0014] The ultra-high purity of the present invention is ≥6N.

[0015] Preferably, in the alloy ingot raw material of step (1), the purity of aluminum is 5N-5N5, for example, it can be 99.999wt%, 99.9991wt%, 99.9992wt%, 99.9993wt%, 99.9994wt% or 99.9995wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, the purity of the copper in the alloy ingot raw material in step (1) and the electrolytic copper in step (2) are both ≥6N, for example, 99.9999wt%, 99.99992wt%, 99.99994wt%, 99.99995wt%, 99.99996wt%, 99.99998wt%, or 99.99999wt%, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] In step (1), the copper coating thickness in the alloy ingot raw material is ≥20mm, for example, it can be 20mm, 25mm, 30mm, 40mm, 50mm, 80mm or 100mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the preparation method of the alloy ingot raw material in step (1) includes: first preparing a copper ingot container with one end open, placing the aluminum ingot into the copper ingot container, then covering the opening of the copper ingot container with the copper ingot and sealing it.

[0019] Preferably, the wall thickness of the copper ingot container, the bottom thickness of the copper ingot container, and the height of the copper ingot are all ≥20mm.

[0020] Preferably, the opening diameter of the copper ingot container is greater than or equal to the diameter of the aluminum ingot.

[0021] Preferably, the sum of the heights of the copper ingot and the aluminum ingot is the same as the opening depth of the copper ingot container.

[0022] Preferably, the sealing method includes laser welding and / or electron beam vacuum welding.

[0023] Preferably, the purity of the graphite crucible in step (2) is ≥5N, for example, it can be 99.999wt%, 99.9992wt%, 99.9994wt%, 99.9995wt%, 99.9996wt%, 99.9998wt%, or 99.9999wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the vacuum degree of the vacuum induction melting in step (2) is 10. -4 -10 -3 Pa, for example, could be 10. -4 Pa, 2×10 -4 Pa, 4×10 -4 Pa, 5×10 -4 Pa, 6×10 -4 Pa, 8×10 -4 Pa or 10 -3 Pa, but not limited to the listed values, applies to other unlisted values ​​within the range as well.

[0025] Preferably, the temperature of vacuum induction melting in step (2) is 1200-1300℃, for example, it can be 1200℃, 1220℃, 1240℃, 1250℃, 1260℃, 1280℃ or 1300℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the vacuum induction melting time in step (2) is 30-40 min, for example, it can be 30 min, 32 min, 34 min, 35 min, 36 min, 38 min or 40 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, in the CuAl alloy described in step (2), the aluminum content is 0.05-1wt%, for example, it can be 0.05wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.8wt%, or 1wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The method for preparing ultra-high purity CuAl alloy provided by this invention effectively avoids the introduction of carbon particles into the alloy due to direct contact between aluminum and graphite crucible during smelting by designing the feeding method, and avoids aluminum burn-off that would cause the alloy composition to fail to meet requirements, thereby improving the purity and quality of the alloy and meeting the needs of high-quality target materials. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the alloy ingot raw material in Embodiment 1 of the present invention;

[0031] Figure 2 This is a cross-sectional view of the alloy ingot raw material of Embodiment 1 of the present invention;

[0032] Among them, 1 is a copper ingot; 2 is an aluminum ingot; and 3 is a copper ingot container. Detailed Implementation

[0033] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0034] To clearly illustrate the technical solution of the present invention, in the embodiments of the present invention, the aluminum content in CuAl alloy is determined by OES (direct reading spectrometer), the content of acid-insoluble ions in the alloy is detected by LPC (liquid particle counter), and the alloy defects are detected by ultrasonic non-destructive testing.

[0035] Example 1

[0036] This invention provides a method for preparing an ultra-high purity CuAl alloy, wherein the aluminum content of the ultra-high purity CuAl alloy is 0.5 wt%, and the preparation method includes the following steps:

[0037] (1) Prepare an ultra-high purity copper ingot container, an ultra-high purity aluminum ingot, and an ultra-high purity copper ingot, each with an open end. The aluminum ingot has a diameter of 35 mm and a height of 40 mm. The copper ingot container has a wall thickness and a bottom thickness of 30 mm. The total opening depth of the copper ingot container is 70 mm. The opening diameter of the 40 mm depth portion inside the opening of the copper ingot container is 35 mm, and the opening diameter of the 30 mm depth portion at the end of the opening is 40 mm. The copper ingot has a diameter of 40 mm and a height of 30 mm. Place the aluminum ingot into the copper ingot container, then cover the opening with the copper ingot. Seal the opening using laser welding to obtain the alloy ingot raw material. The structural schematic diagram and cross-sectional diagram of the alloy ingot raw material are shown below. Figure 1 and 2 As shown;

[0038] (2) The remaining copper raw material in the CuAl alloy, in the form of ultra-high purity electrolytic copper and the alloy ingot raw material obtained in step (1), is placed in a high-purity graphite crucible for vacuum induction melting. The vacuum degree during melting is 5×10⁻⁶. -4 Pa, melting temperature is 1250℃, melting time is 35min.

[0039] In this embodiment, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status after alloy smelting are listed in Table 1.

[0040] Example 2

[0041] This invention provides a method for preparing an ultra-high purity CuAl alloy, wherein the aluminum content of the ultra-high purity CuAl alloy is 0.05 wt%, and the preparation method includes the following steps:

[0042] (1) Prepare an ultra-high purity copper ingot container, an ultra-high purity aluminum ingot, and an ultra-high purity copper ingot with one open end. The aluminum ingot has a diameter of 35 mm and a height of 40 mm. The copper ingot container has a wall thickness and a bottom thickness of 20 mm. The total opening depth of the copper ingot container is 60 mm. The opening diameter of the 40 mm deep part inside the opening of the copper ingot container is 35 mm. The opening diameter of the 20 mm deep part at the end of the opening of the copper ingot container is 40 mm. The copper ingot has a diameter of 40 mm and a height of 20 mm. Place the aluminum ingot into the copper ingot container and then cover the opening with the copper ingot. Seal the opening with laser welding to obtain the alloy ingot raw material.

[0043] (2) The remaining copper raw material in the CuAl alloy, in the form of ultra-high purity electrolytic copper and the alloy ingot raw material obtained in step (1), is placed in a high-purity graphite crucible for vacuum induction melting. The vacuum degree during melting is 10. -4 Pa, melting temperature is 1200℃, melting time is 40min.

[0044] In this embodiment, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status after alloy smelting are listed in Table 1.

[0045] Example 3

[0046] This invention provides a method for preparing an ultra-high purity CuAl alloy, wherein the aluminum content of the ultra-high purity CuAl alloy is 1 wt%, and the preparation method includes the following steps:

[0047] (1) Prepare an ultra-high purity copper ingot container, an ultra-high purity aluminum ingot, and an ultra-high purity copper ingot with one open end. The aluminum ingot has a diameter of 35 mm and a height of 40 mm. The copper ingot container has a wall thickness and a bottom thickness of 50 mm. The total opening depth of the copper ingot container is 90 mm. The opening diameter of the 40 mm deep part inside the opening of the copper ingot container is 35 mm. The opening diameter of the 50 mm deep part at the end of the opening of the copper ingot container is 40 mm. The copper ingot has a diameter of 40 mm and a height of 50 mm. Place the aluminum ingot into the copper ingot container and then cover the opening with the copper ingot. Seal the opening with laser welding to obtain the alloy ingot raw material.

[0048] (2) The remaining copper raw material in the CuAl alloy, in the form of ultra-high purity electrolytic copper and the alloy ingot raw material obtained in step (1), is placed in a high-purity graphite crucible for vacuum induction melting. The vacuum degree during melting is 10. -3 Pa, melting temperature is 1300℃, melting time is 30min.

[0049] In this embodiment, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status after alloy smelting are listed in Table 1.

[0050] Example 4

[0051] This invention provides a method for preparing ultra-high purity CuAl alloy. Compared with Example 1, the melting temperature in step (2) is controlled at 1000℃, and the rest are the same as in Example 1.

[0052] In this embodiment, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status after alloy smelting are listed in Table 1.

[0053] Example 5

[0054] This invention provides a method for preparing ultra-high purity CuAl alloy. Compared with Example 1, the melting temperature in step (2) is controlled at 1500℃, and the rest are the same as in Example 1.

[0055] In this embodiment, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status after alloy smelting are listed in Table 1.

[0056] Example 6

[0057] This invention provides a method for preparing ultra-high purity CuAl alloy. Compared with Example 1, the melting time in step (2) is controlled to be 20 min, and the rest are the same as in Example 1.

[0058] In this embodiment, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status after alloy smelting are listed in Table 1.

[0059] Example 7

[0060] This invention provides a method for preparing ultra-high purity CuAl alloy. Compared with Example 1, the melting time in step (2) is controlled to be 50 min, and the rest are the same as in Example 1.

[0061] In this embodiment, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status after alloy smelting are listed in Table 1.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing an ultra-high purity CuAl alloy. Compared with Example 1, step (2) involves directly adding the same amount of ultra-high purity copper and ultra-high purity aluminum as in Example 1 into the crucible, while the rest is the same as in Example 1.

[0064] In this comparative example, the actual aluminum content, burn-off rate, acid-insoluble particle content, and defect status of the alloy after smelting are listed in Table 1.

[0065] Table 1

[0066]

[0067] In the table, " / " indicates no data.

[0068] As can be seen from Table 1:

[0069] In Examples 1-3, the CuAl alloys prepared by the preparation method provided by the present invention can effectively control the Al content in the alloy, with no Al loss during the smelting process, and the content of acid-insoluble particles in the alloy is low, resulting in high alloy purity and good quality.

[0070] Compared with Example 1, in Example 4, the melting temperature was too low, resulting in incomplete melting of copper and uneven distribution of alloy composition; in Example 5, the melting temperature was too high, causing significant Al loss during melting and affecting alloy quality; in Example 6, the melting time was too short, preventing the alloy from being fully melted and resulting in uneven distribution of alloy composition; in Example 7, the melting time was too long, also causing some Al loss during melting and affecting alloy composition. Therefore, it can be seen that the CuAl alloy prepared by the preferred preparation process of this invention can further improve the purity and quality of the alloy.

[0071] Compared with Example 1, the CuAl alloy prepared by the feeding method of Comparative Example 1 showed greater Al burn-off and introduced more impurity particles during the melting process, resulting in reduced alloy purity and defects, making it difficult to meet the requirements for use as a target material.

[0072] In summary, the method for preparing ultra-high purity CuAl alloy provided by this invention effectively avoids the introduction of carbon particles into the alloy due to direct contact between aluminum and graphite crucible during smelting by designing the feeding method, and also avoids aluminum burn-off that would cause the alloy composition to fail to meet requirements, thereby improving the purity and quality of the alloy and meeting the needs of high-quality target materials.

[0073] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an ultra-high purity CuAl alloy, characterized in that, The preparation method includes the following steps: (1) Prepare alloy ingot raw materials, wherein the center of the alloy ingot raw materials is aluminum and the outside of the aluminum is coated with copper; the preparation method of the alloy ingot raw materials includes: first preparing a copper ingot container with one end open, placing the aluminum ingot into the copper ingot container, then covering the opening of the copper ingot container with the copper ingot and sealing it. (2) Electrolytic copper and the alloy ingot raw material obtained in step (1) are placed in a graphite crucible and vacuum induction melting is performed to obtain ultra-high purity CuAl alloy.

2. The preparation method according to claim 1, characterized in that, In step (1), the purity of aluminum in the alloy ingot raw material is 5N-5N5.

3. The preparation method according to claim 1, characterized in that, The purity of the copper in the alloy ingot raw material in step (1) and the electrolytic copper in step (2) are both ≥6N.

4. The preparation method according to claim 1, characterized in that, In step (1), the copper coating thickness in the alloy ingot raw material is ≥20mm.

5. The preparation method according to claim 1, characterized in that, The sealing methods include laser welding and / or electron beam vacuum welding.

6. The preparation method according to claim 1, characterized in that, The purity of the graphite crucible in step (2) is ≥5N.

7. The preparation method according to claim 1, characterized in that, The vacuum degree of the vacuum induction melting in step (2) is 10. -4 -10 -3 Pa.

8. The preparation method according to claim 1, characterized in that, The temperature of vacuum induction melting in step (2) is 1200-1300℃.

9. The preparation method according to claim 1, characterized in that, The vacuum induction melting time in step (2) is 30-40 minutes.

10. The preparation method according to claim 1, characterized in that, In step (2), the aluminum content in the CuAl alloy is 0.05-1 wt%.

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