Method for removing impurities in tetraalkyl ammonium hydroxide aqueous solution

Abstract

The invention relates to a method for removing metal ion impurities in a tetraalkyl ammonium hydroxide aqueous solution. According to the method, related ion exchange resin is pretreated by electronic-grade sulfuric acid and ultrapure water. According to the method, low-concentration tetraalkyl ammonium hydroxide is used as a raw material, a part of metal in the solution is adsorbed through primary chelating resin, and then the metal in the solution is removed again through secondary compounded mixed bed resin. According to the method, the ion exchange rate is improved mainly by transforming and refining the resin and adjusting the proportion of the compound mixed bed resin, the purification effect of the ion exchange resin on the tetraalkyl ammonium hydroxide solution is optimized, and finally, an electronic-grade product with all metals smaller than or equal to 10 ppb is obtained.

Description

Technical Field

[0001] The present technical solution mainly relates to a method for removing impurities from a tetraalkylammonium hydroxide aqueous solution. Background Art

[0002] Tetraalkylammonium hydroxides (TEAOHs) are key chemical reagents that play a vital role in the semiconductor industry. These compounds are primarily used for cleaning silicon wafers, stripping photoresists, and other critical steps in the semiconductor manufacturing process. As semiconductor device sizes continue to shrink, material purity requirements are increasing. Therefore, high-purity TAMOH is crucial to ensuring the performance and reliability of semiconductor devices.

[0003] However, tetraalkylammonium hydroxide products currently on the market generally suffer from insufficient purity. These products often contain impurities such as metal ions, organic impurities, and other inorganic salts. These impurities can introduce defects during the semiconductor manufacturing process, affecting the performance and quality of the final product. Existing purification technologies, mainly distillation and solvent extraction, can improve the purity of tetraalkylammonium hydroxide to a certain extent, but they also have some shortcomings. For example, the distillation process is energy-intensive and difficult to completely remove low-boiling point impurities, while solvent extraction may introduce new organic solvent impurities. Therefore, developing a purification technology that can effectively improve the purity of tetraalkylammonium hydroxide is of great practical significance to the semiconductor industry. Summary of the Invention

[0004] To address the above problems, the present invention proposes a method for removing metal ion impurities from a tetraalkylammonium hydroxide aqueous solution. The invention mainly improves the removal rate of metal ions in the tetraalkylammonium hydroxide aqueous solution by the ion exchange resin by refining or transforming different cation exchange resins and compounding anion and cation exchange resins in different proportions, thereby improving the purity of the product.

[0005] To achieve the above object of the invention, the present invention is implemented by the following technical solution: a method for removing metal ion impurities in a tetraalkylammonium hydroxide aqueous solution, comprising the following steps: S1: Na-type ion exchange resin transformation: Load the Na-type ion exchange resin into the resin column. Rinse the inlet with ultrapure water for 5-10 Bv. Then, introduce electronic-grade dilute sulfuric acid solution for transformation. Monitor the sodium and other metal ion levels in the outlet solution. When the metal ion levels in the outlet solution are similar to those in the inlet, the resin transformation is complete. Rinse the resin with ultrapure water through the inlet and monitor the conductivity of the outlet until the conductivity of the eluate is ≤ that of the ultrapure water.

[0006] S2: Cation Exchange Resin Refining: H-type cation exchange resin is packed into a resin column. After rinsing the inlet with ultrapure water for 5-10 Bv, the resin is purified by passing it through an electronic-grade dilute sulfuric acid solution to elute any residual metal ions from the resin preparation process. The metal ion content in the solution at the outlet is monitored. When the metal ion level at the outlet is similar to that at the inlet, the resin is fully purified. Ultrapure water is passed through the inlet to rinse the resin, and the conductivity at the outlet is monitored until the conductivity of the eluate is ≤ that of the ultrapure water.

[0007] S3: Cleaning of anion exchange resin: Fill the anion exchange resin into the resin column, flush it with ultrapure water at the liquid inlet, and monitor the conductivity of the eluate at the liquid outlet until it is ≤ the conductivity of ultrapure water.

[0008] S4: The ion exchange resins pretreated in steps S2 and S3 are compounded into a mixed bed resin in a specific ratio, and then loaded into an ion exchange resin column.

[0009] S5: Ultrapure water of a certain temperature is introduced from the liquid outlet to backwash the mixed bed resin column in step S4 until the conductivity of the washing liquid is less than or equal to the conductivity of the ultrapure water.

[0010] S6: The tetraalkylammonium hydroxide aqueous solution with a relatively high concentration is prepared into a tetraalkylammonium hydroxide stock solution with a low concentration using ultrapure water.

[0011] S7: The low-concentration tetraalkylammonium hydroxide stock solution obtained in step S6 is passed through one or more ion exchange resin columns at a certain flow rate using a peristaltic pump to obtain an electronic grade tetraalkylammonium hydroxide aqueous solution with a single metal ion of ≤10 ppb.

[0012] Furthermore, the aspect ratio of the resin column involved in the above steps is 5-8.

[0013] Furthermore, the concentration of the electronic grade dilute sulfuric acid solution in steps S1 and S2 is 5-10%.

[0014] Furthermore, the ion exchange resin in step S1 is a chelating resin of a macroporous styrene-divinylbenzene copolymer with a weakly acidic functional group, preferably any one of D840, D850, D851, D852, and D860.

[0015] Furthermore, the cation exchange resin in step S2 is a gel-type polystyrene divinylbenzene cross-linked resin, preferably any one of HOUP8715, HOUP8720, ZGCNR110, ZGCNR170, and ZGCNR140.

[0016] Furthermore, the anion exchange resin in step S3 is a strongly basic styrene anion exchange resin, preferably any one of SA720N, UPW550B, ZGAER210, ZGAER170, and ZGAER140.

[0017] In the mixed bed resin in step S4, the volume ratio of the anion exchange resin to the cation exchange resin is 0.2-2.

[0018] Furthermore, in the mixed bed resin in step S4, the compounding ratio of the anion exchange resin to the cation exchange resin is preferably 1:5, 1:4, 1:3, 1:2, 1:1 or 2:1.

[0019] Furthermore, the tetraalkylammonium hydroxide in step S6 includes but is not limited to tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc., and the concentration of the stock solution needs to be adjusted to 5-15%.

[0020] Furthermore, the column flow rate in step S7 is 2 to 10 Bv / h.

[0021] The present invention provides a method for removing metal ion impurities in a tetraalkylammonium hydroxide aqueous solution, which has the following beneficial effects: 1. A novel method for purifying tetraalkylammonium hydroxide is provided. The method is simple to operate and readily adaptable to industrial production, resolving the operational complexity of existing methods. The resulting tetraalkylammonium hydroxide aqueous solution contains ≤10 ppb of a single metal ion, more preferably ≤5 ppb of a single metal ion, and even more preferably ≤3 ppb of a single metal ion. The single metal ion is a combination of one or more of Na, Mg, Al, K, Ca, Cr, Fe, Cu, Zn, and Ag.

[0022] 2. The method of the present invention does not require a large amount of solvent and energy, reduces environmental pollution, and solves the problem that the existing method is prone to causing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0024] Example 1 S1: Fill the resin column with D840 ion exchange resin. Rinse the column with ultrapure water for 10 Bv. Then, introduce 10% electronic-grade sulfuric acid solution for transformation. Monitor the sodium and other metal ion levels in the solution at the outlet. When the metal ion levels at the outlet are similar to those at the inlet, the resin transformation is complete. Rinse the resin with ultrapure water at the inlet and monitor the conductivity at the outlet until the conductivity of the eluate is ≤ that of the ultrapure water.

[0025] S2: Pack HOUP8715 ion exchange resin into the resin column. Rinse the column with ultrapure water for 5-10 Bv. Then, purify the column with 10% electronic-grade sulfuric acid to remove any residual metal ions from the resin preparation process. Monitor the metal ion content in the solution at the outlet. When the metal ion level at the outlet is similar to that at the inlet, the resin is fully purified. Rinse the resin with ultrapure water from the inlet and monitor the conductivity at the outlet until the conductivity of the eluate is ≤ that of the ultrapure water.

[0026] S3: Fill the ZGAER210 ion exchange resin into the resin column, flush it with ultrapure water at the liquid inlet, and monitor the conductivity of the eluate at the liquid outlet until it is ≤ the conductivity of ultrapure water.

[0027] S4: The anion and cation exchange resins pretreated in steps S2 and S3 are compounded in a ratio of 1:3 to form a mixed bed resin, which is then loaded into an ion exchange resin column.

[0028] S5: Ultrapure water of a certain temperature is introduced from the liquid outlet to backwash the mixed bed resin column in step S4 until the conductivity of the washing liquid is less than or equal to the conductivity of the ultrapure water.

[0029] S6: The higher concentration of tetraalkylammonium hydroxide aqueous solution is prepared with ultrapure water to obtain a tetraalkylammonium hydroxide stock solution with a concentration of 10%.

[0030] S7: Using a peristaltic pump, the 10% tetraalkylammonium hydroxide stock solution obtained in step S6 is passed through a first-stage D840 ion exchange resin column and then through a second-stage mixed bed resin column at a column flow rate of 5 Bv / h to obtain an electronic grade tetraalkylammonium hydroxide aqueous solution.

[0031] Example 2: The method and steps are the same as those in Example 1, except that the resin model in step S1 is D851.

[0032] Example 3: The method and steps are the same as those in Example 1, except that the resin model in step S1 is D860.

[0033] Example 4: The method and steps are the same as those in Example 1, except that the resin model in step S2 is HOUP8720.

[0034] Example 5: The method and steps are the same as those in Example 1, except that the resin model in step S2 is ZGCNR110.

[0035] Example 6: The method and steps are the same as those in Example 1, except that the resin model in step S2 is ZGCNR170.

[0036] Example 7: The method and steps are the same as those in Example 1, except that the resin model in step S3 is SA720N.

[0037] Example 8: The method and steps are the same as those in Example 1, except that the resin model in step S3 is ZGAER170.

[0038] Example 9: The method and steps are the same as those in Example 1, except that the resin model in step S3 is ZGAER140.

[0039] Example 10: The method and steps are the same as those in Example 6, except that the compounding ratio in step S4 is 1:4.

[0040] Example 11: The method and steps are the same as those in Example 6, except that the compounding ratio in step S4 is 1:1.

[0041] Example 12: The method steps are the same as those in Example 6, except that the compounding ratio in step S4 is 2:1.

[0042] Example 13: The method steps are the same as those in Example 10, except that the column flow rate in step S7 is 2 Bv / h.

[0043] Example 14: The method steps are the same as those in Example 10, except that the column flow rate in step S7 is 10 Bv / h.

[0044] Table 1 shows the concentrations of metal ions in the purified tetraalkylammonium hydroxide aqueous solutions of Examples 1-14.

[0045] Table 1

[0046] The above embodiments are merely preferred technical solutions of the present invention and are not intended to limit the present invention. The embodiments and features in the embodiments of this application may be arbitrarily combined unless they conflict. The scope of protection of the present invention shall be the technical solutions described in the claims, including equivalent alternatives to the technical features of the technical solutions described in the claims. Equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for removing impurities from a tetraalkylammonium hydroxide aqueous solution, characterized in that: The following steps are involved: S1: Resin pretreatment: Na-type ion exchange resin is filled into a resin column, washed with ultrapure water, and then transformed with an electronic grade dilute sulfuric acid solution. After the transformation is completed, the resin is washed with ultrapure water to obtain an H-type ion exchange resin column; S2: Refining of cation exchange resin: H-type cation exchange resin is filled in a resin column, and an electronic grade dilute sulfuric acid solution is introduced for refining, and then ultrapure water is introduced for washing to obtain a refined cation exchange resin; S3: Cleaning of anion exchange resin: filling anion exchange resin into a resin column, and washing with ultrapure water to obtain a refined anion exchange resin; S4: compounding the pretreated ion exchange resins in steps S2 and S3 into a mixed bed resin, then loading it into an ion exchange resin column, and washing it with ultrapure water to obtain a refined mixed bed resin; S5: The tetraalkylammonium hydroxide solution passes through an H-type ion exchange resin column and a mixed bed resin in sequence to obtain a tetraalkylammonium hydroxide aqueous solution free of impurities.

2. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 1, characterized in that: In step S1, the Na-type ion exchange resin macroporous structure of styrene-divinylbenzene copolymer with weakly acidic functional group chelating resin includes any one or more combinations of D840, D850, D851, D852, and D860.

3. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 1, characterized in that: In steps S1 and S2, the mass concentration of the electronic grade dilute sulfuric acid solution is 5-10%, and the temperature in the resin column is 25-40°C.

4. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 1, characterized in that: In step S2, the H-type cation exchange resin is a gel-type polystyrene divinylbenzene cross-linked resin, and the cation exchange resin includes any one or more combinations of HOUP8715, HOUP8720, ZGCNR110, ZGCNR170 or ZGCNR140.

5. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 1, characterized in that: In step S3, the anion exchange resin is a strongly basic styrene-based anion exchange resin, and the anion exchange resin includes any one or more combinations of SA720N, UPW550B, ZGAER210, ZGAER170, and ZGAER140.

6. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 1, characterized in that: In the mixed bed resin in step S4, the volume ratio of anion exchange resin to cation exchange resin is 0.2-2.

7. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 6, characterized in that: The volume ratio of the anion exchange resin to the cation exchange resin is any one of 1:5, 1:4, 1:3, 1:2, 1:1 or 2:

1.

8. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 1, characterized in that: Tetraalkylammonium hydroxide includes tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide, etc. The mass concentration of the tetraalkylammonium hydroxide aqueous solution is 5~15%.

9. The method for removing impurities in a tetraalkylammonium hydroxide aqueous solution according to claim 1, characterized in that: In step S5, the column flow rate is 2 to 10 Bv / h.

10. The tetraalkylammonium hydroxide aqueous solution obtained according to the method according to any one of claims 1 to 9, characterized in that The obtained tetraalkylammonium hydroxide aqueous solution has a single metal ion content of ≤10 ppb, and the single metal ions are Na, Mg, Al, K, Ca, Cr, Fe, Cu, Zn, and Ag.

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