Method for efficient recovery of diffusion welding target using electromagnetic induction heating technology

Abstract

The present application relates to the technical field of magnetron sputtering target recovery, and discloses a method for efficient recovery of a diffusion welding target using an electromagnetic induction heating technology. For the diffusion welding target using pure aluminum or an aluminum alloy as an intermediate layer, an electromagnetic induction alternating current is applied to the aluminum intermediate layer, and on the basis of the skin effect of the alternating current, a target blank and the aluminum intermediate layer are rapidly heated in the form of an eddy current. Due to the relatively low melting point, the aluminum intermediate layer can be rapidly heated above the melting point and melted, such that the target blank is separated from the aluminum intermediate layer. Finally, aluminum residues on the surface of the target blank are removed by means of machining turning, and cleaning and drying are carried out, to obtain a high-purity target blank that can be recycled. By employing rapid electromagnetic induction heating, the present application can effectively improve recovery efficiency and economic benefits while ensuring the purity of the target surface, and is environmentally friendly and pollution-free during the recovery process, and can be widely applied to 8-inch and 12-inch targets containing an aluminum intermediate layer.

Description

A method for efficiently recovering diffusion welding targets using electromagnetic induction heating technology

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411181618.2, filed on August 27, 2024, entitled "A Method for Efficiently Recovering Diffusion Welding Target Material Using Electromagnetic Induction Heating Technology", the entirety of which is incorporated herein by reference. Technical Field

[0003] This application relates to the field of magnetron sputtering targets, specifically to a method for efficiently recovering diffusion welding targets containing aluminum intermediate layers using electromagnetic induction heating technology. Background Technology

[0004] Sputtering targets are a key material in semiconductor chip manufacturing. The principle involves gaseous ions bombarding the target at high speed under an external field, depositing the bombarded target atoms onto a silicon wafer to form the complex wiring structure within the semiconductor chip. Sputtering targets typically consist of a target blank and a backplate. For high-power, high-efficiency sputtering targets, diffusion welding is generally used to connect the target blank and the backplate. Currently, to improve weldability and strength while reducing welding stress, a pure aluminum or aluminum alloy interlayer is often added between the target blank and the backplate. However, due to limitations in the mechanism and process of magnetron sputtering, the actual utilization rate of sputtering targets is only 30%–50% of the target blank's net weight. Since magnetron sputtering does not introduce other impurity elements, the used target still contains a considerable amount of high-purity metal target blank. Therefore, the recycling of used targets is of great significance for resource conservation and environmental protection. Simultaneously, for target manufacturers, it can reduce production costs and increase profits.

[0005] Several patents have disclosed methods for separating the target blank and backing plate. One method is mechanical separation: for example, patent documents 1 (CN 104342618) and 2 (CN 105798733) use hydraulic pressure and grinding friction respectively to separate the target blank and backing plate. However, neither method can completely and effectively achieve separation, resulting in low target material recovery efficiency. Another method is chemical separation: for example, patent document 3 (CN 109266854A) uses a combined acid-base dissolution method to remove the backing plate. Although this can effectively recover the target material, the waste liquid treatment is highly polluting and environmentally unfriendly, and the dissolved backing plate cannot be recycled, resulting in resource waste. Additionally, patent document 4 (CN 111748693A) utilizes the different melting points of the target blank and backing plate materials, heating and melting them to achieve separation. However, the residual target inevitably undergoes element diffusion under prolonged high temperatures, which may affect the purity of the target blank.

[0006] In summary, existing sputtering target recycling methods suffer from the following problems: First, they are inefficient and time-consuming, hindering large-scale production; second, the recycling process may damage the purity of the target, affecting its subsequent performance; and third, while some chemical recycling methods can effectively recover targets, they require large quantities of chemical reagents, resulting in high costs and environmental pollution. Therefore, how to efficiently and environmentally recycle sputtering targets, especially those with aluminum-containing interlayers, has become an urgent problem to be solved.

[0007] Existing technical documents

[0008] Patent documents:

[0009] Patent Document 1: CN 104342618

[0010] Patent Document 2: CN 105798733

[0011] Patent Document 3: CN 109266854A

[0012] Patent Document 4: CN 111748693A Summary of the Invention

[0013] This application addresses the aforementioned problems by employing an electromagnetically induced alternating current applied to diffusion welding targets containing an aluminum interlayer. Based on the skin effect of alternating current, the aluminum interlayer is rapidly heated and melted in an eddy current manner, causing the target blank to separate from the interlayer. Finally, aluminum residue on the target blank surface is removed by machining, followed by cleaning and drying to obtain a high-purity target blank that can be recycled. This application utilizes electromagnetic induction for rapid heating, which effectively prevents aluminum diffusion into the target blank, ensuring target surface purity. It also significantly improves recycling efficiency and economic benefits. This recycling method is environmentally friendly and pollution-free, and can be widely applied to 8-inch and 12-inch targets containing an aluminum interlayer.

[0014] To achieve the above objectives, this technical solution mainly adopts the following technical means:

[0015] A method for efficiently recovering diffusion welding targets containing aluminum interlayers using electromagnetic induction heating technology includes the following steps.

[0016] (1) Prepare a diffusion welding target containing an aluminum intermediate layer;

[0017] (2) Place the above target material on a heating table or heating plate and preheat it as a whole;

[0018] (3) Apply an electromagnetic induction alternating current to the surface of the preheated target material to heat the aluminum intermediate layer to rapid melting.

[0019] (4) Separate the molten target material into a target blank and an aluminum intermediate layer;

[0020] (5) The aluminum intermediate layer residue adhering to the separated target blank is removed by machining turning method, and then cleaned and dried to obtain a high-purity target blank.

[0021] (6) Glow discharge mass spectrometry (GDMS) was used to detect and analyze impurity elements in order to confirm the actual purity of the recovered target blank.

[0022] In step (1), the target is a diffusion welding target containing an aluminum interlayer. Typically, the aluminum interlayer material includes pure aluminum or aluminum alloy, such as 1061 aluminum, 6061 aluminum, 5052 aluminum, etc.

[0023] In step (2), the target material is preheated to a temperature between 180°C and 280°C, preferably between 200°C and 260°C. By preheating to the above temperature range, heat dissipation from the backplate is reduced, the melting rate of the aluminum intermediate layer is accelerated, and the recycling efficiency is improved. The preheating method includes, but is not limited to, placing the target material on a heating plate or heating table.

[0024] In step (3): When the target diameter is between 350mm and 450mm, the diameter of the induction coil should be 5mm larger than the target diameter, but not more than 10mm larger, and the operating frequency should be 50-1000Hz. When the target diameter is below 350mm, the diameter of the induction coil should be 5mm larger than the target diameter, but not more than 20mm larger, and the operating frequency should be 1000-2500Hz. The height of the induction coil must be greater than the thickness of the aluminum interlayer, generally between 1cm and 5cm, and the placement position must ensure complete coverage of the aluminum interlayer.

[0025] In step (3), the rapid melting typically takes less than 30 minutes; preferably less than 28 minutes. By heating, the aluminum intermediate layer melts rapidly, effectively preventing aluminum from diffusing into the target blank and ensuring the purity of the target surface.

[0026] In step (4), the method for separating the target blank and the aluminum intermediate layer is a physical separation means. The physical separation means include using tooling molds for separation, magnetic adsorption, etc. For example, using a fixture of appropriate size to separate the target surface, or using a magnetic chuck to adsorb and separate the target surface. There is no particular limitation on the physical means here, as long as it is a physical means that can separate the target blank and the aluminum intermediate layer.

[0027] In step (5): the machining turning method includes turning, milling, drilling, boring, sawing or grinding, etc., but is not limited to the above machining methods. Any method that can remove the intermediate layer can be used.

[0028] In the above-mentioned efficient recycling method for aluminum-containing intermediate layer diffusion welding targets, the target material is a titanium target, tantalum target, tungsten target, cobalt target, nickel-platinum target, etc. In addition, the target material is the target material that needs to be recycled, preferably including used residual target material and target material scrapped in production, but it is not limited to the above-mentioned target materials. Attached Figure Description

[0029] Figure 1 is a process flow diagram of the implementation of this application.

[0030] Figure 2 is a schematic diagram of the residual target structure. Detailed Implementation

[0031] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Furthermore, to make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] In this application, for ease of understanding of the contents of the specification, Figure 2 shows a schematic diagram of the structure of a typical aluminum-containing interlayer target, which includes a target blank, an aluminum interlayer, and a backing plate.

[0034] Furthermore, the recycling method of the residual target blank in the embodiments and comparative examples of this application is carried out according to the process flow diagram in Figure 1, as detailed below.

[0035] Example 1:

[0036] This embodiment uses a high-purity titanium target containing a pure aluminum interlayer as the target. The target surface diameter is 450 mm and the aluminum interlayer thickness is 4 mm. The recycling method of this titanium target billet is as follows.

[0037] After preparing a high-purity titanium target with a pure aluminum interlayer, place the titanium target on a heating table and preheat it to 230°C. Then, use electromagnetic induction heating on the aluminum interlayer of the titanium target. At this time, the diameter of the induction coil is 460mm and the height is 5mm. The coil is placed to completely cover the aluminum interlayer. The operating frequency is 50Hz, so that the aluminum interlayer melts rapidly within 25 minutes.

[0038] Next, a suitably sized fixture was used to clamp the titanium target blank, separating it from the backing plate. The separated target blank was then simply flattened and machined on a conventional lathe to remove residual aluminum. Finally, it was cleaned and dried with a mixture of dichloromethane and anhydrous ethanol to obtain a high-purity titanium target blank. Finally, glow discharge mass spectrometry (GDMS) was used to analyze impurities and confirm the actual purity of the recovered target blank. The results are shown in Table 1.

[0039] Example 2

[0040] This embodiment uses a high-purity nickel-platinum target containing a 5052 aluminum interlayer as the target. The target diameter is 320mm and the aluminum interlayer thickness is 2mm. The recycling process of this nickel-platinum target billet is as follows.

[0041] The prepared nickel-platinum target residue is placed on a heating table and preheated to 260°C. Then, the aluminum intermediate layer of the preheated nickel-platinum target residue is heated by electromagnetic induction. At this time, the diameter of the induction coil is 330 mm and the height is 4 mm. The placement position completely covers the aluminum intermediate layer. The frequency is 1000 Hz, so that the aluminum intermediate layer melts rapidly within 30 minutes.

[0042] Next, the molten nickel-platinum target residue was adsorbed onto the nickel-platinum target surface using a magnetic chuck, separating the target blank from the backing plate. Finally, the target blank was simply flattened and machined on a conventional lathe to remove residual aluminum. After cleaning with a mixture of dichloromethane and anhydrous ethanol and drying, a high-purity nickel-platinum target blank was obtained. Finally, glow discharge mass spectrometry (GDMS) was used to analyze impurities and confirm the actual purity of the recovered target blank. The results are shown in Table 1.

[0043] Example 3

[0044] This embodiment uses a high-purity tantalum target (target material) containing a pure aluminum interlayer as the target. The target surface diameter is 440mm and the aluminum interlayer thickness is 6mm. The recycling process of this tantalum target billet is as follows.

[0045] The prepared high-purity tantalum target was placed on a heating table and preheated to 320°C. Then, electromagnetic induction heating was used on the aluminum intermediate layer of the tantalum target. At this time, the diameter of the induction coil was 445 mm and the height was 10 mm. The coil was placed to completely cover the aluminum intermediate layer. The operating frequency was 50 Hz, so that the aluminum intermediate layer melted rapidly within 28 minutes.

[0046] A tantalum target was mounted using a mold to separate the target blank from the backing plate. The separated tantalum target blank was simply flattened and then machined on a conventional lathe to remove residual aluminum. Finally, the tantalum target blank after removing residual aluminum was cleaned with a mixture of dichloromethane and anhydrous ethanol and dried to obtain a high-purity tantalum target blank. Finally, glow discharge mass spectrometry (GDMS) was used to analyze impurities to confirm the actual purity of the recovered target blank. The results are shown in Table 1.

[0047] Comparative Example 1:

[0048] This embodiment uses a 12-inch high-purity titanium target with a pure aluminum interlayer as the target. The target diameter is 450mm and the aluminum interlayer thickness is 4mm. The titanium target billet recycling process is as follows.

[0049] The prepared titanium target residue was placed on a heating stage and preheated to 100℃. Then, electromagnetic induction heating was applied to the aluminum interlayer of the preheated titanium target residue. The induction coil diameter was 470mm, the height was 5mm, and it was positioned to cover only half of the aluminum interlayer. The operating frequency was 1200Hz, and the aluminum interlayer melting time was 4 hours. Subsequently, the titanium target blank was separated using a fixture. The separated target blank was then machined on a conventional lathe to remove residual aluminum. Finally, the target blank after removing residual aluminum was cleaned with a mixture of dichloromethane and anhydrous ethanol, dried, and analyzed for impurities using glow discharge mass spectrometry (GDMS). The aluminum content of the target blank exceeded the standard, indicating reduced purity. The results are shown in Table 1.

[0050] Comparative Example 2:

[0051] This embodiment uses a high-purity nickel-platinum target containing a 5052 aluminum interlayer as the target. The target diameter is 320mm and the aluminum interlayer thickness is 2mm. The recycling process of this nickel-platinum target billet is as follows.

[0052] Step (1) Place the nickel-platinum target residue on a heating table and preheat it to 130°C.

[0053] Step (2) Electromagnetic induction heating was applied to the aluminum interlayer of the nickel-platinum residual target. The induction coil had a diameter of 355 mm and a height of 4 mm, and was positioned to cover only half of the aluminum interlayer. The operating frequency was 2600 Hz, and the aluminum interlayer melted for 3 hours. Subsequently, the target blank was separated using a fixture, and the separated target blank was machined on a conventional lathe to remove the residual aluminum. Finally, the target blank after removing the residual aluminum was cleaned with dichloromethane mixed with anhydrous ethanol and dried. Impurity element detection and analysis were performed, and the aluminum content of the target blank exceeded the standard, indicating a decrease in purity. The results are shown in Table 1.

[0054] Comparative Example 3:

[0055] This embodiment uses a high-purity tantalum target containing a pure aluminum interlayer as the target. The target diameter is 440 mm and the aluminum interlayer thickness is 6 mm. The tantalum target billet recycling process is as follows.

[0056] Step (1) Place the tantalum target on a heating table and preheat it to 120°C.

[0057] Step (2) Electromagnetic induction heating was applied to the aluminum interlayer of the tantalum target residue. The induction coil had a diameter of 470 mm and a height of 8 mm, and was positioned to cover only half of the aluminum interlayer. The operating frequency was 1200 Hz, and the melting time of the aluminum interlayer was 3.5 h. Subsequently, the target blank was separated using a fixture, and the separated target blank was machined on a conventional lathe to remove the residual aluminum. Finally, the target blank after removing the residual aluminum was cleaned with dichloromethane mixed with anhydrous ethanol and dried. Impurity element detection and analysis were performed using glow discharge mass spectrometry (GDMS). The aluminum content of the target blank exceeded the standard, and the purity was reduced. The results are shown in Table 1.

[0058] Table 1. GDMS purity test results (ppm)

[0059] As shown in Table 1, Examples 1-3 have low aluminum content and high purity. However, compared to Examples 1-3, the aluminum content in the target blanks of Comparative Examples 1-3 is significantly excessive, resulting in reduced purity. Therefore, the recycling method of this application can efficiently recover residual target blanks while ensuring target surface purity, effectively improving recycling efficiency and economic benefits. Furthermore, this recycling method is environmentally friendly and pollution-free, and can be widely applied to the recycling of target materials containing aluminum intermediate layers.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for efficiently recovering diffusion welding targets using electromagnetic induction heating technology, comprising the following steps: (1) Prepare a diffusion welding target containing an aluminum intermediate layer; (2) Place the above target material on a heating table or heating plate and preheat it as a whole; (3) Apply an electromagnetic induction alternating current to the surface of the above target material to heat the aluminum intermediate layer and melt it rapidly; (4) Separate the molten target material into a target blank and an aluminum intermediate layer; (5) The aluminum intermediate layer residue adhering to the separated target blank is removed by machining turning method, and then cleaned and dried to obtain a high-purity target blank. (6) Impurity element detection and analysis were performed using glow discharge mass spectrometry to confirm the actual purity of the recovered target blank.

2. The method for efficient recovery of diffusion welding targets according to claim 1, wherein, The aluminum-containing intermediate layer in step (1) is made of pure aluminum or aluminum alloy, wherein the pure aluminum is 1061 aluminum, 6061 aluminum, or 5052 aluminum.

3. The method for efficient recovery of diffusion welding targets according to claim 1, wherein, In step (2), the entire target material is preheated to above 180°C and below 280°C.

4. The method for efficient recovery of diffusion welding targets according to claim 1, wherein, The rapid melting mentioned in step (3) is within 30 minutes.

5. The method for efficient recovery of diffusion welding targets according to claim 1, wherein, In step (3), when the target diameter is between 350mm and 450mm, the diameter of the induction coil used should be 5mm larger than the target diameter, but not more than 10mm larger than the target diameter, and the frequency used should be between 50-1000Hz. When the target diameter is less than 350mm, the diameter of the induction coil should be 5mm larger than the target diameter, but not more than 20mm larger, and the operating frequency should be between 1000-2500Hz.

6. The method for efficient recovery of diffusion welding targets according to claim 1, wherein, In step (3), the height of the induction coil must be greater than the thickness of the aluminum intermediate layer, and the placement position must ensure that the aluminum intermediate layer is completely covered.

7. The method for efficient recovery of diffusion welding targets according to claim 1, wherein, The methods for separating the target blank and the aluminum intermediate layer in step (4) include physical separation methods such as separation using tooling molds and magnetic adsorption.

8. The method for efficient recovery of diffusion welding targets according to claim 1, wherein, In step (5), the machining turning method is turning, milling, drilling, boring, sawing, or grinding.

9. The method for efficient recovery of diffusion welding targets according to any one of claims 1-8, wherein, The target materials include titanium targets, tantalum targets, tungsten targets, cobalt targets, and nickel-platinum targets.

10. The method for efficient recovery of diffusion welding targets according to any one of claims 1-8, wherein, The target material refers to the target material that needs to be recycled, including used residual target material and target material that is scrapped during production.

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