A metal purification apparatus, method and use thereof

Abstract

The application discloses a metal purification device and a method and application thereof, and the method comprises the following steps: S1. performing a chemical vapor deposition reaction on a crude metal and a halogen gas to generate a metal halide; S2. decomposing the metal halide in a deposition chamber or depositing the metal by using a hydrogen reduction method; S3. high-temperature smelting the deposited metal under a plasma gas condition; and S4. discharging by using high-temperature low-pressure heat treatment to obtain a purified metal. The method combines a chemical vapor deposition method and a plasma smelting technology, is simple, does not need multiple purifications, and remarkably improves the defects of great difficulty in metal purification and complex process, and promotes the industrial progress of metal purification.

Description

Technical Field

[0001] This invention relates to the field of metal purification technology, specifically to a metal purification apparatus, method, and application. Background Technology

[0002] With the rapid development of semiconductor technology, the demand for high purity core materials in semiconductor technology has increased dramatically. High-purity (6N, 99.9999%) and ultra-high-purity (7N, 99.99999%) metals used in semiconductor processes are becoming increasingly important in the current development of metal purification, and have become core to certain areas of cutting-edge technology. Metal purification technology has become a major bottleneck restricting the downstream semiconductor industry.

[0003] Currently, the purification process for crude metals often involves multiple steps, both wet and dry, requiring repeated refining to improve purity by several orders of magnitude. Traditional processes have significant limitations, including low sample recovery rates and high risks of metal contamination, hindering the industrial progress of metal purification.

[0004] Therefore, it is necessary to study a metal purification device and method to overcome the shortcomings of existing technologies, such as high difficulty and complex processes in metal purification. Summary of the Invention

[0005] This invention provides a metal purification device and method, overcoming the shortcomings of existing technologies in the preparation of high-purity metals, which are difficult and complex.

[0006] In view of the above, the solution of the present invention is as follows:

[0007] The first objective of this invention is to provide a method for purifying metals, comprising the following steps:

[0008] S1. Crude metal reacts with halogen gas via chemical vapor deposition to generate metal halides;

[0009] S2. Decompose metal halides in a deposition chamber or deposit metals using hydrogen reduction;

[0010] S3. High-temperature melting and deposition of metals under plasma gas conditions;

[0011] S4. Degas the smelted metal to obtain purified metal.

[0012] In one embodiment of the present invention, in step S4, the exhaust gas is subjected to high-temperature and low-pressure heat treatment, with a temperature of 150-1500℃ and a pressure of 10. -4 -10 -1 Pa; processing time is 5-240 min.

[0013] In one embodiment of the present invention, the halogen gas in step S1 has a purity of 5N or higher; the hydrogen gas in step S2 has a purity of 5N or higher; and the plasma gas in step S3 has a gas source purity of 5N or higher.

[0014] In one embodiment of the present invention, the plasma gas contains at least one of Ar, H2, N2, He, CH4, and NH3.

[0015] In one embodiment of the present invention, step S3 is performed under a plasma excitation device, and the conditions include at least one of DC, AC, radio frequency, and high frequency.

[0016] In one embodiment of the present invention, the crude metal has a purity of 2N or higher, and the high-purity metal has a purity of 5N or higher.

[0017] Another object of the present invention is to propose the application of the above-described purification method in the purification of metals, including W, Re, Ta, Mo, Ti, and Nb.

[0018] Another objective of this invention is to provide a metal purification apparatus, comprising a CVD furnace, a plasma melting furnace, and an annealing furnace connected in sequence; the CVD furnace includes a CVD precursor chamber, a CVD reaction chamber, and a CVD deposition chamber, the CVD precursor chamber being provided with a first air inlet; the plasma melting furnace is provided with isolation valves at the connection between the CVD furnace and the annealing furnace, and the plasma melting furnace is provided with a third air inlet; the annealing furnace is provided with a fourth air inlet; the CVD furnace, the plasma melting furnace, and the annealing furnace are each connected to a vacuum system.

[0019] In one embodiment of the present invention, the CVD deposition chamber is provided with a second air inlet.

[0020] In one embodiment of the present invention, the vacuum system is connected to an exhaust gas treatment device.

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

[0022] 1. The metal purification method provided by this invention combines chemical vapor deposition and plasma melting technology. The method is simple, requires no multiple purification processes, and significantly improves the shortcomings of high-purity metal purification, such as high difficulty, low recovery rate, and complex process, thus promoting the industrial process of metal purification.

[0023] 2. The metal purification method provided by the present invention achieves the removal of impurity gases from the metal through high temperature and low pressure heat treatment, and can purify the metal to 5N or higher using 2N crude metal as raw material. Attached Figure Description

[0024] Figure 1 This is a flowchart of the metal purification method described in this invention.

[0025] Figure 2 This is a schematic diagram of the overall metal purification device described in this invention.

[0026] Wherein: 1. First air inlet; 2. CVD precursor chamber; 3. Crude metal; 4. CVD reaction chamber;

[0027] 5. Second air inlet; 6. CVD deposition chamber; 7. First crucible; 8. CVD furnace vacuum valve; 9. Vacuum pipeline; 10. Plasma furnace vacuum valve; 11. Second crucible; 12. Annealing furnace vacuum valve; 13. Third crucible; 14. Plasma transfer positive electrode; 15. Plasma non-transfer positive electrode; 16. Plasma transfer / non-transfer negative electrode; 17. Emitting electrode; 18. Plasma beam; 19. First isolation valve; 20. Second isolation valve; 21. CVD furnace; 22. Plasma melting furnace; 23. Annealing furnace; 24. High vacuum pump; 25. High vacuum pump valve; 26. Low vacuum pump valve; 27. Low vacuum pump; 28. Exhaust gas treatment device; 29. ​​Exhaust gas treatment valve; 30. Fore-stage valve; 31. Third air inlet; 32. Fourth air inlet. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0030] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "joining," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] In one embodiment, a metal purification method follows the procedure described below. Figure 1 As shown, the specific steps include the following:

[0032] S1. Crude metal reacts with halogen gas via chemical vapor deposition to generate metal halides;

[0033] S2. Decompose metal halides in a deposition chamber or deposit metals using hydrogen reduction;

[0034] S3. High-temperature melting and deposition of metals under plasma gas conditions;

[0035] S4. Degas the smelted metal to obtain purified metal.

[0036] In this metal purification method, when the crude metal purity is above 2N, the high-purity metal obtained by the above preparation method has a purity of above 5N. This method combines chemical vapor deposition and plasma melting technology, is simple, requires no multiple purification steps, significantly improves the difficulties and complexities of metal purification, and promotes the industrial progress of metal purification.

[0037] In a preferred embodiment, the halogen gas in step S1 has a purity of 5N or higher; the hydrogen gas in step S2 has a purity of 5N or higher; and the plasma gas in step S3 has a purity of 5N or higher.

[0038] Optionally, the plasma gas may be selected from commonly used plasma surface treatment gases, including but not limited to at least one of Ar, H2, N2, He, CH4, and NH3.

[0039] In a preferred embodiment, step S3 is performed under a plasma excitation device, and the conditions include, but are not limited to, DC, AC, radio frequency, high frequency, etc.

[0040] In a preferred embodiment, in step S4, the exhaust gas undergoes high-temperature, low-pressure heat treatment at a temperature of 150-1500°C and a pressure of 10... -4 -10 -1 Pa; processing time is 5-240 min. The purpose is to remove impurity gases from the high-purity metal. When the purification method combines high-temperature, low-pressure heat treatment, and the initial crude metal purity is above 2N, the resulting metal purity is above 5N.

[0041] The above-described metal purification method can be applied to the preparation of high-purity metals from various types of metals, including but not limited to W, Re, Ta, Mo, Ti, and Nb. Specifically, when the purity of crude metals such as W, Mo, and Ti is above 2N, the resulting metal will have a purity of 6N or higher. The ease of the purification process and the final purity of the purified metal depend on the purity of the crude metal. The purification method proposed in this scheme can achieve higher purity when the crude metal purity is higher.

[0042] The impurities in 2N metals vary depending on the metal type and cannot all be listed. Taking tungsten (W) as an example: the impurities contained in 2N tungsten are shown in Table 1.

[0043] Table 1:

[0044]

[0045] In another embodiment, such as Figure 2 As shown, a metal purification device is proposed, comprising a CVD furnace 21, a plasma melting furnace 22, and an annealing furnace 23 connected in sequence; the CVD furnace 21 includes a CVD precursor chamber 2, a CVD reaction chamber 4, and a CVD deposition chamber 6, and the CVD precursor chamber 2 is provided with a first air inlet 1; the plasma melting furnace 22 is provided with isolation valves at the connection between the CVD furnace 21 and the annealing furnace 23, and the plasma melting furnace 22 is provided with a fourth air inlet 32; the annealing furnace 23 is provided with a third air inlet 31; the CVD furnace 21, the plasma melting furnace 22, and the annealing furnace 23 are respectively connected to a vacuum system.

[0046] The plasma melting furnace 22 is a common plasma arc melting furnace. Its melting chamber is connected to the CVD furnace 21 on the left and the annealing furnace 23 on the right. A first isolation valve 19 is provided on the left and a second isolation valve 20 is provided on the right. When open, they connect to facilitate the movement of metal materials, and when closed, they form an isolated melting chamber. An emission electrode 17 is inserted into the upper part of the plasma melting furnace 22, and a plasma transfer / non-transfer negative electrode 16 is provided. A plasma non-transfer positive electrode 15 is provided in the middle, and a plasma transfer positive electrode 14 is provided at the bottom. When the corresponding positive and negative electrodes are connected and energized, a plasma beam 18 is formed in the plasma melting furnace 22, extending from the emission electrode 17 to the bottom.

[0047] The vacuum system described above is designed to ensure the formation of high or low vacuum within the CVD furnace 21, plasma melting furnace 22, and annealing furnace 23. Specifically, the vacuum system includes a high vacuum pump 24 and a low vacuum pump 27. The two vacuum pumps share a vacuum pipeline 9 connecting the bottom of the CVD deposition chamber 6, the plasma melting furnace 22, and the annealing furnace 23. As a common design, valves are installed at the connections between the vacuum pipeline 9 and the CVD deposition chamber 6, the plasma melting furnace 22, and the annealing furnace 23, corresponding to the CVD furnace vacuum valve 8, the plasma furnace vacuum valve 10, and the annealing furnace vacuum valve 12, respectively. The high vacuum pump 24 and the low vacuum pump 27 are respectively equipped with a high vacuum pump valve 25 and a low vacuum pump valve 26 at the connection points of the vacuum pipeline 9. The low vacuum pump 27 is ultimately connected to the exhaust gas treatment device 28, and an exhaust gas treatment valve 29 is provided between them. The high vacuum pump 24 and the low vacuum pump 27 are also connected by a separate pipeline and are equipped with a pre-valve 30, so that the gas in the high vacuum pump 24 can enter the exhaust gas treatment device 28 through the pipeline of the low vacuum pump 27.

[0048] like Figure 1 As shown, during use, crude metal 3 is placed in the CVD precursor chamber 2, the first crucible 7 is placed at the bottom of the CVD deposition chamber 6, the second crucible 11 is placed in the plasma melting furnace 22, and the third crucible 13 is placed in the annealing furnace 23.

[0049] In another embodiment, in the metal purification device described above, a second air inlet 5 is provided at the upper part of the CVD reaction chamber 4 and the CVD deposition chamber 6, for providing reducing gas into the CVD deposition chamber 6, and performing chemical vapor deposition using the reduction method.

[0050] The following uses 2N crude metal as an example to describe the entire purification process in conjunction with the purification methods and apparatus described above.

[0051] Example 1

[0052] S1: Tungsten powder (W) with a purity of 2N is purified by chemical vapor deposition.

[0053] Specifically, 5N chlorine gas and 2N pure tungsten powder are used as precursors and reacted at a temperature of 450-650℃ to generate tungsten metal halogen compound WCl6, which is then carried to the deposition chamber by the movement of gaseous molecules.

[0054] 2N pure tungsten metal is placed in the CVD pre-cavity 2, and the equipment undergoes a vacuum-exhaust-washing process. The vacuum-exhaust-washing process is as follows: The low-vacuum pump valve 26 and the CVD furnace vacuum valve 8 are opened sequentially to maintain the cavity vacuum below 10 Pa; then the CVD furnace vacuum valve 8 and the low-vacuum pump valve 26 are closed. The forestage valve 30 is opened, the high-vacuum pump 24 is opened, the high-vacuum pump valve 25 is opened, and the CVD furnace vacuum valve 8 is opened to maintain the cavity vacuum at 10 Pa. -3 After 15 minutes, close the high vacuum pump valve 25, close the pre-vacuum valve 30, open the first inlet port 1, and charge with Ar until the pressure rises to 10. 3 After Pa, open the low vacuum pump valve 26.

[0055] Repeat the above steps 2-3 times. Maintain a low vacuum state and carry out the CVD reaction. Introduce chlorine gas into the first inlet 1 to maintain the temperature in the CVD precursor chamber 2 at 500℃. After WCl6 is generated in the CVD reaction chamber 4, it enters the CVD deposition chamber 6.

[0056] Inside the CVD deposition chamber 6, the second air inlet 5 is opened to introduce H2 with a reaction gas purity of 5N. The halogen compounds of tungsten metal are reduced to elemental tungsten under conditions of 650-1050℃ to obtain purified metallic tungsten, which is then deposited in the first crucible 7. The gaseous impurity HCl generated in the reaction enters the low vacuum pump 27 through the vacuum pipeline 9 from the CVD deposition chamber 6 and is discharged into the tail gas treatment device 28 through the tail gas treatment valve 29.

[0057] S2: After deposition is complete, open the second isolation valve 20 and move the first crucible 7 to the position of the second crucible 11. Use plasma melting equipment to purify the CVD-purified tungsten powder. The above-mentioned metallic tungsten is further purified by plasma melting technology.

[0058] The evacuation-exhaust-washing procedure is similar to that in CVD. Specifically, the low vacuum pump valve 26 and the plasma furnace vacuum valve 10 are opened sequentially to maintain the chamber vacuum below 10 Pa. Then, the plasma furnace vacuum valve 10 and the low vacuum pump valve 26 are closed. Next, the forestage valve 30 is opened, the high vacuum pump 24 is opened, the high vacuum pump valve 25 is opened, and the plasma furnace vacuum valve 10 is opened to maintain the chamber vacuum below 10 Pa. -3 After 15 minutes, close the high vacuum pump valve 25, close the pre-vacuum valve 30, and open the fourth inlet 32 ​​to introduce a mixture of 10% H2 (purity 5N) and 90% Ar (purity 5N) reaction gases.

[0059] Steps to turn on the plasma excitation device: Connect the non-transfer positive electrode 15 and the non-transfer negative electrode 16 of the plasma to generate a non-transfer arc at the tip of the emitting electrode 17. After stabilization, connect the transfer positive electrode 14 and the transfer negative electrode 16 of the plasma to excite the transfer arc with the non-transfer arc. After stabilization, turn off the non-transfer positive electrode 15 and the non-transfer negative electrode 16 of the plasma.

[0060] Specifically, the gas composition is a mixture of 10% H2 (purity 5N) and 90% Ar (purity 5N), the plasma excitation power is 3kW, the chamber pressure is 5Pa, and the melting time is 120min.

[0061] After melting in step S2, the purity of the purified tungsten metal was tested and found to be above 5N.

[0062] S3: Shut down the plasma melting device and perform high-temperature exhaust.

[0063] After melting is complete, open the first isolation valve 19 and move the second crucible 11 to the position of the third crucible 13. Perform a evacuation-exhaust-washing process on the annealing furnace 23, opening the third air inlet 31 to introduce protective gas and raise the temperature inside the chamber to 150-350℃; the gas pressure is 10... -3 Pa; processing time: 30 min.

[0064] After smelting in step S3, the purity of the purified tungsten metal was tested and found to be above 6N.

[0065] Example 2

[0066] A method for purifying 2N titanium powder (Ti) is provided. The steps are basically the same as in Example 1, except that in step S1, elemental iodine is reacted with titanium powder at a temperature below 230°C to obtain elemental titanium and iodine through a high-temperature decomposition process at a temperature ranging from 1200 to 1570°C within the CVD deposition chamber 6. Iodine vapor is then introduced into the exhaust gas treatment device 28 via vacuum pipeline 9. Combined with step S2, plasma melting is used to obtain purified metallic titanium with a purity of 5N or higher. After further high-temperature, low-pressure exhaust, the purity of the purified metallic titanium is found to be 6N or higher.

[0067] Example 3

[0068] A method for purifying 2N molybdenum powder (Mo) is provided, with the overall steps being the same as in Example 1. In step S1, the high-temperature chlorination reaction in the CVD reaction chamber 4 is conducted at a temperature within the range of 800-1000℃ to generate molybdenum pentachloride. Then, 5N H2 is introduced into the CVD deposition chamber 6, and the temperature is controlled within the range of 900-1200℃ to reduce it to molybdenum powder. Combined with step S2, plasma melting is used to obtain purified metallic molybdenum with a purity of 5N or higher. After further high-temperature, low-pressure exhaust, the purity of the purified metallic molybdenum is tested to be 6N or higher.

[0069] Comparative Example 1

[0070] A method for purifying 2N tungsten powder is provided. The steps are basically the same as in Example 1, except that step S2, plasma melting, is omitted. After processing in steps S1 and S3, the purity of the tungsten metal is finally measured to be less than 5N.

[0071] Comparative Example 2

[0072] A method for purifying 2N titanium powder is provided. The steps are basically the same as in Example 2, except that step S2, plasma melting, is omitted. After processing in steps S1 and S3, the purity of the final titanium metal is measured to be less than 5N.

[0073] Comparative Example 3

[0074] A method for purifying 2N molybdenum powder is provided. The steps are basically the same as in Example 3, except that step S2, plasma melting, is omitted. After processing in steps S1 and S3, the final purity of the metallic molybdenum is less than 5N.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for purifying metals, characterized in that, Includes the following steps: S1. Crude metal reacts with halogen gas via chemical vapor deposition to generate metal halides; S2. Metal is deposited using hydrogen reduction in a deposition chamber; S3. High-temperature melting and deposition of metals under plasma gas conditions; S4. Degas the smelted metal to obtain purified metal; The metals include W, Re, Ta, Mo, Ti, and Nb; In step S4, the exhaust gas undergoes high-temperature, low-pressure heat treatment at a temperature of 150-1500℃ and a pressure of 10. -4 -10 -1 Pa; processing time is 5-240 min.

2. The purification method according to claim 1, characterized in that, The halogen gas in step S1 has a purity of 5N or higher; the hydrogen gas used in the hydrogen reduction method in step S2 has a purity of 5N or higher; and the plasma gas source in step S3 has a purity of 5N or higher.

3. The purification method according to claim 1, characterized in that, The plasma gas contains at least one of Ar, H2, N2, He, CH4, and NH3.

4. The purification method according to claim 1, characterized in that, Step S3 is performed under a plasma excitation device, and the conditions include at least one of DC, AC, radio frequency, and high frequency.

5. The purification method according to claim 1, characterized in that, The crude metal has a purity of 2N or higher, and the purified metal has a purity of 5N or higher.

6. A metal purification apparatus, comprising performing the purification method according to any one of claims 1-5, characterized in that, The system includes a CVD furnace (21), a plasma melting furnace (22), and an annealing furnace (23) connected in sequence. The CVD furnace (21) includes a CVD precursor chamber (2), a CVD reaction chamber (4), and a CVD deposition chamber (6). The CVD precursor chamber (2) is provided with a first air inlet (1). The plasma melting furnace (22) is provided with isolation valves at the connection between the CVD furnace (21) and the annealing furnace (23). The plasma melting furnace (22) is provided with a fourth air inlet (32). The annealing furnace (23) is provided with a third air inlet (31). The CVD furnace (21), the plasma melting furnace (22), and the annealing furnace (23) are connected to a vacuum system.

7. The apparatus according to claim 6, characterized in that, The CVD deposition chamber (6) is provided with a second air inlet (5).

8. The apparatus according to claim 6, characterized in that, The vacuum system is connected to the exhaust gas treatment device (28).

Images