Low-oxygen fine-grain aluminum-scandium-germanium alloy target material and preparation method thereof

Abstract

The invention provides a low-oxygen fine-grain aluminum-scandium-germanium alloy target and a preparation method thereof, and belongs to the technical field of metal and alloy target processing and preparation.The low-oxygen fine-grain aluminum-scandium-germanium alloy target is characterized in that high-purity aluminum powder, scandium hydride powder and germanium powder are homogenized through a powder mixer to obtain mixed powder, the scandium hydride powder plays a role of an oxygen consumption agent and is decomposed at the temperature of 700-800 DEG C to generate H2, the H2 has high permeability, and the germanium content is reduced; diffusion can be carried out along metal particle crystal boundaries, and surface and internal oxide layers are synchronously removed, so that the oxygen content is reduced; after the high-purity metal germanium powder is doped, the strength and the toughness of the aluminum-scandium alloy can be enhanced, germanium can form a compound with aluminum and scandium, solid solution is further carried out, and therefore the strength, the electrical conductivity and the like of the alloy are improved, and the forgeability and the corrosion resistance of the alloy are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of processing and preparation of metal and alloy targets, and particularly relates to a low-oxygen fine-grained aluminum scandium germanium alloy target and a preparation method thereof. Background Art

[0002] High-purity aluminum sputtering targets are very popular in various industries. In the semiconductor field, high-purity aluminum targets are used for thin film deposition. In addition to the semiconductor industry, 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. The aluminum targets prepared by the existing technology have large grain sizes, poor processing performance and corrosion resistance, and need to refine the grains and improve the density through a forging-rolling process.

[0003] Aluminum scandium alloy targets have advantages such as good corrosion resistance, thermal stability, and low resistivity. Sputtering high-purity AlScN thin films with aluminum scandium alloy targets has excellent piezoelectric properties and is the core material for manufacturing filter chips, MEMS sensors, actuators, microphones, and energy harvesters. Since the solubility of scandium in aluminum is extremely low, with the increase of the scandium content, a large amount of brittle intermetallic alloys exist in the alloy system. There are still technical problems such as easy cracking, segregation, and oxidation in the preparation of high-scandium-content aluminum scandium alloy targets by the existing process methods.

[0004] However, after doping high-purity metal germanium into low-scandium-content aluminum scandium alloys, the strength and toughness of the aluminum scandium alloys can be enhanced. The atomic size difference between germanium and aluminum leads to lattice distortion, forming solid solution strengthening and avoiding the generation of brittle intermediate alloys. Germanium and scandium form composite precipitation phases, pinning grain boundaries and refining grains, thereby improving the strength of the alloy, its forgeability and corrosion resistance. Aluminum scandium alloys doped with high-purity germanium have better thermal conductivity and electrical conductivity than pure aluminum and high-scandium-content aluminum scandium alloys, and can replace pure aluminum targets, aluminum scandium alloy targets, etc. With the increasing demand in fields such as microelectronics, optoelectronics, and magnetic storage, especially the rise of the new generation of 5G communication technology and cloud computing technology, the market demand for targets is increasing continuously, and the application prospect of aluminum scandium germanium alloy targets is very broad, with great market potential. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a low-oxygen fine-grained aluminum scandium germanium alloy target and a preparation method thereof. The high-purity aluminum powder, scandium hydride powder, and germanium powder are homogenized by a powder mixer to obtain a mixed powder. The scandium hydride powder acts as an oxygen-consuming agent, which decomposes to produce H2 between 700-800 °C. H2 has strong permeability and can diffuse along the grain boundaries of metal particles to synchronously remove the surface and internal oxide layers, thereby reducing the oxygen content.

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

[0007] S1. Preparation of raw materials: high-purity aluminum powder is mixed in a ratio of 70% to 97% with a purity greater than 5N, scandium hydride powder is mixed in a ratio of 2% to 20% with a purity greater than 3N5, germanium powder is mixed in a ratio of 1% to 10% with a purity greater than 5N, and the obtained powders are mixed uniformly 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, pre-pressed by a hydraulic press, demolded after pressing, and then pre-formed by a cold isostatic press. After cold isostatic pressing, the target material is sprayed with an alumina coating, and then a carbon steel / stainless steel sheath is made. After welding, dehydrogenation, deoxidation and degassing are promoted at 700-800°C 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 warm for initial densification, and then it is quickly cooled down by argon flushing and pressure pressing in the hot isostatic press furnace. The cooling rate is 10-15℃ / min. The final sintering temperature is 500-650℃, the pressure is 140-170MPa, and the heat preservation and pressure maintenance are 3-6h. After the heat preservation and pressure maintenance stage is over, the temperature and pressure are reduced at the same time, and the cooling rate is 5-10℃ / min. After hot pressing, the target material sheath is removed by turning to obtain an aluminum-scandium-germanium target blank. The alumina coating on the surface of the target blank can be removed by fine machining, which indirectly improves the yield rate, that is, the coating material is the machining allowance of fine machining.

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

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

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

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

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

[0015] Preferably, the outer wall of the hot isostatic press is provided with a double-layer water-cooled furnace shell channel.

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

[0017] The mechanism of preparing low-oxygen aluminum scandium germanium target in this scheme:

[0018] In this solution, high-purity aluminum powder, scandium hydride powder, and germanium powder are homogenized by a powder mixer to obtain a mixed powder. The scandium hydride powder acts as an oxygen-consuming agent, which decomposes to produce H2 between 700 - 800 °C. H2 has strong permeability and can diffuse along the grain boundaries of metal particles to synchronously remove the surface and internal oxide layers, thereby reducing the oxygen content. After doping with high-purity metal germanium powder, the strength and toughness of the aluminum-scandium alloy can be enhanced. Germanium can form compounds with aluminum and scandium and further undergo solid solution, thereby improving the strength, electrical conductivity, etc. of the alloy, and enhancing the forgeability and corrosion resistance of the alloy. Since metals such as aluminum and germanium and the cladding material are prone to atomic diffusion to form brittle phases, exacerbating the brittleness of the target, the alumina coating on the surface of the target effectively blocks the connection between the cladding and the target, thereby improving the quality and yield of the target.

[0019] The cooling method of a conventional hot isostatic pressing furnace is furnace cooling. In this solution, a double-layer water-cooled furnace shell channel is provided on the outer wall of the hot isostatic pressing furnace, and rapid cooling is achieved by flushing argon and increasing the pressure to strengthen convection. The mass transfer between powder particles and pore elimination are accelerated at high temperatures, improving the density and uniformity of the target, and rapid cooling and hot isostatic pressing sintering can effectively inhibit grain coarsening at high temperatures.

[0020] Secondly, the sintering temperature used in this solution is slightly higher than the recrystallization temperature of the aluminum-based alloy, which is beneficial to grain boundary migration and atomic diffusion, but lower than the initial melting temperature, preventing the aluminum matrix from being overly softened or melted, and promoting the diffusion and uniform distribution of alloying elements, ensuring that the material is in the dominant stage of plastic deformation during the densification process, effectively promoting the plastic flow and interface diffusion of powder particles, accelerating pore closure, and increasing the density to approach the theoretical value. The uniform distribution of scandium and germanium optimizes the solid solution strengthening effect, enhances the grain boundary bonding strength at the same time, reduces stress concentration, and improves the creep resistance.

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

[0022] (1) When producing aluminum-scandium alloy targets by the existing casting method, there are problems such as ingot composition segregation, high crack defects, and low yield. Especially when preparing aluminum-scandium alloy targets with a high scandium content, it is difficult to form the target. Due to brittle intermetallic compounds, it is difficult to form and process the target. In the traditional powder metallurgy process, metal powders are prone to oxidation during processing and are not easy to perform impurity removal and deoxidation treatment. It is necessary to strictly control the oxygen content. At the same time, it is difficult to ensure the density of the target, and high-quality targets cannot be provided. In this solution, the scandium hydride powder is used as an oxygen-consuming agent, which decomposes to produce H2 between 700 - 800 °C. H2 has strong permeability and can diffuse along the grain boundaries of metal particles to synchronously remove the surface and internal oxide layers, thereby reducing the oxygen content.

[0023] (2) Since atomic diffusion easily occurs between metallic aluminum, germanium and the cladding material to form brittle phases, exacerbating the brittleness of the target, the alumina coating on the target surface effectively blocks the connection between the cladding and the target, thereby improving the quality and yield rate of the target.

[0024] (3) The cooling method of a conventional hot isostatic pressing furnace is furnace cooling. In this solution, a double-layer water-cooled furnace shell channel is provided on the outer wall of the hot isostatic pressing furnace, and rapid cooling is achieved by flushing argon and boosting pressure to enhance convection. The mass transfer between powder particles and pore elimination are accelerated at high temperatures, improving the density and uniformity of the target, and rapid cooling and hot isostatic pressing sintering can effectively inhibit grain coarsening at high temperatures.

[0025] (4) The aluminum scandium germanium alloy target prepared by the hot isostatic pressing process in this solution simultaneously achieves density and refined grains, without the need for further heat treatment, simplifying the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is the ultrasonic C-scan diagram of the target prepared in Example 1 of Experimental Example 1;

[0028] Figure 2 It is the SEM diagram of the target prepared in Example 1 of Experimental Example 1;

[0029] Figure 3 It is the ultrasonic C-scan diagram of the target prepared in Example 2 of Experimental Example 1;

[0030] Figure 4 It is the SEM diagram of the target prepared in Example 2 of Experimental Example 1;

[0031] Figure 5 It is the water immersion ultrasonic C diagram of the aluminum scandium germanium alloy target blank in Comparative Example 3;

[0032] Figure 6 It is the SEM diagram of the aluminum scandium germanium alloy target blank in Comparative Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail in conjunction with the drawings and specific embodiments.

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

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

[0036] Example 1

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

[0038] S1. Preparation of raw materials: Weigh 900 g of high-purity aluminum powder, 50 g of scandium hydride powder, and 50 g of germanium powder. The powder particle size is all <50 μm. Use a multi-dimensional mixer to mix the materials. After mixing for 30 minutes, a mixed powder is obtained. Load the mixed raw material powder into a stainless steel mold. The mold is cleaned to avoid contaminating the raw materials.

[0039] S2. Cold isostatic pressing forming: Pre-press with a hydraulic press, demold after pressing is completed, and then press into shape with a cold isostatic press. The cold isostatic pressure is 90 Mpa, and the pressure holding time is 15 s. Spray alumina particles on the surface of the target to form a 0.5 mm thick coating. Finally, place the target blank in a stainless steel jacket and weld it. Heat up to 700 °C to start degassing for 1 hour.

[0040] S3. Hot isostatic pressing gradient sintering: Place the degassed jacket in a stainless steel tray of a hot isostatic pressing equipment for cold-state pressurized sintering. First, pre-charge pressure, with argon as the medium, and the pre-charged argon is set at 80 Mpa. After the argon charging is completed, start heating up, set at 700 °C, and hold for 5 minutes at 130 MPa for pretreatment. After the pretreatment, charge argon into the furnace and increase the pressure to accelerate the furnace cooling. When the furnace temperature drops to 550 °C, the cooling rate is 14 °C / min. At this time, the furnace pressure is 170 Mpa, and heat isostatic pressing treatment is carried out for 3 hours with heat preservation and pressure holding. The heat preservation temperature difference is ±1 °C, and the pressure holding pressure difference is ±0.5 MPa. After the heat preservation and pressure holding are completed, cool down at 5 °C / min. The aluminum scandium germanium alloy target jacket after hot isostatic pressing is removed by turning to obtain an aluminum scandium germanium alloy target blank with a target blank size of 200 mm × 10 mm.

[0041] Example 2

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

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

[0044] S2. Cold isostatic pressing: pre-pressing with hydraulic press, demoulding after pressing, and then pressing with cold isostatic press, the cold isostatic pressure is 100Mpa, and the holding time is 30s. Alumina particles are sprayed on the surface of the target to form a 1mm thick coating, and finally the target blank is placed in a stainless steel sleeve for welding, and the temperature is raised to 800℃ to start degassing, which lasts for 0.5h.

[0045] S3, hot isostatic pressing gradient sintering: Place the degassed package in the stainless steel tray of the hot isostatic pressing equipment for cold pressurized sintering. Pre-pressurize first, the medium is argon, and the pre-filling argon is set to 70Mpa. After the argon filling is completed, the temperature begins to rise, set to 800℃, 135MPa, and keep warm for 3min pretreatment. After the pretreatment is completed, argon is flushed into the furnace to pressurize and accelerate the cooling in the furnace. The furnace temperature drops to 600℃, and the cooling rate is 12℃ / min. At this time, the furnace pressure is 160Mpa, and the heat preservation and pressure are maintained for 4h for hot isostatic pressing treatment. The insulation temperature difference is ±1℃, and the pressure difference is ±0.5MPa. After the insulation and pressure are completed, the temperature is reduced by 5℃ / min. The aluminum-scandium-germanium alloy target package after hot isostatic pressing is removed by turning to obtain an aluminum-scandium-germanium alloy target blank with a target blank size of 150mm×18mm.

[0046] Comparative Example 1

[0047] The hydrogenated scandium powder was replaced with pure scandium powder, and the remaining steps were the same as in Example 1.

[0048] After removing the jacket, the target blank was sampled for oxygen content testing, and the O content was 2577ppm, which shows that scandium hydride as a deoxidizer can effectively reduce the O content of the target material, while pure metal powder introduces O during the powder making process, thereby increasing the O content of the target material.

[0049] Comparative Example 2

[0050] The aluminum oxide layer is not sprayed, and the remaining steps are the same as in Example 1.

[0051] After removing the sheath, samples were taken from the target blank surface for iron content testing, and the iron content was 2213 ppm, which shows that the alumina coating can effectively block the diffusion between Fe atoms in the sheath material and metal atoms in the target material. Failure to spray the alumina layer increases the processing loss of the target material and reduces the yield rate.

[0052] Comparative Example 3

[0053] Preparation of Aluminum-ScGe Alloy Target 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, with a powder particle size of <50μm, use a multidimensional mixer to mix the materials, and obtain a mixed powder after mixing for 30 minutes. Put the mixed raw material powder into a stainless steel mold, and clean the mold to avoid contamination of the raw materials.

[0055] S2. Cold Isostatic Pressing: Pre-press with a hydraulic press, demold after pressing, and then press and form with a cold isostatic press. The cold isostatic pressure is 90 Mpa, and the pressure holding time is 15 s. Spray alumina particles on the surface of the target to form a 0.5 mm thick coating. Finally, place the target blank in a stainless steel sheath and weld it. Heat up to 700 °C to start degassing for 1 h.

[0056] S3. Hot Isostatic Pressing with Gradient Sintering: Place the degassed sheath in a stainless steel tray of a hot isostatic pressing equipment for cold-state pressure boosting and sintering. First, pre-charge pressure with argon as the medium, and set the pre-charge argon to 80 Mpa. After the argon charging is completed, start heating up, set to 650 °C, 130 MPa, keep the temperature and pressure for 3 h for hot isostatic pressing treatment. After the temperature and pressure holding are completed, cool down at a rate of 5 °C / min. Remove the sheath of the scandium-aluminum-germanium alloy target after hot isostatic pressing by turning processing to obtain the scandium-aluminum-germanium alloy target blank.

[0057] Experimental Example 1

[0058] Investigate the characteristics of the targets prepared in the examples

[0059] Perform water immersion ultrasonic C-scan on the target blank finished product prepared in Example 1 as Figure 1 , and the defect rate of the target blank is 0.05%. Subsequently, randomly sample the target blank, analyze the oxygen content of the target blank with an oxygen-nitrogen-hydrogen analyzer, and the result shows that the oxygen content is 256 ppm. Detect the purity of the target blank by glow discharge mass spectrometry, and the result shows that the purity > 4N, and no other impurities are introduced. The SEM result is as Figure 2 shown, showing that the grain size < 40 μm, and the element content is shown in Table 1 below:

[0060] Table 1 Analysis of impurity elements of the target prepared in Example 1

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

[0062] Perform water immersion ultrasonic C-scan on the paired target blank finished product prepared in Example 2 as Figure 3 shown, and the defect rate of the target blank is 0.08%. Subsequently, randomly sample the target blank finished product, analyze the oxygen content of the target blank with an oxygen-nitrogen-hydrogen analyzer, and the result shows that the oxygen content is 380 ppm. Detect the purity of the target blank by glow discharge mass spectrometry, and the result shows that the purity > 4N, and no other impurities are introduced. The SEM result is as Figure 4 shown, showing that the grain size < 40 μm, and the element content is shown in Table 2 below:

[0063] Table 2 Analysis of impurity elements of the target prepared in Example 2

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

[0065] Perform water immersion ultrasonic C-scan on the target blank finished product prepared in Comparative Example 3 as Figure 5As shown, the defect rate of the target blank is 0.15%. The SEM results show that the grain size is about 80 μm. The results are as Figure 6 shown, indicating that the preliminary high-temperature densification step was not carried out, the density of the edge of the target blank is poor, and at the same time, gradient sintering can refine the grains.

[0066] These results show that the scandium germanium alloy target prepared by the process provided by this solution has low oxygen content, low metal impurity content, and the defect rate of the target blank is as low as 0.05%.

[0067] The above is only the preferred embodiment of this invention patent, and the protection scope of this invention patent is not limited to the above embodiments. For those skilled in the art, the improvements and transformations obtained without departing from the technical concept of this invention patent should also be regarded as the protection scope of this invention patent.

Claims

1. A preparation method of a hypoxic fine-grained aluminum scandium germanium alloy target, characterized in that, It includes the following steps: S1. Preparation of raw materials: The proportion of high-purity aluminum powder is 70% - 97%, the purity is greater than 5N, the proportion of scandium hydride powder is 2% - 20%, the purity of scandium hydride powder is greater than 3N5, the proportion of germanium powder is 1% - 10%, the purity is greater than 5N. Under the protection of inert gas or in a vacuum environment, the prepared powders are mixed evenly by a powder mixer; S2. Cold isostatic pressing forming: The powders evenly mixed in step S1 are loaded into a stainless-steel mold, pre-pressed by a hydraulic press, demolded after pressing, and then pre-formed by a cold isostatic press. After cold isostatic pressing forming, an alumina coating is sprayed on the target, and then a carbon steel / stainless-steel cladding is made. After welding, dehydrogenation, deoxidation, and degassing are promoted at 700 - 800 °C to obtain an ingot blank; S3. Hot isostatic pressing gradient sintering: The ingot blank after welding in S2 is placed in a hot isostatic press for gradient sintering. After pre-sintering, it is kept warm for preliminary densification, and then argon is flushed into the hot isostatic press furnace and pressurized to rapidly cool down, with a cooling rate of 10 - 15 °C / min. The final sintering temperature is 500 - 650 °C, the pressure is 140 - 170 MPa, and it is kept warm and pressurized for 3 - 6 h. After the end of the heat preservation and pressure holding stage, the temperature and pressure are reduced simultaneously, with a cooling rate of 5 - 10 °C / min. After hot pressing, the carbon steel / stainless-steel cladding of the target is removed by turning to obtain an aluminum scandium germanium target blank. After fine machining of the target blank, the final target product is obtained.

2. The preparation method according to claim 1, wherein In S1, the powder particle size of the aluminum powder, scandium hydride powder, and germanium powder < 50 μm.

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

4. The preparation method according to claim 1, characterized in that In S2, the pressure of the cold isostatic press is 80 - 100 Mpa, and the pressure holding time is 15 - 30 s.

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

6. The preparation method according to claim 1, characterized in that, In S3, the pre-sintering temperature is 650 - 850 °C, the pre-sintering pressure is 120 - 140 MPa, and the heat preservation time is 1 - 5 min.

7. The preparation method according to claim 1, wherein The outer wall of the hot isostatic press is provided with a double-layer water-cooled furnace shell channel.

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

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