Composite powder for preparing copper sputtering target material and preparation method of copper sputtering target material
By designing a composite ratio of micron-sized spherical copper powder and nano-sheet copper powder, along with a solid in-situ reducing agent, and combining warm pressing and low-temperature in-situ reduction-high-temperature densification processes, the problems of high equipment costs, high energy consumption, and difficulty in removing oxygen impurities in existing high-purity, high-density oxygen-free copper sputtering targets have been solved, achieving efficient and economical preparation of copper sputtering targets.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG METALLURGICAL RES INST
- Filing Date
- 2026-02-26
- Publication Date
- 2026-05-19
AI Technical Summary
Existing technologies for preparing high-purity, high-density oxygen-free copper targets suffer from problems such as high equipment investment, high energy consumption, low production efficiency, difficulty in removing oxygen impurities, large grain size, large resistivity fluctuations, and high risk of thermal cycling cracking. These issues make it difficult to meet the economic and large-scale production requirements of large-size targets.
The method employs a composite ratio of micron-sized spherical copper powder and nano-sheet copper powder, with the addition of a solid in-situ reducing agent. Through a two-step sintering process of warm pressing and low-temperature in-situ reduction followed by high-temperature densification, deep deoxidation is achieved using the built-in solid reducing agent. Combined with multi-scale powder gradation and reasonable segmented heating, the method reduces equipment costs and energy consumption, while improving density and microstructure uniformity.
It significantly improves the density and microstructure uniformity of copper sputtering targets, reduces oxygen content, refines grains, reduces equipment costs and energy consumption, and meets the economic and large-scale production needs of large-size targets.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of sputtering target preparation, and particularly relates to a composite powder for preparing copper sputtering targets and a method for preparing copper sputtering targets. Background Technology
[0002] High-purity, high-density oxygen-free copper sputtering targets are the core basic materials for manufacturing thin films for high-end integrated circuits and flat panel displays. Their performance directly determines the conductivity uniformity, defect rate, and device reliability of the thin film. The current industrial-scale preparation route mainly relies on the traditional powder metallurgy process. This process uses a single-particle-size powder combined with constant-scale pressing and cold isostatic pressing to form a composite, followed by long-term high-temperature sintering.
[0003] The significant application bottlenecks of this technology path are mainly as follows: On the one hand, densification heavily relies on cold isostatic pressing and ultra-high pressure treatment, resulting in huge equipment investment, extremely high energy consumption, and low production efficiency; on the other hand, the sintering process mainly relies on externally introduced reducing atmosphere for deoxidation, which is difficult to effectively remove oxygen impurities trapped between and inside the powder particles. To achieve the target density, extremely high sintering temperatures or ultra-long holding times are often required. This not only leads to abnormally large grains and affects the uniformity of sputtered film thickness, but also easily induces resistivity fluctuations in the sputtered film due to differences in grain orientation. Especially for highly reactive metals such as copper, existing processes often require the introduction of organic binders to suppress oxidation. The residual carbides in these binders easily form "micro-particle" defects, causing poor brightness and dark spot performance in the display panel.
[0004] Furthermore, the green blanks after cold isostatic pressing still exhibit a density distribution gradient, which can easily lead to micro-cracks due to uneven shrinkage during subsequent sintering, significantly increasing the risk of thermal cycling cracking during use after the target material is bonded. Although vacuum hot pressing technology can control oxygen content to some extent, it is limited by its long production cycle per piece, complex equipment, and high cost, making it difficult to meet the economic and large-scale mass production requirements of advanced panel technology for large-size targets. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a composite powder for preparing copper sputtering targets. It employs a composite ratio of micron-sized spherical copper powder and nano-sheet copper powder, and adds a solid in-situ reducing agent, enabling the mixed powder to simultaneously possess high packing density, excellent sintering activity, and self-reducing function. Furthermore, it provides a method for preparing copper sputtering targets, replacing the traditional cold isostatic pressing process with a warm pressing process. Then, a two-step sintering process of low-temperature in-situ reduction followed by high-temperature densification is used, utilizing an embedded solid reducing agent to achieve deep deoxidation from the inside out, thereby obtaining a high-purity, dense, oxygen-free copper sputtering target.
[0006] The specific solution of this invention is as follows: One of the objectives of this invention is to provide a composite powder for preparing copper sputtering targets, the components of which include: copper powder and a solid in-situ reducing agent; The copper powder includes copper powder A, copper powder B and copper powder C; copper powder A has a particle size of 30~50μm, copper powder B has a particle size of 10~20μm and copper powder C has a particle size of 100~500 nm; the solid in-situ reducing agent is selected from at least one of copper formate, urea and oxalic acid.
[0007] Preferably, the mass ratio of copper powder A, copper powder B and copper powder C is (65~75):(20~28):(3~7).
[0008] Preferably, copper powder A and copper powder B are spherical powders, and copper powder C is flake powder.
[0009] Preferably, the content of the solid in-situ reducing agent is 0.1% to 1% of the total amount of copper powder.
[0010] Preferably, the particle size of the solid in-situ reducing agent is 5~20μm.
[0011] A second objective of this invention is to provide a method for preparing the composite powder, comprising: mixing copper powder with a solid in-situ reducing agent under an inert atmosphere.
[0012] Preferably, the mixing speed is 15-30 rpm and the mixing time is 120-240 min. More preferably, the inert atmosphere is either argon or nitrogen.
[0013] Preferably, copper powder and solid in-situ reducing agent are mixed in a mixer, and the loading amount is 30% to 50% of the effective volume of the mixing tank.
[0014] The third objective of this invention is to provide a method for preparing a copper sputtering target, comprising: S1. The above-mentioned composite powder is pressed into shape to obtain a green body; S2. Under a reducing atmosphere, the obtained green body is first reduced in situ to decompose the solid reducing agent and generate reducing gas; then sintering is performed.
[0015] Preferably, in S2, the in-situ reduction temperature is 300~400℃ and the holding time is 60~120min; more preferably, the heating rate in this stage is 3~8℃ / min.
[0016] Preferably, in S2, the sintering temperature is 1000~1050℃ and the holding time is 120~180min; more preferably, the heating rate in this stage is 2~5℃ / min.
[0017] Preferably, in S2, the sintering temperature is 1020~1040℃.
[0018] Preferably, in S2, the reducing atmosphere is either high-purity hydrogen or hydrogen from ammonia decomposition; more preferably, the dew point of high-purity hydrogen is ≤-40℃.
[0019] Preferably, in S1, the composite powder is preheated to 80~120℃ under vacuum conditions, and the pressing conditions are 100~200MPa for 0.5~2 min; more preferably, the vacuum degree is ≤100Pa.
[0020] The fourth objective of this invention is to provide a copper sputtering target, which is prepared by the above method.
[0021] The beneficial technical effects of this invention are as follows: The composite powder for copper sputtering targets provided by this invention adopts the design concept of built-in solid in-situ reducing agent. The specific solid in-situ reducing agent has three major characteristics: low temperature decomposition, strong reducing power and no harmful residue. The resulting composite powder has self-reducing properties.
[0022] The preferred scheme further combines multi-scale powder gradation, using composite micron-sized spherical copper powder and nanosheet copper powder to achieve a composite powder with both high packing density and high sintering activity. The micron-sized spherical powder, with its excellent flowability, constructs a high-density, uniform packing framework, ensuring good formability and strength of the green body. The nanosheet powder plays multiple key roles: its two-dimensional morphology effectively fills the pores between the spherical powder particles, increasing packing density; its extremely high specific surface area provides a significant driving force for sintering, significantly reducing densification temperature and time; and it also acts as pinning points for grain growth, refining and homogenizing the final microstructure.
[0023] Based on the aforementioned composite powder, the method for preparing the copper sputtering target provided by this invention employs a two-step sintering process after forming, utilizing a rationally segmented heating method to precisely match the physicochemical changes required by the material at different stages. Specifically: The first step is in-situ reduction, which is carried out in a low-temperature range for a sufficient time to allow the built-in solid reducing agent to continuously decompose and release a reducing atmosphere, thereby removing the oxide layer on the particle surface and oxygen impurities in the closed pores from the inside out, achieving deep deoxidation. The second step is sintering. Relying on the clean copper surface and the high activity of nanoparticles, grain boundary diffusion and material migration are promoted, achieving rapid densification at a lower temperature and inhibiting grain coarsening, resulting in a highly dense sintered body with uniform structure.
[0024] In the preferred embodiment, a warm pressing process is used to preheat the composite powder to a specific temperature, which significantly reduces the deformation resistance and friction effect of copper powder particles, and promotes the powder to achieve full rearrangement and plastic flow under moderate pressure, thereby significantly improving the green density and uniformity, and eliminating the dependence on cold isostatic pressing technology.
[0025] In summary, this invention can significantly improve the density of copper sputtering targets, reduce the oxygen content of copper sputtering targets, and refine the grain structure through the synergy of materials and processes, while reducing equipment costs and energy consumption, and has good prospects for industrial application. Detailed Implementation
[0026] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.
[0027] Example 1 A composite powder for preparing copper sputtering targets comprises: 45μm spherical atomized copper powder (70wt%), 15μm spherical electrolytic copper powder (25wt%), 500nm flake copper powder (5wt%), and 10μm copper formate, wherein the content of copper formate is 0.5% of the total amount of copper powder.
[0028] The method for preparing the composite powder described in this embodiment is as follows: under nitrogen protection, the above-mentioned components are added to a mixer and mixed for 180 minutes at a mixing speed of 25 rpm; wherein, the loading amount is 35% of the effective volume of the mixing tank.
[0029] A method for preparing a copper sputtering target, comprising: S1. Under vacuum conditions of ≤100Pa, the composite powder of the copper sputtering target material described in this embodiment is preheated to 100°C and molded, and then warm-pressed at 150MPa for 1min to obtain a green blank. S2. The green compact is reduced in situ in a hydrogen atmosphere with a dew point of -50°C by heating to 350°C at 5°C / min and holding for 90 min. Then, the compact is sintered by heating to 1030°C at 3°C / min and holding for 150 min. After cooling in the furnace, the final product is obtained.
[0030] Example 2 A composite powder for preparing copper sputtering targets comprises: 45μm spherical atomized copper powder (65wt%), 15μm spherical electrolytic copper powder (28wt%), 500nm flake copper powder (7wt%), and 20μm urea, wherein the urea content is 0.8% of the total copper powder. The preparation method of the composite powder in this embodiment is the same as that in Example 1.
[0031] A method for preparing a copper sputtering target differs from Example 1 only in that the composite powder for the copper sputtering target in S1 is replaced with the composite powder for the copper sputtering target described in this example, while the other process steps and parameters are the same as in Example 1.
[0032] Example 3 A method for preparing a copper sputtering target, comprising: S1. Under vacuum conditions of ≤100Pa, the composite powder described in Example 1 is preheated to 80°C and molded, and then warm-pressed at 200MPa for 0.5min to obtain a green body. S2, Same as in Example 1.
[0033] Example 4 A method for preparing a copper sputtering target, comprising: S1, Same as in Example 1; S2. The green compact is heated to 400℃ at a rate of 8℃ / min and held for 60 min in a hydrogen atmosphere with a dew point of -50℃ to complete in-situ reduction. Then, the temperature is increased to 1020℃ at a rate of 2℃ / min and held for 180 min to complete sintering. After cooling in the furnace, the final product is obtained.
[0034] Example 5 A method for preparing a copper sputtering target, which differs from Example 1 only in that step S1 involves molding the copper sputtering target described in Example 1 with composite powder at room temperature to obtain a green blank. All other processes and parameters are the same as in Example 1.
[0035] Example 6 A method for preparing a copper sputtering target, which differs from Example 1 only in that step S2 adopts a one-step sintering method, directly heating to 1030℃ at 5℃ / min and holding for 240 min, while other processes and parameters are the same as in Example 1.
[0036] Example 7 A method for preparing a copper sputtering target, which differs from Example 1 only in that the in-situ reduction temperature in step S2 is 200℃ and the holding time is 90min, while the other processes and parameters are the same as in Example 1.
[0037] Example 8 A method for preparing a copper sputtering target, which differs from Example 1 only in that the sintering temperature in step S2 is 980℃ and the holding time is 180min, while the other processes and parameters are the same as in Example 1.
[0038] Comparative Example 1 A composite powder for preparing copper sputtering targets comprises: 35μm spherical atomized copper powder (100wt%) and 10μm copper formate, wherein the content of copper formate is 0.5% of the total amount of copper powder.
[0039] A method for preparing a copper sputtering target differs from Example 1 only in that step S1 uses the composite powder described in this comparative example, while other process steps and parameters are the same as in Example 1.
[0040] Comparative Example 2 A composite powder for preparing copper sputtering targets comprises: 45μm spherical atomized copper powder, 15μm spherical electrolytic copper powder, and 10μm copper formate, wherein the content of copper formate is 0.5% of the total copper powder; the mass ratio of 45μm spherical atomized copper powder to 15μm spherical electrolytic copper powder is 70:25.
[0041] A method for preparing a copper sputtering target differs from Example 1 only in that the raw material in step S1 is replaced with the composite powder described in this comparative example, while the other process steps and parameters are the same as in Example 1.
[0042] Comparative Example 3 A composite powder for preparing copper sputtering targets comprises: 45μm spherical atomized copper powder (80wt%) and 15μm spherical electrolytic copper powder (20wt%).
[0043] A method for preparing a copper sputtering target differs from Example 1 only in that the raw material in step S1 is replaced with the composite powder described in this comparative example, while the other process steps and parameters are the same as in Example 1.
[0044] Comparative Example 4 A composite powder for preparing copper sputtering targets, which differs from Example 1 only in that no solid in-situ reducing agent is added.
[0045] A method for preparing a copper sputtering target differs from Example 1 only in that the raw material in step S1 is replaced with the composite powder described in this comparative example, while the other process steps and parameters are the same as in Example 1.
[0046] Comparative Example 5 A powder for preparing copper sputtering targets uses atomized spherical copper powder with a single particle size of 35 μm.
[0047] A method for preparing a copper sputtering target differs from Example 1 in that, in step S1, the raw material is replaced with the powder described in this comparative example, a green blank is obtained by room temperature molding, the pressing pressure is 500 MPa, and then sintering is completed in a hydrogen atmosphere with a dew point of -20°C, the temperature is increased to 1050°C at 10°C / min and held for 120 min, and the final product is obtained after furnace cooling.
[0048] The performance of the copper sputtering targets obtained in the above embodiments and comparative examples was tested. The test methods and results are shown below: Oxygen content test: Refer to national standard GB / T 5121.8-2024 "Chemical analysis methods for copper and copper alloys - Part 8: Determination of oxygen, nitrogen and hydrogen content".
[0049] Density test: Refer to the national standard GB / T 3850-2015 "Method for Determination of Density of Dense Sintered Metallic Materials and Hard Alloys". The ratio of the measured density to the density of smelted pure copper (value 8.96 g / cm3) is the density of the sintered billet.
[0050] Grain size testing: Refer to the national standard GB / T 6394-2002 "Method for determination of average grain size of metals".
[0051] Table 1. Test data of oxygen-free copper sputtering targets prepared in the examples and comparative examples.
[0052] Based on the test data in the table, the reasons for the increased oxygen content and decreased density in Examples 5-8 compared to Example 1 are analyzed as follows: Example 5: When pressed at room temperature, the powder has insufficient plastic deformation, and the particles are mainly mechanically interlocked. The elastic aftereffect leads to microscopic defects in the green body, which become the core of pore nucleation during sintering and hinder the densification process.
[0053] Example 6: A rapid heating step causes the reducing agent to decompose violently, and the generated gas cannot be discharged in time. At the same time, the surface oxide is sealed by the densified surface layer, forming internal gas pressure, which causes the billet to expand and produce defects.
[0054] Example 7: Insufficient temperature during the low-temperature stage leads to incomplete decomposition of the reducing agent and insufficient generation of reducing gas. Internal oxides cannot be effectively reduced, and residual oxygen impurities form pinning points, hindering grain boundary migration and densification.
[0055] Example 8: Insufficient sintering temperature leads to insufficient thermodynamic driving force, which cannot overcome the energy barrier of pore shrinkage. Grain boundary and volume diffusion are insufficient, spheroidization of pores occurs but is not eliminated, and the densification process cannot be completed.
[0056] Based on the test data in the table, the reasons for the increased oxygen content and decreased density of Comparative Examples 1-5 compared to Example 1 are analyzed as follows: Comparative Example 1: Single-size powder results in inherent porosity in the particle packing structure, which significantly reduces the initial density of the green body. This leads to an increase in mass transfer distance and insufficient diffusion driving force during subsequent sintering. Porosity cannot be effectively eliminated through grain boundary migration, ultimately forming a non-dense structure.
[0057] Comparative Example 2: The absence of nano-sheet copper powder resulted in insufficient sintering activity in the system, slow neck formation rate in the early stage of sintering, weakened driving force for material migration, hindered densification process, making it difficult to eliminate isolated pores and poor microstructure development.
[0058] Comparative Example 3: The ratio of coarse to fine powder deviates from the optimal packing model, resulting in a decrease in the packing density of the powder, uneven shrinkage during sintering, stress concentration in local areas, and hindering the coordinated elimination of pores and the densification process.
[0059] Comparative Example 4: Relying solely on external atmosphere reduction, the reducing gas has difficulty penetrating into the closed pores, the oxide layer on the particle surface cannot be completely removed, and the residual internal oxide forms a diffusion barrier, which in turn affects grain boundary migration and densification.
[0060] Comparative Example 5: Single grain size and room temperature high pressure pressing result in many pores and internal stress in the green blank. Subsequently, the high dew point atmosphere and rapid sintering prevent the gas and oxides from being discharged. They are sealed inside by the prematurely densified surface layer, eventually forming a defect structure with high oxygen residue, spheroidized pores and coarse grains.
[0061] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A composite powder for preparing copper sputtering targets, characterized in that, Its components include: copper powder and solid in-situ reducing agent; The copper powder includes copper powder A, copper powder B and copper powder C; the particle size of copper powder A is 30~50μm, the particle size of copper powder B is 10~20μm and the particle size of copper powder C is 100~500 nm; the solid in-situ reducing agent is selected from at least one of copper formate, urea and oxalic acid.
2. The composite powder for preparing copper sputtering targets according to claim 1, characterized in that, The mass ratio of copper powder A, copper powder B and copper powder C is (65~75):(20~28):(3~7).
3. The composite powder for preparing copper sputtering targets according to claim 1 or 2, characterized in that, The content of the solid in-situ reducing agent is 0.1% to 1% of the total copper powder.
4. The composite powder for preparing copper sputtering targets according to claim 1 or 2, characterized in that, The particle size of the solid in-situ reducing agent is 5~20μm.
5. The method for preparing composite powder for copper sputtering targets according to any one of claims 1-4, characterized in that, The copper powder is mixed with a solid in-situ reducing agent under an inert atmosphere.
6. The method for preparing composite powder for copper sputtering targets according to claim 5, characterized in that, The mixing speed is 15~30 rpm, and the mixing time is 120~240 min.
7. A method for preparing a copper sputtering target, characterized in that, include: S1. Using the composite powder of any one of claims 1-4 as raw material, press and shape to obtain a green body; S2. Under a reducing atmosphere, the obtained green body is first reduced in situ to decompose the solid reducing agent and generate reducing gas; then sintering is performed.
8. The method for preparing a copper sputtering target according to claim 7, characterized in that, In S2, the in-situ reduction temperature is 300~400℃, and the holding time is 60~120min.
9. The method for preparing a copper sputtering target according to claim 7 or 8, characterized in that, In S2, the sintering temperature is 1000~1050℃ and the holding time is 120~180min; preferably, in S2, the sintering temperature is 1020~1040℃.
10. The method for preparing a copper sputtering target according to claim 7 or 8, characterized in that, In S1, the composite powder is preheated to 80~120℃ under vacuum conditions, and the pressing conditions are 100~200MPa for 0.5~2 min.