High-purity tin electrolytic refining directional impurity removal process

Abstract

The invention discloses a directional impurity removal process for electrolytic refining of high-purity tin. The directional impurity removal process comprises the following steps: preparing an electrolyte; an anode ingot and a cathode plate are placed in an electrolytic bath containing electrolyte, the distance between the anode ingot and the cathode plate is set, circulating flow and circulating time are set for circulating electrolysis, and high-purity tin is deposited on the cathode plate after multiple times of circulating electrolysis. According to the method, the formula of the electrolyte is adjusted, [BMIM] Cl-AlCl3 and 4-hydroxybenzenesulfonic acid modified by polyethylene glycol-2000 are added into the electrolyte, and after circulating electrolysis, high-purity tin obtained on a negative plate reaches the purity of 6N, so that a foundation is laid for subsequent preparation of high-purity tin with the purity of 7N5; and the content of impurity elements such as Sb, As and Ge which are difficult to remove through high-temperature smelting in the high-purity tin is further reduced.

Description

Technical Field

[0001] This invention belongs to the field of high-purity tin electrolytic purification technology, and more specifically, this invention relates to a high-purity tin electrolytic refining directional impurity removal process. Background Technology

[0002] Photolithography, used for generating and replicating circuit patterns, is the most critical technology in semiconductor manufacturing. Advances in photolithography are a crucial technological precursor to the continuous updates of integrated circuit technology following Moore's Law, and its level of advancement determines the overall level of semiconductor manufacturing technology. Photolithography is integral to the entire semiconductor device and integrated circuit manufacturing process, and the smallest line size in photolithography is a marker of the development level of integrated circuits. my country's semiconductor photolithography mainly faces two major challenges: independent research and development of photolithography machines and the domestic substitution of key basic materials for photolithography technology.

[0003] With the development of photolithography technology, the exposure light source has evolved from 193nm deep ultraviolet (DUV) light to 13.5nm extreme ultraviolet (EUV) light. This significant wavelength difference brings higher resolution and etching precision to EUV lithography machines, giving them a significant advantage in manufacturing chips with smaller linewidths. EUV lithography machines are currently the most advanced lithography machines. Currently, relevant domestic institutions are independently developing EUV lithography machines. The light source is the core component of the EUV lithography machine. Extreme ultraviolet light cannot be obtained through conventional means; currently, it can only be generated by bombarding molten tin with a high-energy laser (carbon dioxide laser). The required tin purity is 99.999995% (7N5), and there are strict requirements for oxygen content.

[0004] To obtain high-purity tin meeting the 7N5 purity requirement, the current process involves electrolytic refining, vacuum medium-frequency melting, zone capacity refining, and low-oxygen forming. The purification results of the initial electrolytic refining stage are crucial for subsequent tin purification processes. For impurities with low high-temperature volatility and partition coefficients close to 1, such as As, Sb, and Ge... Vacuum induction melting and zone melting processes alone cannot achieve effective separation and removal, making it difficult to produce stable 7N5 high-purity tin. Considering the significant difference in electrolytic potential between impurities and tin, electrolysis is used to effectively remove these impurities. Currently, there is no efficient electrolytic technology for removing difficult-to-remove impurities such as As, Sb, and Ge. Electrolyte formulations involve many types of additives in varying amounts, making it difficult to obtain electrolyte formulations that target deep removal of specific impurity elements. Furthermore, the easy oxidation of high-purity tin electrolytes is an industry challenge. Oxidation leads to the inability to continuously operate the electrolysis process and the waste of the electrolyte, resulting in high resource consumption and the generation of large amounts of waste liquid. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these and other advantages according to the present invention, the present invention provides a high-purity tin electrolytic refining and directional impurity removal process, comprising the following steps: Step 1: Prepare the electrolyte; Step 2: Place the anode ingot and cathode plate in the electrolytic cell containing electrolyte, set the distance between the anode ingot and cathode plate, set the circulation flow rate and circulation time for cyclic electrolysis, and after multiple cycles of electrolysis, high-purity tin is deposited on the cathode plate.

[0007] Preferably, in step one, the electrolyte comprises the following raw materials: concentrated H2SO4, 4-hydroxybenzenesulfonic acid, SnSO4, NaCl, hydrazine sulfate, disodium ethylenediaminetetraacetate, gelatin, tartaric acid, and 2-naphthol.

[0008] Preferably, in step one, the electrolyte contains concentrated H2SO4 at a concentration of 20-120 g / L, 4-hydroxybenzenesulfonic acid at a concentration of 60-100 g / L, SnSO4 at a concentration of 40-60 g / L, NaCl at a concentration of 5-15 g / L, hydrazine sulfate at a concentration of 1-5 g / L, disodium ethylenediaminetetraacetate at a concentration of 1-5 g / L, gelatin at a concentration of 0.5-1.5 g / L, tartaric acid at a concentration of 0.1-1 g / L, and 2-naphthol at a concentration of 0.1-0.5 g / L.

[0009] Preferably, the electrolyte further includes [BMIM]Cl-AlCl3 at a concentration of 5-15 g / L, wherein the [BMIM]Cl-AlCl3 is obtained by mixing 1-butyl-3-methylimidazolium chloride ionic liquid and anhydrous aluminum chloride in a molar ratio of 1:1-3.

[0010] Preferably, the 4-hydroxybenzenesulfonic acid is replaced with modified 4-hydroxybenzenesulfonic acid, and the method for preparing the modified 4-hydroxybenzenesulfonic acid includes: S11. Dissolve polyethylene glycol-2000 in dichloromethane to obtain a polyethylene glycol solution. Add thionyl chloride dropwise under ice bath conditions at 4°C. Under nitrogen protection, reflux at 70-80°C for 1-6 hours. Remove excess SOCl2 and dichloromethane by rotary evaporation under vacuum of 0.1 Pa and 40-60°C to obtain chlorinated polyethylene glycol. S12. Dissolve 4-hydroxybenzenesulfonic acid in N,N-dimethylformamide, add chlorinated polyethylene glycol, add K2CO3 as a catalyst, and stir at 500-800 rpm for 6-8 hours at 80-90℃. Cool the reaction solution to room temperature, pour it into ice-cold ether to precipitate, filter, and vacuum dry at 45-60℃ for 12-24 hours to obtain modified 4-hydroxybenzenesulfonic acid.

[0011] Preferably, in step S11, the ratio of polyethylene glycol-2000, dichloromethane, and thionyl chloride is 10~30g:100~500mL:1~15mL.

[0012] Preferably, in S12, the ratio of 4-hydroxybenzenesulfonic acid, N,N-dimethylformamide, chlorinated polyethylene glycol, and K2CO3 is 10~30g:100~500mL:10~15g:1~2g.

[0013] Preferably, in step two, the anode ingot is a tin ingot to be purified, and the cathode plate is one of stainless steel plate, titanium plate, 6N pure tin plate, platinum-plated titanium plate, ruthenium-plated titanium plate, and silver-plated copper plate.

[0014] Preferably, in step two, each electrolytic cell contains 6 anode ingots and 5 cathode plates placed alternately, with the outermost anode ingots of the electrolytic cell and the cathode plates placed between adjacent anode ingots, the distance between the anode ingots and the cathode plates being 45~55mm.

[0015] Preferably, in step two, the electrolysis cycle time is 12-24 hours, the cycle flow rate is 2-4 L / min, and the power controller is set to constant current mode with a current density of 30-35 A / m. 3 The electrolysis temperature is 20~30℃.

[0016] The present invention has at least the following beneficial effects: By adjusting the electrolyte formula, the present invention adds [BMIM]Cl-AlCl3 and 4-hydroxybenzenesulfonic acid modified by polyethylene glycol-2000 to the electrolyte. After cyclic electrolysis, the high-purity tin obtained on the cathode plate not only reaches the purity of 6N, laying the foundation for the subsequent preparation of high-purity tin with a purity of 7N5, but also further reduces the content of impurity elements such as Sb, As and Ge in high-purity tin that are difficult to remove by high-temperature melting.

[0017] In the high-purity tin electrolytic refining and directional impurity removal process disclosed in this invention, [BMIM]Cl-AlCl3 is added to the electrolyte. [BMIM]Cl-AlCl3 not only inhibits electrolyte volatilization, but more importantly, it reacts with Sb during electrolysis. 3+ And As 3+ [AsCl4] is formed. - / [SbCl4] - Complexes, selectively deposited in anode slime, can reduce the amount of Sb migrating to the cathode plate for deposition. 3+ And As 3+ The amount of [AsCl4] - [SbCl4] - The formation of the complex leads to Sb 3+And As 3+ The reduction potential shifts significantly negatively, much lower than that of Sn. 2+ The reduction potential is reduced, thus reducing the deposition of Sb and As elements on the cathode plate, thereby reducing the content of Sb and As elements in the high-purity tin obtained by electrolysis.

[0018] The modified 4-hydroxybenzenesulfonic acid added to the electrolyte, after modification with polyethylene glycol-2000, retains its properties of improving electrolyte dispersibility and promoting Sn... 2+ In addition to its role in uniform migration on the cathode surface and reducing local concentration differences, the modified 4-hydroxybenzenesulfonic acid... With electrolytic oxidation of Ge 4+ The formation of complexes, and the introduction of long chains of polyethylene glycol-2000, form a hydrated coating layer on the unstable complexes, hindering their migration to the cathode and reducing the probability of Ge element electrodeposition on the cathode plate, thereby reducing the Ge element content in the high-purity tin obtained by electrolysis.

[0019] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0020] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0021] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0022] Example 1 A high-purity tin electrolytic refining and directional impurity removal process includes the following steps: Step 1: Mix 7 kg of concentrated H2SO4 with 80 L of water, then add 6 kg of 4-hydroxybenzenesulfonic acid, 4.5 kg of SnSO4, 1 kg of NaCl, 0.2 kg of hydrazine sulfate, 0.2 kg of disodium ethylenediaminetetraacetate, 0.1 kg of gelatin, 0.05 kg of tartaric acid, and 0.02 kg of 2-naphthol in sequence, and make up the volume to 100 L to obtain the electrolyte. Step 2: Pour the prepared electrolyte into the electrolytic cell. Clean six cast 4N tin anode plates with dilute hydrochloric acid and purified water, then cover them with 2000-mesh anode bags. Place the treated cathode plates (titanium plates) and anode plates alternately within the electrolytic cell with a 50mm spacing between them. The outermost layer of the cell is the anode ingot, and the cathode plates are placed between adjacent anode ingots, with a 50mm spacing between the anode ingots and cathode plates. Set the circulation flow rate to 3L / min (using a circulation pump to ensure electrolyte flow within the electrolytic cell) and the circulation time to 24 hours for continuous electrolysis. Set the power controller to constant current mode with a current density of 30A / m. 3 The electrolysis temperature was controlled at 25±5℃, and after 8 days of cyclic electrolysis, high-purity tin was deposited on the cathode plate. After the tin deposited on the cathode plate was peeled off, 2 kg of high-purity tin ingots with a purity of 6N were cast in a vacuum.

[0023] Example 2 A high-purity tin electrolytic refining and directional impurity removal process includes the following steps: Step 1: Mix 7 kg of concentrated H2SO4 with 80 L of water, then add 1 kg of [BMIM]Cl-AlCl3, 6 kg of 4-hydroxybenzenesulfonic acid, 4.5 kg of SnSO4, 1 kg of NaCl, 0.2 kg of hydrazine sulfate, 0.2 kg of disodium ethylenediaminetetraacetate, 0.1 kg of gelatin, 0.05 kg of tartaric acid, and 0.02 kg of 2-naphthol in sequence, and bring the volume to 100 L to obtain the electrolyte; wherein, [BMIM]Cl-AlCl3 is obtained by mixing 1-butyl-3-methylimidazolium chloride ionic liquid and anhydrous aluminum chloride in a 1:1 molar ratio; Step 2: Pour the prepared electrolyte into the electrolytic cell. Clean six cast 4N tin anode plates with dilute hydrochloric acid and purified water, then cover them with 2000-mesh anode bags. Place the treated cathode plates (titanium plates) and anode plates alternately within the electrolytic cell with a 50mm spacing between them. The outermost layer of the cell is the anode ingot, and the cathode plates are placed between adjacent anode ingots, with a 50mm spacing between the anode ingots and cathode plates. Set the circulation flow rate to 3L / min (using a circulation pump to ensure electrolyte flow within the electrolytic cell) and the circulation time to 24 hours for continuous electrolysis. Set the power controller to constant current mode with a current density of 30A / m. 3 The electrolysis temperature was controlled at 25±5℃, and after 8 days of cyclic electrolysis, high-purity tin was deposited on the cathode plate. After the tin deposited on the cathode plate was peeled off, 2 kg of high-purity tin ingots with a purity of 6N were cast in a vacuum.

[0024] Example 3 A high-purity tin electrolytic refining and directional impurity removal process includes the following steps: Step 1: Mix 7 kg of concentrated H₂SO₄ with 80 L of water, then add 6 kg of modified 4-hydroxybenzenesulfonic acid, 4.5 kg of SnSO₄, 1 kg of NaCl, 0.2 kg of hydrazine sulfate, 0.2 kg of disodium ethylenediaminetetraacetate, 0.1 kg of gelatin, 0.05 kg of tartaric acid, and 0.02 kg of 2-naphthol in sequence, and bring the volume to 100 L to obtain the electrolyte; the preparation method of modified 4-hydroxybenzenesulfonic acid includes: S11. Dissolve 20g of polyethylene glycol-2000 in 250mL of dichloromethane to obtain a polyethylene glycol solution. Add 10mL of thionyl chloride dropwise under ice bath conditions at 4℃. Under nitrogen protection, reflux at 80℃ for 1h. Remove excess SOCl2 and dichloromethane by rotary evaporation under vacuum of 0.1Pa and 40℃ to obtain chlorinated polyethylene glycol. S12. Dissolve 30g of 4-hydroxybenzenesulfonic acid in 300mL of N,N-dimethylformamide, add 10g of chlorinated polyethylene glycol, add 1.5g of K2CO3 as a catalyst, and stir at 800rpm for 6h at 90℃. Cool the reaction solution to room temperature, pour it into ice-cold ether to precipitate, filter, and vacuum dry at 60℃ for 12h to obtain modified 4-hydroxybenzenesulfonic acid. Step 2: Pour the prepared electrolyte into the electrolytic cell. Clean six cast 4N tin anode plates with dilute hydrochloric acid and purified water, then cover them with 2000-mesh anode bags. Place the treated cathode plates (titanium plates) and anode plates alternately within the electrolytic cell with a 50mm spacing between them. The outermost layer of the cell is the anode ingot, and the cathode plates are placed between adjacent anode ingots, with a 50mm spacing between the anode ingots and cathode plates. Set the circulation flow rate to 3L / min (using a circulation pump to ensure electrolyte flow within the electrolytic cell) and the circulation time to 24 hours for continuous electrolysis. Set the power controller to constant current mode with a current density of 30A / m. 3 The electrolysis temperature was controlled at 25±5℃, and after 8 days of cyclic electrolysis, high-purity tin was deposited on the cathode plate. After the tin deposited on the cathode plate was peeled off, 2 kg of high-purity tin ingots with a purity of 6N were cast in a vacuum.

[0025] Example 4 A high-purity tin electrolytic refining and directional impurity removal process includes the following steps: Step 1: Mix 7 kg of concentrated H2SO4 with 80 L of water, then add 1 kg of [BMIM]Cl-AlCl3, 6 kg of modified 4-hydroxybenzenesulfonic acid, 4.5 kg of SnSO4, 1 kg of NaCl, 0.2 kg of hydrazine sulfate, 0.2 kg of disodium ethylenediaminetetraacetate, 0.1 kg of gelatin, 0.05 kg of tartaric acid, and 0.02 kg of 2-naphthol in sequence, and bring the volume to 100 L to obtain the electrolyte; wherein, [BMIM]Cl-AlCl3 is obtained by mixing 1-butyl-3-methylimidazolium chloride ionic liquid and anhydrous aluminum chloride in a 1:1 molar ratio; The preparation methods of modified 4-hydroxybenzenesulfonic acid include: S11. Dissolve 20g of polyethylene glycol-2000 in 250mL of dichloromethane to obtain a polyethylene glycol solution. Add 10mL of thionyl chloride dropwise under ice bath conditions at 4℃. Under nitrogen protection, reflux at 80℃ for 1h. Remove excess SOCl2 and dichloromethane by rotary evaporation under vacuum of 0.1Pa and 40℃ to obtain chlorinated polyethylene glycol. S12. Dissolve 30g of 4-hydroxybenzenesulfonic acid in 300mL of N,N-dimethylformamide, add 10g of chlorinated polyethylene glycol, add 1.5g of K2CO3 as a catalyst, and stir at 800rpm for 6h at 90℃. Cool the reaction solution to room temperature, pour it into ice-cold ether to precipitate, filter, and vacuum dry at 60℃ for 12h to obtain modified 4-hydroxybenzenesulfonic acid. Step 2: Pour the prepared electrolyte into the electrolytic cell. Clean six cast 4N tin anode plates with dilute hydrochloric acid and purified water, then cover them with 2000-mesh anode bags. Place the treated cathode plates (titanium plates) and anode plates alternately within the electrolytic cell with a 50mm spacing between them. The outermost layer of the cell is the anode ingot, and the cathode plates are placed between adjacent anode ingots, with a 50mm spacing between the anode ingots and cathode plates. Set the circulation flow rate to 3L / min (using a circulation pump to ensure electrolyte flow within the electrolytic cell) and the circulation time to 24 hours for continuous electrolysis. Set the power controller to constant current mode with a current density of 30A / m. 3 The electrolysis temperature was controlled at 25±5℃, and after 8 days of cyclic electrolysis, high-purity tin was deposited on the cathode plate. After the tin deposited on the cathode plate was peeled off, 2 kg of high-purity tin ingots with a purity of 6N were cast in a vacuum.

[0026] Three rounds of cyclic electrolysis were performed according to the methods of Examples 1-4, with each round lasting 8 days. The content of each element in the high-purity tin ingots obtained from each round of electrolysis in Examples 1-4 was determined using glow discharge mass spectrometry (GDMS). The units are all ppm, and the results are shown in the table below: Table 1. Impurity element content in each sample As can be seen from the table above, high-purity tin with a purity of 6N can be obtained in all examples 1-4. Among them, the high-purity tin obtained by electrolysis in example 4 has the lowest combined content of As, Sb and Ge, indicating that [BMIM]Cl-AlCl3 and 4-hydroxybenzenesulfonic acid modified by polyethylene glycol-2000 play a key role in the separation of As, Sb and Ge impurities from Sn.

[0027] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0028] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A high-purity tin electrolytic refining and directional impurity removal process, characterized in that, Includes the following steps: Step 1: Prepare the electrolyte; Step 2: Place the anode ingot and cathode plate in the electrolytic cell containing electrolyte, set the distance between the anode ingot and cathode plate, set the circulation flow rate and circulation time for cyclic electrolysis, and after multiple cycles of electrolysis, high-purity tin is deposited on the cathode plate.

2. The high-purity tin electrolytic refining and directional impurity removal process as described in claim 1, characterized in that, In step one, the electrolyte includes the following raw materials: Concentrated H2SO4, 4-hydroxybenzenesulfonic acid, SnSO4, NaCl, hydrazine sulfate, disodium ethylenediaminetetraacetate, gelatin, tartaric acid, 2-naphthol.

3. The high-purity tin electrolytic refining and directional impurity removal process as described in claim 2, characterized in that, In step one, the electrolyte contains concentrated H2SO4 at a concentration of 20-120 g / L, 4-hydroxybenzenesulfonic acid at a concentration of 60-100 g / L, SnSO4 at a concentration of 40-60 g / L, NaCl at a concentration of 5-15 g / L, hydrazine sulfate at a concentration of 1-5 g / L, disodium ethylenediaminetetraacetate at a concentration of 1-5 g / L, gelatin at a concentration of 0.5-1.5 g / L, tartaric acid at a concentration of 0.1-1 g / L, and 2-naphthol at a concentration of 0.1-0.5 g / L.

4. The high-purity tin electrolytic refining and directional impurity removal process as described in claim 2, characterized in that, The electrolyte also includes [BMIM]Cl-AlCl3 at a concentration of 5-15 g / L, wherein the [BMIM]Cl-AlCl3 is obtained by mixing 1-butyl-3-methylimidazolium chloride ionic liquid and anhydrous aluminum chloride in a molar ratio of 1:1-3.

5. The high-purity tin electrolytic refining and directional impurity removal process as described in claim 2, characterized in that, The 4-hydroxybenzenesulfonic acid is replaced with modified 4-hydroxybenzenesulfonic acid, and the preparation method of the modified 4-hydroxybenzenesulfonic acid includes: S11. Dissolve polyethylene glycol-2000 in dichloromethane to obtain a polyethylene glycol solution. Add thionyl chloride dropwise under ice bath conditions at 4°C. Under nitrogen protection, reflux at 70-80°C for 1-6 hours. Remove excess SOCl2 and dichloromethane by rotary evaporation under vacuum of 0.1 Pa and 40-60°C to obtain chlorinated polyethylene glycol. S12. Dissolve 4-hydroxybenzenesulfonic acid in N,N-dimethylformamide, add chlorinated polyethylene glycol, add K2CO3 as a catalyst, and stir at 500-800 rpm for 6-8 hours at 80-90℃. Cool the reaction solution to room temperature, pour it into ice-cold ether to precipitate, filter, and vacuum dry at 45-60℃ for 12-24 hours to obtain modified 4-hydroxybenzenesulfonic acid.

6. The high-purity tin electrolytic refining and directional impurity removal process as described in claim 5, characterized in that, In S11, the ratio of polyethylene glycol-2000, dichloromethane, and thionyl chloride is 10~30g:100~500mL:1~15mL.

7. The high-purity tin electrolytic refining and directional impurity removal process as described in claim 5, characterized in that, In S12, the ratio of 4-hydroxybenzenesulfonic acid, N,N-dimethylformamide, chlorinated polyethylene glycol, and K2CO3 is 10~30g:100~500mL:10~15g:1~2g.

8. The high-purity tin electrolytic refining and directional impurity removal process as described in claim 1, characterized in that, In step two, the anode ingot is a tin ingot to be purified, and the cathode plate is one of the following: stainless steel plate, titanium plate, 6N pure tin plate, platinum-plated titanium plate, ruthenium-plated titanium plate, and silver-plated copper plate.

9. The high-purity tin electrolytic refining directional impurity removal process as described in claim 1, characterized in that, In step two, six anode ingots and five cathode plates are alternately placed in each electrolytic cell. The outermost part of the electrolytic cell is the anode ingot, and the cathode plates are placed between adjacent anode ingots. The distance between the anode ingot and the cathode plate is 45~55mm.

10. The high-purity tin electrolytic refining directional impurity removal process as described in claim 1, characterized in that, In step two, the electrolysis cycle time is 12-24 hours, and the cycle flow rate is 2-4 L / min; the power controller is set to constant current mode, and the current density is 30-35 A / min. 3 The electrolysis temperature is 20~30℃.

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