A low-oxygen fine-grained aluminum-scandium-germanium alloy target and its preparation method

Abstract

This invention provides a low-oxygen, fine-grained aluminum-scandium-germanium alloy target and its preparation method, belonging to the field of metal and alloy target processing and preparation technology. In this method, high-purity aluminum powder, scandium hydride powder, and germanium powder are homogenized using a powder mixer to obtain a mixed powder. Scandium hydride powder acts as an oxygen depletor, decomposing at 700-800℃ to produce H2. H2 has strong permeability and can diffuse along the grain boundaries of metal particles, achieving simultaneous removal of the surface and internal oxide layers, thereby reducing the oxygen content. Doping with high-purity metallic germanium powder can enhance the strength and toughness of the aluminum-scandium alloy. Germanium can form compounds with aluminum and scandium and further undergo solid solution treatment, thereby improving the alloy's strength, conductivity, forgeability, and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of metal and alloy target processing and preparation technology, specifically relating to a low-oxygen fine-grained aluminum-scandium-germanium alloy target and its preparation method. Background Technology

[0002] High-purity aluminum sputtering targets are widely used across various industries. In the semiconductor field, they are used for thin film deposition. Beyond semiconductors, high-purity aluminum targets are also used to manufacture reflective layers in optical devices, protective and decorative coatings in the aerospace and automotive industries, and barrier layers in packaging materials. However, aluminum targets prepared using existing technologies suffer from large grain sizes, poor processing performance, and poor corrosion resistance. Therefore, a forging-rolling process is needed to refine the grains and improve density.

[0003] Aluminum-scandium alloy sputtering targets possess excellent corrosion resistance, thermal stability, and low resistivity. High-purity AlScN thin films sputtered from aluminum-scandium alloy targets exhibit superior piezoelectric properties, making them a core material for manufacturing filter chips, MEMS sensors, drivers, microphones, and energy harvesters. However, due to the extremely low solubility of scandium in aluminum, increasing scandium content leads to the formation of numerous brittle intermetallic alloys in the alloy system. Current processes for preparing high-scandium-content aluminum-scandium alloy sputtering targets still face technical challenges such as cracking, segregation, and oxidation.

[0004] Doping low-scandium-content aluminum-scandium alloys with high-purity germanium enhances their strength and toughness. The atomic size difference between germanium and aluminum leads to lattice distortion, resulting in solid solution strengthening and preventing the formation of brittle intermediate alloys. Germanium and scandium form composite precipitates that pin grain boundaries, refine grains, and improve the alloy's strength, forgeability, and corrosion resistance. High-purity germanium-doped aluminum-scandium alloys exhibit superior thermal and electrical conductivity compared to pure aluminum and high-scandium-content aluminum-scandium alloys, making them a viable alternative to pure aluminum targets and aluminum-scandium alloy targets. With increasing demand from microelectronics, optoelectronics, and magnetic storage, especially the rise of next-generation 5G communication and cloud computing technologies, the market demand for targets is continuously increasing. Aluminum-scandium-germanium alloy targets have a very broad application prospect and significant market potential. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a low-oxygen, fine-grained aluminum-scandium-germanium alloy target and its preparation method. High-purity aluminum powder, scandium hydride powder, and germanium powder are homogenized using a powder mixer to obtain a mixed powder. The scandium hydride powder acts as an oxygen-consuming agent, decomposing at 700-800℃ to produce H2. H2 has strong permeability and can diffuse along the grain boundaries of metal particles, achieving simultaneous removal of the surface and internal oxide layers, thereby reducing the oxygen content.

[0006] To achieve the above objectives, this solution first provides a method for preparing a low-oxygen, fine-grained aluminum-scandium-germanium alloy target, comprising the following steps:

[0007] S1. Preparation of raw materials: The proportion of high-purity aluminum powder is 70% to 97%, with a purity greater than 5N; the proportion of scandium hydride powder is 2% to 20%, with a purity greater than 3N5; the proportion of germanium powder is 1% to 10%, with a purity greater than 5N. The powders are mixed evenly using a powder mixer under inert gas protection or vacuum environment.

[0008] S2. Isostatic pressing: The powder mixed evenly in step S1 is loaded into a stainless steel mold and pre-pressed using a hydraulic press. After pressing, the mold is removed and then pre-formed using a cold isostatic press. After cold isostatic pressing, the target material is sprayed with an alumina coating. Then, a carbon steel / stainless steel sheath is made and welded. After welding, dehydrogenation, deoxygenation and degassing are promoted at 700-800℃ to obtain an ingot.

[0009] S3. Hot Isostatic Pressing Gradient Sintering: The ingot after S2 welding is placed in a hot isostatic press for gradient sintering. After pre-sintering, it is kept at a certain temperature for initial densification. Then, argon is injected into the hot isostatic press furnace for rapid cooling at a rate of 10-15℃ / min. The final sintering temperature is 500-650℃ and the pressure is 140-170MPa. The temperature and pressure are maintained for 3-6 hours. After the temperature and pressure maintenance stage, the temperature and pressure are reduced simultaneously at a rate of 5-10℃ / min. After hot pressing, the target material cladding is removed by turning to obtain an aluminum scandium germanium target blank. The alumina coating on the target blank surface can be removed by finishing, which indirectly improves the yield. That is, the coating material is the machining allowance for finishing.

[0010] Preferably, the particle size of the aluminum powder, scandium hydride powder, and germanium powder in S1 is <50μm.

[0011] Preferably, the mixing time in S1 is 25-30 minutes.

[0012] Preferably, the pressure of the S2 intercooled isostatic press is 80-100 MPa, and the pressure holding time is 15-30 seconds.

[0013] Preferably, the thickness of the alumina coating in S2 is 0.5-1 mm.

[0014] Preferably, the pre-sintering temperature in S3 is 650-850℃, the pre-sintering pressure is 120-140MPa, and the holding time is 1-5min.

[0015] Preferably, the hot isostatic press has a double-layer water-cooled furnace shell channel on its outer wall.

[0016] Based on a general inventive concept, this solution also provides a low-oxygen fine-grained aluminum-scandium-germanium alloy target.

[0017] The mechanism for preparing low-oxygen aluminum scandium germanium targets in this scheme is as follows:

[0018] This method homogenizes high-purity aluminum powder, scandium hydride powder, and germanium powder using a powder mixer to obtain a mixed powder. Scandium hydride powder acts as an oxygen depletor, decomposing at 700-800℃ to produce H2. H2 has strong penetrability and can diffuse along the grain boundaries of metal particles, achieving simultaneous removal of the surface and internal oxide layers, thereby reducing the oxygen content. Doping with high-purity metallic germanium powder can enhance the strength and toughness of the aluminum-scandium alloy. Germanium can form compounds with aluminum and scandium and further undergo solid solution treatment, thereby improving the alloy's strength, conductivity, forgeability, and corrosion resistance. Since metallic aluminum and germanium are prone to atomic diffusion with the cladding material to form brittle phases, exacerbating the brittleness of the target material, the alumina coating on the target surface effectively blocks the connection between the cladding and the target, thus improving the quality and yield of the target material.

[0019] Conventional hot isostatic pressing (HIP) furnaces use in-furnace cooling. In this design, the furnace outer wall is equipped with a double-layer water-cooled furnace shell channel. Rapid cooling is achieved by enhancing convection through argon injection and pressurization. Material migration and porosity elimination between powder particles are accelerated at high temperatures, improving the density and uniformity of the target material. Furthermore, rapid cooling during HIP sintering effectively suppresses grain coarsening at high temperatures.

[0020] Secondly, the sintering temperature used in this scheme is slightly higher than the recrystallization temperature of aluminum-based alloys, which is beneficial for grain boundary migration and atomic diffusion, but lower than the initial melting temperature to prevent excessive softening or melting of the aluminum matrix. This also promotes the diffusion and uniform distribution of alloying elements, ensuring that the material is in the plastic deformation-dominated stage during densification. This effectively promotes the plastic flow of powder particles and interfacial diffusion, accelerates pore closure, and increases density to near the theoretical value. The uniform distribution of scandium and germanium optimizes the solid solution strengthening effect, while also enhancing grain boundary bonding strength, reducing stress concentration, and improving creep resistance.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The existing casting method for producing aluminum-scandium alloy targets has problems such as ingot composition segregation, high crack defects, and low yield. In particular, the preparation of high scandium content aluminum-scandium alloy targets is difficult to form. Due to the brittle intermetallic compounds, the targets are difficult to form and process. In the traditional powder metallurgy process, the metal powder is easily oxidized during processing and it is not easy to remove impurities and deoxidize. It is necessary to strictly control the oxygen content. At the same time, the density of the target is difficult to guarantee, and high-quality targets cannot be provided. This solution uses scandium hydride powder to act as an oxygen depleting agent. It decomposes at 700-800℃ to produce H2. H2 has strong penetrability and can diffuse along the grain boundaries of metal particles to achieve simultaneous removal of the surface and internal oxide layers, thereby reducing the oxygen content.

[0023] (2) Since aluminum and germanium are prone to atomic diffusion with the cladding material to form a brittle phase, which aggravates the brittleness of the target material, the aluminum oxide coating on the surface of the target material effectively blocks the connection between the cladding and the target material, thereby improving the quality and yield of the target material.

[0024] (3) Conventional hot isostatic pressing furnaces use furnace-in-furnace cooling. In this scheme, the outer wall of the hot isostatic pressing furnace is equipped with a double-layer water-cooled furnace shell channel. Convection is enhanced by argon flushing and pressure to achieve rapid cooling. Material migration and porosity elimination between powder particles are accelerated at high temperatures, improving the density and uniformity of the target material. Rapid cooling and hot isostatic pressing sintering can effectively suppress grain coarsening at high temperatures.

[0025] (4) The aluminum scandium germanium alloy target prepared by the hot isostatic pressing process of this scheme achieves both density and grain refinement, eliminating the need for further heat treatment and simplifying the process. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The ultrasonic C-scan image of the target material prepared in Example 1 of Experimental Example 1;

[0028] Figure 2 This is a SEM image of the target material prepared in Example 1 of Experimental Example 1;

[0029] Figure 3 The ultrasonic C-scan image of the target material prepared in Example 2 of Experimental Example 1;

[0030] Figure 4 SEM image of the target material prepared in Example 2 of Experimental Example 1;

[0031] Figure 5 The image shows the ultrasonic C-mode of the aluminum-scandium-germanium alloy target billet immersed in water in Comparative Example 3.

[0032] Figure 6 The image shows the SEM image of the aluminum-scandium-germanium alloy target blank in Comparative Example 3. Detailed Implementation

[0033] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0034] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.

[0035] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art; unless otherwise specified, the reagents used in the embodiments are all commercially available.

[0036] Example 1

[0037] Preparation of low-oxygen fine-grained aluminum-scandium-germanium alloy sputtering material

[0038] S1. Preparation of raw materials: Weigh 900g of high-purity aluminum powder, 50g of scandium hydride powder, and 50g of germanium powder. The particle size of the powder is <50μm. Mix the powders using a multi-dimensional mixer for 30 minutes to obtain a mixed powder. Load the mixed raw material powder into a stainless steel mold. Clean the mold to avoid contamination of the raw materials.

[0039] S2. Cold Isostatic Pressing: The target material is pre-pressed by a hydraulic press, demolded after pressing, and then pressed into shape by a cold isostatic press. The cold isostatic pressing pressure is 90 MPa, and the holding time is 15 seconds. Alumina particles are sprayed onto the surface of the target material to form a 0.5 mm thick coating. Finally, the target blank is placed in a stainless steel sleeve for welding, and the temperature is raised to 700℃ to start degassing for 1 hour.

[0040] S3. Hot Isostatic Pressing Gradient Sintering: The degassed cladding is placed in a stainless steel tray of a hot isostatic pressing (HIP) apparatus for cold-state pressurization sintering. Pre-pressurization is performed using argon gas at a pressure of 80 MPa. After argon charging, the temperature is raised to 700℃ and held at 130 MPa for 5 minutes for pretreatment. After pretreatment, argon is injected into the furnace to accelerate cooling, reducing the furnace temperature to 550℃ at a rate of 14℃ / min. At this point, the furnace pressure is 170 MPa. The furnace is then held at this temperature and pressure for 3 hours for HIP treatment, with a temperature difference of ±1℃ and a pressure difference of ±0.5 MPa. After holding at this temperature and pressure, the temperature is reduced at a rate of 5℃ / min. The hot isostatic pressing aluminum-scandium-germanium alloy target cladding is removed by machining to obtain an aluminum-scandium-germanium alloy target blank with dimensions of 200 mm × 10 mm.

[0041] Example 2

[0042] Preparation of low-oxygen fine-grained aluminum-scandium-germanium alloy sputtering material

[0043] S1. Raw material preparation: Weigh 800g of high-purity aluminum powder, 150g of scandium hydride powder, and 50g of germanium powder. The powder particle size is <50μm. Mix the powders using a multi-dimensional mixer for 25 minutes to obtain a mixed powder. Load the mixed raw material powder into a stainless steel mold. Clean the mold thoroughly to avoid contaminating the raw materials.

[0044] S2. Cold Isostatic Pressing: The target material is pre-pressed by a hydraulic press, demolded after pressing, and then pressed into shape by a cold isostatic press. The cold isostatic pressing pressure is 100 MPa, and the holding time is 30 seconds. Alumina particles are sprayed onto the surface of the target material to form a 1 mm thick coating. Finally, the target blank is placed in a stainless steel sleeve for welding, and degassing begins at 800℃ for 0.5 hours.

[0045] S3. Hot Isostatic Pressing Gradient Sintering: The degassed cladding is placed in a stainless steel tray of a hot isostatic pressing (HIP) apparatus for cold-state pressurization sintering. Pre-pressurization is performed using argon gas at a pressure of 70 MPa. After argon charging, the temperature is increased to 800℃ and 135 MPa, and held for 3 minutes for pretreatment. After pretreatment, argon is injected into the furnace to accelerate cooling, reducing the furnace temperature to 600℃ at a rate of 12℃ / min. At this point, the furnace pressure is 160 MPa. The furnace is then held at this temperature and pressure for 4 hours for HIP treatment, with a temperature difference of ±1℃ and a pressure difference of ±0.5 MPa. After holding at this temperature and pressure, the temperature is reduced at a rate of 5℃ / min. The hot isostatic pressing aluminum-scandium-germanium alloy target cladding is removed by machining, yielding an aluminum-scandium-germanium alloy target blank with dimensions of 150mm × 18mm.

[0046] Comparative Example 1

[0047] Replace the scandium hydride powder with pure scandium powder, and follow the same steps as in Example 1.

[0048] After removing the casing, the oxygen content of the target blank was tested and found to be 2577 ppm. This indicates that scandium hydride, as a deoxidizer, can effectively reduce the oxygen content of the target material. In contrast, pure metal powder has an increased oxygen content due to the introduction of oxygen during the powder preparation process.

[0049] Comparative Example 2

[0050] No aluminum oxide layer is applied; the remaining steps are the same as in Example 1.

[0051] After removing the cladding, the iron content of the target blank was tested and found to be 2213 ppm. This indicates that the alumina coating can effectively block the diffusion between Fe atoms in the cladding material and the target metal atoms. The absence of an alumina coating increases the processing loss of the target material and reduces the yield.

[0052] Comparative Example 3

[0053] Preparation of aluminum scandium germanium alloy targets by non-gradient sintering

[0054] S1. Preparation of raw materials: Weigh 900g of high-purity aluminum powder, 50g of scandium hydride powder, and 50g of germanium powder. The particle size of the powder is <50μm. Mix the powders using a multi-dimensional mixer for 30 minutes to obtain a mixed powder. Load the mixed raw material powder into a stainless steel mold. Clean the mold to avoid contamination of the raw materials.

[0055] S2. Cold Isostatic Pressing: The target material is pre-pressed by a hydraulic press, demolded after pressing, and then pressed into shape by a cold isostatic press. The cold isostatic pressing pressure is 90 MPa, and the holding time is 15 seconds. Alumina particles are sprayed onto the surface of the target material to form a 0.5 mm thick coating. Finally, the target blank is placed in a stainless steel sleeve for welding, and the temperature is raised to 700℃ to start degassing for 1 hour.

[0056] S3. Hot Isostatic Pressing Gradient Sintering: The degassed cladding is placed in a stainless steel tray of a hot isostatic pressing (HIP) apparatus for cold-pressurized sintering. Pre-pressurization is performed using argon gas at a pressure of 80 MPa. After argon charging, the temperature is increased to 650℃ and 130 MPa, and held at this temperature and pressure for 3 hours for HIP treatment. After the holding period, the temperature is reduced at a rate of 5℃ / min. The HIP-pressed aluminum-scandium-germanium alloy target cladding is removed by machining to obtain the aluminum-scandium-germanium alloy target blank.

[0057] Experimental Example 1

[0058] Examining the properties of the target materials prepared in the examples

[0059] The target preform prepared in Example 1 was subjected to water immersion ultrasonic C-scan. Figure 1 The target blank defect rate was 0.05%. Subsequently, random samples of the target blank were taken, and the oxygen content was analyzed using an oxygen-nitrogen-hydrogen analyzer. The results showed an oxygen content of 256 ppm. Glow discharge mass spectrometry was used to determine the purity of the target blank, and the results showed a purity > 4N, with no other impurities introduced. SEM results are as follows: Figure 2 As shown, the grain size is <40μm, and the elemental composition is shown in Table 1 below:

[0060] Table 1. Impurity element analysis of the target material prepared in Example 1

[0061] element Fe Cu Si Ca Mg Ni C N O Result in ppm 12 5.6 8.1 11 3.3 4.1 46 1.1 256

[0062] The target preform prepared in Example 2 was subjected to water immersion ultrasonic C-scan. Figure 3 As shown, the defect rate of the target blank was 0.08%. Subsequently, random samples of the finished target blank were taken, and the oxygen content was analyzed using an oxygen, nitrogen, and hydrogen analyzer. The results showed an oxygen content of 380 ppm. Glow discharge mass spectrometry was used to detect the purity of the target blank, and the results showed a purity > 4N, with no other impurities introduced. SEM results are shown below. Figure 4 As shown, the grain size is <40μm, and the elemental composition is shown in Table 2 below:

[0063] Table 2. Elemental analysis of impurity materials prepared in Example 2

[0064] element Fe Cu Si Ca Mg Ni C N O Result in ppm 14 3.9 5.3 8 2.1 3.4 55 1.8 380

[0065] The target preform prepared in Comparative Example 3 was subjected to water immersion ultrasonic C-scan. Figure 5As shown, the defect rate of the target blank is 0.15%. SEM results show a grain size of approximately 80 μm. Figure 6 As shown, this indicates that without a high-temperature preliminary densification step, the density of the target blank edge is poor, while gradient sintering can refine the grains.

[0066] These results demonstrate that the scandium-germanium alloy target prepared by the process provided in this scheme has low oxygen content, low metal impurity content, and a target blank defect rate as low as 0.05%.

[0067] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, any improvements and modifications obtained without departing from the technical concept of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-oxygen, fine-grained aluminum-scandium-germanium alloy target, characterized in that, Includes the following steps: S1. Preparation of raw materials: The proportion of high-purity aluminum powder is 70% to 97%, with a purity greater than 5N; the proportion of scandium hydride powder is 2% to 20%, with a purity greater than 3N5; the proportion of germanium powder is 1% to 10%, with a purity greater than 5N. The powders are mixed evenly using a powder mixer under inert gas protection or vacuum environment. S2. Cold isostatic pressing: The powder mixed evenly in step S1 is loaded into a stainless steel mold and pre-pressed using a hydraulic press. After pressing, the mold is removed and then pre-formed using a cold isostatic press. After cold isostatic pressing, the target material is sprayed with an alumina coating. Then, a carbon steel / stainless steel sheath is made and welded. After welding, dehydrogenation, deoxygenation and degassing are promoted at 700-800℃ to obtain an ingot. S3. Hot Isostatic Pressing Gradient Sintering: The ingot after S2 welding is placed in a hot isostatic press for gradient sintering. After pre-sintering, it is held at a temperature of 650-850℃ and a pressure of 120-140MPa for 1-5 minutes. Then, argon is injected into the hot isostatic press furnace for rapid cooling at a rate of 10-15℃ / min. The final sintering temperature is 500-650℃ and the pressure is 140-170MPa. The temperature and pressure are held for 3-6 hours. After the temperature and pressure holding stage, the temperature and pressure are simultaneously reduced at a rate of 5-10℃ / min. After hot pressing, the carbon steel / stainless steel casing of the target material is removed by turning to obtain an aluminum scandium-germanium target blank. After finishing the target blank, the final target material is obtained.

2. The preparation method according to claim 1, characterized in that, The particle size of aluminum powder, scandium hydride powder and germanium powder in S1 is <50μm.

3. The preparation method according to claim 1, characterized in that, The mixing time in S1 is 25-30 minutes.

4. The preparation method according to claim 1, characterized in that, The pressure of the S2 intermediate cooling isostatic press is 80-100 MPa, and the pressure holding time is 15-30 seconds.

5. The preparation method according to claim 1, characterized in that, The thickness of the alumina coating in S2 is 0.5-1 mm.

6. The preparation method according to claim 1, characterized in that, The hot isostatic press has a double-layer water-cooled furnace shell channel on its outer wall.

7. A low-oxygen fine-grained aluminum-scandium-germanium alloy target material prepared by the preparation method according to any one of claims 1-6.

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