Preparation method of ultra-high purity tungsten wire

Abstract

This application relates to the field of high-purity semiconductor materials, specifically to a method for preparing ultra-high purity tungsten wire. The method includes the following steps: Step S1: Cutting ultra-high purity tungsten rods with a diameter of 19-21 mm from an ultra-high purity tungsten plate; Step S2: Performing high-temperature heat treatment on the ultra-high purity tungsten rods from Step S1, followed by continuous heating-rotary forging, and repeating the heating-rotary forging process to obtain pretreated ultra-high purity tungsten rods; Step S3: Sequentially subjecting the pretreated ultra-high purity tungsten rods from Step S2 to a process of attaching graphite emulsion, heating, and drawing to obtain black tungsten wire, repeating the graphite emulsion, heating, and drawing process, followed by electrolytic polishing to obtain ultra-high purity tungsten wire. This application uses a 7N-grade ultra-high purity tungsten plate prepared by chemical vapor deposition (CVD) to prepare high-purity tungsten wire. The ultra-high purity tungsten rods are first subjected to high-temperature heat treatment, followed by continuous heating-rotary forging, and then finely drawn. The drawing method of this application ensures the purity and excellent performance of the tungsten wire.

Description

Technical Field

[0001] This application relates to the field of high-purity semiconductor materials, specifically to a method for preparing ultra-high-purity tungsten wire. Background Technology

[0002] In cutting-edge semiconductor technology, particularly in the crucial process of ion implantation, the purity of components used is paramount. Even minute amounts of impurities can profoundly impact the performance of the final product. High-purity tungsten filaments, as a core component of ion implantation equipment, are subject to stringent purity monitoring and control. The importance of high-purity tungsten filaments lies in their ability to operate stably under extreme conditions such as high temperature and high vacuum, providing a stable and efficient light source for ion implantation. However, even minute amounts of impurity elements, such as molybdenum, can severely affect the precision and efficiency of ion implantation, thereby impacting the performance of semiconductor devices. Therefore, the preparation of high-purity tungsten filaments requires not only high tungsten content but also extremely low levels of impurity elements. However, in nature, tungsten and molybdenum are common associated minerals, and their presence in ores makes complete separation during extraction and preparation extremely difficult. While existing powder metallurgy methods for tungsten production have made significant progress in tungsten extraction and purification, they still struggle to completely remove impurity elements such as molybdenum.

[0003] Chemical vapor deposition (CVD) has attracted significant attention due to its unique advantages. By precisely controlling reaction conditions and selecting appropriate reactants, CVD can produce tungsten materials with extremely high purity. This method not only effectively removes impurities such as molybdenum but also ensures that the purity of tungsten meets the standards required in the semiconductor industry. Tungsten materials prepared by CVD not only have high purity but also excellent crystallinity and microstructure. This significantly improves the physical and chemical properties of tungsten materials, meeting the semiconductor industry's demand for high-quality materials. By adjusting reaction conditions such as temperature, pressure, and gas flow rate, the deposition rate, film thickness, and uniformity of tungsten can be precisely controlled. This makes CVD a reliable method for preparing high-quality tungsten materials. However, although tungsten materials prepared by chemical vapor deposition have many advantages, there are differences in the grain structure between high-purity tungsten products prepared by chemical vapor deposition and those prepared by powder metallurgy (PM). CVD high-purity tungsten has a columnar crystal structure, which is coarser than the equiaxed crystal structure of PM tungsten. This makes it very difficult to draw into wires, and the tungsten wire drawing process prepared by powder metallurgy (PM) cannot meet the wire drawing requirements of CVD high-purity tungsten.

[0004] In summary, most current methods for drawing tungsten wires are based on powder metallurgy (PM). However, the purity of the tungsten wires produced does not meet the requirements of ion implantation. There are no records of drawing high-purity tungsten wires prepared by chemical vapor deposition (CVD). Therefore, there is an urgent need to propose a method for preparing ultra-high purity tungsten wires. Summary of the Invention

[0005] In the existing technology, tungsten wires prepared by powder metallurgy (PM) are drawn into wires, but the purity of the tungsten wires prepared does not meet the requirements of ion implantation. However, there is no record of drawing high-purity tungsten wires prepared by chemical vapor deposition (CVD). Therefore, this application proposes a method for preparing ultra-high purity tungsten wires.

[0006] The technical solution of this application is as follows: A method for preparing ultra-high purity tungsten wire includes the following steps: Step S1. Cut ultra-high purity tungsten rods with a diameter of 19~21mm from the ultra-high purity tungsten plate; Step S2. The ultra-high purity tungsten rod from step S1 is first subjected to high-temperature heat treatment, and then subjected to continuous heating-rotation forging, and repeated heating-rotation forging to obtain a pretreated ultra-high purity tungsten rod. Step S3. The pretreated ultra-high purity tungsten rod from step S2 is subjected to a process of attaching graphite emulsion, heating, and drawing to obtain black tungsten wire. The process of attaching graphite emulsion, heating, and drawing is repeated, followed by electrolytic polishing to obtain ultra-high purity tungsten wire.

[0007] Preferably, the ultra-high purity tungsten plate in step S1 is produced based on CVD technology, and its grain structure is columnar crystal structure with a purity of 7N grade. Before use, the ultra-high purity tungsten plate needs to be stress annealed at a temperature of 800~1200℃, a heating rate of 50~100℃ / h, and a holding time of 5~10h, followed by air cooling. The ultra-high purity tungsten rod is cut by wire cutting, and the length of the ultra-high purity tungsten rod is not less than 400mm.

[0008] Preferably, the annealing temperature is 900~1200℃, the heating rate is 60~80℃ / h, and the holding time is 7~10h.

[0009] Preferably, the annealing temperature is 1050~1150℃, the heating rate is 65~75℃ / h, and the holding time is 9~10h.

[0010] Preferably, the high-temperature heat treatment parameters in step S2 are: current increase rate of 1000~1100A / min, maximum current of 3800A~4200A, holding time of 20~25min, current decrease rate of 700~900A / min, and air cooling for 25~30min.

[0011] Preferably, the high-temperature heat treatment parameters in step S2 are: current increase rate of 1030~1070A / min, maximum current of 4000A~4100A, holding time of 23~25min, and current decrease rate of 750~850A / min.

[0012] Preferably, the high-temperature heat treatment parameters in step S2 are: current increase rate of 1050~1060A / min, maximum current of 4070A~4100A, holding time of 24~25min, and current decrease rate of 800~820A / min.

[0013] Preferably, in step S2, the heating-rotation forging process is divided into three stages: L1, L2, and L3, based on the diameter of the ultra-high purity tungsten rod.

[0014] Preferably, in the L1 stage, the diameter of the ultra-high purity tungsten rod is 13~20mm, the heating temperature is 600~800℃, the heating time is 4~8min, the rotary forging temperature is 550~750℃, the rotary forging forward speed is 3~5m / min, and the tungsten rod rotary forging compression ratio is 10~18%.

[0015] Preferably, in the L1 stage, the heating temperature is 630~750℃, the heating time is 5~8min, the rotary forging temperature is 600~700℃, the rotary forging forward speed is 3.5~4m / min, and the tungsten rod rotary forging compression ratio is 12~16%.

[0016] Preferably, in the L1 stage, the heating temperature is 650~700℃, the heating time is 6~7min, the rotary forging temperature is 630~670℃, the rotary forging forward speed is 3.5~3.8m / min, and the tungsten rod rotary forging compression ratio is 13.5~14.5%.

[0017] Preferably, in the L2 stage, the diameter of the ultra-high purity tungsten rod is 7~13mm, the heating temperature is 500~700℃, the heating time is 3~7min, the rotary forging temperature is 450~650℃, the rotary forging forward speed is 3~5m / min, and the tungsten rod rotary forging compression ratio is 10~18%.

[0018] Preferably, in the L2 stage, the heating temperature is 530~650℃, the heating time is 4~7min, the rotary forging temperature is 500~600℃, the rotary forging forward speed is 3.5~4m / min, and the tungsten rod rotary forging compression ratio is 12~16%.

[0019] Preferably, in the L2 stage, the heating temperature is 550~600℃, the heating time is 5~6min, the rotary forging temperature is 530~570℃, the rotary forging forward speed is 3.5~3.8m / min, and the tungsten rod rotary forging compression ratio is 13.5~14.5%.

[0020] Preferably, in the L3 stage, the diameter of the ultra-high purity tungsten rod is 4~7mm, the heating temperature is 400~600℃, the heating time is 2~6min, the rotary forging temperature is 350~550℃, the rotary forging forward speed is 3~5m / min, and the tungsten rod rotary forging compression ratio is 12~20%.

[0021] Preferably, in the L3 stage, the heating temperature is 430~550℃, the heating time is 3~6min, the rotary forging temperature is 400~500℃, the rotary forging forward speed is 3.5~4m / min, and the tungsten rod rotary forging compression ratio is 15~17%.

[0022] Preferably, in the L3 stage, the heating temperature is 450~500℃, the heating time is 4~5min, the rotary forging temperature is 430~470℃, the rotary forging forward speed is 3.5~3.8m / min, and the tungsten rod rotary forging compression ratio is 15.5~16.5%.

[0023] Preferably, in step S3, the wire drawing process is divided into three stages: P1, P2, and P3, based on the diameter of the high-purity tungsten rod. In stage P1, the diameter of the ultra-high-purity tungsten rod is 2-4 mm, the wire drawing temperature is 420-450℃, and the wire drawing compression ratio is 17-23%. In stage P2, the diameter of the ultra-high-purity tungsten rod is 1-2 mm, the wire drawing temperature is 400-430℃, and the wire drawing compression ratio is 18-24%. In stage P3, the diameter of the ultra-high-purity tungsten rod is 0.5-1 mm, the wire drawing temperature is 380-410℃, and the wire drawing compression ratio is 19-25%.

[0024] Preferably, in step S3, in stage P1, the drawing temperature is 430~440℃ and the drawing compression ratio is 19~21%; in stage P2, the drawing temperature is 410~420℃ and the drawing compression ratio is 20~22%; in stage P3, the drawing temperature is 390~400℃ and the drawing compression ratio is 21~23%.

[0025] Preferably, in step S3, the drawing temperature is 432~435℃ and the drawing compression ratio is 19.5~20.5% in stage P1; the drawing temperature is 412~415℃ and the drawing compression ratio is 20.5~21.5% in stage P2; and the drawing temperature is 392~395℃ and the drawing compression ratio is 21.5~22.5% in stage P3.

[0026] The beneficial effects of this application are: (1) The high-purity tungsten wire preparation method proposed in this application uses 7N-grade ultra-high-purity tungsten plates prepared by chemical vapor deposition (CVD) as raw material. Such high-purity tungsten plates are in high demand in the semiconductor manufacturing field, especially for ion implantation. Compared with traditional tungsten wires, its impurity content is extremely low, which solves the problem of not being able to meet the high-precision production requirements due to excessive impurities. At the same time, it greatly reduces the potential harm of impurities to equipment and improves the overall production efficiency and product quality. (2) In this application, the ultra-high-purity tungsten rod is first subjected to high-temperature heat treatment using continuous heating-rotary forging. The heating-rotary forging is divided into three stages, L1, L2, and L3, according to the diameter of the ultra-high-purity tungsten rod. Each stage has key parameters such as temperature and time set to ensure that the uniformity of the material and the stability of the performance are maintained as the diameter of the tungsten rod gradually decreases, thus obtaining a high-purity tungsten rod. Subsequently, this application performs fine wire drawing on the high-purity tungsten rod. The wire drawing process is divided into three stages, P1, P2, and P3, according to the diameter of the tungsten rod. At each stage, key parameters such as drawing temperature and drawing compression ratio are strictly controlled to ensure that the final tungsten wire has excellent performance. This not only guarantees the purity and uniformity of the tungsten wire but also greatly improves its mechanical properties and stability. Detailed Implementation

[0027] To further illustrate the technical means and effects adopted by this application in order to achieve the intended purpose of the invention, the following detailed description of the specific implementation methods, structures, features and effects of this application, in conjunction with preferred embodiments, is provided below.

[0028] Examples 1-5

[0029] This embodiment provides a method for preparing ultra-high purity tungsten wire. It should be noted that the main difference between Examples 1 to 5 lies in the different process parameters, as shown in Tables 1 to 3, as detailed below: Step S1. The ultra-high purity tungsten plate with columnar crystal structure and a purity of 7N, produced by CVD technology, is stress-annealed in a heat treatment furnace at a temperature of 800~1200℃, a heating rate of 50~100℃ / h, and a holding time of 5~10h. Then, it is air-cooled in the heat treatment furnace. The ultra-high purity tungsten rod is then cut using wire cutting until the surface is smooth and free of protrusions and depressions. The diameter of each ultra-high purity tungsten rod is controlled to be 19~21mm and the length is not less than 400mm.

[0030] By adopting the above annealing treatment, the stress generated inside the tungsten plate during the chemical vapor deposition process can be effectively removed, thereby improving the wire drawing performance of the tungsten rod.

[0031] Step S2. The ultra-high purity tungsten rod from step S1 is first subjected to high-temperature heat treatment using electrofusion. The parameters of electrofusion are: current increase rate of 1000~1100 / min, maximum current of 3800~4000A, holding time of 20~25min, current decrease rate of 700~900A / min, and air cooling with the electrofusion equipment for 25~30min.

[0032] Following continuous heating and rotary forging, the process is divided into three stages (L1, L2, and L3) based on the diameter of the ultra-pure tungsten rod. This heating-rotary forging process is repeated to obtain pretreated ultra-high purity tungsten rods. In stage L1, when the diameter of the ultra-high purity tungsten rod is 13-20 mm, the heating temperature is 600-800℃, the heating time is 4-8 min, the rotary forging temperature is 550-750℃, the rotary forging speed is 3-5 m / min, and the tungsten rod rotary forging compression ratio is 10-18%. In stage L2, when the diameter of the ultra-high purity tungsten rod is 7-13 mm, the heating temperature is 500-700℃, the heating time is 3-7 min, the rotary forging temperature is 450-650℃, the rotary forging speed is 3-5 m / min, and the tungsten rod rotary forging compression ratio is 10-18%. In the L3 stage, when the diameter of the ultra-high purity tungsten rod is 4~7mm, the heating temperature is 400~600℃, the heating time is 2~6min, the rotary forging temperature is 350~550℃, the rotary forging forward speed is 3~5m / min, and the tungsten rod rotary forging compression ratio is 12~20%.

[0033] By employing the above technologies, high-temperature heat treatment is carried out using electrofusion, which can provide temperatures higher than those in conventional heat treatment furnaces through current control. High-temperature heat treatment can further remove internal stress from tungsten rods, enabling them to meet the requirements for rotary forging and wire drawing. In the ultra-pure tungsten rods, a heating-rotary forging process is used. Heating preheats the tungsten rods, improving their rotary forging performance, while rotary forging effectively reduces internal stress and enhances their rotary forging properties.

[0034] Step S3. The pretreated ultra-high purity tungsten rod from step S2 is sequentially subjected to a graphite emulsion attachment, heating, and wire drawing process to obtain black tungsten wire. This process is repeated until the diameter reaches 0.5~2 mm, followed by electrolytic polishing to obtain ultra-high purity tungsten wire. The wire drawing process is divided into three stages based on the diameter of the high-purity tungsten rod: P1, P2, and P3. In stage P1, the ultra-high purity tungsten rod diameter is 2~4 mm, the drawing temperature is 420~450℃, and the drawing compression ratio is 17~23%. In stage P2, the ultra-high purity tungsten rod diameter is 1~2 mm, the drawing temperature is 400~430℃, and the drawing compression ratio is 18~24%. In stage P3, the ultra-high purity tungsten rod diameter is 0.5~1 mm, the drawing temperature is 380~410℃, and the drawing compression ratio is 19~25%.

[0035] Table 1 Annealing parameters Example 1 1100 70 10 Example 2 1000 50 5 Example 3 800 80 7 Example 4 900 90 8 Example 5 1200 1000 9 Table 2 High heat treatment parameters Example 1 1050 4100 810 25 Example 2 1060 4080 820 24 Example 3 1000 3900 700 24.5 Example 4 1100 3800 860 24 Example 5 1080 4200 900 25 Table 3 L1 Stage Processing Parameters Example 1 700 6.5 650 3.7 14 Example 2 680 4 550 3 12 Example 3 600 7 600 4.5 13 Example 4 800 6 700 4 15 Example 5 750 8 750 5 16 Table 4 L2 stage processing parameters Example 1 600 5.5 550 3.7 14 Example 2 500 3 450 3 12 Example 3 550 4 500 3.5 13 Example 4 650 6 550 4 15 Example 5 700 7 650 5 16 Table 5 L3 Stage Processing Parameters Example 1 500 4.5 450 3.7 16 Example 2 400 2 350 3 12 Example 3 450 3 400 3.5 14 Example 4 550 5 500 4 18 Example 5 600 6 550 5 20 Table 6 Processing parameters for stages P1~P3

[0036] Testing revealed that the tungsten wire prepared using the method described in this application has a purity of 7N grade and a diameter of 0.5~1mm. This is because the high-purity tungsten wire preparation method proposed in this application uses 7N grade ultra-high purity tungsten plates prepared by chemical vapor deposition (CVD). Compared to traditional tungsten wires, its impurity content is extremely low, solving the problem of insufficient impurities to meet the requirements of high-precision production. This application first subjects the ultra-high purity tungsten rod to high-temperature heat treatment, followed by continuous heating-rotary forging. The heating-rotary forging process is divided into three stages (L1, L2, L3) based on the diameter of the ultra-high purity tungsten rod. Each stage has set key parameters such as temperature and time to ensure that the uniformity of the material and the stability of its performance are maintained as the diameter of the tungsten rod gradually decreases, resulting in a high-purity tungsten rod. Subsequently, this application performs a fine wire drawing process on the high-purity tungsten rod. The wire drawing process is divided into three stages (P1, P2, P3) based on the diameter of the tungsten rod. In each stage, key parameters such as the wire drawing temperature and wire drawing compression ratio are strictly controlled to ensure that the final tungsten wire has excellent performance. This not only ensures the purity and uniformity of the tungsten wire but also greatly improves its mechanical properties and stability. The above description is merely a preferred embodiment of this application and is not intended to limit the application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit the application. Any person skilled in the art can make some modifications or alterations to the disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for producing an ultra-high purity tungsten wire, characterized by, Includes the following steps: Step S1. Cut ultra-high purity tungsten rods with a diameter of 19~21mm from an ultra-high purity tungsten plate using wire cutting. Step S2. The ultra-high purity tungsten rod from step S1 is first subjected to high-temperature heat treatment, and then subjected to continuous heating-rotation forging, and repeated heating-rotation forging to obtain a pretreated ultra-high purity tungsten rod. Step S3. The pretreated ultra-high purity tungsten rod from step S2 is subjected to a process of attaching graphite emulsion, heating, and drawing to obtain black tungsten wire. The process of attaching graphite emulsion, heating, and drawing is repeated, followed by electrolytic polishing to obtain ultra-high purity tungsten wire. The ultra-high purity tungsten plate in step S1 is produced using CVD technology. Its grain structure is columnar and its purity is 7N grade. Before use, the ultra-high purity tungsten plate needs to be stress annealed at a temperature of 800~1200℃, a heating rate of 50~100℃ / h, and a holding time of 5~10h, followed by air cooling. The length of the ultra-high purity tungsten rod is not less than 400mm.

2. The method of claim 1, wherein the tungsten wire has a purity of 99.9999% or more. In step S2, the ultra-high purity tungsten rod is subjected to high-temperature heat treatment using electrofusion. The high-temperature heat treatment parameters are: current increase rate of 1000~1100A / min, maximum current of 3800A~4200A, holding time of 20~25min, current decrease rate of 700~900A / min, and air cooling for 25~30min.

3. The method of claim 1, wherein the tungsten wire has a purity of 99.9999% or more. In step S2, the heating-rotary forging process is divided into three stages: L1, L2, and L3, based on the diameter of the ultra-high purity tungsten rod.

4. The method of claim 3, wherein the tungsten wire has a purity of 99.9999% or more. In the L1 stage, the diameter of the ultra-high purity tungsten rod is 13~20mm, the heating temperature is 600~800℃, the heating time is 4~8min, the rotary forging temperature is 550~750℃, the rotary forging forward speed is 3~5m / min, and the tungsten rod rotary forging compression ratio is 10~18%.

5. The method for preparing ultra-high purity tungsten wire according to claim 3, characterized in that, In the L2 stage, the diameter of the ultra-high purity tungsten rod is 7~13mm, the heating temperature is 500~700℃, the heating time is 3~7min, the rotary forging temperature is 450~650℃, the rotary forging forward speed is 3~5m / min, and the tungsten rod rotary forging compression ratio is 10~18%.

6. The method for preparing ultra-high purity tungsten wire according to claim 3, characterized in that, In the L3 stage, the diameter of the ultra-high purity tungsten rod is 4~7mm, the heating temperature is 400~600℃, the heating time is 2~6min, the rotary forging temperature is 350~550℃, the rotary forging forward speed is 3~5m / min, and the tungsten rod rotary forging compression ratio is 12~20%.

7. The method for preparing ultra-high purity tungsten wire according to claim 1, characterized in that, In step S3, the wire drawing process is divided into three stages: P1, P2, and P3, based on the diameter of the high-purity tungsten rod. In stage P1, the diameter of the ultra-high-purity tungsten rod is 2-4 mm, the wire drawing temperature is 420-450℃, and the wire drawing compression ratio is 17-23%. In stage P2, the diameter of the ultra-high-purity tungsten rod is 1-2 mm, the wire drawing temperature is 400-430℃, and the wire drawing compression ratio is 18-24%. In stage P3, the diameter of the ultra-high-purity tungsten rod is 0.5-1 mm, the wire drawing temperature is 380-410℃, and the wire drawing compression ratio is 19-25%.

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