Method for preparing and recycling high-purity tungsten target material

Abstract

The invention belongs to the technical field of magnetron sputtering target material manufacturing, and discloses a method for preparing and recycling a high-purity tungsten target material. According to the preparation and recovery method, used tungsten residual targets serve as raw materials, primary tungsten powder is obtained after mechanical crushing and ball milling, after crushing and ball milling, the primary tungsten powder reacts with fluorine gas at the high temperature to obtain low-purity tungsten hexafluoride with the purity of 2-4 N, and secondary tungsten powder with the purity larger than or equal to 7 N, the O content smaller than or equal to 300 ppm, impurity elements Fe, Ni, Cr, K and Mo smaller than or equal to 0.01 ppm and the average particle size smaller than or equal to 3 micrometers is obtained in a CVD deposition mode. And high-purity tungsten and tungsten alloy target materials can be prepared again by taking the tungsten powder as a raw material.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetron sputtering target material manufacturing, and in particular relates to a method for preparing and recycling a high-purity tungsten target material. Background Art

[0002] Tungsten target has high melting point (3410℃), high density (19.3g / cm 3 ), high thermal conductivity (165W / (m∙K)), high strength, low expansion coefficient (4.6×10 -6 mm -1 ), high corrosion resistance, and other properties, making it widely used in the manufacturing of advanced memory devices. Recent research has shown that tungsten is expected to replace copper as an interconnect material. High-purity tungsten targets are key materials for memory device manufacturing, and their annual consumption is very large. However, after sputtering high-purity tungsten targets using physical vapor deposition (PVD) methods, sputtering tracks with varying sputtering depths are produced due to magnetic field uniformity issues. When the depth of one sputtering track approaches the target thickness, the target becomes unusable. At this point, the target utilization rate reaches less than 30%, and the remaining 70% or more of the high-purity tungsten residual targets are unusable.

[0003] Since the melting point of high-purity tungsten targets is very high, high-purity tungsten powder is required as the raw material for preparation and sintering. However, high-purity tungsten powder is usually obtained by calcining and reducing high-purity ammonium paratungstate APT as the raw material. The high-purity tungsten powder currently prepared by chemical methods is limited by the low purity of the APT raw material. The current tungsten resources, high-quality and high-grade tungsten concentrates are becoming increasingly scarce. The various impurities in tungsten concentrates, especially molybdenum, potassium, iron, and chromium, are all high in content and cannot be removed in the process of preparing high-purity tungsten powder. The Fe, Ni, Cr, K, and Mo impurity element contents of the prepared high-purity tungsten powder are all ≥0.1ppm, and the Mo impurity element content reaches more than 1ppm. If high-purity tungsten residual target blocks are used as raw materials to prepare high-purity tungsten powder, impurities such as Fe, Ni, and Cr are easily introduced during the crushing process. The purity of the final prepared tungsten powder is ≤2N, which cannot meet the purity requirements of high-purity tungsten targets.

[0004] Therefore, the current high-purity tungsten residual target can only be used as a low-purity industrial additive and added to molten steel. Its utilization value is extremely low. How to recycle high-purity tungsten target materials for high value is the current difficulty. Summary of the Invention

[0005] In response to the problems mentioned in the prior art, this patent provides a method for preparing and recycling high-purity tungsten targets: the present invention belongs to the field of magnetron sputtering target manufacturing technology, and discloses a method for preparing and recycling high-purity tungsten targets. The preparation and recycling method uses used high-purity tungsten residual targets as raw materials, obtains tungsten powder after mechanical crushing and ball milling, and reacts the tungsten powder obtained after crushing and ball milling with fluorine gas at high temperature to obtain low-purity tungsten hexafluoride with a purity of 2N~4N. CVD deposition is then used to obtain high-purity tungsten powder with a purity of ≥7N, an O content of ≤300ppm, impurity elements Fe, Ni, Cr, K, Mo ≤0.01ppm, and an average particle size of ≤3μm. High-purity tungsten powder can be used as raw material to prepare high-purity tungsten and tungsten alloy targets again.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing a high-purity tungsten target material using a tungsten target residue, the steps of which are as follows: 1) Grinding to obtain primary tungsten powder (i.e., low-purity tungsten powder); In the step 1), the particle size of the primary tungsten powder is 1-20 μm; 2) Use a fixed bed reactor to react the primary tungsten powder with fluorine gas to obtain low-purity tungsten hexafluoride; In the step 2), the purity of the low-purity tungsten hexafluoride is 2N~4N; 3) Using the low-purity tungsten hexafluoride obtained in step 2) and hydrogen as raw materials, deposition is performed in a chemical vapor deposition (CVD) device to ultimately obtain secondary tungsten powder (i.e., high-purity tungsten powder); 4) Sintering the secondary tungsten powder obtained in step 3) to prepare a finished tungsten target; In the step 4), the purity of the finished tungsten target material is ≥6N, preferably ≥7N, and more preferably ≥7N6.

[0007] In some preferred embodiments, in step 3), the purity of the secondary tungsten powder is ≥7N, the O content is ≤300ppm, the impurity elements Fe, Ni, Cr, K, and Mo are all ≤0.01ppm, and the average particle size is ≤3μm.

[0008] In some preferred embodiments, in step 2), the temperature of the fixed bed reactor is 200-400° C.; and / or The pressure of the fixed bed reactor is 0.1~0.5MPa.

[0009] In some preferred embodiments, in step 2), the ratio of primary tungsten powder to fluorine gas is 1:3 to 1:5; and / or The flow rate is 0.5~1.5L / min.

[0010] In some preferred embodiments, in step 3), the temperature of the reactor in the chemical vapor deposition (CVD) equipment is 900-1000° C.; and / or The pressure of the reactor in the chemical vapor deposition (CVD) equipment is 0.5~1.5atm.

[0011] In some preferred embodiments, in step 4), the flow rate of the secondary tungsten hexafluoride is 15-20 g / min; and / or The flow rate of hydrogen was 2-2.5 L / min.

[0012] In some preferred embodiments, in step 1), the crushed raw material is a tungsten target residue, preferably a recycled tungsten target; more preferably a tungsten target residue with a purity of ≥5N; In the step 1), the pulverization method is any one of the following or a combination of at least two: cutting, mechanical crushing, and ball milling; preferably, the cutting is any one of the following or a combination of at least two: wire cutting, water jet cutting, and laser cutting.

[0013] In some preferred embodiments, in step 1), the crushing method steps are as follows: 1-1) Prepare tungsten target with purity ≥5N and cut it into pieces with size ≤20*20mm by wire cutting, water cutting or laser cutting, preferably with area ≤400mm 2 , more preferably the side length of the fragments is ≤20mm; then mechanically crushed into small fragments of size ≤3*3mm, preferably with an area of ≤9mm 2 More preferably, the side lengths of the small fragments are all ≤3 mm; 1-2) The crushed tungsten fragments are prepared into primary tungsten powder with a particle size of 1-20 μm by ball milling. The ball milling speed is 50-200 r / min and the ball milling time is 2-10 h.

[0014] In some preferred embodiments, in step 3), the impurity elements are selected from any one or a combination of at least two of the following: Fe, Ni, Cr, K, Mo, O; preferably, Fe, Ni, Cr and other impurities introduced during the crushing and ball milling of the tungsten target residue.

[0015] The present invention also provides a high-purity tungsten target prepared by the preparation method, wherein the purity is ≥6N, preferably ≥7N; More preferably, the content of impurity elements including but not limited to Fe, Ni, Cr, K, and Mo is ≤0.01 ppm; Its O content is ≤300ppm.

[0016] The beneficial effect of the present application is at least that high-purity tungsten target materials can be recycled at high value: the present technology uses used tungsten residual targets as raw materials, prepares high-purity tungsten powder (i.e., secondary tungsten powder), and then reuses it to prepare high-purity tungsten target materials again, which has high utilization value.

[0017] The prepared high-purity tungsten powder (i.e., secondary tungsten powder) has higher purity: the purity of the high-purity tungsten powder prepared by this patent using tungsten residual target as raw material can reach 7N (i.e., 99.99999%) or above, and the purity of the finished target material can be as high as 7N6 (i.e., 99.999996%) or above.

[0018] Impurities introduced during the crushing process can be removed, and the prepared high-purity tungsten powder has lower impurity elements: This patent adopts CVD to prepare high-purity tungsten powder. The difference in vapor pressure between tungsten and impurity elements can be used to remove such impurities during the preparation of tungsten hexafluoride and CVD deposition. The final content of impurity elements such as Fe, Ni, Cr, K, Mo, etc. is ≤0.01ppm.

[0019] No need for high-purity tungsten hexafluoride deposition: The present invention only requires low-purity tungsten hexafluoride when preparing tungsten hexafluoride, eliminating the need for distillation and purification to obtain high-purity tungsten hexafluoride with a purity of 6N or above for subsequent CVD deposition. During the subsequent CVD deposition of tungsten powder, impurities such as Fe, Ni, and Cr introduced during the ball milling process are removed through high-temperature reactions, achieving the same effect as obtaining high-purity W powder by depositing high-purity tungsten hexafluoride.

[0020] The present invention ensures the yield of the deposition process by adjusting the relationship between the CVD deposition temperature and the gas flow rate and pressure, and the yield can reach more than 80-90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart for the recycling of high-purity tungsten targets. DETAILED DESCRIPTION

[0022] The following is attached Figure 1 The present invention is further described with specific embodiments, but is not intended to limit the scope of protection of the present invention.

[0023] The inventive mechanism of this invention is as follows: Used high-purity tungsten target remnants (purity ≥5N) are used as raw materials, mechanically crushed and ball-milled to obtain tungsten powder. The primary tungsten powder obtained after crushing and ball milling reacts with fluorine gas at high temperature to obtain low-purity tungsten hexafluoride. This reaction is then carried out using CVD deposition to obtain secondary tungsten powder with a purity ≥7N, an O content ≤300ppm, impurity elements Fe, Ni, Cr, K, and Mo ≤0.01ppm, and an average particle size ≤3μm. This secondary tungsten powder can then be used as raw material to prepare high-purity tungsten and tungsten alloy finished targets. To better explain the present invention and facilitate understanding, the invention is described in detail below using specific implementation examples and comparative examples.

[0024] Examples 1 to 16, target residue cutting: prepare high-purity tungsten target residue with purity ≥5N, cut it into pieces with a size of 10*10mm by wire cutting, water cutting or laser cutting, and then use mechanical crushing to crush it into small pieces with a size of 2*2mm.

[0025] Ball milling: The crushed tungsten fragments were prepared into primary tungsten powder (i.e., low-purity tungsten powder) with a particle size of 3 μm by ball milling. The ball milling speed was 100 r / min and the ball milling time was 5 h.

[0026] Preparation of low-purity tungsten hexafluoride: Using the obtained primary tungsten powder as raw material, a fixed bed reactor is used to react the primary tungsten powder with fluorine gas to obtain low-purity tungsten hexafluoride with a purity of 2N-4N, wherein the temperature of the fixed bed reactor is 200-400℃ and the pressure is 0.1-0.5MPa.

[0027] Chemical Vapor Deposition (CVD): Using low-purity tungsten hexafluoride and hydrogen as raw materials, deposition is performed in a CVD device to obtain high-purity tungsten powder (i.e., secondary tungsten powder) with a purity of ≥7N, an O content of ≤300ppm, impurity levels of Fe, Ni, Cr, K, and Mo ≤0.01ppm, and an average particle size of ≤3μm. The CVD reactor temperature is 900-1000°C, the pressure is 0.5-1.5atm, the flow rate of high-purity tungsten hexafluoride is 15-20g / min, and the flow rate of hydrogen is 2-2.5L / min.

[0028] Preparation of tungsten target: The obtained high-purity tungsten powder is sintered and then re-prepared to obtain a high-purity tungsten target with a purity of ≥6N (i.e., finished target).

[0029] The target material parameters and target material properties prepared in Examples 1 to 16 are shown in Table 1.

[0030] Comparative Example 1, target residue cutting: prepare a high-purity tungsten target residue with a purity of ≥5N, cut it into pieces with a size of 10*10mm by wire cutting, water cutting or laser cutting, and then use mechanical crushing to crush it into small pieces with a size of 2*2mm.

[0031] Ball milling: The crushed tungsten fragments were ball milled to a 3μm tungsten powder at a speed of 100 r / min for 5 hours. The resulting tungsten powder had a purity of 2N, an O content of 800 ppm, and impurity levels of Fe, Ni, and Cr ≥100 ppm, K ≥0.1 ppm, and Mo ≥5 ppm.

[0032] Preparation of tungsten target: The obtained tungsten powder is sintered to prepare a high-purity tungsten target with a purity of 1N8, an oxygen content of 460ppm, an average grain size of 34μm, a relative density of 99.9%, and impurity elements Fe, Ni, Cr ≥100ppm, K ≥0.1ppm, and Mo ≥5ppm.

[0033] Results Analysis: Comparison of Comparative Example 1 with the Example shows that Comparative Example 1 employs conventional methods for recovering high-purity tungsten targets, resulting in crushing and ball milling to obtain low-purity tungsten powder. Further sintering yields a target with a purity of only 1N8, failing to meet the requirements for high-purity targets (purity ≥ 7N). In contrast, the Example can prepare high-purity tungsten target residues into high-purity tungsten powder, which can then be reused to prepare high-purity tungsten targets, demonstrating high utilization value.

[0034] Comparative Example 2, 1. Classification pretreatment: High-purity ammonium paratungstate APT was used as raw material and subjected to airflow classification pretreatment with a classification wheel frequency of 6 Hz.

[0035] 2. Calcination: Calcinate at 480℃ for 2h, 850℃ for 1.5h, and then sieve to obtain high-purity WO 3。

[0036] 3. Preparation of high-purity tungsten powder: Using the prepared high-purity WO3 as raw material, high-purity hydrogen was introduced into the reduction at 950°C for 6 hours, and then sieved to obtain high-purity tungsten powder with a purity of 5N, an O content of 700ppm, impurity elements Fe, Ni, Cr, K ≥ 0.1ppm, a Mo impurity content of 1.7ppm, and an average particle size of 1.8μm.

[0037] 4. Preparation of tungsten target: The obtained tungsten powder is sintered to prepare a high-purity tungsten target with a purity of 4N9, an oxygen content of 320ppm, an average grain size of 12μm, a relative density of 99.9%, impurity elements Fe, Ni, Cr, K ≥ 0.1ppm, and a Mo impurity content of 1.7ppm.

[0038] Results Analysis: Comparison of Comparative Example 2 with the Example shows that Comparative Example 2, a conventional commercial chemical method for preparing high-purity tungsten powder, ultimately only produces high-purity tungsten powder with a purity of less than 5N. The powder also contains high levels of oxygen, Fe, Ni, Cr, K, Mo, and other impurities, exceeding 10 times that of the Example. Furthermore, the oxygen content is approximately 4 times that of Example 1, demonstrating a significant difference in performance. The high-purity tungsten powder prepared by the CVD method in the Example achieves a purity of over 7N. Furthermore, the vapor pressure difference between tungsten and impurity elements can be utilized to remove such impurities during the preparation of tungsten hexafluoride, distillation, and CVD deposition processes. Ultimately, the impurity elements Fe, Ni, Cr, K, and Mo are ≤0.01ppm.

[0039] Comparative Example 3, 1. Prepare raw materials: prepare low-purity tungsten hexafluoride (purity 4N) as raw material.

[0040] 2. Preparation of high-purity tungsten target: Deposition is performed in a CVD device using copper as the substrate. The resulting target has a purity of 5N7, an oxygen content of 12 ppm, an average grain size of 150 μm, a relative density of 99.9%, and impurity levels of Fe, Ni, Cr, K, and Mo ≥ 0.1 ppm. The CVD reactor temperature is 550°C, the pressure is 1 atm, the flow rate of high-purity tungsten hexafluoride is 0.5 g / min, and the flow rate of hydrogen is 1 L / min.

[0041] Results Analysis: Comparative Example 3 employed conventional methods for CVD deposition onto a copper substrate. Comparative Example 3 employed the same low-purity tungsten hexafluoride (purity 2N-4N) as the Examples of this application. Compared with the Examples, the tungsten target material obtained by direct CVD deposition using low-purity tungsten hexafluoride as a raw material in Comparative Example 3 exhibited a target purity of 5N7, an oxygen content of 12 ppm, impurity contents of Fe, Ni, Cr, K, and Mo of ≥0.1 ppm, and an average grain size of 150 μm. In contrast, the Examples utilized recycled, post-consumer high-purity tungsten targets to obtain low-purity tungsten hexafluoride (purity 2N-4N). After CVD deposition using low-purity tungsten hexafluoride, high-purity tungsten powder is obtained again, and the high-purity tungsten powder is sintered to obtain the final high-purity tungsten target. The purity of the high-purity tungsten target obtained in the embodiment can reach more than 7N, and the oxygen content, Fe, Ni, Cr, K, Mo and other impurity element contents are much lower than those in comparative example 3. The average grain size of the high-purity tungsten target obtained using the embodiment is 11-34μm, which is also much smaller than that in comparative example 3.

[0042] Comparative Example 4, 1. Prepare raw materials: prepare low-purity tungsten hexafluoride (purity 4N) as raw material.

[0043] 2. Preparation of high-purity tungsten metal: Deposition is performed in a CVD device using a copper substrate. The resulting target material has a purity of 5N7, an oxygen content of 12 ppm, an average grain size of 150 μm, a relative density of 99.9%, and impurities of Fe, Ni, Cr, K, and Mo ≥ 0.1 ppm. The CVD reactor temperature is 550°C, the pressure is 1 atm, the flow rate of high-purity tungsten hexafluoride is 0.5 g / min, and the flow rate of hydrogen is 1 L / min.

[0044] 3. Rolling: The tungsten billet obtained by CVD deposition is rolled at a heating temperature of 1500°C, a holding time of 30 min, three rolling passes, and a deformation of 10% per pass.

[0045] 4. Heat treatment: The rolled slab is recrystallized under vacuum at a temperature of 1200°C for 2 hours. The final product is a high-purity tungsten target with a purity of 5N7, an oxygen content of 12ppm, an average grain size of 90μm, a relative density of 99.9%, and impurity elements Fe, Ni, Cr, K, and Mo ≥ 0.1ppm.

[0046] Result analysis: Compared with Comparative Example 3, Comparative Example 4 adds the steps of rolling and heat treatment, and the average grain size of the target material finally obtained is reduced from 150μm to 90μm. The average grain size of the target material obtained in the embodiment is 11-34μm. Compared with the embodiment, the average grain size of the target material in Comparative Example 4 is still more than 3 times higher, and the effect difference is significant.

[0047] Example 17, target residue cutting: prepare high-purity tungsten target residue with purity ≥5N, cut it into pieces with a size of 10*10mm by wire cutting, water cutting or laser cutting, and then use mechanical crushing to crush it into small pieces with a size of 2*2mm.

[0048] Ball milling: The crushed tungsten fragments were prepared into tungsten powder with a particle size of 3 μm by ball milling. The ball milling speed was 100 r / min and the ball milling time was 5 h.

[0049] Preparation of tungsten hexafluoride: Using the obtained tungsten powder as raw material, a fixed bed reactor is used to react the tungsten powder with fluorine gas to obtain low-purity tungsten hexafluoride, wherein the temperature of the fixed bed reactor is 200°C and the pressure is 0.1 MPa.

[0050] Chemical Vapor Deposition (CVD): Using low-purity tungsten hexafluoride and hydrogen as raw materials, deposition is performed in a CVD device to obtain high-purity tungsten powder with a purity of 5N9, an O content of 400ppm, impurity contents of Fe, Ni, Cr, K, and Mo ≥0.1ppm, and an average particle size of 2.1μm. The CVD reactor temperature is 850°C, the pressure is 0.5atm, the flow rate of tungsten hexafluoride is 15g / min, and the flow rate of hydrogen is 2.5L / min.

[0051] Preparation of tungsten target: The obtained high-purity tungsten powder can be re-prepared after sintering to produce high-purity tungsten target with purity 5N, oxygen content 50ppm, average grain size 16μm, relative density 99.9%, and impurity elements Fe, Ni, Cr, K, and Mo content ≥0.1ppm.

[0052] Results Analysis: Both Examples 7 and 17 only produced low-purity tungsten hexafluoride during the preparation process, without undergoing distillation and purification to obtain tungsten hexafluoride with a purity of 6N or higher for subsequent CVD deposition. During the subsequent CVD deposition of tungsten powder, Example 7 used a high-temperature reaction to remove impurities such as Fe, Ni, and Cr introduced during the ball milling process, resulting in high-purity tungsten powder with a purity of 7N8 and an oxygen content of 180 ppm. In contrast, Example 17 used a low-temperature (below 900°C) CVD deposition process, which was unable to completely remove impurities such as Fe, Ni, and Cr introduced during the ball milling process. The resulting tungsten powder had an Fe, Ni, Cr, K, and Mo content of ≥0.1 ppm, a purity of 5N9, and an oxygen content of 350 ppm. The Fe, Ni, Cr, K, and Mo impurity content in this example was over 10 times that of the example, and the oxygen content was twice that of Example 7, demonstrating significant differences in performance.

[0053] The main manufacturing processes and performance results of Examples 1 to 16 are shown in Table 1.

[0054]

Claims

1. A method for preparing a high-purity tungsten target, comprising the following steps: 1) Crushing to obtain primary tungsten powder; In the step 1), the particle size of the primary tungsten powder is 1-20 μm; 2) Use a fixed bed reactor to react the primary tungsten powder with fluorine gas to obtain low-purity tungsten hexafluoride; In the step 2), the purity of the low-purity tungsten hexafluoride is 2N~4N; 3) Using the low-purity tungsten hexafluoride obtained in step 4) and hydrogen as raw materials, deposition is performed in a chemical vapor deposition (CVD) device to ultimately obtain secondary tungsten powder; 4) Sintering the secondary tungsten powder obtained in step 3) to prepare a finished tungsten target; In the step 4), the purity of the finished tungsten target material is ≥6N, or ≥7N, or ≥7N6.

2. The method for preparing a high-purity tungsten target according to claim 1, wherein: in, In the step 4), the purity of the secondary tungsten powder is ≥7N, the O content is ≤300ppm, the impurity elements Fe, Ni, Cr, K, and Mo are all ≤0.01ppm, and the average particle size is ≤3μm.

3. The method for preparing a high-purity tungsten target according to claim 1, wherein: in, In step 2), the temperature of the fixed bed reactor is 200-400° C.; and / or The pressure of the fixed bed reactor is 0.1~0.5MPa.

4. The method for preparing a high-purity tungsten target according to claim 1 or 3, characterized in that: in, In the step 2), the ratio of primary tungsten powder to fluorine gas is 1:3-1:5; and / or the flow rate is 0.5-1.5 L / min.

5. The method for preparing a high-purity tungsten target according to claim 1, wherein: in, In the step 3), the temperature of the reactor in the chemical vapor deposition (CVD) equipment is 900-1000° C.; and / or The pressure of the reactor in the chemical vapor deposition (CVD) equipment is 0.5~1.5atm.

6. The method for preparing a high-purity tungsten target according to claim 1 or 5, characterized in that: in, In step 3), the flow rate of low-purity tungsten hexafluoride is 15-20 g / min; and / or The flow rate of hydrogen is 2~2.5L / min.

7. The method for preparing a high-purity tungsten target according to claim 1, wherein: in, In the step 1), the raw material to be crushed is a tungsten target material or a tungsten target residue.

8. The method for preparing a high-purity tungsten target according to claim 7, wherein: in, In the step 1), the crushed raw material is recycled tungsten target material or tungsten residual target.

9. The method for preparing a high-purity tungsten target according to claim 7 or 8, characterized in that: in, In the step 1), the crushed raw material is a tungsten target material or a tungsten residual target with a purity of ≥5N.

10. The method for preparing a high-purity tungsten target according to claim 1, wherein: in, In the step 1), the pulverization method is any one of the following or a combination of at least two: cutting, mechanical crushing, and ball milling.

11. The method for preparing a high-purity tungsten target according to claim 10, characterized in that: in, The cutting is performed by any one of the following or a combination of at least two of them: wire cutting, water cutting, and laser cutting.

12. The method for preparing a high-purity tungsten target according to claim 1, wherein: in, In step 1), the crushing method steps are as follows: 1-1) Prepare tungsten target residue with purity ≥5N, cut it into pieces with size ≤20*20mm by wire cutting, water jet cutting or laser cutting, and then use mechanical crushing to break it into small pieces with size ≤3*3mm; 1-2) The crushed tungsten fragments are prepared into primary tungsten powder with a particle size of 1-20 μm by ball milling. The ball milling speed is 50-200 r / min and the ball milling time is 2-10 h.

13. The method for preparing a high-purity tungsten target according to claim 1, wherein: in, In step 3), the impurity elements are selected from any one or a combination of at least two of the following: Fe, Ni, Cr, K, Mo, and O.

14. A high-purity tungsten target prepared by the preparation method according to any one of claims 1 to 13, characterized in that: Its purity is ≥6N.

15. The high-purity tungsten target according to claim 14, characterized in that: Purity ≥7N.

16. The high-purity tungsten target according to claim 14, characterized in that: in, The content of impurity elements including but not limited to Fe, Ni, Cr, K, and Mo is ≤0.01ppm; Its O content is ≤300ppm.

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